Wind power main shaft and method for prolonging service life of wind power main shaft

Abstract

The invention discloses a wind power main shaft and a method for prolonging the service life of the wind power main shaft, and belongs to the technical field of wind power main shafts. The method comprises the steps that a nanocrystalline transition layer is prepared on the surface of a wind power main shaft base body; preparing a composite working layer on the surface of the nanocrystalline transition layer; carrying out post-treatment on the composite working layer; wherein the composite working layer comprises an inner layer, a middle layer and an outer layer; 5%-15% of nanoscale hard ceramic particles are dispersed and distributed in the binding phase of the inner layer; 20%-35% of nanoscale hard ceramic particles and 1%-5% of nanoscale solid lubricant particles are dispersed and distributed in the binding phase of the middle layer; and 15%-25% of nanoscale hard ceramic particles and 3%-8% of nanoscale solid lubricant particles are dispersed and distributed in the binding phase of the outer layer. By means of the method, the wind power spindle is high in bonding strength, reasonable in stress distribution and good in fatigue resistance, abrasion resistance and corrosion resistance, the service life of key parts of the wind power spindle is prolonged, and reliability is improved.

Description

Technical Field

[0001] This invention relates to the field of wind turbine main shaft technology, and more specifically, to a wind turbine main shaft and a method for extending its service life. Background Technology

[0002] As the core transmission component of wind turbine generators, the wind turbine main shaft is subjected to enormous alternating bending and torsional loads, as well as environmental erosion from wind, sand, humidity, and salt spray over long periods. Critical areas such as bearing positions and seals are prone to wear, fretting fatigue, and corrosion damage, leading to equipment downtime and extremely high maintenance costs. Current technologies often employ surface hardening, thermal spraying (such as high-speed oxy-fuel spraying of tungsten carbide coatings), or chrome plating for strengthening. However, these traditional technologies have the following drawbacks: the surface-hardened layer has a steep hardness gradient, easily causing stress concentration at the interface; the thermally sprayed coating has high porosity, and its bond with the substrate is mainly mechanical, making it prone to peeling under heavy impact; the chrome-plated layer has microcracks, and environmental pressures are increasing.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The purpose of this invention is to provide a wind turbine main shaft and a method for extending its service life, so as to solve or improve the above-mentioned technical problems.

[0005] This invention can be implemented as follows: In a first aspect, the present invention provides a method for improving the service life of a wind turbine main shaft, comprising the following steps: preparing a nanocrystalline transition layer made of Fe-based or Ni-based alloy on the surface of a wind turbine main shaft substrate; preparing a composite working layer on the surface of the nanocrystalline transition layer; and performing post-treatment on the composite working layer to form a dense nanocrystalline nitride layer on the surface of the composite working layer. The composite working layer includes an inner layer, a middle layer, and an outer layer; The inner layer uses Fe-based or Ni-based alloys as the binder phase, and by volume percentage, 5% to 15% of nano-sized hard ceramic particles are dispersed in the binder phase of the inner layer. The intermediate layer uses Fe-based or Ni-based alloys as the binder phase. By volume percentage, the binder phase of the intermediate layer contains 20% to 35% nano-sized hard ceramic particles and 1% to 5% nano-sized solid lubricant particles. The outer layer uses Fe-based or Ni-based alloy as the binder phase. By volume percentage, the binder phase of the outer layer contains 15% to 25% nano-sized hard ceramic particles and 3% to 8% nano-sized solid lubricant particles.

[0006] In an optional embodiment, the area to be strengthened on the surface of the wind turbine main shaft substrate is roughened and cleaned before the nanocrystalline transition layer is prepared.

[0007] In an optional implementation, the roughening and cleaning process includes: first performing sandblasting roughening, and then performing ultrasonic cleaning with alcohol.

[0008] In an optional implementation, a nanocrystalline transition layer is prepared using a high-speed laser cladding method; The scanning speed of high-speed laser cladding is 10 mm / s to 50 mm / s, and the laser power is 2 kW to 4 kW; the raw materials for preparing the nanocrystalline transition layer include Fe-based or Ni-based self-fluxing alloy powders.

[0009] In an optional embodiment, the nanocrystalline transition layer has at least one of the following characteristics: Feature 1: The thickness of the nanocrystalline transition layer is 50μm~150μm; Feature 2: The grain size of the nanocrystalline transition layer is 100nm~500nm; Feature 3: The nanocrystalline transition layer is metallurgically bonded to the substrate.

[0010] In an optional implementation, a coaxial powder-feeding laser cladding method is used to prepare the composite working layer; The raw materials for preparing the inner layer include Fe-based or Ni-based self-fluxing alloy powder and nano-sized hard ceramic particles; the preparation conditions for the inner layer include: laser power of 1kW~3kW and scanning speed of 10mm / s~50mm / s. The raw materials for preparing the intermediate layer include Fe-based or Ni-based self-fluxing alloy powder, nano-scale hard ceramic particles, and nano-scale solid lubricant particles; the preparation conditions for the intermediate layer include: laser power of 1kW~3kW and scanning speed of 10mm / s~50mm / s. The raw materials for preparing the outer layer include Fe-based or Ni-based self-fluxing alloy powder, nano-sized hard ceramic particles, and nano-sized solid lubricant particles; the preparation conditions for the outer layer include: laser power of 1kW~3kW and scanning speed of 10mm / s~50mm / s.

