Studies on laser peening of spring steel for automotive applications

Present experimental laser shock peening study on SAE 9260 spring steel, performed with an in-house developed 2.5J/7ns pulsed Nd:YAG laser, aimed to evaluate laser shock peening process as a possible alternative to existing shot peening practice for enhancing fatigue life of leaf springs. In the investigated range of process parameters, laser shock peening yielded largely comparable magnitude of surface compressive stress and shallower compressed surface layer than those achieved with existing shot peening practice. In contrast to considerably rougher shot peened surface with numerous defects, laser shock peening produced largely unaltered surface finish without peening-induced defects. With respect to shot peening, laser shock peening brought about significant increase in fatigue life. Improved fatigue performance of laser shock peened specimens is attributed to their better surface finish without peening-induced surface defects, which were potential fatigue crack nucleation sites in shot peened specimens. ► Study evaluates laser peening as an alternative to present shot peening practice for leaf springs. ► In contrast to shot peening, laser peening of spring steel produced unaltered surface finish. ► Laser peening yielded comparable surface stress with smaller case depth than shot peening. ► Laser peening brought about significant increase in fatigue life over shot peened specimens. ► Improved fatigue life of laser peened specimens is due to absence of peening-induced defects.