RU2593041C2 - Method of gas-dynamic sputtering of anticorrosion coating from a corrosion-resistant composition onto the surface of container for transporting and/or storing spent nuclear fuel, made from high-strength iron with globular graphite - Google Patents

Abstract

FIELD: metal processing.

SUBSTANCE: present invention relates to a method of gas-dynamic sputtering of an anticorrosion coating from a corrosion-resistant composition onto the surface of a container for transporting and/or storing spent nuclear fuel, made from high-strength iron with globular graphite, and can be used for coating the cavity of the container, which serves to receive the spent nuclear fuel. Coating is performed by a device for hypersonic metal coating which contains a combustion chamber and sprinkler. Above device is set to the position for coating application; then a wire material is sprayed, its chemical composition equates the chemical composition of corrosion resistant steel; DC voltage is supplied to the wire material and an electric arc is ignited in the said combustion chamber, which is fed with a bhutan-air, or propane-air or bhutan-propane-air mixture. Then the spray material that is in the midst of this mixture is fed through the said spraying nozzle towards the surfaces of the container subject to coating, wherein the said container is evenly rotated around the axis that is geometrically aligned with its longitudinal axis, and at the same time the device for hypersonic metallization is moved along the said lengthwise axis when applying the coating on the side surfaces of the above container or it is moved radially relative to the longitudinal axis when applying the coating on the end surfaces of the said container, wherein the speed of rotation of the latter and the translational movement of the hypersonic metallization device are interdependent.

EFFECT: to apply an anti-corrosion coating on the surfaces of the elements of a container for transporting and/or storing spent nuclear fuel.

8 cl, 2 dwg

Description

The invention relates to methods for creating a corrosion-resistant coating for a container for transporting and / or storage of spent nuclear fuel (SNF), the casing of which is made of high-strength cast iron with spherical graphite, and can be used to create a corrosion-resistant coating, for example, the surfaces of the cavity of the container, which is used for receiving SNF .

During operation, the container body for transportation and / or storage of spent nuclear fuel is exposed to radiation, cyclic heating to 125 ° C, vibration and shock loads, and treatment with acid solutions, steam and hot water with a temperature of 95 ° C during decontamination.

The main methods of corrosion protection of the surfaces of the inner cavity of the container, which is used to receive spent nuclear fuel, are either to make the container with an inner stainless steel cup (essentially the lining of the inner cavity of the container), or to apply an anti-corrosion coating to the inner surfaces of the cavity. The first option of protection against corrosion complicates the design of the container and significantly increases the cost of the latter.

The corrosion protection option, which involves the application of an anti-corrosion coating, makes it possible to simplify the design of the container and reduce its cost. However, in this case there are problems associated with the difficulty of providing adhesion (the adhesion strength of the coating to the surface to be protected — the base), porosity, and the exclusion of cracking of the coating during cyclic heating (taking into account the difference in temperature coefficients of the coating and the substrate).

A known method for producing nickel coatings on a metal surface according to the patent SU 1028091 A1 (С23С 18/36, 1989), intended for coating the surface of structural materials of parts of equipment of nuclear reactors of the WWER-1000 and RBMK type. The known method includes the activation of the surface in a solution of a reducing agent, followed by chemical precipitation of Nickel from a solution of the same reducing agent. In this case, the stages of activation and deposition of nickel are carried out in the same bath.

However, the coating obtained by this method has insufficient adhesion to the substrate. In addition, nickel, when irradiated in a neutron flux, forms radioactive cobalt-58, as a result of which the radiation situation worsens.

There is a method of protecting intra-reactor elements, in particular, technological channels from destruction, according to patent RU 2195027 CI (G21C 3/02, G21C 3/04, 2002). The invention can be used to protect against local corrosion. According to the known method, a protective coating of a material with a microhardness exceeding the microhardness of the base is applied to the surface to be protected or part thereof. In an embodiment, a diamond-like coating is applied to the surface. In another embodiment, metal carbides, nitrides or borides are applied to the surface. A variant is possible when a diamond-like coating is applied to the surface together with carbides, nitrides, metal borides in various combinations.

