Mixing powders for powder metallurgy processing: Incorporating a lubricant
The mixing or blending of powder feedstocks for die pressing of powder metallurgy parts is carried out mainly for adding a lubricant in the main blend.
Popular lubricants are stearic acid, stearin, metallic stearates or other organic compound of a waxy nature. The objectives of adding the lubricant are to reduce friction (and therefore even out density variations) during compaction, to reduce ejection forces and to minimize the tendency for ejection cracking in the compact.
A homogeneous mix is produced from the initial constituents by the tumbling action of Alphie Mixer.
In the special case of cemented carbide materials, mixing is carried out 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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