Fabrication and mechanical properties of SiC reinforced reaction-bonded silicon nitride based ceramics

SiC reinforced Si3N4 based ceramics were fabricated via nitridation of silicon, and the influence of SiC addition on the microstructure and mechanical properties of the as-prepared Si3N4/SiC ceramics were investigated. With SiC addition increase, β-Si3N4 grains growth was inhibited and equiaxed Si3N4 grains increased. This can be attributed to grain-boundary pinning effect due to SiC dispersion, resulting in finer β-Si3N4 grains with high aspect ratio. After nitridation and post-sintering at 1750 °C for 2 h, Si3N4/SiC composites with flexural strength of 614 MPa, youngʹs modulus of 263 GPa, hardness of 14.3 GPa were obtained with 10 wt% SiC addition. Compared with pure Si3N4 ceramics, the fracture toughen ss was also improved, reaching the peak value of 3.45 MPa m1/2 at the SiC fraction of 10 wt%. This can be accounted for the phenomena of crack deflection and bridging.