Experimental analysis of the powder flow in a continuous coaxial nozzle for laser metal deposition

This work presents an experimental analysis of the powder flow from a continuous coaxial nozzle for Laser Metal Deposition (LMD), demonstrating the ability to identify the transients and high-speed process flow dynamics. High-speed video tracking of individual particles enabled detailed analysis of size, spatial distribution, and velocities, revealing significant flowrate variations over time of up to $$20%$$ , which may compromise deposition quality. These oscillations emerge from the large number of interactions among particles, carrier gas, and nozzle walls, reflecting complex, self-excited flow dynamics not captured by time-averaged measurements. The standoff distance, defined as the optimal distance between the nozzle and the workpiece, was determined with unprecedented temporal resolution. In the most representative case, the average standoff distance was found to be approximately 16.0~mm , with oscillations over time of up to $$19%$$ , due to variations in both particle trajectories and quantity over time. The particle size distribution was consistent with the manufacturer’s specifications, a good indication of the method’s accuracy, and an error estimation is performed to determine the expected precision of the measurements. A key aspect of this work, and its main contribution, is the development of a workflow capable of tracking individual particles to determine the instantaneous powder mass flowrate, providing a reliable approach to monitor and optimize powder delivery in the LMD process.