A wind turbine main shaft with a surface coating and a long-life corrosion-resistant treatment method and use thereof

Abstract

The present invention belongs to the field of wind turbine main shafts and surface treatment, and specifically relates to a wind turbine main shaft with a surface coating and a long-life corrosion-resistant treatment method and use. The wind turbine main shaft is treated with a surface coating so that the outer layer forms a Cu crystallized transition layer and an amorphous structure layer from the inside to the outside. The Cu crystallized transition layer grows preferentially along the (111) crystal plane, and the amorphous structure layer contains Co, Ni, Cr, Mo, N, and Si in a specific ratio. The two layers are sprayed using a thermal spraying process and are subjected to specific heat treatment respectively after spraying. The surface treatment technology of the wind turbine main shaft of the present invention can significantly extend the life, wear resistance and corrosion resistance of the wind turbine main shaft, and improve its applicability to corrosive and wear-prone environments.

Description

Technical Field

[0001] The present invention belongs to the field of wind turbine main shafts and surface treatment, and in particular relates to a wind turbine main shaft with a surface coating and a long-life corrosion-resistant treatment method and application. Background Art

[0002] As a core component of wind turbines, the wind turbine main shaft plays a crucial role in converting wind energy into mechanical energy and driving the generator to generate electricity. With the rapid development of the wind power industry, the performance requirements for main shaft products are constantly increasing, driving their development towards lightweight, high strength, and high corrosion resistance.

[0003] Wind turbine main shafts face demanding operating conditions. Offshore wind turbines, in particular, are often exposed to corrosive environments with high humidity and salinity, and are subjected to long-term alternating loads. These alternating loads can easily lead to the initiation and propagation of fatigue cracks. Once cracks form, the main shaft's service life is severely impacted. Furthermore, due to thermal expansion coefficient mismatch and residual tensile stresses, stress concentrations can easily occur between the coating and the substrate during operation, further accelerating fatigue crack propagation and leading to premature shaft failure. Furthermore, the main shaft material's insufficient toughness makes it susceptible to fracture under impact loads, making it unable to meet the requirements of long-term stable operation. During high-speed rotation and long-term operation, the main shaft's surface is subject to contact and friction with media such as air, dust, and lubricants, resulting in surface wear. This wear not only reduces surface finish and increases frictional resistance, but also compromises transmission accuracy and efficiency. Furthermore, the resulting debris can further exacerbate main shaft wear, creating a vicious cycle. Under some harsh working conditions, such as dusty environments or heavy-load startup, the main shaft will wear faster. If the main shaft surface hardness is not enough, or the bonding strength of the wear-resistant coating is insufficient, it will also lead to increased wear and affect the service life of the main shaft. For offshore wind turbines, the wind turbine main shaft faces a harsh environment of high salt spray and high humidity, and the corrosion problem is particularly prominent. Corrosion will reduce the strength and toughness of the main shaft, making it more prone to fracture. At the same time, the rust produced by corrosion will increase the surface roughness of the main shaft, further aggravating wear. In some acidic or alkaline environments, the corrosion rate will be even faster. If the corrosion resistance of the main shaft material is insufficient, or the protective performance of the anti-corrosion coating is poor, it will also lead to increased corrosion and affect the service life of the main shaft.

[0004] Although there are many reports on spraying corrosion-resistant coatings on alloy surfaces, including high-entropy alloy coatings and amorphous alloy coatings, they still cannot meet the requirements of special-purpose alloys for wind turbine main shafts, which have extremely high mechanical strength requirements and harsh working conditions. For example, the stainless steel surface coating technology disclosed in CN119663279A can improve the strength of stainless steel and stainless steel itself has strong corrosion resistance, but stainless steel is not suitable for making drive shafts. The high-entropy alloy coating technology disclosed in CN117488140A can improve the wear resistance and corrosion resistance of alloy materials, but the required coating thickness is as high as 1mm. The high-temperature corrosion-resistant coating powder disclosed in CN118875289A also has the advantages of improving alloy hardness, wear resistance, and corrosion resistance, but its Vickers hardness is only 850HV at most and its life is short, which makes it difficult to meet the requirements of wind turbine main shafts under harsh working conditions. The amorphous alloy coating technology disclosed in CN104561877A has the advantages of improving alloy wear resistance and corrosion resistance, but its hardness is poor.

