An efficient test method for the quantification of technology- dependent factors affecting the fatigue behavior of metallic additive manufacturing components

Powder bed fusion (PBF) is the most widely used additive manufacturing (AM) technology for producing high-performance metal parts. The fatigue characterization of PBF metals is a fundamental step toward technology acceptance for structural applications. Most published fatigue characterizations have adopted standard specimens with machined gage sections, although, to be competitive with conventional technologies, machining of PBF parts should be minimized. Therefore, the impact of the as-built surface quality on the fatigue performance of PBF parts is a major concern for part design and qualification. We describe a novel testing approach that adopts miniature specimens and plane cyclic bending for the fatigue characterization of as-built PBF metals and assess this approach for the case of a Ti6Al4V alloy against data obtained with standard specimen geometries and test methods. The role of factors such as stress versus build directionality, geometrical notches, and PBF technology on the high-cycle fatigue of Ti6Al4V is then quantified. The proposed method is cost-effective and has flexible applicability. Therefore, it is useful for basic fatigue research of PBF metals and for supporting the qualification of fatigue-critical PBF parts.