Hardness and Wear Resistance of (CrB, MoB)/Steel Surface Composites Fabricated by High-Energy Electron Beam Irradiation

摘要

The present study is concerned with the improvement of hardness and wear resistance in (CrB, MoB)/ carbon steel surface composites fabricated by high-energy electron beam irradiation. Three kinds of powder mixtures, i.e., 50CrB-50MgF_2(flux), 50MoB-50MgF_2, 25CrR-25MoB-50MgF_2 (wt. percent), were placed on a plain carbon steel substrate, which was then irradiated with electron beam. In the specimens fabricated with flux powders, the surface composite layer of 0.8-1.3 mm in thickness was successfully formed without defects, and contained a large amount (up to 48 vol. percent) of Cr_(1.65)Fe_(0.35)B_(0.9) or Mo_2FeB_2 in the martensitic matrix. The hardness and wear resistance of the surface composite layer were directly influenced by hard borides, and thus were about 3 to 7 times greater than those of the steel substrate. Particularly in the surface composite fabricated with CrB and MoB powders, the wear resistance was most excellent because the hardness of the cell boundary region and martensitic matrix was very high and because borides were connected to form a network structure along cell boundaries.