LDED-based additive-subtractive hybrid manufacturing of Inconel 718 superalloy: evolution of microstructure and residual stress

The development of additive-subtractive hybrid manufacturing (ASHM) offers a near-perfect solution for the integrated preparation of complex structural components. In this study, we prepared additive manufacturing (AM), ASHM-fabricated Inconel 718 (IN718) superalloy based on laser-directed energy deposition (LDED), including two subtractive manufacturing (SM) situations, i.e. milling after cooling (room temperature SM) and immediately milling after AM (high-temperature SM). The evolution of microstructure, residual stress and milling forces for IN718 during a complete ASHM process (including AM and subsequent SM) were explored by experiments, finite element and molecular dynamics simulation. The SM process induces gradient plastic deformation on the sample surface, which led to the formation of nano-grains, low-angle grain boundaries and residual compressive stress. Owing to the higher internal temperatures present at SM, the thermal softening effect results in lower milling forces being subjected to high-temperature SM sample. Also, the dynamic recovery results in lesser nano-grains, low-angle grain boundaries and residual compressive stress in high-temperature SM sample. Thus, SM immediately after AM has a lower degree of plastic deformation on the sample surface compared to room temperature SM, and shows advantages in the preparation of difficult-to-machine materials.HighlightsInconel 718 (IN718) superalloy was prepared by LDED-based additive-subtractive hybrid manufacturing (ASHM).The evolution of microstructure, residual stress and nano-hardness for IN718 during ASHM were investigated.Subtractive manufacturing process of ASHM introduces nano-grains and residual compressive stress.Thermal softening effects and dynamic recovery affect the plastic deformation degree of ASHM-fabricated IN718.