Preparation method of abrasion-resistant coating of flow passage component of water turbine

Abstract

The invention discloses a preparation method of an abrasion-resistant coating of a flow passage component of a water turbine. The method comprises the following steps that the surface of the flow passage component of the water turbine is pretreated and preheated; coating a bottom layer; coating a middle layer; coating a surface layer; and maintaining the coating. Electromagnetic induction heating is carried out on the flow passage component of the water turbine, heat is conducted outwards from the surface of the flow passage component of the water turbine, and after the coating is coated, the temperature gradient from the surface of the flow passage component of the water turbine to the surface of the coating from high to low is formed. Under the action of temperature gradient, the internal coating close to the surface of the component is cured before the external coating, and the diluent in the coating is gradually migrated and volatilized from inside to outside. The problems that the surface temperature of the coating is higher than the surface of the component due to heating modes such as a traditional drying oven and a drying room, the surface of the coating is cured firstly, a diluent in the coating cannot be effectively discharged, cavitation bubbles are formed between the coating and the surface of the component, the binding force of the coating and the component is affected, and tiny bubbles are formed in the coating, and the abrasion resistance of the coating is affected are avoided.

Description

Technical Field

[0001] The present invention relates to the field of preparation of anti-abrasion coatings, and particularly to a method for preparing an anti-abrasion coating for flow components of a water turbine. Background Art

[0002] A water turbine is a device that converts water energy into mechanical energy. The flow components in a water turbine often fail due to surface wear during service. China is rich in hydropower resources, and hydropower generation is supported by the national energy strategy. However, its development depends on special conditions such as large river drops and high sediment content. Traditional water turbine blades are made of materials such as alloy steel, but they are still affected by wear caused by high-speed water flow impact. When generating electricity, the high-speed flowing sediment-laden water flows on the surface of the water turbine blade, which will cause wear on the surface of the water turbine blade and cause serious harm to the equipment. When the water turbine blade is severely worn, defects such as wear pits will appear on the blade surface, which will affect the stability, operation efficiency and service life of the water turbine unit. At present, more than 30% of hydropower stations in the country are affected by sediment wear, involving tens of thousands of machines. The most economical and effective way to solve the above problems is to prepare a highly wear-resistant and corrosion-resistant coating on the material surface; moreover, whenever the potential of the coating material is further explored and the coating performance is improved, it will have an important impact on extending the service life of the flow components and improving the economic benefits of the power station.

[0003] According to relevant experimental and construction data, to ensure that the coating can fully play its anti-abrasion and corrosion resistance on the surface of the flow components of a hydrogenerator, the primary condition is that the coating material has a high bonding strength (≥30 MPa) to the metal substrate. In addition, the destructive force under muddy water conditions is extremely large, which is caused by the dual action of sediment wear and cavitation wear under the action of sediment-laden water flow; at this time, the proportion of sediment wear is relatively high, and the increase in wear depth will further deteriorate the cavitation conditions, forming a vicious cycle. Therefore, in production, it is urgent to solve the protection problem of the most severely abraded parts (such as the head of the movable guide vane and the head of the blade), and the most crucial one is to improve its anti-cavitation performance. Usually, the main component of river sediment is quartz, and its surface hardness is Mohs hardness 6-7 HM. According to the wear theory, a substance with a lower hardness cannot wear a substance with a higher hardness. Therefore, in order to improve the wear resistance of the bonding coating, wear-resistant components need to be added to the coating.