[0005] Therefore, technical personnel in this field urgently need to develop a long-life corrosion-resistant surface treatment technology for the surface of the wind turbine main shaft to better solve the problems of corrosion, wear and other problems caused by harsh working conditions during the operation of the above-mentioned wind turbine main shaft, thereby extending the service life of the wind turbine main shaft. Summary of the Invention

[0006] In response to the above problems, the purpose of the present invention is to provide a wind turbine main shaft with a surface coating and a long-life corrosion-resistant treatment method and use. The wind turbine main shaft and the long-life corrosion-resistant treatment method enable the wind turbine main shaft to have the characteristics of long life, wear resistance, corrosion resistance, high hardness, etc., and significantly improve the adaptability of the wind turbine main shaft to harsh working conditions including highly corrosive environments (such as wind power generation in marine environments) and highly abrasive environments (such as wind power generation in dusty environments).

[0007] The technical solutions of the present invention are as follows:

[0008] First, the present invention provides a wind turbine main shaft with a surface coating, wherein the wind turbine main shaft consists of a wind turbine main shaft substrate, a Cu crystallized transition layer covering the wind turbine main shaft substrate, and an amorphous structure layer covering the Cu crystallized transition layer; the X-ray diffraction pattern of the Cu crystallized transition layer presents a Cu (111) peak; the X-ray diffraction pattern of the amorphous structure layer presents a steamed bun peak when 2θ is between 35° and 50°, and the amorphous degree calculated by MDIJade is more than 98%; the amorphous structure layer contains the following elements by mass percentage: Co: 27.5~28.0%; Ni: 27.0~28.0%; Cr: 18.0%~18.5%; Mo: 15.0%~15.5%; Nb: 7.5%~8.0%; Si: 2.9%~3.5%; the thickness of the Cu crystallized transition layer is 200~500μm; the thickness of the amorphous structure layer is 280~450μm.

[0009] Preferably, the amorphous structure layer contains the following elements by mass percentage: Co: 27.9%~28.0%; Ni: 27.5%~28.0%; Cr: 18.2%~18.3%; Mo: 15.3%~15.5%; Nb: 7.7%~8.0%; Si: 3.1%~3.5%.

[0010] Preferably, the wind turbine main shaft substrate is selected from one of 34CrNiMo6 alloy steel, GCr15 alloy steel, 40Cr alloy steel, and 42CrMo4 alloy steel.

[0011] Another aspect of the present invention provides a method for treating a wind turbine main shaft for long life and corrosion resistance, comprising cleaning a surface of a wind turbine main shaft substrate and ultrasonic shot peening of the wind turbine main shaft substrate. The method further comprises the following steps:

[0012] S1 uses supersonic flame spraying equipment to spray Cu coating on the surface of the wind turbine main shaft substrate after ultrasonic shot peening;

[0013] S2 uses a vacuum heat treatment furnace to perform crystallization treatment on the surface of the wind turbine main shaft after the Cu coating is sprayed in step S1 to form a Cu crystallized transition layer;

[0014] S3 uses a supersonic flame spraying device to spray an amorphous alloy coating on the surface of the wind turbine main shaft formed with the Cu crystallized transition layer in step S2, wherein the amorphous alloy coating uses an amorphous alloy powder with a particle size range of 3-12 μm, and the amorphous alloy powder contains the following elements by mass percentage: Co: 27.5-28.0%; Ni: 27.0-28.0%; Cr: 18.0%-18.5%; Mo: 15.0%-15.5%; Nb: 7.5%-8.0%; Si: 2.9%-3.5%;

[0015] S4 uses a vacuum heat treatment furnace to perform performance heat treatment on the surface of the wind turbine main shaft sprayed with amorphous alloy coating to form an amorphous structure layer;

[0016] The thickness of the Cu crystallization transition layer is 200-500 μm; the thickness of the amorphous structure layer is 280-450 μm.

