LPBF process was one of the most promising additive manufacturing processes of metallic materials over the past decades. It is currently used in a wide range of applications across almost all industrial sectors. However, there is still rooms for improvement, particularly regarding process stability, build rate and metallurgical behavior of manufactured parts.
Recent developments in the field of laser technologies and optical tools, such as diffractive optical element, dual beam fibers or CBC (coherent beam combining) lasers, open new possibilities for beam shaping in lpfb processes.
The present work aims to investigate effect of beam shaping on process stability. Given the potential cost of the power distribution modification, a fully numerical study is proposed, based on prior experimental results.
The simulations are performed with the commercial software COMSOL Multiphysics®. Since, the process stability is strongly influenced by the melt pool behavior, the model must consider as accurately as possible, the most critical physical phenomena. In this study, the process stability is defined by the regularity of the track formation, the molten pool oscillation and the spatter ejections. Consequently, the model accounts for the coupling between heat transfers and fluid flows, in both the solid and liquid phases.
To simulated melt pool behavior in detail, a front tracking method (Phase Field) is employed to simulate liquid surface and gas flow. In this work, particular attention is given to the definition of the vaporization process, which plays a key role for the spatter formation.
After having briefly validated the results of the simulation, we compare thermal and velocity fields for various process parameters (power and feeding rate) and beam shapes (Gaussian, top-hat and donut). Finally, a discussion around key physical values and process stability is done.