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 corro- sion or abrasion. For the optimization of this tech- nique, an explanation of the processes which lead to a maximal deposition performance (i.e. max- imal 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 Dynam- ics, CFD) have been done in order to investi- gate the determining factors for the dimension- ing of the processes. Additionally, velocity mea- surements have been obtained with PIV (Parti- cle Image Velocimetry) to validate the computa- tions. 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 dis- pers 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 experimen- tal results show a good agreement of the veloc- ity fields for large particles. In order to examine simultaneously powder made of particles of dif- ferent sizes, which are common used in practice, a modified postprocessing based on the classifi- cation of the scattered light in different intensity ranges should be taken into consideration.