Powder metallurgy

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Name some of the reasons for the commercial importance of powder metallurgy technology.
Because parts can be made to net or near net shape, parts can be made with a controlled level of porosity certain metals that can't be processed can be processed by PM. Low waste.
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What are some of the disadvantages of PM methods?
High tooling costs, metal powders are expensive, difficulties in handling and storing powders, variations in density can be troublesome
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What are the three principal methods used to produce metallic powders?
Atomisation, the conversion of molten metals into droplets which solidify into powders. Chemical reactions using reducing agents to that combine with oxygen to create powders. Electrolysis deposits particles of metal onto the cathode
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What are the different atomization techniques in powder production?
Gas atomisation, where molten metal is drawn through a siphon and sprayed by a gas jet, or where the molten metal flows into a gas jet stream. Water atomisation where it flows into a water jet. Centrifugal, where it falls onto a rotating disk.
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Which is the most common atomization technique? What are its advantages/disadvantages?
Water atomisation. It can be cooled rapidly, and water velocity is related to powder particle size.Causes oxidation in ferrous powders, synthetic oils may be used
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What are the three basic steps in the conventional powder metallurgy shaping process?
Blending/mixing, pressing, sintering
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What is the technical difference between blending and mixing in powder metallurgy?
Blending is combining particles of the same chemistry but different sizes, mixing means combining metal powders of different chemistry
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What is meant by the term “green” compact?
Pressed but not yet sintered PM part
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Describe what happens to the individual particles during compaction.
Particles are first repacked into an efficient arrangement, then deformation of the particles as pressure increases
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What are the three steps in the sintering cycle in PM?
Preheat where lubricants are burned off, sintering and Cool down
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Why might porosity in the final part be an advantage or disadvantage?
It can be used for self-lubritcating parts, but is lower strength than 100% dense part, water permeation cause oxidation
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What is the difference between impregnation and infiltration in PM?
Impregnation is when an oil or fluid is permitted into the pores of a sintered Pm part, Infiltration is where the pores of the pm part are filled with a molten metal with a lower melting point than the PM part
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What are the two basic classes of metal powders as far as chemistry is concerned?
Elemental powders which are pure powders. Pre-alloyed powders, powders of alloy
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Why is PM technology so well suited to the production of gears and bearings?
The geometries lend themselves to conventional PM pressing. The porosity allows impregnation
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Other cards in this set

Card 2

Front

What are some of the disadvantages of PM methods?

Back

High tooling costs, metal powders are expensive, difficulties in handling and storing powders, variations in density can be troublesome

Card 3

Front

What are the three principal methods used to produce metallic powders?

Back

Preview of the front of card 3

Card 4

Front

What are the different atomization techniques in powder production?

Back

Preview of the front of card 4

Card 5

Front

Which is the most common atomization technique? What are its advantages/disadvantages?

Back

Preview of the front of card 5
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