[0017] Preferably, in step S1, the supersonic flame spraying process conditions are: oxygen 255L / min~280L / min, kerosene 58L / min~62L / min, spraying distance 224mm~254mm, powder feeding amount 35g / min~40g / min, auxiliary gas is hydrogen, and the flow rate is 12slpm~28slpm.

[0018] Preferably, in step S2, the crystallization process conditions are: vacuum degree 3.0×10 -4Pa~1.0×10 -4 Pa, temperature 600℃~650℃, holding time 45min~70min.

[0019] Preferably, in step S3, the supersonic flame spraying process conditions are: oxygen 282 L / min~295 L / min, kerosene 63 L / min~65 L / min, spraying distance 212 mm~237 mm, powder feeding amount 35 g / min~40 g / min, auxiliary gas is hydrogen, and the flow rate is 18 slpm~28 slpm.

[0020] Preferably, in step S4, the heat treatment step is to first evacuate to 3.0×10 -4 ~1.0×10 -4 Pa, followed by a four-stage gradient heat treatment; the process of the four-stage gradient heat treatment is as follows:

[0021] The first stage: heating at 6-10℃ / min to 650-680℃ and keeping warm for 1.5-2.5h;

[0022] The second stage: cooling at 5-7°C / min to 485-515°C and then keeping warm for 0.9-1.5h;

[0023] The third stage: cooling at 3-5°C / min to 240-250°C and then keeping warm for 0.8-1.2h;

[0024] The fourth stage: cool to 100-120°C at 7-8°C / min, then take out and place in air to cool to room temperature.

[0025] Preferably, the amorphous alloy powder is prepared by vacuum air atomization, and the vacuum air atomization method comprises the following steps:

[0026] F1 alloy smelting: Weigh the raw material powder according to the proportion and add it into a high-purity crucible. Under the protection of high-purity argon, use a medium-frequency induction melting furnace to melt the alloy into a completely liquid state. The melting temperature is controlled at 1550℃~1620℃ and the melting time is 30 min~45 min.

[0027] F2 atomization powder making: The smelted alloy liquid flows into the insulation tank through the tundish and then into the atomization nozzle through the guide pipe. The annular gap nozzle is used, the nozzle diameter is 1.5mm~2mm, the nozzle outlet pressure is 10Mpa~20Mpa, and the alloy liquid is impacted by high-pressure argon gas at a speed of 1000m / s~1200m / s to atomize and break it into droplets. The atomized droplets are 1×10 -2 Pa~3×10 -2 In Pa environment, 1×10 6 K / s ~3×10 6 K / s cooling rate cooling;

[0028] F3 powder collection: The cooled powder settles at the bottom of the atomization tower, and the amorphous alloy powder with the required particle size range is separated through a vibration screening system. The amorphous alloy powder is then immersed in deionized water for cleaning to remove surface oxides and residual gases. The powder is then centrifugally dried or dried with hot air to remove moisture. The powder is then vacuum dried at 100°C to 150°C for 2h to 4h, and then graded and screened to obtain amorphous alloy powder with uniform particle size.

[0029] The present invention further provides the use of the wind turbine main shaft with the aforementioned surface coating or the wind turbine main shaft obtained by the aforementioned long-life corrosion-resistant treatment method for the wind turbine main shaft as a wind turbine main shaft used in highly corrosive environments (such as wind power generation in marine environments) and / or highly abrasive environments (such as wind power generation in dusty environments).

[0030] The present invention has the following technical effects or advantages:

[0031] (1) The surface treatment technology of the present invention can form a composite structure coating of the amorphous structure layer / Cu crystallized transition layer with alternating soft / hard components on the surface of the wind turbine main shaft substrate, which has the advantages of long life, high wear resistance and strong corrosion resistance.

