Oxidation and cracking behaviors of triple-layered Cr2AlC coating

Abstract Cr2AlC coating has potential applications as high temperature protective coating. However, inevitable interdiffusion at coating/substrate interface promotes Al depletion and deteriorates its oxidation resistance. In the present work, the oxidation behavior of a triple-layered Cr2AlC coating, with (Cr,Al)2O3 inner layer, amorphous intermediate layer and crystalline Cr2AlC outer layer, was investigated at 900 and 1000 °C in air. The effect of the (Cr,Al)2O3 inner layer as diffusion barrier was evaluated during the oxidation process. It is showed that the triple-layered Cr2AlC coating could effectively improve the oxidation resistance of the M38G alloy substrate, due to the Cr2AlC outer layer. The (Cr,Al)2O3 inner layer could prohibit internal nitridation and retard interdiffusion at the coating/substrate interface, improving oxidation resistance of the triple-layered Cr2AlC coating. Furthermore, cracking of the triple-layered Cr2AlC coating was found after oxidation at 900 and 1000 °C, due to the thermal stress and internal stress introduced by intermediate amorphous layer crystallization during oxidation.