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Title: Metal vapor micro-jet controls material redistribution in laser powder bed fusion additive manufacturing

Abstract

The results of detailed experiments and finite element modeling of metal micro-droplet motion associated with metal additive manufacturing (AM) processes are presented. Ultra high speed imaging of melt pool dynamics reveals that the dominant mechanism leading to micro-droplet ejection in a laser powder bed fusion AM is not from laser induced recoil pressure as is widely believed and found in laser welding processes, but rather from vapor driven entrainment of micro-particles by an ambient gas flow. The physics of droplet ejection under strong evaporative flow is described using simulations of the laser powder bed interactions to elucidate the experimental results. Hydrodynamic drag analysis is used to augment the single phase flow model and explain the entrainment phenomenon for 316 L stainless steel and Ti-6Al-4V powder layers. The relevance of vapor driven entrainment of metal micro-particles to similar fluid dynamic studies in other fields of science will be discussed.

Authors:
 [1];  [2];  [3];  [4];  [1]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Materials Science Division, Physical and Life Sciences Directorate
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Laser Science and Systems Engineering, NIF and Photon Sciences Directorate
  3. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Computational Engineering, Engineering Directorate
  4. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Laser Systems Engineering Operations, Engineering Directorate
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1395471
Grant/Contract Number:
AC52-07NA27344
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Scientific Reports
Additional Journal Information:
Journal Volume: 7; Journal Issue: 1; Journal ID: ISSN 2045-2322
Publisher:
Nature Publishing Group
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Fluid dynamics; Metals and alloys

Citation Formats

Ly, Sonny, Rubenchik, Alexander M., Khairallah, Saad A., Guss, Gabe, and Matthews, Manyalibo J. Metal vapor micro-jet controls material redistribution in laser powder bed fusion additive manufacturing. United States: N. p., 2017. Web. doi:10.1038/s41598-017-04237-z.
Ly, Sonny, Rubenchik, Alexander M., Khairallah, Saad A., Guss, Gabe, & Matthews, Manyalibo J. Metal vapor micro-jet controls material redistribution in laser powder bed fusion additive manufacturing. United States. doi:10.1038/s41598-017-04237-z.
Ly, Sonny, Rubenchik, Alexander M., Khairallah, Saad A., Guss, Gabe, and Matthews, Manyalibo J. Thu . "Metal vapor micro-jet controls material redistribution in laser powder bed fusion additive manufacturing". United States. doi:10.1038/s41598-017-04237-z. https://www.osti.gov/servlets/purl/1395471.
@article{osti_1395471,
title = {Metal vapor micro-jet controls material redistribution in laser powder bed fusion additive manufacturing},
author = {Ly, Sonny and Rubenchik, Alexander M. and Khairallah, Saad A. and Guss, Gabe and Matthews, Manyalibo J.},
abstractNote = {The results of detailed experiments and finite element modeling of metal micro-droplet motion associated with metal additive manufacturing (AM) processes are presented. Ultra high speed imaging of melt pool dynamics reveals that the dominant mechanism leading to micro-droplet ejection in a laser powder bed fusion AM is not from laser induced recoil pressure as is widely believed and found in laser welding processes, but rather from vapor driven entrainment of micro-particles by an ambient gas flow. The physics of droplet ejection under strong evaporative flow is described using simulations of the laser powder bed interactions to elucidate the experimental results. Hydrodynamic drag analysis is used to augment the single phase flow model and explain the entrainment phenomenon for 316 L stainless steel and Ti-6Al-4V powder layers. The relevance of vapor driven entrainment of metal micro-particles to similar fluid dynamic studies in other fields of science will be discussed.},
doi = {10.1038/s41598-017-04237-z},
journal = {Scientific Reports},
number = 1,
volume = 7,
place = {United States},
year = {Thu Jun 22 00:00:00 EDT 2017},
month = {Thu Jun 22 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
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  • We report detailed understanding of the complex melt pool physics plays a vital role in predicting optimal processing regimes in laser powder bed fusion additive manufacturing. In this work, we use high framerate video recording of Selective Laser Melting (SLM) to provide useful insight on the laser-powder interaction and melt pool evolution of 316 L powder layers, while also serving as a novel instrument to quantify cooling rates of the melt pool. The experiment was performed using two powder types – one gas- and one water-atomized – to further clarify how morphological and chemical differences between these two feedstock materialsmore » influence the laser melting process. Finally, experimentally determined cooling rates are compared with values obtained through computer simulation, and the relationship between cooling rate and grain cell size is compared with data previously published in the literature.« less
  • Additive manufacturing (AM) has the potential to revolutionize discrete part manufacturing, but improvements in processing of metallic materials are necessary before AM will see widespread adoption. A better understanding of AM processes, resulting from physics-based modeling as well as direct process metrology, will form the basis for these improvements. Infrared (IR) thermography of AM processes can provide direct process metrology, as well as data necessary for the verification of physics-based models. We review selected works examining how IR thermography was implemented and used in various powder-bed AM processes. This previous work, as well as significant experience at the National Institutemore » of Standards and Technology in temperature measurement and IR thermography for machining processes, shapes our own research in AM process metrology with IR thermography. We discuss our experimental design, as well as plans for future IR measurements of a laser-based powder bed fusion AM process.« less
  • The production of metal parts via laser powder bed fusion additive manufacturing is growing exponentially. However, the transition of this technology from production of prototypes to production of critical parts is hindered by a lack of confidence in the quality of the part. Confidence can be established via a fundamental understanding of the physics of the process. It is generally accepted that this understanding will be increasingly achieved through modeling and simulation. However, there are significant physics, computational, and materials challenges stemming from the broad range of length and time scales and temperature ranges associated with the process. In thismore » paper, we review the current state of the art and describe the challenges that need to be met to achieve the desired fundamental understanding of the physics of the process.« less
  • The production of metal parts via laser powder bed fusion additive manufacturing is growing exponentially. However, the transition of this technology from production of prototypes to production of critical parts is hindered by a lack of confidence in the quality of the part. Confidence can be established via a fundamental understanding of the physics of the process. It is generally accepted that this understanding will be increasingly achieved through modeling and simulation. However, there are significant physics, computational, and materials challenges stemming from the broad range of length and time scales and temperature ranges associated with the process. In thismore » study, we review the current state of the art and describe the challenges that need to be met to achieve the desired fundamental understanding of the physics of the process.« less