A Study on Effect of Multiple Laser Shock Peening on Microstructure, Residual Stress, and Mechanical Strength of 2.5 Ni-Cr-Mo (EN25) Low-Alloy Steel

The effect of multiple laser shock peening (LSP) on the microstructure, residual stress, and mechanical strength of 2.5 Ni-Cr-Mo, low-alloy steel (EN25) is investigated. LSP treatment is carried out for laser power density (LPD) in the range of 2.8 to 4.95 GW cm(-2) with different laser impacts and by maintaining an overlap of 70% and 58% along scanning direction and perpendicular directions, respectively. LSP-treated samples are characterized by residual stress, microstructural evolution, and mechanical strength. Single, double, and triple LSP treatments at 3.53 GW cm(-2) enhanced compressive residual stress at the surface by similar to - 520, similar to - 640, and similar to - 680 MPa compared to the as-received sample (- 100 MPa). In addition, for double and triple LSP impacts, the compressive residual stress is found at higher depths (850 and 965 mu m) than single LSP (660 mu m). XRD peak broadening analysis confirmed grain refinement and micro-strain in the LSP-treated samples. Further, the dislocation density increases with the number of laser impacts. As a result of microstructural refinement and creation of high dislocation density, the hardness in triple LSP-treated samples is increased by nearly 26% as compared to the unpeened one. Twenty percent improvement in yield strength and 12.5% improvement in ultimate tensile strength are observed in triple LSP-treated samples as compared to unpeened sample.

Automated summary

The effects of multiple laser shock peening (LSP) on the microstructure, residual stress, and mechanical strength of EN25 steel were investigated. The results showed that LSP treatment could increase compressive residual stress and hardness on the surface, as well as improve yield strength and ultimate tensile strength.