Thermal spray ceramic powder mainly refers to the oxide, carbide, nitride, boride and silicide powder, commonly used thermal spray ceramic powder mainly Al2O3, ZrO2, TiO2, WC, Cr2O3 and so on. Ceramic coating has outstanding advantages such as high hardness, wear resistance and heat resistance. The use of plasma spraying can solve the problem of high melting point of the material, almost all ceramic materials can be sprayed, and certain ceramic coatings can be obtained with flame spraying.
2, thermal spraying plastics
In the metal and non-metallic surface spraying plastic, with beautiful, corrosion-resistant properties. If you add a hard phase in the plastic powder can also make the coating has a certain degree of wear resistance. Polyethylene coating can withstand temperatures of 250 ℃, at room temperature resistance to dilute sulfuric acid, dilute hydrochloric acid corrosion, and has a concentrated hydrochloric acid, hydrofluoric acid and phosphoric acid corrosion resistance, but also insulating and self-lubricating properties. Commonly used thermal spray plastics and nylon, epoxy resin.
Thermal spraying technology is a new technology to strengthen and protect the surface of the material, which occupies an important position in the surface modification technology. The technology began in China in the 1950s, the end of the 70s to form a climate. At present, no matter in the equipment, materials, technology, scientific research and other aspects of the rapid development and improvement, has become an important part of the surface technology. The development trend is: equipment (spray gun) to high-energy, high enthalpy, high speed development; materials to the series, standardization, commercialization direction to ensure that multi-functional high-quality coating needs; process to the direction of mechanization, automation, such as computer control, robotic operation, etc.. Nowadays, thermal spray technology has been widely used in various fields of the national economy, and the promotion and application of broad prospects.
I, the new development of thermal spray equipment
Recently, China has accelerated the pace of development and production of equipment, has formed a complete development and production system, there are more than 20 units engaged in the development and production of thermal spray equipment to produce various types of oxy-acetylene flame spraying equipment, spray fusion equipment; new arc spraying equipment; complete sets of plasma spraying equipment, spray welding equipment; various types of special machine tools; thermal spraying air purification equipment. Specialized machine tools; thermal spraying air purification equipment, pre-treatment and post-processing equipment. Single machine varieties have reached more than 100, the development and production of these products to ensure that the development of thermal spray technology, more prominent are:
1, high-speed flame spraying device at present, the introduction of high-speed flame spraying device from abroad (HVOF), (HVAF), and supersonic plasma spraying equipment, which is characterized by the high speed of particles, high bonding strength of the coating and the substrate, low porosity, the equipment has been used in aerospace, aviation, metallurgy, and other industries, and the development of thermal spraying technology. These equipments have been playing an important role in aerospace, aviation, metallurgy, chemical industry and electric power industry. However, the above imported equipment is expensive and the fuel (propane, propylene) is not easy to popularize, for the above situation, combined with China's national conditions, Sichuan Great Wall Spraying Technology Research Institute has successfully developed a high-speed spraying gun with oxyacetylene flame as the heat source. Due to the limitations of acetylene pressure, although the particle flight speed does not reach supersonic speed, but it is more than the conventional oxyacetylene flame powder spraying flight speed increased by 4 to 5 times, than the atmospheric pressure plasma spraying also increased by 1 to 2 times, can be sprayed metal and alloy powder materials such as Al2O3-TiO2-Co-WC and polyethylene, nylon and other thermoplastic powder materials. In addition, Xi'an Jiaotong University and other units have successfully developed high-speed flame (HVOF) spraying device, and began to apply.
2, high-speed arc spraying device Due to the arc spraying has a combination of high strength, low energy consumption, low cost and other advantages, so in recent years this equipment in the country more and more attention and actively used, especially in the steel structural parts of the large-area long-lasting protection works and power station boiler pipe thermal corrosion has played an important role. On the basis of ordinary arc spraying, the National Industry-University-Research Equipment Engineering Center Armored Corps College of Engineering, Xi'an Second Artillery College of Engineering has recently developed a successful high-speed arc spraying gun, the air velocity is up to 600m/s or more, and its coating bonding strength, porosity, and many other indicators are superior to the ordinary arc spraying, and is now being further promoted and applied.
