- Ece Alat, The Pennsylvania State University, University Park
The aim of my research was to develop ceramic coatings for zirconium-based nuclear fuel cladding that are corrosion resistant and that can withstand normal operation and accident conditions. Single-layer TiN, single-layer Ti1-xAlxN, and multilayer TiN/Ti1-xAlxN coatings were deposited on flat and tubular zirconium-based substrates by using cathodic arc physical vapor deposition (CA-PVD). Autoclave corrosion tests were performed in static pure water at 360°C and 18.7 MPa for up to 128 days. Following the autoclave test, weight gain analysis was used to characterize corrosion performance of the coated materials. Before and after the corrosion test, the materials were characterized by scanning electron microscopy for morphology examination, energy dispersive spectroscopy for elemental analysis, and x-ray diffraction to determine the phases present. Coating adhesion and corrosion performance was systematically improved through the optimization of parameters involving the substrate surface preparation method, substrate surface roughness, titanium bond coating thickness, coating thickness, deposition parameters, and multilayer design architecture. We determined deposition parameter effects on coating morphology, composition, and adhesion; identified optimized cathodic arc physical vapor deposition parameters to enhance adhesion of the coatings on flat and tubular specimens; and determined the corrosion behavior of TiN and TiAlN in nuclear reactor environment. We concluded that monolithic TiN, monolithic TiAlN, and multilayer TiN/TiAlN coatings are applicable on the substrates tested by using the cathodic arc physical vapor deposition method and that optimized multilayer TiN/TiAlN coatings enhance corrosion resistance at normal operation and extreme environment conditions.