Comparison of surface integrity of GH4169 superalloy after high-energy, low-energy, and femtosecond laser shock peening

In this study, different laser shock peening (LSP) techniques including high-energy laser shock peening (HE-LSP), low-energy laser shock peening (LE-LSP), and femtosecond laser shock peening (FS-LSP) were performed on GH4169 superalloy. The evolution of surface characteristics and microstructure was compared. Results show that the dominant deformation mechanism of GH4169 superalloy after various LSP treatments is dislocation slip, which leads to irregular atomic arrangement and high-density dislocations. The δ phase in the γ matrix restricts the movement of the dislocations and causes massive pile-ups at its boundaries. Thus, a special δ-phase/dislocation composite structure will promote the development of substructure in the deformed layer, although there is no obvious grain refinement. The deformed layer depth and damage mechanism are related to the pulse duration. The order of surface roughness, deformed depth, and arc height ranked according to LSP treatments is: HE-LSP > LE-LSP > FS-LSP. LE-LSP and FS-LSP could replace HE-LSP for thin-walled parts.