Thermal spray technology is one of the steps in equipment surface engineering

       

Boiler is a special closed thermal device. Not only is it swept away directly by flames and smoke, but it is also subjected to moderate pressures above atmospheric pressure. In boiler accidents, four pipes (water-cooled wall pipes, superheater pipes, economizer pipes) leak the most in boiler accidents, accounting for about 40%-60% of boiler accidents, even as high as 70%. Strengthening the maintenance of the boiler is an important link to ensure the safe and economical operation of the boiler.

Thermal spraying technology is one of the important components of surface engineering technology. Due to its material adaptability, it has excellent wear resistance, corrosion resistance, high temperature resistance and insulation under various conditions. The application in the field of boiler protection is the inevitable result of the development of science and technology.



The spraying process generally goes through the following four stages: the spraying material is heated and melted; the melted spraying material is atomized; the melted or melted particles are sprayed and fly; the particles collide, deform, solidify, and accumulate on the surface of the substrate to form a coating.

According to the different types of energy, it can be divided into three categories. At present, arc spraying technology is widely used in the field of boiler protection of coal-fired power plants in my country. In addition, supersonic flame coating and flame powder coating technology also have certain applications.

Arc spray technology

Arc coating uses two coated wires as consumable electrodes. When the two welding wires are short-circuited to ignite the arc, as long as the welding wire is continuously fed, continuously melted, and blown to the workpiece with compressed air, the arc combustion can be maintained, that is, the spraying process. Compared with other thermal coating technologies, the arc coating equipment is simple, the coating cost is low but the efficiency is high, the requirements for operators are low, and the on-site construction repeatability is strong. Therefore, the on-site coating protection of the four tubes of the power plant boiler generally adopts the arc coating technology.



Supersonic flame spraying technology

Ultrasonic flame spraying technology burns combustion-supporting gas and combustion gas in a combustion chamber to generate a high-pressure flame, and then sprays a high-speed flame flow through a special nozzle, so that the powder material fed into it is heated and sprayed on the surface of the substrate at an accelerated speed to form a coating. layer method. Coatings produced by supersonic coating technology are very dense, with high bond strength and low porosity. NiCr-Cr3C2 is a powder material commonly used to protect the boiler tube walls of power plants by using supersonic flame spraying technology, and has good wear resistance.



flame dusting technology

Powder flame coating is a thermal coating method in which oxyacetylene flame is used as heat source and powder is used as coating material. During the spraying process or after the coating is formed, the substrate and coating are heated to melt the coating on the surface of the substrate and diffuse or interfuse with the substrate to form a coating that is metallurgically bonded to the substrate.

Thermal spraying technology has a wide range of applications in metallurgy, transportation, incineration boilers, chemical boilers, offshore petrochemicals, printing and papermaking, general machinery and other fields.