Oxidation behavior of Ni(Co)CrAlYHf(Si) coatings on DS superalloy at 1 150 ℃
(1.北京市北京航空航天大学先进高温结构材料国家重点实验2.National Defence Key Laboratory for Advanced High Temperature Structural Materials,Beijing Institute of Aeronautical Materials, Beijing 100095, China3.Beijing Institute of Aeronautical Materials, Beijing 100095, China4.湖南省长沙市中南大学机电工程学院5.黑龙江省哈尔滨市哈尔滨工业大学材料科学与工程学院)
Abstract: Two Ni(Co)CrAlY coatings were deposited by EB-PVD method on a DS superalloy of Ni-Al-Cr-Co-W-Mo-Ta-Hf system. SEM, XEDS and XRD were used to study the oxidation behavior of the coatings. The two coatings show a good protection for the DS superalloy. The results of the isothermal oxidation test at 1 150 ℃ for 100 h show that the oxidation tendency obeys the parabolic law, and the oxidation rate constant Kp of the coated specimens decreases to about 1/3 of that for the bare superalloy. After oxidation, a continuous alumina-based scale is formed at the surfaces of the coated samples. Y2O3, NiO and SiO2 are also detectable in the oxide scale. A large number of Al in the coating is consumed due to high-temperature diffusion and oxidation reactions, and the NiAl phases in the coating are almost completely transformed to Ni3Al phases. For the Hf-bearing coating, some HfO2 particles exist at the interface between the coating and the substrate. Although internal oxidation occurs, the coating still shows a good adhesion with the superalloy substrate even after oxidation for 100 h. For the bare DS superalloy, after 100 h oxidation at 1 150 ℃, only discontinuous alumina-based oxide particles exist on the surface. Oxide spallation occurs for the bare alloy.
Key words: Ni(Co)CrAlY coating; DS superalloy; interdiffusion; oxidation behavior