Effect of Torch Nozzle Geometry on Particle Temperature and Velocity

Plasma torch nozzle geometry can be engineered to improve the efficiency of heat and momentum transfer from the plasma to the powder. Such a nozzle can achieve higher particle temperatures and velocities for the same plasma recipe. Alternatively, if the desired particle temperature has been determined for a given coating application, a thermally efficient nozzle would achieve this at a lower input power. This not only saves the cost of running the torch but also extends consumable parts lifetime.

This work presents the effect of nozzle geometry on particle temperature and velocity. Experimentally, the Axial III Plus torch was assembled with a standard nozzle and used to spray powder at a given plasma recipe and feed rate. An Accuraspray was used to measure the particle temperature and velocity at various stand-off distances and plotted to obtain the control/target profiles for temperature and velocity. The experiment was then repeated with the modified nozzle, and the parameters adjusted until the temperature and velocity profiles matched that of the standard nozzle. The significance of our findings with the new nozzle will be highlighted.