19.10.2004 Pressing & Sintering

Lubricant Distribution on Compacts and Tool Walls after P/M Compaction

PM2004, in Vienna, Austria. Authors: Erik Hjortsberg, L. Nyborg, Hilmar Vidarsson. The use and effect of lubricants during compaction and ejection of metal powder has for a long time been studied from a macro perspective, assessing effects of different factors but ignoring the actual mechanisms through which they operate. Here, the intention is to explain the physical interaction between the metal powder, lubricant and tool wall on a microscopic level. With the development of a new compaction tool, the use of X-ray photoelectron spectroscopy and ion sputtering, it has been established that, for iron powder samples containing 0.5-3 wt% ethylene bis-stearamide, compressed with 400-800 MPa, both the compact surface and the tool wall are to a large extent covered by a film of monomolecular thickness. Through interference microscopy, the volume of pores at the surface of the compact have been determined to 0.4 (µm)³/(µm)². Several conclusions that deepen the understanding of the functionality of lubricants have been drawn from these observations.