High-temperature oxidation resistance of SiCf/SiC composites annealed and cladded with LaMgAl11O19/Yb2Si2O7 thermal/environmental barrier coatings

SiCf/SiC composites were annealed at 1300oC for 5h in argon and then fully cladded by LaMgAl11O19/Yb2Si2O7 (LMA/YbDS) thermal/environmental barrier coatings (T/EBCs). The annealed and coated system, directly-coated one and non-coated composites were isothermally oxidized at 1350oC for 300h. The oxidation resistance was estimated by strength retention rates. Compared to serious strength degradation in the non-coated composites, high strength retention rates were obtained for the coated ones, indicating LMA/YbDS provided effective protection for SiCf/SiC. Additionally, the annealed and coated system had higher strength retention rates than directly-coated one, resulting from weakened interfacial bonding strength between SiC matrix and fibers.