Effect of welding polarity on iron dilution, clad chemistry, and interfacial microstructure in multilayer SMAW Inconel 625 overlays on SA-3 87 grade 11 steel

Abstract

High-strength steels used in the oil and gas industry are susceptible to corrosion in harsh environments. Although Inconel 625 offers excellent corrosion resistance, its high cost limits large-scale application. Weld cladding with Inconel 625 provides a cost-effective alternative; however, excessive dilution with the steel substrate increases iron content and degrades clad chemistry. This study investigates the effect of welding polarity on iron dilution and clad chemistry in multilayer SMAW Inconel 625 overlays deposited on SA-387 grade 11 steel. Three-layer claddings were produced using direct current electrode negative (DCEN) and direct current electrode positive (DCEP) polarities. Clad chemistry was characterized by positive material identification (PMI) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS). Iron dilution was calculated from measured iron contents. Under the investigated conditions, the DCEN clad exhibited substantially lower iron content (3.97 ± 0.12 wt%) compared with the DCEP clad (10.6 wt%). DCEN also permitted a lower welding current (100–120 A versus 140–150 A for DCEP), resulting in reduced heat input. These findings demonstrate that DCEN polarity can effectively minimize iron dilution and produce clad chemistry closer to that of the Inconel 625 filler metal. Corrosion performance was not directly evaluated in this study and remains a subject for future investigation.