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

Authors:
; ; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1400076
Report Number(s):
LLNL-JRNL-709140
Journal ID: ISSN 2045-2322
DOE Contract Number:
AC52-07NA27344
Resource Type:
Journal Article
Resource Relation:
Journal Name: Scientific Reports; Journal Volume: 7; Journal Issue: 1
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

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. 2017. "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/1400076.
@article{osti_1400076,
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 = {},
doi = {10.1038/s41598-017-04237-z},
journal = {Scientific Reports},
number = 1,
volume = 7,
place = {United States},
year = 2017,
month = 6
}
  • 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.more » 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.« less
  • 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 materials influence themore » 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
  • 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
  • Our study demonstrates the significant effect of the recoil pressure and Marangoni convection in laser powder bed fusion (L-PBF) of 316L stainless steel. A three-dimensional high fidelity powder-scale model reveals how the strong dynamical melt flow generates pore defects, material spattering (sparking), and denudation zones. The melt track is divided into three sections: a topological depression, a transition and a tail region, each being the location of specific physical effects. The inclusion of laser ray-tracing energy deposition in the powder-scale model improves over traditional volumetric energy deposition. It enables partial particle melting, which impacts pore defects in the denudation zone.more » Different pore formation mechanisms are observed at the edge of a scan track, at the melt pool bottom (during collapse of the pool depression), and at the end of the melt track (during laser power ramp down). Finally, we discuss remedies to these undesirable pores are discussed. The results are validated against the experiments and the sensitivity to laser absorptivity.« less