[0004] In order to improve the curing effect of the epoxy mortar coating and the bonding strength with the flow-through components, since the coating is relatively thick, heating and curing are required after the coating is applied. Due to the relatively thick coating, the influence of curing on the coating performance is particularly important. The traditional heating method is to put the flow-through components with the coated coating into an oven or a drying room and heat them at 30°C to 60°C for about 2 hours. However, it is found in production that this heating method transfers heat from the outside of the coating to the surface of the flow-through components, and the temperature of the outer coating is higher than that of the inner coating, resulting in the outer coating curing first, which affects the migration of the diluent in the inner coating, causing the diluent to form bubbles in the coating and reducing the strength of the coating; some diluents will also gather on the surface of the flow-through components to form pores, thus affecting the bonding strength between the coating and the flow-through components. Summary of the Invention

[0005] The present invention aims at a preparation method for an anti-abrasion coating of a water turbine flow-through component to solve the problems that the existing anti-abrasion coating of a water turbine flow-through component is seriously affected by wear caused by the impact of high-speed water flow, the bonding strength between the coating and the flow-through component is not strong, and there are defects such as wear pits on the blade surface when it is serious.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions: A preparation method for an anti-abrasion coating of a water turbine flow-through component, comprising the following steps:

[0007] S1, surface pretreatment of the water turbine flow-through component: Knock off the bulges and severely worn old coatings on the surface of the flow-through component, remove impurities such as sediment and rust on the surface, and expose the metal body of the component surface by sandblasting or sandpaper grinding, etc.;

[0008] S2, preheating of the water turbine flow-through component: Electromagnetically inductively heat the water turbine flow-through component that has undergone surface pretreatment, with a temperature of 30°C to 60°C and a time of 10 min to 60 min;

[0009] S3, coating of the bottom layer: Brush or spray the bottom layer coating on the surface of the flow-through component, requiring the coating to be uniform, without missing coating or sagging. The thickness of the bottom layer coating is 0.2 mm to 1 mm. After coating, electromagnetically inductively energize and heat, with a temperature of 30°C to 60°C and a time of 10 min to 30 min;

[0010] S4, coating of the intermediate layer: Spray, brush or scrape to evenly coat the intermediate layer coating on the bottom layer coating, without missing coating or sagging. The thickness of the intermediate layer coating is 2 mm to 3 mm. After coating, electromagnetically inductively energize and heat, with a temperature of 30°C to 60°C and a time of 10 min to 30 min;

[0011] S5, Coating of the surface layer: By spraying or brushing, evenly apply the surface layer coating on the intermediate layer coating without missed coating or sagging. The thickness of the surface layer coating is 0.2 mm to 1 mm. After coating, heat it by electromagnetic induction, with the temperature being 30°C to 60°C and the time being 60 min to 120 min;

[0012] S6, Curing: Heat the flow-through components of the water turbine by electromagnetic induction, cure them at a temperature of 30°C to 70°C for 1.5 h to 3.0 h, and then let them cool naturally and stand for 24 h.

[0013] Furthermore, the bottom layer coating is an epoxy resin coating, which is obtained by mixing component A and component B in a mass ratio of 100:2 to 80 before coating. Component A is obtained by dissolving liquid epoxy resin in a diluent, and component B is a curing agent.

[0014] Furthermore, component A of the bottom layer coating includes, by mass parts: 60 - 95 parts of liquid epoxy resin and 5 - 40 parts of diluent; component B of the bottom layer coating includes, by mass parts: 100 parts of curing agent.

[0015] Furthermore, the intermediate layer coating is obtained by mixing component C and component D in a mass ratio of 100:2 to 80 before coating. Component C includes, by mass parts: 65 - 90 parts of liquid epoxy resin, 5 - 35 parts of diluent, and 5 - 20 parts of rigid filler; component D includes, by mass parts: 80 - 99 parts of curing agent and 1 - 20 parts of inorganic filler.

[0016] Furthermore, the rigid filler of the intermediate layer coating is emery or corundum with a particle size of 600 - 2000 mesh; the inorganic filler of the intermediate layer coating is fumed silica or organic bentonite with a particle size of 600 - 2000 mesh.

[0017] Furthermore, the surface layer coating is obtained by mixing component E and component F in a mass ratio of 100:2 to 80 before coating. Component E includes, by mass parts: 60 - 90 parts of liquid epoxy resin, 5 - 35 parts of diluent, and 5 - 10 parts of rigid filler; component F includes, by mass parts: 90 - 99 parts of curing agent and 1 - 10 parts of inorganic filler.

