Substructure formation mechanism and high temperature performance in CoNiCrA1Y seal coating by laser melting deposition with inside-laser coaxial powder feeding

摘要

CoNiCrAlY coating with good bonding strength to the substrate, moderate hardness and fine integrity was produced by laser melting deposition inside-laser coaxial powder feeding, which is a promising seal coating for aircraft engine. Solidification mechanism of CoNiCrAlY coating was investigated to clarify the evolution of grains and substructures by SEM, XRD and TEM. Effect of cellular and dendritic substructure morphology with Y2O3 on the high temperature friction and oxidation behavior in CoNiCrAlY seal coating was also evaluated. The oxidation results of different temperature indicated that oxidation resistance of CoNiCrAlY coating is excellent. A continuous and protective Cr2O3 external oxide layer formed on coating surface at 873 K, while a more protective Al2O3 oxide layer formed on the coating surface at 1423 K. In-situ Y2O3 particles formed in CoNiCrAlY coating were thought to be beneficial for anchoring the oxide layer. The friction behavior at high temperature depends on substructure morphology. Wear resistance of CoNiCrAlY coating is significantly improved by cellular substructure with Y2O3. It is the main reason that the substructure morphology will change wear mechanism at high temperature.