PSI - Issue 68

ScienceDirect Available online at www.sciencedirect.com ScienceDirect Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2025) 000–000 Available online at www.sciencedirect.com Procedia Structural Integrity 68 (2025) 981–987

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Structural Integrity Procedia 00 (2025) 000–000

www.elsevier.com/locate/procedia

European Conference on Fracture 2024 Effects of post-heat treatment on the mechanical properties of additive manufactured 316L stainless steel and Inconel 625 super alloy Yasith H. Rajashilpage a , Rasid A. Yildiz a , Mohammad Malekan a, * a Centre for Industrial Mechanics, Institute of Mechanical and Electrical Engineering, University of Southern Denmark, 6400 Sønderborg, Denmark Abstract In this work, the laser powder bed fusion technique was utilized to fabricate samples from two different materials: stainless steel 316L (SS 316L) and Inconel 625 (IN625). The main aim of this study is to explore how the mechanical properties, specifically tensile strength and hardness, of these materials are affected by post-heat treatment. Annealing was chosen as the post-heat treatment method for this research. The investigation primarily focused on evaluating tensile strength and Brinell hardness (HRB) properties. Following post-heat treatment, both SS 316L and IN625 displayed a decrease in elongation and an increase in ultimate tensile strength (UTS) at lower temperatures, approximately 700°C and 900°C. As the annealing temperatures increased, elongation gradually improved while UTS decreased. Higher annealing temperatures, reaching up to 1100°C, tended to restore elongation to around 78% to 95% of the as-built conditions. In terms of hardness properties, both low and high-temperature annealing resulted in a reduction in hardness, with higher temperatures leading to a more significant decrease. The decline in HRB values ranged from 5 to 10 HRB across the lower and higher annealing temperature range. Moreover, elevating printing variables like layer thickness and scanning speed, in addition to post-heat treatment, led to a progressive decrease in mechanical characteristics. The most significant degradation is noted with an 80 µm layer thickness and 2000 mm/s scanning speed, resulting in a 92-94% decrease in elongation compared to as-built samples, and a reduction in UTS by 300-350 MPa for IN625 and 200-250 MPa for SS 316L. Keywords: Additive manufacturing; Heat treatment; Stainless steel 316L; Tensile testing; Hardness testing. 1. Introduction Laser powder bed fusion (PBF) is a prominent metal additive manufacturing (AM) technique that has seen significant advancements, particularly in aerospace, biomedical, and marine applications. AM builds components layer by layer, offering advantages over traditional methods, such as precise dimensional accuracy and the capability to produce complex geometries. It encompasses seven primary techniques: Vat photopolymerization, Binder jetting, Material European Conference on Fracture 2024 Effects of post-heat treatment on the mechanical properties of additive manufactured 316L stainless steel and Inconel 625 super alloy Yasith H. Rajashilpage a , Rasid A. Yildiz a , Mohammad Malekan a, * a Centre for Industrial Mechanics, Institute of Mechanical and Electrical Engineering, University of Southern Denmark, 6400 Sønderborg, Denmark Abstract In this work, the laser powder bed fusion technique was utilized to fabricate samples from two different materials: stainless steel 316L (SS 316L) and Inconel 625 (IN625). The main aim of this study is to explore how the mechanical properties, specifically tensile strength and hardness, of these materials are affected by post-heat treatment. Annealing was chosen as the post-heat treatment method for this research. The investigation primarily focused on evaluating tensile strength and Brinell hardness (HRB) properties. Following post-heat treatment, both SS 316L and IN625 displayed a decrease in elongation and an increase in ultimate tensile strength (UTS) at lower temperatures, approximately 700°C and 900°C. As the annealing temperatures increased, elongation gradually improved while UTS decreased. Higher annealing temperatures, reaching up to 1100°C, tended to restore elongation to around 78% to 95% of the as-built conditions. In terms of hardness properties, both low and high-temperature annealing resulted in a reduction in hardness, with higher temperatures leading to a more significant decrease. The decline in HRB values ranged from 5 to 10 HRB across the lower and higher annealing temperature range. Moreover, elevating printing variables like layer thickness and scanning speed, in addition to post-heat treatment, led to a progressive decrease in mechanical characteristics. The most significant degradation is noted with an 80 µm layer thickness and 2000 mm/s scanning speed, resulting in a 92-94% decrease in elongation compared to as-built samples, and a reduction in UTS by 300-350 MPa for IN625 and 200-250 MPa for SS 316L. Keywords: Additive manufacturing; Heat treatment; Stainless steel 316L; Tensile testing; Hardness testing. 1. Introduction Laser powder bed fusion (PBF) is a prominent metal additive manufacturing (AM) technique that has seen significant advancements, particularly in aerospace, biomedical, and marine applications. AM builds components layer by layer, offering advantages over traditional methods, such as precise dimensional accuracy and the capability to produce complex geometries. It encompasses seven primary techniques: Vat photopolymerization, Binder jetting, Material © 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. Tel.: +45-6550-8607. E-mail address: malekan@sdu.dk

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.2025.06.160 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 * Corresponding author. Tel.: +45-6550-8607. E-mail address: malekan@sdu.dk