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1161 |
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Wednesday, June 04, 2008, Room 08 3:00 PM Diagnostics and Sensors 2 Modern process diagnostics offer a lot of possibilities for gaining data for both quality control and process knowledge. The recorded data is the base for process models and enhances the process knowledge |
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Particle temperature fluctuations in plasma spraying |
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Simon Goutier* / S.P.C.T.S./University of Limoges, FRANCE Elise Nogues / S.P.C.T.S./University of Limoges, FRANCE Michel Vardelle/ S.P.C.T.S./University of Limoges, FRANCE Pierre Fauchais/ S.P.C.T.S./University of Limoges, FRANCE |
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In a DC plasma spray torch, the dynamic behaviour of the arc and its interaction with the electrodes result in fluctuations of arc voltage and plasma instabilities that affect the treatment of the particles injected in the plasma flow, and thus, coating quality. But it could be interesting to see if the experimentally-observed fluctuations of particle temperatures are a major phenomena and if the frequencies of these fluctuations are always in unison with those of voltage In this study, two on-line techniques are used to investigate the time-variation of particle temperatures and their correlation with voltage variation; the first technique makes it possible to analyse plasma voltage instabilities and the second one to investigate the instabilities of particle temperatures. Both allow determining the frequencies and amplitude variations of voltage and temperature. The experiments are carried out with two plasma torches (F4-type and 3MB-type) using respectively argon-hydrogen or nitrogen?hydrogen mixtures are used as plasma-forming gases. A good correlation between arc voltage and particle temperature fluctuations is observed when the plasma torch is operated with argon-hydrogen while that's not the case when the torch is operated with nitrogen-hydrogen. |