PSI - Issue 79

Available online at www.sciencedirect.com

ScienceDirect

Procedia Structural Integrity 79 (2026) 248–258

28th International Conference on Fracture and Structural Integrity - 3rd Mediterranean Conference on Fracture and Structural Integrity Fatigue Evaluation of WAAM-CMT HSLA Steel: Experimental S– N Curve Analysis Considering Deposition Direction Déborah de Oliveira a *, Daniel Víctor Carvalho Lima a , Rodrigo Souza Pimenta a , Thiago Doca a , José Alexander Araújo a , Maksym Ziberov a a University of Brasilia, Mechanical Engineering Department, Asa Norte, Brasília Zip code: 70.910-900, Brazil Abstract 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 × 10^6 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.

© 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of IGF28 - MedFract3 organizers Keywords: Additive Manufacturing; WAAM; Fatigue life; Fracture evaluation.

* Corresponding author. Tel.: +55 61 3107-5503; fax: +55 61 3107-5503 E-mail address: oliveira.deborah@unb.br

2452-3216 © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of IGF28 - MedFract3 organizers 10.1016/j.prostr.2025.12.331