Gas-dynamic spraying of metal: purpose, purpose, types of technology. Advantages and disadvantages of the method. Application area. Equipment and features of the use of cold spraying.
Gas-dynamic spraying of metal is carried out in order to give the surfaces of metal and non-metal products the necessary properties. This can be an increase in electrical and thermal conductivity, strength, protection against the effects of corrosion processes, restoration of geometric dimensions, etc. At the same time, depending on the specific task, depending on the metal of the product, the necessary equipment, consumables and spraying technology are selected. Most often, surfaces are subject to metallization, while the applied coating has high adhesion with the material on which it is applied, and the product is mechanically strong. Pure metal powders or mixtures can be deposited, in which, in addition to the metal component, ceramic powder is introduced in certain quantities. This significantly reduces the cost of powder coating technology and does not affect its properties.
The essence of the method of cold gas-dynamic spraying is the application and fixing on the surface of a product or part of solid particles of metal or a mixture of materials ranging in size from 0.01 to 50 microns, accelerated to the required speed in air, nitrogen or helium. Such material is called powder. These are particles of aluminum, tin, nickel, babbits of different brands, a mixture of aluminum powder with zinc. The medium with which the material is moved can be cold or heated to a temperature not exceeding 700 °C.
Upon contact with the surface of the product, a transformation of the plastic type occurs, and the energy of the kinematic type passes into adhesive and thermal, which contributes to the production of a durable surface layer of the metal. The powder can be applied not only to metal surfaces, but also to those made of concrete, glass, ceramics, stone, which greatly expands the scope of the method for creating surfaces with special properties.
Depending on the pressure, the following types of cold gas-dynamic spraying are distinguished:
- high;
- low.
In the first case, helium and nitrogen are used as a working medium that moves powder material ranging in size from 5 to 50 microns. Metal particles, if they move, have a pressure of more than 15 atm. In the second case, compressed air is used, which is supplied under pressure not exceeding 10 atm. These types also differ in such indicators as heating power and consumption of the working medium.
The spraying steps are as follows:
- preparation of the surface of the product for spraying by mechanical or abrasive means;
- heating the working medium (air, nitrogen, helium) to the temperature set in the technological process;
- supply of heated gas to the nozzle of the equipment together with the powder under the required pressure.
As a result, the powder is accelerated in the flow to supersonic speeds and collides with the surface of the part or product. There is a deposition of a metal layer with a thickness, the value of which depends on the heating temperature of the supplied gas and pressure.
The preparation of the surface of the product by an abrasive method is performed using the equipment itself for applying gas-dynamic spraying by simply changing the mode parameters.
The scope of this type of spraying is quite extensive. The method is used to seal leaks in tanks and pipelines, repair parts and castings made of light alloys, apply electrically conductive, anti-corrosion and anti-friction coatings, eliminate mechanical damage, restore seats in bearings.
The main advantages of the method
The advantages of the technology include:- performance of work under any climatic conditions (pressure, temperature, humidity);
- the possibility of using equipment of a stationary and portable type, which in the latter case allows you to carry out work at the place of their implementation;
- the possibility of applying a coating to local areas (defective places);
- the ability to create layers with different properties;
- the possibility of creating a layer of the required thickness or different in thickness in multilayer coatings;
- the process does not affect the structure of the product, which is sprayed, which is an important advantage;
- safety;
- environmental friendliness.
The disadvantage of this type of spraying is only one fact. Layers can be applied to ductile metals such as copper, zinc, aluminium, nickel and their alloys.
Manufacturers from different countries produce stationary and portable equipment for manual and automated coating of different capacities on different metals.
Applied equipment
The apparatus for gas-dynamic metal spraying consists of the following main parts:- powder containers;
- systems for supplying the working medium, including a cylinder for compressed gas and all the necessary accessories for it;
- nozzles (as a rule, there are several of them, they are of different configurations and are used for different spraying modes);
- control panel.
The process of repairing a part by gas-dynamic spraying is shown in the video:
In fact, it is a more advanced version of the gas-thermal method of restoring various metal parts and surfaces that has long been proven. Cold Spray or simply CGN significantly expands the possibilities of the "hot" method of processing products.
