Reactive hot pressing of SiC-ZrC composites at low temperature

SiC-ZrC composites with relative density in excess of 99% were prepared by reactive hot pressing (RHP) of SiC and ZrH₂ at 1800 °C for 1 h. The reaction between SiC and ZrH₂ resulted in the formation of ZrC_1-x. The formation process and densification behavior during RHP process were investigated. Low temperature densification of SiC-ZrC composites is attributed to the formed nonstoichiometric ZrC_1-x and the removal of SiO₂ impurity on the surface of SiC particles. As reinforced phase, ZrC_1-x has inhibiting effect on the abnormal grain growth of SiC, resulting in homogeneous microstructure of fine SiC grains. Adding 10 wt% ZrH₂ to SiC, the formed SiC-4.62 vol% ZrC composite exhibited better mechanical properties (Vickers hardness of 27.6 ± 0.7 GPa, flexure strength of 448 ± 38 MPa, fracture toughness of 6.0± 0.3 MPa·m^1/2, respectively) than monolithic SiC ceramic.