Atmosphere control during hot isostatic pressing of capsule-free materials

Producing components via powder yields a final product with few process steps. In order to get improved mechanical properties, final consolidation using hot isostatic pressing (HIP) is often performed. In this work, the aim is to include atmosphere control for HIP of capsule-free materials, e.g., additively manufactured components or conventionally pressed and sintered materials. Atmosphere control is applied for various purposes, such as carburising, e.g., traditional case hardening, or introducing an inert furnace atmosphere for HIP of sensitive materials. Carburisation experiments have been performed in a HIP-unit using methane as carbon source. The material response has been evaluated based on varying ratios of methane, time for carburising, ingoing densities, and alloy composition. The results show that porosity has a strong influence on carbon uptake, and lower density yields more carbon. As expected, a strong relation between added methane content and carbon uptake is also seen. Carburisation times of a few minutes gave little effect, however, 60 minutes gave approximately 500µm carburisation depth.