C. X. Li, Q. Zhang, G. J. Yang, C. J. Li, School of Materials Science and Engineering, Xi'an Jiaotong University, Xi'an, China; X. R. Wang, School of Materials Science and Engineering, Xi’an Jiaotong University, Xi'an, China
Nanostructured NiCrAlY coating was deposited on a Ni-based superalloy substrate by cold spraying. The microstructure of the coating was characterized using x-ray diffraction (XRD) and scanning electron microscopy (SEM). The influence of surface morphology on the microstructure and high temperature oxidation behavior of coating was investigated. The surface morphology was adjusted through shot peening treatment. Results showed that after shot peening, surface roughness of cold-sprayed NiCrAlY coating was decreased. The coating surface becomes more uniform. Discontinuous oxide in spherical morphology was formed on the surface of the as-sprayed coating during high temperature oxidation. Oxidation at a lower temperature of 900oC for a limited time leads to formation of θ-Al2O3 in a needle-like morphology. The oxide was transformed to block-like α-Al2O3 with prolonged oxidation for 40h. At 1000 oC, oxidation resulted only in the formation of α-Al2O3 phase on the coating surface. Shot peening changed the as-sprayed rough surface to a smooth one , which benefits the formation of a continuous and uniform oxide layer on NiCrAlY coating surface.
Summary: Nanostructured NiCrAlY coating was deposited on a Ni-based superalloy substrate by cold spraying. The microstructure of the coating was characterized using x-ray diffraction (XRD) and scanning electron microscopy (SEM). The influence of surface morphology on the microstructure and high temperature oxidation behavior of coating was investigated. The surface morphology was adjusted through shot peening treatment. Results showed that after shot peening, surface roughness of cold-sprayed NiCrAlY coating was decreased. The coating surface becomes more uniform. Discontinuous oxide in spherical morphology was formed on the surface of the as-sprayed coating during high temperature oxidation. Oxidation at a lower temperature of 900oC for a limited time leads to formation of è-Al2O3 in a needle-like morphology. The oxide was transformed to block-like á-Al2O3 with prolonged oxidation for 40h. At 1000 oC, oxidation resulted only in the formation of á-Al2O3 phase on the coating surface. Shot peening changed the as-sprayed rough surface to a smooth one , which benefits the formation of a continuous and uniform oxide layer on NiCrAlY coating surface.
