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Numerical and experimental investigations of powder stream behaviors in high-speed laser cladding (HSLC).
Laser cladding (LC) and high-speed laser cladding (HSLC) are direct metal deposition (DMD) techniques where metal powder is delivered to a substrate using a carrier gas, and a laser melts the powder and substrate to create a coating. The primary difference between LC and HSLC lies in the powder-laser interaction, as shown in Figure 1. In LC, the powder is injected into a molten pool on the substrate, while in HSLC, the powder is melted in flight before reaching the substrate. This distinction allows HSLC to achieve deposition speeds up to two orders of magnitude higher than LC while reducing the heat input to the substrate. Achieving these benefits, however, depends on the efficient and predictable interaction between the powder and the laser beam.
This project investigates the behavior of powder streams in HSLC using a dual approach: advanced numerical simulations and experimental validations. It explores the influence of key input parameters, such as gas flow settings, nozzle geometry, and material properties, on powder stream dynamics. By combining numerical modeling and experimental analysis, the study aims to uncover new insights into powder stream behaviors, optimize the process, and refine the robustness of the model under diverse conditions.
Keywords: Additive manufacturing, 3D printing, Multi-physics, Numerical modeling
LC and HSLC are widely used to modify and improve the surface properties of metallic substrates while keeping the structural properties of the substrate. During both processes, the laser provides the energy to melt both the powder and the substrate, creating a melt pool. In conventional LC, the powder is directly melted within the melt pool, whereas in HSLC, most of the energy is absorbed by the powder in flight, allowing for a smaller melt pool and faster deposition rates. [1–3].
Since the laser beam shape can be assumed constant, the interaction between the laser and powder can be controlled by adjusting the powder stream characteristics. While many studies have focused on modeling powder stream characteristics for conventional DMD, fewer have explored high-speed DMD applications. Schopphoven et al. [4] developed a statistical model to map 3D powder density in HSLC, which was validated using laser-light sectioning to analyze powder particle trajectories. From these trajectories, the model described both the particle density and the normalized probability density. However, it did not investigate interactions between the carrier gas, shield gas, and mass flow rate.
On the other hand, Zhang et al. [5] developed a numerical model to predict powder stream characteristics in HSLC, considering the influence of shield gas, carrier gas, and mass flow rate. Although their model was validated by comparing simulated powder density distributions to high-speed camera images, it has several limitations, such as restricted validation conditions, lack of particle velocity analysis, and omission of particle-to-particle interactions, which become critical at high mass flow rates.
In this project, a state-of-the-art Computational Fluid Dynamics–Discrete Element Method (CFD-DEM) model developed at AMLZ (Figure 2) and described by Deifilia To [6] (former master's student) will be adapted to simulate powder stream behavior in HSLC. The model incorporates compressibility, particle-wall and particle-particle collisions, turbulence, and gas mixing. Validation will be conducted by characterizing the powder stream of a custom dual-system HSLC machine at Inspire AG, utilizing high-speed camera imaging and processing and a cutting-edge powder caustic scanner (Figure 3). The effects of shield gas, carrier gas, and mass flow rate will be explored, and the model’s robustness will be tested with different materials and nozzle types.
If the final results are promising, they can potentially be turned into publications. Seeing our recently published paper [6] derived from Deifilia’s master thesis.
LC and HSLC are widely used to modify and improve the surface properties of metallic substrates while keeping the structural properties of the substrate. During both processes, the laser provides the energy to melt both the powder and the substrate, creating a melt pool. In conventional LC, the powder is directly melted within the melt pool, whereas in HSLC, most of the energy is absorbed by the powder in flight, allowing for a smaller melt pool and faster deposition rates. [1–3]. Since the laser beam shape can be assumed constant, the interaction between the laser and powder can be controlled by adjusting the powder stream characteristics. While many studies have focused on modeling powder stream characteristics for conventional DMD, fewer have explored high-speed DMD applications. Schopphoven et al. [4] developed a statistical model to map 3D powder density in HSLC, which was validated using laser-light sectioning to analyze powder particle trajectories. From these trajectories, the model described both the particle density and the normalized probability density. However, it did not investigate interactions between the carrier gas, shield gas, and mass flow rate. On the other hand, Zhang et al. [5] developed a numerical model to predict powder stream characteristics in HSLC, considering the influence of shield gas, carrier gas, and mass flow rate. Although their model was validated by comparing simulated powder density distributions to high-speed camera images, it has several limitations, such as restricted validation conditions, lack of particle velocity analysis, and omission of particle-to-particle interactions, which become critical at high mass flow rates. In this project, a state-of-the-art Computational Fluid Dynamics–Discrete Element Method (CFD-DEM) model developed at AMLZ (Figure 2) and described by Deifilia To [6] (former master's student) will be adapted to simulate powder stream behavior in HSLC. The model incorporates compressibility, particle-wall and particle-particle collisions, turbulence, and gas mixing. Validation will be conducted by characterizing the powder stream of a custom dual-system HSLC machine at Inspire AG, utilizing high-speed camera imaging and processing and a cutting-edge powder caustic scanner (Figure 3). The effects of shield gas, carrier gas, and mass flow rate will be explored, and the model’s robustness will be tested with different materials and nozzle types. If the final results are promising, they can potentially be turned into publications. Seeing our recently published paper [6] derived from Deifilia’s master thesis.
This project aims to enhance the understanding and control of powder stream behaviors in HSLC by optimizing and validating a high-fidelity numerical model.
This project aims to enhance the understanding and control of powder stream behaviors in HSLC by optimizing and validating a high-fidelity numerical model.
Dr. Zhilang Zhang, Mr. Francesco Rippa
Email: zhilzhang@ethz.ch, francesco.rippa@inspire.ch
Dr. Zhilang Zhang, Mr. Francesco Rippa Email: zhilzhang@ethz.ch, francesco.rippa@inspire.ch
Project Description _HSLC investigation.pdf
