Handbook of Metal Injection Molding [2 ed.] 9780081021538, 0081021534, 9780081021521, 9780081028094

Citation preview

Handbook of Metal Injection Molding

This page intentionally left blank

Woodhead Publishing Series in Metals and Surface Engineering

Handbook of Metal Injection Molding

Second Edition Edited by

Donald F. Heaney

An imprint of Elsevier

Woodhead Publishing is an imprint of Elsevier The Officers’ Mess Business Centre, Royston Road, Duxford, CB22 4QH, United Kingdom 50 Hampshire Street, 5th Floor, Cambridge, MA 02139, United States The Boulevard, Langford Lane, Kidlington, OX5 1GB, United Kingdom Copyright © 2019 Elsevier Ltd. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Details on how to seek permission, further information about the Publisher’s permissions policies and our arrangements with organizations such as the Copyright Clearance Center and the Copyright Licensing Agency, can be found at our website: www.elsevier.com/permissions. This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein). Notices Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary. Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility. To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein. Library of Congress Cataloging-in-Publication Data A catalog record for this book is available from the Library of Congress British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library ISBN: 978-0-08-102152-1 (print) ISBN: 978-0-08-102809-4 (online) For information on all Woodhead publications visit our website at https://www.elsevier.com/books-and-journals

Publisher: Matthew Deans Acquisition Editor: Christina Gifford Editorial Project Manager: Lindsay Lawrence Production Project Manager: Joy Christel Neumarin Honest Thangiah Cover Designer: Victoria Pearson Typeset by SPi Global, India

Contents

Contributors

1

Metal powder injection molding (MIM): Key trends and markets R.M. German 1.1 Introduction and background 1.2 History of success 1.3 Industry structure 1.4 Statistical highlights 1.5 Industry shifts 1.6 Sales situation 1.7 Market statistics 1.8 Metal PIM market by region 1.9 Metal PIM market by application 1.10 Market opportunities 1.11 Production sophistication 1.12 Conclusion Further reading

Part One 2

3

xiii

Processing

1 1 2 3 4 7 8 10 10 11 12 18 19 20

23

Designing for metal injection molding (MIM) D.F. Heaney 2.1 Introduction 2.2 Available materials and properties 2.3 Dimensional capability 2.4 Surface finish 2.5 Tooling artifacts 2.6 Design considerations Further reading

25

Powders for metal injection molding (MIM) D.F. Heaney 3.1 Introduction 3.2 Ideal MIM powder characteristics 3.3 Characterizing MIM powders

45

25 26 31 31 31 34 43

45 45 49

vi

Contents

3.4 Different MIM powder fabrication techniques 3.5 Different alloying methods References 4

5

6

7

Powder-binder formulation and compound manufacture in metal injection molding (MIM) R.K. Enneti, V.P. Onbattuvelli, O. Gulsoy, K.H. Kate, S.V. Atre 4.1 Introduction: The role of binders 4.2 Binder chemistry and constituents 4.3 Binder and powder properties and their effects on feedstock 4.4 Mixing technologies 4.5 Case studies: Lab scale and commercial formulations References Further reading Tooling for metal injection molding (MIM) G. Schlieper 5.1 Introduction 5.2 General design and function of injection molding machines 5.3 Elements of the tool set 5.4 Tool design options 5.5 Special features and instrumentation 5.6 Supporting software and economic aspects Further reading Molding of components in metal injection molding (MIM) D.F. Heaney, C.D. Greene 6.1 Introduction 6.2 Injection molding equipment 6.3 Auxiliary equipment 6.4 Injection molding process 6.5 Common defects in MIM References Debinding and sintering of metal injection molding (MIM) components S. Banerjee, C.J. Joens 7.1 Introduction 7.2 Primary debinding 7.3 Secondary debinding 7.4 Sintering

51 55 56

57 57 59 62 80 84 86 88 89 89 89 91 93 99 101 102 105 105 105 109 111 123 125

129 129 131 139 142

Contents

8

9

7.5 MIM materials 7.6 Settering 7.7 MIM furnaces 7.8 Furnace profiles 7.9 Summary Acknowledgments References

155 160 162 167 168 170 170

Secondaries for metal injection molding (MIM) P. Vervoort, M. Martens 8.1 Introduction 8.2 Operations to improve dimensional control 8.3 Operations to enhance mechanical properties 8.4 Operations to improve appearance and surface properties 8.5 Operations to reduce tooling cost and enhance applications 8.6 Resume—Outlook References

173

Hot isostatic pressing (HIP) of metal injection molding (MIM) D.F. Heaney, C. Binet 9.1 Introduction 9.2 The HIP process 9.3 Benefits of the HIP process 9.4 Issues with the HIP process 9.5 Example HIP processes conditions 9.6 Conclusion References Further reading

Part Two 10

vii

Quality issues

Characterization of feedstock in metal injection molding (MIM) H. Lobo 10.1 Introduction 10.2 Rheology 10.3 Thermal analysis 10.4 Thermal conductivity 10.5 Pressure-volume-temperature 10.6 Conclusions Acknowledgments References

173 174 179 183 190 191 194

195 195 196 196 199 200 201 201 202

203 205 205 207 210 214 215 216 217 217

viii

11

12

13

14

Contents

Modeling and simulation of metal injection molding (MIM) T.G. Kang, S. Ahn, S.H. Chung, S.T. Chung, Y.S. Kwon, S.J. Park, R.M. German 11.1 Modeling and simulation of the mixing process 11.2 Modeling and simulation of the injection molding process 11.3 Modeling and simulation of the thermal debinding process 11.4 Modeling and simulation of the sintering process 11.5 Conclusion References

219

219 223 235 243 249 250

Common defects in metal injection molding (MIM) K.S. Hwang 12.1 Introduction 12.2 Feedstock 12.3 Molding 12.4 Debinding 12.5 Sintering 12.6 Conclusion References

253

Qualification of metal injection molding (MIM) D.F. Heaney 13.1 Introduction 13.2 The metal injection molding process 13.3 Product qualification method 13.4 MIM prototype methodology 13.5 Process control 13.6 Understanding of control parameters 13.7 Conclusion 13.8 Sources of further information

271

Control of carbon content in metal injection molding Gemma Herranz 14.1 Introduction: Why is carbon control crucial? 14.2 Methods of controlling carbon, binder decomposition mechanisms, and process parameters affecting carbon control 14.3 Materials 14.4 Material properties affected by carbon content Acknowledgments References

281

253 253 255 260 266 268 268

271 271 272 273 274 277 280 280

281

283 298 320 324 324

Contents

ix

Part Three Special Metal Injection Molding Processes 15

16

17

Micro metal injection molding (MicroMIM) V. Piotter 15.1 Introduction 15.2 Potential of PIM for microtechnology 15.3 Micromanufacturing methods for tool making 15.4 PIM of microcomponents 15.5 Multicomponent micro powder injection molding 15.6 Simulation of MicroMIM 15.7 Conclusion and future trends 15.8 Sources of further information and advice References Two-material/two-color powder metal injection molding (2C-PIM) P. Suri 16.1 Introduction 16.2 Injection molding technology 16.3 Debinding and sintering 16.4 2C-PIM products 16.5 Future trends References Powder space holder metal injection molding (PSH-MIM) of microporous metals K. Nishiyabu 17.1 Introduction 17.2 Production methods for porous metals 17.3 Formation of microporous structures by the PSH method 17.4 Control of porous structure with the PSH method 17.5 Liquid infiltration properties of microporous metals produced by the PSH method 17.6 Dimensional accuracy of microporous MIM parts 17.7 Functionally graded structures of microporous metals 17.8 Conclusion Acknowledgments References

Part Four 18

Metal injection molding of specific materials

Metal injection molding (MIM) of stainless steel J.M. Torralba, J. Hidalgo 18.1 Introduction 18.2 Stainless steels in MIM

331 333 333 333 334 339 349 352 354 355 355

361 361 361 363 366 368 369

371 371 372 375 381 387 392 396 404 405 405

407 409 409 411

x

19

Contents

18.3 Applications of MIM stainless steels Acknowledgements References

419 425 425

Metal injection molding (MIM) of titanium and titanium alloys T. Ebel 19.1 Introduction 19.2 Challenges of MIM of titanium 19.3 Basics of processing 19.4 Mechanical properties 19.5 Cost reduction 19.6 Special applications 19.7 Conclusion and future trends 19.8 Sources of further information References Further reading

431 431 432 438 440 446 449 454 455 455 460

20

Metal injection molding (MIM) of thermal management materials in microelectronics 461 J.L. Johnson 20.1 Introduction 461 20.2 Heat dissipation in microelectronics 461 20.3 Copper 465 20.4 Tungsten-copper 475 20.5 Molybdenum-copper 487 20.6 Conclusions 494 References 494

21

Metal injection molding (MIM) of soft magnetic materials H. Miura 21.1 Introduction 21.2 Fe-6.5Si 21.3 Fe-9.5Si-5.5Al 21.4 Fe-50Ni 21.5 Conclusion References

499

Metal injection molding (MIM) of high-speed tool steels N.S. Myers, D.F. Heaney 22.1 Introduction 22.2 Tool steel MIM processing 22.3 Mechanical properties References

525

22

499 500 507 516 523 524

525 526 532 533

Contents

23

24

25

Metal injection molding (MIM) of heavy alloys, refractory metals, and hardmetals J.L. Johnson, D.F. Heaney, N.S. Myers 23.1 Introduction 23.2 Applications 23.3 Feedstock formulation concerns 23.4 Heavy alloys 23.5 Refractory metals 23.6 Hardmetals References Further reading

xi

535 535 536 538 543 552 560 566 573

Metal injection molding (MIM) of nickel-base superalloys K. Horke, A. Meyer, R.F. Singer 24.1 Introduction 24.2 MIM processing of nickel-base superalloys 24.3 Specific nickel-base superalloys produced by MIM 24.4 Mechanical properties 24.5 Potential applications 24.6 Conclusion and future trends References

575

Metal injection molding (MIM) of precious metals J.T. Strauss 25.1 Introduction precious metal MIM: Precious metals and powder metallurgy 25.2 Applications for precious metal MIM 25.3 Incentives for utilizing MIM for jewelry manufacturing 25.4 Alloy systems and powder production 25.5 MIM processing References Further reading

609

Index

575 576 583 589 601 605 605

609 610 611 617 619 621 622 623

This page intentionally left blank

Contributors

S. Ahn Pusan National University, Busan, South Korea S.V. Atre University of Louisville, Louisville, KY, United States S. Banerjee DSH Technologies LLC, Cedar Grove, NJ; Holo Inc., Oakland, CA, United States C. Binet Advanced Powder Products, Inc., Philipsburg, PA, United States S.H. Chung Hyundai Steel Co., Incheon, South Korea S.T. Chung CetaTech Inc., Sacheon, South Korea T. Ebel Helmholtz-Zentrum Geesthacht, Geesthacht, Germany R.K. Enneti Global Tungsten and Powders, Towanda, PA, United States R.M. German San Diego State University, San Diego, CA, United States C.D. Greene Treemen Industries, Inc., Boardman, OH, United States O. Gulsoy Marmara University, Istanbul, Turkey D.F. Heaney Advanced Powder Products, Inc., Philipsburg, PA, United States Gemma Herranz University of Castilla La Mancha, INEI-ETSII, Ciudad Real, Spain J. Hidalgo Delft University of Technology, Delft, The Netherlands K. Horke Joint Institute of Advanced Materials and Processes, Friedrich-Alexander Universit€at Erlangen-N€ urnberg, Germany K.S. Hwang National Taiwan University, Taipei, Taiwan, ROC C.J. Joens Elnik Systems LLC, Cedar Grove, NJ, United States J.L. Johnson Elmet Technologies LLC, Lewiston, ME, United States

xiv

Contributors

T.G. Kang Korea Aerospace University, Goyang, South Korea K.H. Kate University of Louisville, Louisville, KY, United States Y.S. Kwon CetaTech Inc., Sacheon, South Korea H. Lobo DatapointLabs, Ithaca, NY, United States M. Martens Formatec Ceramics, DV Goirle, The Netherlands A. Meyer Joint Institute of Advanced Materials and Processes, Friedrich-Alexander Universit€at Erlangen-N€ urnberg, Germany H. Miura Kyushu University, Fukuoka, Japan N.S. Myers Kennametal, Inc., Pittsburgh, PA, United States K. Nishiyabu Kindai University, Higashi osaka, Japan V.P. Onbattuvelli Intel Corporation, Santa Clara, CA, United States S.J. Park POSTECH, Pohang, South Korea V. Piotter Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany G. Schlieper Gammatec Engineering GmbH, Radevormwald, Germany R.F. Singer Neue Materialien F€ urth GmbH, Germany J.T. Strauss HJE Company, Inc., Queensbury, NY, United States P. Suri Heraeus Materials Technology LLC, Singapore, Singapore J.M. Torralba Institute IMDEA Materials, Universidad Carlos III de Madrid, Madrid, Spain P. Vervoort Eisenmann Thermal Solutions, Bovenden, Germany

Metal powder injection molding (MIM): Key trends and markets

1

R.M. German San Diego State University, San Diego, CA, United States

1.1

Introduction and background

Powder injection molding (PIM) has a main subdivision, metal powder injection molding (MIM), that has penetrated many fields. This chapter captures the status of the MIM field and provides a basis for evaluating different operations, markets, and regions. Like powder metallurgy, MIM relies on shaping metal particles and subsequently sintering those particles. The final product is nearly full density, unlike press-sinter powder metallurgy. Hence, MIM products are competitive with most other metal component fabrication routes, and especially are successful in delivering higher strength compared with die casting, improved tolerances compared with investment or sand casting, and more shape complexity compared with most other forming routes. Injection molding enables shape complexity, high-production quantities, excellent performance, and often is lower in cost with respect to the competition. Its origin traces to first demonstrations in the 1930s. In the metallic variant, most of the growth has been after 1990, when profitable operations began to emerge following several years of incubation. Sintered materials technologies (cemented carbides, refractory ceramics, powder metallurgy, white wares, sintered abrasives, refractory metals, and electronic ceramics) add up to a very large value, with final products reaching $100 billion per year on a global basis. About 25% of that global activity is in North America. The production of metal powders alone in North America is annually valued at $4 billion (including paint pigments, metallic inks, welding electrodes, and other uses, besides sintered bodies). Sintered carbide and metal parts production in North America is valued at near $8 billion, where metal-bonded diamond cutting tools, sintered magnets, and semimetal products contribute significantly to industry heavily focused on automotive and consumer products. The powder metallurgy industry consists of about 4700 production sites around the world involved in variants of powder or component production. Most popular is the press-sinter variant that relies on hard tooling, uniaxial compaction, and hightemperature sintering. Based on tonnage, about 70% of the press-sinter products are for the automotive industry. However, on a value basis, the story is dramatically different; metal cutting and refractory metal industries generate the largest value. Here, the products include tantalum capacitors, tungsten light bulb filaments, tungsten carbide metal cutting inserts, diamond-coated oil and gas well drilling tips, Handbook of Metal Injection Molding. https://doi.org/10.1016/B978-0-08-102152-1.00001-5 Copyright © 2019 Elsevier Ltd. All rights reserved.

2

Handbook of Metal Injection Molding

high-performance tool steels, and molybdenum diode heat sinks. Compared to the other powder technologies, the MIM variant is still relatively new and small, but it is growing at 14% per year. In 2011, MIM products were globally valued at approximately $1 billion. This sales activity is spread over about 300 actors. Thus, the average sales would be just $3 million per year for a MIM firm.

1.2

History of success

PIM followed behind the first developments in plastic injection molding. Early polymers were thermosetting compounds; Bakelite, the first man-made polymer, was invented about 1909. Subsequently, as thermoplastic such as polyethylene and polypropylene emerged, forming machines appeared to facilitate the shaping of these polymers a few years later. The first demonstrations of PIM were nearly coincidental with the emergence of plastic injection molding. Simultaneously in the USA and Germany during the 1930s, this was applied to the production of ceramic spark plug bodies. This was followed by the use of PIM for forming tableware in the early 1960s. Generally, these were components with wide allowed dimensional variation. The MIM variant reached production in the 1970s. The time delay between early demonstration and commercialization was due to a lack of sophistication in the process equipment. The manufacturing infrastructure improved dramatically with the advent of microprocessor-controlled processing equipment, such as molders and sintering furnaces, which enabled repeatable and defect-free cycles with tighter tolerances. About 80% of the PIM production capacity is devoted to metals, recognized as MIM, but this generally does not include other metal molding technologies such as die casting, thixomolding, and rheocasting. The first MIM patent was by Ron Rivers (Rivers), using a cellulose-water-glycerin binder that proved unsuccessful. Subsequent efforts with thermoplastic, wax-based binders did reach production at several sites. Major attention was attracted when MIM won two design awards in 1979. One award was for a screw seal used on a Boeing jetliner. The second award was for a niobium alloy thrust-chamber and injector for a liquid-propellant rocket engine developed under an Air Force contract for Rocketdyne. Several patents emerged, and one of the most useful was issued in 1980 to Ray Wiech. From this beginning, a host of other patents, applications, and firms arose, with special activity in California. By the middle 1980s, the technology landscape showed multiple actors. Many companies set up at this time without a license, simply by hiring former employees from the early firms who brought with them insight into the technology. All of the early binder patents have expired and the wax-polymer system discovered by Ray Wiech remains the mainstay of the industry. Since the mid-1990s, the use of paraffin wax has migrated to variants such as polyethylene glycol to give water solubility to part of the binder system. This has improved the concerns over solvents used to remove the binder from the molded component—simply immerse the shaped component in hot water to dissolve out most of the binder.

Metal powder injection molding (MIM): Key trends and markets

3

Thus, the MIM concept relies on plastic molding technology to shape a powderpolymer feedstock into the desired shape. The shape is oversized to accommodate shrinkage during sintering. After molding, the polymer is removed and the particles densified by high-temperature sintering. The product is a shrunken version of the molded shape, with near full density, and performance attributes that rival handbook values, usually far superior to that encountered in traditional press-sinter powder metallurgy and investment casting. This success is widely employed in small, complex, and high-value components, ranging from automotive fuel injectors to watch cases.

1.3

Industry structure

The MIM industry structure and interactions shows generally that the firms fall into a few key focal points. Everything revolves around the custom fabricators, firms that form components to satisfy the specifications of the user community—the users are generally well-known firms such as in firearms (Glock, Colt, Remington), computers (Hewlett Packard, Dell, Apple, Seagate), cellular telephones (Motorola, Samsung, Apple), hand tools (Sears, Leatherman, Snap-on Tools), industrial components (Swagelok, Pall, LG), and automotive (Mercedes-Benz, Borg-Warner, Honda, BMW, Toyota, Chrysler). The leading conference focused on MIM started in 1990 and continues today, where participants gather to share information on technology advances. At these conferences the actors in the industry generally come from one of the following sectors: l

l

l

l

l

l

ingredient suppliers—polymers, powders, and ingredients for either selfmixing or commercial feedstock production; globally there are approximately 40 firms that provide most of the MIM powders, although about 400 firms supply metal powders of various chemistries, particle sizes, particle shapes, and purities; for example, in titanium about four companies out of 40 suppliers make the powders used for MIM; feedstock production firms—purchase raw ingredients and formulate mixtures for sales to molding firms; globally there are usually about 12 feedstock suppliers; molding firms—both custom and captive molders that total nearly 300 MIM operations; about one-third are captive and make parts for themselves, but many of the captive firms also perform custom fabrication; 83% of all parts production is categorized as custom manufacturing; thermal processing firms—own sintering furnaces and debinding equipment that provide toll services; currently only a half-dozen firms are active in this area and most are associated with furnaces fabricators; a few firms provide toll hot isostatic pressing to force 100% density when required in medical or aerospace fields; designers—largely systems design firms associated with large multinational firms that intersect with the MIM industry; a few independent designers are available to handle ad hoc projects; equipment suppliers—firms that design and fabricate custom furnaces, molders, mixers, debinding systems, robotic systems, and other capital devices such as testing devices; the majority of molding machine sales are from six firms, furnace sales are from eight firms, mixer sales are from four firms, so about 20 firms constitute the key equipment suppliers;

4 l

l

Handbook of Metal Injection Molding

consumables suppliers—supply process atmospheres, chemicals, molds, polishing compounds, machining inserts, packaging materials, heating elements, and sintering substrates; adjuncts—including researchers, instructors, consultants, design advisors, conference organizers, trade association personnel, magazine editors, and patent attorneys.

