Correlation of microstructure with hardness and wear resistance of surface composites fabricated by high-energy electron beam irradiation of Fe-based metamorphic powders

In this study, surface composites were fabricated with Fe-based metamoprhic powders by high-energy electron beam irradiation, and the correlation of their microstructure with hardness and wear resistance was investigated. Fe-based 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 composite layers of 1.3∼1.9 mm in thickness were homogeneously formed without defects and contained a large amount (up to 48 vol pct) of hard and fine Cr2B crystalline phases in the Cr0.19Fe0.7Ni0.11 matrix. Since the hardness and wear resistance of the surface composite layers were directly influenced by hard Cr2B phases, they were two to three times greater than those of the steel substrate. In particular, the two-layered surface composite showed a high hardness of ∼300 VHN even at 750 °C, as well as at room temperature, because Cr2B phases and the Cr0.19Fe0.7Ni0.11 matrix were hard and thermally stable.