Study of the Change in Surface Wettability for Zircaloy-4 Utilizing Spatially Homogenized Nanosecond Laser Beam

This study introduces laser surface modification technology using a 532 nm Nd:YAG nanosecond laser. A laser beam homogenizer was used to spatially homogenize the laser beam into a square shape with an interference pattern of 30 μm. For laser surface modification processing, primary processing under 110 conditions was first performed, and then, 15 types of main processing conditions were determined based on the three-dimensional surface structure of laser surface modified zircaloy-4. Subsequently, the specimen was post-processed using three methods: left in the air (25 ℃), heated in the oven (200 ℃ for 2 h), and boiled in water (100 ℃ for 2 h). In the absence of post-processing or with heat post-processing, the laser surface modified zircaloy-4 showed super hydrophobicity with a contact angle of 150° or higher for specific laser surface processing parameters. Under specific laser surface processing conditions, the laser surface modified zircaloy-4 with boiling water post-processing exhibited properties close to super hydrophilic with a contact angle of less than 5°. It was confirmed that the surface wettability of zircaloy-4 can be controlled using a spatially shaped nanosecond laser beam.