[0011] In an optional implementation, the composite working layer has at least one of the following characteristics: Feature 4: The nanoscale hard ceramic particles include at least one of tungsten carbide, titanium carbide, and alumina; Feature 5: The particle size of the nanoscale hard ceramic particles is 50nm~250nm; Feature 6: The nanoscale solid lubricant particles include at least one of hexagonal boron nitride and graphene; Feature 7: The total thickness of the composite working layer is 300μm~700μm; Feature 8: The thickness of the inner layer is 150μm~300μm; Feature 9: The thickness of the intermediate layer is 100μm~250μm; Feature 10: The thickness of the outer layer is 50μm~150μm.

[0012] In an optional embodiment, forming a dense nanocrystalline nitride layer includes: performing laser remelting scanning on the surface of the composite working layer and supplementing it with nitrogen protection to form a dense nanocrystalline nitride layer. The laser remelting conditions include: laser power of 1kW~3kW, scanning speed of 10mm / s~20mm / s, and spot diameter of 1mm~5mm.

[0013] In an optional embodiment, the method further includes hot isostatic pressing of the reinforcing layer formed by the composite working layer and the nanocrystalline nitride layer.

[0014] In an optional embodiment, the hot isostatic pressing treatment is carried out at 1000℃~1100℃ for 3h~5h.

[0015] Secondly, the present invention provides a wind turbine main shaft, which is prepared by any of the methods described in the foregoing embodiments.

[0016] In an optional implementation, the wind turbine main shaft has at least one of the following features: Feature 11: The bonding strength between the reinforcing layer and the substrate in the wind turbine main shaft is ≥405MPa; Feature 12: Surface hardness of wind turbine main shaft ≥ 800 HV 0.2 ; Feature 13: The wind turbine main shaft has a corrosion resistance time of ≥520h in the neutral salt spray test.

[0017] The beneficial effects of this invention include: In the method provided by this invention, the composite working layer exhibits a gradient in component content from the inside out. The inner layer of the composite working layer primarily enhances toughness, the middle layer primarily enhances wear resistance and reduces friction, and the outer layer primarily enhances corrosion resistance and wear resistance. Through the aforementioned functional zoning and gradient combination of the composite working layer, the structural layer on the surface of the wind turbine main shaft substrate can simultaneously possess high load-bearing capacity, excellent tribological properties, and environmental adaptability on a macroscopic level. Furthermore, by combining the nanocrystalline transition layer with the aforementioned composite working layer, a smooth transition from substrate to surface properties can be achieved, effectively alleviating the interfacial stress concentration problem caused by the mismatch between the coefficient of thermal expansion and the elastic modulus, and greatly improving the bonding strength between the structural layer on the substrate surface and the substrate.

[0018] The method provided by this invention can effectively strengthen the surface of the wind turbine main shaft, so that the structural layer on the surface of the wind turbine main shaft has a high bonding strength with the substrate. At the same time, it also has the advantages of reasonable stress distribution, fatigue resistance, wear resistance and corrosion resistance, which can effectively improve the service life and reliability of key parts of the wind turbine main shaft. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0020] The following is a detailed description of the wind turbine main shaft provided by the present invention and the method for improving its service life.

[0021] This invention provides a method for extending the service life of wind turbine main shafts, comprising the following steps: S0: Roughen and clean the area to be strengthened on the surface of the wind turbine main shaft substrate.

[0022] In some alternative implementations, the roughening and cleaning process may include: first roughening by sandblasting, and then ultrasonic cleaning with alcohol.

[0023] S1: A nanocrystalline transition layer made of Fe-based or Ni-based alloy is prepared on the surface of the wind turbine main shaft substrate.

[0024] In some alternative implementations, the nanocrystalline transition layer can be prepared using high-speed laser cladding or supersonic cold spraying.

[0025] When preparing the nanocrystalline transition layer using high-speed laser cladding, the scanning speed of the high-speed laser cladding can be 10 mm / s to 50 mm / s (e.g., 10 mm / s, 20 mm / s, 30 mm / s, 40 mm / s, or 50 mm / s), and the laser power can be 2 kW to 4 kW (e.g., 2 kW, 2.5 kW, 3 kW, 3.5 kW, or 4 kW). The raw materials for preparing the nanocrystalline transition layer can include Fe-based or Ni-based self-fluxing alloy powders. Specifically, the Fe-based self-fluxing alloy powder can include at least one of Fe320 powder and Fe60 powder; the Ni-based self-fluxing alloy powder can include at least one of Ni60A powder and Nano-structured Inconel 718 powder.

[0026] If the scanning speed of high-speed laser cladding is too low, it can easily lead to a sharp increase in the dilution rate, heat accumulation causing edge collapse or lumps.

[0027] In some alternative embodiments, the thickness of the nanocrystalline transition layer can be 50 μm to 150 μm, such as 50 μm, 80 μm, 100 μm, 120 μm or 150 μm, or other values ​​within the range of 50 μm to 150 μm.

