Preparation and water-vapour corrosion behaviour of BSAS environmental barrier coatings fabricated on ceramic matrix composites

Environmental barrier coatings (EBCs) are commonly utilized to protect ceramic matrix composite components from water vapour attacks in commercial gas turbine engines. In this work, Si/3Al₂O₃·2SiO₂ (Mullite)/BaO-SrO-Al₂O₃-SiO₂ (BSAS) tri-layered EBCs were fabricated on SiC-based ceramic matrix composites (CMC) substrate via atmospheric plasma spraying technique. The phase composition, microstructure, and bond strength of the environmental barrier coatings were studied by scanning electron microscope, energy dispersive spectrometer, X-ray diffraction analyzer, and mechanical test machine. The water vapour resistance of the BSAS coating and CMC was evaluated with a self-assembled water-vapour corrosion test device. The results indicate that the as-sprayed BSAS coating with a porosity of (5.9 ± 0.8) % mainly comprises the monoclinic celsian BSAS phase, hexacelsian BSAS phase, and SiO₂ phase. The consumption velocity of the BSAS coating is about 12 % that of the naked CMC material in a 1300 °C water vapour environment. After corrosion for 300 h, the average flexural strength of naked samples was (481 ± 9) MPa, which was about 64 % of the coated ones. In addition, the bond strength of the as-sprayed coating is (18.7 ± 1.6) MPa. Even after 300 h of water vapour corrosion, the bond strength of the coating does not decay. Evidently, BSAS coating can protect CMC materials from water vapour corrosion at 1300 °C.