Evolution of microstructural feature and oxidation behavior of LaB₆-modified MoSi₂-SiC coating

LaB₆-modified MoSi₂-SiC (MSL) oxidation resistant coating was designed and successfully fabricated on SiC-coated carbon/carbon (C/C) composites using efficient supersonic atmospheric plasma spraying (SAPS) method. The MSL coating protected the C/C composites from static oxidation at 1773 K for 100 h with a mass loss of 6.52 mg cm⁻² and dynamic ablation about 2023 K for six cycles with a mass loss of 29.86 mg cm⁻², which was superior to the MoSi₂-SiC (MS) coating without La-doping. The presence of rare earth La element promoted the liquid phase sintering of MoSi₂ and B element facilitated the high-temperature stability of SiO₂-rich glass scale, resulting in the formation of La-Si-O-B compound scale with a low volatility and oxygen permeability cover the coating surface, which contributed to improving the resistant to oxidative response of the MSL coating.