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Use of Multi-Modal Synchrotron Analytical Techniques Combined with Electrochemical Analysis to Understand Anomalous Localized and General Corrosion Behavior of Additively Manufactured 316L Stainless Steel

Text: Additive manufacturing via laser powder bed fusion (LPBF)of alloys is found to produce hierarchical microstructures containing fusion boundaries at the macroscale, irregular grains and grain boundaries at the microscale, and subgrain dislocation structures at the nanoscale. These structures, as well as inclusions and print-induced elemental segregation, may impact corrosion performance. Electrochemical polarization of LPBF 316L in simulated sea water indicates much greater variability in corrosion performance as compared to that of wrought 316L. To better understand reasons for this behavior, multimodal synchrotron analytical techniques (high energy diffraction, XAS, XRF, and XPEEM/LEEM) are used to characterize the alloy surface microstructure and chemical heterogeneities as well as the structure of the ultrathin passive layer formed in chloride-containing media. These novel results provide explanations for the impact of compositional heterogeneities on passive behavior and localized corrosion and suggest potential methods to tailor AM alloys for enhanced corrosion performance.