Effect of laser energy on surface deformation mechanism of Nickel-based single-crystal superalloy subject to Laser shock peening

This study investigates the effects of Laser Shock Peening (LSP) on the mechanisms of surface plastic deformation in nickel-based single-crystal (NBSC) superalloys. After LSP at 5–9 J, no grain boundaries are introduced, and the single-crystal (SC) characteristics of the material are still retained. Severe plastic deformation occurs accompanied by the formation of a millimeter-scale work-hardened layer (the hardness could increase by 53.8%). In addition, the periodic structures formed on the surface lead to a maximum increase in surface roughness by approximately 8.1-fold. The deformed surface layer comprises a severe plastic deformation layer (SPDL) and a mild plastic deformation layer (MPDL). Within the SPDL, LSP activates the {111}<110> octahedral slip systems, generating high-density <110>-oriented cross-slip bands and characteristic dislocation configurations such as stacking faults (SFs), dislocation walls (DWs), dislocation tangles (DTs), and dislocation networks, thereby increasing the geometrically necessary dislocation (GND) density. At 10 J, localized remelting zones caused by thermal effects are also involved in the plastic deformation process, resulting in a reduction in the SPDL depth and GND density. Nevertheless, the γ matrix phase exhibits a significantly higher dislocation density than the γ' precipitate phase for all LSP-treated samples. This discovery provides critical mechanistic support and parameter guidance for the engineering applications of LSP in the precise surface modification of SC alloys.