1. Thermal spray ceramic powder
Thermal spray ceramic powder mainly refers to oxide, carbide, nitride, boride and silicide powder. Commonly used thermal spray ceramic powders are mainly There are Al2O3, ZrO2, TiO2, WC, Cr2O3, etc. Ceramic coating has outstanding advantages such as high hardness, good wear resistance and heat resistance. Plasma spraying can solve the problem of high melting point of materials. Almost all ceramic materials can be sprayed. Some ceramic coatings can be obtained by flame spraying.
2. Thermal spray plastic
Spray plastic on metal and non-metal surfaces, which has beautiful appearance and corrosion resistance. If a hard phase is added to the plastic powder, the coating can also have a certain degree of wear resistance. The polyethylene coating can withstand a temperature of 250°C, is resistant to corrosion by dilute sulfuric acid and dilute hydrochloric acid at room temperature, and is resistant to corrosion by concentrated hydrochloric acid, hydrofluoric acid and phosphoric acid, and has insulation and self-lubricating properties. Commonly used thermal spray plastics include nylon, epoxy resin, etc.
Thermal spray technology is a new technology for surface strengthening and protection of materials. It occupies an important position in surface modification technology. This technology began in our country in the 1950s and took shape in the late 1970s. At present, equipment, materials, processes, scientific research, etc. are rapidly developing and improving, and have become an important part of surface technology. Its development trend is: in terms of equipment (spray guns), it is developing towards high energy, high enthalpy and high speed; in terms of materials, it is developing in the direction of serialization, standardization and commercialization to ensure the needs of multi-functional and high-quality coatings; in terms of technology, it is developing towards mechanization and automation. direction development, such as computer control, robot operation, etc. Today, thermal spray technology has been widely used in various fields of the national economy, and its promotion and application prospects are broad.
1. New development of thermal spray equipment
Recently, my country has accelerated the pace of equipment development and production. At present, a complete development and production system has been formed, with more than 20 units engaged in Thermal spray equipment development and production, capable of producing various types of oxyacetylene flame spray equipment, spray melting equipment; new arc spray equipment; complete sets of plasma spray equipment, spray welding equipment; various special machine tools; thermal spray air purification equipment, pre-treatment and Post-processing equipment. There are more than 100 single machine varieties. The development and production of these products ensure the development of thermal spray technology. The more prominent ones are:
1. High-speed flame spraying device. The high-speed flame spraying device currently imported from abroad ( HVOF), (HVAF) and supersonic plasma spraying equipment, which are characterized by high particle flight speed, high bonding strength between coating and substrate, and low porosity. These equipment have played an important role in aerospace, aviation, metallurgy, chemical industry, electric power and other industries. important role. However, the above-mentioned imported equipment is expensive, and the fuel (propane, propylene) is not easy to popularize. In response to the above situation and combined with my country's national conditions, Sichuan Great Wall Spray Technology Research Institute has successfully developed a high-speed spray gun with oxyacetylene flame as the heat source. Due to the limitation of acetylene pressure, although the current flight speed of particles cannot reach supersonic speed, the flight speed is 4 to 5 times higher than that of conventional oxyacetylene flame powder spraying, and 1 to 2 times higher than that of normal pressure plasma spraying. Sprayed metal and alloy powder materials include Al2O3-TiO2-Co-WC and thermoplastic powder materials such as polyethylene and nylon. In addition, Xi'an Jiaotong University and other units have successfully developed high-velocity flame (HVOF) spraying devices and begun to apply them.
2. High-speed arc spraying device Since arc spraying has the advantages of high bonding strength, low energy consumption, and low cost, this equipment has been paid more and more attention in China in recent years and is actively used, especially It plays an important role in large-area long-term protection projects for steel structural parts and thermal corrosion of power station boiler pipes. On the basis of ordinary arc spraying, the Armored Forces Engineering College of the National Industry-Academia-Research Equipment Engineering Center and the Xi'an Second Artillery Corps Engineering College have recently successfully developed high-speed arc spraying guns. The airflow speed is as high as 600m/s or more, and its coating bonding strength, porosity Many other indicators are better than ordinary arc spraying, and it is currently being further promoted and applied.
