Densification, phase transformation and tribological performance of TiC-coated diamond-dispersed Si3N4 composites by current-assisted sintering

Abstract A novel Si3N4-based composite with 30 vol.% TiC-coated diamond has been fabricated by means of current-assisted sintering. The effect of current pattern on the densification behavior, diamond graphitization, and Si3N4 α-β phase transformation was systematically investigated, along with the mechanical and tribological properties of the composites. The composites could be fully densified with minimal diamond graphitization due to the protective TiC coating. Continuous current sintering resulted in enhanced densification and phase conversion through localized Joule heating, whereas the pulsed current mode generated composites with superior Vickers hardness, up to 28 GPa, coefficients of friction (COF) as low as 0.06, and very high wear resistance (∼10−9 mm3/N·m). The interfacial bonding of diamonds to the Si3N4 matrix was considered as the dominant factor influencing the tribological performance of the composites. Use of lower sintering temperatures improves the bonding between the reinforcing particles and the matrix, and hence the wear resistance.