A kind of corrosion-resistant nickel coating for ductile cast iron spent fuel storage tank and laser cladding preparation device and method

Abstract

The application provides a corrosion-resistant nickel coating for a nodular cast iron spent fuel storage tank and a laser cladding preparation device and method. The corrosion-resistant nickel coating is a high-purity nickel cladding layer obtained by using high-purity nickel powder to perform cladding on a nodular cast iron spent fuel storage tank substrate through a laser cladding technology. The nickel coating prepared by the laser cladding method can completely replace the electroplating nickel process used in the spent fuel storage tank at present, reduces the environmental pollution caused by electroplating, and improves the bonding force between the coating and the substrate and reduces the porosity, so that the service life of the coating can be effectively improved.

Description

An apparatus and method for preparing corrosion-resistant nickel coating and laser cladding for ductile iron spent fuel storage tanks. Technical Field

[0001] This invention relates to the field of nuclear power spent fuel reprocessing technology, and more particularly to an apparatus and method for preparing a corrosion-resistant nickel coating and laser cladding for ductile iron spent fuel storage tanks. Background Technology

[0002] Currently, there are four main types of large spent fuel storage and transportation containers internationally: ductile iron containers, stainless steel lead-shielded containers, carbon steel multi-layered wrapped containers, and forged steel containers. With the increase in my country's installed nuclear power capacity and operational years, spent fuel processing capacity has constrained the effective operation of nuclear power plants, leading to a surge in demand for spent fuel storage and transportation containers. Ductile iron is a casting material with excellent mechanical properties and corrosion resistance. Spent fuel storage and transportation containers cast from ductile iron have good radiation shielding capabilities, high integrity, and safety. The process flow and manufacturing cycle are short, and the manufacturing cost can be reduced by more than one-third compared to steel. A 100-ton container can hold approximately 20 tons of spent nuclear fuel with high storage and transportation efficiency, and it has advantages such as high yield strength ratio and better corrosion resistance than carbon steel. Meanwhile, breakthroughs have been achieved in the casting technology of 100-ton-class ductile iron spent fuel tanks in China, making the large-scale use of 100-ton-class ductile iron spent fuel tanks possible.

[0003] However, due to the corrosive effect of spent fuel on ductile iron, there is an urgent need to solve the corrosion problem of the inner wall of ductile iron tanks. Existing technology achieves corrosion protection by electroplating pure nickel onto the inner wall of the tank. However, the adhesion between the electroplated nickel layer and the tank body is limited, and the plating layer has pores, resulting in insufficient assessable effective lifespan of the nickel plating layer, which affects the overall lifespan of 100-ton-class spent fuel ductile iron tanks. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a corrosion-resistant nickel cladding layer for ductile iron spent fuel storage tanks, along with a laser cladding preparation apparatus and method. The invention primarily utilizes laser cladding to prepare a pure nickel cladding layer that forms a metallurgical bond with the ductile iron tank body. This results in a dense, metallurgically defect-free, and corrosion-resistant cladding layer that is less prone to corrosion channels, thereby improving the corrosion resistance of ductile iron spent fuel storage tanks and providing a technical foundation for the industrial application of 100-ton-class ductile iron spent fuel storage tanks.

[0005] The technical means employed in this invention are as follows:

[0006] A corrosion-resistant nickel coating for ductile iron spent fuel storage tanks, wherein the corrosion-resistant nickel coating is a high-purity nickel cladding layer obtained by laser cladding technology, which uses high-purity nickel powder to clad onto the substrate of the ductile iron spent fuel storage tank.

[0007] Furthermore, the chemical composition and mass percentage of the high-purity nickel powder are as follows: Ni: >99.5%; Fe: ≤0.10%; Si: ≤0.30%; Cr: ≤0.05%; O: ≤0.10%; others: ≤0.05%; and the powder particle size range is 120-270 mesh.

[0008] The present invention also provides a laser cladding preparation device for corrosion-resistant nickel coating of ductile iron spent fuel storage tanks, including a turntable and a laser assembly and a cross carriage fixed on the ground. A pit is opened in the ground, the turntable is installed at the bottom of the pit, and the spent fuel storage tank is placed on the turntable. The turntable is used to realize the rotation of the spent fuel storage tank.

[0009] The laser cladding equipment includes a laser cladding head, a laser connected to the laser cladding head via an optical fiber, and a powder feeder connected to the laser cladding head via a powder feeding pipe. The cross carriage includes a support, a horizontal arm, and a vertical arm. The horizontal arm is mounted on the support, and the vertical arm is slidably connected to the horizontal arm. The laser cladding head is connected to the vertical arm. The horizontal arm enables the vertical arm to move the laser cladding head laterally, and the vertical arm enables the laser cladding head to move up and down reciprocatingly.

