Response behavior and optimization strategy of UHTC–SiC dual‐layer coatings under high heat flux ablation environments

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Abstract With more stringent requirements on assessment temperatures and ablation time, traditional ultrahigh temperature ceramic (UHTC)–SiC dual‐layer coating design for C/C composites is at risk of structural failure and reduced service reliability. Herein, as‐designed C/C composites with [HfC/ZrC/HfC]–SiC dual‐layer coatings were tested under three different ablation temperatures (2300°C, 2600°C, 2700°C). The increase in temperature resulted in a significant change in linear ablation rates, ranging from −0.17 µm/s (2300°C) to −34.15 µm/s (2700°C). Based on experiments and finite element analysis (FEA), the primary coating failure mechanism, when the ablation temperature was raised to 2700°C, was attributed to high temperature on the SiC transition layer (>2230°C), leading to rapid escape of gaseous SiO and CO from SiC active oxidation. A new, integrated design that forms a ZrC–SiC transition layer (between UHTC layer and C/C composites) demonstrated the ability to resist high heat flux oxyacetylene flame with low ablation rate (−1.70 µm/s, 90 s) and maintained sufficient interface stability at an assessment temperature of ∼2700°C. This work provides new insights and might help guide design of future antioxidation coatings and their assessment methods.