[0018] Furthermore, the rigid filler of the surface layer coating is emery or corundum with a particle size less than 100 nm, and the inorganic filler of the surface layer coating is fumed silica or organic bentonite with a particle size less than 100 nm.

[0019] Further, the liquid epoxy resin includes one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, linear phenolic epoxy resin, and polyfunctional epoxy resin. The diluent includes one or more of glycidyl ether, butanediol diglycidyl ether, polyethylene glycol diglycidyl ether, acetone, cyclohexanone, and xylene. The curing agent includes one or more of ethylenediamine, diethylenetriamine, m-xylylenediamine, and isophorone diamine. The diluent is used to reduce the viscosity of the coating and improve the film-forming effect, and the curing agent is used to cooperate with electromagnetic induction heating to cure the epoxy coating uniformly and rapidly.

[0020] The technical principle of the present invention is: a preparation method of an anti-abrasion and anti-corrosion coating for the flow-through components of a water turbine. Using the principle of electromagnetic induction heating, the flow-through components of the water turbine are preheated before applying the anti-abrasion and anti-corrosion coating and heated after applying the coating to form a temperature gradient curing coating from the inside out. By electromagnetic induction heating the flow-through components of the water turbine, the heat is conducted from the surface of the flow-through components of the water turbine to the outside. After applying the coating, a temperature gradient from high to low is formed from the surface of the flow-through components of the water turbine to the surface of the coating. Under the action of the temperature gradient, the internal coating close to the surface of the component will cure prior to the external coating, and the diluent in the coating will also gradually migrate and volatilize from the inside out. This avoids the situation in traditional heating methods such as ovens and drying rooms where the surface temperature of the coating is higher than the surface of the component, resulting in the surface of the coating curing first, the diluent inside the coating not being able to be effectively discharged, forming voids between the coating and the surface of the component, affecting the bonding force between the coating and the component, and forming micro-bubbles in the coating, affecting the anti-abrasion and anti-corrosion performance of the coating.

[0021] Compared with the existing oven or drying room heating technology, the present invention uses electromagnetic induction heating to heat the alloy flow-through components of the water turbine. The heat is conducted from the surface of the flow-through components of the water turbine to the outside, forming a temperature gradient from high to low from the surface of the flow-through components of the water turbine to the surface of the coating. Under the action of the temperature gradient, the internal coating close to the surface of the component will cure prior to the external coating, and the diluent in the coating will also gradually migrate and volatilize from the inside out, thereby obtaining a coating with better bonding force and higher strength with the flow-through components. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic cross-section of the coating of the present invention: 1 is the surface of the flow-through components of the water turbine, 2 is the bottom layer of the coating, 3 is the intermediate layer of the coating, 4 is the top layer of the coating, and 5 is the direction of heat transfer during the induction heating process.

[0023] Figure 2 SEM image of the coating surface with defects using traditional oven heating.

[0024] Figure 3 SEM image of the coating surface without defects using electromagnetic induction heating of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] Surface pretreatment of the flow components of the water turbine: For the disassembled water turbine blade (40 cm wide, 60 cm long, 8 mm thick at the edge and 60 mm thick in the middle), after scraping off the damaged and bulging coatings with a scraper, blow sand to remove rust and expose the alloy matrix of the blade.

[0026] Preheating of the flow components of the water turbine: Then, use an electromagnetic induction coil to wrap the blade as a whole, adjust the distance between the coil and the blade surface to be between 50 mm and 80 mm, turn on the control cabinet, energize for heating, control the heating rate at 5 °C / min, heat up to 50 °C, keep warm for 20 min, and then stop heating.

[0027] Coating of the bottom layer, middle layer, and top layer: Then, remove the induction coil, spray the bottom coating, and then put the induction coil around the blade and heat it by electromagnetic induction. After that, remove the induction coil, brush the middle layer, and after coating, put on the induction coil and heat it by electromagnetic induction. Then, remove the induction coil and brush the top layer. After coating, put on the induction coil and heat it by electromagnetic induction. For the schematic cross-section of the coating of the present invention, see Figure 1 。

[0028] Curing: Heat the flow components of the water turbine by electromagnetic induction, cure at a temperature of 30 °C to 70 °C for 1.5 h to 3.0 h, and then cool naturally and stand still for 24 h.

