Effect of Tungsten Inert Gas Remelting on Microstructure, Interface, and Wear Resistance of Fe-Based Coating

Tungsten inert gas arc (TIG) process was employed to remelt Fe-based coating deposited by plasma spraying. Subsequently, the microstructure, interface, and the wear resistance of the coatings before and after remelting were studied. The results showed that the lamellar structure, pores, and inclusions of Fe-based coating were eliminated and the porosity significantly decreased from 4% to 0.4%. The as-sprayed coating contained microcrystalline region, nanocrystalline region, and transition region, while single crystal region and rod-shaped (Fe,Cr)₂₃C₆ were observed in the remelted coating. There was no element diffusion and dissolution phenomenon at the interface; thus, the bonding form between the as-sprayed coating and substrate mainly was mechanical bonding. On the contrary, the diffusion transfer belt (DTB) emerged at the interface of the remelted coating and substrate, the remelted coating was bonded with the substrate metallurgically. Additionally, the average microhardness and elastic modulus of the remelted coating increased by 33.4% and 53.2%, respectively, compared with the as-sprayed coating. During wear process, the as-sprayed coating exhibited obvious brittle fracture characteristics, while the remelted coating appeared typical plastic deformation characteristics and its weight loss reduced by 39.5%. Therefore, TIG remelting process significantly improved the microstructure, mechanical properties, and wear resistance of Fe-based coating.