The disadvantages of the known method include the difference in temperature coefficients of the coating and the base, high tension in the coating, as well as insufficient adhesion of the high-hard coatings proposed in the specified method with the base.

There is a method of creating a protective coating of intra-reactor elements from destruction due to corrosion and mechanical abrasion, disclosed in patent description RU 2412491 C2 (G21C 3/00, 2011). According to the known method, to protect the intra-reactor elements from destruction, a coating consisting of a sublayer and at least one protective layer is applied to their surface or part of the surface. Moreover, the microhardness of the protective layer is higher than the microhardness of the sublayer, and the microhardness of the sublayer is lower than the microhardness of the oxide of the structural material and has intermediate value between the microhardness of the protective layer and the microhardness of the structural material. The protective coating layer may be in the form of a multilayer structure. In another embodiment, the protective coating layer may be in the form of a multilayer structure, at least one of the layers of which has a greater than the material of construction, but less than the oxide, microhardness. The coating materials used are metals and their compounds based on Al, Ti, Zr, Cr, Cu, Nb, Mo, W, C, N, O, B separately or jointly in various combinations. The method is implemented as follows. In a vacuum chamber equipped with a pumping system, a protected product (substrate) is placed in a movable snap-in so that its surface advances in a stream of ions formed by extended and / or point sources of metal ions placed in the same chamber. An electric voltage is applied to the substrate, which provides the necessary acceleration (energy) of the ions when they bombard the surface for ion cleaning, creating a sublayer and protective hard layers. In the chamber volume, a controlled leakage feeds reaction gas (for example, nitrogen, to form nitride with a microhardness exceeding the microhardness of the structural material and lying in the microhardness range from the value of the structural material and higher). The protective coating is applied in three technological operations carried out sequentially in one vacuum chamber: first, the surface of the substrate is subjected to ion bombardment at voltages of the order of 1-2 kV, after which the voltage is reduced to values of the order of 0.1 kV and the sublayer is deposited, then the reaction layer is introduced into the chamber gas and one or more layers of a protective coating is formed. A multilayer structure is created, for example, by sequentially switching on several ion sources generating ion streams of different metals. The multilayer structure includes layers having a greater than the material of construction, but less than oxide microhardness, which provides less tension in the coating and better adhesion of the coating during cyclic heating.

The disadvantages of the known method of creating a protective coating include a rather high cost.

Known methods for gas-dynamic spraying of coatings of powder materials (Khasuy A. Technology spraying. - M., Engineering, 1975. - S. 288). To improve the quality of coatings, as small as possible powders are used. The sprayed particles are heated in a high-temperature gas (plasma) stream to a melting point and above, accelerated to 100-300 m / s and form a coating of molten or partially molten particles on the surface of the part. The range of used particles in size is 5 - 200 microns.

Known methods of cold gas-dynamic spraying of coatings of powder materials (Alkhimov A.P., Klinkov S.V., Kosarev V.F. and other Cold gas-dynamic spraying. Theory and practice / Ed. Ed. V.M. Fomina. - M .: FIZMATLIT, 2010, S. 310-385).

A known method of gas-dynamic spraying of powder materials according to patent RU 2468123 C2 (C23C 24/04, 2012). The method solves the problem of expanding the technological capabilities of the gas-dynamic spraying method, namely increasing the width of the spraying strip and reducing the cost of spraying on the product. The technical result is achieved by the fact that in the method of gas-dynamic spraying of powder materials, including heating the compressed gas, supplying it to a sound nozzle of constant cross-section, forming a swirling gas stream in the nozzle, supplying particles of powder material to the stream, accelerating it in the nozzle and applying to the surface, according to The invention is sprayed with a flat jet of a gas-powder stream with an opening angle equal to β = 40 ÷ 90º, which is formed by a given configuration of the output section of the sound nozzle.

However, the known method of gas-dynamic spraying of powder materials as well as the method according to patent RU 2412491 has a rather high cost, which is caused by the type of sprayed material. It is known that steel powder with the required particle sizes is 3.5-4 times more expensive than steel wire.

