High temperature corrosion behaviour of nickel aluminides: effects of chromium and zirconium

The high temperature corrosion behaviour of nickel aluminide Ni3Al containi ng up to 8 mass % chromium and up to 0.9 mass % zirconium has been investig ated in air and in carburizing, chlorinating and sulphidizing process gases . It was found that undoped Ni3Al shows excellent resistance in air, in car burizing gases and in chlorinating/oxidizing atmospheres, while its corrosi on resistance in oxygen-deficient chlorinating gas atmospheres and in sulph idising atmospheres is poor. Additions of zirconium have a strong impact on the corrosion behaviour, they prevent evaporation of volatile aluminium ch lorides in oxygen-deficient chlorinating environments but they increase the oxidation rate in air and in chlorinating environments. Unlike zirconium, chromium has only a small effect on the corrosion behaviour of Ni3Al. (C) 1 999 Elsevier Science Ltd. All rights reserved.