A kind of water turbine surface coating on-line quick maintenance of cavitation erosion resistant wire and on-line quick maintenance method based thereon

Abstract

The present application relates to the technical field of surface strengthening in water conservancy and power industry, and particularly relates to a kind of water turbine surface coating on-line fast maintenance of cavitation erosion resistant wire and on-line fast maintenance method based on it.The present application is specially made of nickel-chromium band coated high-tungsten flux-cored wire, and the main components of the wire are W, Cr, Si, B, Mn, Nb and the balance of Ni, which can be adapted to handheld laser welding machine operation.The supporting maintenance method is carried out in sequence, including failure layer polishing and shaping, cleaning and impurity removal, 150-250 DEG C preheating pretreatment, then using handheld laser welding machine with the wire, through limiting laser power, welding speed, wire feeding speed and overlap amount parameters, layer-by-layer cladding repair, finally through heat preservation and slow cooling, surface polishing and shaping to complete the maintenance.The present application can realize on-line in-situ fast repair of water turbine component cavitation erosion damage, and the cladding layer has dense structure, high bonding strength, excellent cavitation erosion and wear resistance, effectively solves the problem of low repair efficiency and on-site maintenance in prior art, and is suitable for on-site maintenance of hydroelectric equipment.

Description

Technical Field

[0001] This invention relates to the field of surface strengthening technology in the water conservancy and hydropower industry, and in particular to a cavitation-resistant wire material for online rapid maintenance of the surface coating of a water turbine and an online rapid maintenance method based thereon. Background Technology

[0002] During the long-term service of hydroelectric power equipment, cavitation damage to flow components caused by the coupled effects of water cavitation, sediment abrasion, and media corrosion is a core problem leading to the failure of core components such as turbine blades, guide vanes, and runners, resulting in decreased unit power generation efficiency and increased operation and maintenance costs. Traditional protective technologies such as supersonic spraying and welding have shortcomings such as weak adhesion, high coating porosity, and large thermal deformation, making it difficult to meet the long-term protection requirements under harsh operating conditions. Laser cladding technology, with its advantages of metallurgical bonding, dense structure, and low heat-affected zone, has become the mainstream process for preparing high-performance anti-cavitation coatings and is widely used in industrial protection, especially in hydroelectric turbines.

[0003] The iterative upgrade of laser cladding material systems for turbine surfaces is the core key to improving the performance of anti-cavitation coatings. Currently, the most mature applications are cobalt-based and nickel-based alloy coatings. Among them, the Stellite series of cobalt-based alloys possesses excellent strength, toughness, and impact fatigue resistance, as well as outstanding resistance to high-temperature cavitation erosion, and has been used for a long time in core components such as turbine runners and guide vanes. Nickel-based alloys combine corrosion resistance and wear resistance, making them suitable for marine acid and alkali corrosion coupled with cavitation erosion conditions, and thus have wider applicability.

[0004] In recent years, high-entropy alloys and cermet composite coatings have become a cutting-edge research direction. High-entropy alloys such as CoCrFeNi and CoCrFeNiMn effectively suppress the initiation and propagation of cavitation cracks by relying on the high-entropy effect, fine grain strengthening, and solid solution strengthening mechanisms, resulting in cavitation wear rates far lower than those of conventional stainless steel and traditional alloy coatings. Furthermore, doping with nano-ceramic particles such as WC and TiC can achieve a complementary advantage between the tough matrix and the hard reinforcing phase, significantly improving the coating's hardness and impact resistance. This solves the problem of single coatings being unable to simultaneously achieve both hardness and toughness, making it the optimal material system for anti-cavitation coatings at present.

