First, the characteristics and development of surface engineering and thermal spraying technology
Surface engineering is a surface treatment, surface coating, surface modification or a variety of surface engineering techniques to change the morphology, chemical composition and microstructure and stress state of solid metal surfaces and non-metal surfaces to obtain the required System engineering of surface properties.
Surface engineering combines basic theories, techniques and latest developments in multiple fields. Surface engineering technology creates a coating or film on the surface of the substrate material, or imparts many special properties to the material through surface modification, so that the surface properties of the material are much better than the material matrix, which not only greatly extends the application of the matrix material, but also Solved the problem that materials in many fields cannot meet environmental requirements. Surface engineering technology plays an irreplaceable role in solving common problems such as resources, energy and environment in human development.
Because surface engineering technology saves energy and materials, it protects the precious resources that human beings depend on, and it also plays a very important role in environmental protection. Surface engineering technology in the 21st century will infiltrate all walks of life, promote social civilization and improve the quality of life.
Thermal spraying technology is an important branch of surface engineering. It heats a certain linear and powdery material to a molten or semi-melted state by a heat source such as flame, arc or plasma, and accelerates the formation of droplets at high speed. Spraying onto the substrate forms a coating. The coating is resistant to wear, corrosion, high temperatures and thermal insulation, and can be repaired against wear and tear, corrosion or machining. The application of thermal spraying technology mainly includes four aspects: long-term anti-corrosion, mechanical repair and advanced manufacturing technology, mold making and repair, and manufacturing special functional coating. At present, thermal spray technology has been widely used in almost all industrial fields as well as household products (such as non-stick pans, infrared health heaters, etc.).
At the end of the 20th century, thermal spray technology developed rapidly and was quickly promoted. From 1980 to 2000, the changes in the thermal spray market are shown in Table 1. By the end of the 20th century, plasma spraying still dominated. It is worth noting that the rapid development of high-speed flame spraying (HVOF) will occupy 25% of the market share, ranking second. The arc spraying technology, due to its good economy and superior coating performance compared to the flame spraying layer, will partially replace the flame spraying technology to the third place.
The development trends and characteristics in recent years are:
1. Large-area long-term protection technology has been widely used. For steel structures that have been exposed to the outdoor atmosphere for a long time, aluminum, zinc and alloy coatings are sprayed instead of traditional brushing methods, and cathodic protection is applied for long-term atmospheric corrosion protection;
2. Using thermal spraying technology to repair and strengthen the localization of large-scale key equipment and imported parts;
3. Application of supersonic flame spraying technology:
4. The gas deflagration spraying technology is further applied;
5. high-speed, automatic oxyacetylene flame spray technology developed rapidly;
6. The thermal spray technology is applied in chemical anti-corrosion engineering;
7. Laser remelting technology began to be applied. At present, thermal spraying technology has been widely used in many engineering fields such as military, water conservancy, electric power, chemical industry, construction, environmental protection, biology, etc. Thermal spraying has also been widely used in marine engineering. For hulls, decks, barges, large flat bottoms, tugs, etc., thermal spraying has achieved good long-term protection.
Second, the application of thermal spraying technology in the chemical industry and petroleum industry
In the chemical industry, corrosion is particularly serious. It not only causes a large loss of materials and equipment, but also causes the company to stop production due to corrosion. The damage caused by safety accidents and environmental pollution is even more difficult to estimate. Preventing “run, run, drip, and leak” is one of the main tasks of equipment management in chemical companies. The thermal spray technology, which combines various processes and has the purpose of surface strengthening, can spray all solid engineering materials and has good chemical stability. It has been widely used in the chemical industry. Chemical media often contain sulfur and oxygen, such as fuel, alcohol, acetic acid, toluene, glycerin, syrup storage tanks, the original shaft sleeve mechanical seal and the impeller, can be anti-corrosion by thermal spraying. Generally, the weakly corrosive medium can be solved by metal thermal spraying of aluminum, zinc and stainless steel, and the solution of strong acid, alkali and the like by spraying epoxy and polytetrafluoroethylene through plastic flame. The effect is very significant. The typical application of thermal spraying in the chemical industry has the following aspects: 1. Replace the stainless steel, titanium alloy and other high-grade stainless steel with low-grade materials and heated spray coating. 2. It can be used as anti-corrosion coating for chemical reaction tanks, storage tanks, stirring devices and pipelines. 3. It can be used as a good repair layer for the collapse of the glass-lined equipment.
Thermal spraying has also been widely used in the petroleum industry. Thermal spraying has been successfully used for the repair and protection of equipment such as oil exploration and mining. Thermal spray coating has been successfully used for long-term corrosion protection of petroleum steel pipes and offshore platforms. The arc spraying technology introduced by the engineering installation company of a downhole operation company has solved the metal anti-corrosion problem and filled the metal anti-corrosion blank of the oilfield. The engineering installation company has applied this technology to wire, sheet, profile and metal equipment, and the anti-corrosion ability of the product after spraying has increased by more than 2 times.
