Powder Metallurgy


Reading Assignment

  • 18.1 Introduction to PM
  • 18.2 Process Basics
  • 18.3 Powder Manufacture
  • 18.6 Mixing and Blending
  • 18.7 Compacting
  • 18.8 Sintering
  • 18.9 HIP
  • 18.11 MIM
  • 18.11 Secondary Operations
  • 18.14 Design Considerations

Recommended Reading



The Process

Powder metallurgy is the process of producing components from metal powders. The process is outlined below. Please see the links to the Metal Powder Industries Federation.

Advantages of PM

  • Eliminates or minimizes machining by producing parts at, or close to, final dimensions
  • Eliminates of minimizes scrap losses by typically using more than 97% of the starting raw material in the finished part
  • Permits a wide variety of alloy systems
  • Produces good surface finishes
  • Provides materials which may be heat treated for increased strength or increased wear resistance
  • Provides controlled porosity for self lubrication or filtration
  • Facilitates manufacture of complex or unique shapes which would be impractical or impossible with other metalworking processes
  • Is suited to moderate- to high-volume component production requirements
  • Offers long-term performance reliability in critical applications
  • Is cost effective

Raw Materials Production

  • Elemental or Alloy Metal Powders
  • Additives (graphite, die lubricants)


  • Hot Compaction
    • Isostatic
    • Extrusion
    • Spraying
    • Pressureless sintering
  • Warm Compaction
    • Die Compacting
    • Injection Molding
  • Cold Compaction
    • Die Compacting
    • Isostatic
    • Rolling
    • Injection Molding
    • Slip Casting
    • Cold Forming
  • Sintering
    • Atmosphere
    • Vacuum
  • Optional Secondary Processing
    • Repressing
      • Coining
      • Sizing
    • Resintering
    • Forging
    • Rerolling
    • Metal Infiltration
  • Optional Finishing Steps
    • Machining
    • Heat treating
    • Steam Treating
    • Plastic Impregnation
    • Plating
    • Tumbling
    • Oil Impregnation
    • Shot Peening

Methods of Making Metallic Powders

(See details here from mpif.org)

  • Solid-State Reduction

Reduction is oxidation in reverse common for iron powder
Results in “sponge iron” that is then crushed

  • Electrolytic deposition

same as electroplating
Copper and Iron Powders

  • Atomization

Melted metal sprayed with high pressure steam or liquid
breaks up into small particles

  • Chemical

Usually this process involves precipitating the metal powder out of a chemical solution.


  • Mixes Particles of different sizes to produce uniform particle distribution

May be wet or dry, wet reduces chances of Explosion

  • Mixes powders of different metals
  • Adds lubricants such as

powdered graphite
stearic acid
lithium stearate


  • Pressing or Briqueting
  • Extrusion (bars, hex shapes, etc.)
  • Rolling (Sheets and plates)
  • Slip Casting
  • Centrifugal Casting (for heavy powders, tungsten carbide)
  • High Energy Rate Compacting
  • Isostatic Forming (rubber mold, pressurized chamber)




  • Heating green parts to 60-80% or melting point
    • Increases atomic bonds
    • grain boundaries are formed
    • density is increased
    • mechanical properties are increased
  • Usually done in a controlled atmosphere furnace

Secondary Processes

  • Infiltration

Copper, brass etc. blank placed under a part
Melts cu, brass, etc. but not iron
capillary action draws brass into iron

  • Impregnation

introduces oil etc, into porous bronze or iron bearings.
vacuum tank may be used
also used to seal pores with solder or plastic resins

  • Sizing and Coining

to increase dimensional accuracy
increase density
improve surface finish

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