Laser direct deposition of metal powder is one of the established additive technologies, which is used both for the production of new complex shape components as well as for repairing of damaged or worn-out high-value components. One of the most important properties of the laser direct deposition of powder is powder catchment efficiency. The powder catchment efficiency is significantly influenced by the diameter of powder stream at the surface of the substrate. In order to achieve high powder catchment efficiency, the diameter of the powder stream at the workpiece surface must be equal to or less than diameter of the melting pool, generated with laser beam on the workpiece surface.
In this thesis, the influence of the particle size and output geometry of the feeding tube on the properties of the powder stream was studied based on the analysis of visual images of the powder stream. For this purpose, an experimental setup was designed, built and equipped with appropriate measuring system for visualizing the powder stream. A set of measurements was performed with different values of size ranges of powder and different outlet geometries of the feeding tube. Measurements was performed at different values of the carrier gas volume flow and powder mass flow.
It was found that the outlet geometry of feeding tube has the largest influence on the diameter of the powder stream, while the influence of the particle size was insignificant. It was also found that the influence of the carrier gas volume flow and powder mass flow on the diameter of the powder stream is negligible. All results indicates that the two-phase flow of powder in carrier gas is in collision-dominated regime.
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