In-situ X-ray Observation of Molten Pool Depth

Yamada, Tomonori; Shobu, Takahisa; Nishimura, Akihiko; Yonemoto, Yukihiro; Yamashita, Susumu; Muramatsu, Toshiharu

doi:10.2961/jlmn.2012.03.0002

Cited by 22 publications

(10 citation statements)

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“…Third-generation synchrotron radiation sources provide high flux X-ray beams enabling X-ray imaging with unprecedented temporal (tenths of microseconds) and spatial (a few micrometres) resolution. 33 , 34 This has been exploited to capture the dynamic molten pool behaviour during laser welding 35 , 36 , as well as the formation and evolution of keyhole porosity within stationary laser-induced molten pools. 16 …”

Section: Introductionmentioning

confidence: 99%

In situ X-ray imaging of defect and molten pool dynamics in laser additive manufacturing

et al. 2018

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The laser–matter interaction and solidification phenomena associated with laser additive manufacturing (LAM) remain unclear, slowing its process development and optimisation. Here, through in situ and operando high-speed synchrotron X-ray imaging, we reveal the underlying physical phenomena during the deposition of the first and second layer melt tracks. We show that the laser-induced gas/vapour jet promotes the formation of melt tracks and denuded zones via spattering (at a velocity of 1 m s−1). We also uncover mechanisms of pore migration by Marangoni-driven flow (recirculating at a velocity of 0.4 m s−1), pore dissolution and dispersion by laser re-melting. We develop a mechanism map for predicting the evolution of melt features, changes in melt track morphology from a continuous hemi-cylindrical track to disconnected beads with decreasing linear energy density and improved molten pool wetting with increasing laser power. Our results clarify aspects of the physics behind LAM, which are critical for its development.

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Section: Introductionmentioning

confidence: 99%

In situ X-ray imaging of defect and molten pool dynamics in laser additive manufacturing

et al. 2018

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“…We have succeeded the in-situ observation of a laser induced molten pool with synchrotron radiation [12]. We observed how the droplet was made and grown by this technique.…”

Section: Discussionmentioning

confidence: 94%

Development of laser cladding system with process monitoring by x-ray imaging

2014

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We have been developing a new laser cladding system to repair the damages of parts in aging plants. It consists of some devices which are a laser torch, composite-type optical fiber, QCW fiber laser and etc. All devices are installed in a mobile rack, so we can carry it to plants, laboratories or anywhere we want to use. We should irradiate the work with the best accuracy of laser beam and filler wire in laser cladding. A composite-type optical fiberscope is useful. This fiberscope was composed of a center fiber for beam delivery surrounded by 20000 fibers for visible image delivery. Thus it always keeps target on center of gun-sight. We succeeded to make a line laser cladding on an inside wall of 1-inch tube by our system. Before this success, we solved two serious problems which are the contamination of optics and the deformation of droplet. Observing laser cladding process by X-ray imaging with Spring-8 synchrotron radiation, we found that the molten pool depth was formed to be under a hundred micrometers for 10 milliseconds. A Quasi-CW fiber laser with 1 kW was employed for a heat source to generate the shallow molten pool. The X-ray shadowgraph clarified that a molten droplet was formed at the edge of a wire up to a millimeter size. It grew up if the wire didn't contact with the tube wall in initial state. Here we succeeded to measure the thermo-electromotive force voltage between a wire and a tube metal to confirm whether both came in contact. We propose to apply the laser cladding technology to the maintenance of aging industrial plants and nuclear facilities.

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“…The molten pool formed due to integrated forces of the vapor pressure of liquid metal caused by high power laser beam, the surface tension of molten pool, the blowing force of shielding gas and the fluid gravity in the keyhole [11][12][13], and its morphology varied violently. Yamada et al carried out X-ray imaging of inside materials to observe behavior of molten pool using intense synchrotron radiation during laser welding [14], but the X-ray imaging system were expensive and harmful to operators. Huang concentrated on the CO 2 laser…”

Section: Introductionmentioning

confidence: 99%