Epitaxial growth and oxidation behavior of the NiCoCrAlYTa/Y2O3 coating on a nickel-based single-crystal superalloy blade tips, produced by electro spark deposition

Abstract

The characteristics of the working surface are often related to the safety and longevity of the machine, therefore, various functional coatings are used to meet the special needs of particular components. Ni-based single crystal superalloy blade tips frequently suffer from oxidation, corrosion, and wear under harsh conditions. To improve these problems, the NiCoCrAlYTa/Y2O3 metal matrix composite coating was prepared by electro spark deposition. In this work, the microstructure and epitaxial growth behavior of the NiCoCrAlYTa/Y2O3 coating were investigated, and the oxidation resistance of the substrate and the coating were evaluated and compared. The coating showed ultra-fine columnar crystal structure. The diffusion between the substrate and the coating elements caused by the instantaneous high temperature generated by the electro spark deposition endowed the coating with extremely high metallurgical bonding strength. The ultra-high cooling rate and approximately one-dimensional unidirectional rapid solidification made the Y2O3 nanoparticles evenly dispersed in the coating and realized directional epitaxial growth. The NiCoCrAlYTa/Y2O3 coating exhibited excellent oxidation resistance compared to the substrate. Y2O3 nanoparticles changed the diffusion path of the elements and accelerated the formation of the Al2O3 film. The synergistic effect of ultra-fine microstructure and nanoparticles on the adhesion between the oxide scale and the coating was improved.