Oxidation behavior of a single-crystal Ni-based superalloy over the temperature range of 850 °C-950 °C in air

The oxidation behavior of a single-crystal Ni-based superalloy over the temperature range of 850 degrees C-950 degrees C and under R-a= 0.1-0.2 mu m was investigated. The oxidation kinetics of the superalloy presented two stages. The first and second stages had activation energies of 222 and 263 KJ.mol(-1), respectively. The oxide film comprised NiO, NiCr2O4, CrTaO4, and Al2O3. The formation time of the continuous Al2O3 layer corresponded to the transition point of oxidation kinetics at each temperature. Mass gain in the first stage could be attributed to the formation of an outer NiO layer and an inner alumina layer, whereas that in the second stage could be ascribed to the growth of intermediate spinel layers.