Microstructure and mechanical properties of bimetallic austenitic stainless steel 317 L/inconel 686 fabricated by wire arc additive manufacturing

This study investigated the feasibility of fabricating a bimetallic structure composed of austenitic stainless steel (SS317L) and the nickel-based superalloy Inconel 686 using Gas Metal Arc Welding (GMAW)-based Wire Arc Additive Manufacturing (WAAM). The microstructural evolution, phase formation, elemental distribution, and mechanical properties of the fabricated structure were systematically evaluated. Optical and scanning electron microscopy revealed a well-bonded interface with strong metallurgical bonding between SS317L and Inconel 686. X-ray diffraction confirmed a dual-phase microstructure (γ-austenite + δ-ferrite) in SS317L, a fully austenitic FCC structure in Inconel 686, and an FCC-dominated transition zone resulting from gradual Ni enrichment across the interface. Energy-dispersive X-ray spectroscopy demonstrated smooth elemental diffusion across the interface, while Mo and W preferentially segregated into the interdendritic regions of Inconel 686. Microhardness measurements exhibited a gradual increase from the SS317L region to the Inconel 686 region owing to solid-solution strengthening and microstructural evolution during the WAAM process. The bimetallic structure exhibited an ultimate tensile strength of 664 MPa, a yield strength of 426 MPa, and an elongation of 26%. Fracture of the interface specimens occurred within the SS317L region rather than at the interface, confirming the integrity of the metallurgical bond. These findings demonstrate that GMAW-based WAAM is a promising technique for fabricating SS317L–Inconel 686 bimetallic structures with sound metallurgical bonding and tailored mechanical properties for advanced structural applications.