Microstructure evolution and oxidation resistance of CaO-Al2O3-SiO2/ZrO2-borosilicate multilayer coating for C/C composites

•The multilayer glass coating was prepared by slurry method.•The multilayer design could decrease the stress concentration and improve self-healing ability.•The oxidation resistance increased with the temperature.•The multilayer coating can effectively seal the samples when it oxidizes at 1073–1273 K. CaO-Al2O3-SiO2/ZrO2-borosilicate (CAS/BG) multilayer glass coating was prepared by slurry method on carbon fiber reinforced carbon matrix (C/C) materials to improve their anti-oxidation ability. The weight loss ratio of coated C/C samples were 21.70 %, 1.63 %, 0.035 % respectively after 50 h oxidation at 1073 K, 1173 K, 1273 K, and the samples had excellent mechanical properties remaining. Compared to single BG layer samples, the added outer CAS layer could effectively inhibit gases diffusing by sealing and healing defects. The increased anti-oxidation property with the temperature was mainly attributed to the improved healing ability from glass flow and thermal expansion.