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