RU2542218C2 - Method of production of nanostructured coating - Google Patents

Abstract

FIELD: nanotechnology.

SUBSTANCE: invention relates to a method of production of nanostructured coatings for protecting surfaces of articles. The method comprises forming a high temperature gas flow in the combustion chamber of the sprayer by combustion of fuel in the oxidant, supply to the combustion chamber of the starting material which is a source of formation of nanoparticles, formation and transfer by the high temperature gas flow of nanoparticles and their deposition on the substrate. At that in the combustion chamber by the influence of the high temperature gas flow the starting material is converted to a gaseous state. Then the gas flow after leaving the combustion chamber is quenched to a temperature below the melting temperature of the starting material. Quenching the gas flow may be carried out by mixing with a cold flow of inert gas.

EFFECT: obtaining nanostructured coatings of high quality with use of powder materials of metallurgical industry.

2 cl, 2 dwg, 2 ex

Description

The present invention relates to methods for producing nanostructured surface coatings of products using methods of thermal spraying. Nanostructured coatings can significantly increase the strength and anti-corrosion properties of the surface of products, which ensures an increase in their operational life. The use of nanostructured coatings also makes it possible to produce multilayer nanocomposite materials.

Various methods of thermal spraying are known. In particular, flame spraying is known in which a sprayed material in the form of a powder is continuously supplied to the surface of a part using a gas flame burner (see, for example, RF patent No. 2432416 C1, IPC C23C 4/12). The powder accelerates under the action of a stream of hot gas and melts when heated. Upon impact with the surface of the part, molten droplets spread and solidify, forming a protective coating. However, flame spraying does not provide a nanostructured coating.

There is also a known method of detonation spraying, in which the heating and transportation of particles of powder material to the surface of the part is carried out by using the energy of detonation of a gas mixture (see, for example, the book: Thermal spraying: a training manual / number of authors; edited by L.Kh. Baldaev - M.: Market DS, 2007. S.116-121). Detonation spraying provides a high speed of approach of the powder particles to the surface of the part, which significantly increases the adhesion of the resulting coating to the surface of the part. However, detonation spraying also does not provide a nanostructured coating.

Closest to the proposed invention in terms of features is a method for producing a nanostructured coating, which consists in the formation in the combustion chamber of a high-speed atomizer of a high-temperature gas stream by burning fuel in an oxidizer, in the supply to the combustion chamber of a high-speed atomizer of a liquid source material, which is the source of nanoparticle formation, in the formation of heating and transporting nanoparticles by high-temperature gas flow and their deposition on a substrate, and the liquid source material, which is the source of the formation of nanoparticles, is simultaneously used as fuel for the formation of a high-temperature gas stream, while the material itself is a true or colloidal solution of organic and / or inorganic compounds in an organic solvent or a mixture of several solvents (RF patent No. 2394937 C1, IPC C23C 4/10, B82B 3/00).

A disadvantage of the known method is the use of a true or colloidal solution of organic and inorganic compounds in an organic solvent serving as fuel as a starting material. On the one hand, the preparation of such a solution generally complicates and increases the cost of the coating process. On the other hand, not every material used for coating is soluble in an organic solvent serving as fuel. This limits the technological capabilities of this method.

The objective of the invention is to develop a universal method for producing nanostructured coatings, allowing the use of existing powder materials that are widely used in practice, in particular in powder metallurgy, for applying nanostructured coatings.

The problem is achieved in that in a method for producing a nanostructured coating, which consists in forming a high-speed atomizer of a high-temperature gas stream in a combustion chamber by burning fuel in an oxidizing agent, in feeding into the combustion chamber a starting material, which is a source of nanoparticle formation, in the formation and transfer of a high-temperature gas stream of nanoparticles and their deposition on a substrate in a combustion chamber by exposure to a high-temperature gas flow ny in the gaseous state, and then the gas stream after leaving the combustion chamber is quenched until the temperature below the melting temperature of the starting material. In particular, said gas stream is cooled by mixing it with a cold inert gas stream.

In the proposed method, as a starting material for the formation of nanoparticles, powder materials manufactured by the industry are used. In the combustion chamber, under the influence of a high-temperature gas stream, the powder melts and evaporates. After the gas stream exits the combustion chamber during its sharp cooling, the vapors of the source material, bypassing the liquid state, pass into the solid state. So in a gas stream nanoparticles are formed. When these particles settle on the substrate, a nanostructured coating is formed.

