Effect of Sputtered AlY Coating on High-Temperature Oxidation Behavior of Stainless Steel

AlY coating on 1Cr18Ni9Ti stainless steel was prepared by magnetron sputtering method and some of them were pre-oxidized or vacuum diffusion annealed at 600°C, and the effect of the coating with different treatments on the oxidation behavior of the stainless steel was studied at 1,100°C in air. Results show that the order of the 24-h oxidation mass gain for the specimens is the stainless steel without coating > the stainless steel with coating but without any pre-treatment > the stainless steel with AlY coating after pre-oxidation treatment > the stainless steel with AlY coating after vacuum diffusion annealing. After oxidation, a thick and loose Fe /Cr film is formed on the stainless steel without coating, while thinner Fe /Cr film is formed on the stainless steel with AlY coating. Compared to the oxidation film formed on the steel with pre-oxidized coating, the one formed on the steel with vacuum diffusion annealed coating is thinner and denser. The rare earth Y and its oxides Y in the coating produce reactive element effect and improve the ductility/adhesion of the oxide film, which enhances the oxidation resistance of the stainless steel, especially in the vacuum diffusion annealed AlY coating.