Rotor coaxial heat dissipation structure and manufacturing method thereof

Abstract

The application discloses a rotor coaxial heat dissipation structure and a manufacturing method thereof. The rotor coaxial heat dissipation structure is formed on the surface of a motor rotor shaft in sequence and comprises a gradient functional coating, which comprises a bottom layer for leading out winding heat, a transition layer for solid lubrication and PFPE heat-triggered slow release, and a surface layer for friction reduction and micro-crack repair. The surface layer is externally provided with a laser-processed micro-pit array and a spiral flow guide groove. The application adopts a three-layer collaborative structure of the gradient functional coating, constructs a gradient architecture of the bottom layer (a nano-enhanced phase for heat conduction) - the transition layer (directional whisker + slow-release lubrication) - the surface layer (magnetic response self-repairing), and solves the problem that the functions of heat management, wear resistance and self-repairing of a traditional coating are difficult to be compatible. Meanwhile, the combined design of the laser micro-pit array (liquid storage and drag reduction) and the spiral flow guide groove (strengthening the flow of cooling medium) cooperatively improves the heat dissipation efficiency.

Description

Technical Field

[0001] This invention relates to the field of motor rotor shaft technology, and more specifically, to a coaxial heat dissipation structure for rotors and its manufacturing method. Background Technology

[0002] With the widespread application of high-power-density motors in new energy vehicles, aerospace, and other fields, rotor shaft systems face severe thermal management and tribological challenges, becoming a key bottleneck restricting equipment performance improvement and service life. Existing technologies typically employ single-function coatings (such as thermally sprayed ceramic layers) or simple composite material coatings. Under harsh operating conditions of high temperature (>150℃) and high speed (>10,000 rpm), their inherent performance contradictions become increasingly prominent.

[0003] (1) Imbalance between heat dissipation and mechanical properties:

[0004] The literature (ASME J. Heat Transfer-2023) points out that although high thermal conductivity material systems (such as pure copper heat pipe structures) can effectively dissipate heat, they are difficult to meet the high fatigue strength (>800MPa) requirements of high-speed rotor shafts. While traditional thermal spray ceramic coatings such as Al2O3 / TiC can provide good mechanical protection, their inherent thermal conductivity is too low (<30 W / (m·K)), which leads to heat accumulation in the windings and seriously restricts the power density of the motor.

[0005] The carbon nanotube-reinforced copper matrix composite material (CNT / Cu) proposed in patent CN114231989A attempts to reconcile this contradiction, but it still suffers from insufficient interfacial bonding and thermal damage to the matrix material caused by excessively high densification sintering temperature (>900℃), which limits its large-scale application on precision rotor shafts.

[0006] (2) High-temperature failure of lubricating medium:

[0007] Although the perfluoropolyether (PFPE) based grease proposed in patent US2024035682 has good lubrication performance, it will lose its lubrication function due to significant viscosity loss caused by the thermal degradation and breakage of molecular chains in the high-temperature environment (>150℃) common in rotor systems (experimental data show that the viscosity loss rate is >50%). Microencapsulated ionic liquid technology, which was developed to improve lubrication durability, has a new limitation: the insufficient thermal stability of its core wall material (generally <180℃). At high temperatures, the wall material cracks or permeates, causing the slow-release to fail.

[0008] In view of this, the present invention proposes an innovative coaxial rotor heat dissipation structure. This structure precisely constructs a functional gradient coating system (comprising a three-layer synergistic structure of a base layer, a transition layer, and a surface layer) on the working surface of the rotor shaft body, aiming to significantly extend the effective service life of the coating while ensuring efficient heat dissipation and excellent lubrication performance, thereby improving the overall performance and reliability of high power density motor rotor systems. Summary of the Invention

[0009] To address the aforementioned technical problems, this invention provides, in one aspect, a rotor coaxial heat dissipation structure, a fluorine-containing metal-based lubricating composition, and the synergistic application of both in a motor rotor shaft. In the technical solution of this invention, the rotor coaxial heat dissipation structure comprises a gradient functional coating sequentially formed on the surface of the motor rotor shaft, including:

[0010] The bottom layer, with a thickness of 50-100μm, is composed of copper@graphene composite powder and aluminum nitride-carbon nanotube composite, wherein the copper-based graphene composite powder accounts for 80-85wt% and the aluminum nitride-carbon nanotube accounts for 15-20wt%, and is used to conduct heat out of the winding.

