Advances in Particulate Materials

432 Pages·1995·9.221 MB·English

by  A. Bose (Auth.)

Advances in Particulate Materials
Animesh Bose
Parmatech Corporation
Petaluma, California
Butterworth-Heinemann
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Copyright © 1995 by Butterworth-Heinemann
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Library of Congress Cataloging-in-Publication Data
Bose, Animesh.
Advances in particulate materials / Animesh Bose.
p. cm.
Includes bibliographical references and index.
ISBN 0-7506-9156-5 (acid-free)
1. Particles. I. Title.
TP156.P3B68 1995
620'.43—dc20 94-44281
CIP
British Library Cataloguing-in-Publication Data
A catalogue record for this book is available from the
British Library.
Butterworth-Heinemann
313 Washington Street
Newton, MA 02158-1626
10 9 8 7 6 5 4 3 21
Printed in the United States of America
To my parents Mrs. Bani Bose and Mr. Amal
Kumar Bose, my wife Prarthana, son Pinaki
and daughter Shree
Preface
The chahenges in the area of advanced materials have resulted in the widespread
use of processing techniques that are based on particulate materials (P/M). With
the increasing demands of modern technology, P/M has emerged as the leading
material-shaping process that is flexible enough to fabricate near net-shape
products of extremely difficult-to-machine materials and yet attain very high
rates of production. The advantages of this unique process are currently being
exploited by material scientists and enginers to consolidate new and advanced
materials for the demanding aerospace, automotive, defense, chemical and
medical industries.
It is important to realize that individual particulates serve as the rudimentary
building blocks for the fabrication of useful components from these advanced
materials. This book introduces some of the basic powder production ap­
proaches and some of the underlying scientific principles associated with them.
Though some of the commonly used powder processing and consolidation
methods are briefly mentioned, detailed discussions dweh only around the more
recent advances in this critical area. The main emphasis of the book wih be
to provide readers with an in-depth coverage of a broad segment of the new
and exciting developments in the area of particulate materials.
I have divided the book into six chapters and a short introductory section.
The introductory section describes the contents of the various chapters in detail
and also acknowledges the important segments that could not be discussed. The
first chapter introduces the attributes, unique characteristics, problems, and
numerous applications of this technology and also briefly touches on some of
the safety regulations when using materials in the particulate form. The next
two chapters deal primarily with two popular powder production approaches,
namely melt atomization and chemical powder production approaches. The
fourth chapter on mechanical alloying deals with the power production,
consolidation, and some properties of these nonconventional materials. The
fifth chapter entitled "Intermetallic Compounds" deals with this specific class
xi
xü Preface
of material that has exploded into the area of advanced materials since the 1980s.
The last chapter discusses in detail the most signiñcant development in the area
of material-shaping technology, namely particulate injection molding. The
chapter provides the basic science and technology that is pertinent to near
net-shape processing of advanced materials using a process similar to plastic
injection molding. This chapter also covers the basics of the conventional
sintering processes used for material consohdation (both sohd- and liquid-phase
sintering).
It is my belief that the wide range of topics that have been covered in this
book will provide the interested reader with a broad overview of several
advanced topics in the area of particulate materials in sufficient depth. Though
this book tries to cover a section of the new and exciting developments in the
area of particulate materials, it by no means claims to have covered ah the "new
and exciting" topics in the P/M area. Due to the finite volume of the book,
it was necessary to select the topics that are covered in great detail. The aim
of this book is to cover a fairly broad cross section of the new and rapidly
developing areas of particulate materials in sufficient depth that readers with
a little background in material science can get a very good grasp of the exciting
possibilities that particulate materials have to offer.
