Oxidation behavior of a low-cost second-generation Ni-based single crystal superalloy at 900 °C and 1000 °C

The temperature dependence on the oxide layer and the oxidation mechanism was systematically investigated at 900 °C and 1000 °C in a low-cost second-generation Ni-based single crystal superalloy. The oxidation kinetics could be divided into three stages. The initial stage followed a parabolic law with an activation energy of 60.08 kJ mol⁻¹. A linear law was observed in the second stage due to the formation of Al₂O₃. However, the last stage showed different trends, following an almost flat linear law at 900 °C, while an abnormal increase was observed at 1000 °C. The difference was attributed to the rapid growth of intermediate layer at 1000 °C, while the slight increase at 900 °C resulted in higher growth stress at 1000 °C. Meanwhile, the thermal stress was generated during the cooling process of specimens, which promoted the spallation of the oxide layer. As a result, the spallation of the oxide layer was more severe at 1000 °C, causing the abnormal increase of oxidation kinetics at this stage.