3. Oxygen-acetylene flame metal powder spraying device Oxygen-acetylene flame metal powder spraying technology is currently widely promoted and applied in China. Almost all large enterprises use it as a means of repairing old materials and recycling them. . Shanghai, Jiangsu, Wuhan, Sichuan and other places have developed and produced various types of spraying and spray welding guns, which have been widely used by spraying units. Shanghai Welding, Cutting and Spraying Machinery Factory has recently improved on the original QHT-7/h flame spray gun, using two sets of nozzles and utilizing two heat sources: oxygen-acetylene flame and oxygen-liquefied petroleum gas (household bottled). Using bottled liquefied petroleum gas as combustible gas can greatly reduce costs and bring greater convenience to spraying operations.
4. Gas deflagration spraying device The 621 Research Institute of the Aerospace Corporation began to develop it in the 1960s and has now installed a complete set of gas explosion spraying device for aerospace, aviation and other military industries. Many high-density and high-quality coatings are sprayed, and the equipment has reached or is close to the level of similar foreign products. Beijing Great Wall Titanium Co., Ltd. has cooperated with Ukraine in recent years to establish a Sino-foreign joint venture, Beijing Titanium New Materials Co., Ltd., which has introduced Ukrainian explosive spraying equipment manufacturing technology and is now able to produce computer-controlled explosive spraying equipment for three-dimensional traveling mechanisms. In addition to domestic For outdoor use, it has been sold to the United States, Taiwan and other regions.
5. Oxygen-acetylene flame plastic powder spraying device. In recent years, oxygen-acetylene flame has been used to spray plastic powder with a boiling powder feeding method through a special spray gun to obtain a smooth and smooth plastic coating. This provides a new method for applying plastic coatings to large workpieces, various storage tanks, and pipelines. To this end, Shenyang Thermal Spray Factory, Wuhan Material Protection Research Institute, Armored Forces Engineering College, etc. have successively developed different types of flame plastic powder spraying devices, and have carried out large-scale construction, and have achieved good results. Among them, the performance of the FSP-Ⅱ plastic powder flame spray gun successfully developed by Wuhan Material Protection Research Institute has reached the level of UTP Company's I-SPRAY-JET spray gun.
6. New plasma spray gun. Tsinghua University and other units have successfully developed the QZNI high-energy inner hole plasma spray gun. The power of the gun can reach 75kW. It has thermal efficiency, average enthalpy value of plasma jet, jet temperature, spray gun power and powder. The deposition rate reaches the level of Metco large inner hole spray gun. Recently, Beijing Entropkol Applied Technology Research Institute has successfully developed the BT-G1, BT-G2, and BT-G3 new plasma spray guns, as well as the BT-NI large bore spray gun. It has also successfully developed the BT-F1 dual-type plasma spray gun. The cylindrical ultra-fine powder feeder and physical method cooling system have brought the level of domestic plasma spraying equipment to a new level and shortened the gap with foreign equipment levels.
7. The advent of new sandblasting equipment. Beijing, Shanghai and other places have recently successfully developed small recyclable sandblasting equipment and large environmentally friendly sandblasting equipment, which have greatly improved working conditions and reduced environmental pollution. It has played a positive role in promoting the development of thermal spray technology in my country.
2. New development of thermal spray materials
People call thermal spray materials the "food" of thermal spraying. The performance, quality and variety of spraying materials are one of the important levels to measure the quality of the coating, and are also key factors affecting economic benefits. Although my country's thermal spray materials started late, they have developed rapidly since the 1970s. Currently, there are more than 40 manufacturers producing nearly a hundred varieties, which can basically meet domestic needs.
