Spark plasma sintering of Ti(C, N)-based cermet tool material doped with refractory rare metal carbides (TaC/NbC/VC): Core-rim structure, grains and mechanical properties

The secondary carbides have great impacts on microstructure and mechanical properties of Ti(C, N)-based cermets. In the study, Ti(C, N)-based cermets doped with different refractory rare metal carbides TaC/NbC/VC which was used for cutting tools were prepared by spark plasma sintering. The effects of TaC, NbC and VC on core-rim structure, grain size and mechanical properties of the cermets were studied. TaC/NbC/VC promotes the growth of solid solution phase, reduces the size of black core, increases the intergranular fracture and decreases the cleavage fracture. The solid solution effect and grain refinement effect of VC are stronger than that of NbC, while NbC is superior to TaC. Adding appropriate TaC/NbC/VC can improve the mechanical properties. The best comprehensive mechanical properties of Ti(C, N)-based cermets are achieved with the addition of 3 wt% VC, with a relative density of 99.5%, Vickers hardness of 18.4 ± 0.3GPa, fracture toughness of 10.7 ± 1.3 MPa·m1/2, and flexural strength of 947.4 ± 12.6 MPa. •The solid solution effect and grain refinement effect of VC are stronger than that of NbC, while NbC is superior to TaC.•The addition of TaC/NbC/VC can promote the dissolution and precipitation process of the solid solution phase.•Adding appropriate amount of NbC can form more rimless black grains.•Adding appropriate amount of VC can make the solid solution phase present honeycomb structure.