Numerical Simulation And Experimental Verification Of DC Arc Plasma Sprayed Alumina

For DC arc plasma spraying, the quality of coating mainly depends on the temperature and velocity of sprayed particles before deposition. In order to prepare coating of high quality and optimize the process parameters, it’s meaningful to understand the trajectory, heating and acceleration processes of the particles in the plasma jet.On one hand, DC arc plasma spraying is a complex problem involving heat transfer, fluid flow, electromagnetic field, etc. On the other hand, the interior space of plasma generator is small, the temperature and velocity of the plasma arc and jet are high. These make it very difficult to fully reveal the flow field characteristics of the DC arc plasma spraying and the heating and acceleration processes of the sprayed particles by theoretical analysis and experimental measurement. However, numerical simulation can not only avoid the high cost of experimental measurements, but also the difficulties of theoretical analysis. Besides, numerical simulation can reveal processes comprehensive, it can help us fully understand the flow field characteristics of the DC arc plasma spraying and the heating and acceleration processes of the sprayed particles.In the paper, a three-dimensional computational model of plasma spraying was established based on the actual working conditions of the DC arc plasma sprayed Al2O3particles, which included the cathode and anode. The CFD software Fluent was used to simulate the spraying process. During the simulation, Fluent was developed secondarily by writing user defined scaler and function in C language. With the secondary development, we could not only set the power of plasma reactor being equal to the actual value by adjusting the cathode voltage, but also improve the discrete phase model of Fluent, which describes the heating and acceleration processes of the sprayed particles. The flow field distributions of DC arc plasma reactor and pure plasma jet were obtained by numerical simulation. The trajectory, heating and acceleration processes of alumina particles in the plasma jet were studied. In addition, the temperature and velocity of alumina particles along the axis of plasma torch were measured by Spray Watch3i, It proved the physical model and simulation results were reasonable by the comparison and analysis with the simulation results.