Mechanical Properties and Cutting Performance of Si3N4/Sc2W3O12 Composite Ceramic Tools Materials.

To address the poor thermal shock resistance and high brittleness of traditional ceramic tools, a novel Si3N4/Sc2W3O12 (SNS) composite ceramic material was developed via in situ synthesis using WO3 and Sc2O3 as precursors and consolidated by spark plasma sintering. Sc2W3O12 with negative thermal expansion was introduced to compensate for matrix shrinkage and modulate interfacial stress. The effects of varying Sc2W3O12 content on thermal expansion, residual stress, microstructure, and mechanical properties were systematically investigated. Among the compositions, SNS3 (12 wt.% Sc2W3O12) exhibited the best overall performance: relative density of 98.8 ± 0.2%, flexural strength of 712.4 ± 30 MPa, fracture toughness of 7.5 ± 0.3 MPa·m1/2, Vickers hardness of 16.3 ± 0.3 GPa, and an average thermal expansion coefficient of 2.81 × 10-6·K-1. The formation of a spherical chain-like Sc-W-O phase at the grain boundaries created a "hard core-soft shell" interface that enhanced crack resistance and stress buffering. Cutting tests showed that the SNS3 tool reduced workpiece surface roughness by 32.91% and achieved a cutting distance of 9500 m. These results validate the potential of this novel multiphase ceramic system as a promising candidate for high-performance and thermally stable ceramic cutting tools.