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Open AccessFeature PaperArticle

Laser Powder Bed Fusion of Inconel 718: Residual Stress Analysis Before and After Heat Treatment

1
ISEP—School of Engineering, Polytechnic of Porto, Rua Dr. António Bernardino de Almeida, 431, 4249—015 Porto, Portugal
2
Department of Applied Science and Technology (DISAT), Politecnico di Torino, Corso Duca degli Abruzzi, 24, 10129 Torino (TO), Italy
3
Department of Management and Production Engineering (DIGEP), Politecnico di Torino, Corso Duca degli Abruzzi, 24, 10129 Torino (TO), Italy
*
Author to whom correspondence should be addressed.
Metals 2019, 9(12), 1290; https://doi.org/10.3390/met9121290
Received: 28 October 2019 / Revised: 23 November 2019 / Accepted: 26 November 2019 / Published: 30 November 2019
Residual stresses (RS) of great magnitude are usually present in parts produced by Laser Powder Bed Fusion (PBF-LB), mainly owing to the extreme temperature gradients and high cooling rates involved in the process. Those “hidden” stresses can be detrimental to a part’s mechanical properties and fatigue life; therefore, it is crucial to know their magnitude and orientation. The hole-drilling strain-gage method was used to determine the RS magnitude and direction-depth profiles. Cuboid specimens in the as-built state, and after standard solution annealing and ageing heat treatment conditions, were prepared to study the RS evolution throughout the heat treatment stages. Measurements were performed on the top and lateral surfaces. In the as-built specimens, tensile stresses of ~400 MPa on the top and above 600 MPa on the lateral surface were obtained. On the lateral surface, RS anisotropy was noticed, with the horizontally aligned stresses being three times lower than the vertically aligned. RS decreased markedly after the first heat treatment. On heat-treated specimens, magnitude oscillations were observed. By microstructure analysis, the presence of carbides was verified, which is a probable root for the oscillations. Furthermore, compressive stresses immediate to the surface were obtained in heat-treated specimens, which is not in agreement with the typical characteristics of parts fabricated by PBF-LB, i.e., tensile stresses at the surface and compressive stresses in the part’s core. View Full-Text
Keywords: metals additive manufacturing; PBF-LB; superalloy; hole-drilling strain-gage method; heat treatments; residual stress; microstructure metals additive manufacturing; PBF-LB; superalloy; hole-drilling strain-gage method; heat treatments; residual stress; microstructure
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MDPI and ACS Style

Barros, R.; Silva, F.J.G.; Gouveia, R.M.; Saboori, A.; Marchese, G.; Biamino, S.; Salmi, A.; Atzeni, E. Laser Powder Bed Fusion of Inconel 718: Residual Stress Analysis Before and After Heat Treatment. Metals 2019, 9, 1290. https://doi.org/10.3390/met9121290

AMA Style

Barros R, Silva FJG, Gouveia RM, Saboori A, Marchese G, Biamino S, Salmi A, Atzeni E. Laser Powder Bed Fusion of Inconel 718: Residual Stress Analysis Before and After Heat Treatment. Metals. 2019; 9(12):1290. https://doi.org/10.3390/met9121290

Chicago/Turabian Style

Barros, Rafael; Silva, Francisco J.G.; Gouveia, Ronny M.; Saboori, Abdollah; Marchese, Giulio; Biamino, Sara; Salmi, Alessandro; Atzeni, Eleonora. 2019. "Laser Powder Bed Fusion of Inconel 718: Residual Stress Analysis Before and After Heat Treatment" Metals 9, no. 12: 1290. https://doi.org/10.3390/met9121290

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