[0011] The transition layer, with a thickness of 30-40 μm, is composed of calcium fluoride nanowires, ZIF-8 encapsulated perfluoropolyether, and tungsten disulfide nanosheets, wherein the calcium fluoride nanowires account for 20-45 wt%, the ZIF-8 encapsulated perfluoropolyether accounts for 40-45 wt%, and the tungsten disulfide nanosheets account for 15-20 wt%. The vertical orientation of the calcium fluoride nanowire whiskers is achieved with the assistance of an electrostatic field, which is used for solid lubrication and PFPE thermally triggered slow release.

[0012] The surface layer, with a thickness of 5-10 μm, is composed of tungsten disulfide nanosheets and microencapsulated ionic liquid containing Fe3O4 magnetic cores, wherein the tungsten disulfide nanosheets account for 70-75 wt% and the microencapsulated ionic liquid containing Fe3O4 magnetic cores accounts for 25-30 wt%, and is used for friction reduction and microcrack repair.

[0013] The outer surface layer features a laser-processed array of micro-pits, with specific dimensions of 80±5μm in diameter, 20±2μm in depth, and a density of 15 pits / mm. 2 It features a spiral guide groove with an inclination angle of 25° and a pitch of 200μm.

[0014] Furthermore, in the technical solution of the present invention, the microencapsulated ionic liquid containing Fe3O4 magnetic core is positioned to a depth of 1-3 μm from the outer wall of the surface by a 0.3T magnetic field.

[0015] A fluorine-containing metal-based lubricating composition comprises: component A, component B, and component C;

[0016] Specifically:

[0017] Component A, by mass percentage, includes:

[0018] Copper@graphene composite powder 80%–85%;

[0019] Aluminum nitride-carbon nanotubes: 15%–20%.

[0020] Component B, by mass percentage, includes:

[0021] Calcium fluoride nanowires: 20%–45%;

[0022] Tungsten disulfide nanosheets: 15%–20%;

[0023] ZIF-8 encapsulation uses 40%–45% perfluoropolyether;

[0024] Component C, by mass percentage, includes:

[0025] Microencapsulated ionic liquids containing Fe3O4 magnetic cores comprise 25%–30%;

[0026] 70%–75% tungsten disulfide nanosheets.

[0027] Furthermore, in the technical solution of this invention, the preparation steps of ZIF-8 encapsulated perfluoropolyether are as follows:

[0028] ZIF-8 powder is pre-impregnated with acetone for 1-2 hours, controlling the volume expansion to be no less than 20%, followed by vacuum dehydration at 150℃ for 2 hours; perfluoropolyether PFPE is preheated to 60℃ to reduce viscosity; and then mixed at a ratio of ZIF-8:PFPE = 1:1.2-1.3 (wt).

[0029] Inject into the vacuum reactor, program control: after 30 min, the vacuum drops to 0.1 Pa, the temperature rises to 80 °C, and the pressure is increased in stages from 0.1 MPa to 5 MPa at a rate of 1 MPa / 30 min, and the pressure is maintained at 5 MPa for 4 h.

[0030] Rapidly cool to -20°C to freeze the encapsulation structure and obtain the PFPE@ZIF-8 structure.

[0031] Furthermore, in the technical solution of the present invention, the kinematic viscosity of the perfluoropolyether is 80-500 cSt.

[0032] Furthermore, in the technical solution of the present invention, the microencapsulated ionic liquid containing Fe3O4 magnetic core has a particle size distribution of 2-5 μm, a wall thickness uniformity CV value of <8%, an ionic liquid encapsulation rate of ≥92%, and a thermal stability of >200℃.

[0033] Furthermore, in the technical solution of the present invention, the microencapsulated ionic liquid wall material containing Fe3O4 magnetic cores is polyurea-formaldehyde or melamine, and the Fe3O4 magnetic core content is 5-10 wt%, which is encapsulated in the wall material by interfacial polymerization.

[0034] Furthermore, in the technical solution of the present invention, the ionic liquid is specifically any one of 1-butyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, and 1-hydroxyethyl-3-methylimidazolium tetrafluoroborate.

[0035] The application of a coaxial heat dissipation structure and a fluorine-containing metal-based lubricating composition in the rotor shaft of an electric motor includes the following steps:

[0036] ①The rotor shaft surface is subjected to sandblasting roughening, laser cleaning, preheating to 300℃, and constant temperature for 30 minutes.

