A novel (Hf1/3Zr1/3Ti1/3)C medium-entropy carbide coating with excellent long-life ablation resistance applied above 2100 °C

Compared to conventional monocarbides, the oxides of medium/high-entropy carbides (M/HECs) expressed excellent antioxidant resistance and high-temperature structural stability, which are great potential to improve the oxidation/ablation resistance of carbon/carbon (C/C) composites. M/HECs ceramics coated C/C composites are ideal long-term ablation-resistant structural materials applied in ultra-high-temperature (above 2100 °C) and oxygen-containing environments. This work reported a novel MEC (Hf1/3Zr1/3Ti1/3)C coating first prepared on SiC-coated C/C composites. The fabricated MEC coating significantly prolonged the anti-ablation time (more than 210 s) above 2100 °C in an oxyacetylene flame ablation environment with a heat flux of 2.4 MW/m2, compared to monocarbide coating (less than 90 s). The ablated surface of MEC coating was composed of amorphous Zr–Hf–Ti–C–O oxycarbide pinned by m-(Hf, Zr, Ti)O2 nanoparticles, forming a unique structure of oxide scale for long-term ablation resistance. This work provides a new way to improve the ablation resistance of monocarbide coatings and develops a great promise for new-generation structural materials at ultra-high temperature environments.