Isothermal Oxidation Behavior Characteristics of a Second Generation Ni-base Single Crystal Superalloy in Air at 1000 and 1100°C

The isothermal oxidation behavior of a second generation Ni-base single crystal superalloy was investigated in air at 1000 degrees C and 1100 degrees C. The microstructures of the oxide morphology and the cross-section area of the specimens after oxidation were analyzed by XRD and SEM/EDX. Indeed, the present results indicated that the Ni-base single crystal superalloy denoted the parabolic oxidation kinetics, which are primarily controlled by the growth of the inner alpha-Al2O3 layer. In conclusion, the scales formed on the surface of superalloy both at 1000 degrees C and 1100 degrees C were complex and can be classified into three different layers in general: an outer layer of NiO with a small amount of CoO, an intermediate layer which predominantly composed of spinels (Ni,Co) Al2O4, NiCr2O4, and accompanied with some other oxides such as CrTaO4, NiTiO3 as well as W20O58, and an inner continuous layer of alpha-Al2O3. Nevertheless, the poor Al zone was appeared between the oxide scales and the substrate after oxidation 200 h and 500 h both at 1000 degrees C and 1100 degrees C.