Effect of (Ni, Mo) and TiN on the microstructure and mechanical properties of TiB2 ceramic tool materials

TiB2–TiN composites with (Ni, Mo) as sintering aid have been fabricated by hot-pressing technique, and the microstructure and mechanical properties of the composites were investigated. Grain size and relative density of the composites increase consistently with an increase in the (Ni, Mo). In the case of 10 vol.% (Ni, Mo), the grain size decreases consistently with an increase in the TiN. Ni element is rich in the vicinity around TiN particles. (Ni, Mo) forms a continuous boundary phase around the matrix particles. TiN can improve the bonding strength among the TiB2 grain boundaries and change the fracture pattern from intergranular to transgranular fracture with the increase in TiN. The best mechanical properties of the composites are 1088.20 MPa for three-point flexural strength, 7.54 MPa m1/2 for fracture toughness and 21.53 GPa for Vickers hardness.