[0037] ② By spraying with supersonic flame, 80-85wt% copper@graphene composite powder and 15-20wt% aluminum nitride-carbon nanotube mixture are sprayed to form a base layer with a thickness of 50-55μm on the surface of the rotor shaft.

[0038] ③ By atmospheric plasma spraying, a mixture of 20-45wt% calcium fluoride nanowires, 40-45wt% PFPE@ZIF-8 and 15-20wt% tungsten disulfide nanosheets is sprayed onto the bottom layer to form a transition layer with a thickness of 25-30μm.

[0039] ④ By low-temperature cold spraying, with N2 pressure of 4MPa, carrier gas temperature of 150℃, and magnetic field positioning of 0.3T, 70-75wt% of tungsten disulfide nanosheets and 25-30wt% of microencapsulated ionic liquid mixture containing Fe3O4 magnetic cores are sprayed onto the transition layer to form a surface layer with a thickness of 5-8μm.

[0040] ⑤ A micro-dimple array is fabricated on the surface using a femtosecond laser, with a diameter of 80±5μm, a depth of 20±2μm, and a density of 15 pits / mm. 2 And spiral guide grooves, with an inclination angle of 25° and a pitch of 200μm;

[0041] ⑥ By spark plasma sintering at 650℃ and 75MPa for 5 minutes;

[0042] ⑦ When assembling the equipment for the first time, a small amount of PFPE grease should be pre-applied to the bearing housing, with a thickness of ≤10μm.

[0043] Effective gain:

[0044] In the technical solution of this invention, by adopting a three-layer synergistic structure of gradient functional coating, a gradient architecture is constructed with a bottom layer (heat-conducting nano-reinforcing phase) - a transition layer (directional whiskers + slow-release lubrication) - a surface layer (magnetic response self-healing), which solves the problem of incompatibility between the thermal management / wear resistance / self-healing functions of traditional coatings; at the same time, the combined design of laser micro-pit array (liquid storage and drag reduction) and spiral flow-guiding groove (enhancing the flow of cooling medium) synergistically improves heat dissipation efficiency.

[0045] Furthermore, the "pre-swelling-gradient pressurization" process achieves a PFPE encapsulation rate of >90% in the ZIF-8 channels, overcoming the high-temperature volatility defect of traditional lubricants. The Fe3O4 magnetic core microcapsules are precisely positioned 10-30μm below the surface under a 0.3T magnetic field, enabling targeted repair of wear areas.

[0046] Finally, using aluminum nitride-carbon nanotubes as the interface strengthening phase, CNTs are vertically grown to form a nano-fence, and AlN bridges the thermal conductivity, reducing the interfacial thermal resistance and enhancing thermal conductivity. At the same time, it acts as a migration barrier to prevent the fluorine-containing components from escaping due to centrifugal force.

[0047] Other features and advantages of the present invention will be set forth in the following description. Attached Figure Description

[0048] To more clearly illustrate the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0049] Figure 1 This is a schematic diagram of the application process of the rotor coaxial heat dissipation structure with a fluorine-containing metal-based lubricating composition on the surface of the present invention.

[0050] Figure 2 This is a schematic diagram of the cross-sectional distribution of the coaxial heat dissipation structure on the rotor shaft surface of the present invention.

[0051] Among them, 1 is the rotor shaft, 2 is the bottom layer, 3 is the transition layer, and 4 is the surface layer. Detailed Implementation

[0052] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0053] This invention proposes a rotor coaxial heat dissipation structure, such as... Figure 2 As shown, the gradient functional coating, which is sequentially formed on the surface of the motor rotor shaft 1, includes:

[0054] The bottom layer 2 (50-100μm) is composed of copper-based graphene composite powder (Cu@Gr) and aluminum nitride-carbon nanotube composite (AlN-CNT), with Cu@Gr accounting for 80-85wt% and AlN-CNT accounting for 15-20wt%, and has a thermal conductivity >400 W / (m·K), which is used to dissipate heat from the winding.

[0055] The transition layer 3 (30-40 μm) is composed of calcium fluoride nanowires (CaF2 NWs), ZIF-8 encapsulated perfluoropolyether (PFPE@ZIF-8), and tungsten disulfide nanosheets (WS2), wherein CaF2 NWs account for 20-45 wt%, PFPE@ZIF-8 accounts for 40-45 wt%, and WS2 accounts for 15-20 wt%. The vertical orientation of CaF2 whiskers (orientation deviation <10°) is achieved with the assistance of an electrostatic field, which is used for solid lubrication and thermally triggered slow release of PFPE.