[0005] At the application level, current laser cladding coatings mostly use powder materials. Laser cladding equipment, along with corresponding auxiliary devices, is used to prepare laser cladding coatings for turbine components. The cladding layer is then processed before being put into online use. Although the cavitation erosion resistance of the cladding layer is significantly improved compared to conventional stainless steel and traditional alloy coatings, after a period of online use, localized failures inevitably occur in certain easily cavitation-corroded areas of the parts. During regular maintenance and repair, it is required to be able to perform rapid online repairs to restore the local performance of the parts and prevent the failure site from expanding rapidly. However, laser cladding equipment using powder materials is limited by its complexity, large size, and inconvenience in movement, making rapid online repair impossible. Summary of the Invention

[0006] To address the issue that existing turbine flow components are susceptible to localized failure due to the coupled effects of cavitation erosion, wear, and corrosion, traditional protective processes offer limited protection. Furthermore, existing powder laser cladding equipment is bulky, immobile, and unable to achieve rapid online repair of turbine components on-site, failing to meet the engineering requirements of rapid on-site maintenance, damage containment, and reduced operation and maintenance costs. This invention provides a cavitation-resistant wire material for rapid online maintenance of turbine surface coatings and a method based on it for rapid online maintenance.

[0007] Therefore, the present invention provides the following technical solution: A corrosion-resistant wire for online rapid maintenance of the surface coating of a water turbine, the wire being a flux-cored welding wire structure, made of nickel-chromium alloy strip encased with internal flux powder, the chemical composition of the wire, by element mass percentage, includes W: 40~44%, Cr: 11~13%, Si: 1.8~2.2%, B: 0.8~1.2%, Mn: 1.6~2.2%, Nb: 1.0~1.6%, with the balance being Ni.

[0008] Furthermore, the thickness of the nickel-chromium alloy strip is 0.3~0.6mm.

[0009] Furthermore, the outer diameter of the wire is Ø1.2mm, Ø1.6mm or Ø2.0mm.

[0010] A method for online rapid maintenance based on the cavitation-resistant wire material for online rapid maintenance of turbine surface coating includes a surface pretreatment process, a laser welding cladding process, and a post-treatment process performed sequentially. The surface pretreatment process includes: A1. Remove the failed coating from the area to be repaired by mechanical or manual grinding, and make a smooth transition at the boundary between the area to be repaired and the intact area of ​​the component; A2. Clean the area to be repaired and the surrounding area using a volatile cleaning agent; A3. Use portable heating equipment to preheat the maintenance area; The laser welding cladding process includes: B1. Use a portable handheld laser welding machine in conjunction with cavitation-resistant wire to perform cladding repair on the area to be repaired; The post-processing steps include: C1. After the cladding repair is completed, the cladding area is subjected to heat preservation and slow cooling treatment until it reaches room temperature; C2. The surface of the cladding layer after the heat preservation and slow cooling treatment is repaired by manual or mechanical grinding so that the surface size and morphology of the component meet the requirements for service use.

[0011] Furthermore, in step A3, the preheating temperature is controlled at 150~250℃.

[0012] Furthermore, in step B1, the laser welding cladding process parameters are: laser power 1350~1800W, welding speed 12~20mm / s, wire feed speed 2.0~4.0m / min, cladding overlap 50~70%, and single-layer cladding thickness 0.8~1.0mm.

[0013] Furthermore, in step A2, the volatile cleaning agent is anhydrous ethanol or acetone, used to remove oil, dust and oxidized impurities from the surface of the area to be repaired.

[0014] Furthermore, the portable heating device is a portable electric heating belt.

[0015] Furthermore, in step B1, during the cladding process, the surface condition is checked after each layer of cladding is completed. The next layer of laser welding cladding is carried out only after there are no cracks or pore defects.

[0016] Furthermore, the heat preservation and slow cooling process involves wrapping the cladding area with portable on-site heat preservation cotton to achieve slow cooling and eliminate residual stress from the cladding process.

