Oxidation Behavior Of Cr-Coated Zirconium Alloy Cladding In High-Temperature Steam Above 1200 Degrees C

Dense, uniform, and well-adhered chromium (Cr) coatings were deposited on zirconium (Zr) alloy claddings by using physical vapor deposition (PVD). The Cr-coated samples were tested at 1200 C-o and 1300 C-o, respectively, for different exposure time in water steam environment. Microstructures and compositions of the coating/substrate system after oxidation were characterized by X-ray diffraction, scanning electronic microscopy, and energy dispersion spectrometer. The microstructural results clearly demonstrated that Cr2O3 layer has been produced on the coating surface, acting as an oxygen diffusion barrier and concomitantly reducing the oxidation rate. The experimental results on weight gains soundly supported the microstructural findings that the Cr coatings could protect the Zr substrate from high-temperature steam oxidation, even at a temperature up to 1300 C-o. Finally, the oxidation kinetics was theoretically analyzed and the underlying oxidation mechanism was also clarified.