[0032] (2) The surface treatment technology of the present invention requires a thinner surface coating, which reduces material costs. Moreover, based on the coordinated treatment technology of the Cu crystallization transition layer and the amorphous structure layer, not only does the four-stage gradient performance heat treatment effectively play a role in improving performance, but it also effectively reduces the thickness and cost of the expensive amorphous structure layer.

[0033] (3) The present invention has found through research that the use of an amorphous structure layer or a Cu crystallized transition layer alone, even after heat treatment, cannot significantly improve the lifespan, strength, wear resistance, corrosion resistance and other properties of the wind turbine main shaft. However, a specific layered spraying strategy (first Cu crystallized transition layer and then amorphous structure layer) combined with a specific heat treatment method and a specific thickness design can significantly improve the lifespan, strength, wear resistance, corrosion resistance and other properties of the wind turbine main shaft. Among them, the Cu crystallized transition layer (200~500μm) and the amorphous layer (280~450μm) provide a dense barrier, forming a gradient structure with a total coating thickness of 480~950μm. If a single thick layer is used (e.g., a single layer greater than 500~1000μm), stress cracks will occur. The Cu crystallized transition layer can fill the microscopic defects of the wind turbine main shaft substrate. The specific heat treatment makes the layer grow preferentially along the (111) crystal plane, effectively alleviating the difference in thermal expansion coefficient between the amorphous structure layer and the metal substrate. The ordinary spraying process without the Cu crystallized transition layer is prone to random growth of grains.

[0034] (4) Although the four-stage gradient performance heat treatment failed to change the microstructure and amorphization phenomenon of each coating, it may benefit from the thermal buffering effect of the Cu crystallization transition layer, reducing the thermal shock and other effects on the amorphous structure layer, making the amorphous structure layer conducive to eliminating the source of microcrack initiation during the four-stage gradient performance heat treatment, inhibiting the heterogeneous nucleation of the amorphous structure layer, and unexpectedly improving the life, strength, wear resistance, corrosion resistance and other properties of the wind turbine main shaft. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a microscopic morphology of the composite coating of the product of Experimental Example 1 of the present invention;

[0036] Figure 2 This is the X-ray diffraction detection spectrum of the Cu crystallization transition layer of the product of Experimental Example 1 of the present invention;

[0037] Figure 3 This is the energy spectrum detection spectrum of the amorphous structure layer of the product of Experimental Example 1 of the present invention;

[0038] Figure 4 This is the X-ray diffraction detection spectrum of the amorphous structure layer of the product of Experimental Example 1 of the present invention. DETAILED DESCRIPTION

[0039] The present invention will be further described below with reference to specific embodiments and accompanying drawings. It should be understood that the specific embodiments are only used to explain the present invention and are not used to limit the scope of protection of the present invention.

[0040] It should be noted that:

[0041] First, as an illustrative illustration, the wind turbine main shaft substrates used in the following embodiments are all wind turbine main shafts made of 34CrNiMo6 alloy of the same specification, that is, the wind turbine main shafts have substrates made of 34CrNiMo6 alloy.

[0042] Secondly, in the following embodiments, the treatment process before the wind turbine main shaft substrate coating is processed adopts the following preferred treatment process obtained in the inventor's preliminary experiments:

[0043] C1: The wind turbine main shaft substrate is cleaned by three steps of alkali washing, pickling and water washing. The process conditions of the three steps of alkali washing, pickling and water washing are shown in Table 1:

[0044] Table 1 Three-step surface cleaning process conditions for wind turbine main shaft substrate: alkali washing, pickling, and water washing

[0045]

[0046] In a specific embodiment, as an exemplary treatment, the sodium hydroxide concentration for alkali washing is selected to be 55 g / L, and the treatment is carried out at 85°C for 650 s; the nitric acid concentration for acid washing is selected to be 33%, and the treatment is carried out at 37°C for 1900 s; the sodium carbonate concentration for water washing is selected to be 7 g / L, and the treatment is carried out at 26°C for 400 s.

