Influence of atomic migration mode at different temperatures on the microstructure, mechanical and cavitation erosion behaviors of Co-based alloy coating

摘要

Heat treatment (HT) was used to regulate atomic migration modes to optimize the microstructure and improve the cavitation erosion (CE) durability of thermal-sprayed CoCrAlYTaCSi coating. The structure evolution was analyzed by XRD, SEM and TEM. The mechanical and CE behaviors were characterized by a Vicker's hardness tester and vibratory apparatus. Results demonstrated that the migration, oxidation and precipitation of atoms were effectively interfered by changing HT conditions, which significantly affected the phase structure and properties of coatings. Splat interfaces provided a convenient path for atoms migration, and the inward migration of oxygen was faster at 600 degrees C, causing serious oxidation of internal structure. But directional long-range migration of Al was activated at higher temperatures, and thus a continuous oxide layer mainly composed of Al2O3 was generated on the coating surface, which could prevent oxygen from diffusing into the coating. Meanwhile, through the migration of atoms within the coating, especially at 950 degrees C, the splat interfaces were fused together, and many nano-carbides were precipitated at grain boundaries, finally favoring to improve the hardness and CE-resistance greatly. (C) 2021 Elsevier B.V. All rights reserved.