High temperature oxidation behavior of cast Ni-based superalloy K444

In order to identify the high-temperature oxidation perfromance of cast nickel-base superalloy K444 used as gas turbine blade material, the isothermal oxidation kinetic and oxidation mechanism of the K444 alloy at 800°C and 850°C were investigated. X-ray diffractometer, scanning electron microscope and energy dispersive spectrdmeter were used to analyze the oxidation products as well as the morphology and composition of oxide on cast nickel-base superalloy K444. The results show that the oxidation kinetic curves of the alloy at 800°C and 850°C obey the parabolic law, and almost no oxide spallation is observed. The oxide scale mainly consists of Cr2O3 with small amount of NiCr2O4 and TiO2, and has the multilayer structure. The outmost thin layer is porous and mainly contains non-protective TiO2. The protective Cr2O3 layer with a certain amount of NiCr2O4 and TiO2 is the main layer of the scale. The internal oxide layer is mainly composed of Al2O3.