Effect of the Y₂O₃ addition on the microstructure and ablation behavior of C/C-ZrC-SiC composites with in-situ formed Y-doped ZrC-SiC-ZrSi₂ coating

In this work, C/C-ZrC-SiC composites with in-situ formed Y-doped ZrC-SiC-ZrSi₂ coatings were fabricated via reactive melt infiltration (RMI), with varying Y₂O₃ contents (5 wt%, 10 wt%, and 15 wt%). The influence of Y₂O₃ doping on phase composition, microstructure, and ablation behavior was systematically investigated under oxyacetylene flame conditions. Among all samples, the composite with 10 wt% Y₂O₃ exhibited the most favorable ablation performance, achieving mass and linear ablation rates of −0.88 ± 0.11 mg/s and − 1.28 ± 0.11 μm/s, respectively. The enhanced performance is primarily attributed to the formation of a thermally stable, partially stabilized ZrO₂ phases and a robust, hierarchical oxide architecture that effectively inhibits oxygen ingress and thermal degradation. In contrast, both insufficient and excessive Y₂O₃ additions resulted in microstructural defects detrimental to ablation resistance. These findings demonstrate that optimized Y₂O₃ doping effectively tailors phase stability and structural integrity of ZrC-based coatings, offering a promising route for developing advanced thermal protection materials.