High mechanical properties of β-SiAlON/TiC0.3N0.7 ceramic composite prepared by pressureless spark plasma sintering

Abstract

ABSTRACT β-SiAlON/TiC0.3N0.7 composites containing 2.0-7.5 wt.% TiC0.3N0.7 are prepared by pressureless spark plasma sintering (SPS) with Al2O3-AlN-Y2O3 additives. The TiC0.3N0.7 phase particles are homogeneously dispersed in the β-SiAlON matrix. The reaction between the sample and the graphite mold can be avoided during the pressureless SPS. The β-SiAlON/TiC0.3N0.7 composite with 5 wt.% TiC0.3N0.7, fabricated at 1550°C, exhibits a high density of 3.28 g cm−3 (98% relative density), high Vickers hardness of 14.53 GPa, and high fracture toughness of 7.20 MPa m1/2. By further SPS under a pressure of 24 MPa at 1400 oC, these properties are enhanced to a higher density of 3.32 g cm−3 (full density), higher Vickers hardness of 15.87 GPa, and higher fracture toughness of 7.44 MPa m1/2. Obviously, the fracture toughness of the as-prepared β-SiAlON/TiC0.3N0.7 composites is apparently higher than those of the reported β-SiAlON-based ceramic composites prepared by pressurized SPS, which is mainly attributed to the highly dense microstructures of the interlocking lath β-SiAlON grains and the uniformly distributed TiC0.3N0.7 particles, and the disappearance of the oriented ununiform stress caused by uniaxial pressure in normal pressurized SPS. Accordingly, the pressureless SPS could be a potential technique for the fabrication of high-performance β-SiAlON matrix composites.