Influences of Scanning Speed on Microstructure, Anisotropic Properties and Corrosion of L-PBF SS316L within a High-Density Region

Abstract In this study, stainless-steel 316L samples were fabricated by the laser powder-bed fusion (L-PBF) process under three distinct printing parameter sets, namely, varying scan speeds while maintaining other parameters fixed. The samples were categorized according to their volumetric energy densities (VEDs) as high, medium, and low conditions, which were all included in the range of achieving high relative density. Detailed characterizations of melt pool geometries, grain morphologies, and crystallographic textures were conducted along with Vickers hardness measurements and anodic polarization tests on specific planes of the printed specimens. Results indicated that the crystallographic texture was significantly influenced by the VED, with a preferential orientation of {100} <001> observed in the high VED condition, whereas both medium and low VED conditions displayed a mixed texture of {100} <001> and {110} <001>. The high VED promoted the formation of deeper and wider melt pools embedded with larger, irregularly shaped grains, whereas the medium and low VEDs resulted in narrower melt pools and smaller grain morphologies. Notably, the medium VED generated uniformly stacked melt pools with a periodic stripe pattern, featuring <001> grains aligned at the centerline and <011> grains at the edges, achieving the most accurate depth-to-width ratio according to given input parameters. Such variations in texture and grain morphology directly affected the mechanical responses, whereas differences in grain size governed the corrosion properties in each characteristic direction, depending on the printing strategy. Hereby, highly anisotropic mechanical and corrosion behaviors in the printed material were induced. The critical role of VED or scanning speed in controlling the microstructural characteristics and hardness of L-PBF 316L samples was highlighted.