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High reflectance thermal barrier coatings consisting of 7% Yittria‐Stabilized Zirconia (7YSZ) and Al2O3 were deposited by co‐evaporation using electron beam physical vapor deposition (EB‐PVD). Multilayer 7YSZ and Al2O3 coatings with fixed layer spacing showed a 73% infrared reflectance maxima at 1.85 μm wavelength. The variable 7YSZ and Al2O3 multilayer coatings showed an increase in reflection spectrum from 1 to 2.75 μm. Preliminary results suggest that coating reflectance can be tailored to achieve increased reflectance over a desired wavelength range by controlling the thickness of the individual layers. In addition, microstructural enhancements were also used to produce low thermal conductive and high hemispherical reflective thermal barrier coatings (TBCs) in which the coating flux was periodically interrupted creating modulated strain fields within the TBC. TBC showed no macrostructural differences in the grain size or faceted surface morphology at low magnification as compared with standard TBC. The residual stress state was determined to be compressive in all of the TBC samples, and was found to decrease with increasing number of modulations. The average thermal conductivity was shown to decrease approximately 30% from 1.8 to 1.2 W/m‐K for the 20‐layer monolithic TBC after 2 h of testing at 1316°C. Monolithic modulated TBC also resulted in a 28% increase in the hemispherical reflectance, and increased with increasing total number of modulations.

In an attempt to develop an accident-tolerant fuel (ATF) that can delay the deleterious consequences of loss-of-coolant-accidents (LOCA), multilayer coatings were deposited onto ZIRLO ® 1 coupon substrates by cathodic arc physical vapor deposition (CA-PVD). Coatings were composed of alternating TiN (top) and Ti 1-x Al x N (2-layer, 4-layer, 8-layer and 16-layer) layers. The minimum TiN top coating thickness and coating architecture were optimized for good corrosion and oxidation resistance. Corrosion tests were performed in static pure water at 360º C and 18.7 MPa for up to 90 days. The optimized coatings had no spallation/delamination and had a maximum of 6 mg/dm² weight gain, which is 6 times smaller than that of a control sample of uncoated ZIRLO ® which showed a weight gain of 40.2 mg/dm². The optimized architecture features a ~1µm TiN top layer to prevent boehmite phase formation during corrosion and a TiN/TiAlN 8-layer architecture which provides the best corrosion performance.

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Electron beam‐physical vapor‐deposited thermal barrier coatings (TBC) are susceptible to damage due to environmental contaminants such as calcium–magnesium–aluminum–silicon oxide systems (CMAS). This paper discusses various approaches of modifying TBC for enhanced protection against CMAS attack. Methodologies were explored with various coating systems maintaining functionality as nonwetting, sacrificial, and impervious to CMAS attack. In the brief isothermal (1260°C/10 min) tests, a nearly crack‐free and reglazed Pd coating provided substantial protection from the CMAS attack. Approaches that provided some minor improvements need further optimization to better assess their viability.

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