Thermal spray materials developed and produced by these research and production units can be roughly divided into (recent new varieties):
1. Powder materials Yttria partially stabilized zirconia successfully developed by Beijing General Research Institute of Mining and Metallurgy Thermal gap coating materials and high-temperature oxidation-resistant nickel-chromium-aluminum-cobalt-yttrium oxide underlying materials have been widely used in aeroengines; the thermal barrier coating sprayed with air zirconia materials successfully developed by Chongqing Instrument Materials Research Institute has various The indicators also meet the requirements; the nickel-chromium-chromium carbide composite powder material successfully developed by the Beijing General Research Institute of Mining and Metallurgy has been used as a high-temperature, corrosion-resistant and wear-resistant coating on the water-cooled wall tubes of many power plant boilers, with good application results; Shenyang Grinding Wheel Factory The successfully developed alumina and alumina-titanium oxide powders have been widely used in textile machinery and metallurgical equipment. The CrB2 powder successfully developed by the plant has been sprayed on the continuous casting machine rolls and hearth rolls and has achieved initial results; Beijing Iron and Steel Research The XTiC yCr3C2 zNi composite ceramic material developed by the General Institute using the self-propagation method is suitable for plasma spraying. The coating hardness can reach 54HRC and can withstand high temperatures of 800°C. The Co-WC alloy powder produced by Zigong Cemented Carbide Factory has been widely promoted. Application: The molybdenum-based alloy powder successfully developed in Sichuan and other places has been successfully used in the spraying of automotive synchronization rings.
2. Wire materials Beijing University of Technology has successfully developed and mass-produced wear-resistant and corrosion-resistant thermal spray metal powder core wire materials containing rare earth elements. Typical ones include 7Cr13 type, 3Cr13 type, and low carbon Martensitic wire. The body shape is suitable for arc and flame spraying. The average bonding strength of the coating is 50MPa, the porosity is less than 7, and the average hardness of the coating is 40-50HRC; Beijing Nonferrous Metals Research Institute recently successfully developed Ni for arc spraying primer -Al alloy wire, and Ni-Cr alloy wire for arc spraying (equivalent to 45CT of the American TAFA company) used to resist high-temperature corrosion and abrasive wear; the Armored Forces Engineering Institute developed the SL30 Ni-Cr alloy wire coated with organic metal Composite coating has successfully replaced the 45CT of the American TAFA company; Shenyang University of Technology has successfully developed an iron-based alloy arc spray primer wire to replace aluminum bronze wire; Fe-Cr-Al has been developed and produced in Shanghai, Beijing, Zhejiang, Sichuan and other places Wire, Al-Mg alloy wire, Zn-Al alloy wire and Babbitt alloy wire, etc.
3. Plastic powders. Based on the development of polyethylene, polypropylene, nylon and other powders for oxyacetylene flame spraying, relevant units have recently successfully developed chlorinated polyethers and modified fluoroplastics. Powder has broadened the application range of plastic coatings and has been used in anti-corrosion engineering.
4. Rods The ceramic rod spray materials introduced from the United States have been successfully used in textile machinery. Domestic trial-produced ceramic rods and flexible ceramic wires have been launched and will be launched on the market soon. The above-mentioned materials are all new varieties that have recently appeared in China. The development and production of these materials have created favorable conditions for the development of thermal spray technology in my country.
3. New developments in thermal spraying technology
Thermal spraying technology has been widely promoted and applied in China. The development trends and characteristics in recent years are:
(1) Large-area long-term protection technology has been widely used. For steel structural parts exposed to the outdoor atmosphere for a long time, spraying aluminum, zinc and their alloy coatings is used instead of the traditional painting method and cathodic protection is implemented. Long-term atmospheric anticorrosion has developed rapidly in recent years. Large projects such as television towers, bridges, highway facilities, water gates, microwave towers, high-voltage transmission towers, underground cable supports, navigation beacon floats, shaft shafts and other large projects all use aluminum, zinc and their alloy spraying methods for anti-corrosion. At present, there are dozens of professional spraying factories in China engaged in this field, with the spraying area reaching more than millions of square meters every year. This technology has not only been widely promoted and applied domestically, but has also been well promoted and applied in foreign aid projects.
