La₂O₃ stabilized WB₂-SiC composites with remarkable ablation resistance up to 2273 K

The pure phase and ultrafine WB₂ powders were successfully synthesized using a liquid phase precursor synergized with boro/carbothermal reduction method. Subsequently, dense WB₂-SiC composites (99.5 %) were fabricated through hot pressing sintering. The effects of La₂O₃ additive on the densification, mechanical properties, and ablation resistance of WB₂-SiC composites were systematically investigated. The ablation behavior of the composites was evaluated using a plasma flame. The results indicate that the mass ablation rate of WB₂-SiC-La₂O₃ is 0.463 mg/s, and the linear ablation rate is 0.311 μm/s when exposed to a 2273 K plasma flame for 60 s. The excellent ablation resistance is attributed to the reaction between La₂O₃ and SiO₂ at high temperature, which generates La₂Si₂O₇, effectively pinned in the glassy phase to inhibit the volatilization of B₂O₃. Furthermore, La₂O₃ also reacts with B₂O₃ and SiO₂ to generate a highly viscous B-Si-O-La protective layer, which blocks the ingress of oxygen.