Development History of Thermal Spraying Technology-Material and Equipment Development

       With the development of spraying technology, new coating materials are constantly appearing. In the early 1950s, self-fluxing alloy powder materials were developed, followed by the emergence of powder flame spray welding technology. The successful research on self-fluxing alloy powder materials has played a powerful role in promoting the application of thermal spraying technology in the industrial field. The thermal spraying technology has been developed from the original surface protection and repair to the surface strengthening of mechanical parts. It is not only used for the repair of waste parts, but also for the preparation of pre-protection and strengthening coatings for new parts, creating the application of thermal spraying technology. new field.



In the late 1950s, the United Carbide Company of the United States successfully developed the gas repeated explosive spraying technology, which was used to prepare high-quality carbide coatings and oxide ceramic coatings, and was first applied to the aviation industry. The high particle velocity of gas explosion spraying can produce very good carbide cermet coatings, but the temperature is low, and there are still unsatisfactory places for the preparation of oxide ceramic coatings. With the development of aviation industry, the performance requirements of aero-engines are getting higher and higher. Engine parts must not only have high-temperature strength, but also have high-temperature thermal insulation properties, so as to achieve the purpose of effectively utilizing the thermal efficiency of the engine. Ceramic thermal barrier coating is one of the key technologies to improve the thermal efficiency of aero-engines. The basic principle is that ceramics have a high melting point and low thermal conductivity, and at the same time, the ceramic coating contains a certain porosity, which can isolate the high-temperature components of the engine and gas turbine from the high-temperature gas, so the ceramic coating becomes a good high-temperature gas. Thermal insulation coating material. In order to solve the application of ceramic coating, Plasmadyne Company and Metco Company in the United States have successfully developed plasma spraying equipment and complete sets of technology, and since then they have developed plasma spraying application technology. The application of plasma spraying technology has effectively changed the appearance of thermal spraying technology, solved the spraying technical problems of refractory metal materials and ceramic materials, improved the bonding strength of the coating and reduced the porosity of the coating, and greatly improved the coating. layer quality, promote the rapid development of thermal spray composite materials, open up new application fields in the preparation of special coating functions, greatly accelerate the development of thermal spray coating materials and expand the application range of coating technology. By the 1960s, plasma spraying technology had been widely used in the industry, and it was successfully applied to the preparation of thermal barrier coatings for aircraft engine parts, and achieved remarkable results. In the mid-1960s, the United Carbide Company of the United States successfully studied the plasma spray welding technology, supplementing and expanding the connotation of thermal spraying technology. So far, thermal spraying technology has included oxyacetylene flame spraying, spray welding; arc spraying, gas explosion spraying, plasma spraying, spray welding and other technological methods, forming a relatively complete thermal spraying from equipment, technology, coating materials to application Technology System.



With the development of industrial technology, people's continuous pursuit of high speed, high efficiency and high quality, and higher and higher requirements for the surface performance of parts, all of which have promoted the development of thermal spraying technology. In the 1970s and 1990s, thermal spraying technology developed towards high energy, high speed and high efficiency. Since the late 1970s, American metco company has gradually researched the successful 80kVA high-energy plasma spraying equipment, controllable atmosphere (low pressure or vacuum) plasma spraying equipment, JP2600 series gas high-speed flame spraying equipment: Union Carbide successfully launched D-gun Spraying technology, Stellite company successfully launched JetKote series of high-speed flame spraying equipment, series of plasma spraying equipment, Czech National Institute of Materials Protection developed a complete set of 200kVA water stable plasma spraying technology, American TAFA company researched and launched 8830, 9000 series arc spraying equipment and Plazjet250kVA High-energy and high-speed plasma spraying equipment, JP5000, JP8000 fuel high-speed flame spraying equipment; Northwest Mettech Company of Canada and Metco Company of the United States successfully researched the AxialIII three-arc axial powder feeding plasma spraying system, which greatly improves the spraying efficiency and coating material deposition efficiency, the United States The Inelli-Jet SB250, SB500 series of high-speed active gas spraying (HVAF) equipment launched by UniqueCoat company, the spraying particle speed can reach 900m/s, Russia has successfully launched the active high-speed arc spraying technology; The company has launched a complete set of equipment technology for air-conditioning power spraying.



With the application of plasma spraying and technology, the inert and high temperature jet characteristics of plasma arc provide a wider range of coating materials and coating application opportunities, which greatly enriches the development of thermal spray coating materials (especially high melting point ceramic materials). and improved coating quality. The controlled atmosphere plasma spraying technology can control the environmental factors in the spraying process, and can obtain environmental conditions such as vacuum, low pressure or inert gas. The density of the prepared coating exceeds 98%, and the oxygen content of the coating is less than 400*10-6. So far, more than 6,000 hot-end components of aero-engines and gas turbines have adopted thermal spraying technology, and the service life of their key components has been increased by 3-4 times. For example, after JT8 engine adopts thermal spraying technology, its overhaul period is increased from 4000h to 16000h. When the plasma spraying arc temperature is high, when the carbide (WC/Co) and other materials are sprayed, the carbides are inevitably decomposed and decarburized, and the coating hardness index decreases, and the high-speed gas spraying technology just makes up for this defect. High-speed gas spraying technology, such as JP5000 flame velocity up to 200m/s, particle velocity up to 700m/s, coating bonding strength ≥70MPa, WC/Co coating hardness up to 1200HV, with very excellent performance, has been replaced in many application fields Or partially replace the plasma spray coating.