(2) The use of thermal spraying technology to repair and strengthen large-scale key equipment and localize imported parts has been successfully applied in many cases in recent years, such as: 1.7-meter rolling mill, high-speed fan rotor, large-scale extrusion Press plungers, large gears, electrode extrusion molding nozzles, high-power automobile crankshafts, etc.
The implementation of these tasks has, firstly, solved the urgent need for production; secondly, it has saved a lot of foreign exchange.
(3) Application of supersonic flame spray technology With the development and improvement of thermal spray technology in my country, the quality requirements for spray coatings are becoming increasingly high. The high-velocity gas-fired (HVOF) method developed in the United States and other countries in recent years is a new process for preparing high-quality coatings. Since the supersonic flame spraying method has many advantages, nearly a dozen pieces of equipment have been introduced into China from abroad, playing an important role in various industrial sectors.
(4) Gas deflagration spraying technology has been further applied. Since the particle flight speed of this spraying technology can reach more than 800m/s, the bonding strength between the coating and the substrate can reach more than 100MPa, and the porosity is <1. In certain areas, it is better than other spraying methods. At present, more than 10 units have been installed in China.
(5) Oxyacetylene flame plastic powder spraying technology has developed rapidly. As mentioned above, in recent years, many domestic manufacturers of oxyacetylene flame plastic powder spraying equipment have been used in the chemical industry. Storage tanks, pipelines, slurry machine frames in the ceramic industry, cloth guide rollers in the printing and dyeing industry, cast iron rollers for belt conveyors in the coal industry, polymer injection equipment in the petroleum industry, and surface decoration have all been well used, making up for the The shortcomings of electrospray plastic. It opens up a new way for the application of plastic coatings.
(6) Thermal spray technology is applied in chemical anti-corrosion engineering. Corrosion is one of the main reasons why mechanical parts fail due to the chemical or electrochemical effects of the surrounding medium. It not only causes the loss of a large amount of metal materials, but also makes the loss of production shutdown more difficult to estimate, so people pay special attention to chemical anti-corrosion work. Thermal spray coating is used in corrosive media, especially strong media corrosion. The main reason why it failed to break through in the past was that the sealing agent failed to solve the problem. As we all know, there are pores in the spray coating. If the pores are not sealed, various acids, alkalis, and organic media will penetrate into the pores, causing the coating to fall off and affecting the anti-corrosion effect. According to the requirements of anti-corrosion engineering, my country has recently successfully developed dozens of types of sealing agents such as polyester type, organic polymer type, resin type, plastic type, adhesive type, etc., which are suitable for corrosion by acids, alkali, salts and organic matter. Environment, its operating temperature is 80~350℃. Use ceramic coating, oxide coating or metal or alloy coating, and select appropriate sealing agent according to different media. It has been used in many chemical corrosive media with good results. This series of sealing agents has been patented and won the National Invention Award. The successful research on these sealing agents has brought new progress in the application of thermal spray technology in chemical anti-corrosion engineering.
(7) Laser remelting technology has begun to be applied. In recent years, high-frequency induction remelting and vacuum induction remelting have only been applied within a certain range. Laser remelting technology has been tested on a small area in the past few years and has not been widely used. Recently, Tsinghua University has used laser remelting technology in valve production, and Shanghai Second Textile Machinery Factory has applied laser remelting technology in textile machinery.
(8) Thermal spray technology has also been applied in architectural decoration, medical and health care. In recent years, Sichuan, Shanghai, Shenyang, Yunnan and other places have used thermal spray technology to spray various statues, ornaments, large walls, etc. Good results have been achieved, such as the large-scale mural of a peacock spreading its tail in Shenyang International Shopping Mall, which uses thermal spray technology. With the development and improvement of thermal spraying technology, this technology has penetrated into other fields. For example, the thermal spraying method is used in the biological field to manufacture artificial bones. Currently, more than 200 clinical cases have been carried out in China, and the results are very good. In addition, artificial teeth manufactured by thermal spraying have also been initially applied.