Today, it is undoubtedly the most advanced technology for the recovery and protection of materials, which has become widespread in both the industrial sector and the civil sector.
The principle of action, the pros and cons of CGN
It has two main differences from the gas-thermal method of restoration. Firstly, the deposition of a protective or restorative coating occurs at a low temperature not exceeding 150 °C, which in turn does not cause stress in the workpieces and their deformation. Secondly, the "cold" technology allows you to create a layer of adjustable thickness and within precisely defined boundaries. We will talk about other pros and cons a little later, but for now, about the authors of the method and how it works.
Its developer is "Obninsk powder coating center"(Russia). The equipment they produce is called DIMET ®. It is certified according to the GOST R system and is protected by patents in Russia, the USA, Canada and other countries. The technology is based on the principle of supersonic impact of the smallest particles of low-melting and other materials on the treated surface. Basically, these are polymers or alloys of carbides with metals with a particle size of 0.01-0.5 microns. Mixing with gas, they are fed to the product at a speed of 500-1000 m/s. .jpg)
Depending on the composition of the consumable material (powder) and changing the modes of its application, it is possible to obtain a homogeneous or composite coating with a solid or porous structure and its own functional task. This can be: restoring the geometry of the product, strengthening and protecting the metal from corrosion, increasing the thermal and electrical conductivity of the material, as well as the formation of a wear-resistant coating that can withstand the effects of chemically active environments, high thermal loads, etc.
By the way, Obninsk engineers have already developed several modifications of DIMET ® units. Given the wide demand for this equipment, both manual and automated cold gas-dynamic spraying machines are now mass-produced, which allows them to be used in industry, the oil and gas industry, as well as in small businesses for processing small parts. Moreover, there is nothing particularly complicated in the technology itself. For the operation of the complex (in addition to the material for spraying), only compressed air is needed (supplied at a pressure of 0.6-1.0 MPa and a flow rate of 0.3-0.4 m3/min.) And a 220 V power supply.
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Now more about the advantages and disadvantages of the method. Firstly, in contrast to the gas-thermal method, CGN can be effectively used at normal pressure, in any temperature range and humidity level. Secondly, it is environmentally absolutely safe. Thirdly, due to the high speed, it can also be used for abrasive surface cleaning. Well, the only drawback of the technology is the possibility of applying coatings only from relatively ductile metals, such as copper, aluminum, zinc, nickel, etc.
Scope of CGN
I would like to dwell in more detail on the areas of application of the technology of cold gas-dynamic spraying with powder materials in order to clearly show how much it is in demand today.
Elimination of defects, restoration of surfaces and sealing
All this is a job that even small businesses can do. For example, in small workshops it is possible to repair parts made of light alloys (parts of an automotive structure, for example), primarily aluminum and aluminum-magnesium. Moreover, defects that have arisen both in the production process and during operation are easily eliminated. And the absence of strong heating and the low energy of the method make it possible to repair even thin-walled products. .jpg)
CGN is also excellent for restoring worn surfaces. For example, such a labor-intensive process as “building up” metal in bearing seats can now be carried out even by small enterprises, not to mention the restoration of sealing (when the use of liquid sealants is impossible) in pipelines, heat exchangers or vessels for working gases, liquids.
It is very effective in the repair of complex products, where accurate restoration of geometric parameters is required, elimination of hidden defects, but at the same time with the preservation of all operational characteristics, as well as the presentation. That is why this method is actively used in the military-industrial complex, the railway and aviation industries, agriculture, gas transmission, etc.
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You can not do without this technology in the creation of contact pads. Due to the possibility of easy coating on any metal, ceramic and glass surfaces, CGN is also used in the production of electrical products. For example, in the processes of copper plating, the creation of power current-carrying networks, the application of current leads, the manufacture of sublayers for soldering, etc.
Anti-corrosion treatment and elimination of deep defects
Spraying the so-called anti-friction coating is a highly effective way to get rid of local damage (deep chips, scuffs, scratches). This avoids the procedure of complete refilling or even replacement of the product, which, of course, is not economically viable.
