Evolution of microstructure and thermal conductivity of multifunctional environmental barrier coating systems
نویسندگان
چکیده
Environmental barrier coating (EBC) systems are applied to the surface of silicon-based composites exposed high temperature combustion gas flow paths in turbine engines. They reduce rate composite oxidation, its volatilization by reactions with water vapor, and as their thermal conductivity decreases. Current EBC consist a silicon bond coat covered an ytterbium disilicate (Yb2O3?2SiO2: YbDS) permeation resistant low silica activity barrier. When atmospheric-plasma spray deposition, this outer layer contains 10–15% secondary monosilicate (Yb2O3?3SiO2: YbMS) phase. YbDS has coefficient expansion (CTE) 4–5×10?6 °C?1, similar those composite, but relatively 5–7 W m?1 K?1. YbMS higher steam volatility resistance than YbDS, it much lower (?2–2.5 K?1) at ambient compared higher, highly anisotropic CTE (3–11×10?6 °C?1) results channel cracking which reduces environmental protection. Here, we use combination scanning electron beam laser-based thermoreflectance methods spatially map distribution silicate phases Si-ytterbium system cycling vapor. We show that during cycling, diffusion from thermally grown oxide on Si nearby regions transforms phase thereby reducing risk thermomechanical failure decreasing effective resistance. also is volatilized vapor–ytterbium interface, transformed YbMS, restoring some protection lost reduction thickness transformation near coat.
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ژورنال
عنوان ژورنال: Materials Today Physics
سال: 2021
ISSN: ['2542-5293']
DOI: https://doi.org/10.1016/j.mtphys.2020.100304