Thermal spraying is referred to as spraying, which uses heat source to melt or soften the spraying material, and sprays the droplets into spraying beams by the power of the heat source itself or the compressed air flow, and sprays the droplets to the surface of the substrate at a certain speed to form the coating.

During the spraying process or after the coating is formed, the metal substrate and the coating are heated to make the coating melt on the surface of the substrate and produce diffusion or interfusion with the substrate, forming a metallurgical bonded spraying layer with the substrate. This is also one of the methods of thermal spraying, called thermal spraying welding (hereinafter referred to as spraying welding).

Corrosion starts from the surface, wears on the surface, and fatigue accelerates significantly due to surface damage. As one of the important branches of surface engineering technology, thermal spraying technology is the inevitable result of the development of science and technology in the field of boiler protection.

At present, the technology of supersonic flame spraying and arc spraying is widely used in the field of boiler protection in coal-fired power plants in China.

Supersonic flame spraying technology is a method that combusts combustion gas and combustion gas to produce high-pressure flame in the combustion chamber, and then sprays high-speed flame through a special nozzle, so as to heat and accelerate the powder material into the combustion chamber to form coating on the surface of the substrate. Liquid fuels such as propane, propylene, hydrogen and acetylene or diesel or kerosene can be used.

The coating prepared by supersonic spraying is very compact, with high bonding strength (up to 70 MPa) and very low porosity (1%-3% right). NiCr-Cr3C2 is the most commonly used powder material for the protection of boiler tube wall by supersonic flame spraying. The microhardness of the coating prepared by NiCr-Cr3C2 can reach about 1400 HV, and it has good wear resistance.

The above is the application of thermal spraying technology in the field of boiler protection in combustion power plants, which is more and more widely used in the field of boiler protection in domestic power plants.