Powder Metallurgy or PM is a process of producing components or materials from powders made of metal. Different geometries can be obtained by this process. This may also include non metal powders. PM or Powder Metallurgy reduces the metal removal process to obtain a desired structure, reduces yield loss while manufacturing and cut down cost.
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2. Introduction
Powder Metallurgy or PM is a process of producing components or materials from powders made
of metal.
Different geometries can be obtained by this process. This may also include non metal powders.
PM or Powder Metallurgy reduces the metal removal process to obtain a desired structure,
reduces yield loss while manufacturing and cut down cost.
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Iron Metal Powder
3. Introduction
Powders are generally compressed by applying heat to obtain a specific geometry followed by
sintering to achieve a solid part.
Many unique materials can be made which is impossible to mold or melt.
For example tungsten carbide used for cutting and is used to make other metals is made by
powder metallurgy.
Some other products are:
• Automotive parts
• Sintered Filter (http://catalystrecoveryfilter.com/ , http://sparger.in/ , sintered disc for
sensor protection etc)
• Porous oil impregnated bearing
• Diamond tool
• Electrical contact
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4. Steps for Powdered Metallurgy:
1. Powder Manufacturing
• Metal used in manufacturing of powder are SS316L, Titanium, SS304, FeCrAl, 904L, Nickel
and many more.
• The two most common processes used in manufacturing of PM are:
a) Sponge Iron Process
b) Atomization
Sponge Iron Process
A magnetite (Fe3O4) ore with lime and coke are placed in a silicon carbide retort.
The retort is heated in a kiln thereafter where a slag and a sponge iron cake are
formed due to reduction process.
The iron cake is then crushed and annealed after separating from the slag.
The powder obtained is very irregular in shape containing internal pores which
looks like a sponge.
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5. Steps for Powdered Metallurgy:
Sponge Iron Process Contd.
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SPONGE IRON PARTICLE SHAPE
6. Steps for Powdered Metallurgy:
GAS ATOMIZATION
A hot liquid metal stream is passed from a orifice at high
velocity to generate turbulence and just before the molten
liquid stream exit the orifice a gas is injected which creates
this turbulence (gas expands due to heating and creates
turbulence).
The liquid stream is then collected in a collection volume filled
with gas where further turbulence is created. With the help of
a cyclonic separation, air and powder stream the PM particles
are separated.
The particles obtained are non porous, smaller, have more
breadth in size and are cleaner allowing better compaction.
Particles have a pear or spherical structure with an oxide layer
over them.
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7. Steps for Powdered Metallurgy:
Water Atomization
It is a technique in which atomized water at
high stream is introduced on a molten liquid
metal stream which converts the liquid metal
stream into drops and cools down the metal
powder before it reaches the collection
bottom.
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8. Steps for Powdered Metallurgy:
PM metal particles characteristics:
After manufacturing of metal powder
different sizes are obtained with the help of
screens which is made up of wire mesh. The
screens separate the metal powder
depending upon the sizes.
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9. Steps for Powdered Metallurgy:
Metal Powder Shape
The flow characteristic and powder density depends
on the shape of the metal powder. Different
techniques results in appearance of metal powder.
Water atomization produces irregular shapes with no
internal porosity.
Gas atomization produces spherical shapes with no
internal porosity.
Oxide reduction gives irregular shape with
substantial amount of internal porosity.
Milling and other mechanical techniques gives
variety of shapes.
Chemical techniques produce a range of shapes from
spherical to angular.
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“ATOMIZATION - THE PRODUCTION OF METAL POWDERS" A.
LAWLEY, MPIF -THE IMAGES ARE OBTAINED FROM DIFFERENT
PROCESSES SUCH AS FIG. 1-SPONGE IRON PROCESS, FIG.2-
ELECTROLYTIC PROCESS FOR COPPER PARTICLES, FIG. 3-
MECHANICAL PROCESS FOR ALUMINUM, FIG. 4-IRON WATER
ATOMIZATION & FIG. 5-NICKEL GAS ATOMIZATION.
10. Steps for Powdered Metallurgy:
Metal Powder Compaction
It is a process of compressing the metal powder in a vertically oriented tool
by applying pressure from top to bottom using a external force in this case a
punch tool.
After getting the desired shape or structure the compacted shape is ejected
from the die cavity.
This is the most cost effective manufacturing from rest of the process.
Two most commonly used processes are:
a) Die press Technology
b) Isostatic Pressing and Compaction
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11. Steps for Powdered Metallurgy:
Die press Technology
Die Press technology can be achieved by hydraulic
presses, mechanical and servo-electrical techniques, on
a larger scale hydraulic presses are commonly used.
The steps involved in a production cycle are:
A known volume of feedstock is filled in a die cavity.
Pressure is applied from the top and bottom by using
punches for compressing, this generally reduces the
density gradient level within compact.
Compacted metal is ejected using the pressure applied
by the lower punch.
The metal powder product is removed from the top
using the fill shoe.
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12. Steps for Powdered Metallurgy:
Major advantage of this technique is this, that it can
make complex geometries. The dimensions which
can be achieved are:
Area less than 0.65 square centimeter and larger
than 160 square centimeter and from 2.54
centimeter to 20 centimeter in length are possible.
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13. Steps for Powdered Metallurgy:
Isostatic Pressing and Compaction
The metal powder is placed in a mold and then a external pressure is applied by
using a gas or fluid as a source.
The compacted product is then sintered in a furnace which bonds or fuses the
metal particles and increases the strength of the material.
i. Hot Isostatic Pressing
Heat is applied to the metal powder from 480 degree Celsius to 1230 degree
Celsius by compressing and sintering the part simultaneously. An inert gas such as
Argon is used to prevent any chemical reactions during operation.
ii. Cold isostatic pressing
In this technique a fluid is used to pressurize the mold at room temperature. This
is followed by sintering the metal powder. A liquid is used as a medium to
distribute the pressure uniformly.
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14. Industries where the powdered metallurgy
are used :
Automotive products
Fluid technology
Bearings
Mechatronics
Filter Applications (Refer www.catalystrecoveryfilter.com & www.sparger.in for more details)
Industrial porous metal content
Read the next step, sintering by clicking the link http://catalystrecoveryfilter.com/free-
resources/api-research-papers/ scroll through the articles to view sintering process.
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