Tensile Properties of Inconel 718 Produced by LMD-Wire

The anisotropy in tensile properties of Wire Laser Metal Deposited Inconel 718 (LMD-w) has been investigated from room temperature up to 750 °C at a strain rate of 5.0 10-4 s-1. These properties have been investigated along, at 45° and perpendicular to the building direction. Moreover, different heat treatments have been used: as-built, solution heat treated to dissolve Laves phases, solution treated + aged to trigger γ′/γ″ precipitation and direct-aged. According to this extensive characterization of tensile properties, complemented by SEM and EBSD characterizations, it is shown that, whatever the temperature, Yield stress and tensile resistance have a very weak anisotropy and that tensile properties are mostly dependent to the prior heat treatment state. The anisotropy is mostly observed on elastic properties, due to a pronounced crystallographic texture inherited from the directional thermal gradient during the building process. Moreover, Laves phases do not seem to have a strong impact on tensile properties for this coarse grain material. Tensile strength in such an LMD-processed Inconel 718 is mostly controlled by the γ′/γ″ precipitation and stored “processing” dislocations. A loss of tensile ductility has been evidenced at 750 °C, due to grain boundary oxidation.