A new insight into pitting initiation in selective laser melted 316L stainless steel

Abstract

In this work, the effect of process parameters on pitting corrosion behavior and a detailed study on the pits formed in selective laser melted (SLM) 316L stainless steels in 3.5 wt% NaCl solution were studied. Cyclic polarization (CP) was carried out on the surfaces along the build direction and the pits were characterized using a scanning electron microscope (SEM). Increasing the laser power improved the corrosion resistance while increasing the scan speed was detrimental to it. It was identified that small pits initiated at melt pool boundaries and through dissolution of cell interiors which then possibly coalesced to form bigger pits with a lacy cover formation. The work hence identifies new possible pit initiation sites in SLM SS316L while performing an in-depth analysis of the morphology to understand possible propagation mechanisms.