[0029] Example 1

[0030] The A component of the bottom coating is obtained by mixing 70 parts by mass of bisphenol A epoxy resin, 25 parts of glycidyl ether, and 5 parts of xylene. The B component is 50 parts by mass of diethylenetriamine and 50 parts of m-xylylenediamine. The thickness of the bottom layer is controlled to be 0.4 - 0.5 mm. After coating, an induction coil is put on and heated by electromagnetic induction. It is heated at 50 °C for 10 min. The C component of the intermediate layer coating is obtained by mixing 60 parts by mass of bisphenol A epoxy resin, 15 parts of glycidyl ether, 10 parts of xylene, and 15 parts of 1000-mesh carborundum. The D component is obtained by mixing 40 parts by mass of diethylenetriamine, 45 parts of m-xylylenediamine, and 15 parts of 1000-mesh fumed silica. The thickness of the intermediate layer is controlled to be 2.4 - 2.6 mm. After coating, an induction coil is put on and heated by electromagnetic induction. It is heated at 50 °C for 20 min. The E component of the surface layer coating is obtained by mixing 60 parts by mass of bisphenol A epoxy resin, 20 parts of glycidyl ether, 10 parts of xylene, and 10 parts of carborundum with a particle size of 60 nm - 100 nm. The F component is obtained by mixing 47 parts by mass of diethylenetriamine, 45 parts of m-xylylenediamine, and 8 parts of fumed silica with a particle size of 60 nm - 100 nm. The thickness of the surface layer is controlled to be 0.5 - 1.0 mm. After coating, an induction coil is put on and heated by electromagnetic induction. It is heated at 50 °C for 80 min. The flow-through components of the water turbine are heated by electromagnetic induction. It is cured at 50 °C for 2.0 h, and then naturally cooled and left standing for 24 h. The bonding strength between the obtained coating and the blade surface reaches 55.0 MPa. The SEM image of the coating surface is shown in Figure 3 , and there are no bubbles on the surface of the flow-through components.

[0031] Example 2

[0032] The base coat A component is obtained by mixing 70 parts by mass of bisphenol A epoxy resin and 30 parts by mass of glycidyl ether. The B component is 50 parts by mass of diethylenetriamine and 50 parts by mass of m-xylylenediamine. The base coat thickness is controlled to be 0.4 - 0.5 mm. After coating, an induction coil is put on and heated by electromagnetic induction power-on. It is heated at 50 °C for 10 min. The intermediate coat C component is obtained by mixing 60 parts by mass of bisphenol F epoxy resin, 15 parts by mass of glycidyl ether, 10 parts by mass of xylene, and 15 parts by mass of 1000-mesh carborundum. The D component is obtained by mixing 40 parts by mass of diethylenetriamine, 45 parts by mass of m-xylylenediamine, and 15 parts by mass of 1000-mesh fumed silica. The intermediate coat thickness is controlled to be 2.4 - 2.6 mm. After coating, an induction coil is put on and heated by electromagnetic induction power-on. It is heated at 50 °C for 20 min. The top coat E component is obtained by mixing 60 parts by mass of bisphenol A epoxy resin, 20 parts by mass of glycidyl ether, 10 parts by mass of xylene, and 10 parts by mass of carborundum with a particle size of 60 nm - 100 nm. The F component is obtained by mixing 47 parts by mass of diethylenetriamine, 45 parts by mass of m-xylylenediamine, and 8 parts by mass of fumed silica with a particle size of 60 nm - 100 nm. The top coat thickness is controlled to be 0.5 - 1.0 mm. After coating, an induction coil is put on and heated by electromagnetic induction power-on. It is heated at 50 °C for 80 min. The flow-through components of the water turbine are heated by electromagnetic induction power-on, cured at 50 °C for 2.0 h, then naturally cooled and left standing for 24 h. The bonding strength between the obtained coating and the blade surface reaches 54.7 MPa. There are no bubbles on the surface of the flow-through components.

