Study on the ablation resistance of ZrB2-SiC-LaSi2 coating prepared on the C/C composites

To improve the ablation resistance of C/C composites above 1800 degrees C, ZrB2-SiC coating and ZrB2-SiC-LaSi2 coating were prepared on the surface of C/C composites by atmospheric plasma spraying (APS). The micro-structure, composition evolution and ablation resistance of the coatings were studied. First-principle calculations were used to analyze the ablation mechanism. The results showed that addition of LaSi2 could improve the density and ablation resistance of ZrB2-SiC coatings. LaSi2 could produce more protective Si-O-La sealing phase and form high melting point compounds which stabilize the sealing phase and help improve the ablation resistance of ZrB2-SiC coatings.