Assessment of cyclic deformation behaviour of wire arc additively manufactured carbon steel

Wire Arc Additive Manufacturing (WAAM) has gained popularity due to its speed and cost-effectiveness. However, the current knowledge on the cyclic deformation behaviour of WAAM materials is limited. To address this issue, this study investigates the cyclic deformation behaviour of WAAM ER70S-6 carbon steel. Coupons were extracted from printed walls with horizontal and vertical orientations and from surface and interior locations. Low-cycle fatigue (LCF) tests were performed under fully reversed strain-controlled conditions, spanning strain amplitudes from 0.20 % to 1.50 %. Regardless of the group, the material exhibited cyclic hardening for strain amplitudes above 0.60 % and cyclic softening for smaller strain amplitudes. Significant non-Masing hysteretic behaviour was also observed. Cyclic stress–strain curves and fatigue-life relationships written in terms of stress, strain and energy-based parameters were derived for all groups. Fatigue life was not significantly influenced by printing orientation or location across thickness. However, horizontal orientation resulted in a slightly superior fatigue response. A statistical analysis revealed no significant difference in the accuracy of fatigue-life relationships between the groups. Finally, a comparative study between WAAM materials and conventional steels showed promising results. Yet, conventional steels outperform WAAM carbon steel, at least doubling the fatigue life for the same value of the damage parameter.