Strengthening of Plasma-Sprayed AlCoCrFeNi High-Entropy Alloy Coatings by Laser Remelting

Abstract

To further enhance the AlCoCrFeNi high-entropy alloy (HEAs) coatings prepared by plasma spraying, laser remelting was employed to process the surface. This study investigates the differences in microstructure and the changes in properties between the laser-remelted coatings and the as-sprayed coatings. The results indicate that the laser-treated coating is composed of BCC phase and a small amount of α-Al₂O₃, forming a good metallurgical bond with the substrate. The layered structure of the sprayed coating has been eliminated, with grains rearranged and grown anew, resulting in an increase in hardness from 453.2 HV_0.2 to 591.5 HV_0.2. In electrochemical tests, the remelted coatings had higher corrosion potentials and lower self-corrosion current densities. After XPS testing, the passivation film of the remelted coating exhibits high intensities of Cr₂O₃ and Fe₂O₃. After laser remelting, pores and cracks in the coating are basically eliminated, the microstructure becomes more uniform and denser, and the hardness and wear resistance of the coating are significantly improved; the reduction in coating defects decreases the likelihood of corrosion, enhances the uniformity of the passivation film on the coating surface, and thereby improves the corrosion resistance of the coating. In summary, the laser remelting process can effectively enhance the coating by improving the microstructure of the sprayed coating, thereby enhancing its overall performance.