Role of TiC and WC Addition on the Mechanism and Kinetics of Isothermal Oxidation and High-Temperature Stability of ZrB2-SiC Composites

This study investigates the influence of separate and combined addition of 5 vol.% TiC and/or WC on the isothermal oxidation behaviour of ZrB2-20 vol.% SiC composites consolidated by a spark plasma sintering route. The oxidation performance of the composites was evaluated in the temperature range of 1500-1600 degrees C in air for up to 4 h. Following oxidation, the samples were subjected to a detailed characterization of the microstructure, micro-composition, phase aggregate, and oxide scale growth kinetics. The thermodynamic feasibility of probable reactions and the phase stability of Zr-B-O, Zr-Si-O, Ti-B-O, Ti-C-O, Ti-W-O, and W-C-O systems were examined by dedicated software. While addition of TiC or WC was found to result in protective oxide scale formation, the highest oxidation resistance in terms of reduced mass gain and oxide layer thickness was offered by ZrB2-20SiC-2.5TiC-2.5WC (vol.%) composite at 1500-1600 degrees C in air.