A study on in-situ synthesis of TiB2–SiC ceramic composites by reactive hot pressing

Abstract

TiB2–SiC ceramic composites with (10–20) wt% SiC were in-situ synthesized by the reactive hot pressing (RHP) process at 1700 °C under 32 MPa in vacuum. The influence of SiC content and sintering time on the microstructure and mechanical properties of the composites was investigated in detail. The fracture toughness increased while the flexural strength and hardness decreased as the content of SiC increased. Elongated TiB2 grains with a diameter of 1–2 μm and an aspect ratio of 3–6 were in-situ synthesized in the composites. The composite containing 15 wt% SiC had the optimum comprehensive mechanical properties with flexural strength of 704 MPa, fracture toughness of 5.6 MPa m1/2 and hardness of 19.8 GPa. The improved mechanical properties were attributed to the mixed fracture mode, the strengthening and toughening mechanisms of SiC particles and elongated TiB2 grains including crack bridging, crack deflection, crack branching, grain fracture and the interlocking structure. The fracture toughness and hardness increased due to the improved relative density and higher yield of elongated TiB2 grains as the sintering time increased. However, the abnormal grain growth deteriorated the flexural strength when the sintering time further increased.