Ablation behavior of coating-matrix integrated C/C–SiC-HfC-ZrC composites in plasma wind tunnel

Coating-matrix integrated C/C–SiC-HfC-ZrC composites were fabricated via RMI using HfSi₂-ZrSi₂ hybrid alloys and slurry brushing. The composite featured a borosilicate glass outer layer and a continuous in-situ (Zr, Hf)Si₂-(Hf, Zr)C–SiC coating integrated with the matrix. In a plasma wind tunnel at 5.0 MW/m² and 7.0 kPa, the composite exhibited a linear ablation rate of −2.30 × 10⁻³ mm/s and a mass ablation rate of 4.90 × 10⁻⁴ g/s. The coating debonded from the substrate during ablation caused by thermal mismatch and the escape of gaseous products, but effectively blocked heat, flow, and oxygen, protecting the substrate. Surface (Hf, Zr)O₂ densified via quasi-liquid-phase sintering, with liquid-phase dissipation, temperature surge, and transverse crack inside coating formation. Gaseous product evolution, SiO₂ flow, and temperature gradients promoted columnar (Hf, Zr)O₂ growth, retarding atomic oxygen erosion. Under harsher conditions (6.0 MW/m², 9.0 kPa), the surface temperature exceeded 2800 °C, causing oxide melting, coating degradation, and severe substrate oxidation.