60 - Numerical study of vapor generation on LPBF process - effect on process stability

Abstract

Since few years, the metals additive manufacturing become essential in the industrial and research contexts. If the processes start to be quite well mastered in terms of reproducibility and reliability, these laser applications remain strongly studied as well experimentally as numerically. Indeed, it still today to improve understanding of some defects generation or built instabilities (spatters, denudation zone, balling, humping, …). The Laser Powder Bed Fusion (LPBF) process, studied here, is clearly the most complex due to its multiphysic and multiphasic aspects. In this process the beam is thin (<100 µm), the feeding rate is high (>1 m/s) and the whole material phases (powder, liquid, gas and solid) can interact together and with the beam, producing strong instabilities and complex behaviors. Thus, due to these extreme operating parameters, experimental investigations are not trivial. In parallel, numerical tools become more and more efficient and allow currently to manage, with reasonable computation times, these kinds of highly coupled physical problems. In this paper, authors propose a thermo-hydrodynamic simulation of the LPBF process at the mesoscale (scale of the molten pool). Indeed, a major part of defects comes from the close environment of the laser beam and the molten pool. The model includes the gas/vapor atmosphere, the powder and the substrate materials in static and moving laser configurations. A realistic powder bed is set in the model thanks to powder spatial distribution and particle radii coming from another numerical analysis (Discrete Element Method). The metal-gas interface is tracked by the Eulerian Phase-Field method. A particular caution has also been taken in the realistic representation of the vaporization process. After having validated the results, the simulations have been interpreted in order to analyze process potential instabilities.

Speaker

Morgan Dal

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Conference

60 - Numerical study of vapor generation on LPBF process - effect on process stability

Date/Time

20/03/2024

6:20 pm -6:40 pm

Location

Room 8