Pressureless sintered SiC matrix toughened by in situ synthesized TiB2: Process conditions and fracture toughness

This paper reports the fabrication of SiC toughened by in situ synthesized TiB2 based on pressure-less sintering technique using TiO2, B4C, C and SiC as starting materials. The process conditions were investigated in detail, including the pre-sintering temperatures, carbon contents, differently sized TiO2 powders, TiB2 volume contents, final sintering temperature and time. These conditions were found to have great influence on the TiB2 toughened SiC in terms of relative density, TiB2 particle size and fracture toughness. Homogeneous dispersion of in situ synthesized TiB2 secondary phase was confirmed to enhance the KIC of the SiC matrix. The KIC of SiC toughened by in situ synthesized TiB2 (15 vol%) reaches 6.3 MPa m1/2, which is among the highest values reported so far on TiB2 reinforced SiC composites based on the pressure-less sintering technique using TiO2 as Ti source.