Multiphysics simulation of laser–material interaction during laser powder depositon

Abstract

This work reports a theoretical and numerical study of the parameters related to the process of laser powder deposition through a lateral nozzle. For this purpose, a 3D quasi-stationary finite element model was developed analytically and implemented numerically. The proposed model estimates the shape of the melt pool depending on the process parameters including scanning speed, powder mass flow, laser power, and physical properties. Also, phase transformations and physical properties (density, thermal conductivity, and specific heat) vary as function of temperature. In addition, thermo-capillary forces and their effect on fluid flow inside the melt pool are considered. The obtained set of equations coupled through the temperature variable was solved using COMSOL Multiphysics. The results are presented and compared with previously obtained experimental data, in which chromium powder was deposited, allowing validation of the model. Finally, variations at the melt pool geometry in terms of the operational parameters are analyzed. This model aims at estimation of melt pool geometry during laser powder deposition in time reasonably short to allow for predictable process control.

An overview of Direct Laser Deposition for additive manufacturing; Part I: Transport phenomena, modeling and diagnostics

“…Laser-induced plasma can become a source for non-linear pressure effects; especially at higher power levels [111]. This positive pressure can help in regulating the amount of vapor escaping the melt pool and also increases with power level [112].…”

“…Heat loss due to vaporization of the melt pool can also occur and be somewhat detrimental to DLD. However, as the laser power increases, the effects of vapor output from the melt pool actually decreases due to increased plasma pressure above the melt pool region [112].…”

“…Many 'traditional' DLD methods utilize only one nozzle for powder delivery in which the nozzle is aligned coaxially with the laser. Angled (45º) single-nozzle injection has been investigated, as well [112]. Relative to multi-nozzle DLD systems, such as LENS, it is more difficult to ensure flow uniformity or to direct the material to only specific regions of interest -which is desired for functionally-grading.…”

“…Like PBF-L, the finished part(s) must be sheared off from the substrate after the AM process. DLD can be utilized for additive manufacture of a variety of metals and even ceramics -including: Inconel 625, stainless steels, H13 tool steel, titanium alloy, chromium, tungsten and more [35,[39][40][41][42][43][44][45]. Direct Laser Deposition has also been utilized to successfully manufacture cerments composed of tungsten carbide-cobalt [46].…”

Analytical and Numerical Temperature Prediction in Direct Metal Deposition of Ti6Al4V

“…Other than predicting the temperature and the thermal stresses, the FE-based approach serves also to predict the melt pool geometry as proposed by Peyre et al [15] using a 3D FE model. Several other researchers in [19][20][21] have proposed a complete multi-physics models to predict both the thermo-mechanical processing experienced by the material as well as the complex laser-materials interaction leading to fluid flow in the melt pool, surface tension and thermocapillary forces. Morville et al [22] and Morville [23] presented simulations of a single layer and multilayer cladding with fluid flow and heat transfer to demonstrate the capabilities of FEM method to give a good comprehension of the phenomena responsible for a deleterious surface finish.…”