SiC/HfC/SiC ablation resistant coating for carbon/carbon composites

To improve the ablative resistance of carbon/carbon (C/C) composites, a SiC/HfC/SiC coating was prepared by a multi-step technique of diffusing reaction and chemical vapor deposition. The microstructure and morphology of the coatings were characterized by Scanning Electron Microscopy, X-ray diffraction. The coated C/C exhibits good ablation resistance. A compact glassy HfO2 layer was obtained on the coating surface after ablation, which can efficiently prevent C/C composites from ablation. Meanwhile, the outer SiC coating provides positive protection; Weight loss of the coated samples is only 2.3% after oxidation at 1500 °C for 66 h. HfSiO4 was formed during oxidation and characterized by a stable glassy phase which could protect C/C composites from oxidation.

► The SiC/HfC/SiC coating exhibited high ablation resistance.
► HfO2 glassy layer formed after ablation.
► HfSiO4 was generated after oxidation at 1500.
► The outer SiC coating ensured HfC good coating stability.