Microstructure of Selective Laser Melted 316L under Non-Equilibrium Solidification Conditions

In this study, the microstructural properties of selective laser melted 316L stainless steel were investigated using optical, scanning and transmission electron microscopy as well as X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy. The results show a very fine microstructure with visible melt pool boundaries and austenite as the predominant phase. Extremely fine sub-grain structures can be found within the grains, consisting of colonies of round or elongated cellular structures depending on orientations. Due to the prevailing cooling and solidification conditions, micro-segregations occur, leading to enrichment of the sub-grain boundaries with alloying elements such as silicon, chromium, manganese and molybdenum. The presence of ferrite could be detected in this area using TEM analysis.