Notched Fatigue Behaviour of Additively Manufactured Inconel 718
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Fatigue behavior for different notch geometries of additively manufactured Inconel 718 produced by Selective Laser Melting is investigated at room temperature. Additive manufacturing enables complex geometries in components by producing parts layer by layer from computer aided 3D models, however the produced surfaces are rough and can contains defects, which strongly influence the mechanical behaviour of respective components. In order to take advantage of the possibilities available concerning topology optimization and the allowed complexity of geometry when fabricating with additive manufacturing for load bearing applications, the notched fatigue behaviour of the materials must be evaluated. Inconel 718 is a Ni-based superalloy with high strength, creep and fatigue resistance at elevated temperatures, commonly used in aerospace industries and other industries with high demands of mechanical properties in extreme conditions. In this work I investigate the high cycle fatigue strength of different notch geometries produced by additively manufactured Inconel 718 specimens, a topic not yet reported in literature, but of great importance in terms of the complexity of the components currently being designed for additive manufacturing. The fatigue strength is evaluated for four different geometries, one smooth, one semi-circular and two different blunt v-shaped notches. Fractography of the fracture surfaces is done with scanning electron microscopy, showing that the cracks are initiating from surface defects such as lack of fusion in the notched region. Further the fatigue data is analysed by use of the energy based method strain energy density, unifying all the fatigue data in one single notch independent curve predicting the fatigue life.