Influence of Pulsed Exposure Strategies on Overhang Structures in Powder Bed Fusion of Ti6Al4V Using Laser Beam

Manufacturing structures with low overhang angles without support structures is a major challenge in powder bed fusion of metals using laser beam (PBF-LB/M). In the present work, various test specimens and parameter sets with continuous wave (cw) and pulsed exposure are used to investigate whether a...

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Bibliographic Details
Published in:Metals (Basel ) 2021-07, Vol.11 (7), p.1125
Main Authors: Grünewald, Jonas, Clarkson, Pirmin, Salveson, Ryan, Fey, Georg, Wudy, Katrin
Format: Article
Language:English
Subjects:
additive manufacturing
Art exhibits
Continuous radiation
Energy
Exposure
Flux density
Investigations
Laser beams
Lasers
Mechanical properties
Parameters
Particle size
PBF-LB/M
powder bed fusion of metals using laser beam
Powder beds
power modulation
Pulse duration
Raw materials
Redevelopment
Stainless steel
Surface roughness
Ti64
Ti6Al4V
Titanium alloys
Titanium base alloys
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Summary:Manufacturing structures with low overhang angles without support structures is a major challenge in powder bed fusion of metals using laser beam (PBF-LB/M). In the present work, various test specimens and parameter sets with continuous wave (cw) and pulsed exposure are used to investigate whether a reduction of downskin roughness and overhang angle can be achieved in PBF-LB/M of Ti6Al4V. Starting from cw exposure, the limits of overhang angle and surface roughness at the downskin surface are investigated as a reference. Subsequently, the influence of laser power, scanning speed, and hatch distance with fixed pulse duration (τpulse = 25 µs) and repetition rate (υrep = 20 kHz) on surface roughness Ra is investigated. Pulsed exposure strategies enable the manufacturing of flatter overhang angles (≤20° instead of ≥25°). Furthermore, a correlation between the introduced volume energy density and the downskin roughness can be observed for pulsed exposure. As the reduction in volume energy density causes an increase in porosity, the combination of pulsed downskin exposure and commercial cw infill exposure is investigated. The larger the gap in volume energy density between the infill area and downskin area, the more challenging it is combining the two parameter sets. By combining cw infill and pulsed downskin exposure, flatter overhang structures cannot be manufactured, and a reduction in roughness can be achieved.
ISSN:2075-4701
2075-4701
DOI:10.3390/met11071125