Thermo-mechanical simulation of track development in the Laser Beam Melting process - Effect of laser-metal interaction

Abstract

Résumé Interest has recently emerged for the manufacture of aeronautical parts by Laser Beam Melting (LBM) additive process. This energy efficient process can for instance be used to build complex geometries, which cannot be made with traditional processes. However, complex phenomena occur during powder melting and track development : vaporisation phenomena influence laser-matter interaction by creating metal vapours that are responsible for the reduction of absorbed energy. The recoil pressure generated by the vaporisation counteracts the surface tension between the melt pool and the inert gas, also inducing liquid instabilities. The study of laser-matter interaction and induced phenomena can help understand the origin of defects such as porosities or cracks. In this approach, a level-set modelling of the LBM process at a mesoscopic scale is proposed to follow melt pool evolution and track development during build. A volume heat source model is used for laser/powder interaction considering the material absorption coefficient. A surface heat source is used to take into account the high laser energy absorption by dense metal alloys. An energy solver is coupled with thermodynamic database and pre-determined solidification path. Shrinkage during consolidation from powder to liquid and compact medium is modelled by a compressible Newtonian constitutive law. An automatic remeshing adaptation is also used to save time and avoid high computational cost. In the future, the computation of multiple beads or the build of a wall in a context of lattice structures will have to be considered.

Prediction of Epitaxial Grain Growth in Single-Track Laser Melting of IN718 Using Integrated Finite Element and Cellular Automaton Approach

“…In order to determine the forces dominating the melt pool shape formation, the Marangoni number and Bond number were calculated within the melt pool at the point of maximum temperature during the SLM process. Note that the Marangoni number quantifies the effect of the Marangoni force relative to that of the thermal diffusivity and viscous forces and is defined mathematically as [ 25 , 39 , 42 ]: …”

“…The Bond number defines the ratio of the gravitational force to the surface tension force and is calculated as [ 25 ]: where is the melt pool width, and is the gas–melt density difference. The Bond number was found to be just ~0.0023.…”

Multiphysics simulation of single pulse laser powder bed fusion: comparison of front capturing and front tracking methods

“…Finally, it is assumed that the powder bed behaves like a homogeneous absorbing-scattering medium (Gusarov and Smurov, 2010; Rombouts et al , 2005b). The laser incident irradiation penetrates the powder bed thickness by multi-reflection effect in the single vertical direction resulting in a bulk heat source modeled by the Beer–Lambert equation (Queva et al , 2019): where I is the absorbed intensity in the powder depth.…”

“…Then, a second family of models predict melt pool flows and its resulting morphology. Preliminary developments were proposed by Kolossov et al (2004) and Dal et al (2016), but this second approach has been then fully developed and validated by Chen et al (2018, 2019) on ceramic materials, and then transposed and validated on metals by Queva et al (2019, 2020), among others (Grange et al , 2020; Mayi et al , 2019). Even if this approach does not account for the stochastic nature of the powder bed, rapid estimations of scan track dimensions, as well as information on defects as balling, humping or lack of fusion could be established.…”

Microstructure and Elements Concentration of Inconel 713LC during Laser Powder Bed Fusion through a Modified Cellular Automaton Model

“…Equations ( 37) and (38) show that the grain growth speed is a function of the grain orientation. In particular, the grain orientation affects the capturing rate and then drives the grain growth phenomena.…”