Microstructure and wear resistance of in situ synthesized ZrB₂-ZrC/Fe composite coating produced by plasma cladding

A kind of Fe-based ceramic coatings with ZrB₂ and ZrC as multi scale strengthening phases on the surface of Q235 steel were fabricated by plasma cladding using Fe, Zr, and B₄C powder mixture as precursor. The phase composition, microstructure, microhardness and the wear resistance comparative test of ZrB₂-ZrC/Fe coating and Q235 steel were investigated. The microstructure evolution, the formation of the phase and the wear mechanism were discussed. The results show that ZrB₂-ZrC/Fe coatings are composed of ZrB₂, ZrC, α-Fe, Fe₃C and Fe₂B phases. ZrB₂ phase presents acicular, clubbed and petal forms. ZrC phase is irregular polygon shape. With the increasing of (Zr+B₄C) raw powder, the contents of ZrB₂ and ZrC are increasing, the size of ZrB₂ and ZrC become large. The plasma clad ZrB₂-ZrC/Fe composite coating is closely and metallurgically bonded to the Q235 steel substrate. Compared with Q235 steel substrate, the wear resistance of the coating is improved significantly, up to 5.45 times than that of the substrate. The main wear mechanism of ZrB₂-ZrC/Fe composite coating is abrasive wear, the main fracture mode of the composite coating is transgranular fracture.