Effects of temperature and additives content on SiC ceramics prepared by spark plasma sintering

Abstract

SiC ceramics were sintered with Al2O3-Y2O3-CaO as additives. The effects of sintering temperature and additives content on the relative density, polytype, microstructure and mechanical properties of SiC ceramics were investigated by Archimedes drainage method, XRD, SEM, TEM and Vickers hardness test. The results show that the relative density, hardness and fracture toughness of SiC ceramics increase firstly and then decrease from 1300 ℃ to 1800 ℃, and reach the maximum at 1700 ℃. The phase transformation from β-SiC to α-SiC occurs between 1700 ℃ and 1800 ℃. Reducing the content of additives can increase the grain boundary bonding strength, and can improve the hardness and inhibition of the grain growth. Under the condition of 1700 ℃ and 7% (mass fraction) additives content, the best sintering results are obtained, with relative density, hardness and toughness of 97.9%, 23.3 GPa and 4.1 MPa·m1/2, respectively.

Keywords

• silicon carbide
• sintering temperature
• sintering additive
• microstructure
• mechanical property