Laser welding of additively manufactured 316L stainless steel fabricated with different building orientations

Abstract This study investigates the effect of building orientation on mechanical behavior and microstructure evolution of laser-welded joints in additively manufactured 316L stainless steel. Sheets with a thickness of 2.5 mm were fabricated using laser powder bed fusion (PBF-LB) technique at 0°, 45°, and 90° orientations, then laser welded in directions parallel, inclined at 45°, and perpendicular to the build layers, denoted as WJ0D, WJ45D, and WJ90D, respectively. Mechanical performance was evaluated through tensile testing and micro-indentation hardness measurements, while fracture morphology was examined using scanning electron microscopy (SEM). Microstructural evolution was characterized using laser microscopy and extensive electron backscattered diffraction (EBSD) analysis. The results revealed that the base metals exhibited predominantly austenitic microstructures regardless of the building orientation; however, strength and ductility varied significantly with printing orientation change. The welded joints displayed orientation-dependent differences in fusion zone (FZ) and heat-affected zone characteristics as well as hardness values. FZ widths of approximately 0.55, 0.50, and 0.40 mm were measured for WJ90D, WJ45D, and WJ0D, respectively, with corresponding hardness values of 180 ± 16, 197 ± 13, and 222 ± 9 HV. Tensile testing indicated that WJ0D achieved the highest joint efficiency of 99.7%. EBSD analysis revealed a high Σ3 twin boundary fraction of 27.9% in WJ0D, which correlated with its superior mechanical performance. Fractographic analysis through SEM confirmed ductile fracture behavior across all joints, as characterized by the presence of dimple features.