Oxidation and decomposition of Ti2AlN MAX phase coating deposited on Nickel-based super alloy IN718

In this work, the oxidation behavior of Ti2AlN coating deposited on nickel super alloy IN718 was investigated. The coating was obtained by DC-magnetron sputtering at 540°C and subsequent vacuum annealing at 800°C for 1h. The coating morphology as well as the chemical composition were analyzed using SEM, EDS and XRD, respectively. The XRD results revealed that the coating mainly composed of Ti2AlN MAX phase. Cycling oxidation was performed at 700 °C and 800 °C in air. The XRD and SEM results proved the interaction between substrate and coating and the formation of the quaternary Ti3NiAl2N phase during oxidation at the interface. Due to the Ni diffusion towards the surface, the Ti3NiAl2N phase grew continuously and the Ti2AlN phase decomposed gradually resulting in a coating failure. The results indicate that the oxidation behavior of the coating is essentially controlled by the interdiffusion of Ni from substrate into the coating.