[0056] The surface layer 4 (5-10 μm) consists of tungsten disulfide nanosheets (WS2) and microencapsulated ionic liquid containing Fe3O4 magnetic cores, with WS2 accounting for 70-75 wt% and microencapsulated ionic liquid containing Fe3O4 magnetic cores accounting for 25-30 wt%. The surface is equipped with a laser-processed micro-dimple array (diameter 80±5 μm, depth 20±2 μm, density 15 pits / mm²) and spiral guide grooves (inclination angle 25°, pitch 200 μm) for friction reduction and microcrack repair.

[0057] Among them, the microencapsulated ionic liquid contains a magnetic Fe3O4 core, which is positioned to a depth of 1-3 μm from the outer wall of the surface by a 0.3T magnetic field;

[0058] The PFPE@ZIF-8 package triggers a controlled release of PFPE in response to bearing temperature rise (>120°C) in the transition layer.

[0059] Furthermore, the total thickness of the gradient coating is 80±8μm, and the porosity is <2% after spark plasma sintering (SPS) (700℃ / 80MPa / 5min); the bottom layer is formed by high-velocity oxygen fuel spraying (HVOF) with a flame velocity ≥2400 m / s; the transition layer is formed by atmospheric plasma spraying (APS) with a current of 500A and an electrostatic field strength of 15kV / cm; and the surface layer is formed by low-temperature cold spraying with a nitrogen pressure of 4MPa and a carrier gas temperature ≤150℃.

[0060] Another aspect of the present invention provides a fluorine-containing metal-based lubricating composition, comprising: component A, component B and component C;

[0061] Specifically:

[0062] Component A, by mass percentage, includes:

[0063] Copper@graphene composite powder 80%–85%;

[0064] Aluminum nitride-carbon nanotubes: 15%–20%.

[0065] Component B, by mass percentage, includes:

[0066] Calcium fluoride nanowires: 20%–45%;

[0067] Tungsten disulfide nanosheets: 15%–20%;

[0068] ZIF-8 encapsulation uses 40%–45% perfluoropolyether;

[0069] Component C, by mass percentage, includes:

[0070] Microencapsulated ionic liquids containing Fe3O4 magnetic cores comprise 25%–30%;

[0071] 70%–75% tungsten disulfide nanosheets.

[0072] In this embodiment, Cu@Gr composite powder is formed by ball milling Cu powder and graphene at 400 rpm for 2 hours. Specifically, the Cu powder is a spherical gas-atomized powder with a particle size D50 of 45 ± 5 μm; the graphene has 5-8 layers with a sheet diameter of 20-50 μm. The Cu:Gr mass ratio is 92:8 (wt%). The Cu@Gr composite powder provides mechanical support through a thermally conductive framework, while the graphene enhances the thermal conductivity of the copper-based material (≥450 W / mK), and the coating structure inhibits copper oxidation.

[0073] In this embodiment, calcium fluoride nanowires (CaF2 NWs) are selected from Zhejiang Yanano Materials, model YNM-CF50, with a diameter of 60±20nm and a length of 8-30μm; tungsten disulfide nanosheets are selected from Hexagonal Nanotechnology, model HN-WS2-100, with a sheet diameter of 100±20nm and 2-4 layers. Calcium fluoride nanowires serve as a high-temperature lubrication core; the nanowires interweave to form a self-lubricating network (stable at 600℃), releasing Ca... 2+ Tungsten disulfide nanosheets, acting as friction-reducing and reinforcing agents, repair worn surfaces. Their layered structure undergoes shear slip (reducing the friction coefficient to 0.08), synergistically forming a transfer film with CaF2.

[0074] In this embodiment, ZIF-8 encapsulates perfluoropolyether (PFPE@ZIF-8) as a long-term lubrication guarantee. ZIF-8 can control the release of PFPE to avoid sudden migration.

[0075] The preparation steps for ZIF-8 encapsulated perfluoropolyether are as follows:

[0076] ZIF-8 powder is pre-impregnated with acetone for 1-2 hours, controlling the volume expansion to be no less than 20%, followed by vacuum dehydration at 150℃ for 2 hours; perfluoropolyether (PFPE) is preheated to 60℃ to reduce viscosity; and then mixed at a ratio of ZIF-8:PFPE = 1:1.2-1.3 (wt).

