Enhanced oxidation resistance of Yb2O3-HfB2-SiC/SiC coatings for protecting C/C composites at 1973 K

To enhance oxidation resistance of carbon/carbon (C/C) composite materials at 1973 K in static air, a novel bilayer Yb 2 O 3 -HfB 2 -SiC/SiC (denoted YHSS) coatings were engineered via a two-step process combining pack cementation and slurry method. A substantial loading of ceramic phases (∼60 wt %) was incorporated into the SiC ceramic layer to improve thermal stability of the oxide scale at 1973 K. Following pre-oxidation, the YHSS coatings impart effective oxidation protection to C/C composite materials for over 228 h at 1973 K. Coupled experimental and theoretical analyses confirm that Yb and Hf atoms diffuse into the thermally grown SiO 2 layer, thereby reinforcing the SiO 2 network structure. Furthermore, the coating's exceptional performance is attributed to its dense, flaw-free surface morphology and the homogeneous dispersion of high-content ceramic phases throughout the SiC layer, collectively suppressing oxygen permeation.