Compositional effects on the high-temperature oxidation lifetime of MCrAlY type coating alloys

• We report chemical failure during high-temperature oxidation of bond coat alloys.
• The effects of compositional variations on chemical life were detailed.
• Al and Re increased the lifetime by lowering the oxidation rate and Al diffusivity.
• Effects of Re were more pronounced in the Co-rich alloy than the Ni-rich alloy.
• The observed difference is a result of different alloy phases in two alloy systems.

The lifetimes due to chemical failure during high-temperature oxidation of Co and Ni-rich MCrAlY type coating alloys were investigated. They were found to depend critically on the oxidation rate and Al diffusivity in alloy. Re and Al additions increased the life by providing higher β-phase contents and by lowering the Al diffusivity and oxidation rates. The effects of Re were more pronounced in the Co-rich than the Ni-rich alloys. The observed difference was a result of different alloy phases, with a microstructure of γ, β, and σ in the Co-rich alloys and γ, β, and α in the Ni-rich alloys.