With growing development in Additive Manufacturing (AM) technologies it is necessary to comprehend the deposited materials behavior to enable them to be safely applied as functional parts. Within the AM processes, Wire and Arc Additive Manufacturing (WAAM) is a method that favors the production of bigger parts while associated with higher deposition rates. In this scope, different metals can be applied, but high-strength low-alloy steels (HSLA) stand out for this type of deposition. When evaluating the fatigue life of these materials however, new aspects should be considered, due to the high thermal rates associated with the WAAM process, the parts produced will have microstructural variation and anisotropic behavior, which will interfere in the part functionality. Thus, this work aims to evaluate the fatigue behavior of SHLA steel ER70S-6, deposited by WAAM with cold metal transfer (CMT). For this, walls with 100-layers were deposited and samples were obtained in horizontal and vertical direction with respect to the deposition. The fatigue tests were caried out with load ratios of R = 0. 1 and frequencies of 5 Hz. Results showed that horizontal specimens exhibited superior fatigue performance across all stress levels. At 350 MPa, the horizontal sample endured 2. 23 times more cycles than the vertical counterpart. While horizontal specimens achieved “infinite life” (≥ 2 × 10⁶ cycles) at 302. 4 MPa, vertical specimens did not reach this threshold. Significant scatter was observed among vertical samples; at 302. 4 MPa, fatigue life ranged from 263, 141 to 821, 180 cycles. Fractography revealed brittle initiation zones and ductile final rupture regions, with low-cycle failures showing homogeneous dimpled surfaces. These findings confirm pronounced anisotropy, with horizontal orientation providing up to 2. 2× higher endurance compared to vertical orientation.
Oliveira et al. (Thu,) studied this question.