Synthesis and Properties of MoSi2–MoB–SiC Ceramics

MoB and SiC particulate reinforced MoSi 2 matrix composites were synthesized in situ from Mo, Si, and B 4 C powder mixtures by self-propagating high-temperature synthesis (SHS). The SHS MoSi 2 –MoB–SiC products were vacuum hot-pressed (HPed) at 1400°C for 90 min to fabricate high-density (> 97.5% relative density) bulk composites. Microstructure refinement and improvements in the Vickers hardness and fracture toughness of the HPed composites were observed with increasing B 4 C content in the reaction mixture. The HPed composite of composition MoSi 2 –0.4MoB–0.1SiC exhibited grain size of 1–5 μm, Vickers hardness of 12.5 GPa, bending strength of 537 MPa, and fracture toughness of 3.8 MPa.m 1/2 . These excellent mechanical properties indicate that MoB and SiC particulate reinforced MoSi 2 composites could be promising candidates for structural applications.