Short-term oxidation resistance and degradation of Cr2AlC coating on M38G superalloy at 900–1100 °C

High temperature oxidation behavior of the Cr2AlC coating was investigated at 900–1100 °C. During the oxidation, a continuous Al2O3 scale formed, resulting in the improvement of the oxidation resistance of the substrate. Meanwhile, the oxidation induced depletion of Al within the Cr2AlC coating resulted in the transformation of Cr2AlC to Cr–C phases. Compared with bulk Cr2AlC, the Cr2AlC coating possessed similar oxidation behavior, but with higher oxidation rate. This is because a great number of columnar grain boundaries existed in the as-deposited coating, through which oxygen and nitrogen could diffuse inwardly, resulting in the internal oxidation and nitridation.

► High temperature oxidation behavior of Cr2AlC coating was investigated.
► Cr2AlC coating can improve the high temperature oxidation resistance of Ni-based M38G alloy.
► The good oxidation resistance of the Cr2AlC coating was due to the formation of Al2O3 oxide scale.
► Columnar grain boundaries in Cr2AlC coating lead to internal oxidation and nitridation.
► The internal oxidation and nitridation accelerate the degradation of the Cr2AlC coating.