Laser powder bed fusion at sub-atmospheric pressures

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Laser powder bed fusion at sub-atmospheric pressures. / Bidare, P.; Bitharas, I.; Ward, R. M.; Attallah, M. M.; Moore, A. J.

In: International Journal of Machine Tools and Manufacture, Vol. 130-131, 01.08.2018, p. 65-72.

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@article{996d66ae259b4707ad3b88ddde110f7a,
title = "Laser powder bed fusion at sub-atmospheric pressures",
abstract = "The perceived advantages of laser powder bed fusion (PBF) at reduced pressure include a more stable melt pool and reduced porosity. In this study, high-speed imaging was used to investigate the interaction of the laser beam with the powder bed at sub-atmospheric pressures. At atmospheric pressure, the laser plume produces a flow in the ambient atmosphere that entrains particles toward the melt pool. As the pressure decreases, this hydrodynamic entrainment increases but eventually the expansion of the laser plume prevents the particles reaching the melt pool: profiles and cross-sections of the track reveal a drastic reduction in its cross-sectional area. As the pressure decreases further, into the molecular flow regime, particles are only repelled by the plume away from the melt pool. The regime between 1 bar and ∼50 mbar (the threshold pressure at which the penetration depth no longer increases) could provide a window for successful processing but might require a pre-sinter to maintain the integrity of the powder bed. Lower pressures would definitely require a pre-sinter, for which the additional processing time and increase in process complexity might be justified for porosity-critical applications.",
keywords = "high-speed imaging , laser powder bed fusion , sub-atmospheric pressure , vacuum",
author = "P. Bidare and I. Bitharas and Ward, {R. M.} and Attallah, {M. M.} and Moore, {A. J.}",
year = "2018",
month = aug,
day = "1",
doi = "10.1016/j.ijmachtools.2018.03.007",
language = "English",
volume = "130-131",
pages = "65--72",
journal = "International Journal of Machine Tools and Manufacture",
issn = "0890-6955",
publisher = "Elsevier",

}

RIS

TY - JOUR

T1 - Laser powder bed fusion at sub-atmospheric pressures

AU - Bidare, P.

AU - Bitharas, I.

AU - Ward, R. M.

AU - Attallah, M. M.

AU - Moore, A. J.

PY - 2018/8/1

Y1 - 2018/8/1

N2 - The perceived advantages of laser powder bed fusion (PBF) at reduced pressure include a more stable melt pool and reduced porosity. In this study, high-speed imaging was used to investigate the interaction of the laser beam with the powder bed at sub-atmospheric pressures. At atmospheric pressure, the laser plume produces a flow in the ambient atmosphere that entrains particles toward the melt pool. As the pressure decreases, this hydrodynamic entrainment increases but eventually the expansion of the laser plume prevents the particles reaching the melt pool: profiles and cross-sections of the track reveal a drastic reduction in its cross-sectional area. As the pressure decreases further, into the molecular flow regime, particles are only repelled by the plume away from the melt pool. The regime between 1 bar and ∼50 mbar (the threshold pressure at which the penetration depth no longer increases) could provide a window for successful processing but might require a pre-sinter to maintain the integrity of the powder bed. Lower pressures would definitely require a pre-sinter, for which the additional processing time and increase in process complexity might be justified for porosity-critical applications.

AB - The perceived advantages of laser powder bed fusion (PBF) at reduced pressure include a more stable melt pool and reduced porosity. In this study, high-speed imaging was used to investigate the interaction of the laser beam with the powder bed at sub-atmospheric pressures. At atmospheric pressure, the laser plume produces a flow in the ambient atmosphere that entrains particles toward the melt pool. As the pressure decreases, this hydrodynamic entrainment increases but eventually the expansion of the laser plume prevents the particles reaching the melt pool: profiles and cross-sections of the track reveal a drastic reduction in its cross-sectional area. As the pressure decreases further, into the molecular flow regime, particles are only repelled by the plume away from the melt pool. The regime between 1 bar and ∼50 mbar (the threshold pressure at which the penetration depth no longer increases) could provide a window for successful processing but might require a pre-sinter to maintain the integrity of the powder bed. Lower pressures would definitely require a pre-sinter, for which the additional processing time and increase in process complexity might be justified for porosity-critical applications.

KW - high-speed imaging

KW - laser powder bed fusion

KW - sub-atmospheric pressure

KW - vacuum

U2 - 10.1016/j.ijmachtools.2018.03.007

DO - 10.1016/j.ijmachtools.2018.03.007

M3 - Article

VL - 130-131

SP - 65

EP - 72

JO - International Journal of Machine Tools and Manufacture

JF - International Journal of Machine Tools and Manufacture

SN - 0890-6955

ER -