Fluid and particle dynamics in laser powder bed fusion

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

doi:10.1016/j.actamat.2017.09.051

Cited by 429 publications

(229 citation statements)

References 22 publications

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“…Concentrating on the 100 W and 0.4 m/s condition as typical of a good build condition, the results at 1 bar in Fig. 2a were consistent with our previous observations [4,5]. The laser plume points vertically upwards and induces a flow in the shielding gas that entrains particles from all directions on the powder bed.…”

Section: Resultssupporting

confidence: 89%

“…Figure 2d, c, e shows the effect of changing the process setting at 5 bar. The 50 W and 200 W conditions are consistent with our previous observations [4,5] where the laser plume points forwards and backwards respectively with respect to the laser scan direction. In all cases, the denudation at 5 bar was less than the corresponding process setting at 1 bar; however, there was more plasma, and more and larger spatter particles were generated.…”

Section: Argon Atmospheresupporting

confidence: 91%

“…A portable z-type schlieren system [11] used a 300-W tungsten lamp to introduce collimated white light illumination across the powder bed through the two end viewports [4]. Images were recorded with the high-speed camera using a variable focus telephoto lens (focal length 200-500 mm) at 80,000 fps and 384 × 512 pixels resolution.…”

Section: Experimental Systemmentioning

confidence: 99%

“…Recent studies in PBF at atmospheric pressure have shown that the laser plume of metal vapour and plasma from the melt pool induces a flow in the shielding gas, which entrains powder particles towards the track [2][3][4]. The resulting depletion of powder (denudation) increases the likelihood of porosity and the surface roughness of built parts.…”

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: Resultssupporting

confidence: 89%

Section: Argon Atmospheresupporting

confidence: 91%

Section: Experimental Systemmentioning

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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“…Since the pump-probe delay should be scanned to map the temporal dynamics, it is necessary to irradiate multiple pump pulses for generating identical stimulations in the sample. Therefore, the conventional pump-probe methods are not fully compatible with non-repeating phenomena such as fluid dynamics 4 and explosion dynamics 5,6 . The demand has grown steadily for recording the entire sequence of dynamics induced by a single pump pulse 7,8 .…”

Section: Introductionmentioning

confidence: 99%

Single-shot imaging of microscopic dynamic scenes at 5 THz frame rates by time and spatial frequency multiplexing

Moon¹,

Yoon²,

Lim

et al. 2020

Opt. Express

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Femtosecond-scale ultrafast imaging is an essential tool for visualizing ultrafast dynamics in molecular biology, physical chemistry, atomic physics, and fluid dynamics. Pump-probe imaging and a streak camera are the most widely used techniques, but they are either demanding the repetitions of the same scene or sacrificing the number of imaging dimensions. Many interesting single-shot ultrafast imaging techniques have been developed in recent years for recording non-repetitive dynamic scenes. Nevertheless, there are still weaknesses in the number of frames, the number of image pixels, or spatial/temporal resolution. Here, we present a single-shot ultrafast microscopy that can capture more than a dozen frames at a time with the frame rate of 5 THz. We combine a spatial light modulator and a custom-made echelon for efficiently generating a large number of reference pulses with designed time delays and propagation angles. The single-shot recording of the interference image between these reference pulses with a sample pulse allows us to retrieve the stroboscopic images of the dynamic scene at the timing of the reference pulses. We demonstrated the recording of 14 temporal snapshots at a time, which is the largest to date, with the optimal temporal resolution set by the laser output pulse. Our ultrafast microscopy is highly scalable in the number of frames and temporal resolutions, and this will have profound impacts on uncovering the interesting spatio-temporal dynamics yet to be explored.

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Basics of Metal Additive Manufacturing

2021

Metal Additive Manufacturing

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Fluid and particle dynamics in laser powder bed fusion

Cited by 429 publications

References 22 publications

Laser powder bed fusion in high-pressure atmospheres

Laser powder bed fusion in high-pressure atmospheres

Single-shot imaging of microscopic dynamic scenes at 5 THz frame rates by time and spatial frequency multiplexing

Basics of Metal Additive Manufacturing

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