Notch fatigue behavior of Inconel 718 produced by selective laser melting

Inconel 718 is widely used in hot structures of jet engines because of its excellent mechanical properties at high temperatures. Recently, customized parts of complex geometry are increasingly fabricated by Selective Laser Melting (SLM) of Inconel 718 powder. This contribution investigates the still largely unexplored topic of the combined influence of notches and as-built surfaces on the fatigue strength of SLM Inconel 718 parts. An innovative fatigue test method using miniature notched specimens tested in cyclic plane bending is adopted. Four sets of specimens, each with a different orientation of the notch surface with respect to the build axis, are fabricated with a commercial SLM system, heat treated and fatigue tested. The fatigue results show the directional nature of the as-built notch effect. The link between surface quality of the notched specimens and their layer-wise fabrication is determined by a metallographic investigation.