Application Areas of Thermal Spray Technology

In recent years, thermal spray technologies have evolved from crude processes that were relatively difficult to control, into increasingly precise tools where the process is tailored to take into account the properties of both the deposited material and the required coatings.

Thermal spray technology is continuously developing and new applications are seen for thermally sprayed coating materials and structures. Let's learn the main application areas of thermal spray technology.

1. Aviation

Thermal spraying technology is widely used in the aviation field, such as spraying thermal barrier coatings (bonding layer + ceramic surface layer) on aircraft engine blades. Plasma spraying, supersonic flame spraying bonding layers, such as NiCoCrAlY and CoNiCrAlY, and ceramic surface layer, such as 8% Y0-ZrO(YSZ) oxide (containing rare earth oxide) doping YSZ modification, such as TiO+YSZ, YSZ+ A10 or rare earth lanthanum zirconate-based oxides such as La(ZoCe)024 have also been studied as thermal barrier coatings on rocket engine combustion chambers5. The main rotor shaft of helicopters for military operations in desert areas is easily eroded by sand. The use of HVOF and explosive spraying of WC12Co can improve its wear resistance. HVOF sprays Al-SiC coating on the magnesium alloy substrate for aviation, which can improve wear resistance.

2. Steel and Oil Industry

The iron and steel industry is an important field of thermal spray application, and it is the second largest industry in China after thermal spray application in the aviation industry. In 2009, China's crude steel output accounted for 47% of the world's crude steel output. It is a veritable steel country, but it is not a steel powerhouse. Some high-quality steel still needs to be imported in large quantities. One of the more important reasons is that China's thermal spraying is less used in the steel industry. Such as blast furnace tuyere, high-temperature annealing furnace roller, hot roller plate conveying roller, support roller, straightening roller, galvanized lifting the roller, sinking roller, etc. The use of thermal spray coating on these components can greatly improve work efficiency and reduce costs, Improve the quality of products, and the benefits are significant 19-0.

At the 2011 ITSC conference, Japanese expert Namba investigated the patents related to the application of thermal spraying in the steel industry worldwide. The survey results show that from 1990 to 2009, Japanese patents accounted for 39%, US patents accounted for 22%, European patents accounted for 17%, Chinese patents accounted for 9%, Korean patents account for 6%, Russian patents account for 3%, Brazilian patents account for 3%, and Indian patents account for 1%. Compared with developed countries such as Japan, Europe, and the United States, the application of thermal spraying in the steel industry in China is less, and the development space is huge.

The detailed reports related to the meeting also included NiCrAlY and YO powders as raw materials, NiCrAlY-Y0 spray powders were prepared by agglomeration sintering and mixing methods, and coatings were prepared by HVOFDJ2700 spray gun. Simulate the anti-buildup of furnace rolls in the steel industry. The research results show that the powder coating prepared by the agglomeration sintering method has excellent anti-manganese oxide build-up resistance, but poor resistance to iron oxide build-up. Coatings prepared from mixed powders.

Thermal spraying technology is widely used in gas, oil pipeline, and gate valve surface spraying anti-corrosion and wear-resistant coatings, most of which are HVOF spraying WC10Co4Cr coating.

3. New energy, new equipment, and gas turbines

Solid fuel cells (SOFCs) are now designed in the direction of flat plates and thin plates, including anodes, electrolytes, cathodes, and protective layers. At present, the material design and production technology of solid fuel cells have matured, and the main problem is the preparation problem. Thermal spraying technology (low-pressure plasma spraying, vacuum plasma spraying) has become the most popular technology. The successful application of thermal spraying on SOFC is the latest application of thermal spraying technology in new energy, and also promotes the development of related spraying materials. For example, the plasma sprayed LaSrMnO (LSM) spray material, the German HC.Starck company has already started the production and sales of this material and related materials. The researchers also used liquid-phase plasma spraying to prepare the electrode material LiFePO for lithium-ion batteries. related research reports.

The development of thermal spraying technology is inseparable from the update of equipment. Every international thermal spraying conference will have reports on related new equipment. Because of its low temperature and high-speed design, the K2 spray gun for GTV HVOF spraying can spray metal coatings such as Cu coatings, and the oxygen content of the coating is only 0.04%, which is comparable to cold spraying. Using a high-pressure HVOF spraying system, the combustion chamber pressure can reach 1~3MPa, and the flame flow is low temperature and high speed, spraying 316L stainless steel powder, the deposition efficiency can reach 90%.

Industrial gas turbine blades have begun to use plasma-sprayed thermal barrier coatings, such as YSZ, LazZrzO, SmzZrzO, GdzZr20 coating systems, which are widely used abroad and are currently a popular research field in China.

4. Mechanical wear resistance

Thermal spraying technology has always been an important part of every international thermal spraying conference in the field of wear resistance because almost all workpiece surfaces have wear and tear, and surface strengthening and repair are the future trends of technological development, especially with The technology has a wide range of applications in the wear-resistant industry and also promotes the development of thermal spray wear-resistant materials. The most widely used wear-resistant coatings are: spray welding (flame spraying + remelting) NiCrBSi alloys, which are also the most widely used and studied in the wear-resistant field, such as HVOF spraying FeCrNBC coating, arc spraying NiCrBSi after remelting Research on microstructure and wear resistance, etc.; HVOF spraying, cold spraying tungsten carbide-based coatings, and chromium carbide-based coatings are the most widely used and researched in the field of wear resistance; China's high-end industry tungsten carbide-based spray powders rely on imports, such as aircraft Spraying of the falling frame, sinking roller, corrugating roller, etc. With the development of cold spraying and warm spraying technology to prepare tungsten carbide-based coating, there are also new requirements for tungsten carbide-based spraying powder, such as the powder particle size requirement is -20um+5um.

5. Nanostructures and new materials

Nanostructured coatings, powders, and new materials have been the focus of international research over the years. Nanostructured WC12Co coating is prepared by HVOF spraying. The particle size of the sprayed powder is -10μm+2μm, and the WC grain size is 400nm. The German DURUM company has industrialized production. Me lenvk studied the WC10Co4Cr powder prepared by using tungsten carbide with different grain sizes as raw materials, such as WC grain size>12um (conventional structure), WC grain size 0.2~0.4um (fine grain structure), WC grain size ~0.2um (ultra-fine grain structure); WC grain size <0.2um (nanostructure), each WC10Co4Cr coating (HVOF spraying) was prepared. The research results show that the wear resistance of the fine-grain structure coating is better than that of the conventional structure coating, its wear resistance has been improved. With the shortage of traditional binder phase Co phase resources and the harm to health, foreign companies have carried out research on new binder phase spray powder in the past two years, and related products have been released. WC, chromium carbide-based new spray powder, the binder phase is FeNiCr, 316L, etc., particle size -45um+15um, the coating has excellent corrosion resistance and oxidation resistance, used in coastal, mining, and power stations.

6. Biomedical and paper printing

Thermal spray technology is more and more widely used in the medical industry, such as vacuum plasma, HVOF sprayed Ti, hydroxyapatite, and hydroxyapatite + Ti coatings used in the medical industry (dental, orthopedics). Explosive spraying of TiO2-Ag, such as deposition on Cu coils of air conditioners, can inhibit bacterial growth and keep them clean.

The application of thermal spraying technology in developed countries in Europe and the United States has been quite mature in the papermaking and printing industry, such as the corona roll plasma spraying A10+ TiO coating in the papermaking industry, and the corrugating roll HVOF spraying to prepare the WC10Co4Cr coating. The application of domestic thermal spraying in this industry is still in its infancy, and the spraying powder used depends on imports.