PSI - Issue 68

Available online at www.sciencedirect.com Structural Integrity Procedia 00 (2025) 000–000 Available online at www.sciencedirect.com ScienceDirect

www.elsevier.com/locate/procedia

ScienceDirect

Procedia Structural Integrity 68 (2025) 480–485

European Conference on Fracture 2024 Enhancing the Fatigue Behavior of PBF-LB In718 Through Surface Quality Optimization Matias Jaskari a *, Timo Rautio a , Aappo Mustakangas a Antti Järvenpää a a FMT-research group, Kerttu Saalasti Institute, University of Oulu, Pajatie 5 85500 Nivala, Finland Abstract This study investigates the fatigue behaviour of heat-treated Inconel 718, fabricated using laser powder-bed fusion (PBF-LB) and subjected to surface treatment by electropolishing. Samples were heat-treated and mechanically polished to reduce surface roughness from 5.2 µm to 0.3 µm. Fatigue testing revealed that electropolishing significantly improved fatigue resistance, increasing the fatigue limit by over 90%, from 220 to 420 MPa. Despite these improvements, the fatigue limit reached only 0.58 times the theoretical ideal value of 1.6*HV, indicating a remaining susceptibility to surface defect-driven fatigue failure. Microstructural analysis via EBSD showed epitaxial grain growth in the build direction, with a homogenous face-centered cubic (FCC) phase, though traces of brittle Laves phase are likely present. Hardness testing indicated minor cyclic softening after higher stress amplitude, with values decreasing from 450 HV to 436 HV. Fracture consistently initiated at the surface, with cracks propagating through cleavage before transitioning to transgranular propagation. Overall, the findings demonstrate that while electropolishing enhances fatigue performance, further optimization is needed to mitigate surface-initiated failures in PBF-LB Inconel 718 components. © 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 ECF24 organizers Keywords: Laser powder-bed fusion; Inconel 718; Fatigue; Surface quality © 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 ECF24 organizers

* Corresponding author E-mail address: matias.jaskari@oulu.fi

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 ECF24 organizers

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 ECF24 organizers 10.1016/j.prostr.2025.06.085