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Thermal spraying technology is the use of heat sources to heat the spray material to melt or semi-melt state, and at a certain speed spray deposited to the surface of the pre-treated substrate to form a coating.
thermal spraying with a wide range of materials, light equipment, flexible process, less operating procedures, quick repair, adaptability, coating thickness control and other advantages, applicable to a variety of substrate material parts, almost all solid material surface preparation of a variety of protective coatings and functional coatings, has been widely used in petrochemical, aerospace, transportation, paper and machinery and other fields.
01 Application of thermal spraying in aero engines
Aero engines, more than 75% of engine components need to be sprayed, different components have different coating performance requirements, and the performance is related to coating materials, spraying process, spraying technology . Among them, thermal spraying material is one of the core of technology, the development of thermal spray material can provide better safety for aviation engines, which gives a lot of room for the development of coating materials.
Below is a brief explanation of the application of several types of thermal spray materials in aero engines:
wear-resistant coating materials
in the field of mechanical engineering, one of the most common forms of failure is due to wear and tear of machine parts due to long operation. The way to reduce this mechanical failure is to replace parts in time or enhance the wear resistance of parts, but frequent replacement of parts will inevitably lead to greater waste of human and financial resources. The appearance of wear-resistant materials greatly meets people's needs and reduces the wear caused by materials flushing equipment components. For the components of aviation engines, its wear-resistant coating material must meet the requirements of high melting point, high hardness, good resistance to shock wear and so on, the wear-resistant coating obtained by thermal spraying technology has excellent wear resistance.
coating material, the
between the rots also has a great impact on the efficiency of the aircraft engine. Smaller clearances not only greatly improve the efficiency and fuel consumption of aeronautical engines, but also improve the safety performance of the engine, so a large number of sealing coating materials are used in aero engines. In order to meet the current operating requirements of aviation engines, aviation engines use sealing coating materials need to have high strength and resistance to gas impact, generally metal and non-metallic composite materials, so far there are more than 20 feasible spray materials, ceramic materials and nanomaterials and other thermal spray materials research is also under way.
high temperature protective coating material
aviation engine in the course of operation will generate a lot of heat, in order to prevent engine components due to high temperature oxidation and other phenomena, the need to spray high temperature protective materials on its surface. Depending on the actual requirements during operation, the applied high temperature protective coating, in addition to having basic high temperature resistance and antioxidant properties, also requires that the material of this coating material do not decompose at high temperature conditions and do not react with the surface of the applied body.
size repair coating material
in the operation of the aero engine, the application of the corresponding material on the surface of its parts, just to effectively reduce the probability of wear or other damage, and can not directly prevent the occurrence of such damage. Therefore, after a long period of operation of the aviation engine, it is inevitable that some parts will appear wear or other damage, and these damage will change the size of the original parts, affecting the normal operation of the machine, so the study of repair coating materials is also extremely important. In addition, according to the actual repair process, it is possible to adopt the corresponding scientific and reasonable spraying technology and spraying process.
engine performance, reduce maintenance costs, extend life, improve safety index.
application of thermal spraying in boiler protection in thermal power plants
boiler is a special closed thermal equipment. Not only directly to be washed by flame and smoke, but also to bear higher than atmospheric pressure of the medium pressure. In boiler accidents, "four tubes" (refers to water-cooled wall pipes, superheated tubes, reheated tubes and coal-saving pipes) have the largest number of bursts, accounting for about 40%-60% of all boiler accidents, or even up to 70%. Therefore, strengthening the maintenance and maintenance of boilers is one of the most important links to ensure the safe and economical operation of boilers.thermal spraying technology, as one of the important components of surface engineering technology, because of its strong material adaptability, in many operating conditions with excellent wear resistance, corrosion resistance, high temperature resistance, insulation capacity, its application in the field of boiler protection is the inevitable result of scientific and technological development.
The spraying process typically goes through four stages: the spray material is heated and melted, the melted spray material is atomized, the fine particles that melt or melt are ejected, and the particles collide, deform, solidify and accumulate on the substrate surface to form a coating.can be divided into three categories depending on the type of energy used (see figure below). At present, the most widely used in the field of boiler protection in coal-fired power plants in China is arc spraying technology. In addition, supersonic flame spraying and flame powder spraying technology have a certain degree of application.
arc spraying technology is . Arc spraying is the use of two sprayed wire as self-consumption electrodes, when the two wire short will ignite the arc, as long as the wire continuously into, and constantly replenish the melting and compressed air blowing to the work piece, can maintain the arc combustion that spray process. Compared with other thermal spraying processes, arc spraying equipment is simple, spraying cost is low but high efficiency, and the requirements of operators are low, the site construction repeatability is strong. Therefore, in the power plant boiler "four-tube" on-site spray protection, the arc spraying process is generally used.
supersonic flame spray technology is . Ultrasonic flame spraying technology is a method to make gas and combustion gas burn in the combustion chamber to produce high-pressure flame, and then by special nozzles to shoot out high-speed flame flow, so that the powder material into which to heat, accelerate injection to the surface of the substitut to form a coating. The coating prepared using the ultrasonic spraying process is very dense, with high binding strength and very low porosity. NiCr-Cr3C2 is the most commonly used powder material when using ultrasonic flame spraying process to protect the boiler pipe wall of power plant, and has good wear resistance.
flame powder spraying technology is . Powder flame spraying is a heat source using oxyacetylene flame and powder as a spray material. During the spraying process or after the formation of the coating, the substrate and coating are heated so that the coating melts on the surface of the substrate and diffuses or melts with the substrate to form a coating that is combined with the metallurgy of the substrate.
Reduce maintenance costs, improve production efficiency, improve equipment safety performance
03 Other applications
thermal spraying technology in metallurgy, transportation, incineration boilers, chemical industrial boilers, marine petrochemicals, printing and paper industry, general machinery and other aspects of many applications.
thermal spraying technology has been developed and widely used in China, and has made important contributions in the national economy, but there are still some problems in the practical application of thermal spraying. Specific analysis, see the next decomposition.
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