Effect of Laser Surface Treatment on the Corrosion Resistance of Zircaloy-4 at High Temperature

Abstract

A 700 V pulsed laser was used for the surface treatment of Zircaloy-4. Phases including the treatment layer, morphology and the distributions of alloying elements of the treatment layer were detected via X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The results showed that the laser surface treatment (LST) layer is also α-Zr phase layer, the morphology of the treatment layer was “cauliflower-like” and the Fe-Cr precipitates in the LST layer were dissolved. The corrosion tests of the LST and the no-laser surface treatment (NLST) specimens were conducted in steam at 1100 °C using TGA (NETZSCH STA 449 F). The results showed that LST can enhance the corrosion resistance of the Zircaloy-4 in high-temperature steam. More microcracks distributed in the oxide film formed on the NLST specimen than on the LST specimen. And the volume fraction of the tetragonal zirconia (t-ZrO2) phase in the oxide film on the surface of the LST specimen was higher than that of NLST specimen. The main reason for this phenomena could be attributed to the dissolving Fe-Cr precipitates and higher solid solution of Fe and Cr in the laser treatment layer.