Investigations on microstructure, mechanical properties and abrasion resistance of 4wt%Cr-2wt%Mn-2wt%Cu-Fe-B alloy

The microstructure, mechanical properties and abrasion resistance of Fe-B alloy with 4wt%Cr-2wt%Mn-2wt%Cu addition have been systematically investigated. The results show that the microstructures mainly consist of martensite and boride (M2B) in the as-cast and heat treated Fe-B alloys; after heat treatment, the morphology and volume fraction of the M2B have little change, meanwhile the nucleation and precipitation of secondary borocarbide M23(C, B)6 probably take place in an in situ manner within martensite. Moreover, the M2B is identified as chemical formula of Fe2.04Cr0.11Mn0.07(B, C) reflecting body-centred tetragonal (bct) structure, and the secondary borocarbide M23(B, C)6 has the stoichiometry of Fe18.84Cr2.84Mn0.57(B, C)6 with face-centred cubic (fcc) structure. After heat treatment, the matrix hardness and bulk hardness of Fe-B alloy decrease owing to the decreasing of B/C concentration of matrix caused by the precipitation of M23(C, B)6, while the fracture toughness of Fe-B alloy increases. Meanwhile, the heat treatment will decrease the wear resistance of Fe-B alloy, i.e. the wear resistance of Fe-B alloy would decrease with reduction of the matrix hardness.