Influence of process parameters on powder jet properties in L-DEDp using different nozzle designs

In the Laser Directed Energy Deposition (L-DEDp) process, a laser melts fine metal powder delivered through a carrier gas as a focused powder jet. The geometry and behaviour of this jet, particularly its stand-off distance and focus diameter, are directly influenced by process parameters such as carrier gas flow, shielding gas flow, and powder mass flow. These characteristics affect the interaction between the laser and the material, which influence the deposition quality. In this study, a camera-based monitoring system was employed to capture images of the powder gas jet stream (PGJS), enabling precise measurement of its geometrical features through image processing techniques. Experiments were conducted using two different nozzle designs across a wide range of process parameters to investigate how each parameter influences the jet’s shape and stability. The results show that carrier gas has a dominant effect on particle velocity and jet convergence, while powder mass flow primarily impacts the jet’s focus diameter. Shielding gas was found to affect stand-off distance more significantly at lower carrier gas levels. This work contributes to a better understanding of PGJS behaviour and provides valuable insights for optimising L-DEDp across different nozzle configurations.