Computer modelling of the influence of process parameters on the heating and acceleration of particles during plasma spraying

The motion and heating of feedstock particles in the jet during plasma spraying have been simulated using a theoretical model based on a CFD code. The main parameters affecting particle behaviour are the particle diameter, powder injection velocity, the flow velocity and temperature of the plasma gas at the nozzle inlet. There is found to be a strong interaction between the flow field characteristics and the particle parameters, which complicates the particle behaviour during spraying. The work demonstrates that particle velocity and surface temperature measurements provide limited information and a coherent computational model is required for process optimization. An end state of in-flight particles is proposed as a means of improving the methodology for the control of thermal spraying. Contour diagrams of end-state parameters against injection velocity and particle size are presented as a guide for improved process control.