Numerical and Experimental Study of Particle Motion in Plasma Arc Welding

The PTA ("Plasma-Transferred-Arc") is a widespread variant of plasma powder processes to manufacture coatings against corrosion or abrasion. For the optimization of this technique, an explanation of the processes which lead to a maximal deposition performance (i.e. maximal quantity of powder converted per time) is required. Especially the gas and particle flow in the region between the burner nozzle and the work piece is of interest. In the present study, flow simulations (Computational Fluid Dynamics, CFD) have been done in order to investigate the determining factors for the dimensioning of the processes. Additionally, velocity measurements have been obtained with PIV (Particle Image Velocimetry) to validate the computations. This measurement method enables on the one hand the acquisition of the velocity in the gas-phase. On the other hand the velocity of the dispers particle flow can be examined. Due to the high intensities of the plasma light, a modified PIV setup has been used in the present analysis. Comparisons between numerical and experimental results show a good agreement of the velocity fields for large particles. In order to examine simultaneously powder made of particles of different sizes, which are common used in practice, a modified postprocessing based on the classification of the scattered light in different intensity ranges should be taken into consideration.