RU2329104C2 - Method for detonating application of coatings and apparatus for implementing thereof - Google Patents

Abstract

FIELD: blasting.

SUBSTANCE: problem that the claimed inventions are aimed to solve is extending the technological capabilities of detonation spraying. The essence of this method consists in injecting a predetermined volume of incombustible working gas into a barrel before filling thereof with a detonable gas mixture. Prior to igniting the mixture a zone filled with said detonable gas mixture is created at the closed end of the barrel and a zone filled with said incombustible working gas is created at the open end, powder is supplied to the incombustible working gas zone and the particles are accelerated by a shockwave being transmitted through the inflammable working gas. The claimed device is fitted with an additional valve intended for injecting the incombustible working gas into the barrel and disposed at the closed end of the barrel. This method for application of coatings is essentially a shock wave method, whereby powder particles are accelerated by a shockwave excited in the incombustible working gas by expanding detonation products of the detonable gas mixture.

EFFECT: extending capabilities of the detonation spraying method.

4 cl, 5 dwg

Description

The invention relates to detonation spraying and can be used for applying powder coatings for various purposes on parts of various materials.

Known methods of detonation coating (see, for example, US patent No. 2714563 (1955) [1], US patent No. 2972550 (1958) [2], Shesternenkov VI Detonation coating. // Powder metallurgy , 1968, No. 1, pp. 37-47 [3], V. Teller, E. Schwartz. The detonation method of coating. // Production of coatings by high-temperature spraying. Collection of articles. Edited by L.K. Druzhinin, V. V. Kudinova. M.: Atomizdat, 1973, p.133-139 [4], US patent No. 5985373 (1999) [5]). Detonation spraying allows the coating of metals, heat-resistant alloys and ceramics on substrates of a wide variety of materials: metals, alloys, ceramics, glass, plastics, etc. For known methods of detonation spraying, it is common that the process is carried out using detonation units (guns) and the coatings are applied in the mode of continuously repeating cycles (shots) with a duration of each cycle of a fraction of a second. However, the known methods do not allow to apply high-quality coatings from materials that decompose, evaporate or change structure at elevated temperatures, since powder particles are heated by spraying under the influence of high-temperature detonation products, since they are accelerated by the flow of these products.

Closest to the proposed method is a method of detonation coating (see. "Detonation spraying of coatings", A. I. Zverev, S. Yu. Sharivker, E. A. Astakhov. - L .: Sudostroenie, 1979, [6], pp. .165 selected as a prototype).

According to the prototype, the coating is applied in a cyclic mode, and each cycle includes the following basic operations: filling the mixing chamber and the barrel with a detonating gas mixture, introducing a portion of the sprayed powder into the barrel, igniting the mixture (at the closed end of the barrel), forming the coating and blowing the barrel with nitrogen. All operations within the cycle are synchronized. The main technological parameters of the process are: the composition of the combustible gas, its flow rate, the frequency of shots, the flow rate of the powder, the method and place of its supply to the barrel, particle size. The coating is usually multi-layer. The first shots cause the first layer, which lies directly on the workpiece (substrate), then the following layers are applied, which lie on top of each other.

The disadvantage of this method is its lack of technological capabilities. Since particles are accelerated in a detonation wave by a stream of high-temperature and high-speed detonation products, the powder particles undergo strong heating and can also react with surrounding gases ([6], p. 61). This is due to the fact that it is recommended to bring the powder into the area between the trunk cut and the point of mixture ignition where a stable detonation wave propagates ([7], p. 111). For a number of materials, in particular for refractory compounds, heating is useful and, in combination with the high particle velocity characteristic of detonation spraying, makes it possible to apply durable low-porous coatings. However, there are materials for which contact with high-temperature detonation products can lead to an undesirable change in their chemical composition, microstructure and properties, as well as in the case of polymer coatings, and their decomposition. This limits the possibilities of the known method of detonation spraying.

Known devices for detonation coating [1, 5, 7] having a barrel open at one end, a gas supply unit, a spray powder supply unit and an explosion initiation unit with an igniter (candle) ([7], p. 11). The gas supply unit in these devices is designed to supply detonating mixture and purge gas to the barrel. The purge gas is used to displace the remaining detonation products from the barrel in order to prepare the device (gun) for the next shot. Usually, relatively cheap nitrogen, sometimes even air, is used for purging. However, the supply of some non-combustible gas to the barrel, except for the purge, is not provided in the designs, which limits the ability to control acceleration and heating of powder particles not only by varying the composition and volume of the detonating mixture, but also by filling part of the barrel with some other except purge, non-flammable gas.

Closest to the proposed device is a device known from [6], selected as a prototype.

The known device comprises a barrel open at one end, an igniter of the detonating gas mixture, valves for supplying combustible gas, an oxidizing agent and purge gas to the barrel, and a device for introducing powder into the barrel.