4. It is of great significance to further promote the application of thermal spray technology
Wear and corrosion are the main reasons for the failure of materials and parts. According to relevant reports, the losses caused by wear and corrosion in developed countries account for about 3 to 5 of the total national economic output. In 1993, the losses caused by corrosion in my country reached more than 100 billion yuan, with an average of 300 million yuan per day. In 1994, the total output value of my country's national economy was 4.38 trillion yuan. If calculated based on loss 4, it would be more than 170 billion yuan. The direct economic benefit of the promotion and application of thermal spray technology during the "Eighth Five-Year Plan" period was approximately 3.5 billion yuan.
As people's requirements for material performance further increase, more in-depth research and exploration will be conducted on thermal spray equipment, processes, materials, etc. Data show that the thermal spray process has broad development prospects as an excellent surface modification technology, and it is of great significance to further promote and apply this technology extensively and deeply.
Introduction to plastics
[1] Plastics are synthetic high molecular compounds {polymer}, also known as polymers or macromolecules, and are generally Plastics or resin, as they are commonly called, can be freely changed in shape and style. It is a material made of monomer raw materials through synthesis or condensation reaction polymerization. It is composed of synthetic resin and fillers, plasticizers, stabilizers, lubricants, colorants and other additives. Its main component is synthetic resin. The term resin [2] was originally named after the lipids secreted by animals and plants, such as rosin, shellac, etc. Currently, resin refers to a polymer that has not been mixed with various additives. Resin accounts for approximately 40% to 100% of the total weight of plastic. The basic properties of plastics are mainly determined by the nature of the resin, but additives also play an important role. Some plastics are basically composed of synthetic resins with no or less additives, such as plexiglass, polystyrene, etc. The so-called plastic is actually a kind of synthetic resin. Its shape is similar to the pine resin in natural resin, but it is called plastic because it is synthesized through the power of chemistry.
According to the definition of the American Society for Testing and Materials, plastic is a material with high molecular weight organic substances as its main component. It takes on a solid shape when processed. During the manufacturing and processing process, it can Use flow to create shapes.
Therefore, through this explanation we can get the following understandings:
●It is a polymer organic compound
●It can exist in various forms, such as Liquid, solid, colloidal solution, etc.
●It can be molded (moldable)
●A wide variety of different plastics due to different monomer compositions
●Wide range of uses Products are diversified
●Have different properties
●Can use different processing methods
The terms plastic and resin are also commonly used Mix it up. Figure 1.1 shows the process of plastic production.
Figure 1.1 Plastic production process
Plastics can be divided into two categories: thermosetting and thermoplastic. The former cannot be reshaped and used, while the latter can be produced repeatedly. There are basically two types of plastic polymer structures: the first is a linear structure, and polymer compounds with this structure are called linear polymer compounds; the second is a body structure, and polymer compounds with this structure Called body type polymer compounds. Some polymers have branched chains, called branched polymers, and have a linear structure. Although some polymers have cross-links between molecules, there are few cross-links, which is called a network structure and is a body structure.
Molecular structure classification of polymers:
(a) Linear structure
(b) Linear structure (with branches)
(c) Network structure (a small amount of cross-links between molecular chains)
(d) Body structure (a large number of cross-links between molecular chains)
Two different structures, Showing two opposite properties. Because polymers with linear structures (including branched structures) have independent molecules, they are elastic and plastic, can be dissolved in solvents, can be melted when heated, and have low hardness and brittleness. Since there are no independent macromolecules in the body structure polymer, it has no elasticity and plasticity, cannot dissolve and melt, can only swell, and has greater hardness and brittleness. Plastics have two kinds of polymer structures. Thermoplastics are made of linear polymers, and thermosetting plastics are made of body-shaped polymers.
