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A cylinder head damaged by corrosion, a clutch crankcase turned by a stone, or a leaking conditioner radiator can now be repaired in minutes using a unique installation for air deposition of metals.

Anatoly SUKHOV

In the early 90s, when the Russian economy was falling apart before our eyes, a group of physicists from Obninsk near Moscow decided to prove that science is not a pauper on the porch of the state and is able not only to survive in market conditions, but to develop and make a profit.

At the beginning of the 80s, Novosibirsk scientists discovered an interesting phenomenon: if particles of metal with a size of 5-50 microns are accelerated to speeds of 500-600 m / s (the speed of sound in air is 330 m / s), then when they collide with a metal plate, they stick to it forming a durable coating. This is similar to firing microscopic bullets, spreading across a target, like butter on a sandwich. However, things didn’t go beyond laboratory experiments: there was nothing to think about the practical application of the discovery with thin and cumbersome experimental facilities.

Obnintsy, evaluating the prospects of the method, decided to put theory into practice and create an industrial installation. We had to design from scratch, and place orders for parts privately at the defense enterprises of the city. Today, the technology of the Obninsky Powder Spraying Center is already being used by rocket launchers (Design Bureau Salyut) and nuclear specialists (Smolensk NPP). There are no analogues to Dimetu in the world yet - as the scientists called their installation. It is already patented in the USA, Europe, China. Daimler-Chrysler also took an interest in it, inviting developers to his factory for a demonstration. How is the apparatus arranged and what are the advantages of the new method?

One of the main details of the installation is the Laval nozzle, which accelerates a gas stream to supersonic speeds (the same, only large sizes, are mounted on rocket engines). In order to reduce the cost of consumables and make the installation universal, we decided to abandon convenient in use, but expensive inert gases in favor of compressed air from a conventional compressor developing 6 atm at a flow rate of 0.3 mz / min. At the entrance to the nozzle, a red-hot spiral heats the air to about 700 ° C; otherwise, it cannot be dispersed to the required 500–600 m / s. The nozzle and heating element are combined in a sprayer that the operator holds in his hand. You can’t get burned - thermal protection is similar to that installed on the "Buran". Metal powder is poured into a special feeder with a vibrator, from where it is fed through a hose to the nozzle exit and is carried away by a stream of air. Adjustment of the spraying mode and multilevel protection (voltage surges, compressor failure, etc.) are provided.

What can be sprayed? It is mainly aluminum, zinc, copper, brass. Apply to any metals and alloys, glass, ceramics, stone. Materials that are “unconnected” by traditional methods are combined - for example, steel and aluminum, aluminum and copper, and the tensile strength is very high - 5–10 kgf / mm2. The coating thickness is practically unlimited and can be centimeters, and the porosity does not exceed 5%. It can be sharpened, drilled, milled. This structure is achieved thanks to ceramic additives to the main powder. They do not spend their kinetic energy on melting, but upon impact they give it to the metal, "forging" and compacting it.

The new method has many advantages. The coating is applied literally "on the knee", at room temperature, in the open air. Neither expensive vacuum chambers, nor heated melt baths, nor high voltage are needed. Thorough preparation of parts is not required. "Dimet" allows you to apply metal on oily, painted, even slightly rusty surfaces or on an uncleaned weld - all that is superfluous is simply swept away by a high-speed stream. It is possible to confine oneself only to surface cleaning (without coating) by supplying a clean abrasive to the nozzle instead of metal powder.

One of the main advantages of the method is insignificant heating of parts (surface temperature does not exceed 100–150 ° С). So, there are no deformations associated with overheating, steel tempering. In addition, the repaired part is practically impossible to spoil (melt or burn, as during welding): the new metal simply “builds up” from above, and its excess can then be removed by machining. However, with a certain skill, subsequent processing is minimized - the method allows you to apply the coating precisely to the treated area, without "dusting" the neighboring areas.

The main disadvantage of this method is that it cannot be reached into a secluded stream of powder; the optimal position of the spray gun is perpendicular to the surface being treated at a distance of 5–20 mm. Working at an acute angle (for example, when restoring a candle hole in the cylinder head) requires skill (as with ordinary enamel painting). Another disadvantage associated with the use of compressed air as a carrier is the inability to apply iron coatings. However, often this is not necessary: ​​a broken steel tube can be sealed with aluminum, and a cracked cast-iron cylinder block with copper. Let us consider in more detail what and how it is possible to repair Dimet in a car.

One of the most promising components for repair is the radiator of an automobile air conditioner (condenser). As a rule, it is located in front of the radiator of the cooling system, so all the salt and stones go to him. Salt quickly eats through the thin walls of the tubes. Soldering rarely helps (it is not possible to choose the right solder, completely clean the surface from corrosion products), adhesives are unreliable, and welding is completely useless. Spray restoration takes only a few minutes (no need to clean the surface), and the patch will probably outlast the tube itself.

Many problems are caused by cylinder heads on older cars. Of course, most owners of domestic cars would never even think of restoring “gaps” between cooling channels - it’s easier to buy a new head. But if a foreign car with a rare engine, or even real antiques, the cost of a new part with delivery can become comparable to the price of a car. This is where Dimet comes in handy - maybe, during repairs, you won’t even have to crack the valves, and the cost of consumables will not exceed a dollar.

Once they brought an aluminum crankcase from some jeep with two huge holes - the wizard-masters tried to weld cracks after the impact and burned the “winged metal”. In a few minutes the wound was healed, it remains to walk on an emery - and the part is like new.

Everyone knows that welding work on a car is always undesirable: it is almost impossible to reliably protect the welding place from corrosion. Galvanizing the weld seam after repair is not a problem with Dimet, especially since it is not necessary to clean the seam, and zinc can be applied as much as you wish (1 kg of powder costs 7-10 dollars).

Anyone can easily work with the installation, and after training, you can create a very complex relief. If you spray the gun evenly, you get an even matte finish, stop it - the stalagmite grows - this is not paint that is afraid of drips.

Probably, after meeting with "Dimet" many will think: is it possible for them to replace welding? The parts do not heat up, you cannot tear off the coating from the base metal with a chisel … But the developers warn that welding is still much stronger, especially at a break, therefore, when connecting loaded parts, this should be remembered.

Today, in Obninsk, they produce a special portable installation for auto repair "Dimet-402" powered by 220 V mains (power consumption 2.2 kW) at a price of $ 2, 300-3, 000, depending on the configuration (compressor is not included). Although why only for car repair? Have you ever painted metal on glass?

This is how the portable installation “Dimet-402” looks like: 1 - spray gun; 2 - feeders; 3 - pressure regulator and moisture separator; 4 - control unit spraying mode.

Opportunities of “Dimet: protection of welds and their sealing, spraying of coatings of large thickness, coating by stencil, metallization of glass.

1. Repaired gearbox (light metal - sprayed).

2. Restore the tightness of the condenser.

3. We repair a head of the block of cylinders. Feeders and powder containers are visible on the right.