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1988 |
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Wednesday, May 05, 2010, Sophia Room 9:40 AM Process Diagnostics 2 |
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Improving powder injection in plasma spraying by optical diagnostics of the plasma and particle characterization |
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Georg Mauer* / Forschungszentrum Jülich GmbH, Germany Robert Vaßen/ Forschungszentrum Jülich GmbH, Institut für Energieforschung (IEF-1), Germany Detlev Stöver/ Forschungszentrum Jülich GmbH, Institut für Energieforschung (IEF-1), Germany Stefan Kirner/ Universität der Bundeswehr München, Institut für Plasmatechnik und Mathematik IPM (LPT), Germany José-Luis Marqués-López/ Universität der Bundeswehr München, Institut für Plasmatechnik und Mathematik IPM (LPT), Germany Stephan Zimmermann/ Universität der Bundeswehr München, Institut für Plasmatechnik und Mathematik IPM (LPT), Germany Günter Forster/ Universität der Bundeswehr München, Institut für Plasmatechnik und Mathematik IPM (LPT), Germany Jochen Schein/ Universität der Bundeswehr München, Institut für Plasmatechnik und Mathematik IPM (LPT), Germany |
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During plasma spraying, the feedstock particles, suspended in a carrier gas, are injected into a plasma gas jet to be melted and accelerated towards the substrate. In most cases the injection is oriented in radial direction rectangular to the torch axis. The carrier gas flow controls the radial injection speed and thus the particle trajectories through the plasma plume. It has to be adjusted carefully depending on particle characteristics and injector geometry as well as on the plasma parameters to achieve optimum heat and momentum transfer. Applying three cathode torch concepts, there is an additional important set-up parameter: the azimuthal position of the injectors has to be adjusted to achieve proper particle injection into a non-rotationally symmetric plasma jet. To identify the optimum set-up no simple indicators are available, thus sophisticated diagnostical methods are applied. Furthermore, it has to be taken into account that the shape of the plasma plume changes with the plasma parameters. At first some basic effects of the injection conditions on particle parameters based on DPV-2000 measurements using the single cathode F4 torch are presented. Furthermore, the investigation of the plasma plume by emission computer tomography is described when operating the three cathode TriplexPro? gun. By this imaging technology, the three dimensional shape of the radiating plasma jet is reproduced based on images achieved from three CCD cameras rotating around the plume axis, with each camera being equipped with a narrowband filter. It is shown how the formation of the plasma jet changes with plasma parameters and to what extent the particle trajectories are affected. The impact on particle temperatures and velocities was verified by DPV-2000 measurements. |