Modeling of Suspension Plasma Spraying Process

Suspension plasma spraying (SPS) process, a relatively new deposition technique in thermal spray coating, has been increasingly applied to deposit high-quality coatings using sub-micron particles. Realistic simulation of the plasma jet and arc attachment inside the torch would, therefore, significantly help to better understand and improve this process. For this reason, a 3D transient model is developed in this work to simulate the magneto-hydrodynamic fields inside a DC plasma torch including arc attachment. The Reynolds Stress Model (RSM) is used to simulate the time-dependent turbulent plasma flow. To investigate the effects of plasma arc fluctuation on the trajectory, temperature, and velocity of suspension droplets injected into the plasma jet, a two-way coupled Eulerian-Lagrangian method is employed. Sub-micron yttria-stabilized zirconia (YSZ) particles, suspended in ethanol, are modeled as multicomponent droplets. The Kelvin-Helmholtz Rayleigh-Taylor (KHRT) breakup model is used to simulate the droplet breakup. The particles are also tracked after the completion of suspension breakup and evaporation to obtain the in-flight particle conditions including the trajectory, size, velocity, and temperature. The arc attachment spots showed a good agreement with the experimental images. It was also shown that the particles properties are significantly affected by plasma arc fluctuations.