An open-architecture metal powder bed fusion system for in-situ process measurements

Bidare, Prveen; Maier, Robert R. J.; Beck, Rainer J.; Shephard, Jonathan D.; Moore, Andrew J.

doi:10.1016/j.addma.2017.06.007

Cited by 63 publications

(49 citation statements)

References 14 publications

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“…Results were recorded for three different laser power and scan speed combinations that provided the same line energy (laser power divided by scan speed) of 250 J/m: 50 W and 0.2 m/s, 100 W and 0.4 m/s and 200 W and 0.8 m/s. The 100-W laser power condition has been shown to build parts with > 99% density in our system [9] at atmospheric pressure (1 bar). Single tracks and rectangular islands were scanned at absolute pressures of 1, 3 and 5 bar.…”

Section: Resultsmentioning

confidence: 83%

“…We previously reported the design and characterisation of an open-architecture PBF system for in situ measurements [9]. The PBF system is computer controlled for the automated build of fully dense components, enabling in-process measurements under realistic build conditions.…”

Section: Experimental Systemmentioning

confidence: 99%

“…The powder Fig. 1 Schematic of the openarchitecture PBF system with pressure chamber was melted with a single-mode fibre laser (1070 nm) focussed to a spot of diameter 50 μm [9].…”

Section: Experimental Systemmentioning

confidence: 99%

“…4. The incident laser beam traverses more of the thermal plume of heated gas and metal vapour produced by the melt pool at 200 W than at 100 W; the thermal plume rises faster in helium steady state build after 6 to 10 layers the denudation is less severe due to the increased powder layer thickness [9] and the surface roughness of previously built layers [4].…”

Section: Argon Atmospherementioning

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: Resultsmentioning

confidence: 83%

Section: Experimental Systemmentioning

confidence: 99%

“…The powder Fig. 1 Schematic of the openarchitecture PBF system with pressure chamber was melted with a single-mode fibre laser (1070 nm) focussed to a spot of diameter 50 μm [9].…”

Section: Experimental Systemmentioning

confidence: 99%

Section: Argon Atmospherementioning

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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“…Several in situ process monitoring techniques have been developed to examine the build process for improving process parameters and inform models. Visible‐light high‐speed imaging provides insight into many important phenomena including spatter, powder motion and denudation, and melt pool dynamics . Thermal imaging has also played a significant role in understanding how material thermal properties and build strategies affect the final build .…”

Section: Introductionmentioning

confidence: 99%

Laser‐Induced Keyhole Defect Dynamics during Metal Additive Manufacturing

et al. 2019

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Laser powder bed fusion (LPBF) metal additive manufacturing provides distinct advantages for aerospace and biomedical applications. However, widespread industrial adoption is limited by a lack of confidence in part properties driven by an incomplete understanding of how unique process parameters relate to defect formation and ultimately mechanical properties. To address that gap, high‐speed X‐ray imaging is used to probe subsurface melt pool dynamics and void‐formation mechanisms inaccessible to other monitoring approaches. This technique directly observes the depth and dynamic behavior of the vapor depression, also known as the keyhole depression, which is formed by recoil pressure from laser‐driven metal vaporization. Also, vapor bubble formation and motion due to melt pool currents is observed, including instances of bubbles splitting before solidification into clusters of smaller voids while the material rapidly cools. Other phenomena include bubbles being formed from and then recaptured by the vapor depression, leaving no voids in the final part. Such events complicate attempts to identify defect formation using surface‐sensitive process‐monitoring tools. Finally, once the void defects form, they cannot be repaired by simple laser scans, without introducing new defects, thus emphasizing the importance of understanding processing parameters to develop robust defect‐mitigation strategies based on experimentally validated models.

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