[0028] If the thickness of the nanocrystalline transition layer is less than 50 μm, it is not conducive to interface stability; if the thickness of the nanocrystalline transition layer is greater than 150 μm, it is not conducive to heat dissipation and performance improvement.

[0029] In some alternative embodiments, the grain size of the nanocrystalline transition layer can be 100nm~500nm, such as 100nm, 200nm, 300nm, 400nm or 500nm, or other values ​​within the range of 100nm~500nm.

[0030] If the grain size of the nanocrystalline transition layer is less than 100 nm, it is not conducive to grain refinement of the transition layer; if the grain size of the nanocrystalline transition layer is greater than 500 nm, it is not conducive to the ductile-brittle balance of the material.

[0031] In some alternative implementations, the nanocrystalline transition layer is metallurgically bonded to the substrate.

[0032] In some alternative implementations, the coefficient of thermal expansion of the nanocrystalline transition layer is between that of the substrate and the composite working layer.

[0033] As mentioned above, by setting the aforementioned nanocrystalline transition layer, it can achieve the functions of fine grain strengthening, thermal control, and defect repair.

[0034] S2: A composite working layer is prepared on the surface of the nanocrystalline transition layer.

[0035] The composite working layer includes an inner layer, a middle layer, and an outer layer.

[0036] The inner layer uses an Fe-based or Ni-based alloy as the binder phase, and by volume percentage, the binder phase of the inner layer contains 5% to 15% nano-sized hard ceramic particles dispersed (preferably uniformly dispersed). That is, the volume percentage of nano-sized hard ceramic particles in the binder phase of the inner layer can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%, or other values ​​within the range of 5% to 15%.

[0037] In the aforementioned inner layer, nano-sized hard ceramic particles can improve toughness. If the volume percentage of nano-sized hard ceramic particles in the binder phase of the inner layer is less than 5%, it is difficult to effectively improve toughness. If the volume percentage of nano-sized hard ceramic particles in the binder phase of the inner layer is greater than 15%, it is easy to cause agglomeration and uncontrolled porosity, and exacerbate the mismatch of thermophysical properties.

[0038] The intermediate layer uses an Fe-based or Ni-based alloy as the binder phase. By volume percentage, the binder phase of the intermediate layer contains 20%–35% dispersed (preferably uniformly dispersed) nano-sized hard ceramic particles and 1%–5% nano-sized solid lubricant particles. That is, the volume percentage of nano-sized hard ceramic particles in the binder phase of the intermediate layer can be 20%, 22%, 25%, 28%, 30%, 32%, or 35%, or other values ​​within the range of 20%–35%. The volume percentage of nano-sized solid lubricant particles in the binder phase of the intermediate layer can be 1%, 2%, 3%, 4%, or 5%, or other values ​​within the range of 1%–5%.

[0039] In the aforementioned intermediate layer, nano-sized hard ceramic particles can also improve toughness, while nano-sized solid lubricant particles can improve wear resistance. If the volume percentage of nano-sized hard ceramic particles in the binder phase of the intermediate layer is less than 20%, it is not conducive to achieving "percolation strengthening" and crack deflection; if the volume percentage of nano-sized hard ceramic particles in the binder phase of the intermediate layer is greater than 35%, it is easy to cause discontinuity of the binder phase and embrittlement of the sintering neck. If the volume percentage of nano-sized solid lubricant particles in the binder phase of the intermediate layer is less than 1%, it is not conducive to the formation of a continuous lubricating film; if the volume percentage of nano-sized solid lubricant particles in the binder phase of the intermediate layer is greater than 5%, it is easy to cause strength collapse and induce coating peeling.

[0040] The outer layer uses an Fe-based or Ni-based alloy as the binder phase. By volume percentage, the binder phase of the outer layer contains 15%–25% (preferably uniformly dispersed) nano-sized hard ceramic particles and 3%–8% nano-sized solid lubricant particles. That is, the volume percentage of nano-sized hard ceramic particles in the binder phase of the outer layer can be 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, or 25%, or other values ​​within the range of 15%–25%. The volume percentage of nano-sized solid lubricant particles in the binder phase of the outer layer can be 3%, 4%, 5%, 6%, 7%, or 8%, or other values ​​within the range of 3%–8%.

[0041] In the aforementioned outer layer, nanoscale hard ceramic particles can also improve toughness, and nanoscale solid lubricant particles can also improve wear resistance. If the volume percentage of nanoscale hard ceramic particles in the binder phase of the outer layer is less than 15%, it is not conducive to the toughening effect of "crack bridging" and "wake shielding"; if the volume percentage of nanoscale hard ceramic particles in the binder phase of the outer layer is greater than 25%, it is prone to metal rheological instability and brittle spalling. If the volume percentage of nanoscale solid lubricant particles in the binder phase of the outer layer is less than 3%, it is not conducive to the formation of a "self-healing" transfer film; if the volume percentage of nanoscale solid lubricant particles in the binder phase of the outer layer is greater than 8%, it is prone to binder phase fragmentation and three-body abrasive wear.

