Microstructure evolution and cyclic oxidation performance of Cr2AlC transition layer as active diffusion barrier for Ni-based superalloy and NiCrAlY coating

Cr2AlC transition layer between the NiCrAlY coating and K417G superalloy was prepared to improve oxidation resistance of conventional NiCrAlY coating. Long-term cyclic oxidation was conducted at 1000 degrees C. Cr2AlC transition layer decomposed to Cr7C3 after annealing and further transformed to thermodynamically more stable continuous Cr23C6 during subsequent oxidation. Continuous Cr23C6 effectively blocked diffusion between NiCrAlY coating and substrate. Cr2AlC transition layer also supplied additional Al for NiCrAlY coating, greatly extended service life of the NiCrAlY coating. Furthermore, Cr2AlC, Cr23C6 and Cr7C3 were thermally matched to substrate and coating, avoiding coating spallation during cyclic oxidation.

Automated summary

The Cr2AlC transition layer was used to improve the oxidation resistance of the conventional NiCrAlY coating, and the long-term cyclic oxidation at 1000 degrees C showed that the Cr2AlC transition layer decomposed to Cr7C3 after annealing and further transformed to the thermodynamically more stable continuous Cr23C6 during subsequent oxidation. The continuous Cr23C6 effectively blocked diffusion between the NiCrAlY coating and the substrate, and the Cr2AlC transition layer also supplied additional Al for the NiCrAlY coating, greatly extending its service life. Furthermore, the thermal matching of Cr2AlC, Cr23C6, and Cr7C3 with the substrate and coating prevented coating spallation during cyclic oxidation.