I would like to take this opportunity to thank several individuals for their
help in getting the complete manuscript together. Special thanks are due to
Professor Randall M. German, Pennsylvania State University, for reviewing the
text and providing excellent guidance. The author would also like to acknowl
edge the work of Mr. Victor Hernandez, SwRI, in preparing some of the
excellent artwork. Special thanks are due to Mr. Karl Zueger, Parmatech
Corporation, for providing me with the opportunity to complete this enormous
task by creating conditions that are ideal for such intehectual exploration. I
would like to acknowledge the help provided by the dedicated staff of
Butterworth-Heinemann, especially Ms. Aliza Lamdan, Mr. Alexander Greene,
and Mr. Frank Satlow. The stimulating discussions with Dr. Malay Ghosh,
Alcon, provided the motivation for undertaking a project of this nature. I would
also like to acknowledge the support provided by Mrs. L. Galapate, Parmatech
Corporation, Dr. J. Strauss, HJE, Dr Richard Page, SwRI, and Mrs Mary
Bannon Stoner, MPIF. Lastly, the book would be incomplete without mention
of the assistance provided by Mrs. Prarthana Bose both in terms of encourage
ment to go ahead with the book and also for her tremendous help in the
manuscript preparation.
Aminesh Bose
Petaluma, CA
Introduction
Particulate materials (P/M) are increasingly playing a vital role in the processing
of advanced materials. The unique advantages provided by the P/M processing
route are currently being exploited by material scientists and engineers to
consolidate new and advanced materials for the ever-demanding aerospace,
automotive, defense, and structural components. With increasing demands of
modern technology, P/M technology has emerged as the leading metalworking
process that is flexible enough to fabricate near net-shape products of materials
that are extremely difficult to machine and yet attain very high rates of
production.
For the readers to get a reasonably good understanding of the P/M processes
and how the particulate materials are consohdated into useful bulk shapes, it
is important to realize that individual particulates serve as the rudimentary
building blocks for the fabrication of these advanced parts. This book wih,
therefore, introduce the basic powder production approaches and some of the
underlying principles associated with them. Though some of the commonly used
powder processing methods wih be briefly mentioned, detailed discussions wih
only dweh around the more recent advances in this critical area. Similarly,
traditional consolidation techniques such as cold compaction and sintering will
not be treated as separate chapters. Some of the cold consolidation techniques
will be briefly touched in the first introductory chapter and some of the
conventional sintering methods will be included in Chapter 6 on Particulate
Injection Molding. Numerous pressure-assisted hot consohdation techniques
will, however, not constitute a part of this book, primarily due to their sheer
volume. The main emphasis of the book will be to provide readers with an
in-depth coverage of a broad segment of the new and exciting developments
in the area of particulate materials. The book will be divided into six chapters,
which are outlined below:
1. Introduction to Particulate Materials
xiii
xiv Introduction
2. Chemical Powder Production Approaches
3. Melt Atomization
4. Mechanical Alloying
5. Intermetahic Compounds
6. Particulate Injection Molding
The introductory chapter ñrst initiates the readers to the term "particulate
materials," and provides some of the reasons why it is necessary to use the term
"particulate materials" instead of the more commonly used name of "powder
metallurgy." The next section of that chapter introduces the readers to different
types of particulate materials that are used for processing advanced materials
and some of their important powder characteristics. A brief discussion on
several aspects of safety and regulations when using materials in the particulate
form, especially when it is in the submicrometer range, should be of interest.
The toxic effect of some powders on the human system is also brieñy touched
in this chapter. The ñrst chapter also briefly covers the cold consolidation
techniques of die compaction, cold isostatic pressing, and the CONFORM
process. Lastly, the chapter deals with some of the apphcations of this unique
P/M process.
The next few chapters provide detailed coverage of a number of powder
production methods. The basic premise is that almost ah materials can be
reduced to powders provided there is input of sufflcient energy. Very large
energy consumption wih resuh in an increased price tag for the powder, which
in turn will reduce its use. However, if there is sufflcient value added to the
part, the higher price of the powders can be justifled. In the particulate injection
molding (PIM) process, where complex shapes can be produced easily (which
provides a value-added component) the added price due to the ñne powder
requirement is acceptable as long as the total process economics is comparable
or better than the competing processes. In some cases, however, P/M processing
is the only possible route for fabricating the required component. In such cases,
high powder production costs are often justifled. Similarly, high-tempera
ture refractory metals, the majority of the structural ceramics, dispersion-
strengthened composites, etc., are good examples where higher powder
production costs can be justifled.
