Effect of graphite content on properties of B ₄ C‐W ₂ B ₅ ceramic composites by in situ reaction of B‐Gr‐ <scp>WC</scp>

Abstract

Abstract Strip‐shaped W 2 B 5 reinforced B 4 C ceramic composites were prepared via in situ reaction of boron(B)‐graphite(Gr)‐ WC system by powder metallurgy (P/M). In order to study the effect of the graphite content on the properties of the as‐fabricated ceramic composites, the powder mixture of B‐Gr‐ WC with various amounts of Gr powder were blended and consolidated by spark plasma sintering ( SPS ). The sintering parameters were shown as following: sintering pressure was set as 30 MP a; The three‐step sintering temperature was 1100‐1550‐1700°C and the duration time was set as 5‐5‐6 minutes, respectively. In situ formed strip‐shaped W 2 B 5 particles were dispersed homogeneously in B 4 C matrix, which resulted in a remarkable improvement on the fracture toughness and mechanical properties. Appropriate 5vol% residual Gr in the composite shows positive effect on the mechanical properties which achieved an optimal counter‐balance of fracture toughness and hardness, the relative density was 99.8%, the Vickers hardness can reach 30.2 GPa, and the fracture toughness was 11.9 MPa·m 1/2 when the sintering temperature was set at 1700°C.