Overlapped weld bead analysis on dissimilar duplex stainless steel-2507 and inconel-625 using WAAM-CMT process

• WAAM-CMT dissimilar joints DSS-2507 and IN-625 for high temperature applications. • DSS-2507 and IN-625 microhardness slightly drops with increase in heat inputs. • Microhardness in overlapping zone (236.57-293.94 VHN) rose slightly with less heat. • Microstructure changes and grain coarsening occur in overlapping zones. • XRD and EBSD confirm phase structures and material properties. Additive manufacturing (AM) of dissimilar metals presents renewed possibilities for high-performance engineering applications, such as aircraft turbines, offshore pipelines, and chemical reactors, where components encounter varied thermal, mechanical, and corrosion demands. This study studies the overlapping weld bead formation between Duplex Stainless Steel-2507 (DSS-2507) and Inconel-625 (IN-625) utilising Wire-Arc Additive Manufacturing with Cold Metal Transfer (WAAM-CMT). For both metals, the current was changed (140A, 160A, and 180A), while the travel speed remained constant at 120 mm/min. The second metal deposition maintained a 30% overlap. A multi-technique characterisation approach, comprising micro-hardness testing, FESEM imaging, XRD, and EBSD analysis, was applied to examine microstructural evolution, crystallographic orientation, and mechanical property variations throughout the weld zones. In the intermetallic portions of the overlap, microhardness values ranged from 236.57 to 293.94 VHN, demonstrably exceeding those of the IN-625 metal zones. Results reveal that DSS-2507 hardness reduced with greater heat input due to coarser duplex structures, but IN-625 maintained consistent micro-hardness via solid-solution strengthening. Microstructural studies demonstrated strong grain coarsening and phase shifts within the overlap zones, which are crucial for joint integrity. XRD confirmed the presence of dual-phase and FCC structures, while EBSD provided insights into textural and boundary features essential for understanding fatigue and corrosion performance. This research provides insights into dissimilar metal weld invention, enabling the precise design of gradient materials and functionally customised structures through controlled WAAM-CMT overlapping procedures for next-generation manufacturing in demanding environments.