Modeling Particle Spray and Capture Efficiency for Direct Laser Deposition Using a Four Nozzle Powder Injection System

Abstract

Powder capture efficiency is indicative of the amount of material that is added to the substrate during laser additive manufacturing (AM) processes, and thus, being able to predict capture efficiency provides capability of predictive modeling during such processes. The focus of the work presented in this paper is to create a numerical model to understand particle trajectories and velocities, which in turn allows for the prediction of capture efficiency. To validate the numerical model, particle tracking velocimetry (PTV) experiments at two powder flow rates were conducted on free stream particle spray to track individual particles such that particle concentration and velocity fields could be obtained. Results from the free stream comparison showed good agreement to the trends observed in experimental data and were subsequently used in a direct laser deposition (DLD) simulation to assess capture efficiency and temperature profile at steady-state. The simulation was validated against a single track deposition experiment and showed proper correlation of the free surface geometry, molten pool boundary, heat affected zone boundary, and capture efficiency.

Investigation of molten pool geometry and flow field based on powder scale modeling in laser directed energy deposition

“…As EUMs increases and the temperature of the powder particles in the melt pool rises, the heat input increases the temperature gradient of the melt pool, which causes an increase in the surface tension gradient, resulting in a faster flow velocity of the liquid, as shown in Eq. (18). The position of the solidus temperature continues to migrate downward as EUM increases, and the heat affected zone expands, resulting in increasing melt depth dimensions of 0.510 mm, 0.520 mm, and 0.537 mm, respectively.…”

“…The second type of LDED numerical model considers powder delivery and is recognized as a powder-scale model [18][19][20]. In this model, the powder handling approach can be categorized into two types based on the level of computational accuracy.…”

Multiphysics multi-scale computational framework for linking process–structure–property relationships in metal additive manufacturing: a critical review

“…To this end, the Discrete Phase Modeling (DPM) framework is employed. The powder particles are assigned a Lagarngian description in DPM whereas the gas phase is considered a continuum [120]. To resolve the turbulent nature of the gas flow, a Reynolds averaged Navier-Stokes (RANS) formulation is utilised.…”

Laser additive manufacturing of steels

“…As a result, larger melt pools are created. This also indicates a higher capture efficiency, which is an important benchmark criterion to evaluate the efficiency of a laser process and is defined as the ratio of the powder trapped in the melt pool to the powder delivered [101,102].…”

“…In addition, laser power is also closely related to the balling phenomenon, which is a defect resulting from the inhomogeneous regrouping of powder particles and has been well-studied in laser cladding and welding [102][103][104]. Since LAM is a layer-wise manufacturing process, the balling phenomenon is a severe impediment to the uniform layer deposition and leads to the formation of inter-layer pores and even delamination under thermal stress [105].…”