[0047] C2: The cleaned wind turbine main shaft substrate is subjected to ultrasonic shot peening. During the ultrasonic shot peening process, ultrasonic vibrations are applied with an amplitude of 40-50 μm and a frequency of 35-50 kHz, alternating cosine and sine waves with 6-8 alternating amplitude and frequency. Each ultrasonic shot lasts 30-50 minutes. In a specific embodiment, as an exemplary treatment, during the ultrasonic shot peening process, ultrasonic vibrations are applied with an amplitude of 45 μm and a frequency of 40 kHz, alternating cosine and sine waves with 7 alternating amplitude and frequency. Each ultrasonic shot lasts 40 minutes.

[0048] Finally, in the following embodiments, the specially prepared amorphous alloy powder of the present invention used for the amorphous coating of the wind turbine main shaft is prepared by vacuum air atomization. The amorphous alloy powder contains the following elements by mass percentage: Co: 27.5% to 28.0%; Ni: 27.0% to 28.0%; Cr: 18.0% to 18.5%; Mo: 15.0% to 15.5%; Nb: 7.5% to 8.0%; Si: 2.9% to 3.5%. The vacuum air atomization preparation method includes the following steps:

[0049] F1 alloy smelting: Weigh the raw material powder according to the proportion and add it into a high-purity crucible. Under the protection of high-purity argon, use a medium-frequency induction melting furnace to melt the alloy into a completely liquid state. The melting temperature is controlled at 1550℃~1620℃ and the melting time is 30 min~45 min.

[0050] F2 atomization powder making: The smelted alloy liquid flows into the insulation tank through the tundish and then is introduced into the atomization nozzle through the guide pipe. The annular gap nozzle is used, the nozzle diameter is 1.5mm~2mm, the nozzle outlet pressure is 10Mpa~20Mpa, and the alloy liquid is impacted by high-pressure argon gas at a speed of 1000m / s~1200m / s to atomize and break it into droplets. The atomized droplets are 1×10- 2 Pa~3×10 -2 In Pa environment, 1×10 6 K / s ~3×10 6 K / s cooling rate cooling;

[0051] F3 powder collection: The cooled powder settles at the bottom of the atomization tower, and the amorphous alloy powder with the required particle size range is separated through a vibration screening system. The amorphous alloy powder is then immersed in deionized water for cleaning to remove surface oxides and residual gases. The powder is then centrifugally dried or dried with hot air to remove moisture. The powder is then vacuum dried at 100°C to 150°C for 2h to 4h, and then graded and screened to obtain amorphous alloy powder with uniform particle size.

[0052] In a specific embodiment, as an exemplary preparation, the melting temperature of step F1 is controlled at 1600°C and the melting time is 40 min; the nozzle diameter of step F2 is 1.5 mm, the nozzle outlet pressure is 15 MPa, the high-pressure argon gas velocity is 1100 m / s, and the droplet cooling pressure is 2×10 -2 Pa, cooling rate 2×10 6 K / s; in step F3, the amorphous alloy powder is vacuum dried at 125°C for 3h and then graded and sieved.

[0053] Example 1 A wind turbine main shaft with a surface coating, its preparation method, and structural analysis

[0054] According to the above method, the treatment process before the wind turbine main shaft substrate coating is completed, and then the surface coating treatment of the wind turbine main shaft substrate is carried out. The steps are as follows:

[0055] S1 uses supersonic flame spraying equipment to spray Cu coating on the surface of the wind turbine main shaft substrate after ultrasonic shot peening;

[0056] S2 uses a vacuum heat treatment furnace to perform crystallization treatment on the surface of the wind turbine main shaft after the Cu coating is sprayed in step S1 to form a Cu crystallized transition layer;

[0057] S3 uses a supersonic flame spraying device to spray an amorphous alloy coating on the surface of the wind turbine main shaft where the Cu crystallized transition layer is formed in step S2;

[0058] S4 uses a vacuum heat treatment furnace to perform a performance heat treatment (a four-stage gradient heat treatment process) on the surface of the wind turbine main shaft, which has been sprayed with an amorphous alloy coating, to form an amorphous structure layer. Specific process parameters for the samples in different experimental examples are shown in Table 2.

