Influence of Solution Nitriding of Supersolidus–Sintered Cold Work Tool Steels on their Hardenability

Abstract Powder metallurgical steel grades offer higher quality and performance compared to cast and forged steel grades due to their finer microstructure without segregations or textures. Because high-alloyed, cold work tool steels cannot be compacted by solid-state sintering, hot isostatic pressing is state of the art. This process, however, is comparatively expensive and there is thus a high demand for alternative densification processes. Supersolidus liquid-phase sintering represents an alternative to hot isostatic pressing for densification of these steels to theoretical density. During sintering, the steel powder interacts with the sintering atmosphere, which can be a vacuum, hydrogen, hydrogen plus nitrogen, or nitrogen. In a nitrogen atmosphere, there may be nitrogen uptake by the sintered material, which changes the chemical composition of the steel and thus results in a decrease in the sintering temperature. The aim of this work is to investigate the influence of nitrogen uptake on the hardenabi...