Effects of Al, B and C additives on microstructure and mechanical properties of spark-plasma-sintered SiC ceramics

Abstract

Densification of the SiC powder without and with additives B+C or Al+B+C was carried out by spark plasma sintering (SPS). The unique features of the process are the possibilities of using a very fast heating rate and a short holding time to obtain fully dense materials. The heating rate and applied pressure were kept at 100° C/min and 40 MPa, while the sintering temperature and soaking time varied from 1650-1850° C for 10-40 min, respectively. The SPS-sintered specimens with the addition of B+C or Al+B+C at 1850° C reached near-theoretical density. The 3C major crystalline phase of SiC was transformed to 6H at 1800° C and translated to 4H during prolonged annealing at 1850° C. The strength of 531.0 MPa and the fracture toughness of 3.9 MPa• m(1/2) were obtained by the addition of Al+B+C to SiC prepared at 1850° C for 10 min.