Formation processes for large ejecta and interactions with melt pool formation in powder bed fusion additive manufacturing

Abdalla R. Nassar, Molly A. Gundermann, Edward W. Reutzel, Paul Guerrier, Michael H. Krane, Matthew J. Weldon

Research output: Contribution to journalArticle

8 Scopus citations

Abstract

Ejecta with a size much larger than the mean particle size of feedstock powder have been observed in powder bed fusion additive manufacturing, both during post-process sieving and embedded within built components. However, their origin has not been adequately explained. Here, we test a hypothesis on the origin of large (much larger than the mass-median-diameter of feedstock powder) ejecta—that, in part, they result from stochastic, inelastic collisions of ejecta and coalescence of partially-sintered agglomerates. The hypothesis is tested using direct observation of ejecta behavior, via high-speed imaging, to identify interactions between ejecta and consequences on melt pool formation. We show that stochastic collisions occur both between particles which are nearly-simultaneously expelled from the laser interaction zone and between particles ejected from distant locations. Ejecta are also shown to perturb melt pool geometry, which is argued to be a potential cause of lack-of-fusion flaws.

Original languageEnglish (US)
Article number5038
JournalScientific reports
Volume9
Issue number1
DOIs
StatePublished - Dec 1 2019

All Science Journal Classification (ASJC) codes

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