Apart from producing new components, Wire + Arc Additive Manufacturing (WAAM) enables the remanufacturing of worn metallic parts, supporting a circular economy. However, the as-built surface often shows significant waviness resulting from the layered bead deposition, leading to stress concentrations and thus reduced fatigue life. Finishing operations are typically performed to mitigate those effects, though omitting them could save processing time, energy consumption, and overall costs. This work investigates the fatigue performance of S355J2 steel components remanufactured by WAAM using EMK8 wire, retaining as-built surface waviness. A novel four-point bending specimen with a WAAM-filled groove was designed to replicate a surface repair. Two electric arc welding methods — conventional short-circuit and Cold Metal Transfer — were compared to assess the effect of a different heat input. The former process resulted in higher heat input during material deposition. Compared to reference curves for S355J2 and bulk WAAMed EMK8 specimens, the fatigue strength of the remanufactured specimens was seen to be reduced. The as-built surface resulted in steeper slopes of the S-N curves compared to the polished reference materials. Crack initiation was determined by infrared thermography and was seen to occur between 6 and 50% of the total fatigue life, indicating that the majority of the total fatigue life consisted of crack propagation. The fatigue cracks were monitored by digital image correlation and were seen to propagate into the S355J2 substrate material, which can be considered as dominant for the crack growth rate.
Motte et al. (Thu,) studied this question.