And in anti-corrosion treatment and protection against high-temperature corrosion of various communications, this method has no equal at all. By the way, various modifications of equipment DIMET ® provide high-quality processing of the inner surface of pipes with a diameter of 100 mm and a length of up to 12 m.
Candidates of Physical and Mathematical Sciences O. KLYUEV and A. KASHIRIN.
When the first metal tools of labor first appeared, it turned out that, being solid and durable, they often deteriorated under the influence of moisture. Time passed, people created mechanisms and machines, and the more perfect they became, the more difficult conditions their metal parts had to work. Vibrations and alternating loads, huge temperatures, radiation exposure, aggressive chemical environments - this is not a complete list of "tests" to which they are subjected. Over time, people have learned to protect the metal from corrosion, wear and other phenomena that reduce the life of parts. In fact, there are two approaches to providing such protection: either alloying elements are added to the base metal, which give the alloy the desired properties, or a protective coating is applied to the surface. The operating conditions of machine parts dictate the properties that coatings must have. The technologies for their application are diverse: there are common and relatively simple, there are very thin ones that allow you to create coatings with unique properties. And restless engineers continue to invent new coatings and come up with ways to get them. The fate of these inventions can become happy if the coating is much superior to its predecessors in terms of useful properties or if the technology provides a significant economic effect. In the development of physicists from Obninsk, both of these conditions were combined.
Metal particles flying at great speed upon impact with the substrate are welded to it, and ceramic particles compact the coating (a); stuck ceramic particles are visible on the microsection of the metal layer (b).
Scheme (top) and general view (bottom) of the apparatus for spraying metal coatings.
By means of the device it is possible to apply coverings in any rooms and even in field conditions.
A zone of negative pressure arises behind the critical section of the nozzle, and the powder is sucked in here. Thanks to this phenomenon, it was possible to simplify the design of the feeder.
Defects in body parts (left) and the result of spraying (right): a - a crack in an automatic transmission; b - a cavity in the cylinder head.
Coated with a layer of copper or aluminum, tools can be used in fire hazardous areas: when they hit metal objects, they do not spark.
TEMPERATURE PLUS SPEED
Of the methods of surface metallization in modern technology, galvanic deposition and immersion in a melt are most often used. Vacuum deposition, vapor phase deposition, etc. are used less frequently. The closest thing to the development of Obninsk physicists is gas-thermal metallization, when the deposited metal is melted, sprayed into tiny drops and transferred to the substrate by a gas jet.
Metal is melted with gas burners, electric arc, low-temperature plasma, inductors and even explosives. Accordingly, metallization methods are called flame spraying, electric arc and high-frequency metallization, plasma and detonation-gas spraying.
In the process of flame spraying, a metal rod, wire or powder is melted and sprayed in the flame of a burner operating on a mixture of oxygen and combustible gas. In electric arc metallization, the material is melted by an electric arc. In both cases, metal droplets are moved to the sprayed substrate by air flow. In plasma spraying, a plasma jet is used to heat and spray the material, which is formed by plasmatrons of various designs. Detonation-gas spraying occurs as a result of an explosion that accelerates metal particles to tremendous speeds.
In all cases, the particles of the sprayed material receive two types of energy: thermal - from the heating source and kinetic - from the gas flow. Both of these types of energy are involved in the formation of the coating and determine its properties and structure. The kinetic energy of particles (with the exception of the detonation-gas method) is low compared to the thermal one, and the nature of their connection with the substrate and between themselves is determined by thermal processes: melting, crystallization, diffusion, phase transformations, etc. Coatings are usually characterized by good adhesion to the substrate (adhesion) and, unfortunately, low uniformity, since the spread of parameters over the cross section of the gas flow is large.
Coatings, which are created by gas-thermal methods, have a number of disadvantages. These include, first of all, high porosity, unless, of course, the goal is to specifically make the coating porous, as in some parts of radio tubes. In addition, due to the rapid cooling of the metal on the surface of the substrate, high internal stresses arise in the coating. The workpiece inevitably heats up, and if it has a complex shape, then it can be "led". Finally, the use of combustible gases and high temperatures in the work area make it difficult to ensure the safety of personnel.