[0059] Table 2 Surface coating treatment process parameter information of different experimental samples

[0060]

[0061] As a representative product, the microscopic morphology of the composite coating of the sample of Experimental Example 1, the XRD (X-ray diffraction) detection spectrum of the Cu crystallized transition layer, the energy spectrum detection spectrum of the amorphous structure layer, and the XRD detection spectrum of the amorphous structure layer are shown in Figure 1. Figures 1 to 4 .

[0062] Depend on Figure 1 It can be seen that a double-layer composite coating is formed on the surface of the wind turbine main shaft substrate, the outermost layer is an amorphous structure layer, the second layer is a Cu crystallized transition layer, and the innermost layer is the wind turbine main shaft substrate.

[0063] Depend on Figure 2 It can be seen that the Cu crystallization transition layer shows a highly crystallized Cu layer through XRD detection, and presents a relatively obvious Cu (111) peak at 2θ=43.4°, indicating that Cu grows preferentially along the (111) crystal plane.

[0064] Depend on Figure 3 It can be seen that the main components of the amorphous structure layer are Co, Ni, Cr, Mo, Nb, and Si through energy spectrum detection. The element composition (mass percentage) of the amorphous structure layer is Co: 27.95%; Ni: 27.53%; Cr: 18.24%; Mo: 15.35%; Nb: 7.76%; Si: 3.17%. No oxygen element was found in the energy spectrum detection, indicating that there is no oxidation in the amorphous structure layer.

[0065] Depend on Figure 4 The XRD pattern of the amorphous layer exhibits a broad diffuse scattering peak between 35° and 50° (2θ), commonly known as the "steamed bun peak," with no distinct sharp diffraction peaks. The MDIJade calculation indicates a degree of amorphism slightly exceeding 98%. Furthermore, the XRD patterns before and after the four-step gradient heat treatment are similar, indicating that the surface maintains an amorphous structure after the treatment.

[0066] Example 2 Performance test comparison of different wind turbine main shafts

[0067] In order to investigate the performance of wind turbine main shafts obtained by different coating treatment technologies, the following comparative examples were prepared:

[0068] Comparative Example 1: The wind turbine main shaft made of 34CrNiMo6 alloy is not subjected to surface coating treatment.

[0069] Comparative Example 2: The wind turbine main shaft is made of 34CrNiMo6 alloy. Compared with Experimental Example 1, the difference is that the Cu coating is not sprayed and heat treated (that is, steps S1 and S2 are missing), and the thickness of the amorphous structure layer is the sum of the thickness of the Cu crystallization transition layer and the thickness of the amorphous structure layer in Experimental Example 1.

[0070] Comparative Example 3: The wind turbine main shaft is made of 34CrNiMo6 alloy. Compared with Experimental Example 1, the difference is that the spraying and heat treatment of the amorphous alloy coating are not performed (that is, steps S3 and S4 are missing), and the thickness of the Cu crystallized transition layer is the sum of the thickness of the Cu crystallized transition layer in Experimental Example 1 and the thickness of the amorphous structure layer.

[0071] Comparative Example 4: The wind turbine main shaft is made of 34CrNiMo6 alloy. Compared with Experimental Example 1, the difference is that the heat treatment method in step S4 is to vacuum to 5×10 -3 Pa, heated to 850℃ at 12℃ / min and kept warm for 2.5h; then cooled to 600℃ at 10℃ / min; then cooled to 300℃ at 8℃ / min; then cooled to 100℃ at 15℃ / min and air-cooled to room temperature.

