Fundamental of Materials Forming
-Processing of Powder Metals, Ceramics,
Glass, and Superconductors
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Typical Applications for Metal Powders
TABLE 17.1
Application
Metals
Abrasives
Fe, Sn, Zn
Aerospace
Al, Be, Nb
Automotive
Cu, Fe, W
Electrical/electronic
Ag, Au, Mo
Heat treating
Mo, Pt, W
Joining
Cu, Fe, Sn
Lubrication
Cu, Fe, Zn
Magnetic
Co, Fe, Ni
Manufacturing
Cu, Mn, W
Medical/dental
Ag, Au, W
Metallurgical
Al, Ce, Si
Nuclear
Be, Ni, W
Office equipment
Al, Fe, Ti
Source: R. M. German.
Uses
Cleaning, abrasive wheels
Jet engines, heat shields
Valve inserts, bushings, gears
Contacts, diode heat sinks
Furnace elements, thermocouples
Solders, electrodes
Greases, abradable seals
Relays, magnets
Dies, tools, bearings
Implants, amalgams
Metal recovery, alloying
Shielding, filters, reflectors
Electrostatic copiers, cams
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Powder-Metallurgy
(a)
(b)
(c)
Figure 17.1 (a) Examples of typical parts made by powdermetallurgy processes. (b) Upper trip lever for a
commercial irrigation sprinkler, made by P/M. This part is
made of unleaded brass alloy; it replaces a die-cast part,
with a 60% savings. Source: Reproduced with permission
from Success Stories on P/M Parts, 1998. Metal Powder
Industries Federation, Princeton, New Jersey, 1998. (c)
Main-bearing powder metal caps for 3.8 and 3.1 liter
General Motors automotive engines. Source: Courtesy of
Zenith Sintered Products, Inc., Milwaukee, Wisconsin.
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Making Powder-Metallurgy Parts
Figure 17.2 Outline of processes and operations involved in making powder-metallurgy parts.
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Particle Shapes in Metal Powders
Figure 17.3 Particle shapes in metal
powders, and the processes by which
they are produced. Iron powders are
produced by many of these processes.
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Powder Particles
(a)
(b)
Figure 17.4 (a) Scanning-electron-microscopy photograph of iron-powder particles
made by atomization. (b) Nickel-based superalloy (Udimet 700) powder particles
made by the rotating electrode process; see Fig. 17.5b. Source: Courtesy of P. G.
Nash, Illinois Institute of Technology, Chicago.
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Atomization and Mechanical Comminutio
n
Figure 17.5 Methods of metalpowder production by
atomization; (a) melt
atomization; (b) atomization
with a rotating consumable
electrode.
Figure 17.6 Methods of mechanical
comminution, to obtain fine particles: (a)
roll crushing, (b) ball mill, and (c)
hammer milling.
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Geometries of Powders
Figure 17.7 Some common
equipment geometries for mixing
or blending powders: (a)
cylindrical, (b) rotating cube, (c)
double cone, and (d) twin shell.
Source: Reprinted with permission
from R. M. German, Powder
Metallurgy Science. Princeton,
NJ; Metal Powder Industries
Federation, 1984.
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Compaction
Figure 17.8 (a)
Compaction of metal
powder to form a
bushing. The pressed
powder part is called
green compact. (b)
Typical tool and die set
for compacting a spur
gear. Source: Metal
Powder Industries
Federation.
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Density Effects
Figure 17.9 (a) Density of copper- and iron-powder compacts as a function of compacting pressure. Density greatly
influences the mechanical and physical properties of P/M parts. Source: F. V. Lenel, Powder Metallurgy: Principles
and Applications. Princeton, NJ; Metal Powder Industries Federation, 1980. (b) Effects of density on tensile
strength, elongation, and electrical conductivity of copper powder. IACS means International Annealed Copper
Standard for electrical conductivity.
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Density Variations in Dies
Figure 17.10 Density variation in compacting metal powders in various dies: (a) and (c)
single-action press; (b) and (d) double-action press. Note in (d) the greater uniformity of
density, from pressing with two punches with separate movements, compared with (c).
(e) Pressure contours in compacted copper powder in a single-action press. Source: P.
Duwez and L. Zwell.
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Compacting Pressures for Various Metal Powders
TABLE 17.2
Metal
Aluminum
Brass
Bronze
Iron
Tantalum
Tungsten
Other materials
Aluminum oxide
Carbon
Cemented carbides
Ferrites
Pressure
(MPa)
70–275
400–700
200–275
350–800
70–140
70–140
110–140
140–165
140–400
110–165
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Mechanical Press
Figure 17.11 A 7.3
MN (825 ton)
mechanical press for
compacting metal
powder. Source:
Courtesy of
Cincinnati
Incorporated.