[0010] This invention also provides a laser cladding method for preparing a corrosion-resistant nickel coating for ductile iron spent fuel storage tanks. Using the aforementioned laser cladding apparatus, the method includes a laser cladding process and a heat treatment process, specifically comprising the following steps:

[0011] Step 1: During cladding, after cleaning the cladding surface of the spent fuel storage tank, install the spent fuel storage tank on the turntable plane in the pit, align it, and then fix it.

[0012] Step 2: Adjust the horizontal and vertical arms of the cross slide to the appropriate positions to ensure that the distance between the laser cladding head and the surface to be cladding meets the cladding requirements. Adjust the turntable speed so that the linear velocity of the spent fuel storage tank meets the cladding requirements. During cladding, the turntable rotates at a constant speed, the vertical arm of the cross slide moves vertically up and down at a constant speed, and the laser cladding head performs spiral cladding on the surface of the spent fuel storage tank.

[0013] Step 3: After the cladding is completed, the entire body of the spent fuel tank is heat-treated. After the heat treatment is completed, it is slowly cooled to room temperature with the furnace.

[0014] Furthermore, in the laser cladding process, the laser used has a rated power of 6kW and a spot diameter of Φ4.9mm;

[0015] The cladding layer is prepared in two layers. The parameters for the first cladding layer are: laser power 1.8-1.9kW, spot scanning speed 18-19mm / s, powder feed rate 18-22g / min, and cladding layer thickness 0.5-0.6mm; Ni purity of the cladding layer is >94%.

[0016] The parameters for the second cladding layer are as follows: laser power 1.9–2.0 kW, spot scanning speed 17–18 mm / s, powder feed rate 20–24 g / min, cladding layer thickness 0.6–0.7 mm, and Ni purity of the cladding layer >99%.

[0017] Furthermore, in the heat treatment process, the holding temperature is 480–520°C, and the holding time is 2–4 hours.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] 1. The present invention provides a dense and non-porous nickel cladding layer prepared by laser cladding, which forms a metallurgical bond with the ductile iron spent fuel storage tank substrate.

[0020] 2. Compared with existing electroplated pure nickel layers, the nickel coating obtained by the laser cladding process of this invention has higher bonding strength, extremely low porosity, and better resistance to cavitation erosion. Therefore, the cladding layer has the following significant characteristics:

[0021] (1) The laser-clad nickel coating has good adhesion to the ductile iron matrix: the bonding strength is >140MPa;

[0022] (2) The two-layer cladding process design ensures that the second layer (surface layer) has high nickel purity and high hardness: nickel purity > 99%, hardness 150-180HV.

[0023] (3) The nickel coating prepared by laser cladding can completely replace the electroplating nickel process currently used in spent fuel storage tanks, reducing the environmental pollution caused by electroplating. Moreover, the improved bonding strength between the coating and the substrate and the reduced porosity can effectively improve the service life of the coating.

[0024] (4) The method of the present invention can be widely applied to corrosion protection of ductile iron parts under corrosion conditions, and local repair can be carried out by re-cladding after local failure.

[0025] Based on the above reasons, this invention can be widely applied in fields such as spent nuclear fuel reprocessing. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 is a schematic diagram of laser cladding on the ductile iron spent fuel storage tank of the present invention.

[0028] In the diagram: 1. Laser equipment; 2. Cross carriage; 3. Laser cladding head; 4. Turntable; 5. Ground; 6. Spent fuel storage tank. Detailed Implementation

[0029] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0032] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0033] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0034] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation besides the orientation of the device as described in the figures. For example, if the device in the figures is inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0035] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0036] The purpose of this invention is to provide a corrosion-resistant nickel cladding coating and laser cladding preparation apparatus and method for ductile iron spent fuel storage tanks. The invention utilizes laser cladding to prepare a pure nickel cladding layer that forms a metallurgical bond with the ductile iron tank body. This results in a dense, metallurgically defect-free, and corrosion-resistant cladding layer that is less prone to corrosion channels, thus improving the corrosion resistance of ductile iron spent fuel storage tanks and providing a technical foundation for the industrial application of 100-ton-class ductile iron spent fuel storage tanks. Simultaneously, it replaces the existing electroplating nickel process used for spent fuel storage tanks, reducing the environmental pollution caused by electroplating. Furthermore, if the cladding layer fails locally, it can be repaired by re-laser cladding.

[0037] This invention provides a corrosion-resistant nickel coating and laser cladding preparation apparatus and method for ductile iron spent fuel storage tanks, thereby obtaining a metallurgically bonded, dense nickel coating on the ductile iron spent fuel tank body.

