Pulsed laser welding of AISI 316L stainless steel under space conditions

• Pulsed LBW of 316 L SS tested under Earth, lunar, and low G for space manufacturing. • Bead geometry remained consistent across gravity levels due to rapid solidification. • Earth gravity produced higher porosity; low G showed smaller spherical pores. • Microstructure and solidification mode unaffected by gravity-driven flow. • EBSD showed equivalent grain size and shape, confirming suppressed buoyancy effects. Parabolic flight experiments investigated pulsed laser beam welding (LBW) of AISI 316 L stainless steel under Earth, lunar, and low gravity. Welding was performed in high vacuum using a pulsed 1070 nm fiber laser at constant pulse frequency and travel speed. Thermal behavior was analyzed using transient finite element modeling (FEM) under vacuum boundary conditions, considering heat conduction and radiative losses. Porosity and microstructure were characterized by computed tomography, scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). Weld bead width and overall microstructural features remained similar across gravity levels, consistent with the short pulse time associated with calculated solidification rates up to 127.5 mm/s. Pores formed under reduced gravity exhibited more spherical morphology and lower total pore volume, decreasing from 0.16 mm 3 on Earth to 0.10 mm 3 in lunar gravity and 0.03 mm 3 in low gravity. All conditions exhibited similar solidification morphology, with fully austenitic solidification near the weld periphery and ferrite–massive austenite toward the weld center. Grain size remained close to 10 µm in both conditions, while aspect ratios were approximately 2.7 and 2.6 for ground and low gravity, respectively, indicating limited gravity influence under the pulsed LBW conditions investigated.