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Progress in Plasma Processing of Materials, 1997

ISBN:
1-56700-093-2 (Print)

EXPERIMENTAL INVESTIGATION OF METAL PARTICLE VAPORIZATION IN PLASMA SPRAYING

K.-I. Li
EPM-Madylam, ENSHMG, BP 95, F-384G2 Saint Martin d'Heres, France

Michel Vardelle
LMCTS-URA 320, University of Limoges, 123 Avenue Albert Thomas -87060 Limoges Cedex - France

Pierre Fauchais
Laboratoire Sciences des Procedes Ceramiques et de Traitements de Surface UMR CNRS 6638 University of Limoges 123 avenue Albert Thomas, 87060 LIMOGES - France

C. Trassy
UPR 9033 CNRS - EPM, ENSHMG BP 95 - 38402 Saint-Martin-d'Heres - France

Abstract

The phenomenon of particle vaporization in a dc plasma jets is difficult to control. It depends on thermal properties of plasma-forming gas, the plasma jet's length and diameter, the size and trajectory of injected particles. The vaporization of particles is detrimental to the deposition efficiency and may affect the coating quality. in plasma spraying, however, it could be desired in other plasma processes (for example : selective evaporation for metals purification and plasma assisted chemical vapor deposition process).
To have a better understanding of particle vaporization under plasma spraying conditions, and especially the effect of vapor issuing from particles on. coating formation, the vaporization of metallic powders was investigated using an absorption spectroscopic technique which allows determination of metal vapor concentration within the plasma jet and its plume.
Several absorption lines have been utilized in real time mode in this technique to determine the metallic gas density surrounding a single evaporating in flight particle and the geometry of its vapor cloud. Results on iron powders injected in different plasma gas mixtures are reported.