Improvement of material performance of Inconel 718 formed by high deposition-rate laser metal deposition

As precipitation hardening nickel-based super-alloy, the mechanical properties of Inconel 718 (IN718) formed by high deposition-rate LMD (HDR-LMD) are far lower than the relevant specifications, making it unable to be used in practical industry applications. With the purpose of improving its material performance, the current study has been carried out. The microstructure characteristics of the as-deposited IN718 have been analysed, and the mechanical properties of it have been tested. Based on which, reasons that result in its poor mechanical properties have been identified. Furthermore, aiming to solve these problems the methods in order to improve material performance have been studies. It is found: the poor mechanical properties of the as-deposited IN718 could be significantly improved by HIPing (Hot Isostatic Pressing) and proper heat treatments. In addition, the mechanical properties of the heat-treated material are superior to AMS specifications for IN718 fabricated by conventional manufacturing processes. It concluded: HIP can dramatically reduce the porosity of the as-deposited material; the columnar grains can be transformed to equiaxed grains by homogenization, eliminating material anisotropy; Laves phase could be dissolved by solution treatment, transforming to needle-like d phase; strengthening phases will be precipitated by double aging, therefore strengthening/hardening the material.