[0042] Continuing from the above, the composition of the composite working layer varies gradually from the inside to the outside. The inner layer primarily enhances toughness, the middle layer improves wear resistance and reduces friction, and the outer layer enhances corrosion resistance and abrasion resistance. Through this functional zoning and gradient combination, the structural layer on the surface of the wind turbine main shaft substrate simultaneously possesses high load-bearing capacity, excellent tribological properties, and environmental adaptability on a macroscopic level. Furthermore, by combining the nanocrystalline transition layer with the aforementioned composite working layer, a smooth transition from substrate to surface properties can be achieved, effectively mitigating the interfacial stress concentration problem caused by the mismatch between thermal expansion coefficients and elastic moduli, and significantly improving the bonding strength between the structural layer on the substrate surface and the substrate.

[0043] In some alternative embodiments, the nanoscale hard ceramic particles may include at least one of tungsten carbide, titanium carbide, and alumina.

[0044] The particle size of nanoscale hard ceramic particles can be 50nm~250nm, such as 50nm, 80nm, 100nm, 120nm, 150nm, 180nm, 200nm, 220nm or 250nm, or other values ​​within the range of 50nm~250nm.

[0045] If the particle size of nanoscale hard ceramic particles is less than 50 nm, it is not conducive to dispersion uniformity and agglomeration control; if the particle size of nanoscale hard ceramic particles is greater than 250 nm, it is not conducive to achieving the "nano" effect and improving the fine grain strengthening effect.

[0046] In some alternative embodiments, the nanoscale solid lubricant particles may include at least one of hexagonal boron nitride and graphene.

[0047] In some alternative implementations, a coaxial powder-feeding laser cladding method can be used to prepare the composite working layer, which can ensure that the nanoparticles are uniformly dispersed and do not suffer severe burn-off or grain growth.

[0048] When preparing a composite working layer using a coaxial powder-feeding laser cladding method, the raw materials for the inner layer can include Fe-based or Ni-based self-fluxing alloy powders and nanoscale hard ceramic particles. The preparation conditions for the inner layer can include: laser power ranging from 1kW to 3kW (e.g., 1kW, 1.5kW, 2kW, 2.5kW, or 3kW), and scanning speed ranging from 10mm / s to 50mm / s (e.g., 10mm / s, 20mm / s, 30mm / s, 40mm / s, or 50mm / s).

[0049] The raw materials for preparing the intermediate layer may include Fe-based or Ni-based self-fluxing alloy powder, nano-sized hard ceramic particles, and nano-sized solid lubricant particles. The preparation conditions for the intermediate layer may include: a laser power of 1kW to 3kW (e.g., 1kW, 1.5kW, 2kW, 2.5kW, or 3kW), and a scanning speed of 10mm / s to 50mm / s (e.g., 10mm / s, 20mm / s, 30mm / s, 40mm / s, or 50mm / s).

[0050] The raw materials for preparing the outer layer may include Fe-based or Ni-based self-fluxing alloy powder, nano-sized hard ceramic particles, and nano-sized solid lubricant particles. The preparation conditions for the outer layer may include: a laser power of 1kW to 3kW (e.g., 1kW, 1.5kW, 2kW, 2.5kW, or 3kW), and a scanning speed of 10mm / s to 50mm / s (e.g., 10mm / s, 20mm / s, 30mm / s, 40mm / s, or 50mm / s).

[0051] The composition of the inner, middle and outer layers can be continuously gradient-transitioned by adjusting the material delivery ratio, thereby avoiding abrupt changes in interface properties.

[0052] In some alternative implementations, the total thickness of the composite working layer can be 300μm to 700μm, such as 300μm, 400μm, 500μm, 600μm or 700μm, or other values ​​within the range of 300μm to 700μm.

[0053] If the total thickness of the composite working layer is less than 300nm, it is not conducive to improving contact fatigue life and impact resistance; if the total thickness of the composite working layer is greater than 700nm, it is easy to cause compressive stress relaxation and interlaminar shear failure.

[0054] In some alternative embodiments, the thickness of the inner layer can be 150 μm to 300 μm, such as 150 μm, 200 μm, 250 μm, or 300 μm, or other values ​​within the range of 150 μm to 300 μm. The thickness of the intermediate layer can be 100 μm to 250 μm, such as 100 μm, 150 μm, 200 μm, or 250 μm, or other values ​​within the range of 100 μm to 250 μm. The thickness of the outer layer can be 50 μm to 150 μm, such as 50 μm, 100 μm, or 150 μm, or other values ​​within the range of 50 μm to 150 μm.

[0055] It should be emphasized that in the above-mentioned composite working layer, the thickness of the inner layer, the middle layer and the outer layer should be set within the above range, so as to achieve a strong and tough connection of the heterogeneous material system under the thermo-mechanical coupling field.

[0056] S3: Post-process the composite working layer to form a dense nanocrystalline nitride layer on the surface of the composite working layer.

[0057] In some alternative embodiments, forming a dense nanocrystalline nitride layer may include: performing laser remelting scanning on the surface of the composite working layer and supplementing it with nitrogen protection to form a dense nanocrystalline nitride layer, which can further improve corrosion resistance.

[0058] In some optional implementations, laser remelting conditions may include: a laser power of 1kW to 3kW (e.g., 1kW, 1.5kW, 2kW, 2.5kW, or 3kW), a scanning speed of 10mm / s to 20mm / s (e.g., 10mm / s, 15mm / s, or 20mm / s), and a spot diameter of 1mm to 5mm (e.g., 1mm, 2mm, 3mm, 4mm, or 5mm).

