Hot Pressing: Technology and Theory

Abstract

This chapter describes the technology and theory of hot pressing method. Hot pressing is the densification of a loosely packed powder or a compacted preform by the simultaneous application of heat and pressure. The specific benefits of hot pressing are seen in terms of the achievement of high final density and microstructural improvement such as fine grain size. Hot pressing procedures include simple linear hot pressing, continuous pressing, and hot isostatic pressing. The main disadvantages of the process are its high cost and its limited capacity to fabricate a variety of shapes at mass-production rates. The most successful approach to the modeling of hot pressing has been to use creep models suitably modified to account for the effects of porosity and external pressure. The ideal powder for hot pressing should contain no agglomerates, have a narrow particle size distribution, and a fine particle size for promoting rapid densification. It is found that the actual pressing conditions are determined largely by the powder sinterability and the desire to form a particular microstructure.