Influence of Substrate Inclination Angle on Deposition Morphology and Interfacial Microstructure During TIG-Based Wire Arc Additive Manufacturing of Steel/Tin Bimetallic Structures

Steel/tin bimetallic components fabricated using traditional casting processes have inherent drawbacks, including complicated preparation procedures and a relatively low interfacial bonding strength. To efficiently create metallurgical composite steel/tin bimetallic structures under complex service conditions, we utilized TIG-based additive manufacturing with front wire feeding to prepare the components. The effects of the substrate inclination angle on the macroscopic morphology of the deposited layer, interfacial phase composition, the growth behavior of intermetallic compounds (IMCs) at the bimetallic interfaces, and interfacial mechanical properties were investigated. Our results show that macro-structural defects like cracks, voids and pores were not observed at the steel/tin interfaces. The grains of the interface IMCs were mainly composed of Fe3Sn, FeSn2 and FeSb2 phases; Fe-rich microspheres were dispersed inside the deposited tin layer. Under horizontal substrate conditions, deposited layer morphology and IMC layer thickness presented symmetric distributions. When the inclination angle of the substrate reached 30°, the deposited layers exhibited an asymmetric teardrop morphology, resulting in an increased layer height and width and penetration depth. Meanwhile, tin alloy grains were significantly refined; more high-angle grain boundaries (HAGBs) were formed at the spreading fronts of molten droplets. Tin alloy hardness was improved via synergistic dispersion and grain boundary strengthening. This work reveals the inclination–morphology–microstructure–property correlation, fills the research gap in inclined substrate arc additive manufacturing of steel/tin bimetals, and provides a theoretical foundation for engineering applications.