Effect of graphite content on properties of B4C-W2B5 ceramic composites by in situ reaction of B-Gr-WC

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 MPa; 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.