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Progress in Plasma Processing of Materials, 2001

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Influence of I.R. radiation on target pyrometric measurement under plasma spraying conditions

Thierry Renault
Laboratory Sciences of Ceramic and Surface Treatment Processes (SPCTS UMR-CNRS 6638) - 123, avenue Albert Thomas 87060 Limoges Cedex - France; Thermadyne Inc. 82 Benning Street, West Lebanon, NH 03784, USA

Cedric Bossoutrot
SPCTS UMR-CNRS 6638, 123 Avenue A. Thomas - 87060 Limoges Cedex - 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


In thermal spraying, the temperature of the substrate and previously deposited layers influences droplet flattening, interlamellar contacts, residual stresses... , and governs in consequence the coating adhesion, density, porosity. .. Substrate and coating surface temperature is generally followed by I.R. pyrometry, which however can be disturbed by plasma radiation.
The aim ofthis paper is :
• To study the plasma direct radiation and that reflected by the target by using an I.R. spectroscopic set-up.
• To measure the target radiation evolution with its temperature and roughness modifying its emissivity. In our experimental conditions with an Ar-H2 D-C plasma jet, the substrate is an Hastelloy x® (not very sensitive to oxidation), grit blasted with different Ra on top of which yttria stabilized zirconia powder is sprayed.
Possible spectral ranges where plasma emission disturbance is minimum has been deduced to carry out temperature measurements and to provide necessary corrections to pyrometric signals.