Effect of duplex and austenite stainless steel fillers on mechanical, microstructural, and corrosion characteristics of dissimilar welds using Cold Metal Transfer welding

• Comparative study of E309L and E2209 fillers in dissimilar CMT welds. • Duplex filler E2209 shows superior strength, hardness, and pitting resistance. • Austenitic filler E309L provides better ductility and intergranular corrosion resistance. • Comprehensive analysis supports filler selection for durable welded joints. This research analyzes the mechanical, metallography, and corrosion characteristics of dissimilar (SS316L and SS439 stainless steels) weld joints developed with Cold Metal Transfer (CMT) technique with E309L and E2209 filler wires. SEM analysis of the WZs (WZ) showed that E309L exhibited a homogeneous structure with larger and more frequent pits in corrosion testing. In comparison, E2209 welds demonstrated finer dendritic structures with fewer corrosion pits, indicating superior resistance to pitting corrosion. Mechanical testing highlighted that E2209 welds achieved an improved ultimate tensile strength (582 MPa) and 74 MPa impact strength compared to E309L welds (525 MPa UTS and 62 MPa impact strength). However, E309L welds exhibited slightly better elongation (35 %) due to their fully austenitic structure. Microhardness analysis revealed that E2209 welds had higher hardness in the WZ (approximately 350 HV), attributed to their duplex microstructure. In contrast, E309L welds showed uniform but lower hardness values (∼330 HV), and the potentiodynamic polarization tests were done in NaCl solution (3.5 wt. %) showed better corrosion resilience for E2209 welds, with has a reduced corrosion current density and a more favourable corrosion potential compared to E309L welds. SEM analysis of the corrosion morphology confirmed fewer and smaller pits in E2209 welds.