Tailoring Surface and Subsurface Properties of Selective Laser Melted SS316L Subjected to Laser Shock Peening
摘要
This study examines the microstructural changes and residual stress evolution in selective laser melted (SLM) austenitic stainless steel 316L cylindrical disks subjected to laser shock peening without coating (LPwC) at distinct laser power densities (6, 9, and 12 GW cm−2). XRD analysis provided evidence of strain accumulation and an increase in defect density, as evidenced by peak shifts and peak broadening. EBSD data confirms that post-LPwC, the average grain size decreased from 74 to 62 µm at a power density of 12 GW cm−2. Additionally, KAM and GND density mapping show increased localized plastic strain at 6 GW cm−2 and 9 GW cm−2, and reduced dislocation activity at 12 GW cm−2 due to dynamic recrystallisation mechanisms. Furthermore, microhardness was elevated by up to 20 % at 12 GW cm−2. However, the cross-sectional depth profile suggests 6 GW cm−2 has much more stable hardness across the depth. The LPwC process effectively increased the residual stress from a low CRS baseline in the as-built condition to a maximum CRS of 572 MPa at 6 GW cm−2. While 12 GW cm−2 yielded the highest grain refinement due to high peak pressure, the depth of the CRS was limited compared to 6 GW cm−2, a trade-off attributed to the pulse-shortening effect of dielectric breakdown. This comprehensive study reveals the efficacy of LPwC in achieving superior surface properties, offering a reliable post-processing approach for AM metallic parts designed for extreme environments.