[0072] Comparative Example 5: The wind turbine main shaft is made of 34CrNiMo6 alloy. Compared with Experimental Example 1, the difference is that the amorphous alloy powder adopts the amorphous alloy powder (Co 0.33 Ni 0.33 Cr 0.23 Mo 0.1 ) 76 Nb4(B 0.3 Si 0.7 ) 20 The preparation method can be found in the Journal of Alloys and Compounds 2023 document "Microstructure, mechanical properties and tribological behaviors of (Co 0.33 Ni 0.33 Cr 0.23 Mo 0.1 ) 80-x Nbx(B 0.3 Si 0.7 ) 20 High entropy amorphous alloy coatings (authors Shuaishuai Zhu, Yuping Wu, Sheng Hong, Jiangbo Cheng, Zheng Wei, Baosen Zhang).

[0073] Comparative Example 6: The wind turbine main shaft is made of 34CrNiMo6 alloy. Compared with Experimental Example 1, the difference is that the thickness of the Cu crystallized transition layer is 510 μm; the thickness of the amorphous structure layer is 1000 μm.

[0074] Sample test items and methods are as follows:

[0075] (1) Life test: The test method adopts GB / T 24607-2023 Rolling bearing life reliability test and evaluation method;

[0076] (2) Wear resistance test: The test method adopts the pin-disc friction wear method of YB / T 6178-2024 metal material wear test;

[0077] (3) Corrosion resistance test: The test method adopts GB / T 10125-2021 artificial atmosphere corrosion test salt spray test.

[0078] The sample test results are shown in Table 3.

[0079] Table 3 Sample test results

[0080]

[0081] From the test results in Table 3, it can be seen that the lifespan, wear resistance and corrosion resistance of the samples of Comparative Examples 2-6 and Experimental Examples 1-3 are better than those of Comparative Example 1, indicating that surface coating treatment technology can improve the lifespan, wear resistance and corrosion resistance of wind turbine main shafts. However, the coating combination strategy (Comparative Examples 2, 3, 5, 6) or the heat treatment method (Comparative Example 4) all result in the performance of the surface-treated wind turbine main shafts of the comparative examples being far inferior to the samples of Experimental Examples 1-3. Among them, Comparative Examples 2, 3, 5, and 6 respectively involve a single coating strategy, changing the amorphous alloy powder material or thickness, etc. This shows that the material selection, thickness relationship, heat treatment method and thickness of the Cu crystallized transition layer of the amorphous structure layer can significantly affect the performance of the surface-treated wind turbine main shaft. Among them, the Cu crystallized transition layer requires a specific thickness relationship to form an effective match with the amorphous structure layer, and together with the help of the four-stage gradient heat treatment process, the performance parameters of the wind turbine main shaft are improved. The samples of Experimental Examples 1-3 have greatly improved the wear resistance, hardness and life of the wind turbine main shaft based on the material selection, thickness relationship, heat treatment method and thickness of the Cu crystallization transition layer of the specific amorphous structure layer, and the product performance has been greatly improved, making it more suitable for highly corrosive environments (such as wind power generation in marine environments) and highly abrasive environments (such as wind power generation in dusty environments).