The basic powder fabrication approaches are discussed under several broad
chapters, such as chemical powder production approaches, melt atomization,
and mechanical alloying. Some of the processes discussed are already producing
powders that are being used extensively in fabricating advanced materials. Some
of the processes discussed in these chapters are presently laboratory curiosities,
but possess the attributes of becoming extremely important powder fabrication
routes in the near future. However, it should be mentioned that well-known
Introduction xv
processes for powder production, such as electrolytic processing, mechanical
mihing, beneñciation of ores followed by metal extraction, and common
chemical approaches such as that used in the production of tungsten and
molybdenum powders (e.g., reduction of tungsten oxide obtained from
ammonium paratungstate) will not be covered in this book. A detailed
description of the majority of the common powder processing approaches has
been very well covered in most of the powder metallurgy textbooks, both old
and new. This book will attempt to cover some of the recent developments in
powder fabrication. However, there will still be a number of novel processes
that will not be adequately covered. As a case in point, the process of chatter
machining to produce powders with high aspect ratios will not be discussed.
It should be mentioned that though the chapter on mechanical alloying will
deal extensively with powder production, this chapter will also discuss the
consolidation and some of the properties of these nonconventional materials.
Thus, the chapter cannot be classified as dealing only with powder production,
as in reality its coverage includes the making of the powders, their consolidation,
and also some of the properties of these advanced materials. This chapter also
includes discussions on amoφhous or glassy metals and ahoys, nanocrystalline
materials, and new materials with extended solid solubility. The chapter on melt
atomization, for the most part, deals exclusively with powder production, except
for a small section on spray forming, which in reality is a combination of powder
production and powder consolidation techniques rolled into one. In contrast,
the chapter on chemically produced powders deals almost exclusively with
powder production techniques.
The fifth chapter, entitled 'Tntermetallic Compounds," offers coverage of this
rapidly developing class of materials with very interesting property combina­
tions. This chapter, in a true sense, deals with a specific class of material.
Intermetallic compounds have exploded into the area of advanced materials
since the 1980s. It was decided that this class of materials was so unique and
has become so important that it warrants a separate chapter by itself. The
chapter starts with a description of what intermetallic compounds are and their
importance in the materials arena, later goes on to discuss specific compounds such
as nickel aluminides, titanium aluminides, iron aluminides, silicide-based
intermetallic compounds, and several other classes of intermetallic com­
pounds.
The last chapter, on "Particulate Injection Molding," discusses the key steps
associated with this net-shape processing technique that in recent years has shot
into the limelight. Some of the exciting developments in the area of particulate
injection molding such as the formation of ahgned fiber-reinforced composites,
injection molding of thixotropic materials that uses particulates as the starting
material, development of several new binder systems and the processes adopted
xvi Introduction
to remove the binders, freeze compression molding of materials mixed with
water based binders, etc., are discussed in detail. It was felt that this material
shaping process was so important that its individual processing steps such as
feedstock formation, injection molding, debinding, and sintering deserved
detailed coverage. This provided the opportunity of covering some of the
conventional sintering processes used for material consolidation (both solid and
hquid phase sintering). It should be remembered that the process of sintering
is also applied to densify green shapes that can be attained by other P/M
methods such as conventional die pressing and cold isostatic pressing that are
briefly described in the first introductory chapter.
