Abstract
A 3D model was established to accurately simulate the internal and external powder stream characteristics of the coaxial discrete three-beam nozzle for laser metal deposition. A k-ε turbulence model was applied in the gas flow phase, and powder flow was coupled to the gas flow by a Euler-Lagrange approach as a discrete phase model. The simulated powder stream morphology was in good agreement with the experimental results of CCD and high-speed camera imaging. The simulation results showed that the length, diameter and shrinkage angle of the powder passage in the nozzle have different effects on the velocity and convergence characteristics of the powder stream. The influence of different particle size distribution and the inner laser shielding gas on the powder stream were also discussed in this study. By analyzing the powder stream caused by different incident directions of powder passage, and the collision process between powder and the inner wall, the basic principle of controlling powder stream convergence was obtained.
Highlights
Laser metal deposition (LMD), as an important industrial additive manufacturing technology, has been more widely used to fabricate large scale and complex shape parts.At present, the majority of the implementations of LMD technology are based around laser cladding with coaxial powder feeding
The continuous phase k-ε turbulence model was adopted for the gas flow, and the powder stream was coupled as a discrete phase in Euler–Lagrange model, which has been proved to be an effective method in previous similar studies
Analysis of the powder focus size is rarely involved in these studies because changes in powder or gas parameters would not have any effect on the convergence characteristics of the powder stream
Summary
Laser metal deposition (LMD), as an important industrial additive manufacturing technology, has been more widely used to fabricate large scale and complex shape parts. The majority of the implementations of LMD technology are based around laser cladding with coaxial powder feeding. Since LMD mainly involves the interaction between laser and powder, it is of great significance to study the powder injection process in order to improve manufacturing quality and the utilization ratio of materials. The flow and convergence characteristics of powder stream inside, and after, injecting from a coaxial nozzle have always been a focus issue. There is no recognized effective means to test and monitor the flow of powder, especially the flow inside the nozzle. Most studies adopt the combination of numerical simulation and experimental verification, which is beneficial to save the cost of experimentation
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