Oxygen balance during laser powder bed fusion of Alloy 718

Pauzon, Camille Nicole Géraldine; Raza, Ahmad; Hryha, Eduard; Forêt, Pierre

doi:10.1016/j.matdes.2021.109511

Cited by 30 publications

(21 citation statements)

References 11 publications

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“…At high temperatures, about 2000 • C, and under thermodynamic equilibrium, the melt contains 0.1 wt % (1000 ppm) nitrogen under 1 bar of N 2 compared to only 0.003 wt % (30 ppm) under 0.002 bar of N 2 when using Ar as the main process gas. However, because of the rapid cooling conditions during L-PBF (approximately 10 7 K/s [13]), the melt pool lifetime is very limited. Still, the calculated phase diagram allows pointing out that the nitrogen equilibrium concentration is higher for high nitrogen pressure (e.g., at 1100 • C, approximately 2.5 wt % N 2 for 1 bar, and 0.5 wt % N 2 for 0.002 bar).…”

Section: Discussionmentioning

confidence: 99%

“…Gruber et al [12] revealed that the degradation of the used powder and its recycling was associated with the increased presence of oxide inclusions and related lack-of-fusion defects in the as-built material. Recent work by authors with focus on the in-depth characterization of the powder degradation during L-PBF of Alloy 718 highlighted the development of Al and Cr oxide patches on the spatters when using Ar as the processing atmosphere, in addition to the thin Ni oxide layer characteristic of the feedstock powder [13]. It was shown that spatter particles picked up more than 300 ppm of oxygen from the process atmosphere after one processing cycle.…”

Section: Introductionmentioning

confidence: 99%

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Effect of the Process Atmosphere Composition on Alloy 718 Produced by Laser Powder Bed Fusion

Pauzon

Markström²,

Goff

et al. 2021

Metals

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The detrimental effect of nitrogen and oxygen when it comes to the precipitation of the strengthening γ’’ and γ’ phases in Alloy 718 is well-known from traditional manufacturing. Hence, the influence of the two processing atmospheres, namely argon and nitrogen, during the laser powder bed fusion (L-PBF) of Alloy 718 parts was studied. Regardless of the gas type, considerable losses of both oxygen of about 150 ppm O2 (≈30%) and nitrogen on the level of around 400 ppm N2 (≈25%) were measured in comparison to the feedstock powder. The utilization of nitrogen as processing atmosphere led to a slightly higher nitrogen content in the as-built material—about 50 ppm—compared to the argon atmosphere. The presence of the stable nitrides and Al-rich oxides observed in the as-built material was related to the transfer of these inclusions from the nitrogen atomized powder feedstock to the components. This was confirmed by dedicated analysis of the powder feedstock and supported by thermodynamic and kinetic calculations. Rapid cooling rates were held responsible for the limited nitrogen pick-up. Oxide dissociation during laser–powder interaction, metal vaporization followed by oxidation and spatter generation, and their removal by processing atmosphere are the factors describing an important oxygen loss during L-PBF. In addition, the reduction of the oxygen level in the process atmosphere from 500 to 50 ppm resulted in the reduction in the oxygen level in as-built component by about 5%.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of the Process Atmosphere Composition on Alloy 718 Produced by Laser Powder Bed Fusion

Pauzon

Markström²,

Goff

et al. 2021

Metals

Self Cite

View full text Add to dashboard Cite

show abstract

“…The ratio of the particle's surface area to volume-denoted by SA/V-was also of interest because this ratio serves as a metric of a powder's affinity to adsorbing specific compounds on its surface; this is a commonly utilized metric to observe surface energyrelated changes associated with the SA/V ratio [26,27]. Given that the Microtrac does not provide 3D measurements, the calculations of surface area and volume are solely approximations based upon the particle's 2D image profile, resulting in an approximation of the SA/V ratio; more accurate estimations of the SA/V ratio could be completed using Brunauer-Emmett-Teller (BET) measurements for surface area quantification and 3D particle size/shape analysis for volume calculations.…”

Section: Influential Factors On Powder Properties and Behaviormentioning

confidence: 99%

Exploration of the Effects of Metallic Powder Handling and Storage Conditions on Flowability and Moisture Content for Additive Manufacturing Applications

Grubbs

Sousa

Cote

2022

Metals

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Metal powder-based additive manufacturing (AM) relies on consistently successful processing of feedstock powder, necessitating through-process predictability in powder properties and behavior. However, routine powder handling and storage may degrade powder performance by influencing flowability and moisture content through exposure to ambient conditions. Therefore, this study aimed to evaluate the effects of repeated environmental exposure on the flowability and moisture content of Al 5056 and Ta powders for AM applications. Using Carney Funnel flow tests, thermogravimetric analysis, and particle size/shape analysis, powder characterization helped elucidate powder property and behavioral changes with exposure. Results indicated inconsistent flowability and moisture content changes for both material types when exposure conditions were altered. Correlational statistics highlighted the most influential particle characteristics on powder behavior after exposure; particle morphology was most impactful for the semi-spherical Al 5056, whereas moisture content and particle size were most significant for the angular Ta. While exposure to laboratory conditions minimally changed powder performance in this study, caution is advised when handling and storing powders in more “extreme” environments. Powder users are urged to implement quality controls alongside powder characterization to pinpoint how specific powders should be treated, handled, and stored in a given environment for successful processing in AM.

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“…Firstly, in a commercial L-PBF system, the oxygen level is typically controlled at a level lower than 1000 ppm, which is not sufficiently low to prevent surface oxidation [8,9]. Based on simulations, in L-PBF process the powder in close proximity of the part is heated to elevated temperatures due to the heat conduction from the printed part [10].…”

Section: Introductionmentioning

confidence: 99%

Influence of part geometry on spatter formation in laser powder bed fusion of Inconel 718 alloy revealed by optical tomography

Chen

Raza

Hryha

2022

Journal of Manufacturing Processes

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Oxygen balance during laser powder bed fusion of Alloy 718

Cited by 30 publications

References 11 publications

Effect of the Process Atmosphere Composition on Alloy 718 Produced by Laser Powder Bed Fusion

Effect of the Process Atmosphere Composition on Alloy 718 Produced by Laser Powder Bed Fusion

Exploration of the Effects of Metallic Powder Handling and Storage Conditions on Flowability and Moisture Content for Additive Manufacturing Applications

Influence of part geometry on spatter formation in laser powder bed fusion of Inconel 718 alloy revealed by optical tomography

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