Arc spraying is one of the methods of thermal spraying of coatings, which consists in feeding two wires independently to the head of the gun, where an electric arc is generated between them. The heat from the arc melts the wires. The molten material is sprayed with compressed air and accelerated towards the properly prepared surface of the object. The particles of the material hitting the substrate rapidly solidify, forming a coating.
Material: solid and flux wires
Supersonic spraying is flame spraying. However, compared to conventional flame spraying (LVOF), the HVOF method has a supersonic jet of gases exiting the nozzle. High speed is obtained by feeding a mixture of gases or liquid fuel and oxygen into the combustion chamber of the spray gun, where they are ignited and then continuously burned. The hot gas formed as a result of combustion is “ejected” under high pressure through the nozzle, reaching a speed exceeding the speed of sound (>1000m/s), allowing the particles of the coating material in the form of powder to be accelerated to 800m/s. In another method, a high-pressure nozzle is used – the combustion of the gas mixture takes place outside it. Compressed air is used to focus the beam of sprayed material, which simultaneously cools the nozzle. The fuel can be gaseous (propane, acetylene, natural gas, etc.) or liquid (kerosene, etc.). The powder is fed axially with compressed nitrogen into the gas stream, or injected through a hole in the wall of the nozzle where the pressure is lower. As a result, it reaches high kinetic energy, is melted or melted, and then deposited on the surface of the element, forming a coating.
Material: metallic powders, cermet