Comparisons on localized surface modifications of stainless steels induced by laser shock peening and robotic hammer peening

Abstract

Localized surface peening processes have been carried out on single spots by employing laser-shock peening (LSP) and robotic hammer peening (RHP) on stainless steels SS304L and SS316L. The LSP process has induced apparent γ-to-ɛ martensite transformations (MTs) in the surface layer of SS304L rather than in that of SS316L. In comparison, the MTs induced by the RHP process in the surface layer of SS304L with the crater depth similar to that produced by LSP is dominated by γ-to-α’ rather than γ-to-ɛ. Further studies of groove-like tracks produced by RHP scanning on SS316L with varied paths provided clues for material migrations on the surface from the center to the edges of the tracks. Detailed surface modifications by LSP and RHP are finally discussed based on the observations under scanning-electron microscope.