Additively manufactured Inconel 718 plus superalloy with heterostructures and high mechanical properties

Wire-arc directed energy deposition (DED-arc) is a promising method to efficiently build large complex parts. However, columnar-grained structures commonly exist in DED-arc parts which exhibit anisotropic properties. In this study, the morphologies, microstructures, and mechanical properties of Inconel 718 plus superalloys fabricated by hybrid DED-arc with micro-rolling (HDMR) are investigated. Simulation and experimental results show that increasing the rolling force flattens the weld bead and significantly enhances the aspect ratio. Additionally, our simulations reveal that as the rolling force increases, there is a corresponding rise in equivalent plastic strain while longitudinal residual tensile stress decreases; intriguingly, residual compressive stress may even emerge. The HDMR process alters the morphology of the brittle Laves phase with a reduced content. Notably, a heterostructure characterized by alternating fragmented columnar (average size of 64.4 μm) and equiaxed fine grains (average size of 49.9 μm) is observed at a 30 kN rolling force, which can weaken the texture strength and enhanced dislocation density of the sample. In summary, in-situ rolling shows great potential in enhancing both tensile and yield strength while significantly minimizing the anisotropy of built samples. To validate these findings, an Inconel 718 plus superalloy combustion chamber is built utilizing the HDMR method.