Compared with other materials, plastics have the following characteristics:
〈1〉 Resistant to chemical attack
〈2〉 Glossy, partially transparent or translucent
〈3〉 Mostly good insulators
〈4〉 Light weight and strong
〈5〉 Easy to process, can be mass produced, and cheap
〈6〉 Widely used, multi-functional, easy to color, and partially resistant to high temperatures
Plastics are also divided into general-purpose plastics and engineering plastics, which are mainly defined by their wide range of uses, such as PE , PP is cheap and can be produced on many different types of machines. Engineering plastics are more expensive, but their raw material stability and physical properties are much better. Generally speaking, they have both rigidity and toughness. Table 1.1 is a comparison table of plastic raw materials. Items 1 to 8 are general-purpose plastics, and items 9 and 10 are in between. Generally speaking, PP, HDPE, LDPE, PVC and PS are the five most commonly used plastics.
Table 1.1 Comparison table of commonly used plastic raw materials
Scientific name
English abbreviation
Chinese scientific name
Common name
Polypropylene
PP
Polypropylene
High Density Polyethylene
HDPE
High Density Polyethylene
Hard Soft Polyethylene
Low Density Polyethylene
LDPE
Low Density Polyethylene
Linear Low Density Polyethylene
LLDPE
Linear low density polyethylene
Polyvinyl Chloride
PVC
Polyvinyl chloride
General Purpose Polystyrene
GPPS
General grade polystyrene
Hard glue
Expansible Polystyrene
p>
EPS
Expanded polystyrene
Styrofoam
High Impact Polystyrene
HIPS
Impact-resistant polystyrene
Impact-resistant hard rubber
Styrene-Acrylonitrile Copolymers
AS, SAN
Benzene Ethylene-Acrylonitrile-Styrene Copolymers
Transparent Styrene Glue
Acrylonitrile-Butadiene-Styrene Copolymers
ABS
Acrylonitrile- Butadiene-styrene *** polymer
Super unbreakable glue
Polymethyl Methacrylate
PMMA
Polymethacrylic acid Ester
Acrylic
Ethylene-Vinyl AcetateCopolymers
EVA
Ethylene-Vinyl Acetate Copolymer
Rubber
Polyethylene Terephthalate
PET
Polyethylene terephthalate
Polyester
Polybutylene Terephthalate
PBT
Polybutylene Terephthalate
Polyamide(Nylon 6.66)
PA
Polyamide nylon
Polycarbonates
PC
Polycarbonate resin
Bulletproof glue
Polyacetal
POM
Polyacetal resin
Saigon, Duuraco
Polyphenyleneoxide
PPO
Polyphenylenesul
Noryl
Polyphenylenesul
fide
PPS
Polyphenylene sulfide
Polyurethanes
PU
Polyurethane
[Edit this paragraph] Characteristics of plastics
Plastics mainly have the following characteristics:
① Most plastics are lightweight, chemically stable, and will not rust; ② Good impact resistance; ③ Good transparency and wear resistance; ④ Good insulation and low thermal conductivity; ⑤ Good general formability and colorability, low processing cost; ⑥ Most plastics have poor heat resistance and thermal expansion rate Large and easy to burn; ⑦Poor dimensional stability and easy to deform; ⑧Most plastics have poor low temperature resistance and become brittle at low temperatures; ⑨Easy to age; ⑩Some plastics are easily soluble in solvents.
Plastics can be divided into two categories: thermosets and thermoplastics. The former cannot be reshaped and used, while the latter can be produced repeatedly.
There are basically two types of plastic polymer structures: the first is a linear structure, and polymer compounds with this structure are called linear polymer compounds; the second is a body structure, which has Polymer compounds with this structure are called body-type polymer compounds. Some polymers have branched chains, called branched polymers, and have a linear structure. Although some polymers have cross-links between molecules, there are few cross-links, which is called a network structure and is a body structure.
Two different structures, showing two opposite performances. Because polymers with linear structures (including branched structures) have independent molecules, they are elastic and plastic, can be dissolved in solvents, can be melted when heated, and have low hardness and brittleness. Since there are no independent macromolecules in the body structure polymer, it has no elasticity and plasticity, cannot dissolve and melt, can only swell, and has greater hardness and brittleness. Plastics have two kinds of polymer structures. Thermoplastics are made of linear polymers, and thermosetting plastics are made of body-shaped polymers.