Laser powder bed fusion at sub-atmospheric pressures

Bidare, Prveen; Bitharas, Ioannis; Ward, Robin; Attallah, Moataz M.; Moore, Andrew J.

doi:10.1016/j.ijmachtools.2018.03.007

Cited by 56 publications

(47 citation statements)

References 13 publications

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“…1. The pressure chamber was essentially the same as a vacuum chamber used to perform PBF at sub-atmospheric pressures down to 10 μbar [5] and so it is not described in detail again here. The key difference was that the high-vacuum viewport assemblies, which were used to provide optical access to the powder bed, were reinforced externally with stainless steel adapter plates and additional O-rings to prevent them from blowing out under high pressure.…”

Section: Experimental Systemmentioning

confidence: 99%

“…High-speed image sequences were recorded with a Phantom V2512 monochrome camera at 40,000 frames per second (fps) and 768 × 368 pixels resolution, with illumination of the powder bed by a Lumencor SOLA SM white light source [5]. The camera was fitted with a band-stop filter to block light from the PBF laser.…”

Section: Experimental Systemmentioning

confidence: 99%

“…The resulting depletion of powder (denudation) increases the likelihood of porosity and the surface roughness of built parts. If the ambient pressure is reduced, the speed of the laser plume increases [2,5]. In the hydrodynamic flow regime, the associated increase in the induced flow entrains more powder particles, and particles from further away on the powder bed, towards the laser scan line, increasing the width of the denuded zone.…”

Section: Introductionmentioning

confidence: 99%

“…However, these particles do not reach the melt pool due to the increased speed and wider ejection angle of the laser plume: profiles and cross-sections of the track reveal a drastic reduction in its cross-sectional area. Eventually, at pressures low enough to reach the molecular flow regime, there is no entrainment of particles towards the laser scan line and all particles are repelled from the melt pool by the expansion of the laser plume [2,5].…”

Section: Introductionmentioning

confidence: 99%

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Laser powder bed fusion in high-pressure atmospheres

Bidare

Bitharas

Ward

et al. 2018

Int J Adv Manuf Technol

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High-speed imaging and schlieren imaging were used to investigate the interaction of the laser beam with the powder bed at pressures up to 5 bar, in argon and helium atmospheres. The entrainment of powder particles in the flow of shielding gas generated by the laser plume, and hence denudation, was reduced at high pressure for both gases. However, for argon, high pressure increased the temperature of both the melt pool and the laser plume, which significantly increased the generation of spatter and ionisation of the metal vapour with degraded surface smoothness and continuity. For helium, the formation of spatter and plasma did not increase with the increase in pressure above that observed at atmospheric pressure: its higher thermal conductivity and thermal diffusivity limited the laser plume temperature. Layers built at 5 bar in helium had a surface smoothness and continuity comparable to those built in argon at atmospheric pressure, but achieved at a higher laser scan speed, suggesting that a high-pressure helium atmosphere may be used to enhance the build rate.

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Section: Experimental Systemmentioning

confidence: 99%

Section: Experimental Systemmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Laser powder bed fusion in high-pressure atmospheres

Bidare

Bitharas

Ward

et al. 2018

Int J Adv Manuf Technol

Self Cite

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“…For instance, the "hatch angle" has an impact on the strength properties of stainless steel 304 [7]. Laser density energy [12,13] and chamber pressure [14] influence the porosity of the printing parts. Additionally, there are works which present controversial results for austenitic steel.…”

Section: Introductionmentioning

confidence: 99%

Structure control of 316L stainless steel through an additive manufacturing

et al. 2019

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The 3D printing process is a recent technique, which allows one to produce parts of complex geometry. The influence of printing parameters on the mechanical and structural properties of many materials has been extensively studied. However, despite the considerable amount of research, the task of comparing the results of different scientific groups is complicated. Each research group performs the investigation with different printing conditions. A lot of works contain not full information about the printing process parameters which were applied. This paper presents the results on the mechanical and structural properties of 316L stainless steel according to variable printing parameters, such as laser density energy, scan strategy, and build direction at other fixed conditions. The results reveal a parabolic dependency between the mechanical properties and the laser density energy. The laser density energy of 161 J/mm 3 leads to the best mechanical characteristics (yield strength of 530 MPa, ultimate strength of 580 MPa, and ductility of 63.2%). Scan strategy does not influence the mechanical properties of the samples printed in the vertical direction. At the same time, the strong scan strategy effect is observed for the samples printed in horizontal direction. The difference in the ultimate strength between the vertically and horizontally printed samples reaches up to 70 MPa.

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Numerical Simulation of Additive Manufacturing Processes

Carin

2022

Additive Manufacturing of Metal Alloys 1

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Laser powder bed fusion at sub-atmospheric pressures

Cited by 56 publications

References 13 publications

Laser powder bed fusion in high-pressure atmospheres

Laser powder bed fusion in high-pressure atmospheres

Structure control of 316L stainless steel through an additive manufacturing

Numerical Simulation of Additive Manufacturing Processes

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