Simultaneously improved strength and toughness of in situ bi-phased TiB2–Ti(C,N)–Ni cermets by Mo addition

Abstract

Optimizing strength and toughness are always the key issues for cutter materials. Generally, increasing the strength of the material would sacrifice its toughness or vice versa. In this work, the TiB2–Ti(C,N)-(Ni + Mo) cermets with high strength and high toughness were fabricated in Mo–Ni–B4C-Ti-BN systems by reactive hot pressing. With the addition of Mo, the highest combustion temperature decreased and the matching degree between ceramic particles and Ni binder was improved, which lead to the decrease in the porosity of cermets and the refinement of ceramic particles. The fabricated TiB2–Ti(C,N)–Ni cermet with 2 wt.% Mo addition exhibited the simultaneously improved strength and toughness. The σUCS and KIC of the TiB2– Ti(C,N)-(Ni+2Mo) cermet were 3.24 GPa and 7.28 MPa·m1/2 respectively, which were increased by 11% and 20% compared with those of the cermet without Mo addition. The strengthening mechanisms of the cermets with Mo addition were attributed to the refinement of ceramic particles, the improved homogeneity in the microstructure and the simultaneously increase in the strength of interfacial bonding and the binder itself.