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

Abstract

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.