Mechanical properties and microstructure of Al2O3-SiCw ceramic tool material toughened by Si3N4 particles

Al₂O₃-SiC_w toughened ceramic tools play vital role in high-speed machining of nickel-based superalloys due to their superior mechanical properties. Herein, owing to synergistic toughening mechanism, α-Si₃N₄ particles are employed as reinforcement phase into Al₂O₃-SiC_w ceramic composite to optimize mechanical properties of Al₂O₃-SiC_w ceramic tools. Moreover, the influence of Si₃N₄ content and sintering parameters on microstructure and mechanical properties of Al₂O₃-20 vol%SiC_w ceramic tool material is systematically investigated. Results reveal that appropriate amount of Si₃N₄ particles is required to effectively increase the density of Al₂O₃-SiC_w ceramic composites. The presence of Si₃N₄ particles leads to formation of novel β-sialon phase during hot-press sintering, which effectively enhances fracture toughness and flexural strength of Al₂O₃-SiC_w ceramic composites. It is observed that grain size of newly formed β-sialon phase is extremely sensitive to hot-pressing sintering conditions. The degree of chemical transformation of α-Si₃N₄ into Si_6-zAl_zO_zN_8-z (β-sialon) and z-value of Si_6-zAl_zO_zN_8-z are significantly influenced by sintering temperature. Overall, Al₂O₃-20 vol%SiC_w-15 vol%Si₃N₄ ceramic tool material, with 1.5 vol%Y₂O₃-0.5 vol%La₂O₃-0.5 vol%CeO₂ (YLC) sintering additive, rendered optimal mechanical properties after sintering at 1600 °C under 32 MPa for 30 min. Improved mechanical performance can be ascribed to synergistic toughening and strengthening influence of whiskers and particles.