Development of coating by thermal plasma spraying under very low-pressure condition <1Â mbar

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).