Study on the mechanical properties, microstructure and oxidation resistance of Si3N4/Si3N4W/Ti(C7N3) nanocomposites ceramic tool materials

Si3N4/Si3N4W/Ti(C7N3) nanocomposites ceramic tool materials with the different content of Ti(C7N3) and α-Si3N4W were sintered by various hot-pressing processes. Their mechanical properties of flexural strength, fracture toughness and hardness, microstructure and oxidation resistance were studied. The research results showed that Si3N4/20wt%Si3N4W/25wt%Ti(C7N3) nanocomposite, which was sintered under 30 MPa at 1750 °C for 60 min, exhibited the finer microstructure with the elongated β-Si3N4 grains and achieved better mechanical properties with a flexural strength of 890 MPa, a fracture toughness of 9.51 MPa m1/2, and a hardness of 18.08 GPa. The elongated Si3N4 and Ti(C7N3) grains contributed to the grains pulling-out, crack bridging and deflection. Si3N4/20wt%Si3N4W/25wt%Ti(C7N3) nanocomposite was oxidized weakly at 850 °C for 50 h but strongly at 1150 °C for 50 h.