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Title: Laser-Induced Keyhole Defect Dynamics during Metal Additive Manufacturing

Abstract

Laser powder bed fusion (LPBF) metal additive manufacturing provides distinct advantages for aerospace and biomedical applications. However, widespread industrial adoption is limited by a lack of confidence in part properties driven by an incomplete understanding of how unique process parameters relate to defect formation and ultimately mechanical properties. To address that gap, high-speed X-ray imaging is used to probe subsurface melt pool dynamics and void-formation mechanisms inaccessible to other monitoring approaches. This technique directly observes the depth and dynamic behavior of the vapor depression, also known as the keyhole depression, which is formed by recoil pressure from laser-driven metal vaporization. Also, vapor bubble formation and motion due to melt pool currents is observed, including instances of bubbles splitting before solidification into clusters of smaller voids while the material rapidly cools. Other phenomena include bubbles being formed from and then recaptured by the vapor depression, leaving no voids in the final part. Such events complicate attempts to identify defect formation using surface-sensitive process-monitoring tools. Finally, once the void defects form, they cannot be repaired by simple laser scans, without introducing new defects, thus emphasizing the importance of understanding processing parameters to develop robust defect-mitigation strategies based on experimentally validated models.

Authors:
ORCiD logo [1];  [1];  [2];  [1];  [2];  [2];  [2];  [2];  [3];  [1];  [1];  [3];  [2];  [1];  [1]
+ Show Author Affiliations
  1. SLAC National Accelerator Lab., Menlo Park, CA (United States)
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  3. Ames Lab. and Iowa State Univ., Ames, IA (United States)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES); USDOE National Nuclear Security Administration (NNSA); USDOE Office of Energy Efficiency and Renewable Energy (EERE), Energy Efficiency Office. Advanced Manufacturing Office
OSTI Identifier:
1560679
Alternate Identifier(s):
OSTI ID: 1557328; OSTI ID: 1560982
Report Number(s):
LLNL-JRNL-748807
Journal ID: ISSN 1438-1656; TRN: US2000556
Grant/Contract Number:  
AC02-07CH11358; AC02-76SF00515; SC0012704; AC52-07NA27344
Resource Type:
Accepted Manuscript
Journal Name:
Advanced Engineering Materials
Additional Journal Information:
Journal Volume: 21; Journal Issue: 10; Journal ID: ISSN 1438-1656
Publisher:
Wiley
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING; 36 MATERIALS SCIENCE; additive manufacturing; laser powder bed fusion; titanium; X-ray imaging

Citation Formats

Kiss, Andrew M., Fong, Anthony Y., Calta, Nicholas P., Thampy, Vivek, Martin, Aiden A., Depond, Philip J., Wang, Jenny, Matthews, Manyalibo J., Ott, Ryan T., Tassone, Christopher J., Stone, Kevin H., Kramer, Matthew J., van Buuren, Anthony, Toney, Michael F., and Nelson Weker, Johanna. Laser-Induced Keyhole Defect Dynamics during Metal Additive Manufacturing. United States: N. p., 2019. Web. doi:10.1002/adem.201900455.
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Kiss, Andrew M., Fong, Anthony Y., Calta, Nicholas P., Thampy, Vivek, Martin, Aiden A., Depond, Philip J., Wang, Jenny, Matthews, Manyalibo J., Ott, Ryan T., Tassone, Christopher J., Stone, Kevin H., Kramer, Matthew J., van Buuren, Anthony, Toney, Michael F., & Nelson Weker, Johanna. Laser-Induced Keyhole Defect Dynamics during Metal Additive Manufacturing. United States. https://doi.org/10.1002/adem.201900455
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Kiss, Andrew M., Fong, Anthony Y., Calta, Nicholas P., Thampy, Vivek, Martin, Aiden A., Depond, Philip J., Wang, Jenny, Matthews, Manyalibo J., Ott, Ryan T., Tassone, Christopher J., Stone, Kevin H., Kramer, Matthew J., van Buuren, Anthony, Toney, Michael F., and Nelson Weker, Johanna. Tue . "Laser-Induced Keyhole Defect Dynamics during Metal Additive Manufacturing". United States. https://doi.org/10.1002/adem.201900455. https://www.osti.gov/servlets/purl/1560679.
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@article{osti_1560679,
title = {Laser-Induced Keyhole Defect Dynamics during Metal Additive Manufacturing},
author = {Kiss, Andrew M. and Fong, Anthony Y. and Calta, Nicholas P. and Thampy, Vivek and Martin, Aiden A. and Depond, Philip J. and Wang, Jenny and Matthews, Manyalibo J. and Ott, Ryan T. and Tassone, Christopher J. and Stone, Kevin H. and Kramer, Matthew J. and van Buuren, Anthony and Toney, Michael F. and Nelson Weker, Johanna},
abstractNote = {Laser powder bed fusion (LPBF) metal additive manufacturing provides distinct advantages for aerospace and biomedical applications. However, widespread industrial adoption is limited by a lack of confidence in part properties driven by an incomplete understanding of how unique process parameters relate to defect formation and ultimately mechanical properties. To address that gap, high-speed X-ray imaging is used to probe subsurface melt pool dynamics and void-formation mechanisms inaccessible to other monitoring approaches. This technique directly observes the depth and dynamic behavior of the vapor depression, also known as the keyhole depression, which is formed by recoil pressure from laser-driven metal vaporization. Also, vapor bubble formation and motion due to melt pool currents is observed, including instances of bubbles splitting before solidification into clusters of smaller voids while the material rapidly cools. Other phenomena include bubbles being formed from and then recaptured by the vapor depression, leaving no voids in the final part. Such events complicate attempts to identify defect formation using surface-sensitive process-monitoring tools. Finally, once the void defects form, they cannot be repaired by simple laser scans, without introducing new defects, thus emphasizing the importance of understanding processing parameters to develop robust defect-mitigation strategies based on experimentally validated models.},
doi = {10.1002/adem.201900455},
journal = {Advanced Engineering Materials},
number = 10,
volume = 21,
place = {United States},
year = {2019},
month = {7}
}
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Journal Article:
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Publisher's Version of Record
https://doi.org/10.1002/adem.201900455
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Cited by: 1 work
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Figures / Tables:

Figure 1 Figure 1: The frequency of void defect formation within the fixed field of view (2.048 mm) as the laser power is increased into the keyhole regime for two different laser scan speeds. An arrow indicating the approximate location of the transition to the keyhole regime is drawn to show themore » relationship between keyhole formation and the formation of voids. The faster scan speed shows a linear increase in voids with increased laser power with a slope of 0.05 voids mm-1 w-1. The slow speed shows the same linear dependence after a dramatic increase in void formation between 75 and 100W. The slower scan speed is the average number of voids for two different tracks with the error bars showing one standard deviation. Error bars are not shown for the 455 mm s-1 laser speed because only one run was performed for each power.« less
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Works referenced in this record:

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    Works referencing / citing this record:

    A laser powder bed fusion system for in situ x-ray diffraction with high-energy synchrotron radiation
    journal, July 2020

    • Uhlmann, Eckart; Krohmer, Erwin; Schmeiser, Felix
    • Review of Scientific Instruments, Vol. 91, Issue 7
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    A laser powder bed fusion system for in situ x-ray diffraction with high-energy synchrotron radiation
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    • Uhlmann, Eckart; Krohmer, Erwin; Schmeiser, Felix
    • Deutsches Elektronen-Synchrotron, DESY, Hamburg
    • DOI: 10.3204/pubdb-2020-02554
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