3, oxygen - acetylene flame metal powder spraying device Oxygen - acetylene flame metal powder spraying technology is now widely used in the domestic promotion of a wide range of applications, almost all the large enterprises have it as a means of repairing the old and recycling. Shanghai, Jiangsu, Wuhan and Sichuan have developed and produced a variety of models of spraying, spray welding gun, has been widely for the spraying unit. Shanghai Welding and Cutting Spraying Machinery Factory recently improved on the basis of the original QHT-7/h flame gun, using two sets of nozzles, the use of two kinds of heat sources: namely, oxygen? Acetylene flame and oxygen? Liquefied petroleum gas (domestic bottled). The use of bottled liquefied petroleum gas as a combustible gas can greatly reduce costs and bring greater convenience to the spraying operation.
4, gas explosion spraying device Aerospace Corporation Sixty-two One Research Institute, from the 60s began to develop, has now placed a complete set of gas explosion spraying device for aerospace, aviation, and other military sectors sprayed a lot of high-density high-quality coatings, the equipment has reached or close to the level of similar foreign products. Beijing Great Wall Titanium Company in recent years, in cooperation with Ukraine, the establishment of a Sino-foreign joint venture Beijing Titanium New Materials Co., Ltd. introduced the Ukrainian explosive spraying equipment manufacturing technology, and is now able to produce computer-controlled three-dimensional walking mechanism of the explosive spraying equipment, in addition to domestic users, has been sold to the United States and Taiwan and other regions.
5, oxygen - acetylene flame plastic powder coating device In recent years, the use of oxygen - acetylene flame, with boiling powder feeding method, through a special spray gun spraying plastic powder, you can get a flat and smooth plastic coating. This for large workpieces, various tanks, pipeline coating plastic coating provides a new method. To this end, Shenyang Thermal Spraying Plant, Wuhan Institute of Materials Protection, Armored Corps Engineering Institute have successfully developed different types of flame plastic powder spraying device, and a large area construction, received good results. Among them, Wuhan Institute of Materials Protection successfully developed FSP-II type plastic powder flame spray gun performance reached the level of UTP company I-SPRAY-JET spray gun.
6, new plasma spray gun Tsinghua University and other units developed a successful QZNI high-energy bore plasma spray gun, the gun power up to 75kW, thermal efficiency, average enthalpy of the plasma jet, jet temperature, gun power and powder deposition rate have reached the level of the Metco large bore spray gun. Recently, Beijing Entropy Cole Applied Technology Research Institute successfully developed BT-G1, BT-G2, BT-G3 type new plasma spray gun, and BT-NI type large bore spray gun, and also successfully developed BT-F1 type double cylinder ultra-fine powder feeder and physical cooling system, so that the level of domestic plasma spraying equipment to a new level, and shorten the gap with the level of foreign equipment.
7
7, new sand blasting equipment Beijing, Shanghai and other places have recently developed a small recyclable sand blasting equipment and large-scale environmentally friendly sand blasting equipment, greatly improving the labor conditions, reduce environmental pollution, to promote the development of China's thermal spraying technology has played a positive role.
