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Powder Blending/Mixing Compacting
Sintering
Powder Metallurgy (P/M)
Particulate Processing of Metals and Ceramics
Powder Metallurgy (P/M)
The Characterization of EngineeringPowders
Production of Metallic Powders Conventional Pressing and Sintering Alternative Pressing and Sintering
Techniques Materials and Products for P/M
Powder Metallurgy (P/M) ?Metal processing technology in which parts
are produced from metallic powders• Usual PM production sequence:
Pressing - powders are compressed into desired shapeto produce green compact• Accomplished in press using punch-and-die
tooling designed for the partSintering – green compacts are heated to bond the
particles into a hard, rigid mass• Performed at temperatures below the melting
point of the metal
Why Powder Metallurgy isImportant ?
• P/M parts can be mass produced to netshape or near net shape, eliminating orreducing the need for subsequentmachining
• P/M process wastes very little material - ~97% of starting powders are converted toproduct
• P/M parts can be made with a specifiedlevel of porosity, to produce porous metalparts– Examples: filters, oil‑impregnated bearings and gears
windshield penetrator sabot stabilizing fin propellant
Kinetic Energy PenetratormaterialsTungsten Heavy Alloy (WHA) Typical composition (wt.%): 90W-7Ni-3Fe Liquid Phase sintered 1500°C melting point of binder alloy (Ni-Fe) ~1465°Crequirements• high density• dimensional precision
Kinetic Energy Armour Piercing Penetrator
Cutting tool inserts
Earlier, high speed steel (HSS) which was manufactured by casting route was used for cutting applications. Such steels are called cutting tool steels. However, they cannot be used by cutting at high speeds wherein the temperature can exceed 600°C. For still higher cutting output, hardmetals or cemented carbides [WC-(6-10 wt.%)Co] is used. Such alloys are consolidated by liquid phase sintering.
P/M Work Materials
• Mostly used for bulk ceramic components• Other P/M metals include copper, nickel,
and refractory metals such asmolybdenum and tungsten
• Metallic carbides such as tungsten carbideare often included within the scope ofpowder metallurgy
Engineering Powders
A powder can be defined as a finely dividedparticulate solid
• Engineering powders include metals andceramics
• Geometric features of engineeringpowders:– Particle size and distribution– Particle shape and internal structure– Surface area
Production of MetallicPowders
• In general, producers of metallic powdersare not the same companies as those thatmake PM parts
• Any metal can be made into powder form• Three principal methods by which metallic
powders are commercially produced1. Atomization2. Chemical3. Electrolytic
• In addition, mechanical methods areoccasionally used to reduce powder sizes
High velocity gas stream flows throughexpansion nozzle, siphoning molten metal frombelow and spraying it into container
Gas Atomization Method