Fatigue Behavior of L-PBF Metals: Cost-Effective Characterization via Specimen Miniaturization

High-performance metal parts are presently produced by the powder bed fusion (PBF) technology. When considered for structural applications, a key ingredient that would promote technology acceptance in industry is know-how on fatigue properties of PBF metals. The typical approach of published fatigue characterizations uses specimens of standard geometry with machined gage sections. However, surface machining of PBF parts should be minimal to be competitive with conventional fabrication technologies while the influence of rough as-built surfaces on fatigue performance should be experimentally quantified to overcome unacceptable trial-and-error approach to part design and qualification. To support this critical task, an original testing approach based on drastic specimen miniaturization to reduce cost and increase flexibility (i.e., the specimen is 22 mm long and 5 × 5 mm2 in minimum cross section) and plane cyclic bending to highlight the role of surface state. The method has been first published in 2017 and since then it has successfully applied to the fatigue characterization of L-PBF metals under a variety of surface conditions, surface orientations and surface finish. Factors such as as-built versus machined surfaces, surface orientation with respect to reference build direction, geometrical notches have been investigated for different L-PBF metals. The paper presents this cost-effective test method and reviews its recent applications to the fatigue characterization of Ti6Al4V, AlSi10Mg and In718 under different L-PBF processing and surface finishing conditions.