Oxidation behavior of a low-cost second-generation Ni-based single crystal superalloy at 900 °C and 1000 °C
Haitao Fu, Wenchao Yang, Qiang Wang, Chen Liu, Jiarun Qin, Yuzhang Lu, Jian Shen, Haijun Su, Lin Liu
Abstract
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 Al 2 O 3 . 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.