Design for Powder Metallurgy - Module 3 Selection of Manufacturing Lecture 6 Notes | EduRev

: Design for Powder Metallurgy - Module 3 Selection of Manufacturing Lecture 6 Notes | EduRev

 Page 1


 
 
 
 
 
 
 
 
Module 
3 
Selection of Manufacturing 
Processes 
Page 2


 
 
 
 
 
 
 
 
Module 
3 
Selection of Manufacturing 
Processes 
 
 
 
 
 
 
 
 
Lecture 
6 
Design for Powder  
Metallurgy 
Page 3


 
 
 
 
 
 
 
 
Module 
3 
Selection of Manufacturing 
Processes 
 
 
 
 
 
 
 
 
Lecture 
6 
Design for Powder  
Metallurgy 
Instructional objectives 
By the end of this lecture, the student will learn the basic principles of Powder Metallurgy 
processes and the critical issues to be considered during design of parts to be manufactured 
using Powder Metallurgy processes/ 
 
Principles of Powder Metallurgy Process 
Powder metallurgy is the process of blending fine powdered materials, compacting the same 
into a desired shape or form inside a mould followed by heating of the compacted powder in 
a controlled atmosphere, referred to as sintering to facilitate the formation of bonding of the 
powder particles to form the final part. Thus, the powder metallurgy process generally 
consists of four basic steps, as indicated in Figure 3.6.1: (1) powder manufacture, (2) 
blending of powders, (3) compacting of powders in a mould or die, and (4) sintering. 
Compacting is generally performed at room temperature and at high pressure. Sintering is 
usually done at elevated temperature and at atmospheric pressure. Often, compacting and 
sintering are combined. Optional secondary processing often follows to obtain special 
properties or enhanced dimensional precision. Powder Metallurgy route is very suitable for 
parts that are required to be manufactured from a single or multiple materials (in powder 
form) with very high strength and melting temperature that pose challenge for the application 
of casting or deformation processes. 
 
 
 
 
 
 
 
 
 
 
 
 
 
Page 4


 
 
 
 
 
 
 
 
Module 
3 
Selection of Manufacturing 
Processes 
 
 
 
 
 
 
 
 
Lecture 
6 
Design for Powder  
Metallurgy 
Instructional objectives 
By the end of this lecture, the student will learn the basic principles of Powder Metallurgy 
processes and the critical issues to be considered during design of parts to be manufactured 
using Powder Metallurgy processes/ 
 
Principles of Powder Metallurgy Process 
Powder metallurgy is the process of blending fine powdered materials, compacting the same 
into a desired shape or form inside a mould followed by heating of the compacted powder in 
a controlled atmosphere, referred to as sintering to facilitate the formation of bonding of the 
powder particles to form the final part. Thus, the powder metallurgy process generally 
consists of four basic steps, as indicated in Figure 3.6.1: (1) powder manufacture, (2) 
blending of powders, (3) compacting of powders in a mould or die, and (4) sintering. 
Compacting is generally performed at room temperature and at high pressure. Sintering is 
usually done at elevated temperature and at atmospheric pressure. Often, compacting and 
sintering are combined. Optional secondary processing often follows to obtain special 
properties or enhanced dimensional precision. Powder Metallurgy route is very suitable for 
parts that are required to be manufactured from a single or multiple materials (in powder 
form) with very high strength and melting temperature that pose challenge for the application 
of casting or deformation processes. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 3.6.1 Basic steps in Powder Metallurgy process [3] 
Page 5


 
 
 
 
 
 
 
 
Module 
3 
Selection of Manufacturing 
Processes 
 
 
 
 
 
 
 
 
Lecture 
6 
Design for Powder  
Metallurgy 
Instructional objectives 
By the end of this lecture, the student will learn the basic principles of Powder Metallurgy 
processes and the critical issues to be considered during design of parts to be manufactured 
using Powder Metallurgy processes/ 
 
Principles of Powder Metallurgy Process 
Powder metallurgy is the process of blending fine powdered materials, compacting the same 
into a desired shape or form inside a mould followed by heating of the compacted powder in 
a controlled atmosphere, referred to as sintering to facilitate the formation of bonding of the 
powder particles to form the final part. Thus, the powder metallurgy process generally 
consists of four basic steps, as indicated in Figure 3.6.1: (1) powder manufacture, (2) 
blending of powders, (3) compacting of powders in a mould or die, and (4) sintering. 
Compacting is generally performed at room temperature and at high pressure. Sintering is 
usually done at elevated temperature and at atmospheric pressure. Often, compacting and 
sintering are combined. Optional secondary processing often follows to obtain special 
properties or enhanced dimensional precision. Powder Metallurgy route is very suitable for 
parts that are required to be manufactured from a single or multiple materials (in powder 
form) with very high strength and melting temperature that pose challenge for the application 
of casting or deformation processes. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 3.6.1 Basic steps in Powder Metallurgy process [3] 
Powder Manufacture 
The manufacturing of the material powder is the first step in powder metallurgy processing 
route that It involves making, characterising, and treating the powder which have a strong 
influence on the quality of the end product. Different techniques of powder making are: 
Atomising Process 
In this process the molten metal is forced through an orifice into a stream of high velocity air, 
steam or inert gas [Figure 3.6.2]. This causes rapid cooling and disintegration into very fine 
powder particles and the use of this process is limited to metals with relatively low melting 
point. 
Gaseous Reduction  
This process consists of grinding the metallic oxides to a fine state and subsequently, 
reducing it by hydrogen or carbon monoxide. This method is employed for metals such as 
iron, tungsten, copper, etc. 
Electrolysis Process 
In this process the conditions of electrode position are controlled in such a way that a soft 
spongy deposit is formed, which is subsequently pulverised to form the metallic powder. The 
particle size can be varied over a wide range by varying the electrolyte compositions and the 
electrical parameters. 
Carbonyl Process 
This process is based upon the fact that a number of metals can react with carbon monoxide 
to form carbonyls such as iron carbonyl can be made by passing carbon monoxide over 
heated iron at 50 – 200 bar pressure. The resulting carbonyl is then decomposed by heating it 
to a temperature of 200 – 300
0
Stamp and Ball mills  
C yielding powder of high purity, however, at higher cost. 
These are mechanical methods which produce a relatively coarse powder. Ball mill is 
employed for brittle materials whereas stamps are used for ductile material. 
Granulation Process  
This process consists in the formation of an oxide film in individual particles when a bath of 
metal is stirred in contact with air. 
Mechanical Alloying 
In this method, powders of two or more pure metals are mixed in a ball mill. Under the 
impact of the hard balls, the powders are repeatedly fractured and welded together by 
forming alloy under diffusion. 
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