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Hot and Cold Isostatic Pressing
Figure 17.12 Schematic diagram of cold isostatic pressing, as applied
to forming a tube. The powder is enclosed in a flexible container
around a solid core rod. Pressure is applied isostatically to the
assembly inside a high-pressure chamber. Source: Reprinted with
permission from R.M. German, Powder Metallurgy Science.
Princeton, NJ; Metal Powder Industries Federation, 1984.
Figure 17.14 Schematic illustration of
hot isostatic pressing. The pressure and
temperature variation vs. time are shown
in the diagram. Source: Preprinted with
permission from R.M. German, Powder
Metallurgy Science. Princeton, NJ;
Metal Powder Industries Federation,
1984.
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Capabilities Available from
P/M Operations
Figure 17.13 Capabilities,
with respect to part size and
shape complexity, available
from various P/M operations.
P/F means powder forging.
Source: Metal Powder
Industries Federation.
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Powder Rolling
Figure 17.15 An example of powder rolling. Source: Metals
Handbook (9th ed.), Vol. 7. American Society for Metals.
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Sintering Temperature and Time for
Various Metals
TABLE 17.3
Material
Copper, brass, and bronze
Iron and iron-graphite
Nickel
Stainless steels
Alnico alloys
(for permanent magnets)
Ferrites
Tungsten carbide
Molybdenum
Tungsten
Tantalum
Temperature
(° C)
760–900
1000–1150
1000–1150
1100–1290
1200–1300
Time
(Min)
10–45
8–45
30–45
30–60
120–150
1200–1500
1430–1500
2050
2350
2400
10–600
20–30
120
480
480
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Sintering
Figure 17.16 Schematic illustration of two mechanisms for sintering metal powders: (a)
solid-state material transport; (b) liquid-phase material transport. R = particle radius, r =
neck radius, and r = neck profile radius.
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Mechanical Properties of Selected
P/M Materials
TABLE 17.4
Designation
Ferrous
FC-0208
MPIF
type
N
R
S
FN-0405
S
T
Aluminum
601 AB, pressed bar
Brass
CZP-0220
T
U
W
Condition
Ultimate
tensile
strength
(MPa)
AS
HT
AS
HT
AS
HT
AS
HT
AS
HT
225
295
415
550
550
690
425
1060
510
1240
205
—
330
—
395
655
240
880
295
1060
45 HRB
95 HRB
70 HRB
35 HRC
80 HRB
40 HRC
72 HRB
39 HRC
80 HRB
44 HRC
<0.5
<0.5
1
<0.5
1.5
<0.5
4.5
1
6
1.5
70
70
110
110
130
130
145
145
160
160
AS
HT
110
252
48
241
60 HRH
75 HRH
6
2
—
—
—
—
—
165
193
221
76
89
103
55 HRH
68 HRH
75 HRH
13
19
23
—
—
—
Yield
Strength
(MPa)
Hardness
Elongation
in 25 mm
(%)
Elastic
modulus
(GPa)
Titanium
Ti-6AI-4V
HIP
917
827
—
13
—
Superalloys
Stellite 19
—
1035
—
49 HRC <1
—
MPIF: Metal Powder Industries Federation. AS: as sintered, HT: heat treated, HIP: hot isostatically pressed.
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Mechanical Property Comparison for
Ti-6Al-4V
TABLE 17.5
Density
(%)
100
100
98
> 99
100
Yield
strength
(MPa)
840
875
786
805
880
Ultimat
e
strength
(MPa)
930
965
875
875
975
Process(*)
Cast
Cast and forged
Blended elemental
(P+S)
Blended elemental
(HIP)
Prealloyed (HIP)
(*) P+S = pressed and sintered, HIP = hot isostatically pressed.
Source: R.M. German.
Elongatio
n (%)
7
14 40
8
9
14
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Reduction
of area
(%)
15
14
17
26
Page 20
Examples of P/M Parts
Figure 17.17 Examples of
P/M parts, showing poor
designs and good ones.
Note that sharp radii and
reentry corners should be
avoided and that threads and
transverse holes have to be
produced separately by
additional machining
operations.
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Forged and P/M Titanium Parts and
Potential Cost Saving
TABLE 17.6
Weight (kg)
Part
F-14 Fuselage brace
F-18 Engine mount support
F-18 Arrestor hook support fitting
F-14 Nacelle frame
Forged
billet
2.8
7.7
79.4
143
P/M
1.1
2.5
25.0
82
Final
part
0.8
0.5
12.9
24.2
Potential
cost
saving
(%)
50
20
25
50
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Characteristics of Ceramics Processing
TABLE 17.7
Process
Slip casting
Advantages
Large parts, complex shapes; low
equipment cost.
