A ZrC–SiC/SiC multilayer anti-ablation coating for ZrC modified C/C composites

To improve ablation resistance of ZrC modified C/C composites fabricated by precursor infiltration and pyrolysis process, a multilayer coating with ZrC–SiC outer layer and SiC inner layer was prepared on the composites by supersonic atmosphere plasma spraying combined with pack cementation. The bonding strength and ablation property of the coated composites were studied by tensile adhesive method and oxyacetylene flame, respectively. The results showed that the bonding strength of the coating was greater than 10.65 MPa as the fracture occurred in the ZrC modified C/C composites. After ablation for 120 s, the linear and mass ablation rates of the composites were 0.28 × 10⁻³ mm/s and 0.01 × 10⁻⁴ g/s, respectively. The evolution of the coating during ablation was as follows: ZrO₂–SiO₂ binary eutectic, melted ZrO₂ layer, grainy ZrO₂ connected by ZrO₂–SiO₂ eutectic, dense sintering ZrO₂ scale, and forming glass-like SiO₂ after sintering ZrO₂ failure. The outer ZrC–SiC layer could provide protection to the modified composites for 60s under oxyacetylene flame, and the inner SiC coating can continue to protect the composites by forming SiO₂ glass-like coating for another 60s.