High Temperature Corrosion Behavior of Ni-Cr-Co Base Superalloy in Air with Water Vapor

By means of TGA, SEM (EDX) and XRD, the high temperature corrosion behavior of Ni-Cr-Co base superalloy was studied at 750 ℃ and 775 ℃ in air with water vapor. The results indicate that the kinetic curve of the alloy oxidized at 750 ℃ for 2480 h in air with 10% water vapor obeys a parabolic law at the initial oxidation stage and then follows a linear law. The oxide scale mainly consists of Cr₂O₃ and the internal oxides, Al₂O₃ and TiO₂, also precipitate in matrix. The protective oxide scale of the alloy oxidized at 775 ℃ for 432 h in air with 5% water vapor is composed of Cr₂O₃, TiO₂ and CoCr₂O₄ and the internal oxides are Al₂O₃ and TiO₂. The corrosion speed is quickened because of the presence of water vapor. The corrosion procedure is decided by the transmission of the elements through the oxide scale.