Influence of water vapor on the isothermal oxidation behavior of low pressure plasma sprayed NiCrAlY coating at high temperature

The oxidation of low pressure plasma sprayed (LPPS) NiCrAlY coatings on nickel base superalloy were studied at 1050 °C in flows of O2, and mixture of O2 and 5% H2O under atmospheric pressure. NiCrAlY coating exhibits a very low oxidation rate at 1050 °C in pure O2 and the oxidation kinetics accords with a parabolic law. The oxidation kinetics of NiCrAlY coating obeys almost a linear law after long exposure times in the presence of 5% water vapor. The oxide formed on the surface of LPPS NiCrAlY coating after oxidation at 1050 °C in pure O2 consisted of Al2O3, whereas the oxide formed on the surface of LPPS NiCrAlY coating after oxidation at 1050 °C in a mixture of O2 and 5% H2O is mainly composed of NiCr2O4, NiO, Cr2O3 and Al2O3. It is suggested that the effect of water vapor on the oxidation of the NiCrAlY coating may be attributed to the increase in Ni and Cr ions transport.