Limitations
Low production rate; limited
dimensional accuracy.
Extrusion
Hollow shapes and small
diameters; high production rate.
Parts have constant cross section;
limited thickness.
Dry pressing
Close tolerances; high production
rate with automation.
Wet pressing
Complex shapes; high production
rate.
Density variation in parts with high
length-to-diameter ratios; dies require
high abrasive-wear resistance;
equipment can be costly.
Part size limited; limited dimensional
accuracy; tooling costs can be high.
Hot pressing
Strong, high-density parts.
Protective atmospheres required; die life
can be short.
Isostatic
pressing
Jiggering
Uniform density distribution.
Equipment can be costly.
High production rate with
automation; low tooling cost.
Limited to axisymmetric parts; limited
dimensional accuracy.
Injection
molding
Complex shapes; high production
rate.
Tooling can be costly.
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Steps in Making Ceramic Parts
Figure 17.18 Processing steps involved in making ceramic parts.
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Slip-Casting
Figure 17.19 Sequence of operations in slip-casting a ceramic part. After the slip has
been poured, the part is dried and fired in an oven to give it strength and hardness.
Source: F. H. Norton, Elements of Ceramics. Addison-Wesley Publishing Company, Inc.
1974.
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Extruding and Jiggering
Figure 17.20 (a) Extruding and (b) jiggering operations. Source: R. F. Stoops.
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Shrinkage
Figure 17.21 Shrinkage of wet clay caused by removal of water during drying.
Shrinkage may be as much as 20% by volume. Source: F. H. Norton, Elements of
Ceramics. Addison-Wesley Publishing Company, Inc. 1974.
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Sheet Glass Formation
Figure 17.22 (a)
Continuous process for
drawing sheet glass from
a molten bath. Source:
W. D. Kingery,
Introduction to Ceramics.
Wiley, 1976. (b) Rolling
glass to produce flat
sheet.
Figure 17.23 The float method
of forming sheet glass. Source:
Corning Glass Works.
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Glass Tubing
Figure 17.24
Manufacturing process
for glass tubing. Air is
blown through the
mandrel to keep the
tube from collapsing.
Source: Corning Glass
Works.
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Steps in Manufacturing a Glass Bottle
Figure 17.25 Stages in
manufacturing an
ordinary glass bottle.
Source: F.H. Norton,
Elements of Ceramics.
Addison-Wesley
Publishing Company,
Inc. 1974.
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Glass Molding
Figure 17.26
Manufacturing a glass
item by pressing glass
in a mold. Source:
Corning Glass Works.
Figure 17.27 Pressing
glass in a split mold.
Source: E.B. Shand,
Glass Engineering
Handbook. McGrawHill, 1958.
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Centrifugal Glass Casting
Figure 17.28 Centrifugal
casting of glass.
Television-tube funnels are
made by this process.
Source: Corning Glass
Works.
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Residual Stresses
Figure 17.29 Residual stresses in tempered glass plate, and stages involved in inducing
compressive surface residual stresses for improved strength.
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PIM HISTORY
Manufacturers of the 21st century are requiring stronger, yet lighter
and more durable components that cost less. Fortunately, parts
manufacturers are no longer forced to choose between the production
limitations of metal die casting and the material limitations of plastic
injection molding.
The last decade has seen the development of a new manufacturing
process for metal and ceramic parts. This process, known as
Powdered Injection Molding “PIM” or Ceramic Injection Molding
“CIM”, are ideal for parts requiring complex geometry, which are
generally difficult to cast and costly to machine using traditional
manufacturing methods
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PIM HISTORY
• State-of-the-art equipment and technical expertise have made Britt
Manufacturing Company a leader in the Powdered Injection
Molding field. Using this process, we can eliminate many of the
design restrictions of conventional machining or casting
techniques. Significant component weight reductions are possible,
and multiple components can be redesigned and manufactured as a
single part, simplifying assembly.
• At Britt, we understand the exciting possibilities Powdered
Injection Molding presents to its customers in the aerospace,
appliance, automotive, dental, electronics, medical,
telecommunications, and tool industries. We welcome the
opportunity to demonstrate our expertise on your next project.
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POWDER INJECTION MOLDING
POWDERED METAL
POLYMER BINDER
FEEDSTOCK
INJECTION MOLDING
GREEN BODY
DEBINDING PROCESS
BROWN BODY
SINTERING OVEN
FINISHED PART
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POST MOLDING
Molded products are referred to as“Green Parts”.
Parts may be machined or other secondaries may be performed adding features in the
green state. If possible, machining is easier in the green state.
Green Part before secondary
(Milling)
Green Part after Milling (Snap
Ring Groove)
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DEBIND
Debinding is the removal of binders mixed with the metal or ceramic powders, which takes place after molding.
