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 x 10(-3) mm/s and 0.01 x 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.