[0033] Example 3

[0034] The base coat A component is obtained by mixing 70 parts by mass of bisphenol A type epoxy resin and 30 parts by mass of glycidyl ether. The B component is 50 parts by mass of diethylenetriamine and 50 parts by mass of m-xylylenediamine. The base coat thickness is controlled to be 0.4 - 0.5 mm. After coating, an induction coil is put on and heated by electromagnetic induction power-on. It is heated at 50 °C for 10 min. The intermediate coat C component is obtained by mixing 60 parts by mass of bisphenol F type epoxy resin, 15 parts by mass of glycidyl ether, 10 parts by mass of xylene, and 15 parts by mass of 1000-mesh carborundum. The D component is obtained by mixing 40 parts by mass of diethylenetriamine, 45 parts by mass of m-xylylenediamine, and 15 parts by mass of 1000-mesh fumed silica. The intermediate coat thickness is controlled to be 2.4 - 2.6 mm. After coating, an induction coil is put on and heated by electromagnetic induction power-on. It is heated at 50 °C for 20 min. The top coat E component is obtained by mixing 60 parts by mass of bisphenol F type epoxy resin, 20 parts by mass of glycidyl ether, 10 parts by mass of xylene, and 10 parts by mass of carborundum with a particle size of 60 nm - 100 nm. The F component is obtained by mixing 47 parts by mass of diethylenetriamine, 45 parts by mass of m-xylylenediamine, and 8 parts by mass of fumed silica with a particle size of 60 nm - 100 nm. The top coat thickness is controlled to be 0.5 - 1.0 mm. After coating, an induction coil is put on and heated by electromagnetic induction power-on. It is heated at 50 °C for 80 min. The flow-through components of the water turbine are heated by electromagnetic induction power-on, cured at 50 °C for 2.0 h, then cooled naturally and left standing for 24 h. The bonding strength between the obtained coating and the blade surface reaches 54.2 MPa. There are no bubbles on the surface of the flow-through components.

[0035] Comparative example

[0036] Take the preheated flow components of the water turbine, and apply the bottom coat. The component A of the bottom coat is obtained by mixing 70 parts by mass of bisphenol A epoxy resin, 25 parts of glycidyl ether, and 5 parts of xylene. The component B of the bottom coat is 50 parts by mass of diethylenetriamine and 50 parts by mass of m-xylylenediamine. Control the thickness of the bottom coat to be 0.4 - 0.5 mm. After coating, heat it in an oven at 50 °C for 10 min; The component C of the intermediate coat is obtained by mixing 60 parts by mass of bisphenol A epoxy resin, 15 parts of glycidyl ether, 10 parts of xylene, and 15 parts of 1000-mesh carborundum. The component D of the intermediate coat is obtained by mixing 40 parts by mass of diethylenetriamine, 45 parts by mass of m-xylylenediamine, and 15 parts of 1000-mesh fumed silica. Control the thickness of the intermediate coat to be 3.0 - 3.5 mm. After coating, heat it in an oven at 50 °C for 20 min; The component E of the top coat is obtained by mixing 60 parts by mass of bisphenol A epoxy resin, 20 parts of glycidyl ether, 10 parts of xylene, and 10 parts of carborundum with a particle size of 60 nm - 100 nm. The component F of the top coat is obtained by mixing 47 parts by mass of diethylenetriamine, 45 parts by mass of m-xylylenediamine, and 8 parts of fumed silica with a particle size of 60 nm - 100 nm. Control the thickness of the top coat to be 0.5 - 1.0 mm. After coating, heat it in an oven at 50 °C for 80 min. Cure the flow components of the water turbine in an oven at a heating temperature of 50 °C for 2.0 h, then let it cool naturally and stand for 24 h. The bonding strength between the obtained coating and the blade surface reaches 50.2 MPa. There are defects on the surface of the flow components. The SEM image of the defective coating surface is shown in Figure 2 , and the defective part is within the red dotted circle.

