Metal-organic Chemical Vapor Deposition of Environmental Barrier Coatings for All-Oxide Ceramic Matrix Composites

All-oxide ceramic matrix composites (CMCs) are promising candidates for structural components in key high-temperature applications, e. g. gas turbines and jet engines. Although inherently oxidation resistant, these materials are prone to corrosive attack by water vapor and other species in the combustion atmosphere. This drawback can be overcome by environmental barrier coatings (EBC) produced via metal-organic chemical vapor deposition (MOCVD), currently being under investigation at IOT. MOCVD is a convenient route to produce coatings at intermediate vacuum conditions with high deposition rates (up to 100 microns/h) and particularly advantageous for coating of complex shaped substrates. EBCs based on yttrium-aluminates are considered to exhibit high corrosion resistance in hot gas environment. WHIPOX-type CMCs provided by DLR were coated by MOCVD using yttrium- and aluminum-beta-diketonates. Prior to EBC deposition a bond coat was applied to substrate surfaces in order to assure good adhesion and uniform layer thickness. The coating thickness, crystallinity and morphology were characterized by x-ray diffraction and scanning electron microscopy.