The ablation behavior and mechanical property of C/C-SiC-ZrB₂ composites fabricated by reactive melt infiltration

In order to improve the ablation resistance of carbon/carbon (C/C) composites, SiC-ZrB₂ di-phase ceramic were introduced by reactive melt infiltration. The ablation properties of these composites were evaluated by oxyacetylene torch with a heat flux of 2.38 MW/m² for 60 s. Compared with the pure C/C composites, the C/C-SiC-ZrB₂ composites show a significant improvement in the ablation resistance, and the linear and mass ablation rates decreased from 10.28×10⁻³ mm/s to 6.72×10⁻³ mm/s and from 3.08×10⁻³ g/s to 0.61×10⁻³ g/s, respectively. After ablation test, the flexural strength retentions of the C/C and C/C-SiC-ZrB₂ composites near the ablated center region are 39.7% and 81.6%, respectively. The higher strength retention rate of C/C-SiC-ZrB₂ composites was attributed to the introduction of SiC-ZrB₂ ceramic phases, which have excellent ablation resistant property. During ablation test, an ‘embedding structure’ of Zr-O-Si glass layer was formed, which could act as an effective barrier for oxygen and heat. The oxide ceramic coating could protect the C/C-SiC-ZrB₂ composites from further ablation, and thus contribute to retaining the mechanical property of C/C-SiC-ZrB₂ composites after ablation.