Component production is the central activity. It is split between internal and external products, referred to as captive and custom molders. Likewise it is supported by two parallel supply routes, depending on the decision to selfmix or to purchase premixed feedstock. An example captive molder would be a firearm company that uses MIM to fabricate some of the safety, trigger, or sight components. On the other hand, custom molders also can make these same components, but just as likely may be involved in several application areas as determined by their customer base. As outsourcing increases for multinational firms, custom fabrication grows. Accordingly, MIM from facilities owned by large firms such as Rocketdyne, IBM, AMP, and GTE as early adopters, shifted to purchasing components from captive molders focused on a variety of application areas. Some of the early captive applications included the following examples: l

l

l

l

l

l

l

l

l

l

l

l

l

dental orthodontic brackets made out of stainless steel or cobalt-chromium alloys; business machine components for postage meters and typewriters; watch components including weights, bezels, cases, bands, and clasps; camera components that included switches and buttons; firearm steel parts such as trigger guards, sights, gun bodies, and safeties; carbide and tool steel cutting tools such as wood router bits, end mills, and metal cutting inserts; electronic packages for electronic systems using glass-metal sealing alloys; personal care items such as hair trimmers using tool steel; medical hand tools for special surgical operations; rocket engines using specialty materials such as niobium; automotive air bag actuator components using hardenable stainless steels; special ammunition that included birdshot, armor piercing and frangible bullets; turbocharger rotors for trucks and automobiles formed from high-temperature stainless steels or nickel superalloys.

Since each of these MIM operations had a single field of focus, little was done to grow that portion of the industry. However, in more recent years growth in MIM has come with the shift to custom molding which services a wide variety of applications. The custom molding firms have joined together in efforts to advance the industry, via collaborative marketing efforts, promotion of material standards, publicity through annual awards, and sharing of business data. Although declining, captive molding still remains an important part of the MIM industry. Although the sales growth varies year to year, in most recent times, the global sales gain has been sustained at 14% per year.

1.4

Statistical highlights

Measures of the MIM growth are possible through several parameters, including the following.

Metal powder injection molding (MIM): Key trends and markets l

l

l

l

l

l

l

l

l

l

l

l

5

Patents: Since the start of MIM the total patent generation is large, exceeding 300 by the year 2000, but in more recent years the rate of patent generation has slowed and there are today about 200 currently active patents. Powder sales: In 2010, more than 8000 tons of metal powder were consumed globally by MIM, with a growth rate in powder tonnage use approaching about 20% per year, but due to price reduction the value increases about 14% per year. Feedstock purchase: The two options of self-mixing or purchasing feedstock seem to be of equal merit. Of the top firms, 71% form their own feedstock, which is almost the same ratio for all companies independent of size, suggesting purchased feedstock is neither an advantage nor disadvantage; however, self-mixing does provide greater manufacturing flexibility. Mixing: For those firms mixing their own feedstock, in 2011, they generate $1.8 million in sales per mixer, but the top 20 firms that mix their own feedstock are at $7 million in sales per mixer per year. Sales per molder: In many countries, especially when an operation is at a high utilization, the molding machine generates at least $1 million in sales per year. Across the industry the mean sales per molder is $536,000, while the leading firms have $1.5 million in sales per molder per year. Sales per furnace: Furnaces come in many different sizes and designs, but across the industry sales average about $1 million per furnace per year; for the top MIM operations (with larger and continuous furnaces) the sales average $3.2 million per furnace per year. Continuous furnaces: In 2011, the installed capacity of high-volume continuous sintering furnaces reached 4500 tons of products per year; these are installed with a breakdown of 38% Asia, 47% Europe, and 15% North America. Captive versus custom production: About a third of the firms are captive, but only 21% of the firms have more than 50% of their sales internally. The best estimate is that 17% of the production value in 2011 is for internal use. Sales per kg: Across the MIM industry the average is about $125 in sales per kg of powder consumed, ranging from highs of $10,000 per kg for jewelry, cutting tips, and precision wire bonding tools to $16 per kg for casting refractories. The largest ceramic application is in aerospace casting cores, and the typical is $1000 per kg. Likewise, for metals, the stainless steel orthodontic bracket contributes nearly $100 million in annual sales at an average near $650 per kg. The low tolerance tungsten cell phone eccentric weights sell for a very low price, in the $60 per kg range. Sales per part: Across the industry, the typical part sale price is between $1 and $2 each, but values range from 5 cent cell phone vibrator weights to $35 solenoid bodies and $400 knee implants. Component size: The most typical MIM part mass is in the 6–10 g range. The mass range is from below 0.02 g to over 300 g, but the mean is under 10 g. The largest MIM parts are heat dissipaters for the control systems in hybrid electric vehicles at 1.3 kg and some aerospace superalloy bodies that have similar mass and dimensions reach 200 mm. A growing aspect of MIM is the microminiature components where features are in the micrometer range and this approached $68 million per year in sales for 2010. Employment: Nearly 8000 people are employed in PIM globally, of which nearly 7000 people are employed in MIM, giving an average of 21 people per operation and a median of just 16 people per MIM facility. The larger firms reach upwards to 300–800 people; the largest ceramic injection molding firm once reached employment near 800 people.

Historically, about 80% of the PIM field is for metallic components, or MIM. In recent times, that has increased to nearly 90% metallic. Of the 366 firms that currently

6

Handbook of Metal Injection Molding

Table 1.1 Summary statistics on PIM Percentage of PIM firms in North America Percentage of PIM firms in Europe Percentage of PIM firms in Asia Percentage of PIM firms in rest of world Largest concentration of firms Percentage of firms primarily captive Largest PIM firms

31 28 37 4 USA, China, Germany, Japan 33 India, USA, Germany, Japan

Table 1.2 Summary of PIM global sales Total PIM sales 2010 Total PIM firms Total PIM employment Typical R&D staff Typical profit as % of sales Sales per full-time employee Sales per molding machine Sales per production furnace Percent of firms self-mixing Total installed number of mixers Total installed number of molding machines Total installed number of furnaces Percent of industry using thermal debinding Percent of industry using solvent debinding Percent of industry using catalytic debinding Percent of industry using other debinding Median part size (g)

$1.1 billion 366 8000 2 11 $126,000 $538,000 $980,000 72 380 1750 850 49 26 14 11 6

practice PIM, the majority is located in Asia. The leading countries in terms of PIM were the USA with 106 operations, China with 69 (although expansion is rapid in China), Germany with 41, Japan with 38, Taiwan with 17, Korea with 14, and Switzerland with 12. The number of operations is not necessarily indicative of financial size, since one of the largest MIM facilities is in India, a country which only has five MIM operations, while the USA has the most firms, but they tend to be smaller. Table 1.1 provides a summary of the PIM activities. The USA and China have the most firms while the largest facility is in India. The PIM field is approximately one-third captive and two-thirds custom production. Example captive operations include ceramic casting core production, orthodontics, surgical tools, medical implants, and firearms. PIM includes metals, ceramics, and carbides. Together these materials amount to sales for 2010 that reached $1.1 billion, with about $1 billion in metal components. Table 1.2 provides a summary on the global sales performance. In 2011, of the 366 firms practicing PIM, some do multiple materials. Across the industry over 80% of

Metal powder injection molding (MIM): Key trends and markets

7

Table 1.3 Typical unit manufacturing cell in metal PIM Mixers Molders Debinding reactors Sintering furnaces Typical number of employees per cell

1 4 2 2 20

Table 1.4 Typical productivity ratios Mean sales per employee Median employees per molding machine Mean employees per molding machine Mean employees per production furnace Median employees per production furnace Mean sales per molding machine Median sales per molding machine Mean sales per furnace Median sales per furnace Mean sales per mixer (if installed) Median sales per mixer (if installed) Median growth percentage in sales

$125,000 5 4.2 9 6.7 $536,000 $400,000 $976,000 $667,000 $1.8 million $1.0 million 11

the firms produce metallic components, 20% practice ceramic PIM, 4% practice cemented carbide injection molding, and less than 1% practice composite production (mostly injection-molded silicon carbide that is infiltrated with aluminum to form Al-SiC). Obviously, about 5% of the firms supply a mixture of material types. A MIM or PIM facility basically requires mixing, molding, debinding, and sintering capabilities. Over the years, a typical ratio of these production devices has emerged. Some of the industry unit manufacturing cell ratios are captured in Table 1.3. Note that each device is an integer (one or two or three mixers) so for the mean the value can be noninteger, but for the median only integer values are allowed. Another metric comes from the productivity, usually measured in terms of sales or per employee. Table 1.4 gives several statistical productivity measures for the global PIM industry. In this table, the employment count is based on full-time equivalent (FTE), since several firms have significant part-time employment. Hence, the typical PIM industry (metals, ceramics, carbides, and composites) seems to be as tabulated.

1.5

Industry shifts

The key trends in MIM on a global basis are evident by comparing year 2000 with year 2010. For many years, the MIM field sustained compound annual sales growth at 22% per year with a 34% per year increase in the number of operations. In recent years, the

8

Handbook of Metal Injection Molding

growth rates have become more modest and have stabilized near 8% per year in North America, but continue at a 30% per year pace in Asia. Globally the overall average is 14% per year for recent years. On the basis of some important statistics, here are the changes from year 2000 to year 2010 for MIM: l

l

l

l

l

number of MIM operations decreased 34%; global sales increased 100%; employment increased 100%; installed molding capacity increased 79%; installed sintering capacity increased 86%.

These statistics indirectly indicate increased concentration of the business into the hands of fewer firms. Although a large number of companies are active in MIM, at any one time some are simply in an evaluation mode, and this was especially true in 2000. These characteristically consist of a small team (two or three people) and one or two molding machines, usually purchased feedstock, and might even rely on toll sintering. After initial exploration, many such efforts are terminated or production is transferred to an outside vendor. This is evident by the decrease in number of MIM firms from 2000 to 2010 while the overall field grew. Today, large actors consist of well over 20 molding machines.

1.6

Sales situation

Sales statistics were first gathered in the middle 1980s. Significant growth has produced industry maturation. The metal PIM process is now accepted by several sophisticated customers, such as Bosh, Siemens, Chrysler, Honeywell, Volkswagen, Mercedes Benz, BMW, Chanel, Apple Computer, Pratt and Whitney, Samsung, Texas Instruments, General Electric, Nokia, Motorola, Rolls Royce, Continental, Stryker, LG, Sony, Philips, Seagate, Toshiba, Ford, General Motors, IBM, Hewlett-Packard, Seiko, Citizen, Swatch, and similar firms. Most of the common engineering materials are available in MIM, but as illustrated in Fig. 1.1, based on sales, stainless steels are dominant. The global material sales (value, not tonnage) are as follows—53% stainless steels, 27% steels, 10% tungsten alloys, 7% iron-nickel alloys (mostly magnetic alloys), 4% titanium alloys, 3% copper, 3% cobalt-chromium, 2% tool steels, 2% nickel alloys (superalloys), and 1% electronic alloys (Kovar and Invar). On a tonnage basis, the stainless steel portion of powder consumption is larger, reaching upwards to 60%–65% of powder consumption, and because of that large consumption the powder price is lower, further fueling the use of stainless steel. Some of the metal powders are much higher priced, such as titanium, so the sales partition based on tonnage versus dollars is skewed due to a wide range in material costs. The metal PIM sales for 2010 were in the neighborhood of $1 billion dollars. Independent reports for 2010 give estimates from $955 to $984 million. Some difficulty exists in gathering accurate information since a majority of the firms are privately held and do not make annual reports. Further, currency exchange rates change over the year

Metal powder injection molding (MIM): Key trends and markets

9

leading to inaccurate estimates. For 2010, the best estimate on PIM sales is $1.1 billion and MIM sales is $955 million. The PIM estimate for 2009 was $920 million, so PIM grew from 2009 to 2010 by almost 20%, largely in MIM, and was ahead of the general economic recovery. Fig. 1.2 plots sales growth globally since first recorded at $9 million for 1986. This plot shows that the ceramic business contracted while MIM expanded, largely due to the aerospace slowdowns.

Fig. 1.1 MIM sales globally by main material category. This plot is based percent of global sales, while other studies report based on tonnage of powder consumed.

Fig. 1.2 Annual sales, in millions of US dollars, for MIM as the lower curve and all of PIM as the upper curve plotted against year.

10

Handbook of Metal Injection Molding

Table 1.5 Summary global MIM statistics 2009 total MIM sales 2010 total MIM sales Typical profit as % of sales % MIM sales from self-mixing Installed number of MIM mixers Installed number of MIM molding machines

1.7

$860 million $955 million 9 63 290 1450

Market statistics

The largest market for MIM has historically been industrial components, including pump housings, solenoids, handles, plumbing fixtures, and fitting. This still amounts to 20% of global sales (more in Japan and less in Europe). This is based on component sales, not number of parts or firms or tons of powder, as is reported in other studies. Automotive components are the second largest market for MIM at 14% of global value (on tonnage basis it is much higher in Europe and lower in North America). Consumer products are the third largest market at 11% of the MIM sales, and these are dominated by Asia (cell phone, consumer, and computer parts). Next are the dental, medical, electronic, and firearm applications, each at 7%–9% of the global MIM product value, with North America being the largest actor. Other contributions come from computers, hand tools, luggage trimmings, cosmetic cases, robots, sporting devices, and watch components. The statistical profile for MIM firms shows that about half of the global actors are tiny, being under $1 million in annual MIM sales; sometimes these are located as pilot efforts in large companies or more commonly reflecting private ownership. Table 1.5 gives an industry summary for MIM. About 32% of the operations have captive products, but only 18% of the industry sales are primarily captive. Following the Prado Principle, in MIM the largest 20% of firms control 80% of sales. Moreover, the top 10% of MIM firms control over 60% of sales, average $25 million per year turnover and run with 20 or more molding machines and an average of 120 employees. The top 10% of the MIM industry average five employees for each molder, nine people per furnace, turnover $1.5 million per molding machine each year, $3.2 million per furnace each year, and 70% self-mix.

1.8

Metal PIM market by region

As shown in Fig. 1.3, the primary sales and growth in MIM is in Asia, but the USA remains one of the largest users and producers of ceramic PIM components. Table 1.6 summarizes the regional statistics for PIM in millions of dollars for 2009, the last year where consolidated data are reported. For reference, North American MIM was $186 million in 2009 out of the $316 million total. Of that $32 million was captive MIM. In North America, captive MIM is frequently used for orthodontic brackets and firearms,

Metal powder injection molding (MIM): Key trends and markets

11

Fig. 1.3 Sales partition based on major geographic region.

Table 1.6 Summary of regional sales for PIM Region

Total PIM ($ million)

North America Europe Asia Rest of world Total

316 293 446 27 1082

but is also used for medical applications. The valuation of those products is difficult, since the distributed cost (when the bracket is sold to the dentist) is probably $100 million, but the trade cost (bulk internal transfer cost) is more modest. For 2009, in Europe, the dominant captive MIM applications were watches and similar decorative components such as specialty luggage fasteners. In 2009, the Swiss watch industry did about $12 billion in watch sales, at an average transaction of $566 per watch. Not all watches use MIM, but those that do have a typical MIM content in the $1–$8 range, so the 21 million watches would fit with the $32 million captive Europe sales. In Asia, the captive MIM is mostly for the “3Cs”—products for computers, cellular telephones, and consumer electronics—at the assembly houses such as Foxconn.

1.9

Metal PIM market by application

In prior reports from some of the trade associations, such as the Metal Powder Injection Molding Association in 2006, the medical component sales constituted 36% of MIM, the automotive component was 14% of sales, and hardware was 20% of sales. In the 2007 survey, the MIM market was partitioned as given in Table 1.7 in terms of percentage of sales in each geographic region. More recently, an expanded set of application groups is used to reflect added efforts in sporting, jewelry, hand tools, aerospace, and such. Further, consumer products were separated from watches since watch production was not growing, but uses for latches, eyeglasses, and luggage clasps was growing. Accordingly, the 2010 industry partitioned by application area

12

Handbook of Metal Injection Molding

Table 1.7 Market partition by region and application in terms of percent of sales for 2007 Application

North America

Europe

Asia

ROW

Automotive Consumer Dental Electronics Firearms Hardware Industrial Medical Military Other

30 0 18 6 6 0 6 34 0 0

28 32 14 0 9 0 3 2 1 9

18 15 0 41 0 1 14 2 2 5

0 0 8 0 66 0 24 1 1 1

ROW, rest of world.

is given in Table 1.8. This is a combination of number of companies and their relative focus, so a firm that does only dental counts as 1, but a firm that does dental and industrial counts as 0.5 for each, and so on. This tabulation shows that industrial components (valves, fittings, connectors) are the broadest market focus, followed by consumer (kitchen tools, toothbrush parts, scissors), and electronic components (heat sinks, hermetic packages, connectors). Automotive and medical are fast-growing areas, especially in North America. When considered in terms of sales value, some of the large markets with fewer actors become evident as tabulated in Table 1.9.

1.10

Market opportunities

Listed below are several often discussed market opportunities and some of the related information on growth aspects relative to MIM and its future. l

l

l

l

Consumer, cell phone, and computer uses continue to grow. A comparison of the 2007 and 2009 partition shows an increased use of MIM in hand-held devices, ranging from cell phones to portable computers. The components are small, complex, and strong, applied to switches, buttons, hinges, latches, and decorative devices. Since most of the assembly is in Asia, parts production has migrated to Asia to keep supply lines short. Firearms went through a rapid escalation after the November 2008 election of Obama to the Presidency in the USA, due to fear of new restrictive gun laws; although that wave passed in North America, the temporary surge offset the economic decline seen in many other fields. Military procurement of firearm components has started to slow. However, smaller firearm manufacturers have started to embrace MIM. Industrial, hand tool, and household applications remain strong and steady, and include valve, plumbing, spraying, wrenches, multitools, pepper grinders, scissors, circular saws, nailing guns, and similar devices. Automotive applications for MIM started to escalate with use in turbochargers, fuel injectors, control components (clock mounts, entry locks, knobs, and levers), and valve lifters.

Metal powder injection molding (MIM): Key trends and markets

13

Table 1.8 Global market attention based on primary marketing focus for MIM firms in 2011

l

Field

Percentage

Aerospace Automotive Casting Cell phone Computer Consumer Cutting Dental Electronic Firearm Hand tool Hardware Household Industrial Jewelry Lighting Medical Military Sporting Telecom Watch Wear

2 7 2 2 3 10 2 4 10 6 2 2 0 23 1 1 8 4 2 1 2 5

This initiated in the USA for Buick and Chrysler applications, but leadership shifted to Japan with Honda and Toyota applications from integrated vendors (Nippon Piston Rings) for turbocharger and valve applications. Subsequently, European MIM shops picked up on the materials and applications opened by higher performance but smaller engines, and this wave has become global. There are many complaints over automotive parts production, but it generates large sales volumes that help to lower all costs and improve the field. All expectations are that MIM will continue to grow in the automotive sector. Medical applications are growing from an early base of endoscopic devices, and will become enormous as MIM becomes widely accepted.

