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Melt pool feature analysis using a high-speed coaxial monitoring system for laser powder bed fusion of Ti-6Al-4 V grade 23


In laser powder bed fusion (LPBF), defects such as pores or cracks can seriously affect the final part quality and lifetime. Keyhole porosity, being one type of porosity defects in LPBF, results from excessive energy density which may be due to changes in process parameters (namely, laser power and scan speed) and/or result from the part’s geometry and/or hatching strategies. To study the possible occurrence of keyhole pores, experimental work and simulations were carried out for optimum and high volumetric energy density conditions in Ti-6Al-4 V grade 23. By decreasing the scanning speed from 1000 to 500 mm/s for a fixed laser power of 170 W, keyhole porosities are formed and later observed by X-ray computed tomography. Melt pool images are recorded in real-time during the LPBF process by using a high-speed coaxial Near-Infrared (NIR) camera monitoring system. The recorded images are then pre-processed using a set of image processing steps to generate binary images. From the binary images, geometrical features of the melt pool and features that characterize the spatter particle formation and ejection from the melt pool are calculated. The experimental data clearly show spatter patterns in case of keyhole porosity formation at low scan speed. A correlation between number of pores and amount of spatter is observed. Besides the experimental work, a previously developed high fidelity finite volume numerical model was used to simulate the melt pool dynamics with similar process parameters as used during the experiments. Simulation results illustrate and confirm the keyhole porosity formation by decreasing laser scan speed.

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  1. In [24], the laser spot diameter was assumed to be 50 µm, resulting in slightly smaller reported VED values as compared to the values reported here. Afterwards, the laser spot size was measured to be 37.5 µm leading to the corrected VED values shown in Table 1.


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The authors acknowledge Prof. Shoufeng Yang for initial supervision and discussion of this work.


This research work was funded by research project “PAM2 (Precision Additive Metal Manufacturing)” of the EU Framework Programme for Research and Innovation within Horizon 2020—Marie Skłodowska-Curie Innovative Training Networks under grant agreement No 721383 and by the agency Flanders Innovation & Entrepreneurship (VLAIO) through the Flanders Make project MONICON ICON (HBC.2016.0459).

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Aditi Thanki: Conceptualization, investigation, formal analysis, visualization, validation, writing - original draft. Louca Goossens: Conceptualization, formal analysis, writing - review and editing. Agusmian Partogi Ompusunggu: Conceptualization, supervision, investigation, formal analysis, software, writing - original draft. Mohamad Bayat: Investigation, formal analysis, writing - original draft. Abdellatif Bey-Temsamani: Project management, writing - original draft. Brecht Van Hooreweder: Supervision, resources, writing - review and editing. Jean-Pierre Kruth: Resources, writing - review and editing. Ann Witvrouw: Conceptualization, supervision, funding acquisition, resources, project management, writing - original draft.

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Correspondence to Aditi Thanki.

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Aditi Thanki and Louca Goossens are joint first authors.

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Thanki, A., Goossens, L., Ompusunggu, A.P. et al. Melt pool feature analysis using a high-speed coaxial monitoring system for laser powder bed fusion of Ti-6Al-4 V grade 23. Int J Adv Manuf Technol 120, 6497–6514 (2022).

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  • Laser powder bed fusion (LPBF)
  • Melt pool monitoring
  • Spatter analysis
  • Keyhole porosity
  • Finite volume modelling
  • X-ray computed tomography (X-CT)