Hot isostatically pressed tool steels: microstructure

This chapter discusses the microstructure of high alloy tool steels. The microstructure of high alloy tool steels is mainly affected by the alloying constituents, the way of manufacturing and hot working and the heat treatment. In powder metallurgical (PM) versions, the powder particle size, the highest processing temperature and the degree of deformation play a major role. The nital etched microstructure of a fully heat treated high speed steel from different manufacturing routes is compared at identical nominal composition and similar dimensions. The effect of heat treatment is illustrated for the same steel in a hot isostatic pressing (HIP) plus hot worked condition. Microstructural anisotropy in hot worked HIP tool steels is also illustrated.