Much of the recent growth has been in minimally invasive surgical tools and robotic devices. Early frustrations were with the time to become qualified and the relatively small production lots on many surgical tools. Now adaptations to the market show that much higher prices allow for profitable MIM production in the smaller lots. For example, with knee implants in the USA, one million replacements are made per year, so that is an attractive opportunity. However, there are left and right knees, and about 12 designs or styles. Thus the fragmentation shows on average 40,000 per year of a design, and since there are three leaders in this market, any one company might only order 12,000 of each part per year. This is a low production volume application for

14

Handbook of Metal Injection Molding

Table 1.9 Percent of global MIM sales for each market segment in 2011 Application field

Percentage

Aerospace Automotive Casting Cell phone Computer Consumer Cutting Dental Electronic Firearm Hand tool Hardware Household Industrial Jewelry Lighting Medical Military Sporting Telecom Watch Wear

0 14 0 4 4 11 0 9 9 7 3 1 0 20 1 0 8 2 2 0 2 0

MIM. However, pricing allows for sales that might reach $4 million per design. So far only a few MIM firms are positioning for the production of implants, while many are seeking orders in surgical hand tools. Minimally invasive surgical tools are a prime opportunity for MIM. Micro-featured devices are frequently shown for new genetic sensors (micro-pillar, micro-texture, and micro-array designs). These will be small devices, potentially used in enormous quantities for rapid blood testing and disease identification. l

l

l

Dental applications in this field long ago matured and today there are several firms involved in orthodontic bracket fabrication. However, new instrument and hand tool designs have opened up special opportunities for micro-featured designs. So MIM is moving from its strong historical position in orthodontic brackets into hand tools and special endodontic surgical devices. Aerospace applications for MIM have been demonstrated for 30 years. A new wave of efforts is now starting, driven by cost concerns and envisioned savings with MIM. About a dozen firms are active in this area. Like medical applications, the production volumes are often small, in the 10,000 per year range, but the unit prices are high. Lighting applications for MIM are limited to refractory metals and ceramics, and the developments in this area are in the hands of the big three—Sylvania, Philips, and General Electric. After much early effort, the MIM viability is in serious doubt due to cost reduction and

Metal powder injection molding (MIM): Key trends and markets

l

l

15

competing light-emitting diode (LED) devices. Mounts for LED devices out of copper by MIM have been displayed, but cost will probably work against MIM. Sporting applications have persisted for 20 years, but it appears the cost points in this field do not match well with MIM and the penetration of MIM remains small. Past successes have included metal supports for football knee braces, dart bodies, golf clubs, and running cleats. Jewelry applications are new to MIM and could potentially grow rapidly as alternative materials (nongold and nonsilver) become accepted. These include titanium, high-polish stainless steel, tantalum, and even bronze.

The upside market size on a few of these is quite large, while others not listed above might grow, but the key actors are in place in Asia and it is doubtful if new entries can play a role. Future opportunities emerging from research and development (R&D) efforts are discussed at the conferences. Some of the leading opportunities include ultra-highthermal conductivity composites (for example copper-diamond) for heat sinks. Demonstrations reaching 580 W/(mK) thermal conductivity have been shown by a Japanese MIM firm for use in supercomputers, high-end servers, phased array radar systems, military electronics, hybrid vehicle control systems, gaming computers, and other applications involving high-performance computing. One such device is pictured in Fig. 1.4. A related area is in vapor chamber designs, typically from copper, where a closed internal chamber of porous metal is used to apply heat pipe technology to a similar problem requiring heat dissipation around electronics. Similarly, another area is LED heat sinks, where copper arrays are used to mount the semiconductor, with reports of 100 g arrays with costs as low as $0.75 per mount; these demonstrations have largely come from Asia.

Fig. 1.4 A copper MIM heat transfer device used for electronic cooling. Photograph courtesy of Lye King Tan.

16

Handbook of Metal Injection Molding

Fig. 1.5 Stainless steel MIM medical implant device. Photograph courtesy of Metal Powder Industries Federation.

Microminiature MIM for medical minimally invasive surgical tools is an area of development, involving very small components for end manipulators, such as cutters, grasps, and drug delivery. Most are made from stainless steel and example components are being sold in the range of $2–$15 each. Fig. 1.5 shows one example used in shoulder repair. Other microminiature MIM applications involve components for cell phones, computers, hand-held electronic devices, and dental hand tools for endodontic use and dental cleaning. Implants such as dental tooth posts, components for ligament alignment, hearing canal (ear) reconstruction, drug delivery, heart valves, artificial knees, shoulders, and hips, are expected to be a billion dollar opportunity, but will require considerable dedication and resources to realize; Stryker and Medtronic have set up internal production, Zimmer and Biomed have elected to work with a few MIM shops, and Accellent has elected to be fully qualified for any applications on a custom basis. Microarray devices with hundreds to thousands of pins, posts, or holes for disposable lab-on-a-chip devices are used in blood testing, assessment of disease, analysis of DNA to predict disease, and protein tests; the biochip market is targeted to reach $3.8 billion in sales by 2013 and considerable research is taking place to support this effort. Hewlett-Packard and Oregon State University have a small MIM facility examining options, but activity is also on-going in Germany, Singapore, and Japan. Titanium biocompatible structures, such as for tissue affixation, implants, surgical tools, tool implants, and even sporting devices represent another development area. About 19 firms have some variant of titanium, but few have focused on medical quality. Porous titanium by MIM offers the possibility of hydroxyapatite (bone) infusion; an example MIM device for tooth implants is shown in Fig. 1.6. A further example is hardware tools from tool steel, such as threading devices for cast iron plumbing or water pipes, hand tools, valves and fittings, handles, forming tools, drills, dies. Also, hermetic packages for microelectronics are being developed

Metal powder injection molding (MIM): Key trends and markets

17

Fig. 1.6 Titanium dental implant formed by MIM with an intentional porous region for bone ingrowth. Photograph courtesy of Eric Baril.

using Kovar to enable glass to metal sealing. Fig. 1.7 shows an example MIM part that is sealed with lead. This design routinely sells for $30 each. Aerospace applications exist for smaller superalloy bodies such as IN 625, 713, 718, 723, or Hastelloy X, where the high detail, good surface finish, and shape complexity offered are financially attractive for military and commercial applications. Polymer Technologies, Maetta Sciences, PCC Advanced Forming, Parmatech,

Fig. 1.7 Hermetic Kovar microelectronic package with attached glass-metal sealed lead wires. Component courtesy of Yimin Li.

18

Handbook of Metal Injection Molding

Fig. 1.8 Sales distribution chart for global MIM firms, showing the mode size is in the range from $1 million to $3 million annual sales and over half the firms are below $1 million in annual sales.

Advanced Materials Technology, Advanced Powder Processing, and a few other firms are positioned for this area. Of that total population of companies, the majority practice MIM. The distribution in annual sales for the 366 PIM firms is given in Fig. 1.8. This plot shows almost half are small, with under $1 million in annual sales. This is a partitioning that is roughly based on a factor of three step size, starting with 100,000 for the smaller firms and increasing to show five PIM firms over $30 million.

1.11

Production sophistication

The statistics show that MIM is at an early stage of sophistication as a net-shaping technology. The North American segment is about 90% fully in compliance with one of the ISO 9000/9001/9002 variants, about 25% incompliance with ISO 14000, but nearly 60% of the companies have no intentions along these lines. Several of the firms are into the automotive standards, but few are certified with AS 9100 B, which is required for aerospace components—Maetta Sciences, Pratt and Whitney, Polymer Technology, and PCC Advanced Forming Technology. Several of the firms are in compliance with the ISO 13485 good manufacturing practices required for medical devices, but only a few are at the standards required for implants. Another view of the sophistication is evident by the sales distribution, where the top 10% of the firms based on annual sales control about 60% of the sales, show higher sales per full-time employee (slightly under $300,000/FTE), per molding machine ($1.5 million), per furnace ($3.2 million), and generally set the benchmark for productivity. On the other hand, 50% of the firms listed in this report have annual sales of $1 million or less, and drag down all of the industry statistics.

Metal powder injection molding (MIM): Key trends and markets

19

The key actors in MIM are small compared with several other metalworking technologies. The sophistication of the PIM industry is graphically given in Fig. 1.9. The stage 0 firms are in an evaluation mode, largely trying to determine if there is a business fit, for example possibly a plastic molder seeking material diversification. The stage 1 operation would have no serious sales, and might be setting up or shutting down or sitting idle with technology. A significant portion of the MIM industry is in this situation. A few will grow to be significant actors. Others have dabbled for many years, but have never found the right combination of customers and technology. There are about 150 firms showing up in MIM that fit this category and they contribute about $42 million in sales (roughly $0.25 million per firm per year). Stage 2 firms are more serious about making a business and generally are operating with several molders and are pushing to grow their business. This group generally is between one and two shifts and consists of slightly over 100 firms doing about $116 million in sales. The stage 3 firms dominate the sales, consisting of slightly more than 100 firms doing just under $700 million in sales ($7 million per firm). These are the captive operations in dental and firearms and the major custom. Most of the stage 2 firms are qualified by ISO audits, but only the larger firms are in compliance with aerospace, automotive, or medical quality standards.

1.12

Conclusion

The PIM field has exhibited enormous growth since the first sales statistics were gathered in 1986, amounting to $9 million globally then. Today, MIM is the dominant form of PIM and has sustained 14% per year growth in recent years. The number of MIM firms has not shown much change in recent times, but the size and sophistication have grown considerably. Various estimates have been offered for how far and how long MIM can sustain the growth. The informed estimates balance cost, capacity, and competitive factors, but generally agree that MIM will double yet again to reach $2 billion in annual sales by 2017. After that, significant Fig. 1.9 A histogram plot showing the relative sophistication of the MIM industry based on operational characteristics, as described in the text.

20

Handbook of Metal Injection Molding

cost reduction will be required. Unfortunately, industry-wide research and innovations seem to be lacking. The R&D personnel, publication rate, patent rate, and other leading indicators warn that MIM reached its peak of innovation in about 2005. Contemporary concepts show that patent activity is generally the best leading indicator of commercial sales and profits; so, on this basis, there are early warnings of MIM reaching the end of its growth. Another symptom of the end of growth comes from the fact that, rather than innovation, most industry R&D efforts have turned to cost reductions, improved quality, improved dimensional control, and improved impurity control. These shorter-term gains will not offset the longer-term needs for new materials, products, and applications as required to sustain MIM toward $2 billion in annual sales.

Further reading Anonymous (2007). China reaches for a vibrant future as MIM takes off. Metal Powder Report, 12–21. November. German, R. M. (2007). Global research and development in powder injection molding. Powder Injection Moulding International, 1(2), 33–36. German, R. M. (2009). Titanium powder injection molding: a review of the current status of materials, processing, properties, and applications. Powder Injection Moulding International, 3(4), 21–37. German, R. M. (2011). Metal injection molding: A comprehensive MIM design guide. Princeton, NJ: Metal Powder Industries Federation. German, R. M., & Johnson, J. L. (2007). Metal powder injection molding of copper and copper alloys for microelectronic heat dissipation. International Journal of Powder Metallurgy, 43(5), 55–63. Itoh, Y., Uematsu, T., Sato, K., Miura, H., & Niinomi, M. (2008). Fabrication of high strength alpha plus beta type titanium alloy compacts by metal injection molding. Journal of the Japan Society of Powder and Powder Metallurgy, 55, 720–724. Johnson, P. K. (1979). Award winning parts demonstrate P/M developments. International Journal of Powder Metallurgy and Powder Technology, 15, 323–329. Kato, Y. (2007). Metal injection molding in Asia: current status and future prospects. Powder Injection Moulding International, 1(1), 22–27. Manison, P. (2007). UK-based producer looks to build on current success for precision ceramic components. Powder Injection Moulding International, 1(1), 45–47. Mills, B. (2007). Flexibility helps MIM producer meet the demands of a broad client base. Powder Injection Moulding International, 1(1), 20–21. Moritz, T., & Lenk, R. (2009). Ceramic injection molding: a review of developments in production technology, materials and applications. Powder Injection Moulding International, 32(3), 23–34. Park, S. J., Ahn, S., Kang, T. G., Chung, S. T., Kwon, Y. S., Chung, S. H., et al. (2010). A review of computer simulations in powder injection molding. International Journal of Powder Metallurgy, 46(3), 37–46. Piotter, V., Hanemann, T., Heldele, R., Mueller, M., Mueller, T., Plewa, K., et al. (2010). Metal and ceramic parts fabricated by microminiature powder injection molding. International Journal of Powder Metallurgy, 46(2), 21–28. Rivers, R.D. (1976). Method of injection molding powder metal parts. US Patent 4,113,480.

Metal powder injection molding (MIM): Key trends and markets

21

Sakon, S., Hamada, T., & Umesaki, N. (2007). Improvement in wear characteristics of electric hair clipper blade using high hardness material. Materials Transactions, 48, 1131–1136. Schlieper, G. (2007). Leading German manufacturer works to develop the market for MIM in the automotive sector. Powder Injection Moulding International, 1(3), 37–41. Schwartzwalder, K. (1949). Injection molding of ceramic materials. Ceramic Bulletin, 28, 459–461. Venvoort, P. (2007). Developments in continuous debinding and sintering solutions for MIM. Powder Injection Moulding International, 1(2), 37–44. Whittaker, D. (2007). Developments in the powder injection molding of titanium. Powder Injection Moulding International, 1, 27–32. Whittaker, D. (2007). Powder injection molding looks to automotive applications for growth and stability. Powder Injection Moulding International, 1(2), 14–22. Wiech, R.E. (1980). Manufacture of parts from particulate material, US Patent 4,197,118. Williams, B. (2007). Powder injection molding in the medical and dental sectors. Powder Injection Moulding International, 1, 12–19. Williams, N. (2007). European MIM pioneer drives the industry forward with quality and customer satisfaction. Powder Injection Moulding International, 1(2), 30–34. Ye, H., Liu, X. Y., & Hong, H. (2008). Fabrication of metal matrix composites by metal injection molding—a review. Journal of Materials Processing Technology, 200, 12–24.

This page intentionally left blank

Part One Processing

This page intentionally left blank

Designing for metal injection molding (MIM)

2

D.F. Heaney Advanced Powder Products, Inc., Philipsburg, PA, United States

2.1

Introduction

Metal injection molding (MIM) is a process by which powder is shaped into complex components using tooling and injection molding machines that are very similar to those used in plastic injection molding. Therefore, the component’s complexity is of the same magnitude as those seen in plastic injection molding. The artifacts associated with the injection molding process (gates, ejector pins, parting line) are also similar to those seen in plastic injection molding and must be accounted for in design. However, since the MIM process requires multiple post-molding debinding and sintering steps, some design considerations such as cross-sectional thickness and geometry features require consideration. As a general rule of thumb, components that are less than approximately 100 g and fit into the palm of your hand could be good candidates for MIM technology. A mean size of 15 g is typical for a MIM component; however, components in the range around 0.030 g are possible. Table 2.1 compares the MIM process with other manufacturing processes. Notice that MIM is limited to smaller part sizes, can provide thinner wall thicknesses, has excellent surface finish, and is suited for high volumes. Table 2.2 reviews the upper and lower specifications of the MIM process. The following are some general design considerations which will be discussed in detail in this chapter. l

l

l

l

l

l

l

l

Avoid components over 12.5 mm (0.5 in.) thick. This is a function of MIM technology and alloy, for example 4140 and alloys that use carbonyl powder can have thicker wall sections than those that use gas-atomized powders that have larger particles. Also modifications to binder systems can be made to allow thicker sections to debind. Avoid components over 100 g in mass; however, 300 g are possible for some technologies. Avoid long pieces without a draft (2 degrees) to allow ejection. Avoid holes smaller than 0.1 mm (0.0039 in.) in diameter. Avoid walls thinner than 0.1 mm (0.0039 in.), although 0.030 mm walls are possible in some cases. Maintain uniform wall thickness; thin, slender sections attached to thick sections should be avoided to enhance flow during molding, to avoid sinks and voids, and to limit distortion during sintering. Core out thick areas to avoid sinks, warpage, and debinding defects. Avoid sharp corners. The desired radius is >0.05 mm (0.002 in.).

Handbook of Metal Injection Molding. https://doi.org/10.1016/B978-0-08-102152-1.00003-9 Copyright © 2019 Elsevier Ltd. All rights reserved.

26

Handbook of Metal Injection Molding

Table 2.1 Comparison of MIM attributes with other fabrication techniques Attribute

MIM

Powder metallurgy

Casting

Machining

Component size (g) Wall thickness range (mm) Percent theoretical density (%) Percent theoretical strength (%) Surface finish (μm) Production volume

0.030–300 0.025a–15

0.1–10,000 2+

1+ 5+

0.1+ 0.1+

95–100

85–90

94–99

100

95–100

75–85

94–97

100

0.3–1 2000+

2 2000+

3 500+

0.4–2 1+

a

Features this small could have distortion.

Table 2.2 Typical attributes produced by the MIM process Attribute

Minimum

Typical

Maximum

Component mass (g) Max. dimension (mm) Min. wall thickness (mm) Tolerance (%) Density (%) Production quantity

0.030 2 (0.08 in.) 0.025 (0.001 in.)a 0.2 93 1000

10–15 25 (1 in.) 5 (0.2 in.) 0.5 98 100,000

300 150 (6 in.) 15 (0.6 in.) 1 100 100,000,000

a

Features this small could have distortion.

l

l

l

l

l

Design with a flat surface to aid in sintering—otherwise custom ceramic setters required. Avoid inside closed cavities—although some technologies such as a chemically or thermally removable polymer core may be used but is not common. Avoid internal undercuts—although a collapsible core or extractible core mentioned earlier could be used but are not common. Design with lettering—raised or recessed. Design with threads—internal and external.

2.2

Available materials and properties

MIM is available in many of the common structural materials for medical, military, hardware, electronic, and aerospace applications. If the powder is available in the appropriate size, 93%). The purpose of the controlled-expansion alloys is to insure good mating and/or sealing with other materials as the materials change temperature. Table 2.7 provides controlled-expansion alloy data for F-15 alloy. F-15 is also known as Kovar™ and consists of 29% nickel, 17% cobalt and the balance iron. F-15 has a coefficient of thermal expansion that matches borosilicate (Pyrex) and alumina ceramics and is primarily used for hermetically sealing applications. Other MIM control expansion alloys such as Alloy 36, Alloy 42, and Alloy 48 exist and are basically iron with the percentage nickel added that matches the alloy number to adjust thermal expansion rate. Alloy 36 has a zero coefficient of thermal expansion until 100°C, Alloy 42 has low expansion until about 300°C and has thermal expansion behavior similar to many soft glasses. Alloy 48 has a thermal expansion behavior which matches soda lead and soda lime glasses.

Designing for metal injection molding (MIM)

29

Implantation of MIM components is a growing market where the primary alloys in use are F-75, MP35N, and titanium-based alloys. Table 2.8 provides MIM biocompatible alloy data for F-75 and MP35N. MIM titanium data exist, but are strongly dependent upon the manufacture of the product. MIM titanium and MIM titanium alloy properties are susceptible to carbon and oxygen impurities, thus, monitoring of these impurities in these alloys is paramount. Table 2.4 Typical MIM structural material properties

Material 316L SS 17-4PH SS 17-4PH SS H900 420 SS 440C SS 310 SS Fe 2200 (2 Ni) 2700 (7.5 Ni) 4605 4605 HT 4140 HT 4340 4340 HT 52,100 HT 8620 9310 S7 HT

Density (g/cm3)

YS (MPa)

UTS (MPa)

Elongation (%)

Unnotched Charpy impact energy (J)

7.8 7.6

180 740

520 900

40 6

190 140

67 HRB 27 HRC

185 190

7.6

1100

1200

4

140

33 HRC

190

7.5 7.6 7.5 7.6 7.6

1200 1600 185 – 125

1370 1250 – – 280

– 1 – 20 35

40 – – – 135

44 HRC 55 HRC – – 45 HRB

190 190 – 190 190

7.6

250

400

12

175

69 HRB

190

7.55 7.55 7.5 7.5 7.5 7.5

210 1480 1200 300 1100 1100

440 1650 1600 750 1200 1500

15 1 5 9 6 2

70 55 75 – – –

62 HRB 48 HRC 46 HRC 95 HRB 40 HRC 62 HRC

200 210 200 – – –

7.5 7.5 7.4

130 350 1550

320 540 1750

25 15 2

– – –

100 HRB 375 HV1 53 HRC

– – –

Macro hardness

Young’s modulus (GPa)

Table 2.5 MIM soft magnetic alloy properties

Material

Density (g/cm3)

YS (MPa)

UTS (MPa)

Elongation (%)

Macro hardness (HRB)

Maximum permeability, μ max

Maximum Hc (A/m)

B1990

2200 Fe–50Ni Fe–3Si Fe–50Co 430L

7.6 7.7 7.6 7.7 7.5

120 165 380 150 230

280 450 535 200 410

35 30 24 1 25

45 50 80 80 65

2300 45,000 8000 5000 1500

120 10 56 120 140

1.45 1.40 1.45 2.00 1.15

30

Handbook of Metal Injection Molding

Table 2.6 Copper property comparison Material Density (g/cm3) Thermal conductivity (W/mK) Net shape capability

Cu MIM Grade 1

Cu MIM Grade 2

Wrought C11000

Cast 81,100

Cast 83,400

8.5 330

8.4 290

8.9 380

8.9 350

8.7 180

Excellent

Excellent

Difficult to machine

Difficult to cast

Easy to cast

Table 2.7 Controlled-expansion alloys Material

Density (g/cm3)

YS (MPa)

UTS (MPa)

Elongation (%)

Hardness (HRB)

CTE (100°C)

CTE (200°C)

CTE (300°C)

F-15

7.8

300

450

24

65

6.6

5.8

5.4

Table 2.8 Bioimplantable alloys

Material

Density (g/cm3)

YS (MPa)

UTS (MPa)

Elongation (%)

Macro hardness (HRC)

Young’s modulus (GPa)

F-75 MP35N

7.8 8.3

520 400

1000 900

40 10

25 8

190 –

Table 2.9 Heavy alloys

Material

ASTMB-777-07

Density (g/cm3)

YS (MPa)

UTS (MPa)

Elongation (%)

Macro hardness (HRC)

90W-7Ni-3Fe 90W-6Ni-4Cu 95W-3.5Ni-1.5Fe 95W-3.5Ni-1.5Cu

Class Class Class Class

17 17 18 18

607 620 620 586

860 758 860 793

14 8 12 7

25 24 27 27

1 1 3 3

The last class of alloys discussed here is the tungsten-based heavy alloys, which are of interest because of their high density. These alloys find application in military, medical, cell phone, inertia balancing, and sporting goods applications. Some specific applications are inertia penetrators, cell phone vibration weights, golfing club weights, medical electrodes, and fishing and hunting weights. Table 2.9 provides tungsten heavy alloy data.

