2. Atomization process involves use of high
pressure fluid jets to break up a molten metal
stream into very fine droplets, which when
solidify into fine particles .
Method was used on large scale during world
war II .
High quality powders of Al ,brass ,iron , SS
,tool steel and super alloys are produced by
the above method .
3. Water atomization
Gas atomization
Vacuum atomization
Centrifugal atomization
Rotating disk atomization
Ultrasonic atomization
4. This method uses high pressure water jets to
dis-integrate the molten metal stream .
Water is used due to their higher viscosity
and superior quenching ability .
The process is in-expensive and can be used
both for small and large scale production .
Metals and alloys which do not react
chemically with water cant be atomized by
this process .
5. Molten metal stream is dis-integrated by
means of high velocity gas in this method .
The gases used are Ar , N2 ,He gas jets .
The atomized powder are collected in water
bath .
Fluidized bed cooling is used when certain
characteristics of powder are desirable for
example, spherical shape or particles with
little or no oxide(surface) content .
This process is costier than water atomization
6. When molten metal supersaturated with gas
,under pressure is suddenly exposed to
vacuum the outcoming gas of metal solution
expands rapidly causing atomization of metal
stream .
High purity powders obtained by this
method.
Metal is saturated with H2 gas .
7. This method uses centrifugal force to break
off molten metal drops from molten end of
consumable electrode .
Method is used to produce powders of
reactive metals of metal like titanium .
In this process one end of the metal bar is
heated and melted by bringing it into contact
with non consumable tungsten electrode
, while rotating it longitudinally at high
speeds.
8. Centrifugal force cause the metal droplets to
be thrown off outwards , which when solidify
as spherical shaped particles inside an
evacuated chamber .
9. this process involves the impinging of stream
of molten metal on the surafce of rapidly
spinning disk ,which results in mechanical
atomization of metal stream and causes the
droplets to be thrown off the edges of disk .
Particles formed are generally spherical and
their sizes decrease with increasing disk
speed .
Use of vacuum /inert gas is mandatory
because of purity requirements .
10. This method involves use of ultrasonic waves
to produce fine powders from a molten
stream of metals .
11. 1. Melting and superheating facility
2. Atomization chamber
3. Powder collection tank
12. Standard melting furnaces are used to
produce the liquid metal . This is usually
accomplished by air melting, Inert gas or
vacuum induction melting .
Complex alloys which are highly susceptible
to contamination ( like Ni base super alloys)
are usually melted in vacuum induction
furnaces .
Metal from furnace transferred to tundish (
reservoir ) .
13. Consists of atomizing nozzles system located
at base of tundish , which controls shape and
size of molten metal stream .
The high velocity atomization medium
breaks up the molten stream into fine
droplets , which cool and solidfy as they
settle at bottom of atomization chamber.
Inert gas like N2can be purged into tank to
minimize oxidation of resulting powder .
14. 2 ways – dry collection and wet collection .
Dry collection : in this particles solidfy before
they reach the bottom of tank .The collection
tank should have sufficient height to ensure
complete solidification of particles before
they fall to bottom .
Wet collection : powder is collected in water
tank provided at bottom of atomization unit
.the tank may be externally cooled .
15. Function of atomization nozzle is to control
the flow and pattern of atomizing medium to
provide for efficient dis integration of
powders .
For a given nozzle design , the average
particle size is controlled by
1.pressure of atomizing medium
2. Apex angle between the axes of gas jets .
16. Higher apex angle lead to smaller particle size
Nozzle design controls the efficiency of dis
integration which decides the final characteristics of
powder .
Apex angle for water atomization is less than that of
gas .
Nozzles used in atomization process(both water
and gas ) are either annulart type or jet type .
17. Selection of medium mainly on reactivity of
the metal and cost of medium .
Water and air are inexpensive but they react
with many molten metals .
Inert gases are useful but expensive .
N2, Ar, He are inert gases are used to prevent
contamination .
Synthetic oils are used as atomization
medium in place of water or gas .
18. Oil atomization is used to produce powders
of high carbon steel , high speed steels
, bearing steels .
19. 1. Pressure of metal head .
2. Pressure of atomizing medium .
3. Metal temperature .
4. Orifice area
5. Molten metal properties .
20. Processing capability : almost all metals
that can be melted can be atomized .
Freedom to alloy : higher purity and pre-
alloyed powders can be prepared directly
from melt .
Cleanliness : powders can be produced with
few or nil non-metallic inclusions .
Versatility : particle shape and size is possible
to control by processing parameters such as
21. Metal temperature and pressure of atomizing
medium .
• Productivity : higher productivity with lower
cost of equipment as compared to many
other methods .
