This PPT contains information about basic operations of Powder Metallurgy(PM). it is consist of manufacturing techniques of powder, and manufacturing of products by the powder.
2. The basic operation of powder
metallurgy techniques
• The four basic operations of the powder metallurgy are:
1.Manufacture of powder
2.Mixing or blending powder particles
3.Compacting
4.Sintering
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3. Summarized steps of power
metallurgy
• Obtaining metal powder of required fineness and purity
• Subjecting these particles to a sufficiently high pressure in a
die using a press to achieve cohesion among them
• Sintering these compacted mass at a temperature high
enough to diffuse particles & cause inter-granular grain
growth to form a single solid.
• Taking out solid component & applying the secondary
operations such as finishing, sizing & finally inspecting the
component.
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4. Manufacture of Powder
Metallurgy
• The size of powder particles normally ranges
from 1-100 µm, preferably 10-20 µm.
• The processes:
1.Mechanical Process
2.Atomization
3.Electrolytic Deposition
4.Reduction
5.Hydride & Carbonyl Process
6.Condensation of Metal Powder
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5. Methods For Manufacturing of
Metal Powder
• Mechanical Processes:
• In mechanical processes, crushing or milling takes place.
• This method is used for brittle metals/alloys like tungsten
carbide, iron oxide, Sb, Bi etc.
• Atomization:
• In atomization process, the molten metal is disintegrated
in fine particles by using high pressure jets of air, water,
inert gases and it is divided in particles being collected in
collector.
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7. Methods For Manufacturing
of Metal Powder
• Electric Deposition:
• This is method works on the principle of electrolysis and
mainly used to produce powder of copper.
• In this method the anode of copper and the cathode of
aluminum are immersed in electrolyte of copper
sulphate(acidic solution).
• Reduction:
• Reduction method involves reduction of metals usually in
their oxide compound.
• These compounds are heated with reducing agents such as
Carbon, Coal, CO, H2 etc.
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9. Methods For Manufacturing
of Metal Powder
• Hydride and Carbonyl Process:
• Some metals such as tantalum, niobium etc, gets reacted
with hydrogen and makes hydrides that are stable ate
room temperature.
• These hydrides dissociates at 350°C in hydrogen and pure
metal.
• Similarly many metals makes carbonyl compounds. at
suitable temperature and pressure they get dissociated
and gives us the pure metal.
• Condensation:
• This method is used for the metals such as zinc, cadmium,
magnesium etc. that are boiled and their vapour can be
condensed to achieve their powder form.
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10. Mixing & Blending of
Powders
• Mixing:
• The powder is mixed well to produce uniform distribution
of powder, particularly when the size of powders is
different.
• In wet mixing the better mixing of powders, water or
solvent is used for reduction of dust, reduction of chances
of exploration and hazardous side effects and to prevent it
from getting oxidized.
• Blending:
• Blending is the operation to add lubricant and volatizing
agents and then thoroughly mixing of the powder.
• The lubricants used are basically the metallic separators
such as zinc separate, graphite, oil, glycerin, paraffin etc.
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12. Powder Compaction
• Compacting techniques are generally of 2 types:
A.Pressure techniques:
• This includes die pressing, roll pressing, extrusion
methods, forging method and vibratory compaction.
A.Non Pressure Techniques:
• This includes slip casting, continuous and gravity
methods.
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15. Sintering
• After compacting of the metal powder, the mass
obtained is called “Green Compact” or “Briquette”.
• To achieve the final finished product, Sintering must be
done. Sintering is applied to obtain the all possible final
strength and hardness that is needed.
• The sintering process is consist of heating the Green
compact in a furnace to a temperature below it’s melting
point. The heating takes place in reducing atmosphere.
• Sintering is essentially a process of bending particles by
atomic diffusion.
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16. Sintering
• The Diffusion of atoms takes place at the boundaries of
the atoms that are connected to another atom. At the
boundaries of atom, while diffusion, the atoms are getting
connected and sequentially grain boundaries are also
diffused.
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17. Sintering
• There are basically 2 types of sintering:
1.Solid Phase Sintering:
• In this process the sintering takes place across the cold
welded surfaces that are adjacent to each-other.
1.Liquid Phase Sintering:
• In this process, the melt of one metal is penetrated
through another metal, thus alloying results in a
continuous bonds between those two metals. 17
