Laser Shock Peening in Hydrogen Environments: Coupled Stress Transport Trapping Mechanisms and Application Gaps

Abstract

Hydrogen embrittlement limits the deployment of high-strength steels and advanced alloys in hydrogen infrastructure. Laser shock peening (LSP) is increasingly considered as a mitigation route because it combines deep compressive residual stresses with near-surface microstructural modification. This review critically assesses LSP not as an isolated strengthening treatment, but as a surface layer design strategy governed by coupled stress, hydrogen transport and trapping mechanisms. Evidence from steels, nickel based alloys and additively manufactured materials shows that compressive residual stresses may suppress stress assisted hydrogen transport and delay crack initiation, while LSP-induced nanostructuring, dislocations, twins and interfaces can either redistribute hydrogen beneficially or promote localized plasticity and damage. Reported trends are frequently confounded by hydrogen charging mode, surface roughness, contamination, residual stress depth profiling and limited structure performance correlations. Two design critical gaps are identified: the lack of quantitative links between post-LSP stress/defect architectures and hydrogen assisted fatigue crack growth, and the near absence of impact toughness data after LSP under hydrogen exposure. The review proposes mechanism informed qualification routes combining residual stress mapping, hydrogen characterization, service representative mechanical testing and modelling.