[0038] High-purity nickel cladding layer is obtained by cladding high-purity nickel powder onto the substrate of ductile iron spent fuel storage tank using laser cladding technology.

[0039] The chemical composition and mass percentage of laser-clad high-purity nickel powder are as follows: Ni: >99.5%; Fe: ≤0.10%; Si: ≤0.30%; Cr: ≤0.05%; O: ≤0.10%; others: ≤0.05%; powder particle size range is 120-270 mesh.

[0040] This invention discloses a laser cladding method for preparing a corrosion-resistant nickel coating for ductile iron spent fuel storage tanks, comprising a laser cladding process and a heat treatment process. In the laser cladding process, the laser used has a rated power of 6kW and a spot diameter of Φ4.9mm. The cladding layer is prepared in two layers. The parameters for the first layer are: laser power 1.8–1.9kW, spot scanning speed 18–19mm / s, powder feed rate 18–22g / min, and cladding layer thickness 0.5–0.6mm; the Ni purity of the cladding layer is >94%. The parameters for the second layer are: laser power 1.9–2.0kW, spot scanning speed 17–18mm / s, powder feed rate 20–24g / min, cladding layer thickness 0.6–0.7mm, and Ni purity of the cladding layer is >99%. In the heat treatment process, the holding temperature is 480–520℃, and the holding time is 2–4 hours.

[0041] The laser cladding preparation device of the present invention includes a turntable, a laser complete set of equipment 1 and a cross slide 2 fixed on the ground 5. A pit is opened on the ground 5, the turntable 4 is installed at the bottom of the pit, and the spent fuel storage tank 6 is placed on the turntable 4. The turntable 4 is used to realize the rotation of the spent fuel storage tank 6.

[0042] The laser cladding equipment 1 adopts existing equipment, including a laser cladding head 3, a laser, a powder feeder, a control system, etc. The laser cladding head 3 and the laser are connected by optical fiber, the laser cladding head 3 and the powder feeder are connected by a powder feeding pipe, and the laser and the control system, and the powder feeder and the control system are connected by control cables. The cross slide 2 includes a bracket, a horizontal arm and a vertical arm. The horizontal arm is mounted on the bracket, the vertical arm is slidably connected to the horizontal arm, and the laser cladding head 3 is connected to the vertical arm. The horizontal arm enables the vertical arm to move the laser cladding head 3 laterally, and the vertical arm enables the laser cladding head 3 to move up and down reciprocally.

[0043] Specific implementation steps and methods:

[0044] The laser-clad nickel coating described in this example has good adhesion to the substrate and extremely low porosity, and can withstand long-term vibration cavitation corrosion. It has wide adaptability to corrosion-resistant conditions of ductile iron parts, and is particularly suitable for corrosion-resistant treatment of ductile iron spent fuel storage tanks.

[0045] The main parameters for this example are as follows:

[0046] 1. Composition of clad pure nickel powder: Ni: 99.62%; Fe: 0.05%; Si: 0.18%; Cr: 0.03%; O: 0.075%; Others: 0.045%;

[0047] 2. Powder particle size: 120~270 mesh;

[0048] 3. Implementation Method: During cladding, the cladding surface of the spent fuel storage tank is cleaned and then installed on a turntable plane in the pit, aligned and fixed. The horizontal and vertical arms of the cross slide are adjusted to appropriate positions to ensure that the distance between the cladding head and the surface to be cladding meets the cladding requirements. The turntable speed is adjusted so that the linear velocity of the spent fuel storage tank meets the cladding requirements. During cladding, the turntable rotates at a constant speed, and the vertical arm of the cross slide moves vertically up and down at a constant speed. The laser cladding head performs spiral cladding on the surface of the tank.

[0049] The parameters for the first cladding layer are: laser power 1.85kW, spot scanning speed 19mm / s, powder feeder rate 19g / min, and cladding layer thickness 0.5~0.6mm; the parameters for the second cladding layer are: laser power 1.95kW, spot scanning speed 18mm / s, powder feeder rate 21g / min, and cladding layer thickness 0.6~0.7mm.

[0050] After the cladding is completed, the spent fuel tank body is subjected to heat treatment at a temperature of 490±10℃ for 2.5 hours, and then slowly cooled to room temperature with the furnace.

[0051] The performance test results of laser cladding nickel coating are shown in Table 1 below.

[0052] Table 1 Performance test results of laser-clad nickel coatings in the examples.

[0053]

[0054] In this embodiment, a nickel cladding with a purity of 99.16% was prepared by laser cladding on a ductile iron spent fuel tank. The bonding strength between the cladding and the substrate was 148 MPa. The cladding structure was dense and had good resistance to cavitation erosion.