[0077] Inject into the vacuum reactor, program control: vacuum to 0.1 Pa (30 min), heat to 80℃ (PFPE viscosity decreases from 280 cP to 40 cP), gradient pressurization: pressurize stepwise from 0.1 MPa to 5 MPa (increase by 1 MPa every 30 min), pressurize to 5 MPa and hold for 4 h;

[0078] Rapidly cool to -20°C to freeze the encapsulation structure and obtain the PFPE@ZIF-8 structure.

[0079] Furthermore, the kinematic viscosity (KV) of the perfluoropolyether is preferably 80-500 cSt. Excessively high viscosity hinders penetration, while excessively low viscosity makes it difficult to form an effective lubricating film. In this embodiment, the specific perfluoropolyether type is at least one of Krytox GPL 205, Fomblin Y LVAC 18 / 8, DAPLEX D-80PF, DEMNμm S-65, and Molykote PF-50E.

[0080] Understandably, at low temperatures, the ZIF-8 channels shrink and lock the PFPE. At high temperatures, friction causes the channels to expand, releasing the PFPE as needed for lubrication. After wear, calcium fluoride / tungsten disulfide provides relay lubrication, offering dual lubrication protection.

[0081] In this embodiment, microencapsulated ionic liquid containing Fe3O4 magnetic cores is used as a self-healing agent. The capsules rupture to release the ionic liquid to fill the micro-pits (repair response time <10s), which is used for emergency repair of wear.

[0082] Among them, the microencapsulated ionic liquid wall material containing Fe3O4 magnetic core is polyurea-formaldehyde or melamine; the ionic liquid is any one of 1-butyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, or 1-hydroxyethyl-3-methylimidazolium tetrafluoroborate; the Fe3O4 magnetic core content is 5-10 wt%, which is pre-emulsified and dispersed in the oil phase, and then formed into microcapsules by interfacial polymerization.

[0083] Furthermore, the microencapsulated ionic liquid containing Fe3O4 magnetic cores has a particle size distribution of 2-5 μm, a wall thickness uniformity CV value of <8%, an ionic liquid encapsulation efficiency of ≥92%, and a thermal stability of >200℃.

[0084] It is understandable that microencapsulated ionic liquids containing Fe3O4 magnetic cores are enriched in the 1-3 μm depth range from the coating surface by a 0.3T magnetic field. When microcracks are generated by friction in the coating, stress concentration causes the capsules to rupture, and the ionic liquid seeps out. The ionic liquid undergoes physical filling through capillary penetration. At the same time, the active groups of the ionic liquid chemically bond with the metal to form metal complexes for chemical repair. It also forms an ionic liquid-solid composite film with CaF2 / WS2 for synergistic lubrication.

[0085] Specifically, 1-butyl-3-methylimidazolium hexafluorophosphate forms Fe-N coordination bonds between the N atom of the imidazolium ring and the exposed iron atom, PF6. - Hydrolyzes to PO4 3- A ferric phosphate film is formed, inhibiting electrochemical corrosion; the imidazole ring of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt is adsorbed on the nascent metal surface, forming an electric double layer barrier, SO2-N - -SO2CF3 releases F - FeF2 ceramic film is formed with Fe; the hydroxyethyl (-CH2CH2OH) in 1-hydroxyethyl-3-methylimidazolium tetrafluoroborate bonds with the coating polymer chain through hydrogen bonding to repair the interfacial molecular bridges, BF4 - Hydrolysis produces B2O3 and F - It reacts with the metal to form Fe2B / FeF2 nano-ceramic layers.

[0086] In this embodiment, aluminum nitride-carbon nanotubes (AlN-CNT) serve as the interface strengthening phase. CNTs are grown vertically to form nanofences, while AlN bridges the thermal conductivity, reducing the interfacial thermal resistance and enhancing thermal conductivity. At the same time, it acts as a migration barrier to prevent fluorine-containing components from escaping due to centrifugal force.

[0087] This invention also proposes the application of a rotor coaxial heat dissipation structure and a fluorine-containing metal-based lubricating composition in synergy in the rotor shaft of a motor, comprising the following steps:

[0088] ① The rotor shaft surface is roughened by sandblasting to increase the contact area, Ra=4.0μm; laser cleaning is performed at a power of 1.5kW and a scanning speed of 5m / s to remove the oxide layer; preheating is carried out at 300℃ for 30min to reduce thermal stress.