The detonation-gas method stands somewhat apart. During the explosion, the speed of the particles reaches 1000-2000 m/s. Therefore, the main factor determining the quality of the coating is their kinetic energy. Coatings are characterized by high adhesion and low porosity, but explosive processes are extremely difficult to control, and it is practically impossible to guarantee the stability of the result.
SPEED PLUS TEMPERATURE
The desire to create a more advanced technology arose a long time ago. The engineers had a goal - to preserve the advantages of traditional technologies and get rid of their shortcomings. The direction of the search was more or less obvious: firstly, the coatings should be formed mainly due to the kinetic energy of the metal particles (the particles should not be allowed to melt: this will prevent the part from heating and the substrate and coating particles from oxidizing), and, secondly, the particles should acquire high speed not due to the energy of the explosion, as in the detonation-gas method, but in a jet of compressed gas. This method is called gas dynamic.
The first calculations and experiments showed that it is possible to create coatings with quite satisfactory characteristics in this way if helium is used as the working gas. This choice was explained by the fact that the speed of the gas flow in the supersonic nozzle is proportional to the speed of sound in the corresponding gas. In light gases (hydrogen was not considered because of its explosiveness), the speed of sound is much higher than in nitrogen or air. It was helium that would accelerate metal particles to high speeds, imparting to them the kinetic energy sufficient to fix them on the target. It was believed that the use of heavier gases, including air, was doomed to failure.
The operation of experimental sputtering installations gave a good result: particles from most industrially used metals accelerated in a helium jet adhered well to the substrate, forming dense coatings.
But the engineers were not completely satisfied. It was clear that equipment running on light gases would inevitably be expensive and could only be used at enterprises producing high-tech products (only there are lines with compressed helium). And lines with compressed air are available in almost every workshop, at every car service enterprise, in repair shops.
Numerous experiments with compressed air seemed to confirm the worst expectations of the developers. However, an intensive search nevertheless led to a solution. Coatings of satisfactory quality were obtained when the compressed air in the chamber in front of the nozzle was heated, and fine ceramics or hard metal powder were added to the metal powder.
The fact is that when heated, the air pressure in the chamber increases in accordance with Charles's law, and, consequently, the speed of the outflow from the nozzle also increases. The metal particles, which have gained tremendous speed in the gas jet, soften when they hit the substrate and weld to it. Ceramic particles play the role of microscopic sledgehammers - they transfer their kinetic energy to the underlying layers, compact them, reducing the porosity of the coating.
Some ceramic particles get stuck in the coating, others bounce off it. True, coatings are obtained in this way only from relatively ductile metals - copper, aluminum, zinc, nickel, etc. Subsequently, the part can be subjected to all known methods of machining: drilling, milling, sharpening, grinding, polishing.
THE MAIN CONDITION - SIMPLICITY AND RELIABILITY
The efforts of technologists will be in vain if the designers cannot create simple, reliable and economical equipment in which the process invented by technologists would be implemented. The basis of the apparatus for spraying metal powders was a supersonic nozzle and a small-sized electric compressed air heater capable of bringing the flow temperature to 500-600 o C.
The use of ordinary air as a working gas made it possible to simultaneously solve another problem that faced the developers of systems using light gases. We are talking about the introduction of the sprayed powder into the gas jet. To maintain tightness, the feeders had to be installed up to the critical section of the nozzle, that is, the powder had to be fed into the high pressure area. Purely technical difficulties were exacerbated by the fact that, passing through the critical section, metal particles caused wear of the nozzle, worsened its aerodynamic characteristics, and did not allow stabilization of the coating deposition modes. In the design of the apparatus with an air jet, the engineers applied the principle of a spray gun, known to everyone from school experiments in physics. When a gas passes through a channel of variable cross section, then in a narrow place its velocity increases, and the static pressure drops and may even be lower than atmospheric pressure. The channel through which the powder came from the feeder was located just in such a place, and the powder moved into the nozzle due to air suction.
