An Investigation of Gas-Powder Flow in Laser-Based Direct Metal Deposition

Laser-Based Direct Metal Deposition (LBDMD) is a blown-powder laser deposition process which can produce fully-dense and metallurgicaly sound parts by a layered manufacturing method. Since a deposition head equipped with discontinuous radially symmetric nozzles has the potential to be tilted without influence of the gravity on the powder stream shape, it can be used for multi-axis deposition. The shape of the gas-powder stream with respect to the shape of laser beam and the size of the molten pool, have a large influence on the size and shape of the buildup. They determine the geometrical accuracy and the surface quality of the buildup. This paper examines gas-powder flow from radially symmetric nozzles using computational fluid dynamics method. For verification purpose the powder flow was investigated by a visualization method and powder concentration distribution was analyzed using image processing technique. The obtained results are in good agreement with numerical model.