OXIDATION RESISTANCE AND MICROSTRUCTURE OF Pt AND PtIr DIFFUSION COATINGS ON Ni BASED SINGLE CRYSTAL SUPERALLOYS BY ELECTROPLATING METHOD

Abstract

Blades and vanes for gas turbines, usually made of Ni-based superalloys, are exposed at very high temperature in severe oxidation and corrosion environments. Nowadays, thermal barrier coating systems (TBCs) have been applied to protect them against such severe working conditions. In this study, Pt and PtIr diffusion coatings on Ni based single crystal superalloys were fabricated by an electroplating method followed by an annealing heat treatment process. The microstructure and phase constitution of the coatings were studied by SEM/EDS and XRD methods. The cyclic oxidation test at 1150 o C was conducted to investigate the oxidation resistance of the coatings. The results showed that the addition of Ir in the coating led to the formation of α(NiPt 2 Al) phase and reduced the formation of Kirkendall voids in the coating after 100 cycle oxidation test.