University of Oulu

Khedr M, Hamada A, Abd-Elaziem W, Jaskari M, Elsamanty M, Kömi J, Järvenpää A. Effects of Wall Thickness Variation on Hydrogen Embrittlement Susceptibility of Additively Manufactured 316L Stainless Steel with Lattice Auxetic Structures. Materials. 2023; 16(6):2523.

Effects of wall thickness variation on hydrogen embrittlement susceptibility of additively manufactured 316L stainless steel with lattice auxetic structures

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Author: Khedr, Mahmoud1,2; Hamada, Atef2; Abd-Elaziem, Walaa3;
Organizations: 1Mechanical Engineering Department, Faculty of Engineering at Shoubra, Benha University, Cairo 11629, Egypt
2Kerttu Saalasti Institute, Future Manufacturing Technologies (FMT), University of Oulu, 85500 Nivala, Finland
3Department of Mechanical Design and Production Engineering, Faculty of Engineering, Zagazig University, Zagazig 44519, Egypt
4Mechatronics and Robotics Department, School of Innovative Design Engineering, Egypt-Japan University of Science and Technology, Alexandria 21934, Egypt
5Materials and Mechanical Engineering, Centre for Advanced Steel Research, University of Oulu, 90014 Oulu, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 5.5 MB)
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Language: English
Published: Multidisciplinary Digital Publishing Institute, 2023
Publish Date: 2023-08-21


In the present study, the hydrogen embrittlement (HE) susceptibility of an additively manufactured (AM) 316L stainless steel (SS) was investigated. The materials were fabricated in the form of a lattice auxetic structure with three different strut thicknesses, 0.6, 1, and 1.4 mm, by the laser powder bed fusion technique at a volumetric energy of 70 J·mm⁻³. The effect of H charging on the strength and ductility of the lattice structures was evaluated by conducting tensile testing of the H-charged specimens at a slow strain rate of 4 × 10⁻⁵ s⁻¹. Hydrogen was introduced to the specimens via electrochemical charging in an NaOH aqueous solution for 24 h at 80 °C before the tensile testing. The microstructure evolution of the H-charged materials was studied using the electron backscattered diffraction (EBSD) technique. The study revealed that the auxetic structures of the AM 316L-SS exhibited a slight reduction in mechanical properties after H charging. The tensile strength was slightly decreased regardless of the thickness. However, the ductility was significantly reduced with increasing thickness. For instance, the strength and uniform elongation of the auxetic structure of the 0.6 mm thick strut were 340 MPa and 17.4% before H charging, and 320 MPa and 16.7% after H charging, respectively. The corresponding values of the counterpart’s 1.4 mm thick strut were 550 MPa and 29% before H charging, and 523 MPa and 23.9% after H charging, respectively. The fractography of the fracture surfaces showed the impact of H charging, as cleavage fracture was a striking feature in H-charged materials. Furthermore, the mechanical twins were enhanced during tensile straining of the H-charged high-thickness material.

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Series: Materials
ISSN: 1996-1944
ISSN-E: 1996-1944
ISSN-L: 1996-1944
Volume: 16
Issue: 6
Article number: 2523
DOI: 10.3390/ma16062523
Type of Publication: A1 Journal article – refereed
Field of Science: 214 Mechanical engineering
216 Materials engineering
Funding: This research was funded by [the Council of Oulu Region and the European Union (European Regional Development Fund) for the M3D project and Business Finland for the DREAMS (Database for Radically Enhancing Additive Manufacturing and Standardization) project, grant number: 4795/31/2021].
Copyright information: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (