Transient Phenomena in Plasma Torches and in Plasma Sprayed Coating Generation

D.C. plasma torches are more and more widely used for different applications among which cutting, welding and spraying are probably the most developed. For a long period it is mainly their static characteristics which have been considered and their applications were studied on a macroscopic scale. However many transient phenomena occur, the systematic study of which has started only a few years ago. To limit the discussion we present only the case of plasma spraying with : the transient phenomena, at the anode, and their evolution with the torch working parameters and the electrodes erosion, the consequences of these fluctuations on plasma jet temperature and velocity fields as well as mean electric field in the arc column, the characterization of the molten particles flattening and resulting splat cooling and consequences on coating properties.