Development of improved metallic materials by coupling SPS and PVD techniques – OEDIPUS

The improvement of the durability properties of metal parts is a major issue for many industrial sectors, such as aeronautics, aerospace, military, etc. To meet this criterion, a fine and homogeneous microstructure is often required. Powder metallurgy techniques, typically pressure-assisted sintering processes as spark plasma sintering (SPS), represent a relevant alternative to more conventional elaboration methods (casting, forging, machining…). Indeed, SPS allows the elaboration in a single stage of high-performance materials and structural elements with high mechanical properties, large dimensions and complex shapes. One of the major problems during SPS is the carbon diffusion from the graphite tooling and/or from the graphite foils inserted between the powder and the mold (punches and die) to the powder. If the sintered part is machined afterwards, the surface carbides can be removed, however the diffusion of carbon at grains boundaries remains an irreversible phenomenon, affecting the durability properties of the material. In this project, a PVD film of a carbide-forming element will be deposited, in a first time, on the graphite foils, in order to reduce or even avoid carbon diffusion. In a second phase, the deposition of a PVD film directly on the graphite tooling will be consider. The approach undertaken in this study will be progressive with, initially, the sintering of pure iron before extending to the sintering of maraging steel powders (M300 family).