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

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.