[0059] S4: Hot isostatic pressing is performed on the reinforcing layer formed by the composite working layer and the nitrided layer.

[0060] In some alternative embodiments, hot isostatic pressing can be carried out at 1000°C to 1100°C (e.g., 1000°C, 1050°C, or 1100°C) for 3 to 5 hours (e.g., 3 hours, 4 hours, or 5 hours).

[0061] The above-mentioned hot isostatic pressing treatment can eliminate intralayer defects and enhance interlayer bonding.

[0062] Furthermore, the wind turbine main shaft after hot isostatic pressing can be precision machined to obtain the preset target size.

[0063] In some alternative implementations, before roughening and cleaning, the stress distribution in key reinforcement areas can be determined by finite element analysis based on the specific service conditions, load spectrum and failure modes of the wind turbine main shaft, and then the thickness and composition gradient of each of the above structural layers can be simulated and optimized.

[0064] Accordingly, the present invention also provides a wind turbine main shaft, which is prepared by the above method.

[0065] In some optional implementations, the bonding strength between the reinforcing layer and the substrate in the wind turbine main shaft is ≥405MPa, such as 405MPa~420MPa.

[0066] In some optional implementations, the surface hardness of the wind turbine main shaft is ≥800 HV. 0.2 For example, it can be 800HV 0.2 ~820HV 0.2 .

[0067] In some optional implementations, the corrosion resistance time of the wind turbine main shaft in the neutral salt spray test is ≥520h, such as 520h~540h.

[0068] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0069] Example 1 This embodiment provides a method for improving the service life of onshore wind turbine main shafts (specifically, strengthening the surface of the wind turbine main shaft bearings), including the following steps: S0: The bearing surface of the wind turbine main shaft is roughened by sandblasting and ultrasonically cleaned with alcohol.

[0070] S1: A nanocrystalline transition layer is prepared on the surface of the cleaned bearing using a high-speed laser cladding method.

[0071] The raw material used in the preparation was Ni-based self-fluxing alloy (Ni60A) powder; the scanning speed of the high-speed laser cladding was 21 mm / s and the laser power was 3 kW; after cladding, rapid cooling was performed to prepare a nanocrystalline transition layer with a thickness of about 105 μm and a grain size of about 205 nm, which achieved complete metallurgical bonding with the bearing substrate.

[0072] S2: A gradient nanocomposite working layer is prepared on the surface of the nanocrystalline transition layer using a coaxial powder feeding laser cladding method.

[0073] Inner layer: The powder feed material is a composite powder of Ni60A alloy powder and nano-WC particles (average particle size 80nm); by volume percentage, the amount of nano-WC particles is 7.5% of the Ni60A alloy powder; the laser power is 3kW, the scanning speed is 10mm / s, and an inner layer with a thickness of approximately 195μm is prepared. The microhardness of this layer is approximately 645HV. 0.2 The fracture toughness KIC is calculated to be approximately 25% higher than that of the matrix.

[0074] Intermediate layer: The powder composition was dynamically adjusted to increase the amount of nano-WC particles to 25% of the Ni60A alloy powder (the amount of Ni60A alloy powder was the same as that used in the inner layer) by volume percentage. Simultaneously, nano-h-BN (hexagonal boron nitride) particles, comprising 3% of the Ni60A alloy powder, were incorporated as a solid lubricant. A laser power of 3kW and a scanning speed of 10mm / s were used to prepare an intermediate layer with a thickness of approximately 200μm. The peak hardness of this layer reached 850HV. 0.2 The coefficient of friction decreased to 0.35.

[0075] Outer layer: The powder composition was dynamically adjusted to reduce the amount of nano-WC particles to 18% of Ni60A alloy powder (the amount of Ni60A alloy powder was the same as that used in the preparation of the inner layer) by volume percentage, and the h-BN content was increased to 5% of Ni60A alloy powder; the laser power was 3kW, the scanning speed was 10mm / s, and an outer layer with a thickness of about 100μm was prepared.

[0076] S3: The surface of the above composite working layer is subjected to laser remelting scanning and nitrogen protection to form a dense nanocrystalline nitride layer with a thickness of about 5μm.

[0077] The laser remelting conditions include: laser power of 2kW, scanning speed of 15mm / s, and spot diameter of 3mm.

[0078] S4: The sample prepared in S3 is subjected to hot isostatic pressing at 1050℃ for 4 hours to eliminate residual stress and close the micropores.

[0079] S5: Grind the sample prepared in S4 to the designed size.

[0080] Example 2 This embodiment provides a method for improving the service life of onshore wind turbine main shafts (specifically, strengthening the surface of the wind turbine main shaft bearings), including the following steps: S0: The bearing surface of the wind turbine main shaft is roughened by sandblasting and ultrasonically cleaned with alcohol.

[0081] S1: A nanocrystalline transition layer is prepared on the surface of the cleaned bearing using a high-speed laser cladding method.