[0055] This invention achieves a nickel coating with a bonding strength >140MPa, nickel purity >99%, and hardness of 150-180HV on ductile iron spent fuel tanks through laser cladding. This method can completely replace the electroplating nickel process currently used in spent fuel storage tanks, reducing the environmental pollution caused by electroplating. Furthermore, the improved adhesion between the coating and the substrate, along with reduced porosity, effectively extends the coating's service life. Simultaneously, this method can be widely applied to corrosion protection of ductile iron parts under corrosive conditions, and localized repairs can be achieved through re-laser cladding after partial failure.

[0056] According to the present invention, laser cladding of a Φ1000×2000mm spent fuel tank sample has been completed, and the performance data testing has met the technical requirements.

[0057] The design and implementation of this invention can completely replace the electroplating nickel process currently used in spent fuel storage tanks, reducing environmental pollution from electroplating and effectively solving the corrosion problem of ductile iron tanks caused by spent fuel. It can be widely applied to corrosion protection of ductile iron parts under corrosive working conditions, and localized repairs can be performed through laser cladding after partial failure.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A laser cladding method for preparing a corrosion-resistant nickel coating for ductile iron spent fuel storage tanks, characterized in that, The corrosion-resistant nickel cladding is a high-purity nickel cladding layer obtained by laser cladding technology, using high-purity nickel powder to clad onto the ductile iron spent fuel storage tank substrate. The nickel cladding is dense and non-porous, forming a metallurgical bond with the ductile iron spent fuel storage tank substrate. The nickel cladding exhibits higher bonding strength, extremely low porosity, and better cavitation erosion resistance. The laser-clad nickel cladding has excellent adhesion to the ductile iron substrate: bonding strength... 140MPa; The laser cladding preparation method for the corrosion-resistant nickel coating of ductile iron spent fuel storage tank uses a laser cladding preparation device, which includes a turntable, a complete set of laser equipment and a cross slide fixed on the ground. A pit is opened in the ground, the turntable is installed at the bottom of the pit, and the spent fuel storage tank is placed on the turntable. The turntable is used to realize the rotation of the spent fuel storage tank. The complete set of laser equipment includes a laser cladding head, a laser connected to the laser cladding head through an optical fiber, and a powder feeder connected to the laser cladding head through a powder feeding pipe. The cross slide includes a support, a horizontal arm and a vertical arm. The horizontal arm is installed on the support, the vertical arm is slidably connected to the horizontal arm, and the laser cladding head is connected to the vertical arm. The horizontal arm enables the vertical arm to move the laser cladding head laterally, and the vertical arm enables the laser cladding head to move up and down reciprocally. The laser cladding preparation method for the corrosion-resistant nickel coating of ductile iron spent fuel storage tanks includes a laser cladding process and a heat treatment process, specifically including the following steps: Step 1: During cladding, after cleaning the cladding surface of the spent fuel storage tank, the tank is installed on a turntable plane in a pit, aligned, and fixed; Step 2: Adjust the horizontal and vertical arms of the cross slide to appropriate positions to ensure that the distance between the laser cladding head and the surface to be clad meets the cladding requirements, adjust the turntable speed to ensure that the linear velocity of the spent fuel storage tank meets the cladding requirements, and during cladding, the turntable rotates at a uniform speed, the vertical arm of the cross slide moves vertically up and down at a uniform speed, and the laser cladding head performs spiral cladding on the surface of the spent fuel storage tank; Step 3: After cladding, the entire tank body of the spent fuel tank is heat treated, and after heat treatment, it is slowly cooled to room temperature with the furnace; the cladding layer is prepared in two layers, the first cladding layer Ni purity... 99%; While ensuring the second cladding layer has high nickel purity, it also has high hardness: nickel purity 99%, hardness 150~180HV; the chemical composition and mass percentage of the high-purity nickel powder are: Ni: 99.5%； Fe: ≤0.10%; Si: ≤0.30%; Cr: ≤0.05%; O: ≤0.10%; Other: ≤0.05%; powder particle size range is 120~270 mesh; in the laser cladding process, the laser used has a rated power of 6kW and a spot diameter of Φ4.9mm; the parameters for the first cladding layer are: laser power 1.8~1.9kW, spot scanning speed 18~19mm / s, powder feeder rate 18~22g / min, cladding layer thickness 0.5~0.6mm; Ni purity of the cladding layer 94%; The parameters for the second cladding layer are: laser power 1.9~2.0kW, spot scanning speed 17~18mm / s, powder feed rate 20~24g / min, cladding layer thickness 0.6~0.7mm, and Ni purity of the cladding layer. 99%; In the heat treatment process, the holding temperature is 480~520℃ and the holding time is 2~4 hours.

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