Electron Beam Remelting for Enhancing Thermally Sprayed Coatings: A Case Study on Self-Fluxing NiCrBSi Powders with Tungsten Carbide

Thermally sprayed, self-fluxing NiCrBSi-based coatings, subsequently flame-remelted, exhibit notable abrasion and corrosion resistance. While flame remelting facilitates the formation of a homogeneous, pore-free microstructure and promotes adhesion to the substrate, it suffers from low processing efficiency and introduces considerable thermal loads into the material. In contrast, electron beam remelting (EBR) offers enhanced efficiency, reduced heat input, and the potential to achieve metallurgical bonding with the substrate. This study investigates the influence of EBR parameters on the microstructure, hardness, and elemental distribution of NiCrBSi-based coatings. Four powder compositions—with and without tungsten or tungsten carbide (WC) additives—were deposited via thermal spraying and subjected to EBR. The resulting coatings were analyzed using light and scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and Vickers microhardness testing. The optimized EBR process yielded dense, crack- and pore-free coatings with uniform elemental distribution and effective metallurgical bonding. Maximum matrix hardness values up to 881 HV0.1 were achieved, confirming the efficacy of EBR in enhancing the structural and mechanical integrity of thermally sprayed NiCrBSi coatings. It was also found that the addition of different reinforcement phases to the NiCrBSi matrix can significantly affect the overall microstructure and properties of the matrix itself.