Britt capabilities include chemical (catalytic), solvent and water debind system. The debind method is determined by the
material to beprocessed, required physical properties, metallurgical requirements and chemical composition.
At Britt Manufacturing we are able to utilize three debinding systems, catalytic, solvent and water. Debound parts are
referred to as“Brown Parts”
Catalytic Debind Oven
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DEBINDING MECHANISM
Binder
Chemically
Removed, dissolved or
decomposed binder
Debinding
chemical or solvent
Metal or
Ceramic Powder
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DEBINDING MECHANISM
10 mm
Green
Part
30 min
10 mm
60 min
90 min
Dissolved or decomposed binder
Nitrogen
Debinding chemical or solvent
120 min
150 min
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SINTER
Parts are sintered with a temperature and atmosphere profile specific to the alloy being processed. Debound or “brown”
parts are sintered in vacuum or continuous type furnaces. At the lower temperatures of the sintering cycle (300°to 400°C)
the residual binder is removed. As the temperature increases, particles fuse, pore volume shrink, and grain boundaries form
at particle contacts. The grain size and part density depend on sintering time and temperature. The sintering temperature in
MIM range from 1,200°C to 1,400°C and for CIM they range from 1500°C to 1700°C. Part shrink 17-22% to nearly full
density.
 Secondary machining, heat treat or surface treatments are available.
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SINTERING
316L G 64 in Hydrogen
Temperature (c)
1600
1600
1400
1400
1200
1200
1000
1000
800
800
600
600
400
400
200
200
0
0
0
1 2 3
Time (h)
4
5
6
7
8
9
10
11
12
13
14
Page
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PIM POST SINTERING SECONDARY
Coining:
parts designed without a flat surface required for sintering may need straightening or “coining” to correct
minor shape and dimensional distortions.
Machining:
grinding, milling or other machining secondary operations are applicable, if necessary.
Heat Treat:
standard hardening methods are applicable
Coatings:
most any coating your application requires are possible. Some of the available are: chrome plate, black
oxide etc.
Finishing:
post sinter average finish 32 RMS. A better surface finish may be obtained with our in-house finishing
department.
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ADVANTAGES
Net Shape Forming
Integrate Several Functions Into One Part
Complex Geometry
High Production Rates
Near Properties Of Bar Stock Metal
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PIM Competes
With
Where
 Screw machine parts
 Part failure is a problem due to material failure
 Investment casting
(higher labor cost and design limits)




Volume in excess of 30M parts/year
Minimum bore diameter < 2mm
Wall thickness < 2mm
Surface roughness < 5um
 Powdered metal or “Press and Sinter”
(design limits)





Secondary machining becomes excessive
Two or more parts need to be joined
Internal or external threads are required
Part failure due to lack of density
Design requires parts with high aspect ratios
 Machining
(quantities, labor & machining costs)
 Quantities exceed 30,000 parts/year on simple parts
and 20,000 parts on complex parts
 Complex part geometry requires excessive machining
PIM competes where the design requires the flexibility of plastic injection molding and the mechanical and physical
properties near that of bar stock materials.
Page 15
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FEASIBILITY
Consideration for a good PIM or CIM candidate
Component should be:
 150 grams or less in weight (typical average 50 grams or less)
 Reasonably complex in design (combine components to be produced into one piece, for increased cost savings)
 Maximum wall thickness .5” (12.7mm)
 Minimum wall thickness .005” (.13mm)
 Tolerance Range
Typical
Best
- angular
+/- 2 deg
+/- .5 deg
- dimensional
+/- .3 %
+/- .001” (.0254mm)
Page 16
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POWDER INJECTION MOLDING PART DESIGN
PIM Part Design principals are similar to Plastic Molded Products.
 Draft angles, aiding in ease of part release from mold
 Uniform wall thickness is best
 Gradual wall thickness transition where wall thickness must vary
 Thick cross section should be cored obtaining lower production cost and assist in dimensional control
 Radius corners
Additional requirements for PIM are:
 Flat surface on component preventing sagging or slumping during sintering, custom trays with grooves or holes to allow for proper support are
optional.
 MIM Tolerance Range.
Feature
Typical
Best
Angle
+/- 2 deg
+/- .5 deg.
Dimension
+/- .3%
+/- .001” (.0254mm)
Tighter tolerance is possible with secondary operation.
 The flexibility of PIM component features may include: cross holes, angles, irregular shapes, undercuts, splines, gears and in some cases
threads

Gate location is critical for proper mold fill, but similar to ejector pin and mold parting lines, leave witness area on part surfaces. The location
of the molded imperfections may interfere with function as well as cosmetics. It may be to a designer’s advantage to work with us early in the
design stage to optimize your part design for PIM.
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