As a result, a portable apparatus for applying metal coatings was born. It has a number of advantages that make it very useful in various industries:
for the operation of the apparatus, only an electrical network and an air line or a compressor are needed, providing a compressed air pressure of 5-6 atm and a supply of 0.5 m 3 / min;
when applying coatings, the temperature of the substrate does not exceed 150 ° C;
coatings have high adhesion (40-100 N/mm2) and low porosity (1-3%);
the equipment does not emit harmful substances and radiation;
the dimensions of the device allow it to be used not only in the workshop, but also in the field;
coatings of almost any thickness can be sprayed.
The installation includes the actual sprayer weighing 1.3 kg, which the operator holds in his hand or fixes in the manipulator, an air heater, powder feeders, a unit for monitoring and controlling the operation of the sprayer and feeder. All this is mounted on a rack.
I had to work hard on the creation of consumables. Commercially available powders have too large particle sizes (of the order of 100 microns). A technology has been developed that makes it possible to obtain powders with grains of 20-50 microns.
FROM SPACE VEHICLES TO SEEDERS
The new method of spraying metal coatings can be used in a wide variety of industries. It is especially effective in repair work, when it is necessary to restore parts of products, for example, to repair a crack or a sink. Due to the low temperatures of the process, it is easy to restore thin-walled products, which cannot be repaired in another way, for example, by surfacing.
Since the spraying zone has clear boundaries, the sprayed metal does not fall on defect-free areas, and this is very important when repairing complex-shaped parts, such as gearbox housings, engine cylinder blocks, etc.
Spraying devices are already used in the aerospace and electrical industries, in nuclear power plants and in agriculture, in auto repair enterprises and in foundries.
The method can be very useful in many cases. Here are just a few of them.
Restoration of worn or damaged areas of surfaces. With the help of spraying, parts of gearboxes, pumps, compressors, molds for investment casting, molds for the manufacture of plastic packaging that are damaged during operation are restored. The new method has become a great help for car repair workers. Now, literally "on their knees", they close up cracks in cylinder blocks, mufflers, etc. Without any problems, they eliminate defects (cavities, fistulas) in aluminum castings.
Elimination of leaks. The low gas permeability of the coatings makes it possible to eliminate leaks in pipelines and vessels when sealing compounds cannot be used. The technology is suitable for repairing tanks operating under pressure or at high and low temperatures: heat exchangers, car radiators, air conditioners.
Application of electrically conductive coatings. By sputtering it is possible to apply copper and aluminum films on a metal or ceramic surface. In particular, the method is more cost-effective than traditional methods when copper-plating current-carrying busbars, galvanizing pads on grounding elements, etc.
Anti-corrosion protection. Aluminum and zinc films protect surfaces from corrosion better than paint and many other metal coatings. The low productivity of the installation does not allow processing large surfaces, but it is very convenient to protect such vulnerable elements as welds. With the help of spraying zinc or aluminum, it is possible to stop corrosion in places where "bugs" appear on the painted surfaces of car bodies.
Restoration of plain bearings. Plain bearings usually use babbitt liners. Over time, they wear out, the gap between the shaft and the sleeve increases and the lubrication layer is broken. Traditional repair technology requires either replacement of the liner or welding of defects. And spraying allows you to restore the liners. In this case, ceramics cannot be used to seal the layer of the sprayed metal. Hard inclusions in a matter of minutes after the start of work will disable the bearing, and the surfaces of both the bushings and the shaft will be damaged. I had to use a nozzle of a special design. It allows the coating of pure babbitt in the so-called thermokinetic mode. Powder particles immediately behind the critical section of the nozzle are accelerated by a supersonic air flow, then the flow velocity sharply decreases to transonic. As a result, the temperature rises sharply, and the particles are heated almost to the melting point. When they hit the surface, they deform, partially melt and stick well to the underlying layer.
TO A SPECIALIST - A NOTE
Literature
Kashirin A. I., Klyuev O. F., Buzdygar T. V. Device for gas-dynamic coating of powder materials. RF patent for invention No. 2100474. 1996, MKI6 C 23 C 4/00, publ. 12/27/97. Bull. No. 36.