Designing for metal injection molding (MIM)

2.3

31

Dimensional capability

MIM is a very repeatable process with variability in the range 0.2%–0.5%. This dimensional variability is associated with the amount of shrinkage and distortion that the component experiences from the time that it is molded to after it is sintered. Components shrink about 1% during the molding operation and an additional 15%–25% after sintering. Also, the ceramic fixtures that are used for component support during sintering may have variability in them, which results in variability of the components from one fixture to the next. Some extreme cases may have greater variability if the particular feature tends to distort or if the feature lies along a parting line, ejector pin blemish, or a gate blemish. If a dimension of a component needs to have high precision, that feature should be embedded in one piece of steel and not have the negative effect of gates, parting lines, and ejector pins. Also, core pins that form holes may be tunneled into the far half of the tool to prevent the butt shut-off from forming flash that would cause variability in the inner diameter in that region. In general, MIM variability is superior to investment casting and inferior to high-precision machining.

2.4

Surface finish

MIM produces remarkable surface finish. Typically, 0.8 μm (32 μin) Ra is achieved; however, a surface finish as smooth as 0.3–0.5 μm (12–20 μin) Ra is possible. The surface finish is a function of the size and chemistry of powders that are used, the sintering conditions, and on any secondary operations, i.e., bead blasting or tumbling. Sandblast and beadblast tend to increase surface roughness because of pitting, and tumbling tends to decrease surface roughness. Component surface roughness can also be affected by the surface finish on the tooling used to manufacture the components. Electrical discharge machining (EDM) pits can be translated to the finished MIMed component.

2.5

Tooling artifacts

2.5.1 Parting line The parting line is where the two halves of the mold intersect. Typically, this can leave a witness line that is as small as 0.0003 in. to as large as 0.001 in. This is highly dependent on the quality of the tool. An example of a parting line is shown in Fig. 2.1. In extreme cases, flashing can occur along the parting line in worn or poorly manufactured tools. These tools can be adjusted to eliminate this flash by either grinding or adjusting a tooling feature that is holding the tool “open” during the molding operation. If the tool is worn, the parting line must be welded and the cavity remanufactured by processes like EDM, hardmilling, or grinding. The location of parting line is a compromise between maintaining a low tool cost and ensuring that the witness line does not interfere with the functionality or look of the

32

Handbook of Metal Injection Molding

Fig. 2.1 Parting line blemish on a MIM component showing where the two halves of a tool come together.

component. The location of the parting line is initially defined to make the tool as simple as possible. Ideally the parting line is placed so that all features can be handled in either side of the tool without the need for slides. Slides raise the cost of tooling considerably. However, one must also consider that greatest dimensional repeatability is obtained when the feature to be measured is in one piece of steel. Envision parting line flash variability causing variability in the dimension across the component where the parting line is located. Also, the position to which the tool opens and closes is not identically the same with each cycle, owing to the presence of material on the mold face during processing. Although minor, this can result in a minor variability of
0.0003 in. Another consideration about the parting line is related to draft angle. Typically, draft begins at the parting line for long components. This enables the part to be easily removed from the tool. Parting lines are typically along one plane to minimize cost; however, the parting line can be stepped to accommodate features that could not be molded any other way or for components that require certain surfaces to be free of any witness lines for esthetic or functional applications.

2.5.2 Ejector pin marks Ejector pins are required to remove the green component from the tool. A sufficient quantity of these pins is required to ensure that the green component can be removed without distortion or cracking. As a natural consequence, witness marks where these ejector pins were located are evident. Fig. 2.2 shows a typical ejector pin blemish. These witness marks become more evident as the tool ages owing to the wear between the pin and the cavity where the pin resides. The size of the pin should be selected to allow the cavity where the pin fits to be opened to accommodate larger ejector pins as the tool ages. Ejector pins are typically round, since round ejector pins are available in

Designing for metal injection molding (MIM)

33

Fig. 2.2 Typical ejector pin marks shown on a MIM component.

many standard sizes and the ejector pin housing in the cavity block is most easy to EDM. Rectangular ejector bars are sometime used in special cases; however, the radius associated with the corner of the bar causes issues with fit-up and long-term integrity of the steel in thin sections, since these corners can act as stress concentrators for crack initiation in the tool. Ejector pins are located where the greatest ejection force is required, for example near bosses, cored holes, and ribs. The esthetics and functionality of the finished component should also be considered when selecting an ejector pin location.

2.5.3 Gate locations The gate is the location where the MIM feedstock flows into the cavity. As a consequence, a blemish will be present at this location on the finished product. A gate is typically located in the thickest section of the component and situated to ensure that uniform packing pressure is available across the component to prevent distortion during debinding and sintering. Gates are often situated so that the material flowing into the cavity impinges on a pin or another wall to prevent jetting of the molten feedstock across the cavity, which leads to surface flow defects. Other considerations for gate location are placement in nonconspicuous or secondary machining locations. Figs. 2.3–2.6 show different gate configurations. Fig. 2.3 shows a typical tab gate blemish, which is located along a parting line. Fig. 2.4 shows a tab gate blemish that is recessed to prevent any gate vestige from interfering with the functionality of the device operation. Fig. 2.5 shows a tunnel (also known as a subgate) blemish. Fig. 2.6 shows a center gate that is produced by either a three-plate tool or a hot sprue. This type of gating is used to ensure uniform packing density along the length of the component, which is a round nose cup.

34

2.6

Handbook of Metal Injection Molding

Design considerations

2.6.1 Flats for sintering One of the key features that should be considered when designing a MIM component is how the component will be fixtured or set during the sintering operation. The MIM material is prone to distortion during the thermal debinding and sintering operation if insufficient support is provided. To eliminate distortion, a flat is designed on the part for sintering which also allows low-cost standard flat fixturing to be utilized. The fixturing is typically ceramic for most MIM materials and may have holes in it to accommodate bosses that the component may have along the flat surface.

Fig. 2.3 Tab gate blemish along parting line on a MIM component.

Fig. 2.4 Recessed tab gate blemish along parting line.

Designing for metal injection molding (MIM)

35

Fig. 2.5 Tunnel (sub)gate blemish.

Fig. 2.6 Center gate blemish located for uniform packing pressure and concentricity.

In cases where it is not possible to design a flat into the component, a contoured fixture which follows the shape of the component can be used. This ceramic fixture is typically designed for the as-molded green state component size. Some fixturing can have features that accommodate both the green size and the sintered size. In this design, the component shrinks from the green state support into the sintered state support. In general, the greatest amount of support is required in the green state since the softening of

36

Handbook of Metal Injection Molding

the polymer during the thermal debinding operation is the weakest condition of the component during the entire MIM process. Alternatives to contoured ceramic fixturing include the use of “molded-in” supports to the actual component that can be removed using a secondary operation after sintering. Another technique is to use a cut ceramic shim that is cut to the desired height dimension of the sintered component.

2.6.2 Wall thickness Wall thickness should be maintained as uniformly as possible to avoid warping and subsequent dimensional variability of the components during processing. Warpage can be the result of differences in cross-sectional thickness caused by variations in packing pressures during the molding operation, differences in binder removal time during the thermal debinding, and differences in thermal mass during the sintering operation. Other issues associated with large cross-sectional thicknesses are sinks, the potential for voids, and blister defects associated with difficulty in binder removal. Wall thickness >15 mm (0.6 in.) should be avoided and wall thicknesses below 10 mm (0.4 in.) are ideal. On the lower end of the spectrum, some technologies can achieve a wall thickness of 25–50 μm (0.001–0.002 in.). These can be achieved over a short span, but as the span increases the likelihood of success decreases due to inability to fill or due to air entrapment. Additionally, very thin (99

Kl€ oden et al. (2010)

Heat treatment information

Mar-M247 MIM MIM MIM + HIP + SA + AG

MIM + HIP + SA + AG

MIM + HIP + SA + AG

Cast + AG Cast + AG Cast + AG Cast + AG Cast + AG

(1977) (1977) (1977) (1977) (1977)

Udimet 720 MIM + HIP

MIM + HIP

MIM + HIP

PM

SA: 1093°C/2 h

–

649

1131

1434

22.5

100

PM

SA: 1129°C/2 h Stabilization: 760°C/8 h/AC AG: 649°C/24 h/AC SA: 1129°C/2 h Stabilization: 760°C/8 h/AC AG: 649°C/24 h/AC

–

649

1071

1370

21.3

100

–

649

1142

1475

18.1

–

HIP: 1130°C/140 MPa/4 h SA: 1100°C/1 h AG: 650°C/24 h + 760°C/16 h HIP: 1130°C/140 MPa/4 h SA: 1100°C/1 h AG: 650°C/24 h + 760°C/16 h HIP: 1130°C/140 MPa/4 h SA: 1100°C/1 h AG: 650°C/24 h + 760°C/16 h HIP: 1130°C/140 MPa/4 h SA: 1100°C/1 h AG: 650°C/24 h + 760°C/16 h

MIM tensile test piece

20

1127

1534

–

>99

Kl€ oden et al. (2012, 2013)

Machined MIM tensile test piece

650

1026

1373

–

>99

Kl€ oden et al. (2012, 2013)

Machined MIM tensile test piece

800

931

955

–

>99

Kl€ oden et al. (2012, 2013)

Machined MIM tensile test piece

900

592

598

–

>99

Kl€ oden et al. (2012, 2013)

Cast + wrought

Green, Lemsky, and Gasior (1996) Jain, Ewing, and Yin (2000) Jain et al. (2000)

Udimet 720Li MIM + HIP + SA + AG

MIM + HIP + SA + AG

MIM + HIP + SA + AG

MIM + HIP + SA + AG

AC, air cooled; AG, aged; FC, furnace cooled; HIP, hot isostatically pressed; l/d-ratio, length/diameter ratio.; MIM, metal injection molded—as-sintered; OQ, oil quenched; PM, powder metallurgy route: forged HIP compacts; RAC, rapid air cooled; SA, solution annealed; WQ, water quenching. a Relative Density refers to theoretical density (TD).

600

Handbook of Metal Injection Molding

sintered and hot isostatically pressed, sintered and hot isostatically pressed and heattreated). However, it has to be noted that different sample geometries and test speeds have been used. Especially the ductility is affected by the sample geometry and might differ for different test specimen geometries. Moreover, the densities and the impurity contents differ for different alloys and research groups. Also the chemical composition of the alloys might differ slightly. For MIM nickel-base superalloys, the only available material standard is AMS 5917 for MIM IN 718. Thus, there is a lot of work to be done in order to establish similar standards also for other nickel-base superalloys fabricated by MIM.

24.4.2 Fatigue properties For several aerospace applications, high cycle fatigue (HCF), and/or low cycle fatigue (LCF) properties are of main interest. Published information is available mainly for IN 718 and IN 713LC. For heat-treated metal injection molded IN 718, an approx. 30% reduced fatigue endurance limit at 538°C compared to wrought IN 718 material is reported (Miura et al., 2010). The room temperature rotating bending fatigue limit of MIM IN 718 with 98%–99% theoretical density obtained by Ikeda, Osada, Kang, Tsumori, and Miura (2011) was 65% of the fatigue limit of wrought alloy. In both investigations, residual porosity is assumed to reduce the fatigue strength of injection molded material. A research group from IHI Corporation however, reported MIM IN 718 hightemperature fatigue strengths higher than for wrought material (Ikeda, Satoh, Tsuno, Yoshinouchi, & Satake, 2014). In order to simulate the influence of microporosity, an artificial defect of 0.1 mm diameter was introduced in some test samples. The 0.1 mm surface defects did not lead to any drop of the fatigue strength. Valencia et al. (1997) investigated the high cycle fatigue behavior at 650°C of MIM IN 718 material that was hot isostatically pressed (1190°C/104 MPa/4 h) and subsequently heat-treated per AMS 5663. The results obtained at an R ratio of 1 indicated a higher fatigue life for metal injection molded material than the AMS 5596 minimum requirements. A fatigue stress of 448 MPa at 107 cycles was determined which is 37% above the AMS 5596 minimum requirement (327 MPa). Near-wrought LCF capability at room temperature of MIM IN 718 is reported by Ott and Peretti (2012). Another MIM nickel-base superalloy that was investigated with regard to fatigue properties is IN 713LC. Rotating bending fatigue testing of MIM IN 713LC at 500°C reveals significantly better fatigue properties of MIM IN 713LC material compared to cast and hot isostatically pressed IN 713LC alloy (Horke et al., 2016). These examples show that for metal injection molded nickel-base superalloys, fatigue properties sufficient for practical applications can be achieved. The good fatigue properties for MIM nickel-base superalloys can be explained by the fine grained microstructure obtained via MIM. Elimination of γ-γ0 -eutectics and refractory segregation compared to castings may also play a role in certain cases.

Metal injection molding (MIM) of nickel-base superalloys

601

24.4.3 Creep properties For high-temperature applications, creep deformation has to be considered and is thus of interest for material selection. Information on creep performance of metal injection molded nickel-base superalloys is mainly available for IN 718, IN 713LC, CM 247 LC, and Udimet 700. For metal injection, molded Udimet 700 creep strength comparable to cast material is reported (Diehl & St€ over, 1990). Valencia et al. (1997) investigated the stress rupture properties of metal injection molded IN 718. It was shown that powder injection molded, hot isostatically pressed and δ-phase optimized heat-treated (870°C/10 h + heat treatment per AMS 5663 specification) material meets AMS 5596 requirements. For 650°C test temperature and 689.5 MPa load, time to rupture of 35.9  0.62 h and final elongation of 5.4  1% are reported. The creep resistance of injection molded IN 713LC is lower compared to cast and hot isostatically pressed IN 713LC. A heat treatment consisting of solution annealing followed by an aging step leads to somewhat improved creep resistance (Horke et al., 2016). Similar results have been observed for injection molded CM 247 LC: creep properties of MIM material are inferior to cast and HIPed material, but can be improved by a solution and two step aging heat treatment (Meyer et al., 2017). However, creep strength in the range of cast alloy cannot be reached due to the fine grained microstructure (ASTM 8-10) after MIM. For further improvement of creep resistance, coarser microstructure would be required.

24.5

Potential applications

The development of superalloy parts fabricated by MIM is mainly driven by the aerospace sector. Cost reduction is the main driving force as MIM is a promising technology to meet cost saving targets. According to Schmees et al. (1997), with MIM IN 718 parts for gas turbine engine hardware, the cost reduction compared to machining of wrought material is >50%. Development, testing and validation have progressed significantly. Strong evidence for this is an increasing number of research publications and patents in this field. However, only few test data are published due to the fact that the research efforts are mainly financed by each company individually and thus will be kept confidential. Nevertheless, some examples for developments are mentioned in literature and on conferences. Unfortunately, in most cases no information is available if the technical readiness level has been achieved and if the product is in production or in service. Suitable are small to medium-sized complex parts with large production volumes (>10,000 annually). However, critical production volumes to achieve cost saving in the aerospace sector can be much smaller than in automotive industry due to greater geometric complexity and higher part prices for conventional manufacturing routes. Additionally, in aerospace, engine parts are required for many years as systems are in service for several decades, i.e., the numbers accumulate over the years. With regard to part size and numbers high pressure compressor parts and

602

Handbook of Metal Injection Molding

small turbine parts like compressor vanes and retaining plates appear best suited for MIM (Sikorski et al., 2006). Within a MIM development program of MTU Aero Engines AG compressor vanes could be produced with high-dimensional quality and low surface roughness. By brazing four vanes, vane clusters were obtained. These vane cluster prototypes were qualified for engine testing after successive brazing of a conventional honeycomb seal onto the inner shroud (see Fig. 24.10) (Sikorski et al., 2006). Another application for MIM parts that has been investigated by MTU are honeycomb seals for turbines (Albert, 2012; Sikorski et al., 2006). Accordingly, the alloys IN 713C and Mar-M247 have been the focus of research (Albert, 2012). This potential application is also subject of a patent application, which describes that the honeycomb seal is composed preferably of several segments. Each segment is embodied as a single piece and has a base element as well as honeycomb elements that are embodied as a single piece with the base element (patent US 20090041610 A1). Rolls-Royce reported on MIM as alternative manufacturing route to replace forged IN 718 compressor stator vanes (PIM, 2011). Stator vanes produced by MIM using polymethylmethacrylate (PMMA) and a water soluble polymer as binder components have been investigated. As reported, tolerances of 0.5% can be achieved. A single forging stage followed by a finishing process is applied to obtain desired dimensional and surface quality. More recently, large volume parts like compressor vanes, dampers, dowels, washers, lockplates, and sleeves were listed as potential candidates for MIM for aero-engines (Daenicke, 2017). Typical large volumes in the aero engine sector are in the range of an annual demand of approximately 1000–100,000. As pointed out earlier, the contract times are usually significantly longer compared to other industries, resulting in relatively large accumulated numbers. A typical compressor vane as candidate for MIM is shown in Fig. 24.11. G. Fribourg and J.-F. Castagne from Safran Aircraft Engines produced and investigated a Hastelloy X fuel nozzle fabricated by MIM. The current solution for

Fig. 24.10 Single MIM compressor vane (left) and MIM vane cluster prototype for engine testing (right). Courtesy of MTU Aero Engines AG.

Metal injection molding (MIM) of nickel-base superalloys

603

Fig. 24.11 High pressure compressor vane produced via MIM. Courtesy of Rolls-Royce Deutschland Ltd. & Co KG.

manufacturing this part consists of extrusion, machining, and brazing steps. The metal injection molded fuel nozzle is built up from four subparts that are injection molded separately, machined in the green state, assembled as green parts, debound, and sintered. The as-sintered parts are heat-treated to achieve the required material properties and finally machined. The assembled fuel nozzle is shown in Fig. 24.12 (Fribourg & Castagne, 2014). MIM was able to provide a high-dimensional stability, very good metallurgical quality, and good mechanical properties. Thus, the metal injection molded fuel nozzle has been successfully validated as alternative technology for one of Safrans’s development engines. This investigation took 3 years, including process setting and

Fig. 24.12 Aero engine fuel nozzle from Hastelloy X produced via MIM. Courtesy of Safran Aircraft Engines and Alliance-MIM.

604

Handbook of Metal Injection Molding

validation as well as supply-chain upgrading showing that the investigation of superalloy MIM components is an intensive development process (Fribourg & Castagne, 2014; Richard, 2017). The IHI Group, which is a major supplier to General Electric’s GE-90 engine used on Boeing’s 777 passenger jets, as well as to the GEnX engine used on Boeing’s Dreamliner, published results on the development of Alloy 718 compressor vanes (Williams, 2015). Sufficient fatigue strength and material strength was obtained for high pressure compressor applications. Complex compressor vane prototypes could be manufactured using a newly developed deformation-resistant binder system (Ikeda et al., 2014). Another important sector interested in nickel-base superalloy MIM parts besides the aerospace industry is the automotive industry. Nickel-base superalloy components in the focus of interest for fabrication by MIM are turbocharger components. An example of a turbocharger wheel prototype manufactured by Schunk Sintermetalltechnik GmbH is shown in Fig. 24.13. For this application, materials with good oxidation and corrosion resistance as well as excellent mechanical properties are required since the turbine wheel is driven by the engine’s exhaust gases. Nickel-base superalloys meet these requirements. Traditional turbocharger turbine wheels are manufactured by investment casting. MIM would be an interesting cost-efficient alternative manufacturing route. However, no evidence about MIM turbocharger wheels currently in use is available. Thus, it can be summarized that many research activities on MIM of superalloys are ongoing in aerospace and automotive sector. This is also proven by several patents and patent applications on MIM of superalloys by, e.g., BASF (e.g., patent EP 2416910 A1), MTU Aero Engines (e.g., patent DE102004060023 B4, DE102004057360 B4), Pratt & Whitney (e.g., patent US8316541 B2) and RollsRoyce (e.g., patent: DE102011089260 A1). However, published data and information about parts in service are quite rare.

