Abstract
The plasma spray technology has shown a considerably evolution during the last 10 years. Modeling and diagnostic methods also have shown a strong development and offer tools for a better characterization and simulation of the plasma spray processes. In the same time some new types of plasma torches were developed. The motivation for the development primarily was the productivity measured in spray rate and deposition efficiency. However the necessary level of energy used for the melting and the accelerating of the powder was not always considered as important factor. In the future this factor certainly will take more importance. The reliability of the process becomes to be considered as a major aspect. During the last decade two directions of development were taken. One direction is the axial injection of the powder in the plasma jet. This process allows an excellent control of particles trajectories and looks as attractive process, however the stability of the arc root is not really realized through the axial injection. The stability of plasma spray process can be increased using the principle of cascaded anode to fix the arc root and provide quasi constant condition for the melting and accelerating of the injected powder. The current density of the cathode plays an important roll regarding the time life and also the stability of the process. It was realized an improvement of a factor 5 to 10 of time life of cathode by the using a multi cathode plasma torch with low current density. This technology shows a significantly improvement by the deposition of metallic alloys and ceramic regarding the productivity and the constant quality level of the coating.