[0089] ②Using high-velocity flame spraying (HVOF) with a flame velocity of 2400 m / s, an oxygen flow rate of 900 L / h, and a substrate preheating of 400 °C, a mixture of 80-85 wt% Cu@Gr and 15-20 wt% AlN-CNT is sprayed to form a 50-55 μm thick base layer on the rotor shaft surface.

[0090] ③ By using atmospheric plasma spraying (APS), with a current of 500A, a powder feed rate of 35g / min, and an electrostatic field of 15kV / cm, a mixture of 20-45wt%CaF2 nanowires, 40-45wt%PFPE@ZIF-8 and 15-20wt%WS2 is sprayed onto the substrate to form a transition layer with a thickness of 25-30μm.

[0091] ④ By low-temperature cold spraying, with N2 pressure of 4MPa, carrier gas temperature of 150℃, and magnetic field positioning of 0.3T, a mixture of 70-75wt% WS2 and 25-30wt% microencapsulated ionic liquid containing Fe3O4 magnetic cores is sprayed onto the transition layer to form a surface layer with a thickness of 5-8μm.

[0092] ⑤ A micro-dimple array (diameter 80±5μm, depth 20±2μm, density 15 pits / mm) is fabricated on the surface using a femtosecond laser (wavelength 1030nm, pulse width 200fs). 2 ) and spiral guide grooves (inclination angle 25°, pitch 200μm);

[0093] ⑥ The coating density is improved by spark plasma sintering (SPS) at 650℃ / 75MPa / 5min.

[0094] ⑦ When assembling the equipment for the first time, a small amount of PFPE grease (Krytox GPL 205) should be pre-applied to the bearing housing with a thickness of ≤10μm for extreme cold start protection.

[0095] To further understand the present invention, the following description, in conjunction with embodiments, illustrates a rotor coaxial heat dissipation structure with a fluorine-containing metal-based lubricating composition provided by the present invention. The scope of protection of the present invention is not limited by the following embodiments.

[0096] Experimental Example 1

[0097] Preparation of ZIF-8 encapsulated perfluoropolyether:

[0098] ① ZIF-8 powder was pre-impregnated with acetone for 1.5 hours, followed by vacuum dehydration at 150°C for 2 hours; Krytox GPL 205 perfluoropolyether (PFPE) was preheated to 60°C to reduce viscosity; and mixed at a ratio of ZIF-8:PFPE = 1:1.2 (wt).

[0099] ② Inject into the vacuum reactor, program control: vacuum to 0.1 Pa (30 min), heat to 80℃ and pressurize in a gradient: pressurize stepwise from 0.1 MPa to 5 MPa (increase by 1 MPa every 30 min), pressurize to 5 MPa and hold for 4 h;

[0100] ③ Rapidly cool to -20℃ to freeze the encapsulation structure and obtain the PFPE@ZIF-8 structure.

[0101] Experiment Example 2

[0102] Preparation of microencapsulated ionic liquids containing Fe3O4 magnetic cores:

[0103] Urea-formaldehyde prepolymer, Fe3O4 magnetic core, and 1-butyl-3-methylimidazolium hexafluorophosphate were emulsified and dispersed at a mass ratio of 0.9:0.1:1.3 at a homogenization speed of 8000 rpm for 15 min. Toluene diisocyanate (8 wt%) was added, and the mixture was cured at 60 °C and pH 3.5 for 4 h. After washing and filtration, a microencapsulated ionic liquid containing Fe3O4 magnetic core was obtained.

[0104] Experimental Example 3

[0105] Preparation of microencapsulated ionic liquids containing Fe3O4 magnetic cores:

[0106] Melamine prepolymer, Fe3O4 magnetic core, and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt were emulsified and dispersed at a mass ratio of 1:0.15:1.4 at a homogenization speed of 8000 rpm for 15 min. Toluene diisocyanate (8 wt%) was added, and the mixture was cured at 60 °C and pH 3.5 for 4 h. After washing and filtration, a microencapsulated ionic liquid containing Fe3O4 magnetic core was obtained.

[0107] Experiment Example 4

[0108] Urea-formaldehyde prepolymer, Fe3O4 magnetic core, and 1-hydroxyethyl-3-methylimidazolium tetrafluoroborate were emulsified and dispersed at a mass ratio of 1:0.13:1.5 at a homogenization speed of 8000 rpm for 15 min. Toluene diisocyanate (8 wt%) was added, and the mixture was cured at 60 °C and pH 3.5 for 4 h. After washing and filtration, a microencapsulated ionic liquid containing Fe3O4 magnetic core was obtained.

