Dual-grained Mo_2FeB_2-based cermets containing WC fabricated via multi-step sintering approach: Microstructure, mechanical properties and interface characteristics

摘要

In this study, a novel method was proposed for preparing dual-grained Mo_2FeB_2-based cermets by partially replacing pre-sintered Mo_2FeB_2 particles with WC via multi-step sintering. The microstructure, mechanical properties, and interface structures of the cermets were systematically investigated. The results reveal that the final microstructure of the as-prepared cermets contained fine Mo_2FeB_2 grains and coarse Fe_3(W,Mo)_3C grains, and the average grain size exhibited a typical bimodal distribution. Interestingly, a thin film was formed at the rim/binder phase boundary between Mo_2FeB_2 grains and Fe phases, which alleviated the lattice distortion. Furthermore, the formation of coherent interfaces was observed at the grain/binder phase boundary between Fe_3(W,Mo)_3C grains and Fe phases, and at the rim/rim grain boundary between neighboring Mo_2FeB_2 grains, resulting in a significant enhancement in interfacial bonding strength. The unique interfacial structures were conducive to reinforce strength and toughness of Mo_2FeB_2-based cermets. As a result, superior hardness (90.3 ± 0.1 MPa) and fracture toughness (25 ± 0.5 MPa m~(1/2)) were obtained, without losing lots of transverse rupture strength (1853 ± 21 MPa).