Chromium Deposition on Cobalt-Based Alloys by Pack-Cementation and Behaviour of the Coated Alloys in High Temperature Oxidation

摘要: Two TaC-strengthened cobalt-based alloys, with compositions Co-10Cr-0.25C-4.4Ta and Co-10Cr-0.5C-8.7Ta (wt.%) underwent Cr-deposition by pack-cementation, followed heat-treatment to allow Cr diffusing deeper in their sub-surface. Thereafter they were tested for 50 hours at 1200°C a thermobalance. These alloys successfully enriched chromium, maximal content on surface of about 30wt.% depth enrichment several hundreds micrometers. This allowed chromia-forming behavior the cemented despite 10wt.%Cr bulk. was especially true {C,Ta}-richest alloy oxidation kinetic which wholly parabolic analogous Ni-30Cr known its good 1200°C. The constants chromia-volatilization same levels ones. However, chromium step, diffusion following cementation, causes fragmentation fraction reduction tantalum carbides strengthen alloy.