The closest in combination of essential features with the claimed invention is a method of creating an anti-corrosion coating, which is carried out in the manufacture of a container for transportation and / or storage of SNF according to patent RU 2510770 C1 (G21F 5/00, 2014). According to the known method of creating an anti-corrosion coating on the surface of a container made of high-strength cast iron with spherical graphite, a corrosion-resistant composition is applied by gas-dynamic spraying. Corrosion-resistant composition includes chromium and nickel and in its chemical composition corresponds to the composition of corrosion-resistant steel type 08X18H10T. The coating, applied by gasdynamic method to high-strength nodular cast iron, provides higher adhesive strength compared to the coating applied by metallization or thermal spraying or galvanic method, and combines the necessary mechanical properties and resistance to decontamination.

The known method is aimed at solving the problem of creating an anti-corrosion coating on the surfaces of container elements for transportation and / or storage of spent nuclear fuel made of high-strength cast iron with spherical graphite, which would ensure the adaptability of the container with the casing of said material to repeated exposure to decontamination solutions.

However, in the patent specification RU 2510770 C1, the specific characteristics of the method are not disclosed.

The present invention solves the problem of creating a container for the transportation and / or storage of spent nuclear fuel with a housing made of ductile iron with spherical graphite by gas dynamic spraying.

This problem is solved due to the fact that in the known method of gas-dynamic spraying of an anticorrosive coating from a corrosion-resistant composition on the surface of container elements for transporting and / or storing spent nuclear fuel made of high-strength cast iron with spherical graphite, the coating is sprayed using hypersonic metallization containing a combustion chamber and a spray nozzle. The said agent is set in the position for coating, and then the wire material corresponding to the chemical composition of the corrosion-resistant steel is sprayed, for which a direct current voltage is connected to the wire material and an electric arc is ignited in the said combustion chamber into which butane-air is supplied, or propane-air, or butano-propane-air mixture. Then, the sprayed material in the medium of this mixture is fed through said spray nozzle towards the coated surface of the container. Moreover, the said container is uniformly rotated around an axis geometrically aligned with its longitudinal axis, and the means for hypersonic metallization is simultaneously progressively moved along the said longitudinal axis when spraying the coating onto the side surfaces of the said container or radially with respect to this longitudinal axis when spraying the coating on the end surfaces mentioned container. Moreover, the rotational speeds of the last and translational movements of the means for hypersonic metallization are interconnected.

Along with this, the container is rotated at a speed at which the peripheral speed of movement of the coated surface during coating spraying is 0.3-0.4 m / s relative to the means for hypersonic metallization, which is 2.5-3.5 mm per container revolution .

In addition, the spray nozzle is located at a distance of 120-150 mm from the surface provided with the coating and is oriented towards the latter.

Spraying is carried out in several passes.

In an embodiment, the spraying is carried out in a vertical position of the container.

In another embodiment, the spraying is carried out in a horizontal position of the container.

Along with this, the corrosion-resistant composition in its chemical composition corresponds to the composition of the corrosion-resistant steel 08X18H10T.

In addition, the corrosion-resistant composition in its chemical composition may correspond to the composition of the corrosion-resistant steel 08X19H9T.

The technical result of the use of the invention is to create an effective method of applying a corrosion-resistant coating on the surface of the base (substrate) made of high-strength cast iron with spherical graphite, which provides a wear-resistant coating with increased adhesion to the base material, with virtually no porosity operating under radiation exposure , cyclic heating and exposed to repeated exposure to decontamination solutions.

In FIG. 1 schematically shows an installation for gas-dynamic spraying of an anticorrosive coating with a container installed on it for transportation and / or storage of spent nuclear fuel, general view, longitudinal section (the dash-dotted line shows the surfaces of the container provided with an anti-corrosion coating applied by gas-dynamic spraying); in FIG. 2 is a diagram of a hypersonic metallization process, a longitudinal section showing a combustion chamber, a Laval supersonic nozzle, sprayed wire material and gas mixture supply pipes.