Fig. 24.13 IN 713LC turbocharger wheel prototype produced by metal injection molding. Courtesy of Schunk Sintermetalltechnik GmbH.

Metal injection molding (MIM) of nickel-base superalloys

24.6

605

Conclusion and future trends

MIM of superalloys is generally comparable to other types of MIM materials such as steels. In several studies during the last 30 years, it was shown that nickel-base superalloys can be processed successfully via MIM and sintered to a relative density of >98% with moderate pick up of impurities like carbon and oxygen. Tensile properties of MIM material at low and intermediate temperatures are often comparable to cast or forged material. Unfortunately, ductility and creep resistance at high temperatures are often inferior for MIM, probably due to the existence of coarser precipitates/inclusions, remaining pores, PPB, and small grain size, respectively. Heat treatments or HIP with parameters known from cast or wrought materials can be used to close pores, alter the microstructure, and improve the mechanical properties. Unfortunately, generally only few data are available on relevant high-temperature mechanical properties as material characterization and validation times are long, expensive, and confident. According to the number of references, IN 718 has been studied the most, followed by IN 625 and IN 713. Much more data would be necessary in order to assess the application potential of different MIM nickel-base superalloys. Also an increased number of material standards would help to introduce MIM of nickel-base superalloys for a broader market and would minimize the individual development effort for interested companies. Some main challenges for the future are a better control of impurities in the MIM process, assuring microstructure and property repeatability and a robust supply chain. With regard to the chemical composition, up to now mainly alloys that have been developed for forging or casting were used for MIM. Alloy development programs designing specific MIM superalloys that take advantage of the rapid solidification in fine powders could help to improve the material performance.

References Albert, B. (2012). Hochtemperaturverhalten von Spritzguss-Nickelbasis-Superlegierungen am Beispiel von Honigwaben-Dichtungen (Ph.D. Thesis). University of Bayreuth. Albert, B., V€olkl, R., & Glatzel, U. (2014). High-temperature oxidation behavior of two nickel-based superalloys produced by metal injection molding for aero engine applications. Metallurgical and Materials Transactions A, 45A(10), 4561–4571. Beckman, J. P., & Woodford, D. A. (1988). Intergranular sulfur attack in nickel and nickel-base alloys. In S. Reichman, D. N. Duhl, G. Maurer, S. Antolovich, & C. Lund (Eds.), Superalloys 1998 (pp. 795–804). Warrendale, PA: The Metallurgical Society. Br€aunling, W. J. G. (2015). Flugzeugtriebwerke: Grundlagen, Aero-Thermodynamik, ideale und reale Kreisprozesse, Thermische Turbomaschinen, Komponenten, Emissionen und Systeme (4. Aufl). Berlin, Deutschland: Springer-Verlag. B€ urgel, R., Maier, H. J., & Niendorf, T. (2011). Handbuch Hochtemperatur-Werkstofftechnik: Grundlagen, Werkstoffbeanspruchungen, Hochtemperaturlegierungen und beschichtungen (4. Aufl). Wiesbaden, Deutschland: Vieweg + Teubner Verlag. Contreras, J. M., Jimenez-Morales, A., & Torralba, J. M. (2010). Influence of particle size distribution and chemical composition of the powder on final properties of Inconel 718 fabricated by metal injection Moulding (MIM). Powder Injection Molding International, 4(1), 67–70.

606

Handbook of Metal Injection Molding

Daenicke, E. (2017). MIM for aero-engine parts challenges & opportunities. Presented at the Euro PM2017 congress & exhibition, Milan, Italy, October 1–5. Davies, P. A., Dunstan, G. R., Howell, R. I. L., & Hayward, A. C. (2004). Aerospace adds lustre to appeal of master alloy MIM feedstocks. Metal Powder Report, 59(10), 14–19. Diehl, W., Buchkremer, H., Kaiser, H., & St€over, D. (1988). Spritzgießen von Superlegierungen und deren kapsellose HIP-Behandlung. Werkstoff und Innovation, 1(4), 48–51. Diehl, W., & St€over, D. (1990). Injection moulding of superalloys and intermetallic phases. Metal Powder Report, 45(5), 333–338. Donachie, M., & Donachie, S. (2002). Superalloys—A technical guide. Materials Park, USA: ASM International. Erickson, G. L., Harris, K., & Schwer, R. E. (1985). Directionally solidified DS CM 247 LC— optimized mechanical properties resulting from extensive γ0 solutioning. Presented at the gas turbine conference and exhibit, Houston, TX, USA, March 18–21. Fribourg, G., & Castagne, J.-F. (2014). Development of an aircraft engine combustion chamber part manufactured by metal injection molding (MIM). Presented at the 7th International EWI/TWI seminar on joining aerospace materials, Seattle, WA, USA, September 17–18. German, R. (1997). Supersolidus liquid-phase sintering of prealloyed powders. Metallurgical and Materials Transactions A, 28A(7), 1553–1567. German, R. (2011). Powder injection moulding in the aerospace industry: opportunities and challenges. Powder Injection Molding International, 5(1), 28–36. Gessinger, G. H. (1984). Powder metallurgy of superalloys. London, UK: Butterworths monographs in materials. Giamei, A. F., & Tschinkel, J. G. (1976). Liquid metal cooling: a new solidification technique. Metallurgical Transactions A, 7A(9), 1427–1434. Green, K. A., Lemsky, J. A., & Gasior, R. M. (1996). Development of isothermally forged P/M Udimet 720 for turbine disk applications. In R. D. Kissinger, D. J. Deye, D. L. Anton, A. D. Cetel, M. V. Nathal, T. M. Pollock, & D. A. Woodfood (Eds.), Superalloys 1996 (pp. 697– 703). Warrendale, PA: The Minerals, Metals & Materials Society (TMS). Gulsoy, H. O., Ozbek, S., Gunay, V., & Baykara, T. (2011). Mechanical properties of powder injection molded Ni-based superalloys. Advanced Materials Research, 278, 289–294. Harris, K., Erickson, G. L., & Schwer, R. E. (1986). CMSX® single crystal, CM DS & integral wheel alloys properties and performance. In Proceedings of high temperature alloys for gas turbines & other applications conference, Lie`ge, Belgium, October 6–9. Horke, K., Daenicke, E., Schr€ufer, L., Eichner, T., Langer, I., & Singer, R. F. (2014). Influence of heat treatment on microstructure and mechanical properties of IN 713LC fabricated by metal injection molding (MIM). In Advances in powder metallurgy & particulate materials – 2014 (pp. 112–118). Proceedings of the 2014 world congress on powder metallurgy and particulate materials (PM 2014), Volume 2, Part 4, Orlando, FL, USA, May 18–22. Princeton, NJ, USA: Metal Powder Industries Federation (MPIF). Horke, K., Scherr, R., Meyer, A., Daenicke, E., & Singer, R. F. (2016). Influence of heat treatment on tensile, fatigue and creep properties of nickel-base superalloy IN 713LC fabricated by metal injection moulding. In Proceedings of the powder metallurgy 2016 world congress & exhibition, World PM2016, Hamburg, Germany, October 9–13. Ikeda, H., Osada, T., Kang, H.-G., Tsumori, F., & Miura, H. (2011). Fatigue failure properties of injection molded superalloy compacts. Journal of the Japan Society of Powder and Powder Metallurgy, 58(11), 679–685. Ikeda, S., Satoh, S., Tsuno, N., Yoshinouchi, T., & Satake, M. (2014). Development of metal injection molding process for aircraft engine part production. IHI Engineering Review, 47(1), 44–48. Inco (1977). High-temperature, high-strength nickel base alloys (3rd ed.). Inco Brochure, The International Nickel Company, Inc.

Metal injection molding (MIM) of nickel-base superalloys

607

Jain, S. K., Ewing, B. A., & Yin, C. A. (2000). The development of improved performance PM Udimet 720 turbine disks. In T. M. Pollok, R. D. Kissinger, R. R. Bowman, K. A. Green, M. McLean, S. Olson, & J. J. Schirra (Eds.), Superalloys 2000 (pp. 785–794). Warrendale, PA: The Minerals, Metals & Materials Society (TMS). Johnson, J. L., Tan, L. K., Suri, P., & German, R. M. (2004a). Mechanical properties and corrosion resistance of MIM Ni-based superalloys. In Advances in powder metallurgy and particulate materials — 2004 (pp. 89–101). Proceedings of the 2004 PM2TEC2004 international conference on powder metallurgy & particulate materials, part 4, Chicago, IL, June 13–17. Johnson, J. L., Tan, L. K., Suri, P., & German, R. M. (2004b). Corrosion resistance of Ni-based superalloys processed by metal injection molding. In Proceedings from processing and fabrication of advanced materials XII, Pittsburgh, PA, October 13–15, 2003 (pp. 219–230). Materials Park, OH: ASM International. Kern, A., Bl€omacher, M., ter Maat, J., & Thom, A. (2010). MIM superalloys for automotive applications. In Proceedings of the powder metallurgy 2010 world congress & exhibition, World PM2010, Florence, Italy, October 10–14. Kim, K.-S., Lee, K.-A., Kim, J.-H., Park, S.-W., & Cho, K.-S. (2013). Manufacturing and high temperature mechanical properties of Inconel 713C by using metal injection molding. Advanced Materials Research, 602–604, 627–630. Kl€ oden, B., Jehring, U., Weißssg€arber, T., & Kieback, B. (2010). High-temperature properties of MIM-processed superalloys. In Proceedings of the powder metallurgy 2010 world congress & exhibition, World PM2010, Florence, Italy, October 10–14. Kl€oden, B., Jehring, U., Weißg€arber, T., Kieback, B., Langer, I., & Stein, R. W.-E. (2012). Fabrication of Ni- and Fe-based superalloys by MIM and their properties. In Proceedings of the PM2012 powder metallurgy world congress, Yokohama, Japan, October 14–18. Kl€ oden, B., Weissg€arber, T., Kieback, B., & Langer, I. (2013). The processing and properties of metal injection moulded superalloys. Powder Injection Moulding International, 7(1), 53–66. Meyer, A., Daenicke, E., Horke, K., Moor, M., M€uller, S., Langer, I., & Singer, R. F. (2016). Metal injection moulding of nickel-based superalloy CM247LC. Powder Metallurgy, 59(1), 51–56. Meyer, A., Horke, K., Daenicke, E., M€uller, S., Langer, I., & Singer, R. F. (2017). Metal injection molding of nickel-base superalloy CM247LC: influence of heat treatment on the microstructure and mechanical properties. In Advances in powder metallurgy and particulate materials 2017 (pp. 355–363). Proceedings of the 2017 international conference on powder metallurgy and particulate materials, POWDERMET 2017, Volume 1, Part 4, Las Vegas, NV, USA, June 13–16. Princeton, NJ, USA: Metal Powder Industries Federation (MPIF). Miura, H., Ikeda, H., Iwahashi, T., & Osada, T. (2010). High temperature and fatigue properties of injection moulded superalloy compacts. Powder Injection Moulding International, 4(4), 68–70. Nathal, M. V. (1987). Effect of initial gamma prime size on the elevated temperature creep properties of single crystal nickel base superalloys. Metallurgical Transactions A, 18A (11), 1961–1970. Nobrega, B. N., Eberle, N., & Ristow Jr., W. (2008). Mechanical properties of two MIM processed nickel-based superalloys. Materials Science Forum, 591–593, 252–257. Ott, E. A., & Peretti, M. W. (2012). Metal injection molding of alloy 718 for aerospace applications. JOM, 64(2), 252–256. € un, O., € G€ulsoy, H. O., € Yilmaz, R., & Findik, F. (2013a). Microstructural and mechanical Ozg€ characterization of injection molded 718 superalloy powders. Journal of Alloys and Compounds, 576, 140–153. € un, O., € G€ulsoy, H. O., € Yilmaz, R., & Findik, F. (2013b). Injection molding of nickel based Ozg€ 625 superalloy: sintering, heat treatment, microstructure and mechanical properties. Journal of Alloys and Compounds, 546, 192–207.

608

Handbook of Metal Injection Molding

Patel, S. J. (2006). A century of discoveries. inventors and new nickel alloys. JOM, 58(9), 18–20. PIM (2011). Rolls Royce investigates MIM superalloy stator vanes. PIM International, 5(3), 24. Reed, R. (2006). The superalloys—Fundamentals and applications. New York, USA: Cambridge University Press. Reichman, S., & Chang, D. S. (1987). Powder metallurgy. In C. T. Sims, N. S. Stoloff, & W. C. Hagel (Eds.), Superalloys II (pp. 459–493). New York, USA: John Wiley & Sons. Richard, S. (2017). Challenges of introducing MIM parts in aerospace. Presented at Euro PM2017 congress & exhibition, Milan, Italy, October 1–5. Salk, N. (2011). Metal injection molding of Inconel 713C for turbocharger applications. Powder Injection Moulding International, 5(3), 61–64. Schmees, R., Spirko, J. R., & Valencia, J. (1997). Powder injection molding (PIM) of Inconel 718 aerospace components. In F. H. (Sam) Froes & J. Hebeisen (Eds.), Advanced particulate materials and processes 1997 (pp. 493–499). Proceedings of the fifth international conference on advanced particulate materials and processes (APMP), West Palm Beach, FL, USA, April 7–9. Schmees, R. M., & Valencia, J. J. (1998). Mechanical properties of powder injection molded Inconel 718. In Advances in powder metallurgy and particulate materials Vol. 5, (pp. 107–118). Sidambe, A. T., Derguti, F., Russell, A. D., & Todd, I. (2013). Influence of processing on the properties of IN718 parts produced via metal injection Moulding. Powder Injection Moulding International, 7(4), 65–69. Sikorski, S., Kraus, M., & M€uller, C. (2006). Metal injection molding for superalloy jet engine components. In Cost effective manufacture via net-shape processing (pp. 9-1–9-12), Meeting proceedings RTO-MP-AVT-139, paper 9. Sims, C. T., Stoloff, N. S., & Hagel, W. C. (Eds.), (1987). Superalloys II. New York, USA: John Wiley & Sons. Tetsui, T. (2002). Development of a TiAl turbocharger for passenger vehicles. Materials Science and Engineering A, 329–331, 582–588. Valencia, J. J., McCabe, T., Hens, K., Hansen, J. O., & Bose, A. (1994). Microstructure and mechanical properties of Inconel 625 and 718 alloys processed by powder injection molding. In E. A. Loria (Ed.), Superalloys 718, 625, 706 and various derivatives (pp. 935–945). Warrendale, PA: The Minerals, Metals & Materials Society. Valencia, J. J., Spirko, J., & Schmees, R. (1997). Sintering effect on the microstructure and mechanical properties of alloy 718 processed by powder injection molding. In E. A. Loria (Ed.), Superalloys 718, 625, 706 and various derivatives (pp. 753–762). Warrendale, PA: The Minerals, Metals & Materials Society (TMS). Williams, B. (2015). Growing demand from the aerospace sector drives MIM superalloys research. Powder Injection Moulding International, 9(2), 45–50. Wohlfromm, H., Ribbens, A., ter Maat, J., & Bl€omacher, M. (2003). Metal injection moulding of nickel base superalloys for high temperature applications. In Proceedings of Euro PM2003 congress & exhibition, Valencia, Spain, October 20–22. Yupko, L. M., Svirid, A. A., & Muchnik, S. V. (1986). Phase equilibria in nickel-phosphorus and nickel-phosphorus-carbon systems. Soviet Powder Metallurgy and Metal Ceramics, 25(9), 768–773. Zhang, L., Chen, X., Li, D., Xuanhui, Q., Mingli, Q., & Li, Z. (2016). Net-shape forming and mechanical properties of MIM418 turbine wheel. Journal of Materials Engineering and Performance, 25(9), 3656–3661.

Metal injection molding (MIM) of precious metals

25

J.T. Strauss HJE Company, Inc., Queensbury, NY, United States

25.1

Introduction precious metal MIM: Precious metals and powder metallurgy

It is interesting to note that there are only a few current applications of powder metallurgy (PM) to precious metals but commercialized PM production began with precious metals, specifically platinum (Roll, 1984). Platinum was available as sponge (agglomerated powder) from refining or fine particles from mining. Melting platinum was very difficult and mainly unsuccessful. Consolidating platinum particles (powder) by applying pressure established enough particle-to-particle contact area and provided adequate thermal conductivity so that the compact could be further densified by heating (sintering) and working. Wollaston is credited in using “PM” in the first scaled production of malleable platinum in the early 19th century. The use of the Wollaston method became unnecessary as methods to bulk melt platinum were developed in the mid-19th century, ceasing further use and development of precious metal PM. That is not to say there are not other commercial uses for precious metal powder, they just lie outside of traditional PM processing. For example, 1. Structural solders/brazes in paste form: Solder and braze alloys (Ag-, Au-, and Pd-based) are available in paste form to facilitate their placement to braze joints. A metal powder of the solder or braze alloy is mixed with an organic vehicle (paste). The paste volatizes upon heating and the powder melts and fuses the joint. 2. Electronic solders and thick-film applications: Similar to solder and braze pastes, precious metal (gold and silver) powder (usually chemically precipitated) is mixed with an organic to form an “ink”. This ink is applied to an electronic substrate by screen lithography to form conductive paths or to pot electronic components. The substrate is heated causing the organic to volatize and the powder to sinter into a coherent conductive path. There are some inks that do not require the removal of the organic carrier to form conductive paths. 3. Dental: The most common application for precious metal powder in dentistry is in amalgam restorations (fillings). Alloy powder of the silver-copper eutectic and an alloy powder of silvercopper-tin are mixed with mercury and applied to the prepared tooth cavity. The mercury subsequently diffuses into the powder and forms a solidified amalgam. Other dental applications include the Captek process (Product of Argen Corporation, n.d.); a gold alloy powder mixed with a polymer and applied as a sheet to a porcelain substrate and subsequently fired and similar applications with palladium alloys (Product of Nobil-Metal S.p.A, n.d.). 4. Electrical: Electrical contacts and motor brushes are made from silver-graphite, silvertungsten, silver-molybdenum, silver-(Cd or Sn) oxide, or silver-nickel composites. Silver Handbook of Metal Injection Molding. https://doi.org/10.1016/B978-0-08-102152-1.00030-1 Copyright © 2019 Elsevier Ltd. All rights reserved.

610

Handbook of Metal Injection Molding

is used as the current carrier and the other materials add strength, arc resistance, and lubricity (in the case of graphite in motor brushes) to the composite. Press and sinter, hot press, and extrusion are all used in the production of precious metal electrical components. 5. PMC (Precious Metal Clay): This is a relatively recent application (McCreight, 2006). Precious metal powder (usually pure Ag, Au, or Pt), usually precipitated but can also be fine atomized powder, is mixed with an organic binder to yield a clay-like product. This is molded by hand to a part, which is subsequently fired-burning out the binder and sintering the powder. High densities are not achieved limiting this process to non-critical cosmetic items (jewelry). 6. Additive Manufacturing (AM): There is substantial interest in precious metal parts made by additive manufacturing, specifically via laser powder bed fusion. Most of the activity involves jewelry and watch cases, both of which are design-driven. EOS (www.EOS. info/press/customer_case_studies/glittering_prospects, n.d.), among other AM equipment manufacturers, make small chamber systems to minimize the high cost of filling a large conventionally sized build chamber. The majority of the interest is in Europe at this time.

As shown, there are many uses for precious metal powder but most are outside of what is considered traditional PM technologies. MIM for conventional materials, such as stainless steels, was able to develop quickly by using the extensive resources and knowledge base of press and sinter PM. There is no similar knowledge base or supply for precious metals. This has hindered the adoption of precious metal PM and MIM and only recently has there been commercial use of MIM in precious metal part production.

