Fatigue life assessment of wire arc additively manufactured ER100S-1 steel parts

The aim of this work was to examine uniaxial, torsion, and multi-axial fatigue characteristics of ER100S-1 low carbon steel specimens fabricated with wire arc additive manufacturing (WAAM) technique, a subcategory of directed energy deposition (DED). Two distinct specimen orientations were tested—vertical and horizontal, extracted perpendicular and parallel to the WAAM deposited layers, respectively. Fracture surfaces of the tested specimens were analysed under scanning electron microscope (SEM) to observe fracture mechanisms corresponding to different specimen orientations, different fatigue loading conditions, and to interpret the fatigue results obtained from the tests. Finally, the obtained stress–life results were compared with the fatigue data available in the literature for a series of wrought and WAAM-built structural steel specimens. Moreover, the S–N curves obtained in this study were evaluated against the fatigue design curve recommended for offshore marine welded structures in DNV standard. Test results have shown advantageous characteristics of WAAM-built ER100S-1 specimens compared with behaviours of other structural steels and conservative prediction of its fatigue life by the design curve available in the DNV standard.