Effect of B3Si on the Structure and Properties of B4C Ceramics

Dense composite ceramics based on B 4 C with an addition of 10 to 50 wt % of B 3 Si were obtained by hot pressing. An increased amount of boron silicide decreases the hot pressing temperature to obtain a high-density material. We found a hot pressing temperature, optimal for each of the compositions and possess the highest hardness, which is associated with the formation of a fine-grained structure. Densification occurs during reactive hot pressing, which consists in the decomposition of B 3 Si into Si and BSi n ( n = 12–23) and further interaction with B 4 C to form SiC and B 12 (Si,B,C) 3 . The modification of boron carbide with silicon leads to the stabilization of hardness at ~24–26 GPa in the load range from 2 to 200 N. The highest bending strength of ~500 MPa is observed for samples with up to 20 wt % of B 3 Si. The optimal composition, which combines high values of hardness and flexural strength, is B 4 C–20 wt % B 3 Si.