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

Abstract Si 3 N 4 /Si 3 N 4W /Ti(C 7 N 3 ) nanocomposites ceramic tool materials with the different content of Ti(C 7 N 3 ) and α-Si 3 N 4W 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 Si 3 N 4 /20wt%Si 3 N 4W /25wt%Ti(C 7 N 3 ) nanocomposite, which was sintered under 30 MPa at 1750 °C for 60 min, exhibited the finer microstructure with the elongated β-Si 3 N 4 grains and achieved better mechanical properties with a flexural strength of 890 MPa, a fracture toughness of 9.51 MPa m 1/2 , and a hardness of 18.08 GPa. The elongated Si 3 N 4 and Ti(C 7 N 3 ) grains contributed to the grains pulling-out, crack bridging and deflection. Si 3 N 4 /20wt%Si 3 N 4W /25wt%Ti(C 7 N 3 ) nanocomposite was oxidized weakly at 850 °C for 50 h but strongly at 1150 °C for 50 h.