Hardness and corrosion resistance of steel-based surface composites fabricated with Fe-based metamorphic powders by high-energy electron beam irradiation

Hardness and corrosion resistance of steel-based surface composites fabricated with Fe-based metamorphic powders by high-energy electron-beam irradiation were investigated in this study. Metamorphic powders were deposited on a plain carbon steel substrate, and then electron beam was irradiated on these powders without flux to fabricate a one-layered surface composite. A two-layered surface composite was also fabricated by irradiating electron beam again onto the powders deposited on the one-layered surface composite. The two-layered composite contained 48 vol.% of hard Cr2B crystalline phases in the Cr0.19Fe0.7Ni0.11 matrix, and thus its hardness was 2.5 times greater than that of the steel substrate. The corrosion resistance of the two-layered composite was better than that of an STS304 stainless steel or a coating fabricated by high-velocity oxygen fuel spraying of Fe-based metamorphic powders. This is because the Cr0.19Fe0.7Ni0.11 matrix of the surface composites and coating was selectively corroded, while Cr2B borides were retained inside pits. In the coating, the localized corrosion additionally occurred along splat boundaries, and thus the corrosion resistance of the coating was worse than that of the two-layered surface composite. These findings suggested that various applications of the fabricated surface composites to materials requiring high resistance to wear and corrosion were expected.