Smoke Suppression in Electron Beam Melting of Inconel 718 Alloy Powder Based on Insulator–Metal Transition of Surface Oxide Film by Mechanical Stimulation

In powder bed fusion–electron beam melting, the alloy powder can scatter under electron beam irradiation. When this phenomenon—known as smoking—occurs, it makes the PBF-EBM process almost impossible. Therefore, avoiding smoking in EBM is an important research issue. In this study, we aimed to clarif...

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Bibliographic Details
Published in:Materials 2021-08, Vol.14 (16), p.4662
Main Authors: Chiba, Akihiko, Daino, Yohei, Aoyagi, Kenta, Yamanaka, Kenta
Format: Article
Language:English
Subjects:
Additive manufacturing
Alloy powders
Ball milling
Chemical composition
Direct current
Electrical properties
Electron beam melting
Electron irradiation
Heating
High temperature
Lattice strain
Nickel
Nickel base alloys
Optimization
Oxide coatings
Particle size
Photoelectrons
Powder beds
R&D
Research & development
Residual stress
Room temperature
Scanning electron microscopy
Smoking
Spectrum analysis
Stimulation
Superalloys
Temperature
Titanium alloys
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Summary:In powder bed fusion–electron beam melting, the alloy powder can scatter under electron beam irradiation. When this phenomenon—known as smoking—occurs, it makes the PBF-EBM process almost impossible. Therefore, avoiding smoking in EBM is an important research issue. In this study, we aimed to clarify the effects of powder bed preheating and mechanical stimulation on the suppression of smoking in the powder bed fusion–electron beam melting process. Direct current electrical resistivity and alternating current impedance spectroscopy measurements were conducted on Inconel 718 alloy powder at room temperature and elevated temperatures before and after mechanical stimulation (ball milling for 10–60 min) to investigate changes in the electrical properties of the surface oxide film, alongside X-ray photoelectron spectroscopy to identify the surface chemical composition. Smoking tests confirmed that preheating and ball milling both suppressed smoking. Furthermore, smoking did not occur after ball milling, even when the powder bed was not preheated. This is because the oxide film undergoes a dielectric–metallic transition due to the lattice strain introduced by ball milling. Our results are expected to benefit the development of the powder bed fusion–electron beam melting processes from the perspective of materials technology and optimization of the process conditions and powder properties to suppress smoking.
ISSN:1996-1944
1996-1944
DOI:10.3390/ma14164662