[0037] As mentioned above, it is only the preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

Claims

1. A preparation method of an anti-abrasion and anti-corrosion coating for a flow-through component of a water turbine, characterized in that, It includes the following steps: S1. Surface pretreatment of the flow components of the water turbine: Knock out the bulges and severely worn old coatings on the surface of the flow components, remove impurities such as sediment and rust on the surface, and expose the metal body of the components by sandblasting or sandpapering; S2. Preheating of the flow components of the water turbine: Electromagnetically inductively heat the flow components of the water turbine that have undergone surface pretreatment, with a temperature of 30°C to 60°C and a time of 10 min to 60 min; S3. Coating of the bottom layer: Apply the bottom layer coating to the surface of the flow components by brushing or spraying, requiring the coating to be uniform, without missed coating or sagging. The thickness of the bottom layer coating is 0.2 mm to 1 mm. After coating, electromagnetically inductively energize and heat, with a temperature of 30°C to 60°C and a time of 10 min to 30 min; S4. Coating of the intermediate layer: Apply the intermediate layer coating evenly on the bottom layer coating by spraying, brushing or scraping, without missed coating or sagging. The thickness of the intermediate layer coating is 2 mm to 3 mm. After coating, electromagnetically inductively energize and heat, with a temperature of 30°C to 60°C and a time of 10 min to 30 min; S5. Coating of the top layer: Apply the top layer coating evenly on the intermediate layer coating by spraying or brushing, without missed coating or sagging. The thickness of the top layer coating is 0.2 mm to 1 mm. After coating, electromagnetically inductively energize and heat, with a temperature of 30°C to 60°C and a time of 60 min to 120 min; S6. Curing: Electromagnetically inductively energize and heat the flow components of the water turbine, cure at a temperature of 30°C to 70°C for 1.5 h to 3.0 h, and then naturally cool down and stand still for 24 h.

2. The method according to claim 1, characterized in that, The bottom layer coating is an epoxy resin coating, which is obtained by mixing component A and component B in a mass ratio of 100:2 to 80 before coating. Component A is obtained by dissolving liquid epoxy resin in a diluent, and component B is a curing agent.

3. The method according to claim 2, characterized in that Component A of the bottom layer coating includes, by mass: 60 - 95 parts of liquid epoxy resin, 5 - 40 parts of diluent; Component B includes, by mass: 100 parts of curing agent.

4. The method according to claim 1, characterized in that, The intermediate layer coating is obtained by mixing component C and component D in a mass ratio of 100:2 to 80 before coating. Component C includes, by mass: 65 - 90 parts of liquid epoxy resin, 5 - 35 parts of diluent, 5 - 20 parts of rigid filler; Component D includes, by mass: 80 - 99 parts of curing agent, 1 - 20 parts of inorganic filler.

5. The method according to claim 4, wherein The rigid filler is corundum or emery with a mesh size of 600 - 2000; The inorganic filler is fumed silica or organic bentonite with a mesh size of 600 - 2000.

6. The method according to claim 1, characterized in that The top layer coating is obtained by mixing component E and component F in a mass ratio of 100:2 to 80 before coating. Component E includes, by mass: 60 - 90 parts of liquid epoxy resin, 5 - 35 parts of diluent, 5 - 10 parts of rigid filler; Component F includes, by mass: 90 - 99 parts of curing agent, 1 - 10 parts of inorganic filler.

7. The method according to claim 6, wherein The rigid filler of the top layer coating is corundum or emery with a particle size less than 100 nm, and the inorganic filler is fumed silica or organic bentonite with a particle size less than 100 nm.

8. The method according to claim 2 or 4 or 6, characterized in that, The liquid epoxy resin includes one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, linear phenolic epoxy resin and polyfunctional epoxy resin. The diluent includes one or more of glycidyl ether, butanediol diglycidyl ether, polyethylene glycol diglycidyl ether, acetone, cyclohexanone and xylene. The curing agent includes one or more of ethylenediamine, diethylenetriamine, m-xylylenediamine and isophorone diamine.

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