Densification and properties of transition metal borides-based cermets via spark plasma sintering

Engineering borides like TiB2 and ZrB2 are difficult to sinter materials due to strong covalent bonding, low self-diffusion coefficient and the presence of oxide layer on the powder particles. The present investigation reports the processing of hard, tough and electrically conductive transition metal borides (TiB2 and ZrB2) based cermets sintered with 6 wt.% Cu using spark plasma sintering (SPS) route. SPS experiments were carried out with a heating rate of 500 K/min in the temperature range of 1200–1500 °C for a varying holding time of 10–15 min and the optimization of the SPS conditions is established. A maximum density of ∼95% ρth in ZrB2/Cu and ∼99% ρth in TiB2/Cu is obtained after SPS processing at 1500 °C for 15 min. While the optimized TiB2/Cu cermet exhibits hardness and fracture toughness of ∼17 GPa and ∼11 MPa m1/2, respectively, the optimized ZrB2/Cu cermet has higher hardness of ∼19 GPa and fracture toughness of ∼7.5 MPa m1/2, respectively. High electrical conductivity of ∼0.20 MΩ−1 cm−1 (TiB2/Cu) and ∼0.15 MΩ−1 cm−1 (ZrB2/Cu) are also measured with the optimally sintered cermets.