How P/M Parts are Made

The three basic steps for producing conventional density parts by the powder metallurgy process are Mixing, Compacting, and Sintering. A brief explanation of each step follows:

Step One: Mixing

  • Elemental or prealloyed metal powders are first mixed with lubricants or other alloy additions to produce a homogeneous mixture of ingredients.
  • The initial mixing may be done by either the metal powder producer or the P/M parts manufacturer.

Step Two: Compacting

  • A controlled amount of mixed powder is automatically gravity-fed into a precision die and is compacted, usually at room temperature. Normally, compacting pressures in the range of 30 - 50 tons per square inch are used.
  • Compacting the loose powder produces a "green compact" which, with conventional pressing techniques, has the size and shape of the finished part when ejected from the die, and sufficient strength for in-process handling and transporting to a sintering furnace. Typical compacting techniques use rigid dies set into special mechanical or hydraulic presses.

Step Three: Sintering

  • In the typical sintering step, the green compact is placed on a wide-mesh belt and slowly moved through a controlled atmosphere furnace. The parts are heated to below the melting point of the base metal, held at the sintering temperature, and then cooled.
  • Basically a solid state process, sintering transforms compacted mechanical bonds between the powder particles to metallurgical bonds. This provides the P/M part's primary functional properties.
  • P/M parts are generally ready for use after sintering. However, to provide special properties, the parts can be repressed, impregnated, machined, tumbled, plated, heat treated, or welded.
 pm1  pm2  pm3

 Mixing

Compacting

 Sintering