Comparative assessments of the microstructure-mechanical-corrosion behavior of TIG-welded-304, 309/310, and 316 ASS for marine application

This paper presents the experimental and computational results of the comparative study of microstructure, mechanical properties and corrosion behavior of tungsten inert gas (TIG)-welded 304, 309/310, and 316 steels. The study involves the coupled influence of microstructural changes, sensitization tendency, mechanical response, and corrosion behavior under identical welding and environmental conditions. The welding was performed using ∼ 19 V, 200 A, and 1.5 m/min rate, respectively, with 20 l/min argon as a shielding gas. The heat input of 0.57 kJ/mm, arc length of 2.4 mm, medium-cone-electrode tip geometry with 3.2 mm diameter, and torch angle of 70° from the plate were used. The welded joints were characterized and afterwards exposed to a salt spray environment for 100, 200, and 300 h under constant load. Using finite element modeling (FEM), the high-risk failure regions and stress localization trends in the welded geometries were modeled to show the evolving microstructural modification in the different alloys. The results showed that the chromium-rich carbide formation along grain boundaries increased in all welded steels, suggesting varying susceptibility to sensitization, with 304 exhibiting more pronounced localized compositional heterogeneity in selected regions. TIG-welded 309/310 ASS exhibited the highest ultimate tensile strength (∼452 MPa) and yield strength (∼348 MPa), while 316 demonstrated improved resistance to chloride-induced degradation due to its higher molybdenum content. The salt spray conditions revealed time-dependent mass change behavior influenced by oxide film formation and corrosion product accumulation. The FEA results showed that the localization of stress occurred within the weld and gauge-length region, which is qualitatively in agreement with the fracture region of the tensile experiments. The implications of the results indicate a tradeoff between mechanical strengths and corrosion resistance among the studied alloys and are discussed to comparatively show the performance of 304, 309/310, and 316 in stressful and chloride-induced marine environments.