Keyhole fluctuation and pore formation mechanisms during laser powder bed fusion additive manufacturing

Yuze Huang, Tristan G. Fleming, Samuel J. Clark, Sebastian Marussi, Kamel Fezzaa, Jeyan Thiyagalingam, Chu Lun Alex Leung, Peter D Lee

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106 Citations (Scopus)
70 Downloads (Pure)


Keyhole porosity is a key concern in laser powder-bed fusion (LPBF), potentially impacting component fatigue life. However, some keyhole porosity formation mechanisms, e.g., keyhole fluctuation, collapse and bubble growth and shrinkage, remain unclear. Using synchrotron X-ray imaging we reveal keyhole and bubble behaviour, quantifying their formation dynamics. The findings support the hypotheses that: (i) keyhole porosity can initiate not only in unstable, but also in the transition keyhole regimes created by high laser power-velocity conditions, causing fast radial keyhole fluctuations (2.5–10 kHz); (ii) transition regime collapse tends to occur part way up the rear-wall; and (iii) immediately after keyhole collapse, bubbles undergo rapid growth due to pressure equilibration, then shrink due to metal-vapour condensation. Concurrent with condensation, hydrogen diffusion into the bubble slows the shrinkage and stabilises the bubble size. The keyhole fluctuation and bubble evolution mechanisms revealed here may guide the development of control systems for minimising porosity.
Original languageEnglish
Article number1170
Number of pages11
JournalNature Communications
Publication statusPublished - 4 Mar 2022
Externally publishedYes

Bibliographical note

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ASJC Scopus subject areas

  • Chemistry(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Physics and Astronomy(all)


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