Inconel 718 and stainless steel 316L bimetallic structures built using wire arc additive manufacturing

This study addresses the challenges associated with the fabrication of dissimilar metallic structures by Wire Arc Additive Manufacturing (WAAM), where compositional gradients and interfacial phenomena influence microstructural evolution and the resulting mechanical and corrosion performance. The aim of this work is to fabricate and characterize bimetallic walls combining Inconel 718 and 316L stainless steel using two deposition strategies (superimposed and overlapping), and to compare their behavior with single-material WAAM walls of each alloy. The materials were manufactured by WAAM and analyzed in terms of microstructure, hardness distribution, tensile behavior, and corrosion resistance. The microstructure is predominantly dendritic, consisting of an austenitic matrix with compositional heterogeneities and features consistent with the possible presence of Laves phase and cubic TiN precipitates. Localized defects, including microcracks and solidification-related discontinuities, were observed in the interfacial region. Inconel 718 exhibits the highest strength but reduced ductility, whereas 316L stainless steel shows lower strength and significantly higher elongation. The bimetallic configurations present intermediate mechanical behavior, with tensile properties lying between those of the two base materials and a lower elongation compared to 316L. Hardness follows a similar trend, being higher in Inconel-rich regions, lower in stainless steel, and intermediate at the interface. Corrosion testing reveals comparable global corrosion rates between bimetallic and monolithic materials, although a reduced passive range is observed in the multimaterial structures, attributed to compositional gradients and micro-galvanic effects. In conclusion, WAAM-fabricated Inconel 718–316L bimetallic structures exhibit a balanced combination of mechanical and corrosion performance, although interfacial heterogeneities remain a key factor governing their overall behavior.