2026 deOliveira CMT WAAM Steel Fatigue

Wire arc additive manufacturing (WAAM) utilizing the cold metal transfer (CMT) process provides significant benefits for the production of large and complex metal parts, but the thermal cycles associated with layer-by-layer deposition lead to microstructural and mechanical variabilities that impact fatigue behavior and fracture mechanisms. This research evaluates the fatigue resistance and fracture characteristics of ER70S-6 steel deposited by CMT-WAAM. Fatigue tests were executed on seven specimens extracted horizontally relative to the deposition direction, employing a load ratio of R = 0.1 and a frequency of 20 Hz. The outcomes revealed a fatigue limit of approximately 302 MPa (/C250.53 Su), aligning with typical low-alloy steel behavior. Notably, the fatigue life was significantly reduced upon reusing a previously tested specimen, highlighting the detrimental effect of prior damage. Fractographic analysis conducted via SEM identified crack initiation at defects, followed by propagation characterized by striations and final fractures dominated by ductile dimples. At elevated stress levels (0.67 Su), a less distinct fracture pattern and greater ductile features were observable, suggesting accelerated crack propagation. These findings emphasize the critical influences of defects, stress levels, and loading history on fatigue performance, offering essential insights for enhancing the reliability of WAAM components under cyclic loading.