The Rate‐Dependent Response of Pressureless‐Sintered and Reaction‐bonded Silicon Carbide‐Based Ceramics

A comparison of the static and dynamic hardness and compressive strengths of seven different commercially available pressureless‐sintered ( PS ) and reaction‐bonded ( RB ) silicon carbide‐based ceramics is presented. The intent is to relate these mechanical properties to the microstructure formed during processing. Fine‐grained sintered SiC performed better than coarse‐grained SiC under indentation and compression loading. The sintered specimens had greater hardness and strength than the RB materials that contained a weaker silicon phase. Composite ceramics containing diamond and boron carbide as secondary phases exhibited greater hardness than the other materials. In addition, the compressive strength and hardness improved with strain rate of deformation for all the materials except for the RB materials and SiC–B 4 C composite. The weakening effect observed in the SiC–B 4 C composite during dynamic indentation can be attributed to the B 4 C phase which exhibits localized amorphization; however, the deleterious effects of B 4 C amorphization were reduced due to the strain‐rate hardening of SiC.