Effect of boron nitride nanotubes content on mechanical properties and microstructure of Ti(C,N)-based cermets

Boron nitride nanotubes (BNNTs) reinforced Ti(C,N)-based cermets were fabricated by hot-pressing, and the effect of BNNTs content on their mechanical properties and microstructure was investigated. The composite containing 0.5 wt% BNNTs showed a flexural strength of 1785 MPa. Compared with monolithic Ti(C,N)-based cermets, the Ti(C,N)/BNNTs composite exhibited a significant increase in flexural strength and a slight increase in Vickers hardness and fracture toughness. The added BNNTs could refine matrix grains significantly; however, the excessive content of BNNTs aggregated in the matrix and resulted in a decline in the mechanical properties of the composites. The strengthening and toughening mechanisms of Ti(C,N)/BNNTs composite were discussed, including crack deflection, crack branching, grain bridging and transformation of fracture mode.