Investigating the effects of Fe, Ni, or Cu additions on the microstructure and mechanical properties of W₂CoB₂ cermets

W₂CoB₂ is a type of ternary boride-based cermet. Endowed with prominent advantages including high hardness, high melting point, excellent wear resistance and superior corrosion resistance, it has been extensively applied in various industrial fields such as cutting processing, surface protection and mold manufacturing. In this study, the toughening of W₂CoB₂ cermet was achieved by means of binder phase strengthening, thereby further expanding its application scope. Considering that the mechanical properties of metal ceramics are affected by the bonding performance between the hard phase and binder phase, this study primarily focused on the toughening of cermets. Accordingly, first-principles calculations were used to investigate the effects of doping with transition metals Fe, Ni, or Cu on the interfacial bonding performance of the hard/binder phase. The results showed that doping with Fe or Ni enhanced the interfacial bonding performance, while Cu doping reduced the bonding performance. To verify the calculation results, W₂AB₂/A metal ceramic samples were prepared by vacuum liquid-phase sintering. It was found that adding Fe resulted in the best indentation toughness, which is consistent with the calculated results; however, the microhardness decreased. The microhardness and indentation toughness of the samples without and with Fe, Ni, and Cu added were determined to be 1983.5 HV_0.5 and 9.5 MPa·m^1/2, 1806.5 HV_0.5 and 12.4 MPa·m^1/2, 2123.3 HV_0.5 and 11.2 MPa·m^1/2, 2006.2 HV_0.5 and 10 MPa·m^1/2, respectively, and the coefficient of friction(COF) were 0.63, 0.47, 0.41, and 0.51, respectively. The addition of Fe and Ni can form a solid solution in the binder phase, thereby enhancing the interfacial bonding performance between the hard and binder phases. This significantly improves the indentation toughness of W₂CoB₂. During the wear process, an oxide layer forms on the surface of the binder phase, which reduces the friction coefficient of the sample and enhances its wear resistance. This study demonstrates that the addition of an appropriate amount of Ni can effectively enhance the fracture toughness and wear resistance of W₂CoB₂, while simultaneously maintaining its high hardness.