Second, the new development of thermal spray materials
People say that thermal spray materials are thermal spray "food". Spray material performance, quality, variety is an important measure of the quality of the coating of one of the levels, but also affects the economic benefits of the key factors. China's thermal spray materials, although a late start, but into the 70s since the rapid development, there are now more than 40 manufacturers to produce nearly 100 varieties, basically to meet domestic needs. These research and production units to develop and produce thermal spray materials can be broadly divided into (recent new varieties):
1, powder materials Beijing General Research Institute of Mining and Metallurgy developed successful yttrium oxide partially stabilized zirconia thermal gap coating materials, as well as resistance to high-temperature oxidation of nickel-chromium-aluminum-cobalt yttrium oxide substrate material has been widely used in aircraft engines; Chongqing Instrumentation Materials Research Institute developed a successful air Zirconia material sprayed thermal barrier coating, its indicators also meet the requirements; Beijing General Research Institute of Mining and Metallurgy successfully developed nickel-chromium - chromium carbide composite powder materials, has been in many power plant boiler water-cooled wall pipe as a high-temperature corrosion-resistant wear-resistant coatings, the application of the effect is good; Shenyang Wheel Factory successfully developed alumina, alumina - titanium oxide powder has been widely used in textile machinery and metallurgical equipment, the factory successfully developed the CrB2 powder developed by the plant in continuous casting machine rolls and furnace bottom rolls on the spray application has begun to show results; Beijing Iron and Steel Research Institute using the self-propagating method of development of XTiC + yCr3C2 + zNi composite ceramic materials for plasma spraying, coating hardness of up to 54HRC, can withstand high temperatures of 800 ° C; Zigong Cemented Carbide Factory production of Co-WC alloy powders, has been widely promoted and used; Sichuan and other places Successful development of molybdenum-based alloy powder, has been successfully applied to automotive synchronizer ring coating.
2, wire material Beijing Institute of Technology successfully developed and mass production of wear-resistant and corrosion-resistant thermal spray metal powder core wire containing rare earth elements, the more typical 7Cr13-type, 3Cr13-type, low carbon martensite type, suitable for electric arc and flame spraying, the average bonding strength of the coating for the 50MPa, the porosity is less than 7%, the coating of the average hardness of 40 ~ 50HRC; Beijing General Research Institute of Nonferrous Metals has recently developed a coating material for the thermal spraying of the metal powder core, the average hardness of 40 ~ 50HRC. Beijing General Research Institute of Nonferrous Metals recently developed a successful Ni-Al alloy wire for arc spraying priming, as well as for high temperature corrosion and abrasive wear resistant arc spraying with Ni-Cr alloy wire (equivalent to the U.S. TAFA's 45CT); Armored Corps Engineering Institute developed SL30 type Ni-Cr alloy wire coatings + organic metal composite coatings, successfully replacing the U.S. TAFA 45CT; Shenyang University of Technology successfully developed a new type of Ni-Cr alloy wire coating + organic metal composite coatings, successfully replacing the U.S. TAFA's 45CT. ; Shenyang University of Technology developed a successful iron-based alloy arc spraying priming wire, instead of aluminum bronze wire; Shanghai, Beijing, Zhejiang, Sichuan and other places to develop and produce Fe-Cr-Al wire, Al-Mg alloy wire, Zn-Al alloy wire, as well as pasteurized alloy wire, etc..
3, plastic powder in the development of polyethylene, polypropylene, nylon and other powder for oxyacetylene flame spraying on the basis of the recent units have successfully developed a chlorinated polyether, modified fluorine plastic powder, to broaden the scope of application of plastic coatings have been used in anti-corrosion projects.
4, bar materials The introduction of the United States of America's ceramic bar coating materials, has been successfully applied in the textile machinery, the domestic trial of ceramic bars and flexible ceramic wire has been introduced, will soon be introduced to the market. The above materials, are recently appeared in the country's new species, the development and production of these materials, for the development of China's thermal spray technology to create favorable conditions.
Three, the new development of thermal spray technology
Thermal spraying technology has been widely used in the country, the trend of development in recent years and features are:
(1) large-area, long-lasting protection technology has been widely used for long-term exposure to the outdoor atmosphere of the iron and steel structural components, the use of spraying aluminum, zinc and its alloy coatings instead of the traditional method of painting, the implementation of cathodic protection, the use of cathodic protection. For long-term exposure in the outdoor atmosphere of iron and steel structural parts, the use of spraying aluminum, zinc and its alloy coating, instead of the traditional method of painting, the implementation of cathodic protection for long-lasting atmospheric anticorrosion, in recent years, has been rapid development. Such as television towers, bridges, highway facilities, water gates, microwave towers, high-voltage transmission towers, underground cable supports, buoys, shafts and other large-scale projects, have adopted the spraying of aluminum, zinc and its alloys for corrosion protection. At present, there are dozens of professional spraying factory engaged in this work, spraying area of more than a few million square meters per year. This technology is not only a large number of domestic popularization and application, but also in foreign aid projects have been better promoted and applied.
