Residual Stress Distribution, Phase Transformation, and Wettability Characteristics of Laser Peened Austenitic Stainless Steel

Laser peening without protective coating (LPwC) has been performed on austenitic stainless steel (SS304) with a power density of 9 GW cm −2 and peening passes of one, three and five. Effect of single and multiple laser peening on the residual stress distribution, work-hardening, surface roughness, phase transformation, and wettability has been studied using XRD, EBSD, surface profilometer and goniometer. A maximum compressive residual stress of - 581 MPa and work hardening depth that extended beyond 500 μm were observed with 5 peening passes. Further, an increase in austenite to martensite transformation ( γ → α ′) from 9.4 (unpeened) to 18.5% was observed for 5 peening passes. The average grain size reduced to 11.53% for five-time peened samples compared to single-time peened samples. Wettability studies revealed hydrophilic to hydrophobic transformation after laser peening.