[0082] The raw material used in the preparation is Ni-based self-fluxing alloy (Ni60A) powder; the scanning speed of the high-speed laser cladding is 10 mm / s and the laser power is 2 kW; after cladding, rapid cooling is performed to prepare a nanocrystalline transition layer with a thickness of about 50 μm and a grain size of about 100 nm, which achieves complete metallurgical bonding with the bearing substrate.

[0083] S2: A gradient nanocomposite working layer is prepared on the surface of the nanocrystalline transition layer using a coaxial powder feeding laser cladding method.

[0084] Inner layer: The powder feed material is a composite powder of Ni60A alloy powder and nano-WC particles (average particle size 50nm); by volume percentage, the amount of nano-WC particles is 5% of the Ni60A alloy powder; the laser power is 1kW, the scanning speed is 50mm / s, and an inner layer with a thickness of approximately 300μm is prepared. The microhardness of this layer is approximately 680HV. 0.2 The fracture toughness KIC was calculated to be approximately 29% higher than that of the matrix.

[0085] Intermediate layer: The powder composition was dynamically adjusted to increase the amount of nano-WC particles to 20% of the Ni60A alloy powder (the amount of Ni60A alloy powder was the same as that used in the inner layer) by volume percentage. Simultaneously, 1% of nano-h-BN (hexagonal boron nitride) particles were incorporated as a solid lubricant. A laser power of 2kW and a scanning speed of 30mm / s were used to prepare an intermediate layer with a thickness of approximately 250μm. The peak hardness of this layer reached 865HV. 0.2 The coefficient of friction decreased to 0.36.

[0086] Outer layer: The powder composition is dynamically adjusted to reduce the amount of nano WC particles to 15% of Ni60A alloy powder (the amount of Ni60A alloy powder is the same as that used when preparing the inner layer) by volume percentage, and the h-BN content is increased to 3% of Ni60A alloy powder; the laser power is 1kW, the scanning speed is 50mm / s, and an outer layer with a thickness of about 150μm is prepared.

[0087] S3: The surface of the above composite working layer is subjected to laser remelting scanning and nitrogen protection to form a dense nanocrystalline nitride layer with a thickness of about 8μm.

[0088] The laser remelting conditions include: laser power of 1kW, scanning speed of 10mm / s, and spot diameter of 1mm.

[0089] S4: The sample prepared in S3 is subjected to hot isostatic pressing at 1050℃ for 4 hours to eliminate residual stress and close the micropores.

[0090] S5: Grind the sample prepared in S4 to the designed size.

[0091] Example 3 This embodiment provides a method for improving the service life of onshore wind turbine main shafts (specifically, strengthening the surface of the wind turbine main shaft bearings), including the following steps: S0: The bearing surface of the wind turbine main shaft is roughened by sandblasting and ultrasonically cleaned with alcohol.

[0092] S1: A nanocrystalline transition layer is prepared on the surface of the cleaned bearing using a high-speed laser cladding method.

[0093] The raw material used in the preparation is Ni-based self-fluxing alloy (Ni60A) powder; the scanning speed of the high-speed laser cladding is 50 mm / s and the laser power is 4 kW; after cladding, rapid cooling is performed to prepare a nanocrystalline transition layer with a thickness of about 150 μm and a grain size of about 500 nm, which achieves complete metallurgical bonding with the bearing substrate.

[0094] S2: A gradient nanocomposite working layer is prepared on the surface of the nanocrystalline transition layer using a coaxial powder feeding laser cladding method.

[0095] Inner layer: The powder feed material is a composite powder of Ni60A alloy powder and nano-WC particles (average particle size 250nm); by volume percentage, the amount of nano-WC particles is 15% of the Ni60A alloy powder; the laser power is 2kW, the scanning speed is 30mm / s, and an inner layer with a thickness of approximately 150μm is prepared. The microhardness of this layer is approximately 630HV. 0.2 The fracture toughness KIC was calculated to be approximately 23% higher than that of the matrix.

[0096] Intermediate layer: The powder composition was dynamically adjusted to increase the amount of nano-WC particles to 35% of the Ni60A alloy powder (the amount of Ni60A alloy powder was the same as that used in the inner layer) by volume percentage. Simultaneously, nano-h-BN (hexagonal boron nitride) particles, comprising 5% of the Ni60A alloy powder, were incorporated as a solid lubricant. A laser power of 1kW and a scanning speed of 50mm / s were used to prepare an intermediate layer with a thickness of approximately 100μm. The peak hardness of this layer reached 845HV. 0.2 The coefficient of friction decreased to 0.31.

[0097] Outer layer: The powder composition was dynamically adjusted to reduce the amount of nano-WC particles to 25% of Ni60A alloy powder (the amount of Ni60A alloy powder was the same as that used in the preparation of the inner layer) by volume percentage, and the h-BN content was increased to 8% of Ni60A alloy powder; the laser power was 2kW, the scanning speed was 10mm / s, and an outer layer with a thickness of about 50μm was prepared.

[0098] S3: The surface of the above composite working layer is subjected to laser remelting scanning and nitrogen protection to form a dense nanocrystalline nitride layer with a thickness of about 6μm.

[0099] The laser remelting conditions include: laser power of 3kW, scanning speed of 20mm / s, and spot diameter of 5mm.

