The competitive oxidation behavior of Ni-based superalloy GH4738 at extreme temperature

Higher thrust-to-weight ratio poses challenges for the high-temperature performance of Ni-based superalloys. The oxidation behavior of GH4738 at extreme temperature has been investigated by isothermal and non-isothermal experiments. Resulted from the competitive diffusion of alloying elements, the oxide scale includes the outermost porous oxide layer (OOL), the inner relatively dense oxide layer (IOL) and internal oxide zone (IOZ) depending on the temperature and time. Higher temperature leads to the formation of big voids at the IOL/IOZ interface. At 1200°C, the continuity of Cr-rich oxide layer in the IOL is destroyed and thus spallation occurs. Extending oxidation time contributes to the size of Al-rich oxide particles within the IOZ increase. Based on this, the oxidation kinetics of GH4738 is discussed and the corresponding oxidation behavior at 900-1100°C is predicted.