The proposed method is implemented in a high-speed spraying device, schematically represented in figure 1. The device comprises a combustion chamber 1 connected to the nozzle 2. Fuel 3, an oxidizing agent 4, and a powder 5 of a source material serving as a source of nanoparticles are supplied to the combustion chamber 1. Natural gas or propane-butane or acetylene is used as fuel, and compressed air or oxygen is used as an oxidizing agent. If necessary, nitrogen can also be supplied to the combustion chamber 1 together with the powder. As a result of the combustion of the fuel mixture in the combustion chamber, a high-temperature gas stream is generated. Under the influence of this stream, the powder of the starting material melts, evaporates and mixes with the gas stream. The length of the combustion chamber 1 and the parameters of the gas flow are selected so that in the combustion chamber 1 the powder of the starting material has time to evaporate. The gas stream after exiting the combustion chamber 1 is accelerated in the nozzle 2. In this case, the temperature of the gas stream drops rapidly. The length of the nozzle 2 is selected so that, until the nozzle exit cut is reached, the temperature of the gas stream becomes lower than the melting temperature of the starting material. In this case, due to the transience of the process, the vapors of the starting material, bypassing the liquid state, pass into the solid state. Due to this, a gas stream with nanoparticles leaves the nozzle, which, deposited on the substrate, form a nanostructured coating 6.

Figure 2 schematically presents another embodiment of the proposed method. The device implementing the method comprises a combustion chamber 1 with a conical nozzle 2, into which fuel 3, an oxidizing agent 4, and powder material 5 are supplied. An additional nozzle 6 is connected to the housing of the combustion chamber 1, covering the nozzle 2 of the combustion chamber. An inert gas 7, for example nitrogen, is supplied to the nozzle 6, due to which a cold stream of inert gas is formed in the space 8 between the nozzles 2 and 6. In the combustion chamber 1, a stream of high-temperature gas is formed from the combustion products. Under its influence, the powder particles evaporate and mix with the stream. In the nozzle 2, the flow of high-temperature gas is accelerated, while its temperature is intensively reduced. After exiting the nozzle 2, the high-temperature gas stream, being mixed with a cold inert gas stream, is intensively cooled. As its temperature decreases below the melting temperature of the starting material, nanoparticles are formed from the vapors of the starting material, and a nanostructured coating 9 is formed from these particles on the substrate.

Examples of the proposed method

Example 1. The creation of anti-corrosion coatings using chromium. The melting point of chromium is 2130K, and the boiling point is 2945K. Therefore, for the evaporation of particles of chromium powder, the temperature of the gas stream should be of the order of 2700 ... 2900K. It should be noted that, since the partial pressure of chromium vapor in the gas stream will be small, the temperature of the gas stream may be lower than the boiling point of chromium. Therefore, at a temperature of 2700 ... 2800K, chromium particles can completely evaporate. Thus, a gas stream with chromium vapor at the exit from the combustion chamber will have a temperature of about 2700 ... 2800K. In the nozzle, the gas flow temperature should be reduced to approximately 2050 ... 2150K, i.e. 1.3 ... 1.4 times. This is achieved by appropriate selection of nozzle parameters. Creating a coating is carried out using the device shown in Fig.1. Natural gas, oxygen and chromium powder are fed into the combustion chamber.

Example 2. The creation of an anti-corrosion coating based on aluminum. The melting point of aluminum is 933K, and the boiling point is 2673K. In this case, the boiling point is almost 3 times higher than the melting point. Therefore, to implement the proposed method, it is more advisable to use the device shown in figure 2. For the evaporation of particles of aluminum powder, a temperature of 2000 ... 2100K is quite sufficient, therefore, compressed air can be used as an oxidizing agent. Natural gas, compressed air and aluminum powder are supplied to the combustion chamber, and nitrogen is supplied to the space 8 between nozzles 2 and 6. The gas stream with aluminum vapor at the exit from the combustion chamber will have a temperature of the order of 2000 ... 2100K. As the flow passes through the nozzle, its temperature decreases. After exiting the nozzle, the high-temperature gas stream mixes with the nitrogen stream, and its temperature drops to 850 ... 900K.

In the proposed method for obtaining a nanostructured coating, powder materials widely used in industry are used as a starting material. This greatly simplifies and reduces the cost of obtaining nanostructured coatings, which makes it possible to widely use such coatings. This method also allows the production of multilayer nanocomposite materials.

Claims (2)

1. A method of producing a nanostructured coating, comprising forming a high-temperature gas stream in the spray chamber of the atomizer by burning fuel in an oxidizing agent, feeding the source material, which is the source of nanoparticle formation, into the combustion chamber, forming nanoparticles, transferring nanoparticles by high-temperature gas flow and depositing them on a substrate, characterized in that use the source material in the form of a powder in a combustion chamber, the length of which is chosen from the conditions for ensuring the evaporation of the powder and one material by exposure to a high-temperature gas stream, and the powder of the starting material is transferred to a gaseous state, the resulting gas stream after exiting the combustion chamber is accelerated in the nozzle and cooled to form nanoparticles, using a nozzle whose length is selected from the condition of cooling the gas stream to a temperature below the temperature melting of the starting material. 2. The method according to claim 1, characterized in that the cooling of the gas stream is carried out by mixing with a cold stream of inert gas.

Images