[0100] S4: The sample prepared in S3 is subjected to hot isostatic pressing at 1050℃ for 4 hours to eliminate residual stress and close the micropores.

[0101] S5: Grind the sample prepared in S4 to the designed size.

[0102] Comparative Example 1 The difference between this comparative example and Example 1 is that no nanocrystalline transition layer was provided.

[0103] Comparative Example 2 The difference between this comparative example and Example 1 is that the thickness of the composite working layer remains unchanged, but the raw materials used for preparation are the same as those used for the inner layer of Example 1 (without the intermediate and outer layers).

[0104] Comparative Example 3 The difference between this comparative example and Example 1 is that the thickness of the composite working layer remains unchanged, but the raw materials used for preparation are the same as those used for the intermediate layer in Example 1 (without inner and outer layers).

[0105] Comparative Example 4 The difference between this comparative example and Example 1 is that the thickness of the composite working layer remains unchanged, but the raw materials used for preparation are the same as those used for the outer layer of Example 1 (without an inner layer and intermediate layer).

[0106] Comparative Example 5 The difference between this comparative example and Example 1 is that step S3 was not performed.

[0107] Comparative Example 6 The difference between this comparative example and Example 1 is that step S4 was not performed.

[0108] The performance of the wind turbine main shafts prepared in Examples 1-3 and Comparative Examples 1-6 was compared, and the results are shown in Table 1.

[0109] The bonding strength between the structural layer (including the composite working layer and the nanocrystalline nitride layer) and the substrate is tested according to GB / T8642, the surface hardness is tested according to GB / T 18449.1-2024, and the corrosion resistance is tested according to GB / T 10125-2021.

[0110] Table 1 Performance Results

[0111] Example 4 This embodiment provides a method for improving the service life of wind turbine main shafts in desert environments (specifically, strengthening the flange connection surface of the wind turbine main shaft), including the following steps: S0: The flange connection surface of the wind turbine main shaft is roughened by sandblasting and ultrasonically cleaned with alcohol.

[0112] S1: A nanocrystalline transition layer is prepared on the flange connection surface after cleaning using a high-speed laser cladding method.

[0113] The raw material used in the preparation is Ni-based self-fluxing alloy (Ni60A) powder; the scanning speed of the high-speed laser cladding is 30 mm / s and the laser power is 3 kW; after cladding, rapid cooling is performed to prepare a nanocrystalline transition layer with a thickness of about 120 μm and a grain size of about 480 nm, which achieves complete metallurgical bonding with the bearing substrate.

[0114] S2: A gradient nanocomposite working layer is prepared on the surface of the nanocrystalline transition layer using a coaxial powder feeding laser cladding method.

[0115] Inner layer: The powder feeding material is a composite powder of Ni60A alloy powder and nano TiC particles (average particle size of 250nm); by volume percentage, the amount of nano TiC particles is 7.5% of Ni60A alloy powder; the laser power is 2.5kW, the scanning speed is 35mm / s, and the inner layer with a thickness of about 280μm is prepared.

[0116] Intermediate layer: The powder composition is dynamically adjusted, and the amount of nano-TiC particles is increased to 30% of the Ni60A alloy powder by volume percentage (the amount of Ni60A alloy powder is the same as that used in the preparation of the inner layer). Simultaneously, microencapsulated nano-molybdenum disulfide, accounting for 3% of the Ni60A alloy powder, is incorporated as a solid lubricant. The laser power is 1.5kW, the scanning speed is 25mm / s, and an intermediate layer with a thickness of approximately 215μm is prepared.

[0117] Outer layer: The powder composition was dynamically adjusted to reduce the amount of nano-TiC particles to 20% of Ni60A alloy powder (the amount of Ni60A alloy powder was the same as that used in the preparation of the inner layer) by volume percentage, and the content of microencapsulated nano-molybdenum disulfide was increased to 5% of Ni60A alloy powder; the laser power was 2.1kW, the scanning speed was 45mm / s, and an outer layer with a thickness of about 110μm was prepared.

[0118] S3: The surface of the above composite working layer is subjected to laser remelting scanning and nitrogen protection to form a dense nanocrystalline nitride layer with a thickness of about 7μm.

[0119] The laser remelting conditions include: laser power of 2kW, scanning speed of 15mm / s, and spot diameter of 3mm.

[0120] S4: The sample prepared in S3 is subjected to hot isostatic pressing at 1050℃ for 4 hours to eliminate residual stress and close the micropores.

[0121] S5: Grind the sample prepared in S4 to the designed size.

[0122] The reinforced wind turbine main shaft prepared in this embodiment was subjected to sand erosion wear test and rotational bending corrosion fatigue test (load ±400MPa, frequency 50Hz, spraying sand-containing droplets). At the same time, the original unreinforced wind turbine main shaft was set up as a control and tested according to the same method and conditions.

[0123] The results showed that the unstrengthened control sample developed fatigue cracks and severe corrosion pits at stress concentration points after 2 million cycles; while the strengthened sample obtained in this embodiment showed only slight wear marks on the surface after 5 million cycles, with no fatigue crack initiation, demonstrating excellent resistance to multi-source damage.

