Influence mechanism of K2SO4 addition on microstructure, mechanical properties and abrasion resistance of Fe-2wt%B alloy

Fe2B-type boride exists in Fe–B alloy with a form of netlike, rod-shaped, or fishbone structure. This results in high susceptibility of alloy to fracture. To improve the morphology of Fe2B, various contents of K2SO4 are added into an Fe-2wt%B alloy. The microstructure, mechanical properties and abrasion resistance of the modified alloy have been analyzed systematically.The results show that the α-MnS forms in the alloy, and increases with the increased K2SO4 in a relationship of y = 1.68× + 0.03. Moreover, the α-MnS can act as effective heterogeneous nuclei of M2B (where M represents Cr, Mn, and Fe), owing to a low lattice misfit of (111)α-MnS//(110)M2B. Meanwhile, the addition of element K can result in the formation of adsorbed film (K+ film) on the surface of M2B. By the joint action of α-MnS and K+ film, the structure of M2B changes from net-like into isolated block-shaped after heat treatment, and the shape factor K value of M2B increases from 0.13 to 0.44 with an increment of 241%. The change of M2B morphology effectively promotes an improvement of impact toughness and abrasion resistance of the alloy as a result.