Processing and mechanical characterisation of monolithic silicon carbide ceramic consolidated by spark plasma sintering (SPS)

Silicon carbide ceramics were fabricated using the spark plasma sintering technique without the use of additives. The sintering process was carried out at four different temperatures in the range of 2 073 - 2 223 K under two different pressures, 40 MPa and 80 MPa, under vacuum. The effects of different temperatures and pressures on the density, Vickers hardness, fracture toughness, and microstructure were examined. Fully dense monolithic silicon carbide ceramics with a relative density of approximately 99 % were obtained. Increasing the pressure from 40 to 80 MPa and the temperature from 2 073 to 2 223 K resulted in an increase in the relative densities of spark plasma sintered ceramics from 87 % to 97.5 % and 95.5 % to 99.7 %, respectively. The results revealed that the silicon carbide ceramic spark plasma sintered at 2 223 K while applying 80 MPa of pressure with a 5-minute soaking time under vacuum has the highest hardness and fracture toughness values of 31.9 GPa and 3.6 ± 0.3 MPa • m^1/2, respectively.