In an embodiment of the invention, the method is implemented when creating an anti-corrosion coating, for example, a container 1, intended for transportation and / or storage of SNF of VVER-1000 reactors, the feature of which (i.e., SNF) is intense heat generation and intense γ-radiation and neutron radiation. The container contains a housing including a molded glass with a bottom "a". The glass with the bottom is made in one piece from high-strength cast iron with spherical graphite. The glass contains an anti-corrosion coating 2 applied on its internal surfaces (the surface of the internal cavity of the glass, which is used for receiving SNF) and on a part of its external surfaces by gas-dynamic spraying (hypersonic metallization), which is a corrosion-resistant composition. On the outer surfaces of the glass anticorrosive coating 2 is applied, for example, at the installation sites of the protective sealing caps of the glass and the end shockproof damper (not shown). In an embodiment of the invention, the corrosion resistant composition

It includes nickel and chromium and, in its chemical composition, corresponds, for example, to the composition of corrosion-resistant steel type 08X18H10T.

In an embodiment of the method, the spraying is carried out in the horizontal position of the container 1 using the device 3, which ensures, by means of an appropriate drive (not shown), the rotation of the container around axis 4, geometrically aligned with the longitudinal axis of the container. The spraying is applied using means 5 for hypersonic metallization. The latter includes a combustion chamber 6 of the gas mixture used as a transport gas, a spray nozzle 7, which is made in the form of a supersonic Laval nozzle, and a mechanism 8 for supplying atomized material (wire) 9. In an embodiment of the invention, a wire with a diameter of, for example, 2 mm of stainless steel 08X18H10T. A variant is possible in which 08X19H9T stainless steel wire is used. The spraying material supply mechanism 8 has an electromechanical drive (not shown in the drawing), which supplies two wires 9 electrically isolated from one another from two channels, each of which is connected to the corresponding pole of a DC power source (not shown in the drawing). The gas mixture is fed into the combustion chamber through the nozzles 10. As the gas mixture can be used butane-air, or propane-air, or butane-propane-air mixture. In an embodiment of the invention, a compressed air network and butane (propane) with a pressure of 0.6 MPa are used to operate the means 5. Air consumption up to 1.5 m ³ / min, butane-propane consumption ~ 0.011 kg / h. The tool 5 is made with the possibility of its separate movement along and radially relative to the longitudinal axis 4 by means of movable equipment (not shown in the drawing) with the possibility of feeding the sprayed material 9 in the direction to the surface provided with the coating. An external support separate from the container (not shown in the drawing) is used to fasten the movable equipment.

In an embodiment of the invention, the proposed method for creating an anti-corrosion coating of a container for transportation and / or storage of spent nuclear fuel is implemented as follows.

The container 1 is placed in a horizontal position on the device 3, providing rotation of the container around the longitudinal axis 4. Then the surface of the container, provided with a coating, is preliminarily subjected to dry jet-abrasive treatment.

Inside the volume of the cavity used to receive SNF, hypersonic metallization means 5 is placed in a predetermined position with the possibility of its separate movement along and radially relative to the longitudinal axis 4 of the container by means of movable equipment (not shown in the drawing) with the possibility of feeding the sprayed material in the direction to the coating provided surface.

In this case, the spray nozzle 7 is positioned at a distance of 120-150 mm from the surface provided with the coating and is oriented towards the latter (essentially normal to the surface).

The sprayed material, which is two separate stainless steel wires, for example, 08X18H10T, is connected respectively to the poles of a DC power source and, using the spray material supply mechanism 8, wire 9 (essentially a spray material) is fed into the gas mixture combustion chamber 6. In the combustion chamber between the wires 9 ignite (excite) an electric arc. At the same time, for example, a butane-propane-air mixture is fed into the combustion chamber 6 of the gas mixture. The butane-propane-air mixture ignites, the wire begins to melt. A mixture of gas and stainless steel particles forms in the combustion chamber. Using a supersonic nozzle 7 of Laval, the sprayed material 9 in a butane-propane-air mixture is fed towards the surface of the container to be coated (essentially a mixture of gas and stainless steel particles in the form of a jet is ejected through a supersonic nozzle 7 of Laval onto the protected surface of the container). The maximum working current during the implementation of the method is ~ 380 A.

In the process of spraying a corrosion-resistant composition, the container is rotated uniformly around an axis 4 geometrically aligned with its longitudinal axis using an appropriate drive.

