scholarly journals Microstructure evolution and mechanical response-based shortening of thermal post-treatment for electron beam melting (EBM) produced Alloy 718

2021 ◽  
pp. 141515
Author(s):  
Sneha Goel ◽  
Enrico Zaninelli ◽  
Tejas Gundgire ◽  
Magnus Ahlfors ◽  
Olanrewaju Ojo ◽  
...  
Keyword(s):  
Electron Beam ◽  
Microstructure Evolution ◽  
Electron Beam Melting ◽  
Mechanical Response ◽  
Post Treatment ◽  
Alloy 718

scholarly journals Additive Manufacturing of Alloy 718 via Electron Beam Melting: Effect of Post-Treatment on the Microstructure and the Mechanical Properties

Materials ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 68 ◽  
Author(s):  
Arun Balachandramurthi ◽  
Johan Moverare ◽  
Satyapal Mahade ◽  
Robert Pederson
Keyword(s):  
Electron Beam ◽  
Additive Manufacturing ◽  
Electron Beam Melting ◽  
Elevated Temperatures ◽  
Microstructural Analysis ◽  
Solution Treatment ◽  
Post Treatment ◽  
Alloy 718 ◽  
Machined Surface ◽  
Contour Region

Alloy 718 finds application in gas turbine engine components, such as turbine disks, compressor blades and so forth, due to its excellent mechanical and corrosion properties at elevated temperatures. Electron beam melting (EBM) is a recent addition to the list of additive manufacturing processes and has shown the capability to produce components with unique microstructural features. In this work, Alloy 718 specimens were manufactured using the EBM process with a single batch of virgin plasma atomized powder. One set of as-built specimens was subjected to solution treatment and ageing (STA); another set of as-built specimens was subjected to hot isostatic pressing (HIP), followed by STA (and referred to as HIP+STA). Microstructural analysis of as-built specimens, STA specimens and HIP+STA specimens was carried out using optical microscopy and scanning electron microscopy. Typical columnar microstructure, which is a characteristic of the EBM manufactured alloy, was observed. Hardness evaluation of the as-built, STA and HIP+STA specimens showed that the post-treatments led to an increase in hardness in the range of ~50 HV1. Tensile properties of the three material conditions (as-built, STA and HIP+STA) were evaluated. Post-treatments lead to an increase in the yield strength (YS) and the ultimate tensile strength (UTS). HIP+STA led to improved elongation compared to STA due to the closure of defects but YS and UTS were comparable for the two post-treatment conditions. Fractographic analysis of the tensile tested specimens showed that the closure of shrinkage porosity and the partial healing of lack of fusion (LoF) defects were responsible for improved properties. Fatigue properties were evaluated in both STA and HIP+STA conditions. In addition, three surface conditions were also investigated, namely the ‘raw’ as-built surface, the machined surface with the contour region and the machined surface without the contour region. Machining off the contour region completely together with HIP+STA led to significant improvement in fatigue performance.

scholarly journals Can Appropriate Thermal Post-Treatment Make Defect Content in as-Built Electron Beam Additively Manufactured Alloy 718 Irrelevant?

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 536 ◽  
Author(s):  
Sneha Goel ◽  
Kévin Bourreau ◽  
Jonas Olsson ◽  
Uta Klement ◽  
Shrikant Joshi
Keyword(s):  
Electron Beam ◽  
Process Optimization ◽  
Electron Beam Melting ◽  
Phase Distribution ◽  
Hot Isostatic Pressing ◽  
Alloy 718 ◽  
Proof Of Concept ◽  
Defect Content ◽  
Enhancing Production ◽  
Hardness Values

Electron beam melting (EBM) is gaining rapid popularity for production of complex customized parts. For strategic applications involving materials like superalloys (e.g., Alloy 718), post-treatments including hot isostatic pressing (HIPing) to eliminate defects, and solutionizing and aging to achieve the desired phase constitution are often practiced. The present study specifically explores the ability of the combination of the above post-treatments to render the as-built defect content in EBM Alloy 718 irrelevant. Results show that HIPing can reduce defect content from as high as 17% in as-built samples (intentionally generated employing increased processing speeds in this illustrative proof-of-concept study) to <0.3%, with the small amount of remnant defects being mainly associated with oxide inclusions. The subsequent solution and aging treatments are also found to yield virtually identical phase distribution and hardness values in samples with vastly varying as-built defect contents. This can have considerable implications in contributing to minimizing elaborate process optimization efforts as well as slightly enhancing production speeds to promote industrialization of EBM for applications that demand the above post-treatments.

scholarly journals Encapsulation of Electron Beam Melting Produced Alloy 718 to Reduce Surface Connected Defects by Hot Isostatic Pressing

