Densification, microstructure, and mechanical properties of ZrC-SiC ceramics

ZrC-SiC ceramics were fabricated by high-energy ball milling and reactive hot pressing of ZrH2, carbon black, and varying amounts of SiC. The ceramics were composed of nominally pure ZrC containing 0 to 30 vol% SiC particles. The relative density increased as SiC content increased, from 96.8% for nominally pure ZrC to 99.3% for ZrC-30 vol% SiC. As SiC content increased from 0 to 30 vol%, Young's modulus increased from 404 +/- 11 to 420 +/- 9 GPa and Vickers hardness increased from 18.5 +/- 0.7 to 23.0 +/- 0.5 GPa due to a combination of the higher relative density of ceramics with higher SiC content and the higher Young's modulus and hardness of SiC compared to ZrC. Flexure strength was 308 +/- 11 MPa for pure ZrC, but increased to 576 +/- 49 MPa for a SiC content of 30 vol%. Fracture toughness was 2.3 +/- 0.2 MPa center dot m(1/2) for pure ZrC and increased to about 3.0 +/- 0.1 MPa center dot m(1/2) for compositions containing SiC additions. The combination of high-energy ball milling and reactive hot pressing was able to produce ZrC-SiC ceramics with sub-micron grain sizes and high relative densities with higher strengths than previously reported for similar materials.