Effect of build orientation on the surface topography, microstructure and corrosion properties of additively manufactured SS316L

This study investigates the effect of build orientation on the microstructure and corrosion behavior of stainless steel 316L fabricated utilizing laser powder bed fusion (LPBF). Samples were produced at various inclination angles (40°, 50°, 60°, 70°, 80°, and 90°) using gas-atomized SS316L powder under an inert argon atmosphere. Microstructural analysis was performed using optical microscopy and scanning electron microscopy (SEM) to examine grain size, sub-grain cellular structures, and melt pool morphology. Additionally, surface topography was analyzed via 3D optical profilometry, and quantitative melt pool geometry was statistically assessed using image analysis. Residual stresses were measured via X-ray diffraction (XRD), while Vickers microhardness tests evaluated the mechanical properties, and transmission electron microscopy (TEM) was employed to assess dislocation density and distribution. Corrosion performance was assessed through electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) and Mott-Schottky (MS) analysis in borate buffer solution. The potentiodynamic polarization results revealed that the 60° build orientation exhibited the lowest passive current density and highest breakdown potential, indicating superior passive film stability. Mott-Schottky analysis further confirmed that the 60° orientation promoted the most stable passive layer, with the lowest charge carrier density and the most positive flat-band potential, suggesting improved resistance to localized corrosion. Electrochemical impedance spectroscopy corroborated these findings, as the highest polarization resistance (R p ) was observed in the 60° orientation, indicating enhanced passive layer integrity. Conversely, orientations such as 50° and 90° exhibited high residual stress and greater susceptibility to localized corrosion. This research underscores the critical role of build orientation in optimizing the properties of LPBF-manufactured SS316L components for corrosion-resistant applications. • Build orientation significantly affects corrosion behavior of LPBF-fabricated SS316L. • The 60° orientation exhibits the lowest residual stress and best passive film stability. • A strong correlation is observed between melt pool geometry and electrochemical response. • 3D profilometry reveals peak-dominated surface texture at 60°, aiding film uniformity. • Mott-Schottky and EIS results confirm lowest defect density at the 60° build angle.