Zirconium‐Based High Emissivity Multilayer Coating for Carbon/Carbon Composite With Enhanced Ablation Resistance

A multilayer coating system was developed as an ablation and thermal protection measure for C/C composites. The multilayer coating architecture consists of SiC, ZrB 2 ‐SiC (ZBS), and ZrC‐ZrO 2 (ZZC) sublayers with a Sm 2 O 3 ‐ZrO 2 (SZC) topcoat. The as‐sprayed coating microstructure demonstrated well‐defined adhesion between the layers and the composite without forming major voids or cracks. Coatings with individual sublayer thicknesses of ∼100 µm demonstrated excellent ablation resistance at a maximum surface temperature of ∼2100°C. The ablated multilayer coating microstructure exhibited a dense topcoat that effectively acted as a physical and thermal barrier. The ZBS and ZZC sublayers remained physically and chemically unaffected and maintained their integrity throughout the high heat flux ablation testing period. The topcoat demonstrated a maximum spectral emissivity of 0.99 at 1200°C, contributing to improved thermal radiation efficiency for applications to include hypersonic re‐entry.