The study focuses on the influence of diode laser melting on the microstructure, mechanical properties, and corrosion resistance of low-nickel austenitic stainless steel, which are important because this material is widely used as a cost-effective alternative to conventional stainless steels and must perform reliably in advanced manufacturing processes. In this work, the microstructural changes, hardness variation, residual stresses, and corrosion characteristics of laser-treated steel were examined in detail. The results show a clearly defined heat-affected zone with localised dendritic structures, while no major phase transformation was observed. Using a high-power diode laser, this study investigates the laser melting and welding behaviour of Low Nickel Austenitic Stainless Steel to create a stable, fully penetrated autogenous weld devoid of filler material. At a constant scanning speed of 12 mm/s, laser welding experiments were carried out at power levels between 2400 and 3600 W. Scanning electron microscopy , energy dispersive spectroscopy and electron backscatter diffraction were used to characterise the base metal, fusion interface, and weld centre’s microstructure and composition. The findings show that localised manganese depletion and segregation were seen in the fusion zone, although the key alloying elements (Cr, Mn, Ni, and Cu) were mainly retained after welding. Fe and Cr had uniform distributions according to elemental mapping, whereas Mn displayed localised segregation that affected microstructural homogeneity. Measurements of hardness showed differences between samples, with improved uniformity (240–300 VHN) linked to finer grain structures and peak values exceeding 320 VHN. Nitrogen-shielded welds showed nobler corrosion potentials and lower corrosion current densities than argon-shielded welds, according to electrochemical corrosion testing. Residual stress analysis revealed that argon-shielded samples had higher compressive stresses than nitrogen-shielded samples, demonstrating the significant influence of shielding gas on weld integrity and performance.