Microstructure and mechanical properties of WB ₂ –B ₄ C composites fabricated by boro/carbothermal reduction and SPS

Abstract

Abstract The phase composition, microstructure, and mechanical properties of the WB 2 –B 4 C composites fabricated by a combination of boro/carbothermal reduction and spark plasma sintering (SPS) method with WO 3 , B 4 C, and graphite as raw materials were investigated in this study. The experimental results showed that the relative density of the as‐sintered WB 2 –B 4 C composites was ∼93.1% and ∼99.5%, respectively, after being SPS sintered at 1600°C under the applied load of 30 MPa for 10 min. Scanning electron microscope analysis showed that a network structure with WB 2 grains surrounded by B 4 C grains was observed after sintering. Analyses of high‐resolution TEM showed semi‐coherent interface and lattice distortion transition region between WB 2 and B 4 C grains. The Vickers hardness of WB 2 –B 4 C composite increased to 22.3 ± 0.9 GPa at 9.8 N owing to the fully dense, solid solution of C, and three‐dimensional network structure. Moreover, the fracture toughness and flexural strength of WB 2 –B 4 C composite reach 6.04 ± 0.81 MPa m 1/2 and 750 ± 80 MPa, respectively, which could be attributed to the semi‐coherent interface between WB 2 and B 4 C grains.