Microstructure and Corrosion Characteristics of Selective Laser-Melted 316L Stainless Steel: The Impact of Process-Induced Porosities
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The microstructure and corrosion susceptibility of selective laser-melted (SLM) 316L stainless steel on planes aligned and perpendicular to the building direction in aqueous 3.5 wt.% NaCl solution were investigated and compared with their conventionally wrought counterpart. Cyclic potentiodynamic polarization results confirmed a superior pitting resistance and a reduced rate of metastable pitting for the SLM-fabricated samples regardless of the sample’s orientation compared to the wrought alloy. Although the process-induced porosities in the SLM samples did not affect the corrosion and pitting potentials of the alloy at the initial immersion time, they likely contributed to the reduced re-passivation potential of the surface. Furthermore, at longer immersion times, the electrochemical impedance spectroscopy and immersion testing results confirmed a more detrimental impact of the process-induced porosities on lowering the electrochemical stability of the SLM-316L surface perpendicular to the building direction, where larger size and higher density of crevice-like porosities were detected.
The authors are grateful for support of the Natural Sciences and Engineering Research Council of Canada (NSERC) [Grant #RGPIN-2017-04368] for sponsoring this work. M.M. would like to thank NSERC [Grant #RGPIN-2016-04221], New Brunswick Innovation Foundation (NBIF) [Grant #RIF 2018-005], and Atlantic Canada Opportunity Agency (ACOA)-Atlantic Innovation Fund (AIF) [Project #210414].
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