Contribution of SiC particle size and spark plasma sintering conditions on grain growth and hardness of TiB₂ composites

In this paper, the significance and contribution of SiC particle size and spark plasma sintering (SPS) parameters on the mean TiB₂ grain size and Vickers hardness of TiB₂–20 vol% SiC ceramic composites were studied. An L9 orthogonal array was used to design of experiments by the Taguchi method to investigate the effects of four processing parameters including the SPS temperature, SPS soaking time, SPS pressure and SiC particle size. Three levels were selected for each parameter and the analysis of variance (ANOVA) was employed for optimization of processing parameters. The SPS temperature was identified as the most effective parameter on the as-sintered grain size and hardness of TiB₂–SiC ceramics, but, the SPS soaking time does not have an obvious influence on these characteristics. The presence of SiC together with the in-situ formed nano-sized TiC phases acted as grain growth inhibitors which was helpful to obtain a fine-grained composite microstructure. The ANOVA disclosed that the sintering temperature of 1800 °C, the soaking time of 15 min, the pressure of 30 MPa and the SiC particle size of 200 nm are the optimal processing conditions. A Vickers hardness of 28.5 GPa was predicted at such optimized conditions which is near to the experimentally measured value of 27.4 GPa as the confirmation test.