Investigating efficiency of α-Al 2 O 3 diffusion barrier layer in oxidation of EB-PVD NiCrAlY coatings

Abstract

MCrAlY coatings, as a group of high temperature coatings, have extensively been considered for protecting gas turbine blades against oxidation and hot corrosion. At temperatures of more than 1000°C, interdiffusion between superalloy substrate and coating is one of the most important factors for controlling the lifetime of these coatings. In this paper, thin layers of α-Al₂O₃ were used as a diffusion barrier between superalloy substrate and coating using electron beam physical vapour deposition method. These barrier layers successfully blocked the diffusion of substrate alloy elements such as tungsten, molybdenum and, in particular, titanium into the coating. Results showed that using these diffusion barrier layers between superalloy substrate and coating can considerably improve the oxidation resistance of NiCrAlY coatings so that the parabolic rate constant in the samples with micrometric diffusion barrier layer is about one-third of that in the samples without it.