Oxidation and cracking behaviors of triple-layered Cr2AlC coating

Abstract

Cr 2 AlC 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 Cr 2 AlC coating, with (Cr,Al) 2 O 3 inner layer, amorphous intermediate layer and crystalline Cr 2 AlC outer layer, was investigated at 900 and 1000 °C in air. The effect of the (Cr,Al) 2 O 3 inner layer as diffusion barrier was evaluated during the oxidation process . It is showed that the triple-layered Cr 2 AlC coating could effectively improve the oxidation resistance of the M38G alloy substrate, due to the Cr 2 AlC outer layer. The (Cr,Al) 2 O 3 inner layer could prohibit internal nitridation and retard interdiffusion at the coating/substrate interface, improving oxidation resistance of the triple-layered Cr 2 AlC coating. Furthermore, cracking of the triple-layered Cr 2 AlC 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. • The triple-layered coating improves the oxidation resistance of the M38G alloy effectively. • The (Cr,Al) 2 O 3 inner layer prohibits inter diffusion and internal nitridation during oxidation. • Thermal stress and stress due to amorphous layer crystallization lead to cracking of the coating.