Abstract
The control over coating quality in plasma spraying is partly dependent on the arc and jet instabilities of the plasma torch. Different forms of instabilities have been observed with different effects on the coating quality. We report on an investigation of these instabilities based on high-speed end-on observation of the arc. The framing rate of 40,500 frames per second has allowed the visualization of the anode attachment movement and the determination of the thickness of the cold-gas boundary layer surrounding the arc. The images have been synchronized with voltage traces. Data have been obtained for a range of arc currents, and mass flow rates for different gas injectors and for anodes displaying different amounts of wear. The analysis of the data has led to quantitative correlations between the cold-gas boundary layer thickness and the instability mode for the range of operating parameters. The arc instabilities can be seen to enhance the plasma jet instabilities and the cold-gas entrainment. These results are particularly useful for guiding plasma torch design and operation in minimizing the influence of plasma jet instabilities on coating properties.
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Z. Duan, K. Wittmann, J.F. Coudert, J. Heberlein, and P. Fauchais: Proc. 14th Int. Symp. on Plasma Chemistry, M. Hrabovsk’y, M. Konrád, and V. Kopeck’y, ed., Institute of Plasma Physics AS CR, Prague, Czech Republic, 1999, pp. 233–38.
Z. Duan, J. Heberlein, S. Janisson, K. Wittmann, J.F. Coudert, and P. Fauchais: Tagungsband Conf. Proc., E. Lugscheider and P.A. Kammer, ed., ASM International, Materials Park, OH, 1999, pp. 247–52.
M.P. Planche, Z. Duan, O. Lagnoux, J. Heberlein, J.F. Coudert, and P. Fauchais: Proc. 13th Int. Symp. Plasma Chemistry, C.K. Wu, ed., Peking University Press, Beijing, 1997, pp. 1460–65.
S. Wutzke, E. Pfender, and E. Eckert: AIAA, 1967, 5(4), pp. 1216–32.
M.I. Boulos, P. Fauchais, and E. Pfender: Thermal Plasmas: Fundamentals and Applications, Plenum Publishing, New York, NY, 1994, 1.
J.F. Coudert, M.P. Planche, and P. Fauchais: Plasma Chem. Plasma Processing, 1995, 16(1), pp. 211s-27s.
J.F. Coudert, M.P. Planche, and P. Fauchais: Plasma Chem. Plasma Processing, 1995, 15(1), pp. 47–70.
D.H. Berns: Master’s Thesis, University of Minnesota, Minneapolis, MN, 1994.
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Duan, Z., Heberlein, J. Arc instabilities in a plasma spray torch. J Therm Spray Tech 11, 44–51 (2002). https://doi.org/10.1361/105996302770348961
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DOI: https://doi.org/10.1361/105996302770348961