Effect of TiC Reinforcement on Densification, Structural Evolution and High-Temperature Oxidation Behaviour of ZrB2-20 vol pct SiC Composite

Abstract

This study aims to develop a novel TiC-doped ZrB2-SiC-TiC composite with enhanced sinterability, densification, phase and microstructural stability and oxidation resistance for high-temperature structural application. Due to 5 vol pct TiC addition, higher sintered density (99.6 pct) was obtained by spark plasma sintering (SPS) at 1700 degrees C, which is about 200 degrees C less than the SPS processing temperature needed for ZrB2-20 vol pct SiC. The improved sinterability was ascribed to in-situ formation of (Zr,Ti)B-2 solid solution in this new ZrB2-20 vol pct SiC-5 vol pct TiC composite. The effect of TiC addition on oxidation kinetics of ZrB2-SiC composites was critically evaluated. Consequent upon oxidation at 1600 degrees C for 0-240 minutes in static air, relatively low mass gain and thin oxide layer was observed in the TiC-containing composite. Phase and microstructural analyses of the oxidized samples revealed the formation of a protective oxide scale in both composites. Interestingly, the thickness of SiC-depleted region was found to be much lower in ZrB2-SiC-TiC composite, compared to that of ZrB2-SiC binary system.