Mixing Powders for PM Processing

The mixing, or blending, of powder feedstocks for die pressing of Powder Metallurgy parts is carried out for two reasons:

To introduce alloying element additions in a homogeneous form

Die pressing feedstocks generally consist of elemental mixes in order to maintain as high a level of compressibility as possible. Using this approach means that the compressibility is controlled by that of the soft, annealed base powder (most commonly iron). Use of a fully pre-alloyed powder would mean that the initial particle hardness and work hardening rate would both be increased by the alloying additions and compressibility therefore reduced.

To incorporate a pressing lubricant

Popular lubricants are stearic acid, stearin, metallic stearates or other organic compound of a waxy nature. The purposes of adding the lubricant are to reduce friction (and therefore even out density variations) during compaction, to reduce ejection forces and to minimise the tendency for ejection cracking in the compact.

A homogeneous mix is generally produced from the initial constituents by a tumbling action in an appropriate mixing vessel. Mixing vessels are often of a double-cone geometry, but other vessel shapes are also utilised (V, W or Y-shaped sections).

In the special case of cemented carbide materials, mixing is carried out in a ball mill, in order to coat the individual carbide particles with the binder metal (e.g. cobalt). As the very fine powder particles involved have poor flow characteristics, the mixture is subsequently granulated to form agglomerates.

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Extensive Powder Metallurgy industry news coverage, and the following exclusive deep-dive articles and reports:

  • Burgess-Norton and Amsted Automotive: How a legacy automotive supplier is growing with, not despite, electrification
  • Meeting sustainability demands in PM: High-temperature sintering of nickel- and copper-free powder mixtures for low alloyed PM parts
  • World PM2022: An overview of the status and trends in the global PM industry
  • A novel approach for the production of metal powders with tailored chemical compositions: Amazemet’s rePowder
  • Productivity, flexibility, reliability: SACMI’s new press technologies for the changing PM industry
  • Understanding the thermal properties of metal powders: Characterisation of powders using the Hot Disk technique
  • World PM2022: Views on the potential of Field Assisted Sintering for advanced materials

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