The effect of microcrystalline cellulose on the mixing and compaction response of ferrous powders

Microcrystalline cellulose has physical and chemical qualities which can prove advantageous for a powder lubricant and binder. Specifically, it possesses good green strength, fine particle size, complete decomposition, cleanliness, i.e. <10 ppm metallic constituents, as well as good mixing response. In an experimental study, lubricant properties, specifically mixing and compaction response of microcrystalline cellulose (Avicel^® PH-105) are evaluated against standard lubricants (Acrawax^® and zinc stearate). Iron and stainless steel powders were compacted over a wide density range, i.e. 70 – 90%, at fixed lubricant additions in each range. Compaction characteristics were measured in order to evaluate the effects of the amount and type of lubricant upon consolidation pressure, ejection pressure, green density and green strength. With regard to mixing, compaction and sintering behavior, microcrystalline cellulose performed comparably to the standard lubricants in most cases. Considering the extreme purity, the material may be used as the prime lubricant in P/M processing particularly when metallic contaminants and decomposition products create processing/property difficulties.