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Characterizing surface finish and fatigue behavior in binder-jet 3D-printed nickel-based superalloy 625

Mostafaei, Amir and Neelapu, Surya and Kisailus, Cameron and Nath, Lauren and Jacobs, Tevis and Chmielus, Markus (2018) Characterizing surface finish and fatigue behavior in binder-jet 3D-printed nickel-based superalloy 625. Additive Manufacturing, 24. pp. 200-209. ISSN 2214-8604

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In this study, the fatigue properties of binder-jet 3D-printed nickel-base superalloy 625 were evaluated. Standard fatigue specimens were printed and sintered, then half of the samples were mechanically ground, while the other half were left in their as-sintered state. They were then characterized using micro-computed x-ray tomography, metallographic sample examination, and optical and stylus profilometry for surface topography. The micro-computed tomography observations showed that density of the as-printed sample was ~50%, while the sintered sample neared full densification (98.9 ± 0.3%) upon sintering at 1285 °C for 4 h in a vacuum atmosphere. The metallographic examination showed equiaxed grains. The roughness of the as-sintered samples was significant with an RMS roughness of Rq = 1.39 ± 0.20 μm as measured over a line-scan of 5 mm, but this was reduced to Rq = 0.47 ± 0.02 μm after mechanical grinding. All samples were tested to failure in fatigue, under fully-reversed tension-compression conditions. While the as-sintered samples showed poor fatigue properties compared to prior reports on cast and milled parts, the ground samples showed superior performance. Scanning electron microscopy observation was conducted on the fractured surfaces and showed that the samples underwent transgranular crack initiation, followed by intergranular crack growth and final failure. In the mechanically ground sample, hardness increased nearly two-fold up to 75 µm beneath the sample’s surface and X-ray diffraction indicated an in-plane compressive stress, grain refinement, and micro-strain on the mechanically ground sample. The reduced roughness, surface hardening, and compressive stress resulted in increased fatigue life of the binder-jetted alloy 625.


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Item Type: Article
Status: Published
CreatorsEmailPitt UsernameORCID
Mostafaei, Amiramir.mostafaei@pitt.eduamir.mostafaei
Neelapu, Suryasun20@pitt.edusun20
Kisailus, Cameroncek74@pitt.educek74
Nath, Laurenlnath@bc.pitt.edulnath
Jacobs, Tevistjacobs@Pitt.edutjacobs0000-0001-8576-914X
Chmielus, Markuschmielus@pitt.educhmielus0000-0002-8688-6054
Date: 1 December 2018
Date Type: Publication
Journal or Publication Title: Additive Manufacturing
Volume: 24
Publisher: Elsevier
Page Range: pp. 200-209
DOI or Unique Handle: 10.1016/j.addma.2018.09.012
Schools and Programs: Swanson School of Engineering > Mechanical Engineering and Materials Science
Refereed: No
Uncontrolled Keywords: Additive manufacturing; Inconel 625; Sintering; Fatigue life; Fractography; Surface roughness; Hardness
ISSN: 2214-8604
Official URL:
Article Type: Research Article
Date Deposited: 12 Dec 2019 12:45
Last Modified: 12 Dec 2019 12:45


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