This paper studies the effect of welding heat input on microstructure and low-temperature toughness of laser-arc hybrid welded (LAHW) SAF2507 super-duplex stainless-steel (SDSS) joints. Heat input was adjusted from 0.204 to 0.407 kJ/mm by changing the welding speed. Results indicate that low heat input brings high ferrite content and low impact toughness. The medium heat input generates a balanced two-phase microstructure and gains the highest impact energy of 36.0 J at −46 °C. Excessively high heat input results in obvious grain coarsening and degraded impact performance. This study offers an experimental basis and parameter reference for practical welding production.

Corrosion-resistant coatings with a double-layer structure are deposited on the surface of S30408 stainless steel at welding currents of 170 A, 200 A, and 230 A using metal active gas (MAG) arc welding technology. The influence of welding current on the microstructure, microhardness, wear resistance, and electrochemical corrosion behavior of the coating is systematically studied. The results show that the coating produced at 200 A exhibited the finest martensitic structure, the highest microhardness (~450 HV), and the lowest mass loss (139.9 mg), indicating its superior wear resistance. In contrast, the coating fabricated at 230 A displayed the most positive corrosion potential (−0.302 V vs. saturated calomel electrode (SCE)) in 3.5 wt.% NaCl solution, which is attributed to enhanced elemental homogenization arising from the higher heat input. This paper clarifies the critical role of welding current in balancing wear and corrosion performance and provides a practical guideline for the cost-effective surface enhancement of S30408 steel components.