[0017] Advantages and positive effects of the present invention: This invention utilizes a high-tungsten-content nickel-chromium-based flux-cored cavitation-resistant wire, combined with a suitable handheld laser online repair process, to achieve rapid in-situ repair of cavitation damage in turbine flow components. The wire employs a nickel-chromium alloy strip coated with a specially formulated high-tungsten powder system. Through precise proportioning of W, Cr, Nb, B, Si, and Mn alloying elements, a high-hardness, high-toughness, and cavitation-resistant Ni-Cr-W alloy metallurgical reinforcement layer can be generated in situ during laser welding cladding. The high W content significantly enhances the coating's resistance to cavitation impact and erosion wear; Cr and Nb elements refine the microstructure and inhibit crack propagation; B and Si elements improve cladding wettability and reduce porosity defects; and Mn elements ensure uniform microstructure composition, giving the cladding layer both high strength and fatigue resistance, thus addressing the long-term cavitation and wear failure problems of turbine components at the material level.

[0018] Simultaneously, this invention incorporates an online rapid maintenance process adapted to handheld laser equipment. The pretreatment stage thoroughly removes failed coatings, smoothly repairs boundaries, cleans and removes impurities, and precisely preheats, effectively avoiding defects such as porosity, cracks, and inclusions during laser welding cladding. Then, using matched laser power, scanning speed, wire feed speed, and overlap ratio parameters, along with specialized cavitation-resistant wire, it achieves low heat input, minimal deformation, and dense metallurgical bonding through layered cladding repair. Layer-by-layer inspection ensures reliable cladding quality for each layer. After repair, portable insulation cotton is used for slow cooling to eliminate residual welding stress. Finally, surface shaping and polishing restore the original dimensions and service morphology of the component.

[0019] This invention relies on miniaturized handheld laser equipment and special cavitation-resistant wire to overcome the limitations of traditional powder laser welding and cladding equipment, which is bulky and cannot be used on-site. While ensuring that the repair coating is wear-resistant, cavitation-resistant, and has high bonding strength, it enables rapid online maintenance of cavitation-damaged components of water turbines, significantly improving on-site maintenance efficiency and reducing unit downtime and operation and maintenance costs. Attached Figure Description

[0020] 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.

[0021] Figure 1 This is a schematic diagram of a handheld laser welding machine for rapid welding and repair according to an embodiment of the present invention.

[0022] In the picture: 1. Bucket wheel turbine; 2. Laser welding cladding gun head; 3. Optical fiber and pipeline; 4. Handheld laser welding machine; 5. Wire feeder; 6. Wire feed tube; 7. Thermal insulation material. Detailed Implementation

[0023] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0024] This invention provides a corrosion-resistant wire for online rapid maintenance of the surface coating of a water turbine. The wire is a flux-cored welding wire structure, made of nickel-chromium alloy strip covered with internal flux powder. The chemical composition of the wire, by element mass percentage, includes W: 40~44%, Cr: 11~13%, Si: 1.8~2.2%, B: 0.8~1.2%, Mn: 1.6~2.2%, Nb: 1.0~1.6%, with the balance being Ni.

[0025] The thickness of the nickel-chromium alloy strip is 0.3~0.6mm.

[0026] The outer diameter of the wire is Ø1.2mm, Ø1.6mm or Ø2.0mm.

[0027] A method for online rapid maintenance based on cavitation-resistant wire material for surface coating of water turbines includes a surface pretreatment process, a laser welding cladding process, and a post-treatment process performed sequentially.

[0028] Surface pretreatment processes include: A1. Remove the failed coating from the area to be repaired by mechanical or manual grinding, and make a smooth transition between the area to be repaired and the intact area of ​​the component.

[0029] A2. Clean the area to be repaired and the surrounding area using a volatile cleaning agent. The volatile cleaning agent is anhydrous ethanol or acetone, used to remove oil, dust, and oxidized impurities from the surface of the area to be repaired.

[0030] A3. Use a portable heating device to preheat the repair area. The portable heating device is a portable electric heating belt. The preheating temperature is controlled at 150~250℃.

