Heterogeneous effect of aging temperature on the fatigue life of additively manufactured thin-walled 18Ni300 maraging steel tubular specimen

• Published in: Materials & design Vol. 237; p. 112561
• Main Authors: Karolczuk, Aleksander, Kurek, Andrzej, Böhm, Michał, Derda, Szymon, Prażmowski, Mariusz, Kluger, Krzysztof, Żak, Krzysztof, Pejkowski, Łukasz, Seyda, Jan
• Format: Journal Article
• Language: English
• Published: Elsevier 01.01.2024
• Subjects: 18Ni300 maraging steel; Additive manufacturing; Aging temperature; Fatigue life; Fatigue strength; Gaussian process for regression
• ISSN: 0264-1275
• DOI: 10.1016/j.matdes.2023.112561

Optimizing the geometry for material savings, or heat transfer, can yield thin-walled additively manufactured parts. A wall thickness of only a few hatching spaces can be fabricated using laser powder bed fusion (LPBF). However, the unmachined surface quality and subsurface defects in the low-thickness wall put the load-bearing capacity of the manufactured part under scrutiny. This study aimed to determine the fatigue and quasi-static strengths of nominally 0.5-mm thick tubular specimens of LPBF 18Ni300 maraging steel with respect to the aging temperature (AT). The experimental tests were conducted on six batches of unmachined specimens: non-aged and age-hardened for 6 h at different temperatures, i.e., 450, 470, 490, 530, and 585 °C. The void distribution and specimen surface were characterized using X-ray micro-computed tomography. The heterogeneous effect of AT on fatigue life was recognized by a novel application of the Gaussian process for regression. The mechanical properties of a 0.5-mm thick tubular specimen were equal to or higher than those of a full cross-section specimen. Furthermore, the optimal AT to obtain the highest fatigue strength was 520 °C for low-cycle fatigue, decreasing to 480 °C for high-cycle fatigue.