Effects of Hatch Distance on the Microstructure and Mechanical Anisotropy of 316 L Stainless Steel Fabricated by Laser Powder Bed Fusion

Laser powder bed fusion (LPBF) has unique metal processing characteristics that allow rapid heating and melting of metal powder to form the 3D objects in a layer-by-layer manner. The parts fabricated through LPBF inherited anisotropy behaviors in microstructure and mechanical performance. To effectively ensure the as-built part functionality in terms of microstructure and mechanical performance, scanning direction (SD), building direction (BD), and transverse direction (TD) were selected to be analyzed to build a quantitative process-quality model to control the tensile strength in this study. The influence of hatch distance on microstructure evolution is also investigated. X-ray diffraction (XRD) analysis indicated that (200) peak intensity of γ austenite (fcc) drop-down with hatch distance increased from 0.06 mm to 0.10 mm. Broadening of remelting zone of two adjacent tracks improved the epitaxial growth of column grain. The different ratios of tensile strength and elongation between scanning direction and building direction are 9.23, 19.26% with hatch distance of 0.06 mm, dropped to 3.27, 10.31% with hatch distance of 0.10 mm, respectively. When the hatch distance is over 0.1 mm, the tensile strength and elongation of TD samples drop sharply due to the lack of overlap between molten pools. The different ratio of mechanical anisotropy decreases with hatch distance increases, which also demonstrates that hatch distance can alter the anisotropic of LPBF-ed parts.