Synergistic Reinforcement of SiN Based Ceramics Fabricated via Multiphase Strengthening under Low Temperature and Short Holding Time.

SiN ceramic as a tool material shows promising application prospects in high-speed machining fields; however, the required high mechanical properties and low-cost preparation of SiN ceramic tool materials restrict its application. Herein, synergistic reinforced SiN ceramic tool materials were fabricated by adding β-SiN seeds, inexpensive SiN whiskers and TiC particles into coarse commercial SiN powder (D = 1.5 μm), then sintering by hot-pressing with low temperature and short holding time (1600 °C-30 min-40 MPa). The phase assemblage, microstructure evolution and toughening mechanisms were investigated. The results reveal that the sintered SiN ceramics with synergistic reinforcement, compared to those with individual reinforcement, present an enhancement in relative density (from 94.92% to 97.15%), flexural strength (from 467.56 ± 36.48 to 809.10 ± 45.59 MPa), and fracture toughness (from 8.38 ± 0.19 to 10.67 ± 0.16 MPa·m), as well as a fine Vickers hardness of 16.86 ± 0.19 GPa. Additionally, the various reinforcement modes of SiN ceramics including intergranular fracture, crack deflection, crack bridging and whiskers extraction were observed in crack propagation, arising from the contributions of the added β-SiN seeds, SiN whiskers and TiC particles. This work is expected to serve as a reference for the production of ceramic cutting tools.