Synthesis, microstructure, and mechanical properties of boron suboxide materials doped with chromium boride

Improvement on the densification and fracture toughness of ceramic materials based on boron suboxide (B₆O) has been of great importance. The mechanical properties of B₆O with and without chromium boride addition, hot pressed at a temperature range of 1850–1900°C and pressures of 50–80 MPa for 20 minutes, were investigated. The relative density, phase relationship, microstructures and mechanical properties of the processed ceramics were examined. More than 96% of the theoretical density was obtained for both ceramic systems. A good combination of mechanical properties was obtained with the B₆O-CrB₂ material (H_V = 32.1 GPa, K_IC = 4.5 MPa · m^0.5) compared to the pure B₆O material (H_V = 30.5 GPa, K_IC = brittle). The addition of 1.7 wt.% CrB₂ resulted in a pronounced improvement in both the hardness and fracture toughness values. Crack bridging and deflection are some of the toughening mechanisms liable for the enhanced fracture toughness of the sintered ceramic materials.