Investigations on microstructure, oxidation, and tribological behavior of NiCoCrAlYTa/Y2O3 blade tip protective coating produced by electro spark deposition over a wide temperature range

NiCoCrAlYTa/Y2O3 coatings were prepared on two nickel-based superalloys by electro spark deposition (ESD). The ESD coatings "inherited" the microstructure of the substrate, which depended on the orientation of the substrate and the primary solidification phase of the coating. Columnar crystal structure had fewer grain boundaries, better high-temperature bearing capacity, and a more uniform "glaze" layer than equiaxed crystal structure, which allowed it to exhibit better oxidation resistance and wear resistance. The competition between the lubrication/wear reduction of the "glaze" layer and the plowing caused by hard oxide particles influenced the tribological behaviors of both. The difference in cutting performance between the two coatings is related to the oxidation behavior of the coating and the structure of the "glaze" layer.