Wire+Arc Additively Manufactured Inconel 718: Effect of post-deposition heat treatments on microstructure and tensile properties

Wire + Arc Additive Manufacturing (WAAM) has emerged as a promising technique for producing large free-form components from advanced materials like nickel-base superalloys, particularly Inconel 718, which is favored due to its superior weldability. This study aims to investigate the effects of post-deposition heat treatments on the microstructure and tensile properties of WAAM Inconel 718. A series of experiments were conducted to analyze the microstructural changes and the corresponding mechanical properties after different heat treatment processes. The findings reveal that the as-deposited WAAM Inconel 718 exhibits Laves phase in its microstructure, which can adversely affect its performance. Application of a modified heat treatment effectively dissolved the Laves phase without leading to the precipitation of the δ phase. Furthermore, alterations in the grain structure induced by the heat treatments contributed to a reduction in anisotropy, resulting in enhanced elevated temperature tensile properties that meet the minimum specifications for cast materials, although they still fall short of those for wrought materials. This research underscores the significance of optimizing post-deposition treatments to improve the mechanical performance of WAAM Inconel 718 components.