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1226 ◽  
Author(s):  
Yunus Emre Zafer ◽  
Sneha Goel ◽  
Ashish Ganvir ◽  
Anton Jansson ◽  
Shrikant Joshi
Keyword(s):  
Electron Beam ◽  
Electron Beam Melting ◽  
Surface Defects ◽  
High Surface ◽  
Hot Isostatic Pressing ◽  
Coated Sample ◽  
Alloy 718 ◽  
Isostatic Pressing ◽  
Before And After ◽  
X Ray Computed

Defects in electron beam melting (EBM) manufactured Alloy 718 are inevitable to some extent, and are of concern as they can degrade mechanical properties of the material. Therefore, EBM-manufactured Alloy 718 is typically subjected to post-treatment to improve the properties of the as-built material. Although hot isostatic pressing (HIPing) is usually employed to close the defects, it is widely known that HIPing cannot close open-to-surface defects. Therefore, in this work, a hypothesis is formulated that if the surface of the EBM-manufactured specimen is suitably coated to encapsulate the EBM-manufactured specimen, then HIPing can be effective in healing such surface-connected defects. The EBM-manufactured Alloy 718 specimens were coated by high-velocity air fuel (HVAF) spraying using Alloy 718 powder prior to HIPing to evaluate the above approach. X-ray computed tomography (XCT) analysis of the defects in the same coated sample before and after HIPing showed that some of the defects connected to the EBM specimen surface were effectively encapsulated by the coating, as they were closed after HIPing. However, some of these surface-connected defects were retained. The reason for such remnant defects is attributed to the presence of interconnected pathways between the ambient and the original as-built surface of the EBM specimen, as the specimens were not coated on all sides. These pathways were also exaggerated by the high surface roughness of the EBM material and could have provided an additional path for argon infiltration, apart from the uncoated sides, thereby hindering complete densification of the specimen during HIPing.

scholarly journals Geometry-Induced Spatial Variation of Microstructure Evolution During Selective Electron Beam Melting of Rene-N5

2018 ◽  
Vol 49 (10) ◽  
pp. 5080-5096 ◽  
Author(s):  
Curtis Lee Frederick ◽  
Alexander Plotkowski ◽  
Michael M. Kirka ◽  
Michael Haines ◽  
Austin Staub ◽  
...  
Keyword(s):  
Electron Beam ◽  
Spatial Variation ◽  
Microstructure Evolution ◽  
Electron Beam Melting ◽  
Selective Electron Beam Melting

scholarly journals How electron beam melting tailors the Al-sensitive microstructure and mechanical response of a novel process-adapted γ-TiAl based alloy

2021 ◽  
pp. 110187
Author(s):  
David Wimler ◽  
Katharina Käsznar ◽  
Michael Musi ◽  
Christoph Breuning ◽  
Matthias Markl ◽  
...  
Keyword(s):  
Electron Beam ◽  
Electron Beam Melting ◽  
Mechanical Response

scholarly journals Characterization of Spatter and Sublimation in Alloy 718 during Electron Beam Melting

Materials ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 5953
Author(s):  
Ahmad Raza ◽  
Eduard Hryha
Keyword(s):  
Electron Beam ◽  
Electron Beam Melting ◽  
Elevated Temperatures ◽  
Ion Beam ◽  
High Vacuum ◽  
Alloying Elements ◽  
Heat Shield ◽  
Alloy 718 ◽  
Feedstock Powder ◽  
Heat Shields

Due to elevated temperatures and high vacuum levels in electron beam melting (EBM), spatter formation and accumulation in the feedstock powder, and sublimation of alloying elements from the base feedstock powder can affect the feedstock powder’s reusability and change the alloy composition of fabricated parts. This study focused on the experimental and thermodynamic analysis of spatter particles generated in EBM, and analyzed sublimating alloying elements from Alloy 718 during EBM. Heat shields obtained after processing Alloy 718 in an Arcam A2X plus machine were analyzed to evaluate the spatters and metal condensate. Comprehensive morphological, microstructural, and chemical analyses were performed using scanning electron microscopy (SEM), focused ion beam (FIB), and energy dispersive spectroscopy (EDS). The morphological analysis showed that the area coverage of heat shields by spatter increased from top (<1%) to bottom (>25%), indicating that the spatter particles had projectile trajectories. Similarly, the metal condensate had a higher thickness of ~50 μm toward the bottom of the heat shield, indicating more significant condensation of metal vapors at the bottom. Microstructural analysis of spatters highlighted that the surfaces of spatter particles sampled from the heat shields were also covered with condensate, and the thickness of the deposited condensate depended on the time of landing of spatter particles on the heat shield during the build. The chemical analysis showed that the spatter particles had 17-fold higher oxygen content than virgin powder used in the build. Analysis of the metalized layer indicated that it was formed by oxidized metal condensate and was significantly enriched with Cr due to its higher vapor pressure under EBM conditions.

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