On the effect of shielding gas flow on porosity and melt pool geometry in laser powder bed fusion additive manufacturing

Research output: Contribution to journalArticleScientificpeer-review

Abstract

Metal additive manufacturing is moving from rapid prototyping to on-demand manufacturing and even to serial production. Consistent part quality and development of a wider range of available materials are key for wider adoption. This requires control and optimization of various laser and scanning parameters. Therefore, process modeling has been extensively pursued to reduce experimental runs in the search for parameters that produce dense, high-quality parts for the given alloy. However, these optimal parameters remain machine-specific if conditions defined by the machine architecture are not considered. Previous studies have shown that shielding gas flow is one such parameter that affects porosity and mechanical properties of parts produced with laser powder bed fusion. However, a lack of consensus remains regarding which phenomena are responsible for the observed decrease in quality. In this study, the effect of shielding gas flow velocity on porosity and melt pool geometry in laser powder bed fusion additive manufacturing is studied. It is shown that decreasing the gas flow velocity leads to a drastic loss of penetration of single scan tracks, leading to increased lack-of-fusion porosity at the part level. This is attributed to the obstruction of the laser beam by the process-induced vapor plume emissions of the individual tracks being scanned. As the vapor plume, and how effectively it is removed by the shielding gas flow, have a significant effect on the melt pool geometry in laser powder bed fusion, models aiming at predicting the melt pool geometry and attempts to transfer process parameters from one machine to another should consider the effect of the shielding gas flow.

Original languageEnglish
Article number101030
JournalAdditive Manufacturing
Volume32
Early online date3 Jan 2020
DOIs
Publication statusE-pub ahead of print - 3 Jan 2020
MoE publication typeA1 Journal article-refereed

Fingerprint

3D printers
Shielding
Powders
Flow of gases
Fusion reactions
Porosity
Geometry
Lasers
Flow velocity
Vapors
Rapid prototyping
Laser beams
Metals
Scanning
Mechanical properties

Keywords

  • Gas flow
  • Melt pool geometry
  • Porosity
  • Powder bed fusion
  • Vapor plume

Cite this

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abstract = "Metal additive manufacturing is moving from rapid prototyping to on-demand manufacturing and even to serial production. Consistent part quality and development of a wider range of available materials are key for wider adoption. This requires control and optimization of various laser and scanning parameters. Therefore, process modeling has been extensively pursued to reduce experimental runs in the search for parameters that produce dense, high-quality parts for the given alloy. However, these optimal parameters remain machine-specific if conditions defined by the machine architecture are not considered. Previous studies have shown that shielding gas flow is one such parameter that affects porosity and mechanical properties of parts produced with laser powder bed fusion. However, a lack of consensus remains regarding which phenomena are responsible for the observed decrease in quality. In this study, the effect of shielding gas flow velocity on porosity and melt pool geometry in laser powder bed fusion additive manufacturing is studied. It is shown that decreasing the gas flow velocity leads to a drastic loss of penetration of single scan tracks, leading to increased lack-of-fusion porosity at the part level. This is attributed to the obstruction of the laser beam by the process-induced vapor plume emissions of the individual tracks being scanned. As the vapor plume, and how effectively it is removed by the shielding gas flow, have a significant effect on the melt pool geometry in laser powder bed fusion, models aiming at predicting the melt pool geometry and attempts to transfer process parameters from one machine to another should consider the effect of the shielding gas flow.",
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AU - Revuelta, Alejandro

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AU - Ruusuvuori, Kimmo

AU - Puukko, Pasi

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