Steam oxidation of chromium corrosion barrier coatings for sic-based accident tolerant fuel cladding

SiC-based materials are currently being considered for accident tolerant fuel (ATF) cladding, however, there are concerns regarding hydrothermal corrosion rates and hermeticity. These issues may be addressed with the utilization of a Cr corrosion barrier coating (CBC) but the interaction of Cr with SiC under loss of coolant accident (LOCA) conditions needs to be investigated. In the present work, Cr coatings were deposited onto chemically vapor deposited (CVD) SiC with either high power impulse magnetron sputtering (HiPIMS), cathodic arc (CA), or a combination of both. Annealing and steam thermogravimetric analysis (TGA) was used to study reaction product formation with and without oxidation. After 1200 degrees C annealing, formation of a CrxCy carbide layer at the ambient interface and a CrxSiyCz silicide layer at the SiC interface was observed. After 1200 degrees C TGA exposure, similar carbide and silicide layers were observed but with a Cr2O3 outer reaction layer and a Si and O rich interfacial layer forming between the carbide and silicide layers. Initial mass gain of the coatings during the 1200 degrees C TGA exposure was parabolic and were similar to reported rates of chromia formation. Mass gain behavior and observed transitions in chromia microstructure indicate that metallic Cr may be consumed within the first similar to 1 h at 1200 degrees C and that subsequent chromia formation occurs at the expense of the underlying Cr carbide layer. Overall, the results show no detrimental impact of Cr coatings on the steam oxidation resistance of SiC up to 4 h at 1200 degrees C. (C) 2020 Elsevier B.V. All rights reserved.