25.2

Applications for precious metal MIM

25.2.1 Current manufacturing processes for precious metal part production Since PM is not common in precious metal parts manufacturing, Design for Manufacturing (DFM) guidelines for precious metal PM have not been established. Thus, in order to ascertain potential applications and opportunities, one must review the current processes and parts made from precious metals. Parts made from precious metals include the following: Electrical/electronic contacts Medical: fiduciary markers, electrodes, embolization coils Coins/medallions Watch cases, watch parts Jewelry

The manufacturing methods to process these precious metal items include the following: Investment casting Deformation processes (rolling, extrusion, drawing, stamping, forging/striking/coining) Machining (lathe, mill) AM (Additive Manufacturing) Electroforming, electrophoresis

Metal injection molding (MIM) of precious metals

611

In the following general guidelines for MIM applications, MIM competes well with investment casting and discrete machining. Tube, sheet, and wire products are generally not complimentary to PM processes, nor are electroformed or AM parts. The parts that are commonly made by investment and discrete machining and also manufactured in quantities that would justify the cost of implementing MIM would primarily entail jewelry parts and watch parts. Precious metal watches are traditionally forged from wrought alloy to provide strength so these may not be good MIM candidates. Thus, for the most part, the precious metal manufacturing sector with the most potential for MIM are jewelry and jewelry parts (clasps, ferrules, etc. AKA “findings”) that would be normally be investment cast. Further discussion will address the jewelry sector.

25.3

Incentives for utilizing MIM for jewelry manufacturing

There are three driving forces that justify the use of any PM process over other manufacturing technologies: 1. PM enables a lower manufacturing cost. 2. PM is the only possible way to make the part. 3. PM produces a material or part of higher quality than other processes.

The vast majority of PM applications follow #1. Far fewer applications follow the other two reasons. Cemented carbides are a PM-only process as these composite alloys cannot be cast. PM (hot isostatic pressing (HIP)/extrude/forge) of nickel-based superalloys eliminates the solidification segregation of casting, producing a superior material. Certainly, there are other examples apart from these exceptions but the majority of PM applications are justified from cost savings. The use of MIM in precious metals must follow the same rules. Precious metal MIM either has to have a lower unit manufacturing cost (at equivalent quality levels), it must offer attributes that cannot be done via conventional jewelry manufacturing processes, or it must produce a superior product.

25.3.1 Cost basis Investment casting of jewelry is fragmented and diverse. There are some items that are unique and made in low production volumes. Other more universal parts, such as clasps, which can be used on a multitude of different products, are sometimes produced in large volumes (>50,000 parts per year). If one considers a dental bracket, a jewelry finding is very similar in size and geometric complexity. Thus, it follows that MIM would offer a cost advantage over investment casting, as it did for dental brackets (Riddle, 1992). However, unit cost is only part of the cost equation with precious metals. Much of jewelry production is essentially Just in Time (JIT). That is, parts are only cast when there is an order. Precious metal parts are rarely inventoried due to the high cost of metal. For example, the cost per kg of bulk 18 kt gold, 14 kt gold, and sterling

612

Handbook of Metal Injection Molding

silver are currently $32,000, $24,700, and $500, respectively (www.kitco.com/ market/index.html, 2018). The bulk of the precious metal inventory is not owned by the jewelry manufacturer. Rather, it is leased from banks and repositories. The manufacturer leases the material to fulfill their production requirements and pays back the lease when they are paid for the product (no long-term payments in jewelry). Thus, time is of the essence for throughput rates in manufacturing. In casting, the investment casting cores are made of a polymer and these can be inventoried at very little cost. When an order for a part is made, the inventoried core is added to a production casting tree. The time between receiving the metal, casting it, retrieving it, and finishing it can be less than a day, keeping the lease costs to a minimum. However, for MIM, there is additional time for the following: (1) feedstock preparation from the powder, (2) debinding of the part, and (3) sintering of the part (molding and finishing are assumed to be of the same time scale as for an investment casting). The MIM operation adds at least 24 h to the time to produce a part. In addition, powder production will add another 24–48 h to the time scale. This will add significantly to the cost of materials in the form of lease costs. However, this lease cost will be substantially different between silver and gold alloys. The cost of silver is significantly lower than gold, platinum, or palladium so the cost associated with time-inprocess may not be an issue with silver. Part of the JIT processing implies a high degree of flexibility; parts are only made when ordered. Consequently, for MIM to allow this degree of flexibility, individual parts would have to be able to be molded on demand. This would only be possible with small easily changeable molds. While this is possible it is not typically practiced. Most of MIM tooling is designed for long production cycles. Thus, at this time any application of MIM for jewelry would have to be for large volume production runs. MIM does offer some cost advantages over jewelry investment casting. MIM is inherently a lower labor cost operation. The lower unit labor cost is a result of a reduction in labor per unit part and also a lower labor cost due to lower skill sets required. Investment casting entails more steps at mid to high level of labor skill sets: assembling the casting tree, casting, and removing the part from the cast tree. Removing the cast part from the tree leaves a sheared area that requires more finishing compared to the gate area of a MIM part. Fig. 25.1 is a simplified schematic comparing a typical investment casting operation with a MIM operation. The MIM operation has fewer high relative cost unit operations, and fewer unit operations overall. In investment casting, the bulk of the tree and sprues, etc. can only be reused after cleaning and remelting. The recycle loop for MIM sprues, gates, runners, etc. is smaller as they can be granulated and put back into the molding feedstock; which is a lower cost operation than cleaning and remelting. In addition, there is less material per part as trees are not used in MIM to fill the mold cavity. Fig. 25.2 shows an investment cast tree of jewelry items. It can be seen that the volume of the tree is typically much greater than the jewelry parts being filled. Although reusing this excess can be as simple as cleaning and adding it to virgin material, the ratio of sprue to part is usually much >1 so used material to be recycled is generated faster than product. This implies that much more material needs to be inventoried for casting production than for MIM production.

Metal injection molding (MIM) of precious metals

613

Investment casting $$

Metal injection molding Plastic stock

Injection mold

$

Injection mold

Pelletize

Gating

$

Inspection

$$$

Tree

Gating

Scrap

Pour ceramic investment

$

Inspection

$

Tray Mix feedstock

Dewax

Air debind Tumble

Harden shell

$ $

Cast metal Remove investment

Scrap

Sinter

$

$ $$

Steps

Cost

IC

15

13

MIM

10

5

Inspection Inspection

Secondary operations

Tumble Leach

$$$$$

$

Inspection

$

Inspection

Detree

Fig. 25.1 A schematic of unit operations and relative costs for investment casting vs. MIM. From Strauss, J.T., & Santala, T. (1993). Powder injection molding (PIM) technology: overview and applications to the jewelry industry. In Proceedings of the 7th Santa Fe symposium in jewelry manufacturing technology.

Fig. 25.2 Investment cast trees showing the relative volume of parts to feed and support structure. Courtesy of John McCloskey, Stuller Settings, Lafayette, LA, USA.

614

Handbook of Metal Injection Molding

There are many economic considerations to be taken into account to make a case for MIM on cost alone. Labor savings are still considered the primary driver in MIM applications and for this reason MIM for jewelry, although developed in the US, was investigated in Europe prior to US applications. Fig. 25.3 contains examples of iconic European jewelry items from an early R&D study with MIM. Certainly, there are instances where MIM is justified, as there are several cases where MIM is used in production for sterling silver jewelry items (Staniorski, 2016).

25.3.2 Unique attributes or property/quality basis With respect to material properties, MIM will produce a microstructure that has a finer grain structure with an attendant improvement in mechanical properties and a reduction in chemical segregation with respect to investment casting. This can translate to improved tarnish resistance (Fioravanti, 1985; Raykhtsaum, 2002) which is an important attribute in jewelry. In addition, the finer grained microstructure produces a better polish (Weisner, 2003) than coarse grained material. MIM can offer some design features that are difficult to achieve with investment casting. Sinter-bonding can be used to make complex parts too difficult to mold or cast. Fig. 25.4 shows some hollow jewelry parts made by joining two parts during MIM processing. Molding over a consumable insert can also produce a hollow part as shown in Fig. 25.5. The insert dissolves during debinding. Flat parts or parts with abrupt changes in cross-sectional thickness are problematic in investment casting. Thin flat parts, such as medallions, are difficult to feed during

Fig. 25.3 Two as-sintered iconic jewelry articles MIM’d in 18 karat gold (coin for scale). Courtesy of H. Hilderbrand, Hilderbrand & Cie SA, Geneva, Switzerland.

Metal injection molding (MIM) of precious metals

615

Fig. 25.4 Sinter-bonded parts to make a hollow ring. Top: Green sterling silver hollow half ring. Bottom: Sintered and sectioned ring. Right: Sintered and semipolished ring. From HJE Company, Inc., NY, USA.

casting and abrupt thickness changes can produce shrinkage porosity at the intersection (Tyler Teague, 2018). MIM of thin flat parts is not an issue and can be readily done. Fig. 25.6 shows two medallions made by MIM that would be very challenging to investment cast. The porosity level of a jewelry part can be controlled through MIM processing. Porosity is not generally a positive attribute as it often causes surface defects or part failures for investment cast parts, where it usually exists as macro-porosity. However, in MIM, porosity exists as isolated micro-porosity and the amount, size, and distribution of the porosity can be controlled. The end goal of the jewelry part is to produce a surface of acceptable quality. Since most commodity jewelry items are sold on a per piece basis, having a part with a few weight percent porosity would mean a substantial saving in material and higher profits for the manufacturer. MIM development work with sterling silver found that up to 6% porosity could be incorporated and produce Fig. 25.5 Hollow sterling silver parts made by incorporating a consumable insert. Left: Green sterling silver ring with insert. Top: Soluble insert. Right: Sintered sterling silver ring (coin for scale). From HJE Company, Inc., NY, USA.

616

Handbook of Metal Injection Molding

Fig. 25.6 Sintered 18 karat gold parts made by MIM. Left: HJE medallion (with gate) with a thickness of 1.5 mm. Right: Sports team medallion with a thickness of 1 mm and a loop thickness of 0.5 mm. Center: Dental implant test part. The medallions are as-sintered. The dental implant part is polished (coin for scale). From HJE Company, Inc., NY, USA.

an acceptable surface finish for items such as signet rings and up to 3% porosity could be tolerated for higher-level jewelry pieces (Mohanty, 1998).

25.3.3 Economic/infrastructure considerations One of the key impediments to the adoption of precious metal MIM was the limited sources of MIM-grade precious metal powders. The transition from cast or machined dental brackets to MIM was straightforward as MIM grade stainless powder was readily available. The sources of gas atomized precious metal powders for use in precious metal solders and brazes cannot produce powder fine enough for MIM use (Beeferman, 1999). Atomization technology and equipment is available for making MIM-grade precious metal powder but until recently it was not common. The recent interest in powder bed additive manufacturing for jewelry has resulted in numerous new facilities with atomization systems dedicated to the manufacture of precious metal powders. This has generated renewed interest in precious metal MIM simply because the powder is available. Table 25.1 lists established precious metal powder producers. Other barriers to the adoption of MIM in precious metals include the cost of the MIM equipment and the availability of the technology knowledge base. As MIM has grown for conventional materials, equipment specifically designed for MIM has become more available. The MIM technology (binder formulations, processing

Metal injection molding (MIM) of precious metals

617

Table 25.1 A summary list of current precious metal powder suppliers capable of MIM-grade powder Company

Country

Argen Corporation Braze Alloy Corporation Cimini and Associates Cookson Precious Metals Hilderbrand/C
Hafner Legor Nobil Metals Prince Izant ProGold Technic, Engineered Powder Div.

US US US UK CH, DE IT IT US IT US

knowledge, etc.) has also become more available via published articles, trade conferences, and a significant and mobile MIM engineering work force. If precious metal MIM will progress, will a conventional MIM facility become a toll processor for a jewelry company or design house or will a jewelry facility integrate the MIM process into their operation? It is most likely that precious metal MIM will occur within the jewelry manufacturer (or precious metal manufacture) primarily because of the cost of the material and the security needed in the facility.

25.4

Alloy systems and powder production

Jewelry made of precious metals must meet industry requirements of established jewelry alloys in order to be hallmarked. Sterling silver is probably the most common jewelry alloy. Sterling silver has a minimum of 92.5% silver with the balance being copper or predominantly copper. Thus, sterling silver jewelry is hallmarked with a symbol that includes the numerals “925” meaning 925 parts silver per thousand. Pure silver (AKA “fine” silver) is marked as “999” meaning a minimum of 999 parts silver per thousand. Coin silver has a minimum of 90% silver and is thus marked “900”. Gold jewelry alloys are based on the “karat” system. Pure gold is 24 karat, meaning 24 parts gold per 24. In the US, the most common karat alloys are 18 (18/24 or 75%), 14 (14/24 or 58.3%), and 10 (10/24 or 41.7%) and these numbers will be part of the hallmark for these alloys. Gold is also available as 22, 20, and 12 karat as well. The karat denotes the minimum gold content and the balance can conceivably be anything else. However, the alloying elements are chosen for compatibility to produce alloys that are processible and have properties needed for jewelry (strength, ductility, tarnish resistance). The simplest gold alloy is a ternary of gold, silver, and copper. Different combinations of these elements will yield alloy colors of white, yellow, green, pink, and red. Fig. 25.7 is a ternary diagram that maps out the various alloys with respect to color and karatage. White golds often replace the silver with nickel, zinc, or

618

Handbook of Metal Injection Molding

Au RY

Yellow

20 40

Greenish yellowish

Yellowish

ht 50

rw eig pe 60

40

20

30

40

Whitish

50

60

70

10

90

Reddish

20

80

30

Red

%

Co p

ht

70

50

10

ig we

Cu

ld

10 Ct.

60

14 Ct.

Go

%

GY

70

30

GY-Green yellow

80

18 Ct.

90

10

RY-Red yellow

80

90

Ag

Silver weight % Fig. 25.7 Au-Ag-Cu ternary phase diagram showing color regimes. From https://web.wpi.edu/Images/CMS/MCSI/2006reti.pdf, 2006.

palladium. Nickel is being universally eliminated due to skin sensitivity, palladium is currently too costly, leaving zinc as a common alloying addition. Zinc is considered a requirement in 14, 12, 10, and 9 karat alloys as it richens the color. These alloys without zinc do not have as an acceptable a color (Grice, 2018). There are other trace elements that are often added to act as grain refiners and deoxidants as well. Platinum and palladium alloys are also marked as silver in parts per thousand, the most common alloys being 950 and 900, although 850 is also sometimes available. As with the other jewelry alloys, the noble metal content is called out and the remainder can be anything. Platinum is commonly alloyed with ruthenium, iridium, or cobalt. Palladium is commonly alloyed with ruthenium, gallium, and sometimes copper. In order for any of these precious metal alloys to be a candidate for MIM there are two obvious basic requirements: (1) the alloy is able to be atomized and (2) the atomized powder must be able to be sintered. There are challenges to each of these that are alloy-specific. Silver and gold alloys are readily atomized. All are relatively easy to melt as the liquidus temperatures are all modest with respect to stainless steels and the alloys are not very reactive. Conventional close-coupled inert gas atomization has been used to make MIM grade silver and gold alloys. There is also potential for atomizing these alloys with high pressure water atomization as is done for producing very fine stainless steel MIM powder.

Metal injection molding (MIM) of precious metals

619

As for sintering, most silver and gold alloys for jewelry will sinter. The primary issues come from the alloying additions that may inhibit sintering. For example, in karat gold alloys that contain zinc, the zinc oxide that forms during the atomization, handling, or in the MIM processing (specifically the debinding step) will not reduce at temperatures below the solidus temperatures. This will impede sintering. For gold alloys, it is recommended to use alloys of the gold-silver-copper ternary system. Casting alloys often contain deoxidizers and grain refiners. Neither is necessary if the alloy is to be atomized for MIM processing. Platinum and palladium are not as straightforward to atomize due to their very high liquidus temperatures. The temperatures needed for atomization are much higher than those used for casting, which can be challenging for the refractories used to contain and control the melt during atomization. For example, many of the platinum jewelry alloys have liquidus temperatures approaching 1800°C. Casting may only require 50° C superheat but close-coupled atomization for producing MIM-grade powder may require 100°C to 200°C superheat and for sustained times, which is above the use rating of most refractories. Nevertheless, there is at least one commercial source for atomized platinum alloy powders using gas atomization (Hilderbrand & Cie, n.d.). Recent developments in crucible-less atomization (EIGA, plasma wire, and plasma powder spheroidization) may have potential to make MIM-grade platinum alloy powder. Palladium jewelry alloys require atomization temperatures around 1700°C, making them less challenging. Precious metals are also available as “sponge,” the precipitated and agglomerated powder product that comes from refining. These powders are only available in the elemental metal, not alloys. While it is possible to make precious metal alloys via elemental mixing of powders, these precipitated powders are not optimum for MIM due to their high surface area and attendant low solids loading capabilities in the MIM feedstocks, which create difficulties in molding.

25.5

MIM processing

25.5.1 Silver and gold alloys MIM processing of silver and gold alloys is straight forward and very similar to MIM processing of conventional materials. The two primary differences are in binder formulation and tooling design. With respect to binder formulation, of primary importance are (1) the binder must be removed at a relatively low temperature and (2) debinding must not leave any carbonaceous residue. A binder for silver and gold jewelry alloys must accommodate the alloys’ low sintering temperatures and zero tolerance for carbon. Sintering of these alloys can initiate as low as 300°C (HJE Company, 1993). It is necessary that the binder be completely eliminated at these low temperatures or else residual binders will be trapped in the part. Related to this is that carbon is essentially insoluble in silver and gold jewelry alloys (McLellan, 1969). Unlike iron-based alloys, where residual carbon from the binder can be dissolved and diffused through the matrix to be subsequently

620

Handbook of Metal Injection Molding

removed in a low carbon potential sintering atmosphere, any residual carbon in a jewelry alloy compact will be trapped within the inter-powder microstructure with essentially no mechanism for its removal. This could impede sintering to full or usable density and the resulting pores or entrapped carbon could affect the cosmetics of the part. Wax-polymer binders suitable for copper MIM will be satisfactory for silver and gold jewelry alloys. Typical solids loading for gold and silver MIM feedstock can be between 57% and 67%, depending on the particle size distribution of the powder. Thermal debinding can be done in air as long as the alloy does not contain alloying additions whose oxide cannot be reduced during the sintering cycle. In Section 25.3, zinc was stated to be necessary to provide acceptable colors in 14 karat and lower alloys. Zinc oxides will be problematic as the oxide does not reduce until above the sintering temperature range of these alloys. The copper in the silver or gold alloy will oxidize during thermal debinding but copper oxides will be reduced in the subsequent sintering in a reducing atmosphere. Silver and gold alloys have higher-thermal conductivities than conventional materials. This enhanced heat transfer translates to the powder as well so the feedstock will have a higher-thermal conductivity and can better transfer heat to the tooling leading to faster cooling and solidification. This can be rectified by increasing the crosssectional area of the runners and sprues and by using warm tooling or hot sprues if found necessary. Sintering of these alloys is also straight forward. It has been found that a reducing atmosphere of nitrogen and hydrogen in almost any ratio is satisfactory for sintering. The sintering temperatures are alloy-dependent but tend to be within 100 degrees C of the solidus temperature.

25.5.2 Platinum and palladium alloys PM with platinum and palladium alloys is largely unrealized. Press and sinter PM for discrete jewelry articles was proven possible with precipitated powders and water atomized powder but MIM was not attempted as those powders were not appropriate (too coarse) (HJE Company, Inc, 2000). Sources of gas atomized platinum powder have only recently become available (Hilderbrand & Cie, n.d.). One of the issues with platinum and palladium MIM is that both of these metals are catalytic to hydrocarbons. It has been established that care must be taken in preparing thick-film pastes that use organic binders to avoid fires (Chitale, 2018). However, thick-film pastes use precipitated powders, which have a much greater specific surface area than atomized powders so the catalytic action may be suppressed. This is currently an area of research (HJE Company, Inc, 2017). Carbon is highly soluble in both platinum and palladium (Selman, Ellison, & Darling, 1978). When solubilized in the melt the carbon is ejected during solidification and forms graphite plates, much like the graphite in gray cast iron, and this negatively affects the mechanical properties of platinum and palladium alloys. Carbon that goes into solution in the solid phase during sintering may not behave in the same manner. This should not be an issue if the binder is removed entirely during debinding. The use of an oxidizing thermal debinding environment will be necessary.