Claims

1. A wind turbine main shaft with a surface coating, characterized in that: The wind turbine main shaft is composed of a wind turbine main shaft substrate, a Cu crystallized transition layer covering the wind turbine main shaft substrate, and an amorphous structure layer covering the Cu crystallized transition layer; the X-ray diffraction pattern of the Cu crystallized transition layer presents a Cu (111) peak; the X-ray diffraction pattern of the amorphous structure layer presents a steamed bun peak between 35° and 50°, and the amorphous degree calculated by MDIJade is more than 98%; the amorphous structure layer contains the following elements by mass percentage: Co: 27.5~28.0%; Ni: 27.0~28.0%; Cr: 18.0%~18.5%; Mo: 15.0%~15.5%; Nb: 7.5%~8.0%; Si: 2.9%~3.5%; the thickness of the Cu crystallization transition layer is 200~500μm; the thickness of the amorphous structure layer is 280~450μm; the preparation method of the wind turbine main shaft includes the following steps: S1 uses supersonic flame spraying equipment to spray Cu coating on the surface of the wind turbine main shaft substrate after ultrasonic shot peening; S2 uses a vacuum heat treatment furnace to perform crystallization treatment on the surface of the wind turbine main shaft after the Cu coating is sprayed in step S1 to form a Cu crystallized transition layer; S3 uses a supersonic flame spraying device to spray an amorphous alloy coating on the surface of the wind turbine main shaft formed with the Cu crystallized transition layer in step S2, wherein the amorphous alloy powder used in the amorphous alloy coating has a particle size range of 3 to 12 μm; S4 uses a vacuum heat treatment furnace to perform performance heat treatment on the surface of the wind turbine main shaft sprayed with amorphous alloy coating to form an amorphous structure layer; In step S1, the supersonic flame spraying process conditions are: oxygen 255L / min~280L / min, kerosene 58L / min~62L / min, spraying distance 224mm~254mm, powder feeding rate 35g / min~40g / min, auxiliary gas is hydrogen, and the flow rate is 12slpm~28slpm; In step S2, the crystallization process conditions are: vacuum degree 3.0×10 -4 Pa~1.0×10 -4 Pa, temperature 600℃~650℃, holding time 45min~70min; In step S3, the supersonic flame spraying process conditions are: oxygen 282L / min~295L / min, kerosene 63L / min~65L / min, spraying distance 212mm~237mm, powder feeding rate 35g / min~40g / min, auxiliary gas is hydrogen, and the flow rate is 18slpm~28slpm; In step S4, the heat treatment step is to first evacuate to 3.0×10 -4 ~1.0×10 -4 Pa, followed by a four-stage gradient heat treatment; the process of the four-stage gradient heat treatment is as follows: The first stage: heating at 6-10℃ / min to 650-680℃ and keeping warm for 1.5-2.5h; The second stage: cooling at 5-7°C / min to 485-515°C and then keeping warm for 0.9-1.5h; The third stage: cooling at 3-5°C / min to 240-250°C and then keeping warm for 0.8-1.2h; The fourth stage: cool to 100-120°C at 7-8°C / min, then take out and place in air to cool to room temperature.

2. The wind turbine main shaft with a surface coating according to claim 1, characterized in that: The wind turbine main shaft substrate is selected from one of 34CrNiMo6 alloy steel, GCr15 alloy steel, 40Cr alloy steel, and 42CrMo4 alloy steel.

3. The wind turbine main shaft with a surface coating according to claim 1, characterized in that: The amorphous alloy powder is prepared by vacuum air atomization method, which includes the following steps: F1 alloy smelting: Weigh the raw material powder according to the proportion and add it into a high-purity crucible. Under the protection of high-purity argon, use a medium-frequency induction melting furnace to melt the alloy into a completely liquid state. The melting temperature is controlled at 1550℃~1620℃ and the melting time is 30 min~45 min. F2 atomization powder making: The smelted alloy liquid flows into the insulation tank through the tundish and then into the atomization nozzle through the guide pipe. The annular gap nozzle is used, the nozzle diameter is 1.5mm~2mm, the nozzle outlet pressure is 10Mpa~20Mpa, and the alloy liquid is impacted by high-pressure argon gas at a speed of 1000m / s~1200m / s to atomize and break it into droplets. The atomized droplets are 1×10 -2 Pa~3×10 -2 In Pa environment, 1×10 6 K / s ~3×10 6 K / s cooling rate cooling; F3 powder collection: The cooled powder settles at the bottom of the atomization tower and is separated by a vibration screening system to obtain amorphous alloy powder with a particle size range that meets the requirements. The amorphous alloy powder is then immersed in deionized water for cleaning to remove surface oxides and residual gases. The powder is then centrifugally dried or dried with hot air to remove moisture, and then vacuum dried at 100°C~150°C for 2h~4h.

4. Use of a wind turbine main shaft with a surface coating as claimed in any one of claims 1 to 3 as a wind turbine main shaft for use in highly corrosive and / or highly abrasive environments.

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