Kashirin A. I., Klyuev O. F., Shkodkin A. V. The method of obtaining coatings. RF patent for invention No. 2183695. 2000, MKI7 C 23 C 24/04, publ. 06/20/02. Bull. No. 17.
Contacts of developers and conditions for purchasing their technologies or products can be found in the editorial office.
Cold gas spraying is the latest method in the field of thermal spraying. Compared to conventional thermal spray processes, cold gas dynamic spraying has particular advantages because the spray material does not melt or melt during the process. Thus, the thermal effect on the coating and substrate material remains low.
The high kinetic energy of the particles and the high degree of deformation upon impact on the substrate, which is associated with it, makes it possible to produce uniform and very dense coatings. The range of coating thickness varies from a few hundredths of a millimeter to several centimeters.
In the obtained metal coatings, the physical and chemical properties practically do not differ from those of the base material.
According to the latest system technology from Impact Innovations GmbH, an inert gas - preferably nitrogen or helium - is fed into the spray gun at a pressure of up to 50 bar (725 psi) and heated to a maximum temperature of 1100 °C (2012 °F) in pistol body.
The subsequent expansion of the heated and pressurized gas in the convergent-divergent nozzle to ambient pressure accelerates the process inert gas to supersonic speed and at the same time cools the gas below 100 °C (373 °F).
Sprayable powders are injected into the converging part of the nozzle by means of a powder and carrier gas feeder and accelerated to a particle velocity of 1200 m/s in the main gas stream.
In the highly constricted spray nozzle, the particles hit the untreated, in most cases, component surfaces, deform and turn into a highly adhesive / cohesive and low oxide coating.
Effect of Particle Velocity on Coating Quality and Efficiency
- The coating particle has reached the minimum impact velocity, which is necessary to excite the mechanism of interaction with the surface of the substrate (processed sample). This so-called "critical speed" influences the properties of the coating material.
- Since the impact velocity is higher than the critical velocity, the deformation and adhesion quality of the particles increase.
- If the impact velocity is too high (the "erosion rate"), more material is destroyed than it is added. The coating does not form.
- In order to form a dense and well-formed coating, the particle impact velocity must be between the critical velocity and the erosion velocity.
What can be coated with cold gas dynamic spraying?
Coating materials
Metals: such as magnesium, aluminum, titanium, nickel, copper, tantalum, niobium, silver, gold, etc.
Alloys: for example, nickel-chromium, bronze, aluminum alloys, brass, titanium alloys, MCrAlY powders (alloys based on the base metal (Co, Ni, Cr, Fe) with the addition of chromium, aluminum and yttrium), etc.
mixed materials(metal matrix in combination with solid phases): e.g. metal and ceramics, composites.
Base materials
Metal products and samples, plastics, as well as glass and ceramics.
Individual processing
Each individual material is processed individually.
Processing materials requires individual adjustment of temperature and gas pressure. The combination of these two physical parameters determines the speed of the particles and the quality of the coating. The range of optimal sputtering rate, limited by the critical rate and the erosion rate, is called the settling range. Within this range, the quality of coating deposition is influenced by parameters.
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By the way, Obninsk engineers have already developed several modifications of DIMET installations. Given the wide demand for this equipment, both manual and automated cold gas-dynamic spraying machines are now mass-produced, which allows them to be used in industry, the oil and gas industry, as well as in small businesses for processing small parts. Moreover, there is nothing particularly complicated in the technology itself. For the operation of the complex (in addition to the material for spraying), only compressed air is needed (supplied at a pressure of 0.6-1.0 MPa and a flow rate of 0.3-0.4 m3/min.) And a 220 V power supply.
Now about the advantages and disadvantages of the method. Equipment for metal spraying from China? Firstly, in contrast to the gas-thermal method, CGN can be effectively used at normal pressure, in any temperature range and humidity level.
Secondly, it is environmentally absolutely safe. Thirdly, due to the high speed, it can also be used for abrasive surface cleaning. Well, the only drawback of the technology is the possibility of applying coatings only from relatively ductile metals, such as copper, aluminum, zinc, nickel, etc.
