Development of ferritic–austenitic functionally graded structure via twin wire arc additive manufacturing route

Directed energy deposition-based twin wire-arc additive manufacturing (WAAM) is becoming an increasingly popular technology for fabricating a wide variety of structural components. The spectrum of WAAM applications has rapidly extended, especially over the last decade, including but not limited to offshore and maritime applications, low-volume manufacturing and prototyping, moulds, tooling repair and renovation, and large-sized parts. The present article reports the functionally graded deposition (FGD) with varying compositions of dissimilar steel using twin WAAM. The obtained FGD structure interface displays two distinct zones made up of deposits of austenitic stainless steel (ASS) and low carbon steel (LCS), and it is devoid of any welding flaws. Additionally, several investigations of FGD structure were carried out to obtain a detailed analysis of its mechanical and microstructural characteristics. LCS had a ferrite morphology that was acicular and polygonal, while the microstructure of ASS showed vermicular δ-ferrite and lathy morphology. Hardness profile near the interface of FGD shows a considerable increase in hardness as chromium shifts from ASS to LCS. FGD ultimate tensile strength (UTS) is higher than LCS (499.46 ± 11 MPa) but lower than ASS (583.75 ± 10), but FGD yield strength (YS) is higher than both ASS and LCS because of elements diffusion. Overall, the interface of FGD structure showed significant mechanical bonding and durability.