Plasma is considered the fourth stage of matter in physics.
It is a ionised gas made up of charged particles, a wholly neutral set of ions and electrons, whose total electric charge is near zero.
Plasma coating technology employs an electric torch that generates a direct flow of plasma from a nozzle.
Working principle exploits a plasma flame to melt and to accelerate the particles that will form the coating.
Thermal spraying
Wear
Thermal barriers
Dielectric
Plasma coating
Corrosion
Ceramics
Flexibility
The fourth stage of matter is reached through an electric arc established between two electrodes. Inside the nozzle in which the arc springs, a gas or a blend of gases flows (usually argon, nitrogen, helium or hydrogen are used). At this point the plasma flame is released at temperatures that often exceed 10.000 °C.
In the field of termal spray coatings, plasma spray is the most complete and flexible technology, it allows to coat a wide range of metallic, ceramic and even plastic materials.
Over the years great improvements have been performed in the field of ceramic coatings. Spray plasma coating technology has the advantage of operating at a high melting point, enabling therefore the use of materials that can not be employed by other coating technologies.
The best example is zirconia, a refractory material par excellence, largely employed in the aeronautic and turbogas sectors as thermal barrier.
Other common coatings are those made of chromium oxide, exploited because of its wear resistance and density properties, aluminium oxide, insulating material and perfect against corrosion in general, and titanium coatings.
Using metallic powders plasma generates thicker, more adherent and qualitatively higher coatings if compared to other technologies, except for HVOF. Among the most common plasma coatings it is possible to include molybdenum, copper, tungsten carbides, steel and nickel coatings.