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Title: Denudation of metal powder layers in laser powder bed fusion processes

Understanding laser interaction with metal powder beds is critical in predicting optimum processing regimes in laser powder bed fusion additive manufacturing of metals. In this work, we study the denudation of metal powders that is observed near the laser scan path as a function of laser parameters and ambient gas pressure. We show that the observed depletion of metal powder particles in the zone immediately surrounding the solidified track is due to a competition between outward metal vapor flux directed away from the laser spot and entrainment of powder particles in a shear flow of gas driven by a metal vapor jet at the melt track. Between atmospheric pressure and ~10 Torr of Ar gas, the denuded zone width increases with decreasing ambient gas pressure and is dominated by entrainment from inward gas flow. The denuded zone then decreases from 10 to 2.2 Torr reaching a minimum before increasing again from 2.2 to 0.5 Torr where metal vapor flux and expansion from the melt pool dominates. In addition, the dynamics of the denudation process were captured using high-speed imaging, revealing that the particle movement is a complex interplay among melt pool geometry, metal vapor flow, and ambient gas pressure. Themore » experimental results are rationalized through finite element simulations of the melt track formation and resulting vapor flow patterns. The results presented here represent new insights to denudation and melt track formation that can be important for the prediction and minimization of void defects and surface roughness in additively manufactured metal components.« less
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  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
Report Number(s):
Journal ID: ISSN 1359-6454
Grant/Contract Number:
AC52-07NA27344; 15-ERD-037
Published Article
Journal Name:
Acta Materialia
Additional Journal Information:
Journal Volume: 114; Journal ID: ISSN 1359-6454
Research Org:
Lawrence Livermore National Lab., Livermore, CA (United States)
Sponsoring Org:
Country of Publication:
United States
36 MATERIALS SCIENCE; 42 ENGINEERING; selective laser melting; powder bed fusion; surface structure; defects; fluid dynamics; finite element modeling; high speed imaging
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1281668