Ion beam mixed oxidation protective coating on Zry-4 cladding

Abstract

In this study, SiC was coated on the surface of Zry-4 cladding to improve the oxidation protectiveness. In the coating of SiC onto Zry-4, the prime concern was adhesion at an elevated temperature. Here, a 70keVN ion beam was irradiated onto a SiC coating layer of ∼100nm in thickness; this was deposited via the e-beam evaporation method. Additional coating to a target thickness was then carried out. The films deposited without ion-beam mixing (IBM) often peeled-off at an elevated temperature, while the IBM SiC film always adhered to Zry-4, even after heating to ∼1000°C; at such a temperature, however, cracks formed in the film. X-ray photoelectron spectroscopy (XPS) analysis showed that the deposited SiC film contained about 20at.% of O, while after annealing in air, 76at.% of O was found on the surface layer. This implied that both the surface of SiC film and Zry-4 in the crack lines were oxidized. Comparing the Zr3d peak positions across the interface, a shift of binding energy by ∼1eV was detected, representing that, in view of favorable thermodynamics, SiC/Zry-4 seems to be an acceptable system to apply IBM. To heal the crack, the process of IBM for a 1μm thick coating and annealing was repeated. High-resolution field emission secondary electron microscopy (FE-SEM) showed that the crack lines, the main places at which oxidation occurred, were gradually covered as the process was repeated, ensuring enhanced oxidation protectiveness.