Metal injection molding (MIM) of precious metals

621

Sintering of platinum and palladium powders should be achievable. Pure platinum and palladium could be sintered in air, as done with the thick-film pastes. However, jewelry alloys may contain elements that will require an inert or reducing atmosphere. Ruthenium is commonly added to platinum and ruthenium will form an oxide that is volatile within the sintering temperature range so oxidation should be avoided. Copper, cobalt, gallium, and germanium are also common alloying additions. All of these will oxidize therefore requiring a protective sintering environment. Hydrogen is very soluble in palladium and, to a lesser extent in platinum (Perrot, 2006) and will cause an appreciable lattice dilation. However, this is reversible upon cooling. If hydrogen is necessary to reduce alloy element oxides, it may be feasible to use a partial pressure of hydrogen to reduce the oxides and then finish the sintering under an inert gas atmosphere alone. This is an area that needs further development. The driving force for MIM platinum or MIM palladium may be greater than that for gold and silver alloys. Gold and silver are readily castable whereas platinum and palladium are difficult to cast. If MIM were proven for platinum and palladium alloys, this would present many opportunities in jewelry manufacturing.

25.5.3 MIM post processing In jewelry manufacturing, a prime goal is to achieve a high quality reflective surface finish. Most MIM products are above 95% density, with many approaching 99%. The residual porosity is very fine and evenly distributed in the microstructure. However, a metallographic examination will reveal this porosity even without magnification and it appears as a slightly matte finish or haze (HJE Company, Inc, 1998). This will not be acceptable for jewelry. That said, metallographic preparation is not applicable to jewelry. Jewelry finishing methods tend to work the surface, which produces a burnished surface and may conceal some surface defects. Thus, a finishing method that works or smears the surface is required to conceal the porosity. Involute surfaces respond well to tumbling with metal media (needles). Flat surfaces may require surface peening via tumbling prior to flat face polishing.

References Beeferman, D., 1999. Turbo Braze-Okai Corp., Union, NJ USA. Private communication. Chitale, S., 2018. ESL, div. Ferro Corporation, King of Prussia, PA USA. Private communication. Fioravanti, K. (1985). The effect of heat treatment on the chemical stability of low gold dental alloys. Master’s thesis Troy, NY: Rensselaer Polytechnic Institute. Grice, S., 2018. Hoover & Strong, Richmond, VA USA. Private communication. Hilderbrand & Cie, SA, Geneva, Switzerland. n.d. http://www.hilderbrand.ch HJE Company, 1993 Glens Falls, NY USA, Internal R&D. HJE Company, Inc, 1998 Glens Falls, N Y USA and Les Manufactures Suisses VLG, Neuchatel, Switzerland, Collaborative Research. HJE Company, Inc. 2000 Glens Falls, NY USA and Imperial Smelting & Refining Co. of Canada Ltd. Markham, Ontario, CA, Collaborative R&D.

622

Handbook of Metal Injection Molding

HJE Company, Inc, 2017 Queensbury, NY USA, Internal research. https://web.wpi.edu/Images/CMS/MCSI/2006reti.pdf. (2006). McCreight, T. (Ed.), (2006). PMC decade: The first ten years of precious metal clay. Brynmorgen Press. http://www.brynmorgen.com/books/samples/PMC-Decade.pdf. McLellan, R. B. (1969). The solubility of carbon in solid gold, copper, and silver. Scripta Metallurgica, 3, 389–391. Mohanty, B., 1998 Jostens, Burnsville, MN, USA. Private communication. Perrot, P. (2006). Hydrogen-palladium-platinum. G. Effenberg & S. Ilyenko (Eds.), Noble € Metal Systems. Selected Systems from Ag-Al-Zn to Rh-Ru-Sc. Landolt-Bornstein – Group IV Physical Chemistry. vol. 11B. Berlin, Heidelberg: Springer. Product of Argen Corporation, n.d. San Diego, CA USA. www.captek.com. Product of Nobil-Metal S.p.A., n.d. Villafranca d’Asti Italy. www.nobilmetal.it. Raykhtsaum, G., 2002 Leach & Garner General Findings, N. Attleboro, MA, USA. Private communication. Riddle, P. (1992). Metal injection molding at American orthodontics. Powder metal stainless steel course, MPIF, 11–12 February, 1992, Pittsburgh, PA. Roll, K. H. (1984). History of powder metallurgy. Metals handbook (9th ed.). (Vol. 7, pp. 14–20). American Society for Metals. Selman, G. L., Ellison, P. J., & Darling, A. S. (1978). Carbon in platinum and palladium. Platinum Metals Review, 14(1), 14–20. Staniorski, A., 2016 Cimini & Associates, Westerly, RI, USA. Private communication. Tyler Teague, J., 2018. JETT Research & Proto Products, Ashland City, TN USA. Private communication. Weisner, K. (2003). Metal injection molding (MIM) technology with 18ct Gold. A feasibility study. In Proceedings of the 17th Santa Fe symposium in jewelry manufacturing technology. www.EOS.info/press/customer_case_studies/glittering_prospects n.d. www.kitco.com/market/index.html. Accessed 3 February 2018.

Further reading Strauss, J. T., & Santala, T. (1993). Powder injection molding (PIM) technology: overview and applications to the jewelry industry. In Proceedings of the 7th Santa Fe Symposium in Jewelry Manufacturing Technology.

Index Note: Page numbers followed by f indicate figures and t indicate tables. A Activated sintering, 556 Additive manufacturing (AM), 431, 435, 449, 610 Additives, 290–291 Alloying methods elemental method, 55 master alloy method, 56 prealloy method, 55 Amorphous polymers, 59 Anisotropic shrinkage, 121–123 Apparent density, 50 Application testing, 272–273 Armstrong process, 447 Arrhenius equation, 236 Atomic force microscopy (AFM), 347 Atomization technique, 55 Attritor milling, 539–541 Austenisation temperature, 179 Austenitic steels, 410, 411t Autonomous optimization approach, 353–354 B Bagley’s correction, 230 Ball milling, 539–541 BASF Catamold binder system, 92, 130 Binders, 57–59 characteristics, 57, 58t chemistry, 59–61 constituents, 61 debinding process, 57–58 lab scale and commercial formulations, 84–85 low contact angle, 57 mixing technologies, 80–84 powder properties, feedstock effects flow, 62–68 removal, 73–80 shrinkage and warpage, 70–72 solidification, 69–70

systems, 130 viscosity, 57 Bingham systems, 62 Bioimplantable alloys, 29, 30t Bi-viscosity approach, 353 Blind holes, 343 Bloating defect formation, 77 Boundary element method (BEM), 229 Brown density, 132–133 Bulk transport mechanisms, 143 C Capillary flow porosimeter, 388 Capillary rheometer, 62, 208 Captek process, 609 Carbon control, in MIM, 281 additives, 290–291 atmosphere and temperature, 282 debinding, 292–293 sintering process, 293–298, 294–295f, 297–298f binder decomposition mechanisms binder burnout, 281 oxidative degradation, 288 residual carbon content, 289–290, 289f solvent debinding, 286–287 thermal debinding, 287–288 water debinding, 287 carbon content measurement, tools for elemental analyzer, 281–282, 284 FTIR and MS of gas, 281–282, 286 TGA, 281–282, 284–285, 285–286f carbon source, 281–284 cemented carbides, 281, 312–313, 321–323t high-speed steels, 299–305, 321–323t low-alloy steels, 311–312, 321–323t magnets, 281, 313–317, 321–323t residual carbon, influence of, 281 stainless steels, 281, 306–311, 321–323t

624

Carbon control, in MIM (Continued) titanium alloys, 281, 317–320, 321–323t Carnauba wax, 290 Case hardening operations, 182 Catalytic debinding (CD), 135–137 defects, 260 stainless steels, 414 Catamold binder system, 130 Cavity expansion factor, 94 Cemented carbides, 281, 312–313, 321–323t, 536–537 Chain depolymerization, 289 Clamp tonnage, 106 Cobalt-capping phenomenon, 566 Coinjection molding, 403–404 2C-PIM process one-, two-, or three-channel systems, 362, 362f vs. overmolding, 362, 363f Cold runner technology, 100–101 Compression ratio, 107–108 Computer-aided engineering (CAE), 207, 224 Computer tomography (CT) measurements, 353 Continuum modeling, 244 Controlled-expansion alloys, 28, 30t Coordinate measuring machine (CMM) units, 347 Copper (Cu) applications, 474 debinding and sintering, 469–471 feedstock preparation, 467–469, 468t heat sinks, 366–368, 367f molding, 469 powder characteristics, 466–467, 466t costs, 467 scanning electron micrographs of, 466–467, 467f thermal and electrical conductivity, 28 thermal properties, 471–473 Crack-Nicholson algorithm, 229 Cross-linked carbon, 289, 289f Cross-Williams-Landel-Ferry (WLF) equation, 65, 69t, 208–209, 219–220 Crystalline polymers, 59 Curve fitting coefficients, 65, 71–72 Custom molding, 4

Index

D Debinding, 373–375 atmosphere and temperature, carbon control, 292–293 copper, 469–470 2C-PIM, 363–366 defects, 265t carbon soot, 266 catalytic debinding, 260 oxide residues, 264–266 solvent debinding, 260–261 thermal debinding, 260, 262–264 high-speed tool steels, 527 microporous metals, PSH-MIM method debinding-sintering conditions, 376–377, 377f temperature, schematic drawing, 376–377, 377f thermogravimetric curves in, 376–377, 377f Mo-Cu, 489 nickel-base superalloys, 578–580 primary binders catalytic debinding, Catamold feedstock, 135–137 guidelines, 138–139 supercritical solvent debinding, 134–135 water-soluble systems, 137 wax-based systems, solvent debinding of, 132–134 secondary binders, 139–142 stainless steels catalytic debinding, 414 solvent debinding, 414 thermal debinding, 414 titanium, 436–437, 439 W-Cu, 479–480 weight loss, 274 Defects, in MIM debinding, 265t carbon soot, 266 catalytic debinding, 260 oxide residues, 264–266 solvent debinding, 260–261 thermal debinding, 260, 262–264 feedstock recycled feedstocks, 254–255 uniformity, 253–254

Index

mechanical factors, 253 molding causes and remedies, 259t, 260 flash, 255 flow marks, 258–260, 258f incomplete filling, 258, 258f powder/binder separation, 256–257 residual stress, 256 sink marks, 258 weld lines, 258–260, 259f sintering appearance and discoloration, 266 dimensional control and distortion, 266–267 Depolymerization-type polymer, 283–284, 284f Design for Manufacturing (DFM) guidelines, 610 Design guidelines, MIM attributes and fabrication techniques, 25, 26t bosses, 42 decorative features, 42 dimensional capability, 31 draft, 36–38 flats for sintering, 34–36 materials and properties, 26–30 radii/fillets, 41–42 ribs and webs, 40 surface finish, 31 threads, 38–40 tooling artifacts, 25 ejector pin marks, 32–33 gate locations, 33 parting line, 31–32, 32f undercuts, 42 wall thickness, 36 Die casting, 2 Differential scanning calorimetry (DSC), 210–213 Differential thermal analysis (DTA), 235–236 Dilatometry, 364, 365f, 528, 528f Directional solidification (DS) casting, 582 Direct metal deposition (DMD), 449 Dispersants, 61 Draft angles, 93 DSC. See Differential scanning calorimetry (DSC) Duplex stainless steels, 410, 411t

625

E EBM. See Electron beam melting (EBM) Economic analysis, 272–273 Einstein equation, 62–63 Ejector pin marks, 32–33 Elastic modulus, 72 Electrical discharge machining (EDM), 31 Electron backscatter diffraction (EBSD), 445–446, 446f Electron beam melting (EBM), 431, 435, 449 Electron probe microanalyzer (EPMA), 519–520, 520f Elemental analyzer, 281–282, 284 Elemental powders, 48 Ellingham diagrams, 151 Energy dispersion X-ray analysis (EDXA), 156–158 Energy equation, 225–226 EPMA. See Electron probe microanalyzer (EPMA) Ethylene vinyl acetate (EVA), 77 F F-15 alloy, 28 FDM. See Finite difference method (FDM) Fe-50Co alloy, 28 Feedstocks, MIM binder systems, 205 compositional characteristics, 207, 207t copper, 467–469, 468t defects recycled feedstocks, 254–255 uniformity, 253–254 flow critical solids loading, 62–63 particle characteristics, 65–68 relative viscosity, 62–64, 64f rheological characteristics, 62 shear rate effect, 64–65 temperature effect, 65 hardmetals powder preparation, 541 solids loading, 542, 543–544t heat capacity, 69–70 heavy alloys, 542, 543–544t high-speed tool steels, 526–527 melt rheology, 206 microcomponent PIM

626

Feedstocks, MIM (Continued) binder systems, 339–340 metal powders, 341–342 molybdenum-copper, 488 nickel-base superalloys, 577–578 plastics injection molding process, 205 PVT, 215–216 refractory metals powder preparation, 538–541 solids loading, 541–542 rheology, 207–210 shrinkage and warpage density, 71 modulus, 72 PVT parameters, 71–72 slip phenomena, 207 stainless steels, 411–414 thermal analysis, 210–213 thermal characteristics, 205 thermal conductivity, 69–70, 205–206, 214–215 titanium, 434 tungsten-copper, 478t, 479 volumetric heat capacity, 205 Fe-50Ni alloy, 500, 523–524 chemical compositions of, 516, 516t experimental procedure magnetic properties, 517–523 Ferritic steels, 410, 411t Fe–9.5Si–5.5Al alloy, 499–500, 523 chemical compositions of, 507, 507t gas- and water-atomized powders, magnetic properties of, 513–515 gas-atomized powder compacts, magnetic properties of, 507–512 Fe-6.5Si alloy, 499, 523 characteristics of, 500, 500t density measurement, 501 eddy-current loss, 504–507, 506f hysteresis loss, 504–507, 506f iron loss, 504–507, 506f relative density coercive force, 504, 505f hardness, 501–502, 502f magnetic induction, 504, 505f maximum permeability, 504, 505f mean grain size, 502, 503f oxygen content, 502–504, 504f sintered temperature, 501–502, 502f

Index

thermal debinding and sintering steps, 501, 501f toroidally shaped compacts, 501 Finite difference method (FDM), 228–229 Finite element method (FEM), 219, 222, 228, 245–246, 549–550 Fluorescence dye penetration test, 263–264, 263f Fourier transform infrared spectrometry (FTIR), 281–283, 286 Fray-Farthing-Chen (FCC)-Cambridge process, 447–448 G Gas atomization, 51–52, 619 Glass transition temperature, 59 Grain boundaries (GB), 144 Graphite-producing carbon contamination, 288 Green machining, 192–193, 192f H Hall-Petch relation, 582 Hardmetals cemented carbides, 536–537 feedstocks powder preparation, 541 solids loading, 542, 543–544t postsintering operations, 566 powder processing methods, 535 process concerns carbon control, 565–566 cobalt-capping phenomenon, 566 cracks, sinks, and voids, 564 distortion, 566 flash control, 563–564 low-pressure injection molding, 564 thermal debinding, 565 WC-Co hardmetals alloyed grades, 560–561 liquid-phase sintering, 561–562 micrograin grades, 560–561 process cycle, 562–563 Ru additions, 560 straight grades, 560–561 Hastelloy X (HX), 583, 585 HDPE. See High-density polyethylene (HDPE)

Index

Heat capacity, 69–70 Heat sinks, 461–463 Heat spreaders, 485–487 Heat treatment high-speed tool steels, 531 nickel-base superalloys, 580–583 Heavy alloys, 30, 30t feedstocks, 542, 543–544t powder processing methods, 535 tungsten heavy alloy counterweight, 536, 537f properties, 551–552 W-Ni-Fe and W-Ni-Cu alloys, LPS (see Liquid-phase sintering (LPS)) Hele-Shaw model, 224 Helium pycnometer, 132 Hermetic microelectronic packages, 16–17, 17f, 366–368, 367f High-density polyethylene (HDPE), 285, 285–286f High-speed steels (HSSs) carbon control, 299–305, 321–323t cutting bits, 525–526, 526f debinding, 527 feedstock, 526–527 heat treatment, 531 mechanical properties, 532 sintering, 528–531 stoichiometry of, 526, 527t High-temperature cofired ceramics (HTCCs), 366–368 High-temperature debind (HTB) oven, 131 Hot isostatic pressing (HIP), MIM, 28, 182, 437, 611 consolidating powders, 195–196 creep mechanism, 195–196 diffusion mechanism, 195–196 mechanical properties, 195–196 minimum density, 195–196, 196t nickel-base superalloys, 580–583 pores, 195–196 process benefits, 196–198 conditions, 200 issues, 199–200 sinter-HIP/pressure sintering, 196 temperatures, 196 tool steel, 525 Hot runner technology, 100, 100f

627

HSSs. See High-speed steels (HSSs) Hydraulic injection molding machine, 106 Hydraulic pressure switchover method, 115 Hydride-dehydride (HDH) powder, 434–435 Hydroxyapatite-316L composites, 418 Hygroscopic binder systems, 109–110 I Incomplete binder removal, 141–142 Inconel 625 (IN 625), 583, 586 Inconel 713 (IN 713), 583, 587–588 Inconel 718 (IN 718), 583, 587 Inductive heating, 344 Injection molding process applications basic defects, 233–234 filling time, optimization of, 235 material properties cooling stage, 231 filling stage, 230 packing stage, 231 verification, 231–233 numerical simulation cooling analysis, 229 coupled analysis, filling, packing, and cooling stages, 229–230 filling and packing analysis, 228–229 theoretical background and governing equations cooling stage, 227–228 filling stage, 224–226 packing stage, 226–227 theoretical background and governing equations, 224–228 In-mold labeling (IML), 351 Investment casting, 612, 613f, 614–615 Iron-based powders, 79 Isoelectric point (IEP), 291 Isothermal sintering, 545–547, 546f J Just in time (JIT), 611–612 K Kissinger method, 237–241, 240f Kovar, 266, 462 Kozeny-Carman’s equation, 388 Kroll process, 447

628

L Laser engineered net shaping (LENS), 449 Laser metal printing, 51–52 LIGA method, 337–339 Linear shrinkage equation, 116–118 Line-source method, 214 Liquid-phase sintering (LPS), 245, 299 WC-Co hardmetals, 561–562 W-Ni-Fe and W-Ni-Cu heavy alloys, 543–545 blistering, 551 densification, 545, 546f distortion, 549–551 grain growth-rate constant, 545–547, 547f grain size, increase in, 545–547, 546f green state cracks, 550, 550f initial, intermediate, and final stages, 545 process cycle, 547–549 Low-alloy steels, carbon control, 311–312, 321–323t Low contact angle, 57 Low-pressure injection molding, 105–106 Low-temperature burnout (LTB), 130–131 Low-temperature cofired ceramics (LTCCs), 366–368 LPS. See Liquid-phase sintering (LPS) M Magnets, carbon control, 313–317, 321–323t Mar-M247, 588–589 Martensitic steels, 410, 411t Mass spectrometry (MS) of gas, 281–283, 286 Master alloy method, 56 Master decomposition curve (MDC), 235–237 applications multireaction step decomposition, 241 single reaction-step decomposition, 240–241 theoretical background and governing multireaction steps, 237–239 single reaction steps, 236–237 Master sintering curve (MSC) model, 552–553, 555 Mechanical deformation, 176–178 Metal hydride reduction (MHR), 447

Index

Metal injection molding (MIM), 272f advantages of, 266 carbon content control (see Carbon control, in MIM) defects in (see Defects, in MIM) feedstocks (see Feedstocks, MIM) first MIM system, 130–131 furnaces batch furnaces, 164–167 continuous furnaces, 164, 167 evolution of, 163 profiles, 167–168 HIP (see Hot isostatic pressing (HIP), MIM) medium- or large-scale production, 334 microporous metals, PSH method (see Microporous metals, PSH-MIM method) molding equipment (see Molding) net-shape/near-net-shape components, 271 nickel-base superalloys (see Nickel-base superalloys) platinum and palladium alloys, 620–621 powder-binder formulation and compound manufacture in (see Binders) powders for (see Powder, MIM) reactivity of materials carbon steels, 155–156 corrosion resistant low carbon steels, 156–158 high alloyed steels, 156 high-temperature alloys, 158–159 precious metals, 155 reduced oxides, 155 refractory type materials, 159 titanium and alloys, 158 tungsten alloys, 158 secondary operations for (see Secondary operations, MIM) settering, 160–162 silver and gold alloys, 619–620 soft magnetic materials (see Soft magnetic materials) stainless steels (see Stainless steels, in MIM) thermal management (see Thermal management materials, MIM)

