Warm laser shock peening without coating induced phase transformations and pinning effect on fatigue life of low-alloy steel

• The decarburized surface significantly acts as a protective layer in the laser ablation
• The retained austenite phases transform into martensites during warm laser peening
• The grain refinement and pinning force mechanisms are recognized in this course of work
• The depth wise improved mechanical properties are adequately enhancing the fatigue life
• The optimized thermal engineering process extending the fatigue life of low-alloy steel

The current study proposes warm laser peening without coating process utilizing decarburized surface as the protective ablation layer and is directly intended towards the experimental evolution of existing laser shock peening technology. The interlath-retained austenites are transformed into martensites during warm laser peening. Also, the depth-wise compressive residual stress and its thermal relaxation behavior are comparatively prevailing. The scanning and transmission electron microscopic analysis identify the severe plastic deformation features of microstructures. So, the grain refinement and pinning force mechanisms on the mechanical properties are recognized. Further, the micro and nano-hardness studies provide a significant improvement in the surface and sub-surface mechanical properties. Moreover, the optimized fatigue life of low-alloy steel is achieved through the thermal engineering process. The present work increased the fatigue life of the specimen by 26 times and it is effectively repairing the partially pre-fatigued specimen.

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