Plasma spraying and equipment

Plasma spraying is an important branch of thermal spraying, characterized by high jet temperature and the ability to melt almost all materials, resulting in a wide range of spraying materials. Plasma spraying can be used to prepare various coatings with excellent properties such as wear resistance, corrosion resistance, heat resistance, oxidation resistance, conductivity, insulation, etc., which are easy to operate, fast in speed, and high in efficiency; Suitable for various substrates, both metal and non-metal surfaces can be sprayed; The size range of the sprayed parts is wide, which can be used for both large-scale spraying and local spraying of large components; It can be used for both product manufacturing and core repair. Based on the enormous potential of the thermal spraying market and its social and economic benefits, thermal spraying technology has received great attention worldwide.

At present, plasma spraying equipment used in China is both imported and domestically produced. The imported equipment mainly includes brands such as Sulzer Metco, Praxair, FST, etc. The composition of plasma spraying equipment includes: spray gun, rectifier power supply, control system, heat exchange system, powder feeder, water and electricity conversion box, compressed gas supply system, and working gas supply system.

(1) Spray gun: The plasma spray gun is a key part of the entire system, and the quality of the spray gun directly affects whether spraying can proceed normally and the quality of the coating. Spray gun composition: nozzle, motor rod, electrode, insulator, etc. The nozzle is a key part of the spray gun, and during use, the local heat load is high and easy to burn, requiring cooling water to cool the electrode. In addition to many new spray guns developed abroad, such as METCO 9MB and 10MB manufactured by METCO company. Domestic research in this area is relatively backward, and it is necessary to increase investment in product research and development, strive to improve technical level, and shorten the gap between domestic and foreign brands.

(2) Rectifier power supply: Rectifier power supply is a device that provides electrical energy. Currently, it is mainly used for thyristor rectification, consisting of transformers, reactors, rectifiers, and contactors. The plasma spraying power supply in foreign countries is mainly rectifier type power supply, such as METCO company, which uses thyristor rectifier type; Swiss company Casolin adopts a small transistor power supply, with a compact design, small size, and light weight.

(3) Control system: The central system of the entire equipment, consisting of an electrical control system, an air circuit control system, and a working state control system. The control circuits mainly include fixed program relays, programmable controllers, and computer control systems.

(4) Powder feeder: A device that provides powder to the spray gun during the spraying process, usually requiring a powder particle size range of 5-200 μ m. The powder feeding accuracy is ± 0.1%. The powder feeder includes: 1) fluidized bed type; 2) Positive displacement formula.

(5) Heat exchange system: Heat exchange systems can be divided into two types: water pump refrigeration heat exchange system and Freon refrigeration system.