Scope of CGN
I would like to dwell in more detail on the areas of application of the technology of cold gas-dynamic spraying with powder materials in order to clearly show how much it is in demand today.
Elimination of defects, restoration of surfaces and sealing
All this is a job that even small businesses can do. For example, in small workshops it is possible to repair parts made of light alloys (parts of an automotive structure, for example), primarily aluminum and aluminum-magnesium. Moreover, defects that have arisen both in the production process and during operation are easily eliminated.
And the absence of strong heating and the low energy of the method make it possible to repair even thin-walled products. 
CGN is also excellent for restoring worn surfaces. For example, such a labor-intensive process as “building up” metal in bearing seats can now be carried out even by small enterprises, not to mention the restoration of sealing (when the use of liquid sealants is impossible) in pipelines, heat exchangers or vessels for working gases, liquids.
High-precision restoration of parts of various mechanisms, current conduction
CGN it is very effective in the repair of complex products, where exact restoration of geometric parameters is required, elimination of hidden defects, but at the same time with the preservation of all operational characteristics, as well as the presentation. That is why this method is actively used in the military-industrial complex, the railway and aviation industries, agriculture, gas transmission, etc.
You can not do without this technology in the creation of contact pads. Prices for equipment for spraying metals? Due to the possibility of easy coating on any metal, ceramic and glass surfaces, CGN is also used in the production of electrical products. For example, in the processes of copper plating, the creation of power current-carrying networks, the application of current leads, the manufacture of sublayers for soldering, etc.
Anti-corrosion treatment and elimination of deep defects
Spraying the so-called anti-friction coating is a highly effective way to get rid of local damage (deep chips, scuffs, scratches). This avoids the procedure of complete refilling or even replacement of the product, which, of course, is not economically viable.
And in anti-corrosion treatment and protection against high-temperature corrosion of various communications, this method has no equal at all. By the way, various modifications of equipment DIMET ® provide high-quality processing of the inner surface of pipes with a diameter of 100 mm and a length of up to 12 m.
Additional Information:
Heat-resistant coatings are applied by the gas-dynamic method, which provide protection up to 1000-1100 degrees Celsius. The electrical conductivity averages 80-90% of the electrical conductivity of the bulk material. Corrosion resistance depends on the characteristics of the aggressive environment.
The operation of the DIMET equipment, developed and mass-produced by the “Obninsk Center for Powder Spraying” (OOO “OCPN”), is based on the effect of fixing metal particles, if they move at supersonic speed, on the surface when colliding with it, gas-dynamic spraying of DIMET metals. The technology makes it possible to apply metal coatings not only on metals, but also on glass, ceramics, stone, and concrete. By now, the DIMET technology makes it possible to apply coatings of aluminum, zinc, copper, tin, lead, babbits, nickel and apply them not only to metals, but also to glass, ceramics, stone, and concrete.
Plakart specialists produce gas-dynamic coatings for industrial equipment (for example, in the photo - anti-corrosion coating of a heat exchanger without dismantling). In addition, we supply turnkey cold gas-dynamic spraying installations (adjustment, service, training).
Depending on the composition of the consumable material (powder) and changing the modes of its application, it is possible to obtain a homogeneous or composite coating with a solid or porous structure and its own functional task. This can be: restoring the geometry of the product, strengthening and protecting the metal from corrosion, increasing the thermal and electrical conductivity of the material, as well as the formation of a wear-resistant coating that can withstand the effects of chemically active environments, high thermal loads, etc.
In Browning's description of the invention, these problems are discussed but not resolved. The way out of this situation opens up a spraying method in which the powder is not heated to a molten state. The idea of the possibility of "cold welding" of small metal particles during their high-speed collision with a solid surface was expressed in the invention of Shestakov back in 1967. The proposal for cold welding of particles in a dynamic mode was not developed at that time.
Equipment for cold gas-dynamic spraying of metals? Because to implement the cold spraying regime, new proposals were needed for the design of the nozzle assembly.
