Performance enhancement of local dry underwater TIG welded 304L stainless steel joints using ERNiCrMo-3 filler

The underwater welding of 304L austenitic stainless steel presents challenges in nuclear applications. The resulting welds require consumables evaluation alongside procedural optimization to ensure corrosion resistance and structural integrity. This work employed ERNiCrMo-3 nickel-based filler wire for local dry underwater TIG welding. Process parameters and joint performance were comprehensively evaluated. Welding current and travel speed were optimized to establish a stable process window suitable for multi-layer and multi-pass welding. Defect-free welds were ultimately achieved under the matched parameters. The γ-Ni austenite constituted the matrix phase of the weld metal. Microstructural characterization revealed epitaxial columnar dendrites near fusion boundary and equiaxed grains at weld center. Distinct resolidified structures were also observed within the remelted regions. Interdendritic segregation of Nb and Mo induced the precipitation of Nb-Mo enriched intermetallic compounds.The welded joints achieved an average ultimate tensile strength of 703.3 MPa. In an aqueous solution containing 16000 ppm H 3 BO 3 and 200 ppm NaCl at 50 °C, the ERNiCrMo-3 weld exhibited a lower corrosion rate (4.03 μm/a) than both the 304L base metal and the ER308L weld counterparts (7.57 μm/a). No stress corrosion cracking was found after 90-day U-bend immersion experiment. The results confirmed that ERNiCrMo-3 filler upgraded the service performance of underwater TIG welded joints. Enhanced performance was benefited from homogeneous microstructure and synergistic effects of multi-alloying elements including Ni, Cr, Mo and Nb. This study offered practical technical references for filler selection and process formulation in underwater repair of nuclear facility components.