(2) the use of thermal spray technology to repair and strengthen large-scale key equipment and imported parts and components localization In recent years, there have been many examples of successful applications in this regard, such as: one-meter seven mills, high-speed fan rotor, large-scale extruder plunger, large gears, electrode extrusion molding nozzle, high-power automotive crankshafts and so on. These efforts, one is to solve the urgent need for production; second is to save a lot of foreign exchange.
(3) the application of supersonic flame spraying technology With the development and improvement of China's thermal spraying technology, the quality of the spray layer requirements are increasingly high. In recent years, the United States and other countries to develop a high-speed gas (HVOF) method is a new process for the preparation of high-quality coating method. Due to the supersonic flame spraying method has many advantages, at present the domestic has been introduced from abroad nearly a dozen equipment, in various industrial sectors play an important role.
(4) gas flame spraying technology is further applied to the spraying technology due to the particle flight speed of up to 800m/s or more, the coating and the substrate bonding strength of up to 100MPa or more, the porosity <1%, in some areas of application, better than other spraying methods. At present, more than 10 units have been installed in China.
(5) rapid development of oxyacetylene flame plastic powder coating technology As mentioned earlier, in recent years, there are a number of domestic production and manufacturing of oxyacetylene flame plastic powder coating equipment, using the technology, has been in the chemical tanks, pipelines, ceramic industry lute mud machine plate and frame, printing and dyeing industry guide rolls, the coal industry, the cast iron wheels of the belt conveyor, the petroleum industry, the injection of polymerization equipment, as well as the surface decoration and so on. It has been well used to make up for the lack of electric spraying. For the application of plastic coating, opened up a new way.
(6) thermal spray technology in the chemical corrosion engineering applications Corrosion is a mechanical component by the chemical or electrochemical effect of the surrounding media and one of the main reasons for failure. It not only makes a large number of metal materials subject to loss, thus causing the loss of production stoppage is more difficult to estimate, so people pay special attention to chemical anti-corrosion work. Thermal spray layer applied to corrosive media, especially strong media corrosion, before so failed to break through, the main reason is that the sealing agent failed to solve. As we all know, the spraying layer is the existence of pores, if not sealing processing, a variety of acids, alkalis, organic media will be immersed in the pores, so that the coating off, affecting the effect of anti-corrosion. According to the requirements of anticorrosion engineering, recently China has successfully developed polyester type, organic polymer type, resin type, plastic type, adhesive type and so on dozens of models of sealing agent, suitable for acid, alkali, salt and organic corrosive environments, and its use temperature of 80 ~ 350 ℃. Adopting ceramic coating, oxide coating or metal or alloy coating, and selecting appropriate sealing agent according to different media, it has been applied in many chemical corrosive media with good effect. This series of sealing agent has been patented and won the National Invention Award. These sealing agent research success, so that the thermal spraying technology in the chemical corrosion engineering application has made new progress.
(7) laser remelting technology began to apply In recent years, high-frequency induction remelting, vacuum induction remelting is only applied to a certain extent. Laser remelting technology in previous years have done a small area test, not widely used. Recently, Tsinghua University has been laser remelting technology for the production of valves, Shanghai Second Textile Machinery Factory has been laser remelting technology used in textile machinery.
(8) thermal spray technology in construction and decoration of health care has also been applied in recent years in Sichuan, Shanghai, Shenyang, Yunnan and other places using thermal spray technology sprayed a variety of statues, ornaments, large walls and other good results, such as Shenyang City, the international shopping mall of the peacock large-scale mural on the use of thermal spray technology. With the development and improvement of thermal spraying technology, the technology has penetrated into other fields, such as biological fields with thermal spraying methods, manufacturing artificial bones, has more than 200 cases of clinical, the effect is very good. In addition, with the thermal spraying method of artificial teeth, has also been the initial application.
