Physics of humping formation in laser powder bed fusion

•Implementation of ray tracing heat source in the CFD model•Good consistency between simulations and experiments•Humping defects in samples fabricated at high laser power and scanning speed•Discussion on the roles of various force on humping formation Despite of the promising attributes of laser pow...

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Bibliographic Details
Published in:International journal of heat and mass transfer Vol. 149; p. 119172
Main Authors: Tang, C., Le, K.Q., Wong, C.H.
Format: Journal Article
Language:English
Published: Oxford Elsevier Ltd 01.03.2020
Elsevier BV
Subjects:
Additive manufacturing
Austenitic stainless steels
Capillary flow
Computational fluid dynamics
Computer simulation
Contact angle
Flow stability
Flux density
Humping
Industrial applications
Laser powder bed fusion
Lasers
Porosity
Powder beds
Rapid prototyping
Ray tracing algorithm
Recoil
Scanning
Shear forces
Surface defects
Surface morphology
Surface roughness
Surface stability
Surface tension
Swelling
Laser powder bed fusion
Ray tracing algorithm
Additive manufacturing
Computational fluid dynamics
Surface morphology
Humping
ISSN:0017-9310, 1879-2189
Online Access:Get full text
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Summary:•Implementation of ray tracing heat source in the CFD model•Good consistency between simulations and experiments•Humping defects in samples fabricated at high laser power and scanning speed•Discussion on the roles of various force on humping formation Despite of the promising attributes of laser powder bed fusion, part quality such as porosity and surface roughness remains a critical issue for industrial applications. Humping is a surface defect that may greatly deteriorate the mechanical performances of as-built components. However, current understanding of humping formation remains vague and unclear. In this respect, laser powder bed fusion of stainless steel 316 L single tracks was simulated by using computational fluid dynamics. With the same linear energy density, the simulated tracks exhibit irregular humps at high scanning velocities, which is validated against experiments. In addition, flow kinetics was analyzed to elucidate the physical origins of humping formation during printing process. The study reveals the various effects of surface tension, Marangoni shear force, viscous force and recoil pressure on the humping phenomenon in laser powder bed fusion. At relatively high scanning speed, a swelling with large contact angle is formed due to the competition between surface tension and flow inertia. Capillary instability divides the swelling into separated regions, which is responsible for the humping formation during printing process.
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ISSN:0017-9310
1879-2189
DOI:10.1016/j.ijheatmasstransfer.2019.119172