An Insight into Suspension Plasma Spray: Injection of the Suspension and Its Interaction with the Plasma Flow

Yttria Stabilized Zirconia (YSZ) suspensions were injected in an atmospheric plasma jet using two designs of a home-made two-fluid atomizing nozzle. The sprays of drops were visualized and the behavior of the suspension in the plasma jet was investigated by implementing the Particle Image Velocimetry (PIV) method. The effects of the suspension formulation (surface tension, liquid viscosity, and relative gas-to-liquid mass ratio, GLR) on the distribution and median value of the drop size as well as on the velocity maximum value were evaluated. The interactions between the sprays and the plasma jet were studied. The differences in the behavior of the particle velocity along and radial to the torch axis were pointed out. The validity of PIV measurements was finally demonstrated by the relation established between the in-flight particle velocity and the coating structure.