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Additive manufacturing technology is garnering attention as a novel approach for the fabrication of components with complex shapes. Nevertheless, the low fatigue strength of the additive manufactured metals represents a significant challenge. In this study, rotating bending fatigue tests were conducted on additive manufactured maraging steel up to a very high cycle fatigue (VHCF) range (10^8 cycles). The effects of laser peening (LP) on fatigue strength were investigated. LP introduced compressive residual stress near the surface, while tensile residual stress was generated inside. The fracture initiation point of the non-LP specimen was observed to be the surface in the low-cycle range and the interior in the VHCF range. In contrast, all specimens subjected to laser peening fractured from the interior. LP was found to be effective in improving fatigue strength in the low-cycle range, but it was also observed to reduce fatigue strength in the VHCF range. The effect of LP on VHCF strength was discussed by focusing on the stress acting at the fracture initiation point. Furthermore, the distribution of defect size on polished and fractured surfaces of the specimens was evaluated by extreme value statistics. The results demonstrated that these values were approximately the same. Therefore, the evaluation method based on extreme value statistics can predict the size of defects in a larger volume member.

Rights:

• Creative Commons BY-NC-ND Attribution-NonCommercial-NoDerivs 4.0 International
  

Keyword: fatigue strength, additive manufacturing, maraging steel, laser peening, very high cycle fatigue

Date published: 2025-01-01

Publisher: Iron and Steel Institute of Japan

Journal:

• Tetsu-to-Hagane (ISSN: 00211575) vol. 111 issue. 1 TETSU-2024-081

Funding:

• JSPS 23K22627

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.2355/tetsutohagane.tetsu-2024-081

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Updated at: 2025-01-08 16:31:16 +0900

Published on MDR: 2025-01-20 12:30:50 +0900