Though this book tries to cover a section of the new and exciting
developments in the area of particulate materials, it by no means claims to have
covered all the "new and exciting" topics in the P/M area. This is an appropriate
place to mention some of the topics that could not be covered within the
scope of this book, and thereby acknowledge their importance in the area
of particulate materials. Some of these topics are: explosive compaction,
laser glazing, solid free-form processing, smart processing of particulate
materials, dynamic consolidation, ceramic materials in general, roh compaction
processes, high-temperature sintering (as apphcable to ferrous materials),
secondary operations, application of computers in particulate material technol­
ogy, developments in compaction presses and sintering furnaces, microwave
sintering, rate-controlled sintering, and numerous pressure-assisted hot con­
solidation techniques such as rapid omnidirectional compaction (ROC), hot
isostatic pressing, hot pressing, sinter+HIP, CERACON™, Quick HIP,
bioactive ceramics and other particulate-based biomaterials, and others. Due
to the finite volume of a book, it was necessary to select the topics that would
be covered in great detail, and in the process to be forced to leave out a number
of other important topics.
When writing a book on the new and exciting developments in any processing
area that covers a very broad range of topics it becomes extremely difficult to
pick and choose the areas that will be covered in any great detail. If an attempt
is made to cover almost every exciting development in the area of particulate
materials in any meaningful detail, the information can in no way be
incorporated into the structure of just one or two books, simply owing to its
sheer volume. To provide a case in point, the topic of particulate injection
molding (whose subsections are known as metal injection molding, or ceramic
injection molding, or powder injection molding) has been the subject of several
books and conference proceedings; thus, if any extensive coverage in that area
is attempted, the topic by itself would probably require at least two or three
large books. There wih always be a need for books dedicated entirely to such
new, exciting, and rapidly developing areas as rapid sohdification, particulate
Introduction xvii
injection molding, melt atomization, mechanical alloying, etc. However, that
was not the purpose of this book — as is clearly evident from the title "Advances
in Particulate Materials." The aim of this book is to try to cover a fairly broad
cross section of the new and rapidly developing areas of particulate materials
in sufficient depth, so that readers with a little background in material science
can get a very good grasp of the exciting possibilities that particulate materials
have to offer. Attempts have been made to briefly provide the fundamentals
of topics covered in any detail, and then to discuss the development of the
technology based on the fundamental principles. For readers who wish to delve
at greater depth into one particular topical area, this book provides a significant
number of references that can suitably guide them toward that goal. Unfor­
tunately, to provide a broad coverage with sufficient depth it has been necessary
to make some difficult choices with regard to the topic selections. The readers
would appreciate that within the scope of one book, it would have been
impossible to cover all topics that can be deemed as "new, exciting, and rapidly
proliferating." Though the choice of the topics is a reflection of my personal
preferences, it is expected that the topics discussed cover a significantly broad
area that will be of interest to a large cross section of readers.
An alternate way of attempting to write a book of this nature, and yet keep
it within some manageable magnitude, was to try to cover nearly ah the exciting
topics (most of which could be several books by themselves) of certain interest
within a few pages. However, that coverage would have been so superficial in
nature that the readers would not have gained any understanding of the process
or the material whatsoever. Thus, a difficult choice was made to limit the
coverage of the topics to the chapters that have been outlined earlier. It is
expected that the broad range of topics that have been covered in reasonable
detail will aid a relatively broad spectrum of readers in their endeavor to gain
a more in-depth understanding of what P/M technology can offer and also to
give some an idea about the recent developments in their particular area of
interest. Also, the references, around 80% of which are after the 1980s, should
provide the reader with a recent reference source covering the developments
in the areas of particular interest.
With this brief preview of the chapters and the basic philosophy of this book,
I would like to conclude this brief introductory section. It should be remembered
that the initial success of P/M technology was rooted in the ability of this process
to produce unique materials in very high volumes and at significantly lower cost.
Self-lubricating bronze bearings and WC-Co-based cermets are a couple of
examples that epitomize the early P/M successes. Obtaining the controlled
porous structure that could retain the lubricating oil was a unique attribute that
could be provided only by P/M processing. The press-and-sinter method was
suitable for very high production volumes and the copper and tin powders