A Comparative Analysis of Microstructural Variations in Horizontally and Vertically Built Planes of Selective Laser Melting-Fabricated 316L Stainless Steel in Comparison with Conventional 316L Stainless Steel

Additive manufacturing techniques are rapidly replacing conventional manufacturing routes for the fabrication of complex geometrical features. Selective laser melting (SLM) is one such technique that has considerable protentional to replace conventional techniques for the fabrication of metallic components. However, the anisotropy associated with the SLM-fabricated components has significant implications, which does not permit the widespread applications of SLM process. The anisotropic behavior of SLM-fabricated components is mainly due to the unique and characteristic microstructure features along various built planes and axes. In order to relate these microstructural variations with the resultant behavior along various built planes, an attempt has been made in this paper to deeply investigate the microstructure, grain morphology and phase compositions along horizontally and vertically built planes. A comparison with conventionally fabricated 316L stainless steel was also made to establish relationships. It was observed that all the investigated built planes can only be characterized by face-centered cubic austenitic microstructure. The microstructure features show considerable changes along different built planes with epitaxial sub-grain structure as the dominant feature along vertical plane and cells, columnar as the prominent microstructural features along the horizontally built plane. Afterward, the influence of observed microstructural variations in the density, hardness and tensile behavior was also observed. The density was observed to be independent of the built plane, whereas high hardness values along a vertical plane in comparison with horizontally built plane were observed. However, the ultimate tensile strength and yield strength values were higher for horizontally built samples in comparison with vertically built samples.