Double-Wire Additive Manufacturing Process of Functionally Graded Material by Robotic Arc Welding

In order to enhance the durability, high temperature corrosion resistance, and strength of SS316L in industrial applications, it is recommended to utilize Inconel 625 as a more efficient and costly covering material. Consequently, a double-wire and double-pulse metal inert gas welding process was employed to fabricate two thin-walled SS316L/Inconel 625 functionally graded materials (FGMs) with gradients of 25% and 5%. Subsequent analysis focused on the morphology, microstructure, and properties of the fabricated materials. The findings indicated that this process is a recommended method for manufacturing gradient materials. A consistent transition gradient of 5% resulted in a more stable deposition process, higher forming efficiency, and improved material properties. Evident fractures were observed along the dendrite growth in 75% SS316L area, specifically at the boundary of cellular dendrites analyzed by energy dispersive spectrometer and electron backscattered diffraction. Furthermore, hardness increased and tensile strength decreased along the build direction, specifically the lowest tensile strength was observed in the 75% SS316L/25% Inconel 625 area. Consequently, when selecting gradients for stainless steel and nickel alloy materials, it is advisable to avoid proximity to the 75% SS316L region when dealing with two dissimilar materials. The manufactured FGMs in this study were superior to the wrought value, then the mechanical properties were higher than SS316L and lower than Inconel 625 manufacturing of single material, and the anisotropy was not obvious, in addition, the cost of FGM is lower than that of single /Inconel 625 material. It can improve the problem that the gradient transition zone is easy to fail, reduce the cost, and extend the service life of the parts while meeting performance requirements. Therefore, this achievement can have a significant impact on enhancing the service life and preventing premature failure of dissimilar structure components.