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Mechanical behavior of post-processed Inconel 718 manufactured through the electron beam melting process

Journal Article · · Materials Science and Engineering. A, Structural Materials: Properties, Microstructure and Processing
 [1];  [2];  [1];  [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Arcam AB, Molndal (Sweden)

Here, the electron beam melting (EBM) process was used to fabricate Inconel 718. The microstructure and tensile properties were characterized in both the as-fabricated and post-processed state transverse (T-orientation) and longitudinal (L-orientation) to the build direction. Post-processing involved both a hot isostatic pressing (HIP) and solution treatment and aging (STA) to homogenize the microstructure. In the as-fabricated state, EBM Inconel 718 exhibits a spatially dependent microstructure that is a function of build height. Spanning the last few layers is a cored dendritic structure comprised of the products (carbides and Laves phase) predicted under equilibrium solidification conditions. With increasing distance from the build's top surface, the cored dendritic structure becomes increasingly homogeneous with complete dissolution of the secondary dendrite arms. Further, temporal phase kinetics are observed to lead to the dissolution of the strengthening γ"γ" and precipitation of networks of fine δ needles that span the grains. Microstructurally, post-processing resulted in dissolution of the δ networks and homogeneous precipitation of γ'"γ'" throughout the height of the build. In the as-fabricated state, the monotonic tensile behavior exhibits a height sensitivity within the T-orientation at both 20 and 650 °C. Along the L-orientation, the tensile behavior exhibits strength values comparable to the reference wrought material in the fully heat-treated state. After post-processing, the yield strength, ultimate strength, and elongation at failure for the EBM Inconel 718 were observed to have beneficially increased compared to the as-fabricated material. Further, as a result of post-processing the spatial variance of the ultimate yield strength and elongation at failure within the transverse direction decreased by 4 and 3× respectively.

Research Organization:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Manufacturing Demonstration Facility (MDF)
Sponsoring Organization:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
Grant/Contract Number:
AC05-00OR22725
OSTI ID:
1335303
Alternate ID(s):
OSTI ID: 1417102
Journal Information:
Materials Science and Engineering. A, Structural Materials: Properties, Microstructure and Processing, Journal Name: Materials Science and Engineering. A, Structural Materials: Properties, Microstructure and Processing Journal Issue: C Vol. 680; ISSN 0921-5093
Publisher:
ElsevierCopyright Statement
Country of Publication:
United States
Language:
English

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Cited By (8)

Additive Manufacturing of Alloy 718 via Electron Beam Melting: Effect of Post-Treatment on the Microstructure and the Mechanical Properties journal December 2018
Metal Alloys for Fusion-Based Additive Manufacturing journal February 2018
Progress in the Processing and Understanding of Alloy 718 Fabricated Through Powder Bed Additive Manufacturing Processes book January 2018
The Effect of Location and Post-treatment on the Microstructure of EBM-Built Alloy 718 book January 2018
Influence of build layout and orientation on microstructural characteristics of electron beam melted Alloy 718 journal September 2018
Correlation of Microstructure to Creep Response of Hot Isostatically Pressed and Aged Electron Beam Melted Inconel 718 journal July 2018
Damage Tolerance Evaluation of E-PBF-Manufactured Inconel 718 Strut Geometries by Advanced Characterization Techniques journal January 2020
Can Appropriate Thermal Post-Treatment Make Defect Content in as-Built Electron Beam Additively Manufactured Alloy 718 Irrelevant? journal January 2020

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