An Investigation on the Effect of TiC Additive on the Microstructural and Mechanical Properties of Ultra-High Temperature ZrB2-SiC-Based Ceramic Composite by Multi-Step Spark Plasma Sintering Method

This study investigates the fabrication and characterization of an ultra-high temperature ceramic composite based on ZrB2-20 vol. % SiC using the spark plasma sintering method with a multi-step technique. Sintering of ZrB2 poses challenges due to its covalent nature and high sintering temperature. Adding up to 20 vol. % SiC has shown significant improvement in the sintering process and mechanical properties of the ZrB2-based composite. Therefore, the effect of adding TiC in the range of 0 to 15 vol. % on the microstructural and mechanical properties of the composite was investigated at a temperature of 1800°C and a pressure of 30 MPa. The results indicated that the sintering process and particle bonding start at a temperature of 1600°C and continue up to 1800°C, with densification being controlled by grain boundary diffusion at this temperature. Adding up to 10 vol. % TiC to the ZrB2-SiC composite and sintering at 1800°C for 5 minutes resulted in the formation of (Zr,Ti)B2 and (Ti,Zr)C solid solutions in the matrix and reactions with surface oxides of ZrB2 powder such as ZrO2 and B2O3. These changes led to a 15% increase in relative density and improvements in mechanical properties, including hardness (14%), elastic modulus (12%), fracture strength (20%), and fracture toughness (8%). However, increasing the TiC content from 10 to 15 vol. % resulted in a noticeable decline in the mechanical properties and crystallite size of the composite.