mechanical engineering project

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.