Effect of different additives and open porosity on fracture toughness of ZrB2-SiC-based composites prepared by SPS

In this work, Taguchi experimental design technique was applied to determine the most influential additives and SPS parameters for optimizing fracture toughness of ZrB2-SiC based composites. In this case, nine factors (SiC, Cf, MoSi2, HfB2 and ZrC content, milling time of Cf and SPS parameters such as temperature, time and pressure) were examined on four different levels in order to obtain the optimum mixture. A total of 32 mixtures were prepared in accordance to the L32 array proposed by the method. Fracture toughness of all composites was measured by single edge-notch beam test. SEM was applied to evaluate microstructure. It has been concluded that the open porosity up to 10% has no significant effect on fracture toughness but in higher values, it is varied inversely with its changes. The results showed that temperature with 34.7% and SiC with 29.7% have significant effect on fracture toughness. Cf, M.t, HfB2, pressure and time with 2.3%, 3.2%, 0.05%, 0.44% and 2.3% have influence on fracture toughness, respectively. ZrC has 7.8% and MoSi2 has 6.3% on fracture toughness.