Atmospheric Plasma Spraying Evolution Since the Sixties Through Modeling, Measurements and Sensors

Abstract

This paper presents, through examples, the evolutions of atmospheric plasma spraying since the sixties. The drastic improvement of the spray conditions and coatings reproducibility during more than 50 years was linked both to researches in laboratories and developments of spray equipment’s (plasma torches, computerized control panels, robots to spray coatings on complex parts, sensors working in the harsh environment of spray booths…). This evolution is illustrated through the following topics: (1) plasma forming gas thermodynamic and transport properties either at local thermodynamic equilibrium or more recently at two temperatures; (2) evolution of plasma spray torches since the nineties; (3) plasma jet and in-flight particle measurements with laboratory equipment’s and then sensors in spray booths; (4) plasma jets and torches modeling as well as heat and momentum transfer to particles; (5) splats formation and layering.