Abstract
In this study, Inconel 718 (IN718) specimens, manufactured by laser directed energy deposition (LDED), are subjected to three different heat-treatments to have different microstructural characteristics. Fatigue crack growth (FCG) testing is performed on both as-deposited and heat-treated specimens. The coarse Laves phases with uneven γ′′/γ′ precipitates severely decrease FCG resistance of LDED IN718. The soft precipitate-free zone around short-acicular δ-phase partly reduces FCG resistance of LDED IN718. The FCG threshold (ΔKth) of a judicious heat-treatment specimen increases by ~ 2.6 times vs. as-deposited specimen and reaches 10.8 MPa∙m1/2, and its ΔKth and FCG curve are comparable to those of wrought IN718.
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