Corrosion Behavior of Laser Powder Bed Fusion Fabricated Stainless Steel 316L

Abstract

Metal additive manufacturing techniques have been recognized for their capability of controlling the crystallographic orientations of stainless steels. However, the inherent anisotropic corrosion behavior has not been extensively studied. In this study, the corrosion properties of 316L stainless steels prepared by Laser Powder Bed Fusion (LPBF) additive manufacturing were investigated. The effects of different crystallographic textures, namely {100}, {110} and {111} on both general and pitting corrosion were characterized by several electrochemical measurements, including Electrochemical Impedance Spectroscopy (EIS), potentiodynamic polarization and Mott-Schottky analysis. The results were also compared to the polycrystalline and wrought 316L counterparts. It was found that the LPBF-{111} sample offered the highest general corrosion resistance, followed by the LPBF-{100}, LPBF-polycrystalline and LPBF-{110} samples (Figure 1). The origin of this trend was related to the atomic surface density. The LPBF-{111} surface exhibited a stronger atomic bonding than that of LPBF-{100} and LPBF-{110} samples, resulting in a higher corrosion activation energy and thus a higher general corrosion resistance. All the LPBF samples also offered a significantly higher pitting corrosion resistance (Figure 2), which was attributed to the lower concentration of oxygen vacancies (donor levels) in the passive film that serve as pits nucleation sites, as observed by the Mott-Schottky analysis (Figure 3). Figure 1