Hydrostatic Compaction of Fine Cobalt Powder

Abstract

During the past few decades, a large number of analytical equations have attempted to describe the densification of powders under pressure. A pertinent review of the subject is available in the recent paper published by Chaklader and Bhattacharya.¹ The majority of the empirical relations between the applied pressure and the corresponding green-compact volume (density) has been designed to fit the data obtained by the uniaxial technique of die-pressing, which suffers from serious inconsistencies. The most striking one is the die-wall friction with all of the accompanying anisotropies and inhomogeneities. A great deal of these incongruities, as well as their masking effects, can be avoided by applying the isostatic pressing technique. Basically, the same pressing equations should fit the data obtained from both isostatic and die-pressing experiments. Actually, on the basis of Morgan and Sand’s experiments, Lenel² points out that Heckel’s (or Konopicky’s or Athy’s) equation is the most suitable to describe the phenomenon of isostatic powder densification. According to Mitin,³ a kind of inverse power law equation named after Zhdanowitsch, fairly describes the process. With all the well known limitations of the simple potentional, logarithmic or exponential equations, such a theory does not appear tenable. The goal of this paper is, therefore, to test the interpolating suitability of the empirical pressing equations by treating the experimental data of our own.