[0031] Laser welding cladding process includes: B1. A portable handheld laser welding machine, along with cavitation-resistant wire, is used to perform cladding repair on the area to be repaired. The laser welding cladding process parameters are: laser power 1350~1800W, welding speed 12~20mm / s, wire feed speed 2.0~4.0m / min, cladding overlap 50~70%, and single-layer cladding thickness 0.8~1.0mm.

[0032] During the cladding process, the surface condition is checked after each layer of cladding is completed. Only after there are no cracks or pore defects can the next layer of laser welding cladding be carried out.

[0033] Post-processing steps include: C1. After the cladding repair is completed, the cladding area is kept warm and cooled to room temperature.

[0034] C2. The surface of the cladding layer after the heat preservation and slow cooling treatment is repaired by manual or mechanical grinding so that the surface size and morphology of the component meet the requirements for service use.

[0035] The heat preservation and slow cooling method uses portable on-site insulation cotton to wrap the cladding area, achieving slow cooling and eliminating residual stress from the cladding process.

[0036] Example The main parameters for this example are as follows: 1. Composition of cavitation resistant wire: W: 42%, Cr: 12%, Si: 2.0%, B: 1.0%, Mn: 1.8%, Nb: 1.2%, Ni balance.

[0037] 2. Wire diameter: Ø1.2mm.

[0038] 3. Implementation method: such as Figure 1 As shown, during online maintenance, necessary covering and protection are first applied to the parts of the bucket wheel turbine 1 that do not require maintenance to avoid damage during the maintenance process. Equipment is deployed according to the site environment, and appropriate laser welding cladding gun heads 2, optical fibers, and pipelines 3 are selected. The original failed layer and boundary treatment are removed by manual grinding. After surface flaw detection confirms no errors, the surface to be laser welded is cleaned with alcohol. Then, a portable electric heating belt is used to preheat the surface to be repaired and the surrounding area, and insulation material 7 is used for heat preservation. After the preheating temperature reaches 200℃, a handheld laser welding machine 4 is used with cavitation-resistant wire for laser welding cladding. The cavitation-resistant wire is fed to the area to be repaired by the wire feeder 5 through the wire feed tube 6. Preheating and heat preservation are continuously performed during the process to ensure the laser welding cladding temperature is above 200℃. Laser welding cladding is performed continuously until the thickness of the laser welding cladding layer meets the requirements.

[0039] Laser welding cladding parameters: power 1500W, speed 15~18mm / s, wire feed speed 3.0m / min, overlap 60%, single layer thickness 0.8~1.0mm.

[0040] After the laser welding cladding is completed, the laser welding cladding area is covered with insulation material to keep it warm and slowly cool it to room temperature. After the laser welding cladding layer is inspected and no defects exceed the standard, the laser welding cladding layer is polished by hand until the shape and surface roughness meet the usage requirements.

[0041] This embodiment demonstrates the successful online partial laser welding cladding repair of the bucket wheel of a bucket turbine. The repaired laser welding cladding layer exhibits excellent resistance to cavitation erosion.

[0042] This invention utilizes a flux-cored cavitation-resistant filament, allowing for rapid adjustment of the composition to meet diverse needs and achieve efficient matching with on-site requirements. It also fully leverages the compact size, weight, and mobility of handheld laser welding equipment, making it well-suited for complex on-site environments and enabling rapid online repair of turbine components. This overcomes the limitations of existing powder laser welding cladding, which cannot meet the requirements for rapid online repair of cavitation-resistant cladding layers in turbines. Furthermore, the method of this invention can be widely applied to the on-site repair of various parts, providing rapid response to on-site needs, and allowing for multiple laser welding cladding processes to repair localized failures.

