G. Mauer, R. Vassen, J. L. Marqués-López, D. Stoever, Forschungszentrum Jülich GmbH Institute of Energy Research, Juelich, Germany
Wear at the electrode surfaces of a one-cathode plasma torch changes the characteristic fluctuation pattern of the plasma. This affects the trajectory of the particles injected into the plasma jet in a non-controllable way, which degrades the reproducibility of the process.
Time-based voltage measurements and Fourier analysis were carried out on a one-cathode F4 torch at different wear states to determine the evolution of wear dependant characteristics. A significant correlation is observed between increasing torch wear and decreasing voltage roughness and high frequency noise.
Furthermore, by means of particle diagnostic systems, the change in the particle velocity and temperature has been measured. The variations of the particle characteristics are significant and thus an influence on the sprayed coating microstructure is to be expected.
Summary: Wear at the electrode surfaces of a one-cathode plasma torch changes the characteristic fluctuation pattern of the plasma. This affects the trajectory of the particles injected into the plasma jet in a non-controllable way, which degrades the reproducibility of the process. Time-based voltage measurements and Fourier analysis were carried out on a one-cathode F4 torch at different wear states to determine the evolution of wear dependant characteristics. A significant correlation is observed between increasing torch wear and decreasing voltage roughness and high frequency noise. Furthermore, by means of particle diagnostic systems, the change in the particle velocity and temperature has been measured. The variations of the particle characteristics are significant and thus an influence on the sprayed coating microstructure is to be expected.
