Preparation and characterization of Si3N4-based composite ceramic tool materials by microwave sintering

Si3N4-based composite ceramic tool materials with (W,Ti)C as particle reinforced phase were fabricated by microwave sintering. The effects of the fraction of (W,Ti)C and sintering temperature on the mechanical properties, phase transformation and microstructure of Si3N4-based ceramics were investigated. The frictional characteristics of the microwave sintered Si3N4-based ceramics were also studied. The results showed that the (W,Ti)C would hinder the densification and phase transformation of Si3N4 ceramics, while it enhanced the aspect-ratio of β-Si3N4 which promoted the mechanical properties. The Si3N4-based composite ceramics reinforced by 15 wt% (W,Ti)C sintered at 1600 °C for 10 min by microwave sintering exhibited the optimum mechanical properties. Its relative density, Vickers hardness and fracture toughness were 95.73 ± 0.21%, 15.92 ± 0.09 GPa and 7.01 ± 0.14 MPa m1/2, respectively. Compared to the monolithic Si3N4 ceramics by microwave sintering, the sintering temperature decreased 100 °C，the Vickers hardness and fracture toughness were enhanced by 6.7% and 8.9%, respectively. The friction coefficient and wear rate of the Si3N4/(W,Ti)C sliding against the bearing steel increased initially and then decreased with the increase of the mass fraction of (W,Ti)C., and the friction coefficient and wear rate reached the minimum value while the fraction of (W,Ti)C was 15 wt%.