However, in the known device it is not possible to fill the barrel with some other non-combustible (except purge) gas, which significantly narrows its technological capabilities, since the process of accelerating and heating particles in the barrel depends not only on the composition and volume of the detonating mixture, but also on the type of gas, before firing, a part of the barrel is filled between its open end and the volume filled with the detonating mixture.

Thus, the disadvantages of the known method and device are insufficient technological capabilities.

The task to which the claimed invention is directed is to expand the technological capabilities of detonation spraying.

To solve the problem, the essence of the proposed method is that, in contrast to the known method of detonation coating, consisting of a continuous sequence of cycles, each of which includes filling the barrel with a detonating gas mixture, introducing a portion of the sprayed powder into the barrel, setting the mixture on fire in a closed the end of the barrel, forming a coating and cleaning the barrel with purge gas, according to the invention, before filling the barrel with a detonating gas mixture, a predetermined volume of working gas, so that before igniting the mixture at the closed end of the barrel, a zone filled with a detonating gas mixture is created, at the open end, a zone filled with a non-combustible working gas, and the powder is fed into the zone of non-combustible working gas and the particles are dispersed by a shock wave passing through the non-combustible working gas .

In this case, a gas, such as argon, carbon dioxide, krypton or xenon, or a lighter gas, like neon or helium, is used as a non-combustible working gas.

In addition, in some cases, nitrogen or air can be used as a non-combustible working gas and as a purge gas.

Also, to solve the problem, the essence of the claimed device consists in that, in contrast to the known device containing a barrel open at one end, an igniter of a detonating gas mixture, valves for supplying combustible gas, an oxidizing agent and a purge gas to the barrel, the mechanism for introducing powder into the barrel, according to According to the invention, the device is equipped with an additional non-combustible working gas supply valve located at the closed end of the barrel.

It is the claimed design differences - the characteristics of the device for detonation coating allows you to implement the inventive method of detonation coating, thereby ensuring the achievement of the task, which allows us to conclude that the claimed invention are connected by a single inventive concept.

The technical result that can be obtained as a result of using the invention is to expand the technological capabilities of detonation spraying, which will make it possible to apply high-quality coatings from materials that decompose, evaporate or change structure at elevated temperatures.

When coating in each shot, the detonation installation barrel is filled in such a way that at the closed end of the barrel there is a zone with a detonating gas mixture, and at the open end there is a zone with specially selected non-combustible working gas. A portion of the powder is introduced into the barrel in the zone of non-combustible working gas and the detonating gas mixture is ignited at the closed end of the barrel. The detonation wave propagates along the barrel and, having reached the zone with the working gas, passes into a shock wave, which, propagating to the open end of the barrel, accelerates particles whose flow is directed to the part. After the shot, the barrel is cleaned with purge gas. The required temperature and particle velocity is achieved by choosing the detonating gas mixture and its volume, non-combustible working gas and its volume, as well as the place of powder supply to the barrel (loading depth). As a result, particles are accelerated by a shock wave passing through the working gas, and they do not interact with high-temperature and chemically active detonation products. Nitrogen or air is used as purge gas. As a non-combustible working gas, both purge gas and other gases that differ in density and speed of sound from air and nitrogen, such as argon, carbon dioxide, krypton, xenon, neon and helium, can be used.

The invention is illustrated by drawings, which depict successive stages of the coating cycle.

Figure 1 shows the stage of filling the barrel with a non-combustible working gas, figure 2 shows the stage of supplying the detonating mixture to the barrel and introducing a portion of the powder, figure 3 shows the stage of ignition of the detonating mixture and the propagation of the detonation wave through it, figure 4 shows the stage shock wave propagation through a non-combustible working mixture and acceleration of powder particles by a shock wave; Fig. 5 shows the stage of coating formation and barrel cleaning with purge gas.

The numbers in the drawings indicate: 1 - barrel of the detonation gun, 2 - powder batcher, 3 - sprayed powder in the batcher, 4 - workpiece (substrate), 5 - barrel volume occupied by purge gas, 6 - interface between the purge and non-combustible working gas , 7 - the volume of the barrel occupied by non-combustible working gas, 8 - the valve for supplying the detonating mixture to the barrel, 9 - the valve for supplying the barrel of non-combustible working gas, 10 - the valve for supplying the purge gas to the barrel, 11 - the spark plug, 12 - the volume of the barrel occupied detonating gas mixture, 13 - interface between detonating gas mixture and working gas, 14 — front of the detonation wave, 15 — front of the shock wave in the working gas, 16 — portion of the powder dispersed by the shock wave, 17 — front of the wave propagating through the detonation products toward the closed end of the barrel, 18 — coating, formed on the substrate, 19 is the interface between the purge gas and the detonation products.

The inventive method is as follows.

