MICROSTRUCTURE AND MECHANICAL-PROPERTIES OF HOT-PRESSED SIC-TIC COMPOSITES

Hot-pressed SiC-TiC composite ceramics with 0-100 wt % TiC have been investigated to determine the effect of composition (amount of TiC) on the elastic modulus, hardness, flexural strength and fracture toughness, K(IC). The composites exhibited superior mechanical properties compared to monolithic SiC and TiC, especially in fracture toughness, K(IC), value for 30-50 wt % TiC composite. The maximum values of K(IC) and room-temperature flexural strength were 6 MPa m1/2 for a 50 wt % TiC and 750 MPa for a 30 wt % TiC composite, respectively. The observed toughening could be attributed to the deflection of cracks due to dispersion of the different particles. Although no third phases were detected by both TEM and XRD studies, an EDAX study and resistivity measurements indicated some possibility of solid solutions being present. The composites containing more than 30 wt % TiC, exhibited resistivity lower than 10(-3) OMEGA cm which is favourable for electro-discharge machining of ceramics.