Fatigue Design with Additive Manufactured Metals: Issues to Consider and Perspective for Future Research

Additive manufacturing (AM) is a state of the art technology enabling fabrication of complex geometries, in addition providing other advantages as compared to the traditional subtractive manufacturing methods. However, a wide variety of significantly influence fatigue behavior and structural performance of components made of AM metals. In addition to fabrication process parameters, these include the effects of build direction, surface roughness, residual stresses, and treatment, and multiaxial stress states. At the microstructural level, defects such as pores and lack of fusion particles, as well other microstructural features affect the behavior. In this paper, first a brief review of the aforementioned factors affecting fatigue behavior will be presented. Then some experimental multiaxial fatigue data for selective laser melting (SLM), which is powder bed fusion (PBF) metal AM process, of a common Ti alloy (Ti-6Al-4V) with applications in many industries presented and discussed. The effects of surface finish, heat treatment, and stress state will be evaluated, as well as mechanisms in different life regimes and the role of defects. Finally, some additional factors that must be considered before acceptance of the AM technology in critical load bearing applications will be addressed. (c) 2018 The Authors. Published by Elsevier Ltd.