Abstract: Nickel-based superalloys fabricated by wire-arc directed energy deposition, also known as wire arc additive manufacturing (WAAM), usually exhibit inherent columnar grain structure, micro-segregation, and rough surface. A novel deposition strategy, integrating an oscillating arc and forced interlayer cooling, was developed in WAAM of Inconel (IN) 718 components. The influences of deposition modes on geometrical characteristics, defects, microstructure, and mechanical properties were systematically evaluated. The results showed that the oscillation mode, compared to the standard parallel mode, can effectively promote the molten pool's spread and wettability, as well as prevent overflow, finally resulting in high geometric accuracy. In addition, the voids-like defects were reduced by 77.78%, while most common crack defects were not observed. Meanwhile, the forced interlayer cooling process further increased the cooling rate, leading to the reduction of the element segregation as well as the proportion of long-chain-like Laves phases. After a short-process modified heat treatment, the anisotropic mechanical behaviors of the as-deposited samples were almost eliminated. Compared with the parallel mode samples, the yield strength and ultimate tensile strength of the oscillation path samples increased by 5.75% and 9.25%, respectively, while the elongation increased significantly by 51.20%. This signifies that their strength and ductility were simultaneously improved. The strengthening mechanisms were further analyzed based on the distribution of the strengthening phases, as well as the residual Laves phases and porosity.

Key words: Wire arc additive manufacturing, Deposition strategy, Microstructure characterization, Strengthening mechanism, Inconel 718