Modeling of transport phenomena during the coaxial laser direct deposition process

Abstract

Laser direct deposition is widely used for rapid freeform fabrication of fully dense components with good metallurgical properties directly from computer-aided design drawings. Because of complex physics involved such as laser powder interaction, laser substrate interaction, track interface evolution, and melt-solid interaction, it is important to develop simulation models to better understand the characteristics and mechanisms in the process so that optimization and control of a laser direct deposition process are possible. In this paper, a new comprehensive three-dimensional self-consistent transient model is presented for a coaxial laser direct deposition process, which considers physical behaviors such as laser particle interaction, mass addition, heat transfer, fluid flow, melting, and solidification. A continuum model is built to deal with different phases (gas, liquid, solid, and mushy zone) in the calculation domain. An improved level-set method, which takes the conservative form while being implicitly solved with other governing equations, is proposed to track the evolution of free liquid/gas interface during the deposition process. To make the model more physically complete than those in the literature, a newly derived mass source term, which considers the rate of the gas phase being replaced by the deposited material due to the moving interface in some control volumes, is incorporated into the continuity equation. Corresponding new source terms of enthalpy and momentum due to the moving interface are also derived and embedded in the energy and momentum equations. The governing equations are discretized using the finite volume approach to better predict the fluid motion mainly driven by capillary and thermocapillary forces. The simulated track heights, widths, molten pool depths, and track profiles agree well with the experimental results.

Multiscale Modeling of Transport Phenomena and Dendritic Growth in Laser Cladding Processes

“…The element activation method has been used in finite-element models, [1,2,5] whereas the volume-of-fluid method [7] and the level-set method [6,[8][9][10][11][12] have been used in finite-volume and/or finite-difference models in which the thermofluid flow has been considered. An improved level-set method was proposed by Wen and Shin [11,12] to capture the evolution of the free surface of clad tracks. Additional source terms have been incorporated into the governing equation set to consider more rigorously the effects of continual additions of mass and energy from the deposited powder.…”

“…Some models have been developed based on a heat conduction equation with the consideration of latent heat of phase transformation, [1][2][3][4][5] whereas other models have included a convection term in the formulation to have a more complete consideration of the underlying physics. [6][7][8][9][10][11][12] The most challenging issue in the modeling of cladding processes is to track the freesurface evolution caused by material deposition. Some models are based on a simplified formulation with a predefined geometry of clad track, [13,14] which can give only qualitative results.…”

Numerical simulation of thermal behavior and multicomponent mass transfer in direct laser deposition of Co-base alloy on steel

“…It has some benefits compared with the traditional surface modification and manufacture technique, such as its small heat affected zone, low thermal strain, low porosity, and finer grain size [1,2]. In direct laser deposition, the substrate is melted by a high power density laser beam creating a melt pool in which the multicomponent alloy powders are injected [3]. Cobase and Ni-base alloy have been widely used as the added material to improve the surface properties of substrate, such as strength, wear resistance and corrosion resistance [4][5][6].…”

Advances in the modeling of laser direct metal deposition

“…Different from these are the continuum models of Wen and Shin 67 and Ibarra-medina et al, 74 which contain no analytical component. Wen and Shin modeled the LENS process, incorporating Marangoni and Capillary effects, and used a level-set method for melt pool surface tracking (akin to Han et al…”

“…Gas flow in the powder stream was taken as turbulent, described by the k-e model as reported in another paper dedicated to this subject. 67 The model was also applied to two overlapping tracks, 68 off-axis deposition 69 and cladding with an additional hard particle phase. 70 The model of Ibarra-medina et al incorporated the same effects but considered an annular nozzle and used the volume of fluid (VOF) method (Fig.…”