Four, further promote the application of thermal spray technology is of great significance
Wear and corrosion is the main cause of failure of materials and components. According to the relevant data reports, developed countries due to wear and corrosion caused by the loss of about 3% to 5% of the total output value of the national economy, in 1993, China's losses due to corrosion amounted to more than 100 billion yuan, an average of 300 million yuan per day. 1994 China's total output value of the national economy was 438 billion yuan, if the loss of 4% is more than 170 billion yuan, and the "Eighth Five-Year Plan" during the popularization of thermal spraying technology direct economic benefits of about 3.5 billion yuan. The direct economic benefits of promoting the application of thermal spraying technology during the "Eighth Five-Year Plan" period is about 3.5 billion yuan. With the further improvement of material performance requirements, the thermal spraying equipment, process, materials and other more in-depth research and exploration. Data show that the thermal spray process as an excellent surface modification technology has a broad development prospects, and further extensive and in-depth promotion and application of the technology is of great significance.
Introduction of plastics
[1] Plastics for the synthesis of polymer compounds {polymers (polymer)}, also known as polymers or macromolecules (macromolecules), but also commonly referred to as plastics or resins (resin), can be free to change the shape of the style. It is a material that is polymerized by synthesis or condensation reaction using monomer raw materials, and consists of synthetic resins and additives such as fillers, plasticizers, stabilizers, lubricants, and colorants. The term resin [2] was originally named after the lipids secreted by plants and animals, such as rosin and wormwood, etc. Currently, resin refers to polymers that have not yet been mixed with various additives. Resin accounts for about 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, containing no or few additives, such as plexiglass, polystyrene and so on. The so-called plastic, in fact, it is one of the synthetic resins, the shape is similar to the natural resin in the pine resin, but because of the chemical power to synthesize, and is called plastic.
According to the definition of the American Society for Testing and Materials (ASTM), plastic is a material with high molecular weight organic substances as its main component, which presents a solid shape when processed, and can be modeled by flow during manufacturing and processing.
Therefore, we can get the following understanding after this explanation:
● It is a high molecular weight organic compound
● It can exist in many types of forms such as liquids, solids, colloidal solutions, etc.
● It can be molded
● There are many types of plastics because of the different composition of different monomers
● Wide range of uses. Figure 1.1 shows the process of plastic production.
Figure 1.1 Plastic production process
Plastic can be distinguished into thermosetting and thermoplastic two categories, the former can not be reshaped to use, the latter can be repeated again and again to produce. 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 are called body polymer compounds. Some macromolecules with branched chains, called branched polymers, belong to the linear structure. Some macromolecules have intermolecular cross-links, but fewer cross-links, known as reticulation, belonging to the body-type structure.
The molecular structure of polymers is classified as follows:
(a) Linear structure
(b) Linear structure (with branched chains)
(c) Reticulated structure (with a small number of cross-links between the molecular chains)
(d) Bulk structure (with a large number of cross-links between the molecular chains)
The two different types of structures exhibit two opposite properties. Linear structure (including branched chain structure) polymer due to the existence of independent molecules, so there is elasticity, plasticity, soluble in solvents, heating can melt, hardness and brittleness of the characteristics of the smaller. Body structure polymers due to the existence of no independent macromolecules, so there is no elasticity and plasticity, can not be dissolved and melted, can only be dissolved, hardness and brittleness. Plastics are two structures of polymers have, made of linear polymers are thermoplastics, made of body polymers are thermosetting plastics.
