Effect of Ni content on microstructures and mechanical properties of hot-pressed TiC-TiB2-Ni composite

A TiC-TiB2-Ni composite with different Ni contents was synthesized using a hot pressing method. XRD analyses showed that the TiC-TiB2-Ni composite mainly consisted of TiC and TiB2 phases, and a small amount of metal Ni was also detected except the uncertain peaks. SEM observations showed that TiB2 phases were homogeneously distributed on the TiC matrix and the Ni enriched area in white contrast uniformly distributed on the phase interface, grain boundaries between the TiB2 and TiC grains or the triple junctions among the grains. The Ni enriched area contained metal Ni and NiTi2 compound according to TEM analyses. The experimental results showed that with increasing the Ni content, the volume density of the TiC-TiB2-Ni composite increased, and the hardness, flexural strength and fracture toughness all first increased and then decreased. When the Ni content was 8%, the optimum hardness, flexural strength and fracture toughness of the TiC-TiB2-Ni composite was 18.8 GPa, 604 MPa and 8.9 MPa·m1/2, respectively.