Index

in titanium and titanium alloys (see Titanium, MIM) tooling for (see Tools, MIM) Metal matrix composites, 418 Metal powder injection molding growth, 4–5 history of, 2–3 industry, 3–4, 7–8 market aerospace applications, 14, 17–18 automotive applications, 12 automotive components, 11–12 consumer components, 12 copper MIM heat transfer device, 15, 15f dental applications, 14 electronic components, 12 firearms, 12 in hand-held devices, 12 hermetic Kovar microelectronic package, 16–17, 17f industrial components, 12 jewelry applications, 15 lighting applications, 14 medical applications, 13 medical components, 11–12 micro-featured devices, 13–15 minimally invasive surgical tools, 13–15 by region, 10–11 robotic devices, 13–15 sales value, 12 sporting applications, 15 stainless steel MIM medical implant device, 16, 16f statistics, 10 titanium biocompatible structures, 16, 17f ultra-high-thermal conductivity composites, 15 powder metallurgy industry, 1–2 production capacity, 2 production sophistication, 18–19 production statistics, 4–7 sales statistics, 8–9 sintered materials technologies, 1 Microelectronic or microelectro-mechanical systems/microopto-electromechanical systems (MEMS/MOEMS) fabrication, 347 Microelectronics

629

copper (see Copper (Cu)) heat sink design, 461–463 material selection, 464, 465t Mo-Cu (see Molybdenum-copper (Mo-Cu)) thermal property measurement, 465 W-Cu (see Tungsten-copper (W-Cu)) Microinjection molding process, 344, 346t Micromachining, 337 Micro metal injection molding (MicroMIM), 418 ceramics, 333 microcomponents PIM debinding and sintering, 346–347 feedstocks, 339–342 metrology and handling, 347–348 molding procedure, 342–346 micromanufacturing methods, tool making LIGA method, 337–339 microstructured mold inserts, 335–336t, 337 microtools, 334–337 microtechnology, 333–334 multicomponent micro powder injection molding 2C-MicroPIM approach, 349–350 fixed and movable structures, 350–351 micro in-mold labeling, PIM feedstocks, 351 sinter joining, 351–352 simulation of, 352–354 Micromolding technology, 105–106, 108 Microporous metals, PSH-MIM method, 375–376, 392–396 control of porous structure experimental materials, manufacturing conditions, 381, 381t geometrical analysis, 386–387 sintering shrinkage, 382–384 sintering temperature, 384–386 debinding sintering conditions, 376–377, 377f temperature, 376–377, 377f thermogravimetric curves, 376–377, 377f extrusion and injection molding, 379–380, 379f functionally graded porous structures multilayered porous structure, 396–399 sandwich porous structures, 403–404

630

Microporous metals, PSH-MIM method (Continued) Ti-MIM, sequential injection molding, 399–402 liquid infiltration properties, 388–391 measurement, 387–388 Ni powder, PMMA particle, 378–379, 378f pore formation mechanism, 375, 376f particle size, effects of, 380, 380f SEM images and pore sizes of, 377, 378f Micro sacrificial plastic mold insert MIM (μ-SPiMIM), 374 MIM. See Metal injection molding (MIM) Mo-Cu. See Molybdenum-copper (Mo-Cu) Modeling and simulation, MIM injection molding process (see Injection molding process) mixing process continuity and momentum balance equations, 219 highly viscous PIM feedstock, 219 Kenics mixer, flow characteristics, 222 mixing analysis, 222–223 particle-tracking method, 219–221 WLF model, 219–220 sintering process (see Sintering) thermal debinding process (see Thermal debinding) Mold cooling analysis, 227 Molded threads, 39–40 Moldex 3D, 228 Mold filling, computer simulation, 102 Moldflow, 228 Molding auxiliary equipment granulators, 110 material drying, 109–110 mold temperature controllers, 110 part removal, 110–111 defects causes and remedies, 259t, 260 flash, 255 flow marks, 258–260, 258f incomplete filling, 258, 258f powder/binder separation, 256–257 residual stress, 256 sink marks, 258 weld lines, 258–260, 259f equipment

Index

conventional injection molding machines, 106–108 microinjection molding machines, 108 mold, 109 injection molding process anisotropic shrinkage, 121–123 backpressure, 112 cool time, 116 defects in, 123–124 fill rate, 111 gate freeze study, 111–112, 112f hold pressure and time, 115–116 injection speeds, 114 mold and melt temperature, 114 plastification, 112 PVT, 116–121 reciprocating screw, 111 shrinkage, 116 switchover point and method, 115 thermoplastics, 105 Molten feedstock, 90, 99 Molybdenum (Mo), 540f agglomerates, 253, 254f characteristics, 539t, 541 powder preparation, 539 properties of, 537t sintering mechanical properties, 556–557, 557t Mo-CeO2, 557 pure molybdenum, microstructure of, 556–557, 557f solid-state sintering, 555, 555f TZM and Mo-La2O3, applications, 537 W-Cu and Mo powders, solids loading, 541, 542f Molybdenum-copper (Mo-Cu) applications, 493–494 debinding and sintering, 489–491 feedstock preparation, 488 infiltration, 492 injection molding, 489 powder, 487 properties, 464, 465t thermal properties, 492–493 Monochromatic synchrotron radiation, 347–348 MSC model. See Master sintering curve (MSC) model Multiple cavity tooling, 99–100, 99f

Index

N Navier-Stokes equation, 224–225 Nickel-base superalloys applications, 575 cast nickel-base superalloys, 575 corrosion resistant high-temperature alloys, 575 MIM of, 575–576 IN 625, 583, 586 IN 713, 583, 587–588 IN 718, 583, 587 applications, 601–604 creep properties, 601 debinding and sintering, 578–580 fatigue properties, 600 feedstock preparation and injection molding, 577–578 Hastelloy X, 583, 585 Mar-M247 and CM 247 LC, 588–589 Nimonic 90, 583, 585–586 nominal composition, 583, 584t post processing (HIP/heat treatments), 580–583 powder preparation and quality, 576–577 tensile properties, 589–600, 592–599t U700, 583–585 U720/U720Li, 583, 585 polycrystalline wrought alloys, 575 Nickel-free stainless steels, 410, 417 Nimonic 90, 583, 585–586 Niobium (Nb), 540f characteristics, 539t, 541 powder preparation, 541 properties of, 537t, 538 sintering, 558–559, 559f No-flow temperature, 212, 213t Nordheim’s Rule, 472 Normalized entropy, 223, 223f O One-channel coinjection molding, 362, 362f Overmolding, 2C-PIM process, 361, 362–363f, 363 Oxide residues, 264–266 P P.A.N.A.C.E.A. steel, 417 Paraffin wax (PW), 2, 285, 285–286f

631

PARDISO, 220 Particle size distribution (PSD), 47–48 Particle-tracking method, 220–223 Parting line, 31–32, 32f Persistent liquid-phase sintering, 148 Phase-hardened (PH) stainless steel, 306–307, 410, 411t Plasma-quench process, 447 Plasticizers, 61 Platinum agglomerated powder, 609–610 and palladium alloys, 620–621 Plunger injection method, 105–106 Poisson equation, 224 Polishing method, 198 Polyacetal, 69–71, 283–284, 284f, 414 Polybutyl methacrylate (PBMA), 283–284 Polyethylene glycol (PEG), 109–110, 287 Polymer burnout method, 73 Polymethylmethacrylate (PMMA), PSHMIM method. See Microporous metals, PSH-MIM method Polyolefins, 283–284 Polypropylene (PP), 283–284, 284f Polyvinyl alcohol (PVA), 109–110 Polyvinyl chloride (PVC), 107–108 Porous materials, 371 Porous metals open porous metals, applications, 371–372 production methods advantages, 373 MIM, debinding in, 373–375 net-shape production, 372 porosity and pore size, 372–373, 373f Powder injection molding (PIM) of ceramics and carbides, 105–106 2C-PIM (see Two-color powder injection molding (2C-PIM)) global sales, 6–7, 6t production capacity, 5 Powder, MIM alloying methods elemental method, 55 master alloy method, 56 prealloy method, 55 characteristics apparent density, 50 PSD, 47–48, 50 pycnometer density, 49–50

632

Powder, MIM (Continued) shape, 48 size, 46–47 tap density, 50 copper characteristics, 466–467, 466t costs, 467 scanning electron micrographs of, 466–467, 467f fabrication techniques chemical reduction, 54–55 gas atomization, 51–52 manufacturing methods and attributes, 51, 51t thermal decomposition, 53 tungsten carbide grade powders, 51 water atomization, 52–53 molybdenum-copper, 487 nickel-base superalloys, 576–577 titanium, 434–435 tungsten-copper, 475–478 Powder space holder metal injection molding (PSHMIM), microporous metals. See Microporous metals, PSH-MIM method Power-law index, 222–223 Prado Principle, 10 Prealloy method, 55 Precious metal clay (PMC), 610 Precious metals, MIM alloy systems and powder production, 617–619 jewelry manufacturing processes cemented carbides, 611 cost basis, 611–614 economic/infrastructure considerations, 616–617 nickel-based superalloys, 611 unique attributes/property/quality basis, 614–616 metal parts production, current processes for, 610–611 and powder metallurgy additive manufacturing, 610 dental applications, 609 electrical contacts, 609 electronic solders and thick-film applications, 609 PMC, 610

Index

structural solders/brazes in paste form, 609 Pressure-volume-temperature (PVT), 71–72, 215–216, 226, 231f Prior particle boundary (PPB), 578, 578f Product qualification method, 272–273 Programmable logic controller (PLC), 133 Property evaluation, 272–273 PSD. See Particle size distribution (PSD) Pseudographitic carbon, 289, 289f Pycnometer density, 49–50 Q Qualification, MIM process application testing, 272–273 component mass, 278 debinding, 278 economic analysis, 272–273 feedstock behavior, 278 powder characteristics chemistry, 277 powder size and size distribution, 278 process control, 274–276 prototype methodology, 273 material selection, 274 tooling, 274 sintering chemistry analysis, 279 component density, 279 component dimension variability, 279 component mass, 279 crack detection, 279 mechanical testing, 280 microstructure, 279 X-ray, 279 R Rabinowitsch correction, 207, 230 Random scission, 289, 289f Rapid omnidirectional compaction (ROC), 559 Reciprocating screw technology, 105–106 Recycled feedstocks, 254–255 Refractory metals, 535. See also Hardmetals; Heavy alloys applications, 536–538 cost advantage, 535 feedstock formulation

Index

powder preparation, 538–541 solids loading, 541–542 powder processing methods, 535 properties of, 536, 537t sintering activated sintering, 556 process concerns, 559–560 process cycle, 556–559 solid-state sintering, 552–555 Relative viscosity, 62–64 Residual carbon content chain depolymerization, 289 pseudographitic and cross-linked, 289, 289f random scission, 289 side-group elimination, 289–290 Reynolds number, 224 Rhenium (Re), 540f applications, 537–538 characteristics, 539t, 541 disadvantages, 537–538 powder preparation, 541 properties of, 537t rhenium effect, 536 sintering activated sintering, 556 in hydrogen and HIPed, 558, 558f Rheocasting, 2 Rumpf equation, 75–76 Runge-Kutta method, 221 S Scanning electron microscopy (SEM), 51–52, 75, 245 Secondary operations, MIM appearance and surface properties, 183–190 applications, 190–191 competing technologies, 173, 175t conventional operations, 173 dimensional control factors, 174 high precision machine parts, 174, 176f mechanical deformation (sizing), 176–178 green machining, 192–193, 192f heat treatments, 179, 180–181t mechanical properties, 179–183 netshape technique, 173

633

tooling cost, 190–191 Semicrystalline polymers, 211–212 Sensitization process, 409 Sequential injection molding, 399–402 Shared load method, 200 Shrinking undegraded core/series model, 75 Side-group elimination, 289–290 SIMUFLOW, 228 Sinter-bonding, 614, 615f Sintering, 149–150, 619–621 applications gravitational distorting, 247–248 sintering optimization, 248–249 atmosphere and temperature, carbon control, 293–298, 294–295f, 297–298f chemistry analysis, 279 component density, 279 component dimension variability, 279 component mass, 279 copper, 469–471 2C-PIM, 363–366 crack detection, 279 defects appearance and discoloration, 266 dimensional control and distortion, 266–267 definitions, 142 Fe-6.5Si alloy, 501, 501f, 501t high-speed tool steels, 528–531 liquid phase, 147–149 mass transport mechanisms, 143–145 material properties and simulation verification data extraction techniques, 246–247 densification, 245 distortion, 246 grain growth, 245 mechanical testing, 280 microstructure, 279 molybdenum-copper, 489–491 nickel-base superalloys, 578–580 powder size and surface area, 150–151 practices, 146–147 refractory metals activated sintering, 556 process concerns, 559–560 process cycle, 556–559 solid-state sintering, 552–555 shrinkage, 117–118, 120, 120f

634

Sintering (Continued) stages of, 145–146 stainless steels, 414–416 theoretical background and governing equations constitutive relation, 244–245 numerical simulation, 245 theories, 142–143 titanium, 437, 439–440 W-Cu, 480–482, 480–482f W-Ni-Fe and W-Ni-Cu heavy alloys, LPS (see Liquid-phase sintering (LPS)) X-ray, 279 SLPS. See Supersolidus liquid-phase sintering (SLPS) Smoothed particle hydrodynamics (SPH) method, 353 Soft magnetic materials electromagnetic applications, 499 Fe-50Ni alloy, 500, 516–524 Fe–9.5Si–5.5Al alloy, 499–500, 507–515, 523 Fe-6.5Si alloy, 499–507, 523 Solid-state sintering, refractory metals, 552–555 Solvent debinding carbon control, 286–287 copper, 469 defects, 260–261 stainless steels, 414 titanium, 436 W-Cu, 479–480 Spark plasma sintering (SPS), 559 Stainless steels, in MIM advantage of, 409–410 applications, 419–424, 421–422t binders, feedstocks, and debinding, 411–414 boron additions, sintering improvements, 417 carbon control, 281, 306–311, 321–323t global market, 409–410 mechanical properties, 410, 411t metal matrix composites, 418 μMIM, 418 nickel-free stainless steels, 410, 417 performance of, 416–417 sensitization process, 409

Index

sintering, 414–416 two-color MIM, 418–419 Statistical process control (SPC), 115 Stearic acid (SA), 290–291, 290f Sterling silver, 617 Stokes equations, 220 Stress concentration factor, 41–42, 41f, 76 Supersolidus liquid-phase sintering (SLPS), 149, 299, 309–311, 579 Synchrotron radiation, 353 T Tab gate, 33, 34f Tait equation, 71, 72t, 226, 231 Tantalum (Ta), 540f applications, 538 characteristics, 539t, 541 powder preparation, 541 properties of, 537t sintering, 558 Tap density, 50 TGA. See Thermogravimetric analysis (TGA) Thermal conductivity, 69–70 Thermal debinding, 620 carbon control evaporation, 287–288 oxidative degradation, 287–288 thermal degradation, 287–288 conventional heat treatment, 235–236 copper, 469 defects, 260, 262–264 DTA, 235–236 hardmetals, 565 Mo-Cu, 489 stainless steels, 414 temperatures of common secondary binders, 139–140, 140t TGA, 235–236 titanium, 436–437, 439 W-Cu, 479–480 Thermal decomposition, 53 Thermal management materials, MIM copper (see Copper (Cu)) molybdenum-copper, 487–494 tungsten-copper, 475–487 Thermogravimetric analysis (TGA), 139–140, 140f, 235–239, 240f, 262, 281–282, 284–285, 285–286f, 291, 527

Index

Thermoplastic polymers, 59 Thermosetting polymers, 61 Thixomolding, 2 Threads, 38–40 Three-channel coinjection molding, 362, 362f Three-plate tooling, 96 Time switchover method, 115 TiRO process, 447 Titanium aluminides (TiAl), 452–454 Titanium dental implant, 16, 17f Titanium, MIM advantages, 431 carbon control, 281, 317–320, 321–323t challenges of binder, 435–436 biocompatibility, 437 feedstock, 434 interstitial elements, 432–434 porosity, 437 powder, 434–435 cost reduction cost-efficient powder production techniques, 447–448 Kroll process, replacement of, 447 powder blending, 448–449 mechanical properties fatigue properties, 445–446 tensile properties, 441–445 wrought vs. MIM-processed Ti-6Al-4V alloy, 440, 441f medical application, 449–451 processing debinding, 439 feedstock production, 438 injection molding, 438–439 powder handling, 438 sintering, 439–440 titanium aluminides, 452–454 Tools, MIM design options gating options and venting, 95–96 mold materials, 94 oversize design, 94–95 undercut design, 97–99 elements of, 91–93 injection molding machine, general design and function, 89–91, 90f software and economic aspects, 101–102

635

special features and instrumentation, 99–101 Tool steels dispersed carbides, 525 high-speed tool steels (see High-speed steels (HSSs)) HIP tool steel, 525 ingot cast, 525 Torque rheometer, 62 Transient liquid-phase sintering, 149 Tungsten (W), 540f activated sintering, 556 applications, 536 cemented carbides, 536–537 characteristics, 539t, 541 heavy alloys, 30, 30t counterweight, 536, 537f properties, 551–552 W-Ni-Fe and W-Ni-Cu alloys, LPS (see Liquid-phase sintering (LPS)) oxide additions, 536 powder preparation, 538–541 properties of, 536, 537t solids loading, 541, 542f solid-state sintering, 552–553, 553–554f, 555 tungsten carbide, 536–537 WC-Co hardmetals alloyed grades, 560–561 liquid-phase sintering, 561–562 micrograin grades, 560–561 process cycle, 562–563 Ru additions, 560 straight grades, 560–561 Tungsten-copper (W-Cu) debinding, 479–480 densification, 475 feedstock preparation, 478t, 479 heat spreaders and boilers, 485–487 infiltration, 482–483 injection molding, 479 powder, 475–478 properties, 464, 465t sintering, 480–482, 480–482f thermal properties, 483–484 Two-channel coinjection molding, 362, 362f Two-color MIM technology, 418–419

636

Two-color powder injection molding (2C-PIM) advantage, 368 automotive sensor holders, 366–368, 367f coinjection molding, 362, 362f copper-based heat sinks, 366–368, 367f debinding and sintering, 363–366 defect-free components, 368–369 hermetic microelectronic packages, 366–368, 367f overmolding, 361, 362–363f, 363 Two-material powder injection molding. See Two-color powder injection molding (2C-PIM) Two-sphere sintering model, 143, 144f Two-stage hydrogen reduction process, 541

Index

W Walking beam furnace, 164, 165f Wall slip phenomena, 207–208 Washburn’s equation, 389 Water atomization, 52–53 Water debinding, carbon control, 287 Wax-based feedstocks, 130 Wax-polymer binder system, 2, 69–70, 69–70t, 72t W-Cu. See Tungsten-copper (W-Cu) Wear resistance, 337, 342 White light interferometry, 347 Wicking process, 73 Wiech process, 163 Wiedemann-Franz relationship, 472 Wollaston method, 609–610

U Udimet 700 (U700), 583–585 Udimet 720 (U720), 583, 585 Udimet 720Li (U720Li), 583, 585 Ultraviolet (UV)-based lithography, 337–338 Uniform distributed/parallel model, 75

X

V

Y

Vacuum debinding, 469 Vacuum sintering, 293, 294f, 296 high-speed tool steels, 529–530 molybdenum, mechanical properties of, 556–557, 557t prealloyed Nb-30Hf-9W, 558–559 Volumetric shrinkage, 117–118, 119f Volumetric transition temperature, 71–72

Yield strength (YS), 177, 183, 195–196 Young’s modulus, 40

X-ray, 279 X-ray photoelectron spectroscopy (XPS) analysis, 290–291

Z Zinc-reclaim process, 541 Zirconia stabilized with yttria (YSZ), 160 Zirconia-toughened alumina (ZTA), 160