Microstructural evolution and mechanical property enhancement: Thin-walled structures of an Inconel 718 superalloy fabricated via hybrid laser-arc directed energy deposition

Arc-directed energy deposition (Arc-DED) of the Inconel 718 (IN718) superalloy offers distinct advantages, such as low cost and high deposition efficiency. However, these methods are plagued by problems such as poor forming accuracy, coarse microstructures, and suboptimal mechanical properties. This study introduces a laser beam as an auxiliary heat source for the arc, seeking to present a novel approach to fabricate high-performance thin-walled structures of the IN718 superalloy. By contrasting the effects of Arc-DED and hybrid laser-arc directed energy deposition (HLA-DED) on the fabrication of thin-walled IN718 superalloy components, we find that HLA-DED technology significantly improves the forming accuracy, refines the microstructure, and enhances the mechanical properties of thin-walled structures. Specifically, compared with Arc-DED, the thin walls produced by HLA-DED show an 18.39 % increase in the effective width coefficient and a 59.13 % reduction in the machining allowance. Additionally, the significantly large heat input in HLA-DED expands the remelting region, leading to a higher microhardness of the samples. Prolonged in situ heat treatment during HLA-DED promotes the dissolution of Laves phases (950 degrees C) and subsequent precipitation of gamma '' strengthening phases and MC carbides (650 degrees C). These improvements significantly enhance both the strength and plasticity of the IN718 superalloy components fabricated via HLA-DED. As a result, compared with the Arc-DED samples, the HLA-DED samples exhibit superior yield strength, ultimate tensile strength and elongation in both the horizontal and vertical directions.