Atmosphere control during hot isostatic pressing of capsule free materials

Producing components via powder metallurgy yields a final product with few process steps. In order to get improved mechanical properties, a final compaction using hot isostatic pressing (HIP) is often made. Capsule free HIP can be used for components produced via consolidation processes that yield a closed porosity at the surface, such as additive manufacturing (AM) or press and sinter methods that achieve high density. Without capsule, the compacted material is exposed to the atmosphere during HIP and it is, therefore possible to adjust the surface properties by carburising or nitriding before gas quenching, similar to conventional case hardening processes. The potential of this process has been evaluated in this work. More than 20 different HIP trials have been performed with variations of atmosphere, time, and temperature. Sinter steels and tool steels have been included in the trials. The materials are characterised and evaluated, and thereafter used to optimise this new process