At the same time, the means for hypersonic metallization 5 with the help of a suitable drive are translationally moved along the longitudinal axis 4 when coating, for example, on the side surface of the container or - radially with respect to the longitudinal axis 4 when coating, for example, on the surface of the bottom of the container. In this case, the rotation speeds of the container 1 and the translational movement of the means 5 for hypersonic metallization are interconnected. In an embodiment, the container is rotated at a speed at which the coated

the surface of the container moves with a peripheral speed of 0.3-0.4 m / s, while the tool 5 is moved with a feed of 2.5-3.5 mm per revolution of the container.

Spraying (i.e. coating) is carried out in several passes. This is due to the fact that the sprayed corrosion-resistant composition, in comparison with high-strength cast iron with spherical graphite, has low thermal conductivity and otherwise, overheating and delamination of the latter can occur.

In an embodiment of the invention, the optimum thickness of the coating sprayed in one pass, for example, 60 microns.

Corrosion-resistant coating on the protected outer surfaces of the container is applied in a similar manner after a corresponding reinstallation of the means 5 for hypersonic metallization.

The main characteristics of the anti-corrosion coating obtained using this method:

- adhesion strength of the coating to the cast-iron surface up to 55 MPa;

- porosity is practically not detected;

- the possibility of cracking is absent;

- the number of decontamination of the coated surface is not limited;

- the service life corresponds to the service life of the container;

- maintainability - provided.

These characteristics are achieved, in particular, due to the fact that:

- the jet velocity at the exit of the supersonic nozzle 7 of Laval reaches the Mach number ~ 3 (~ 1200 m / s);

- the flight speed of the particles forming the coating is about 500 m / s;

- the angle of the jet does not exceed 10 degrees;

- the velocity head of the flow of a mixture of gas and stainless steel particles is three times higher than with plasma spraying.

Thus, due to the design features, the proposed method of creating an anti-corrosion coating of the container body for transportation and / or storage of spent nuclear fuel, which is made of high-strength cast iron with spherical graphite, provides a wear-resistant coating with increased adhesion to the base material, with almost no porosity operating under conditions radiation exposure, cyclic heating and exposed repeatedly to decontamination solutions.

Claims (8)

1. The method of gas-dynamic spraying of a corrosion-resistant coating from a corrosion-resistant composition on the surface of a container for transporting and / or storage of spent nuclear fuel made of high-strength cast iron with spherical graphite, characterized in that the coating is sprayed using means for hypersonic metallization containing a combustion chamber and a spray nozzle, wherein said means is set to the coating position, and then the wire material is sprayed, responding which in its chemical composition is the chemical composition of corrosion-resistant steel, for which a direct current voltage is connected to the wire material and an electric arc is ignited in the said combustion chamber, into which a butane-air or propane-air or butane-propane-air mixture is supplied, then the sprayed material in the medium of this mixture is fed through the said spray nozzle in the direction to the coated surfaces of the container, while the said container is uniformly rotated about an axis, geometrically aligned with its longitudinal axis, and the means for hypersonic metallization is simultaneously progressively moved along the said longitudinal axis when spraying the coating on the side surfaces of the said container or radially with respect to this longitudinal axis when spraying the coating on the end surfaces of the said container, the rotational speeds of the last and translational movements means for hypersonic metallization are interconnected. 2. The method according to p. 1, characterized in that the container is rotated at a speed at which the peripheral speed of movement of the coated surface during coating spraying is 0.3-0.4 m / s relative to the means for hypersonic metallization, which is moved with a feed of 2 5-3.5 mm per container turn. 3. The method according to p. 1, characterized in that the spray nozzle is located at a distance of 120-150 mm from the surface to be coated and oriented in the direction of the latter. 4. The method according to p. 1, characterized in that the spraying is carried out in several passes. 5. The method according to p. 1, characterized in that the spraying is carried out in the vertical position of the container. 6. The method according to p. 1, characterized in that the spraying is carried out in a horizontal position of the container. 7. The method according to p. 1, characterized in that the corrosion-resistant composition in its chemical composition corresponds to the composition of corrosion-resistant steel 08X18H10T. 8. The method according to p. 1, characterized in that the corrosion-resistant composition in its chemical composition corresponds to the composition of corrosion-resistant steel 08X19H9T.

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