Plastics have the following characteristics compared with other materials:
〈1〉 Chemical resistance
〈2〉 Glossy, partly transparent or translucent
〈3〉 Mostly good insulators
〈4〉 Lightweight and strong
〈5〉 Easy to process, mass-produced, and cheap
〈6〉 Versatile, useful, and easy to use. Wide range of uses, utility, easy to color, part of the high temperature resistance
Plastics are also divided into general-purpose plastics and engineering plastics, mainly defined by the wide range of uses, such as PE, PP, cheap, can be used in a variety of different types of machine production. Engineering plastics are more expensive, but the stability of raw materials and physical properties are much better, in general, it has both rigidity and toughness of the two characteristics. Table 1.1 for the plastic raw materials comparison table, 1 to 8 items for the general use of plastics, the 9th, 10th between the two. Generally referred to as PP, HDPE, LDPE, PVC and PS for the five major ubiquitous plastics.
Table 1.1 Comparison Table of Common Plastic Materials
Scientific Name
English Abbreviation
Chinese Name
Common Name
Polypropylene
PP
Polypropylene
High Density Polyethylene <
HDPE
High Density Polyethylene
Rigid Soft Gel
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 Purpose Polystyrene
Hard Gel
Expansible Polystyrene
EPS
Expansible Polystyrene
Foam Gel
High Impact Polystyrene
HIPS
Impact Polystyrene
Impact Resistant Hard Gel
Styrene-Acrylonitrile Copolymers
AS,SAN
Styrene-Acrylonitrile*** Polymer
Transparent Vigorous Adhesive
Acrylonitrile-Butadiene- Styrene Copolymers
ABS
Acrylonitrile-Butadiene-Styrene*** Polymer
Superfast Adhesive
Polymethyl Methacrylate
PMMA
Polymethyl Methacrylate
Acrylic
Ethylene-Vinyl AcetateCopolymers
EVA
Ethylene-Vinyl Acetate*** Polymer
Rubber Adhesive
Polyethylene Terephthalate
PET
Polyethylene Terephthalate
Polyester
Polybutylene Terephthalate
PBT
Polybutyl Terephthalate
Polyamide (Nylon 6.66)
PA )
PA
Polyamide (Nylon 6.66)
Polyamide (Nylon 6.66)
Polycarbonates
PC
Polycarbonates
Polycarbonate
Bullet-proof Adhesive
Polyacetal
POM
Polyacetal resins
Race Steel, Ripstop Steel
PolyphenyleneoxidePPO
Polyphenylene Oxide
Noryl
Polyphenylenesulfide
PPS
Polyphenylene Sulfide
Polyurethanes
PU
Polyurethanes
[edit]Characteristics of plastics
Plastics mainly have the following characteristics:
① Most plastics are lightweight, chemically stable, and will not corrode; ② good impact resistance; ③ good transparency and abrasion resistance; ④ good insulation, low thermal conductivity; ⑤ good molding, coloring, low processing costs; ⑥ most plastics have poor heat resistance. Most plastics have poor heat resistance, large thermal expansion, easy to burn; ⑦ poor dimensional stability, easy to deform; ⑧ most plastics have poor low-temperature resistance, brittle at low temperatures; ⑨ easy to age; ⑩ some plastics are soluble in solvents.
Plastics can be distinguished as thermosetting and thermoplastic two categories, the former can not be reshaped to use, the latter can be repeated again and again repeated production.
The structure of plastic polymers are basically two types: the first is a linear structure, with this structure of polymer compounds known as linear polymer compounds; the second is the structure of the body, with this structure of polymer compounds known as body polymer compounds. Some macromolecules with branched chains, called branched polymers, belong to the linear structure. Some macromolecules, although intermolecular crosslinking, but less crosslinking, known as the mesh structure, belonging to the body structure.
Two different structures, showing two opposite properties. Linear structure (including branched structure) polymers due to the existence of independent molecules, so there is elasticity, plasticity, in the solvent can be dissolved, heating can melt, hardness and brittleness of the characteristics of the smaller. Body structure polymers due to the existence of no independent macromolecules, so there is no elasticity and plasticity, can not be dissolved and melted, can only be dissolved, hardness and brittleness. Plastics are two structures of polymers are available, made of linear polymers are thermoplastics, made of body type polymers are thermosetting plastics.