Oxidation behavior of a single-crystal Ni-base superalloy in air at 900 and 1050 °C

The high temperature oxidation behavior of the single-crystal Ni-base superalloy with higher Cr contents was investigated at 900 and 1050 degrees C in air by using SEM, XRD, and SEM/EDAX. The results show that the mass gain rapidly increases in the initial stage of oxidation at high temperature, and the oxidizing process is mainly controlled by the formation of Cr2O3 and Al2O3 phases. The obvious process of the surface oxidation, internal oxidation and internal nitridation in the alloy occurs during oxidation at high temperature. And the poor-aluminum but rich-tantalum areas appear above the internal oxides layer. The phase containg Ta-richer may restrain the element Al in the matrix diffusing outward, which restrains the growth up of the oxide scales.