Effect of Compaction Temperature on the Lubricant Distribution in Powder Metal Parts

Warm compaction is a process leading to parts with high green strength and density. An increased compacting temperature lowers the flow stress of the metallic particles and increases their ductility, resulting in higher powder compressibility and stronger interparticles bonding, either mechanical or metallurgical. Although many studies have been published on warm compaction, very few investigated the influence of compaction temperature on the behavior of the lubricants. In most cases, the choice of a lubricant for warm compaction relies only on the experimental evaluation of the compressibility and of the ejection performance of the selected metal/lubricant system. An investigation was carried out to characterize the behavior of the lubricant during the compaction of water-atomized iron powder mixes at 25 and 150°C. Using techniques such as SEM, WDS and SIMS, the microstructure of the compacts and the distribution of the lubricant within the parts were characterized for mixes containing different lubricants (LiSt and EBS). The results were related to the properties of the iron powders and lubricant during the compaction of the parts.