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This paper deals with the diagnostic yttria-stabilized zirconia (YSZ) in-flight particles in Vacuum Plasma Spray (VPS) process using an optical measurement device. Particle velocity, temperature and diameter were correlated to spray distance under a fixed chamber pressure of about 14 kPa. Experiments were carried out with a two-color pyrometer. Results show that correlations can be satisfactory described with linear relationships. Particle velocity and temperature decrease when increasing spray distance whereas particle diameter exhibits a linear increase with the spray distance.

Very Low-Pressure Plasma Spray (VLPPS under 1 mbar) has been developed and used for deposition of copper powder (10–63 μm) coating on stainless steel substrate. In order to improve the understanding of this technique and to study the volatilization of the injected powder in supersonic plasma, optical emission spectroscopy study has been carried out. Preliminary results of the properties and the structure of VLPPS copper coating are presented. It is shown that the plasma expansion with decreasing chamber pressure increases the volatilization of particles and allows to obtain a very dense coating with crystalline structures and avoids oxygen, due to the preheating of the substrate with plasma (length about 1.50 m).