A Multilayer SiC/ZrB2/SiC Ablation Resistance Coating for Carbon/Carbon Composites

To improve the ablation resistance of carbon/carbon (C/C) composites, a new SiC/ZrB₂/SiC multilayer coating is designed and fabricated by a three-step method of pack cementation, supersonic plasma spraying, and low pressure chemical vapor deposition. In this study, ablation behavior of SiC/ZrB₂/SiC coating is investigated under oxyacetylene torch environment. Oxyacetylene ablation testing results show that the linear ablation rate and mass ablation rate of SiC/ZrB₂/SiC coated C/C composites are only −5.0 × 10⁻⁴ mm s⁻¹ and −9.6 × 10⁻⁴ g s⁻¹, respectively, for 20 s ablation under heat flux of 2400 kW m⁻². However, the ablative linear rate of ZrB₂/SiC coated C/C composites is 7.5 × 10⁻⁴ mm s⁻¹ and the ablative mass rate is zero. The better ablation resistance is mainly attributed to a molten SiO₂–ZrO₂ hybrid glassy layer formed after ablation on the surface of the composites and acting as thermal barrier layer inhibiting inward diffusion of oxygen.