Gas-powder dynamics within the off-axis nozzle of the Precitec YC52 laser cladding head (Germany) has been studied using the original Tepler shadow setup, the high-speed tracing system and the laser Doppler anemometer. The length of the laminar part of the gas-powder flow has been optimized for variety of the transport and shielding gas flow, as well as the diameter of the orifice of cyclone. Powder jet at the nozzle’s outlet follows the carrier gas flow structure. In case of 4 mm nozzle’s diameter, the powder stream separates into two stable vortex structures near the surface of the substrate, causing significant losses of powder particles (about 2/3 of the total powder mass) within the melting zone, which finally reduces the efficiency of the deposition process and the powder utilization. Practical recommendations on the application of the optical diagnostic to optimize gas-powder jets for laser cladding are provided.

Keywords: laser powder cladding, shadow method, off-axis nozzle, tracing, laser Doppler anemometry, gas-powder flow optimization