Effect of open porosity on flexural strength and hardness of ZrB2-based composites

In this work, Taguchi L32 experimental design was applied to optimize flexural strength and hardness of ZrB2-based composites which were prepared by SPS. With this aim, batch ZrB2-based composites tests were performed to achieve targeted experimental design with nine factors (SiC, Cf, MoSi2, HfB2 and ZrC content, milling time of Cf and SPS parameters such as temperature, time and pressure) at four different levels. Flexural strength of all composite was measured by three-point bending test. Hardness measurement was done by Vickers indenter. SEM was applied to evaluate microstructure. The results showed that SiC grain size plays important role on flexural strength and correlation between flexural strength and open porosity is low while hardness strongly depends to open porosity. Grain size variation in the range of ~1.5 µm to ~8 µm has little effect on hardness.