Melting behavior in laser powder bed fusion revealed by in situ X-ray and thermal imaging

Wakai, Yuki; Ogura, Tomoya; Nakano, Shizuka; Sato, Naoko; Kajino, Satoshi; Suzuki, Shinsuke

doi:10.1007/s00170-020-05828-3

Cited by 12 publications

(6 citation statements)

References 35 publications

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“…The above fact was confirmed from thermal images later. These had already confirmed in our previous paper that used the same experimental equipment [20].…”

Section: Analysis Results Of X-ray Imagessupporting

confidence: 81%

“…Figure 1 shows a schematic of LPBF experiments conducted in this study using in-situ X-ray and thermal imaging. The following parameters were different from those in our previous paper [20]: powder metal, the material of the container, its transferring method, laser irradiation condition, the Xray tube voltage and current. Spherical pure Ti powder of average particle size under 45 µm (TILOP-45: OSAKA Titanium Technologies Co., Ltd.) which was produced by gas atomization method was used.…”

Section: Experimental Setup and Materialsmentioning

confidence: 77%

“…Based on these, it is expected that the melting behavior in single-track examination can be clarified in detail by combining in-situ simultaneous observation of melting powder by X-ray imaging and temperature distribution measurement by thermal imaging. Then, our group established an analytical method using X-ray and thermal imaging simultaneously for the first time [20]. Wakai et al classified the variations of the melting behavior with time at one-point irradiation using X-ray and thermal imaging.…”

Section: Introductionmentioning

confidence: 99%

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Transition mechanism of melt depth during Laser Powder Bed Fusion using in-situ X-ray and thermal imaging

Ogura¹,

Wakai²,

Nakano³

et al. 2021

Preprint

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This research clarified the transition mechanism of melt depth in Ti powder bed during Laser Powder Bed Fusion process using in-situ X-ray and thermal imaging. A fiber laser beam of 150 W was irradiated on a powder bed at a scan speed of 15 mm/s for 3.5 s in a vacuum chamber. The obtained X-ray images showed a keyhole depth Ld increased immediately after laser irradiation, gradually decreased, and became constant. It also showed a keyhole width Lw increased immediately after laser irradiation and decreased afterward, after that, Lw increased again, and became constant. Furthermore, thermal images that measured the temperature on the powder bed showed the high temperature width Lh gradually increased and become constant. The model of the driving force which pushed the molten droplet was examined by analyzing the volume and scattering speed of the molten droplet. The model indicated the recoil pressure caused by the vaporization of powder metal was a driving force for the molten droplet scattering. The transition mechanism of keyhole depth was considered as follows. The increase of Ld at the beginning is due to the increase of the recoil pressure PT. This is because the decrease of Lw and large quantity of vaporization. Next, the decrease of Ld is due to the decrease in PT. This is because the increase of Lw and decrease of quantity of vaporization. At last, the transition to the constant Ld is caused by stabilization of Lw and Lh followed by stabilization of PT.

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“…The above fact was confirmed from thermal images later. These had already confirmed in our previous paper that used the same experimental equipment [20].…”

Section: Analysis Results Of X-ray Imagessupporting

confidence: 81%

Section: Experimental Setup and Materialsmentioning

confidence: 77%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Transition mechanism of melt depth during Laser Powder Bed Fusion using in-situ X-ray and thermal imaging

Ogura¹,

Wakai²,

Nakano³

et al. 2021

Preprint

Self Cite

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“…Nevertheless, it is possible to measure the temperature distribution on the surface of the molten pool using remote temperature measurement methods, such as high-speed infrared cameras (95) or two-color pyrometry methods (96)(97)(98) . However, it is not currently possible to measure the time variation in the G and R, which determines the solidification microstructure.…”

Section: Solidification and Crystalline Growthmentioning

confidence: 99%

Digital Twin Science of Metal Powder Bed Fusion Additive Manufacturing: A Selective Review of Simulations for Integrated Computational Materials Engineering and Science

Okugawa

2022

ISIJ Int.

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A digital twin (DT) is a cyberspace replica of a system, such as manufacturing equipment. A DT consists of statistical models and computer simulations of physical phenomena occurring in the system. The modeling is adjusted to the system based on signals from sensors attached to the system and their temporal changes. In general, a DT is utilized to (i) predict phenomena occurring in the system, (ii) optimize control parameters, and (iii) estimate part replacement schedules. We propose to use a DT to elucidate the unique solidification phenomena occurring in a type of metal 3D printing (i.e., additive manufacturing: AM) process. Thus, we propose that applications of DT that obtain scientific data be referred to as "digital twin science (DTS)." This paper first reviews the fundamental of the AM process, particularly powder bed fusion (PBF) and relevant computer simulations, and then studies on computer simulations conducted to elucidate the relationship between the extreme conditions characteristic of the PBF process and solidification microstructures. The findings achieved by the DTS approach indicate that the combination of experimental and simulation data aid the future development of techniques to obtain required microstructures exhibiting desired properties.

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“…Wakai et al 58 combined the in-situ X-ray imaging with a pyrometer to monitor the melt pool of Ti–6Al–4V in L-PBF. However, their device's spatial and temporal resolutions (X-ray: 45 μm/pix with 500 Hz framerate, pyrometer: 13.3 μm/pix with 50 Hz framerate) were not high enough to observe rapid thermal and geometry changes.…”

Section: Introductionmentioning

confidence: 99%

In situ melt pool measurements for laser powder bed fusion using multi sensing and correlation analysis

Wang

García

Kamath

et al. 2022

Sci Rep

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Laser powder bed fusion is a promising technology for local deposition and microstructure control, but it suffers from defects such as delamination and porosity due to the lack of understanding of melt pool dynamics. To study the fundamental behavior of the melt pool, both geometric and thermal sensing with high spatial and temporal resolutions are necessary. This work applies and integrates three advanced sensing technologies: synchrotron X-ray imaging, high-speed IR camera, and high-spatial-resolution IR camera to characterize the evolution of the melt pool shape, keyhole, vapor plume, and thermal evolution in Ti–6Al–4V and 410 stainless steel spot melt cases. Aside from presenting the sensing capability, this paper develops an effective algorithm for high-speed X-ray imaging data to identify melt pool geometries accurately. Preprocessing methods are also implemented for the IR data to estimate the emissivity value and extrapolate the saturated pixels. Quantifications on boundary velocities, melt pool dimensions, thermal gradients, and cooling rates are performed, enabling future comprehensive melt pool dynamics and microstructure analysis. The study discovers a strong correlation between the thermal and X-ray data, demonstrating the feasibility of using relatively cheap IR cameras to predict features that currently can only be captured using costly synchrotron X-ray imaging. Such correlation can be used for future thermal-based melt pool control and model validation.

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Melting behavior in laser powder bed fusion revealed by in situ X-ray and thermal imaging

Cited by 12 publications

References 35 publications

Transition mechanism of melt depth during Laser Powder Bed Fusion using in-situ X-ray and thermal imaging

Transition mechanism of melt depth during Laser Powder Bed Fusion using in-situ X-ray and thermal imaging

Digital Twin Science of Metal Powder Bed Fusion Additive Manufacturing: A Selective Review of Simulations for Integrated Computational Materials Engineering and Science

In situ melt pool measurements for laser powder bed fusion using multi sensing and correlation analysis

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