Direct metal laser-sintered stainless steel: comparison of microstructure and hardness between different planes

Microstructural analysis and micro-hardness measurements were performed on different planes of 316L stainless steel fabricated by direct metal laser sintering (DMLS) technique. A fine cellular network was observed within the steel microstructure, where morphology of most cells changed from columnar on XZ-plane (vertical section) to equiaxed on XY-plane (horizontal section). Correspondingly, morphology of most grains was found to alter from columnar for the XZ-plane to equiaxed in the case of the XY-plane. Moreover, X-ray diffraction (XRD) analysis revealed a fully austenitic structure for both the planes. The average micro-hardness value for the XZ-plane and XY-plane was insignificantly (≈ 3%) different, which was attributed to the random grain orientation observed on both the planes. However, the average micro-hardness of the DMLS-fabricated 316L stainless steel in this contribution was approximately 25% higher than that of the as-cast one.