The role of carbon addition on properties of boron carbide- silicon carbide composites

In this research, composites were produced by mixing boron carbide (B4C) and silicon carbide (SiC) with varying amounts of carbon (C) and densifying them via spark plasma sintering at 1950 °C for 5 min. The effects of different C contents on the properties of the composites were observed. Density, elastic modulus, microstructure, Vickers hardness, and fracture toughness were evaluated. It has been observed that the oxygen content of starting powders should be matched with the added C content to obtain high density and desirable mechanical properties. The highest density, elastic modulus, and hardness values were obtained in samples containing 1.5 wt% C. The highest elastic modulus was obtained in the 10 wt% B4C–SiC-1.5 wt% C sample, at 451 GPa. The highest hardness value was 32.85 GPa, corresponding to the sample containing 90 wt% B4C–SiC-1.5 wt% C. The highest fracture toughness value was attained by the sample containing 10 wt% B4C–SiC-2.5 wt% C, at 2.87 MPa m1/2. Lastly, the composite samples showed transgranular fracture behavior.