Diagnostics of Thermal Spraying Plasma Jets

Diagnostics of Thermal Spraying Plasma Jets
P. Fauchais, J.F. Coudert, M. Vardelle, A. Vardelle

D.C. plasma spraying is a fast growing technology which has diffused progressively from aeronautic and nuclear industries to other ones. This is due to the increasing need for thick coatings with more and more sophisticated. properties but also to a better control of the coating qualities and reproducibility. These results have been obtained thanks to a better understanding of the involved phenomena with the development of the diagnostic techniques which will be summarized in this presentation.

The way the plasma jet is formed is recalled and the consequences for its behavior (piston flow, turbulences and surrounding atmosphere pumping) described through fast camera and CARS experiments. The effect of the arc fluctuations on the spectroscopic temperature measurements is emphasized. The possibility to use these fluctuations to determine at least the axial velocity of the jet is commented... A comparison between spectroscopic and enthalpy probes measurements is presented as well as the limitations of Rayleigh technique to measure temperatures below 6000 K.

The statistical methods to measure inflight the mean particulates number flux (by laser fluxmetry), velocity (by laser anemometry), diameter (by laser scattering) and surface temperature (by two color pyrometry) is discussed together with their limitations. The way to determine the temperature and species density of the vapor surrounding the particulates in flight is also presented. Then the techniques enabling to determine the velocity, diameter and surface temperature of an unique particulate in flight is commented.

This paper was a keynote presentation at the 1992 TMS Annual Meeting.

Publisher: TMS
Product Format: PDF
Pages: 31-54
Date Published: February 1, 1992
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