In each cycle of the coating process, called a shot, the barrel 1 is first filled with non-combustible working gas through valve 9, so that the working gas fills the volume of the barrel 7, displacing the purge gas 5 left there after cleaning the barrel, and the boundary between these gases 6 moves to the side trunk cut (figure 1). The valves 8 and 10 for supplying the detonating mixture and purge gas are closed. Then the barrel 1 is filled with the detonating gas mixture through the valve 8, so that upon completion of filling at the closed end is the zone of the detonating gas mixture 12, and at the open end is the zone of the working gas 7 with a border 13 between them (figure 2). Valves 9 and 10 for supplying working and purge gases are closed. Then, during or after the supply of the detonating gas mixture into the barrel 1, a portion of the powder 3 from the dispenser 2 is introduced into the working gas zone 7 (Fig. 2). At the next stage, detonation is initiated at the closed end of the barrel with the spark plug 11 (Fig. 3). The detonation front 14 moves along the volume of the detonating gas mixture 12 and, after reaching the interface 13, it splits into a reflected wave 17 moving along the detonation products toward the closed end of the barrel, and a shock wave 15 moving along the non-combustible gas toward the open end of the barrel and involving in motion powder 16 in the direction of the substrate 4 (figure 4). As a result of the collision of the powder particles with the substrate, a coating 18 is formed (Fig. 5). Next, the barrel is cleaned with purge gas supplied through valve 10. Valves 8 and 9 for supplying the detonating gas mixture and the working gas to the barrel are closed. The place of supply of the powder into the barrel, as well as the ratio of the volumes of the detonating gas mixture 12 and the working gas 7 in the barrel before igniting the mixture, is set so that the powder particles do not enter the detonation products. That is, so that they are not caught up with the boundary of section 13 (Fig. 4). Non-combustible working gas 7 is selected for each specific case so as to provide the necessary speed and temperature of the particles for coating. To control particle acceleration, non-combustible working gas can be used as heavier than nitrogen and air gases, for example argon, carbon dioxide, krypton or xenon, whose density is 1.38, 1.53, 2.89 and 4, respectively. 53 times greater than the density of air, and lighter, such as neon and helium, the density of which is respectively 1.44 and 7.24 times less than the density of air. It is not practical to use these gases for purging because of their high cost. In some cases, for example, when spraying small particles of aluminum or PTFE granules, purge gas can be used as a working gas, i.e. nitrogen or air.

Thus, the inventive coating method is essentially a shock wave method in which the acceleration of powder particles is carried out by a shock wave excited in a non-combustible working gas by expanding detonation products of a detonating gas mixture.

The application of the invention significantly expands the possibilities of the method of detonation spraying, since it allows the application of coatings from decaying or changing properties in contact with the products of detonation of materials.

Literature

1. R. M. Poorman, H. B. Sargent, and H. Lamprey. Method and Apparatus Utilizing Detonation Waves for Spraying and other Purposes. US Patent No. 2714563 of Aug. 2, 1955.

2. John F. Pelton. Flame Plating Using Detonation Reactants. US Patent No. 2972550 of May 28, 1958.

3. Shesternenkov V.I. Knock coating. / Powder Metallurgy, 1968, No. 1, p. 37-47.

4. W. Teller, E. Schwartz. Detonation coating method. / Obtaining coatings by high temperature spraying. Sat articles. Ed. L.K. Druzhinina, V.V. Kudinova. M .: Atomizdat, 1973, p.133-139.

5. Chernyshov A.V. Method and Apparatus for Applying Multi-Layered Coatings by Detonation. US Patent No. 5985373 of Nov.16, 1999.

6. A.I. Zverev, S.Yu. Sharivker, E.A. Astakhov. Knock coating spraying. - L .: Shipbuilding, 1979.

7. Bartenev S.S., Fedko Yu.P., Grigorov A.I. Knock coatings in mechanical engineering. - L .: Engineering, Leningrad. Department, 1982.

Claims (4)

1. The method of detonation coating, comprising a continuous sequence of cycles, each of which includes filling the barrel with a detonating gas mixture, introducing a portion of the sprayed powder into the barrel, setting the mixture on fire, forming the coating and cleaning the barrel with purge gas, characterized in that before filling the barrel with detonating gas with a gas mixture, a predetermined volume of non-combustible working gas is admitted into it so that before igniting the mixture at the closed end of the barrel, an area filled with a detonating gas mixture is created , At the open end - a zone filled with non-combustible working gas, a powder is fed into a zone of non-combustible working gas and the particles dispersed by passing incombustible working gas shock wave. 2. The method according to claim 1, characterized in that argon, carbon dioxide, krypton, xenon, neon or helium are used as a non-combustible working gas, and nitrogen or air is used as a purge gas. 3. The method according to claim 1, characterized in that nitrogen or air is used as a non-combustible working gas and as a purge gas. 4. A device for implementing the method of detonation coating, comprising a barrel open at one end, an ignitor of a detonating gas mixture, valves for supplying combustible gas, an oxidizing agent and purge gas to the barrel, a mechanism for introducing powder into the barrel, characterized in that it is equipped with an additional valve for feeding barrel of non-combustible working gas located at the closed end of the barrel.

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