Comparison of surface integrity, microstructure and corrosion resistance of Zr-4 alloy with various laser shock peening treatments

Zirconium-4 (Zr-4) alloy is extensively utilized in the key structural materials of pressurized water reactors (PWRs). This study investigates the application of three distinct laser shock peening (LSP) techniques for the surface modification of Zr-4 alloy. The comparative analysis focuses on the mechanical effects induced by High- Energy Laser Shock Peening (HE-LSP) and the thermo-mechanical effects produced by Low-Energy Laser Shock Peening (LE-LSP) and Femtosecond-Laser Shock Peening (FS-LSP) on the surface integrity and microstructure of Zr-4 alloy. Additionally, the study examines how these modified surface states influence the corrosion resistance of the Zr-4 alloy. The findings indicate that LSP enhances the corrosion resistance of Zr-4 alloy through grain structure refinement, improved grain orientation, and the formation of Compressive residual stress (CRS). The ablation layer can further augment the corrosion resistance; however, the primary factor in enhancing the corrosion resistance of Zr-4 alloy lies in improving the corrosion resistance of the deformation layer. The sample subjected to HE-LSP exhibited the optimal corrosion resistance, demonstrating a 78.5 % reduction in corrosion current density.