[0124] In summary, the method provided by this invention can effectively strengthen the surface of the wind turbine main shaft, giving the structural layer on the surface of the wind turbine main shaft a high bonding strength with the substrate. It also has the advantages of reasonable stress distribution, fatigue resistance, wear resistance and corrosion resistance, which can effectively improve the service life and reliability of key parts of the wind turbine main shaft.

[0125] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for improving the service life of wind turbine main shafts, characterized in that, Includes the following steps: A nanocrystalline transition layer made of Fe-based or Ni-based alloy is prepared on the surface of the wind turbine main shaft substrate; a composite working layer is prepared on the surface of the nanocrystalline transition layer; and the composite working layer is post-treated to form a dense nanocrystalline nitride layer on the surface of the composite working layer. The composite working layer includes an inner layer, a middle layer, and an outer layer; The inner layer uses an Fe-based or Ni-based alloy as the binder phase, and by volume percentage, 5% to 15% of nano-sized hard ceramic particles are dispersed in the binder phase of the inner layer. The intermediate layer uses an Fe-based or Ni-based alloy as the binder phase, and by volume percentage, the binder phase of the intermediate layer contains 20% to 35% nano-sized hard ceramic particles and 1% to 5% nano-sized solid lubricant particles. The outer layer uses an Fe-based or Ni-based alloy as the binder phase, and by volume percentage, the binder phase of the outer layer contains 15% to 25% nano-sized hard ceramic particles and 3% to 8% nano-sized solid lubricant particles.

2. The method according to claim 1, characterized in that, Before preparing the nanocrystalline transition layer, the area to be strengthened on the surface of the wind turbine main shaft substrate is roughened and cleaned. Preferably, the roughening and cleaning treatment includes: first performing sandblasting roughening, and then performing alcohol ultrasonic cleaning.

3. The method according to claim 1, characterized in that, Nanocrystalline transition layers were prepared using high-speed laser cladding. The scanning speed of the high-speed laser cladding is 10 mm / s to 50 mm / s, and the laser power is 2 kW to 4 kW; the raw materials for preparing the nanocrystalline transition layer include Fe-based or Ni-based self-fluxing alloy powder.

4. The method according to any one of claims 1 to 3, characterized in that, The nanocrystalline transition layer has at least one of the following characteristics: Feature 1: The thickness of the nanocrystalline transition layer is 50μm~150μm; Feature 2: The grain size of the nanocrystalline transition layer is 100nm~500nm; Feature 3: The nanocrystalline transition layer is metallurgically bonded to the substrate.

5. The method according to claim 1, characterized in that, The composite working layer was prepared using a coaxial powder-feeding laser cladding method. The raw materials for preparing the inner layer include Fe-based or Ni-based self-fluxing alloy powder and nano-scale hard ceramic particles. The preparation conditions for the inner layer include: laser power of 1kW~3kW and scanning speed of 10mm / s~50mm / s; The raw materials for preparing the intermediate layer include Fe-based or Ni-based self-fluxing alloy powder, nano-scale hard ceramic particles, and nano-scale solid lubricant particles; the preparation conditions for the intermediate layer include: laser power of 1kW~3kW and scanning speed of 10mm / s~50mm / s. The raw materials for preparing the outer layer include Fe-based or Ni-based self-fluxing alloy powder, nano-scale hard ceramic particles, and nano-scale solid lubricant particles; the preparation conditions for the outer layer include: laser power of 1kW~3kW and scanning speed of 10mm / s~50mm / s.

6. The method according to claim 1 or 5, characterized in that, The composite working layer has at least one of the following characteristics: Feature 4: The nanoscale hard ceramic particles include at least one of tungsten carbide, titanium carbide, and alumina; Feature 5: The particle size of the nanoscale hard ceramic particles is 50nm~250nm; Feature 6: The nanoscale solid lubricant particles include at least one of hexagonal boron nitride and graphene; Feature 7: The total thickness of the composite working layer is 300μm~700μm; Feature 8: The thickness of the inner layer is 150μm~300μm; Feature 9: The thickness of the intermediate layer is 100μm~250μm; Feature 10: The thickness of the outer layer is 50μm~150μm.

7. The method according to claim 1, characterized in that, Forming a dense nanocrystalline nitride layer includes: performing laser remelting scanning on the surface of the composite working layer and supplementing it with nitrogen protection to form a dense nanocrystalline nitride layer; The laser remelting conditions include: laser power of 1kW~3kW, scanning speed of 10mm / s~20mm / s, and spot diameter of 1mm~5mm.

8. The method according to claim 1, characterized in that, It also includes: hot isostatic pressing treatment of the reinforcing layer formed by the composite working layer and the nitrided layer; Preferably, the hot isostatic pressing treatment is carried out at 1000℃~1100℃ for 3h~5h.

9. A wind turbine main shaft, characterized in that, It is prepared by the method described in any one of claims 1 to 8.

10. The wind turbine main shaft according to claim 9, characterized in that, The wind turbine main shaft has at least one of the following characteristics: Feature 11: The bonding strength between the reinforcing layer and the substrate in the wind turbine main shaft is ≥405MPa; Feature 12: The surface hardness of the wind turbine main shaft is ≥800HV 0.2 ; Feature 13: The wind turbine main shaft has a corrosion resistance time of ≥520h in the neutral salt spray test.

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