Microstructure and mechanical properties of newly synthesized Mo(Co,Fe)B cermets

Abstract

In this work, a novel Mo(Co,Fe)B cermet was prepared using Mo, Fe, Co and B powders and the reaction boronizing sintering route. The phase transformation, thermal behavior, densification behavior, microstructure and mechanical properties of cermets are systematically investigated. After sintering, the microstructure of cermets was composed of Mo(Co,Fe)B hard and CoFe binder phases. The formation of Mo(Co,Fe)B phase during solid-state sintering occurred by the reactions of 2Fe + B → Fe2B, 2Co + B → Co2B and 2Mo + Fe2B + Co2B → 2Mo(Co,Fe)B. During liquid-phase sintering, two liquid phases, namely L1 and L2, were sequentially generated by the reactions of CoFe + Fe2B + Co2B → L1 and CoFe + L1 + Mo(Co,Fe)B → L2, respectively. The as-obtained cermet exhibited excellent comprehensive mechanical properties with hardness of 89.5 ± 0.2 HRA, transverse rupture strength of 1927 ± 31 MPa and fracture toughness of 17.5 ± 0.4 MPa•m1/2. In summary, these findings look promising for future preparation and application of low-cost and high-performance ternary boride cermets.