MICROSTRUCTURAL CHARACTERISATION OF HSS DENSIFIED BY HOT ISOSTATIC PRESSING AS A FUNCTION OF THE PROCESS VARIABLES

摘要

Water atomised T42 HSS powders with two different particle sizes have been densified by Hot Isostatic Pressing (HIPing) with and without carbon additions. Green compacts have been encapsulated and several combinations of time and temperature were carried out in order to study the evolution of the microstructure with those parameters. Mean austenite grain size as well as type, size and volume fraction of carbides have been measured by quantitative metallography on fully dense specimens, In contrast to the standard temperature used in the industry (1100℃) for HIP of HSS, a temperature as low as 850℃ was successfully used here to obtain a fully dense material. The heat treatment behaviour of these steels is analysed. A comparison between the microstructure of the steels developed in the present work and a commercial HIPed HSS grade made from gas atomised powders is also reported.