Preparation and characterization of Si3N4/(W, Ti)C nano-composite ceramic tool materials

Si3N4-based composite ceramic tool materials reinforced with nanoscale Si3N4 and microscale (W, Ti)C were fabricated by hot pressing and sintering technology. The flexural strength, fracture toughness and hardness of the sintered composites were tested and the microstructure and indention cracks were observed. The experimental results showed that the Si3N4/(W, Ti)C nanocomposites containing 18 vol% of nanoscale Si3N4 and 20 vol% of microscale (W, Ti)C, which were sintered under a pressure of 30 MPa at 1700 °C in vacuum condition for 45 min, had the optimum comprehensive mechanical properties. The appropriate addition of microscale (W, Ti)C and nanoscale Si3N4 accelerated the formation of elongated β-Si3N4 grains and contributed to the improvement of mechanical properties. The strengthening and toughening mechanisms for the Si3N4/(W, Ti)C composite ceramic tool materials was a synergistic effect of intergranular and transgranular fracture, crack bridging, deflection and branching.