Synthesis and Characterization of Thin Film Fealcr for High Temperature Corrosion Applications

In the Fukushima nuclear disaster, the backup diesel power generator for the cooling pumps
failed causing the Zircaloy cladding that covered the fuel rods to rapidly undergo steam oxidation
producing a combustible mixture of hydrogen gas. The resulting explosion resulted in the uncontrolled
release of radioactive materials into the atmosphere, which has stimulated intense interest in the
development of novel oxidation resistant cladding materials. If the cladding material were to more
actively resist oxidation in the presence of high temperature steam the amount of hydrogen produced
would be reduced, mitigating the risks of forming explosive mixtures. Recent studies have shown that
FeCrAl is a promising alloy system for resisting Zercaloy oxidation under high temperature when used in
bulk. However, replacing the entire fuel cladding for every nuclear reactor in the United States is a time
consuming and cost prohibitive measure.
Here we perform feasibility studies for the use of FeCrAl thin-film coatings as short-term
oxidation barriers for the Zircaloy in high temperature environments. Such coatings could be deposited
on top of the existing Zircaloy cladding materials to reduce overall cost compared to replacing the whole
unit. To evaluate the effect of different compositions of FeAlCr on oxidation resistance, composition
spread samples within the region of the Fe-Cr-Al phase on the FeCrAl ternary phase diagram were
oxidized up to 6 hour 1323K. The films were synthesized through magnetron sputtering and the
temporal dynamics of oxide growth and metallographic phase were characterized as a function of
composition through Raman spectroscopy and in-situ synchrotron diffraction. The role of composition,
processing, and crystal structure on the type of surface oxide formed at 1323K will be discussed.