Reactive ZrB 2 -induced oxidation resistance and kinetics in (Zr,Ti,W)C-based ceramics at 1000°C–1100°C

Abstract

This study systematically investigates the high-temperature oxidation behaviour of (Zr,Ti,W)C-Me _x B _y multiphase ceramics fabricated by spark plasma sintering, focusing on their performance in static air at 1000°C–1100°C (operating temperature range for divertor components in nuclear fusion devices). The oxide layers consist predominantly of t-TiO₂, m-ZrO₂ and (Ti, Zr)O₂/(Zr,Ti)O₂ solid solutions. At 1000°C, oxidation follows parabolic kinetics, suggesting diffusion-controlled growth. At 1100°C, linear kinetics prevail as enhanced volatilisation of WO₃ and B₂O₃ leads to porous microstructures. The outer oxide layer develops voids due to WO₃ sublimation, while the inner layer remains dense owing to B₂O₃ filling the pores and cracks. The multiphase oxide structure, comprising (Zr,Ti)O₂ and (Ti,Zr)O₂ solid solutions along with dispersed ZrO₂ and TiO₂ particles, substantially enhances the oxidation resistance. The incorporation of ZrB₂ significantly increases the apparent activation energy of oxidation from 13.3641 kJ/mol (TW) to 47.4178 kJ/mol (TW60ZB), representing a 355% improvement in oxidation resistance. The key mechanisms include prolonged oxygen diffusion paths due to low-diffusivity ZrO₂ regions, grain boundary pinning by interphase boundaries and microstress fields at TiO₂/ZrO₂ interfaces that deflect microcracks. These results demonstrate the promising potential of (Zr,Ti,W)C-Me _x B _y ceramics for high-temperature applications such as nuclear fusion divertor components.