Protection of cobalt-based refractory alloys by chromium deposition on surface

► Chromium deposits by pack-cementation were tested for cast low-Cr cobalt-base alloys. ► The chromium carbides of the Co-10Cr-C alloys led to unwanted outer carbide layer. ► The surfaces of the Co-10Cr and Co-10Cr-Ta-C alloys were really enriched in chromium. ► The TaC carbides facilitate inward diffusion of chromium during diffusion treatment. ► Only the alloys without Cr-carbides can be really enriched in Cr by pack-cementation.