Influence of scanning strategy and building direction on microstructure and corrosion behaviour of selective laser melted 316L stainless steel

In-depth understanding of corrosion behaviour is a key aspect regarding the application of additively manufactured parts. In this study, 316L stainless steel was manufactured under different scanning strategies using selective laser melting (SLM). Microstructure characterization and electrochemical tests in NaCl aqueous solution (3.5 wt%), including open circuit potential (OCP), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS), were conducted to study the influence of scanning strategies on the corrosion behaviour. The microstructure and corrosion on different planes were characterized to reveal the influence of building direction. EBSD analysis shows that the scanning strategy affects the continuity of grain growth through adjacent layers and the growth of grains inside the melt track. Electrochemical tests indicate a clear difference in corrosion resistance perpendicular and parallel to building direction and with different scanning strategies. Pitting corrosion is the main form of corrosion in SLM 316L stainless steel and preferentially initiates on molten pool boundaries.