Powder metallurgy is a process that makes materials or components from metal powders rather than melting metals. It involves blending metal powders, compacting them into shapes, and sintering them by heating below the melting point to fuse the particles together. This allows for mass production of parts with complex shapes that would be difficult to make through other methods. An example of a material commonly made through powder metallurgy is tungsten carbide, which is used to cut other metals.

1. ME8712 - TECHNICAL SEMINAR

3.  Powder metallurgy (PM) is a term covering a wide
range of ways in which materials or components are
made from metal powders.
 PM processes can avoid, or greatly reduce, the need to
use metal removal processes, thereby drastically
reducing yield losses in manufacture and often resulting
in lower costs.

4.  Powder metallurgy (PM) is a term covering a wide range of
ways in which materials or components are made from metal
powders.
 The entire material need not be melted to fuse it.
 Powder metallurgy is also used to make unique materials
impossible to get from melting or forming in other ways.
 A very important product of this type is tungsten carbide
(WC). WC is used to cut and form other metals and is made
from WC particles bonded with cobalt.
 It is very widely used in industry for tools of many types and
globally ~50,000 tonnes/year (t/y) is made by PM.

5.  Powder production.
 Blending or mixing.
 Powder compaction.
 Sintering.
 Finishing Operations.

7.  Blending and mixing (Rotating drums, blade
and screw mixers.
 Pressing - powders are compressed into
desired shape to produce green compact
Accomplished in press using punch-and-die
tooling designed for the part.
 Sintering – green compacts are heated to
bond the particles into a hard, rigid mass.
Performed at temperatures below the melting
point of the metal

8.  In general, producers of metallic powders are not the same
companies as those that make PM parts
 Any metal can be made into powder form
 Three principal methods by which metallic powders are
commercially produced
(i) Atomization (by gas, water, also centrifugal one)
(ii) Chemical
(iii) Electrolytic
 In addition, mechanical methods are occasionally used to
reduce powder sizes

9.  Blending
 Compacting
 Sintering

10.  For successful results in compaction and
sintering , the starting powders must be
homogenized (powder should be blended
and mixed).
 Blending - powders of same chemistry but
possibly different particle sizes are intermingled.
-- Different particle sizes are often blended to reduce
. porosity.
 Mixing - powders of different chemistries are combined .
 PM technology allows mixing various metals into alloys that
would be difficult or impossible to produce by other means.

11.  Press powder into the desired shape and size in dies using a
hydraulic or mechanical press.
 Pressed powder is known as “green compact”.
 Stages of metal powder compaction:

12. Compacting is usually performed at room temperature. Pressures
range from 10 tons per square inch (tons/in2) (138 MPa) to 60
tons/in2 (827 MPa), or more.

14.  Heat treatment to bond the metallic particles, thereby increasing
strength and hardness.
 Usually carried out at between 70% and 90% of the metal's melting
point (absolute scale)
– Generally agreed among researchers that the primary
driving force for sintering is reduction of surface energy.
– Part shrinkage occurs during sintering due to pore size
reduction 12/1/2014 Powder Metallurgy
 Parts are heated to ~80% of melting temperature.

15.  Transforms compacted mechanical bonds to much stronger metal
bonds.
 Many parts are done at this stage. Some will require additional
processing.
Third stage:
Sintered product is cooled in a controlled atmosphere.
– Prevents oxidation and thermal shock.
Gases commonly used for sintering:
--H2, N2, inert gases or vacuum

18.  Precision parts can be produced.
 The production can be fully automated, .
therefore,
 Mass production is possible.
 Production rate is high.
 Over-head costs are low.
 Break even point is not too large.
 Material loss is small.

19.  High tooling and equipment costs.
 Metallic powders are expensive.
 Problems in storing and handling metal powders.
APPLICATIONS:
 Used in the production of gears and other small machine
components.