AVS 50th International Symposium
    Advanced Surface Engineering Tuesday Sessions
       Session SE-TuA

Paper SE-TuA8
Surface Alloying of Aluminum Films by Electron Beam Evaporation on Zirc-4 Substrates and Hydrothermal Crystal Growth in Sub-critical Condition

Tuesday, November 4, 2003, 4:20 pm, Room 323

Session: High Temperature Protective Coatings
Presenter: S.T. Park, University of Florida
Authors: S.T. Park, University of Florida
R.H. Baney, University of Florida
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Waterside corrosion of the Zircaloy cladding encasing the uranium oxide pellets is one of the primary factors limiting high "burn up" of nuclear fuel in pressurized water reactor (PWR) nuclear reactors. High "burn up" can significantly impact plant safety and economics. This research has been performed to develop ceramic coating corrosion protection system. Aluminum films were deposited on Zircaloy substrates by electron-beam evaporation and surface-alloyed by controlled oxidation at near the melting temperature of aluminum. Two different oxidation procedures were employed to make compositional gradient compound layers. These gradient compound layers can increase the corrosion resistance and minimize the interface defects like grain boundaries that can occur in multilayer coatings. The substrate surface roughness, aluminum film thickness, and air oxidation time and temperature were varied. The durability of films was tested through the use of an autoclave test in sub-critical condition that is the same condition as in actual PWR. The samples were then evaluated to determine the film condition. Deposited films were characterized for morphology and elemental composition using field emission scanning electron microscopy (FE SEM), energy dispersive x-ray analysis (EDX), and auger electron spectroscopy (AES). AES analysis of the oxidized coatings showed that gradient compositions were obtained as expected, with Al, Zr, and O content varying through the coating thickness. Glancing angle x-ray diffraction (GAXRD) analysis also showed that variety of intermetallic and oxide phases (such as Al@sub 3@Zr, Al@sub 2@Zr@sub 3@, Al@sub 2@O@sub 3@, ZrO@sub 2@ and Zr@sub 3@O) were formed in the coatings during processing. Hydrothermal growth of well-faceted particulates was observed after autoclave test. They were identified to be hydrothermal synthesized aluminum hydroxide, Boehmite by GAXRD and transmission electron microscopy (TEM).