Abstract
Residual stress is generally considered as the main criterion in laser shock peening for enhancement of fatigue life. However, changes in material hardness, microstructure and surface roughness can also affect component performance. These three aspects are investigated in this paper for welded marine steel samples subjected to laser peening. After laser peening an increase in hardness was seen across the weld and parent metal, with the local hardness dependent upon the initial hardness of the region before peening. The increase was relatively higher for the weld metal which had lower initial hardness. The local surface displacement profiles reflected the number of laser peening layers applied, and the peening also affected the distortion of the specimen after welding.
Highlights
Laser shock peening (LSP) is a promising surface improvement technique that can increase the fatigue life of metallic components
This paper addresses the changes in material hardness, surface displacement profile, and microstructure of DH275 marine steel post welding and laser peening
This study found that the distortion increased with an increase in number of peening layers, which correlates with the resulting compressive residual stresses
Summary
Laser shock peening (LSP) is a promising surface improvement technique that can increase the fatigue life of metallic components. In the laser peening process a laser beam is pulsed on to a metal surface that can either be protected by an ablative layer or kept bare, and that is covered by a water layer. Various studies have examined the variability of stress during laser peening [2,3]. Increasing the number of peening layers typically results in an increase of compressive stress in depth. It is generally understood that during laser peening a thin layer of surface metal is melted when the process is carried out without an ablative tape covering. This study found that the distortion increased with an increase in number of peening layers, which correlates with the resulting compressive residual stresses. Distortion caused by the welding was present before peening
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