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Laser surface treatment of amorphous Ti-Al-C (50:25:25 at.%) coating deposited on Zircaloy-4 substrate by dc magnetron sputtering was parametrically investigated as a function of surface temperature and dwell time. The as-deposited coating was transformed to crystalline Ti 2 AlC without significant phase alteration of Zircaloy-4 substrate under optimized conditions (900 °C for 3 second). Thermal analysis via commercial finite element software was applied to guide the selection of parameters for laser surface treatment. Coating performance was evaluated with wear and scratch tests as well as high temperature steam oxidation tests. Although laser treatment led to the formation of microcracks, it was noted to improve the mechanical integrity of the coatings and the oxidation tests indicated the protective nature of the as-deposited and laser-annealed coatings. The oxide particulate morphology and size formed during the steam oxidation tests varied dramatically between the as-deposited and laser-annealed coatings.

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Fuel Cladding Chemical Interactions (FCCI) in a nuclear reactor occur due to thermal and radiation enhanced inter-diffusion between the cladding and fuel materials, and can have the detrimental effects of reducing the effective cladding wall thickness and the formation of low melting point eutectic compounds. Deposition of diffusion barrier coatings of a thin oxide on the inner surface of the cladding can potentially reduce or delay the onset of FCCI. This study examines the feasibility of using nanofluid-based electrophoretic deposition (EPD) process to deposit coatings of titanium oxide, yttria-stabilized zirconia (YSZ) and vanadium oxide. The deposition parameters, including the nanofluid composition, current, and voltage were optimized for each coating material using test flat substrates of T91 ferritic-martensitic steel. Diffusion characteristics of the coatings were investigated by diffusion couple experiments using the fuel surrogate cerium. These diffusion couple studies performed in the temperature range of 560°C and 585°C showed that the oxide coatings significantly reduce the solid state inter-diffusion between cerium to steel.

A coordinated effort to link advanced materials characterization methods and computational modeling approaches is critical to future success for understanding and predicting the behavior of reactor materials that operate at extreme conditions. The difficulty and expense of working with nuclear materials have inhibited the use of modern characterization techniques on this class of materials. Likewise, mesoscale simulation efforts have been impeded due to insufficient experimental data necessary for initialization and validation of the computer models. The objective of this research is to develop methods to integrate advanced materials characterization techniques developed for reactor materials with state-of-the-art mesoscale modeling and simulation tools. Research to develop broad-ion beam sample preparation, high-resolution electron backscatter diffraction, and digital microstructure reconstruction techniques; and methods for integration of these techniques into mesoscale modeling tools are detailed. Results for both irradiated and un-irradiated reactor materials are presented for FY14-FY16 and final remarks are provided.