[0043] According to the present invention, online rapid maintenance of a 390m head, 15MW bucket wheel turbine has been completed. The performance indicators of the bucket wheel, clad using laser welding, all meet the requirements for on-site use. Combining the rapid development and application of miniaturized portable handheld laser welding machine technology, laser welding cladding wire with cavitation resistance has been specifically developed. Using a handheld laser welding machine, rapid online localized laser welding cladding repair can be achieved, possessing the same metallurgical bonding, dense structure, and low heat-affected zone as traditional laser welding cladding. Furthermore, the use of flux-cored welding wire allows for compatibility with various powder materials used in laser welding cladding, enabling rapid repair of localized cavitation-resistant coatings on turbine components.

[0044] 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 cavitation-resistant wire material for online rapid maintenance of the surface coating of a water turbine, characterized in that, The wire is a flux-cored welding wire structure, made of nickel-chromium alloy strip covered with internal flux powder. The chemical composition of the wire, by element mass percentage, includes W: 40~44%, Cr: 11~13%, Si: 1.8~2.2%, B: 0.8~1.2%, Mn: 1.6~2.2%, Nb: 1.0~1.6%, with the balance being Ni.

2. The cavitation-resistant wire material for online rapid maintenance of the surface coating of a water turbine as described in claim 1, characterized in that, The thickness of the nickel-chromium alloy strip is 0.3~0.6mm.

3. The cavitation-resistant wire material for online rapid maintenance of the surface coating of a water turbine as described in claim 1, characterized in that, The outer diameter of the wire is Ø1.2mm, Ø1.6mm or Ø2.0mm.

4. A method for online rapid maintenance based on the cavitation-resistant wire material used for online rapid maintenance of the turbine surface coating as described in any one of claims 1-3, characterized in that, It includes a surface pretreatment process, a laser welding cladding process, and a post-treatment process performed sequentially. The surface pretreatment process includes: A1. Remove the failed coating from the area to be repaired by mechanical or manual grinding, and make a smooth transition at the boundary between the area to be repaired and the intact area of ​​the component; A2. Clean the area to be repaired and the surrounding area using a volatile cleaning agent; A3. Use portable heating equipment to preheat the maintenance area; The laser welding cladding process includes: B1. Use a portable handheld laser welding machine in conjunction with cavitation-resistant wire to perform cladding repair on the area to be repaired; The post-processing steps include: C1. After the cladding repair is completed, the cladding area is subjected to heat preservation and slow cooling treatment until it reaches room temperature; C2. The surface of the cladding layer after the heat preservation and slow cooling treatment is repaired by manual or mechanical grinding so that the surface size and morphology of the component meet the requirements for service use.

5. The method for online rapid maintenance of the surface coating of a water turbine according to claim 4, characterized in that, In step A3, the preheating temperature is controlled at 150~250℃.

6. The method for online rapid maintenance of the surface coating of a water turbine according to claim 4, characterized in that, In step B1, the laser welding cladding process parameters are: laser power 1350~1800W, welding speed 12~20mm / s, wire feed speed 2.0~4.0m / min, cladding overlap 50~70%, and single-layer cladding thickness 0.8~1.0mm.

7. The method for online rapid maintenance of the surface coating of a water turbine according to claim 4, characterized in that, In step A2, the volatile cleaning agent is anhydrous ethanol or acetone, used to remove oil, dust and oxidized impurities from the surface of the area to be repaired.

8. The method for online rapid maintenance of the surface coating of a water turbine according to claim 4, characterized in that, The portable heating device is a portable electric heating belt.

9. A method for online rapid maintenance of the surface coating of a water turbine according to claim 4, characterized in that, In step B1, during the cladding process, the surface condition is checked after each layer of cladding is completed. If there are no cracks or pore defects, the next layer of laser welding cladding is carried out.

10. A method for rapid online maintenance of a turbine surface coating according to claim 4, characterized in that, The heat preservation and slow cooling process involves wrapping the cladding area with portable on-site heat preservation cotton to achieve slow cooling and eliminate residual stress from the cladding process.

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