Silicon carbide-titanium diboride ceramic composites

The effect of TiB2 content on mechanical properties of silicon carbide-titanium diboride ceramic composites was studied. The hardness of the ceramics decreased from 27.8 GPa for nominally pure SiC to 24.4 GPa for nominally pure TiB2. In contrast, fracture toughness of the ceramics increased from 2.1 MPa m1/2 for SiC to ∼6 MPa m1/2 for SiC with TiB2 contents of 40 vol.% or higher. Flexure strengths were measured for three composites containing 15, 20, and 40 vol.% TiB2 and analyzed using a two parameter Weibull analysis. The Weibull modulus increased from 12 for 15 vol.% TiB2 to 17 for 20 and 40 vol.% TiB2. Microstructural analysis revealed microcracking in the ceramics containing 20 and 40 vol.% TiB2. The ceramic containing 40 vol.% TiB2 had the best combination of properties with a fracture toughness of 6.2 MPa m1/2, hardness of 25.3 GPa, Weibull modulus of 17, and a strength of 423 MPa.