HIGH-PERFORMANCE STAINLESS-STEEL VIA POWDER-METALLURGY HOT ISOSTATIC PRESSING

Argon atomised austenitic stainless steel (AISI 304) powder was charac terised for its physical properties such as particle shape, microstruc ture, median particle size, particle size distribution, apparent densi ty, tap density, and flowrate. Subsequently, the tap density of the as received powder was improved to the desired level by adjusting the po wder followed by mixing and blending. This powder was subjected to hot isostatic pressing (hipping) at two different combinations of tempera ture and pressure to optimise the microstructure and mechanical proper ties. Mechanical properties of the stainless steel obtained by the pow der metallurgy (PM) hipping route were found to be superior of those o f conventionally processed wrought steel. The superior performance of PM hipped steel is attributed to its low oxygen content, fine grain si ze, and high degree of chemical homogeneity. Although the production o f billets by the hipping route does not appear to be economical owing tot he high capital cost of the hot isostatic press, the added advanta ge of obtaining a nearnet shape makes the process economically viable for production of intricate shapes. (C) 1997 The Institute of Material s.