Impact of Aggressive Environments and Processing Orientation on the Mechanical Performance of L-PBF 316L Stainless Steel

This study addresses the limited understanding of how build orientation and aggressive environments jointly affect the mechanical reliability of L-PBF 316L stainless steel. Specimens were fabricated in vertical, edge, and flat orientations and exposed for 360 h to 1 M H₂SO₄, 3.5 wt.% NaCl, and dry air oxidation at 800 °C. Tensile tests and microstructural analyses revealed strong anisotropy: edge and flat builds showed higher tensile and yield strength, while vertical builds exhibited greater ductility. Aqueous environments caused surface degradation and moderate strength loss, most severe in vertical samples. High-temperature oxidation induced σ-phase precipitation, increasing tensile strength (~20%) but reducing ductility and yield strength. These findings highlight the critical role of building orientation and service conditions in ensuring long-term performance of L-PBF 316L stainless steel.