Effect of heat treatment on the microstructure and pitting corrosion behavior of 316L stainless steel fabricated by different additive manufacturing methods (L-PBF versus L-DED): Comparative investigation exploring the role of microstructural features on passivity

This work explores the relation between microstructural features and pitting corrosion resistance of additively manufactured 316 L stainless steel. Specimens fabricated using two different laser-based manufacturing processes (L-PBF and L-DED) were studied in as-built and heat-treated conditions following a comparative approach. Potentiodynamic polarization tests and corrosion morphology analysis served to evaluate their corrosion resistance and passive behavior. This work shows that, contrary to previous reports, the absence of MnS inclusions or presence of the microsegregation structure are not the main factors enhancing passivity of these materials. Instead, dislocation density was the only microstructural feature matching the trend in their passivity behavior. • Passivity follows relation (L-PBF>L-DED>Wrought) for heat treatment bellow 1000 °C. • Heat treatment above 1210 °C deteriorates corrosion resistance by enhancing IGC. • MnS inclusions and micro-segregation structure are not deciding factors in corrosion. • Dislocation density was the only microstructural feature matching trend in passivity. [ABSTRACT FROM AUTHOR]