Effect of microstructure on the mechanical properties of liquid-phase-sintered silicon carbide at pre-creep temperatures

The effect of the microstructure on the mechanical properties of pressureless, liquid-phase-sintered (LPS) α-SiC ceramics above room-temperature was studied. LPS-SiC ceramics were fabricated with different microstructural features (grain size and morphology, and content of the intergranular phase), and their mechanical behaviour under contact stresses was evaluated by high temperature Hertzian testing (HTHT) from room temperature up to the creep temperature (1000 °C). The amount of intergranular phase was found to control the elasto-plastic properties of LPS-SiC at intermediate temperatures. Grain size and morphology had a significant influence only on toughness, since the crack bridging mechanism was enhanced by elongated grains, the more so the larger their size. Implications of these results for the design and fabrication of LPS-SiC ceramics with tailored contact-mechanical properties are discussed.