[0109] Experimental Example 5

[0110] Urea-formaldehyde prepolymer and 1-hydroxyethyl-3-methylimidazolium tetrafluoroborate were emulsified and dispersed at a mass ratio of 1:1.5 at a homogenization speed of 8000 rpm for 15 min. Toluene diisocyanate (8 wt%) was added, and the mixture was cured at 60 °C and pH 3.5 for 4 h. After washing and filtration, microencapsulated ionic liquid was obtained.

[0111] Application Example 1

[0112] ① The rotor shaft surface is roughened by sandblasting to increase the contact area, Ra=4.0μm; laser cleaning is performed at a power of 1.5kW and a scanning speed of 5m / s to remove the oxide layer; preheating is carried out at 300℃ for 30min to reduce thermal stress.

[0113] ②Using high-velocity flame spraying (HVOF) with a flame velocity of 2400 m / s, an oxygen flow rate of 900 L / h, and a substrate preheating of 400 °C, a mixture of 80 wt% Cu@Gr and 20 wt% AlN-CNT is sprayed to form a 50 μm thick underlayer on the rotor shaft surface.

[0114] ③ By using atmospheric plasma spraying (APS), with a current of 500A, a powder feed rate of 35g / min, and an electrostatic field of 15kV / cm, a mixture of 45wt% CaF2 nanowires, 40wt% PFPE@ZIF-8 prepared in Experimental Example 1, and 15wt% WS2 was sprayed onto the substrate to form a transition layer with a thickness of 25μm.

[0115] ④ By low-temperature cold spraying, with N2 pressure of 4MPa, carrier gas temperature of 150℃, and magnetic field positioning of 0.3T, 75wt% of WS2 and 25wt% of the microencapsulated ionic liquid mixture containing Fe3O4 magnetic core prepared in Experimental Example 2 were sprayed onto the transition layer to form a surface layer with a thickness of 6μm.

[0116] ⑤ A micro-dimple array (diameter 80±5μm, depth 20±2μm, density 15 pits / mm) is fabricated on the surface using a femtosecond laser (wavelength 1030nm, pulse width 200fs). 2 ) and spiral guide grooves (inclination angle 25°, pitch 200μm);

[0117] ⑥ The coating density is improved by spark plasma sintering (SPS) at 650℃ / 75MPa / 5min.

[0118] ⑦ When assembling the equipment for the first time, a small amount of PFPE grease (Krytox GPL 205) with a thickness of 8μm should be pre-applied to the bearing housing for extreme cold start protection.

[0119] Application Example 2

[0120] ① The rotor shaft surface is roughened by sandblasting to increase the contact area, Ra=4.0μm; laser cleaning is performed at a power of 1.5kW and a scanning speed of 5m / s to remove the oxide layer; preheating is carried out at 300℃ for 30min to reduce thermal stress.

[0121] ② A 53μm thick underlayer is formed on the rotor shaft surface by spraying a mixture of 85wt% Cu@Gr and 15wt% AlN-CNT through supersonic flame spraying (HVOF) with a flame velocity of 2400m / s, an oxygen flow rate of 900L / h, and a substrate preheating of 400℃.

[0122] ③ By using atmospheric plasma spraying (APS), with a current of 500A, a powder feed rate of 35g / min, and an electrostatic field of 15kV / cm, a mixture of 40wt% CaF2 nanowires, 40wt% PFPE@ZIF-8 prepared in Experimental Example 1, and 20wt% WS2 was sprayed onto the substrate to form a transition layer with a thickness of 28μm.

[0123] ④ By low-temperature cold spraying, with N2 pressure of 4MPa, carrier gas temperature of 150℃, and magnetic field positioning of 0.3T, 70wt% of WS2 and 30wt% of the microencapsulated ionic liquid mixture containing Fe3O4 magnetic core prepared in Experimental Example 3 were sprayed onto the transition layer to form a surface layer with a thickness of 8μm.

[0124] Steps ⑤, ⑥, and ⑦ are the same as in Application Example 1.

[0125] Application Example 3

[0126] ① The rotor shaft surface is roughened by sandblasting to increase the contact area, Ra=4.0μm; laser cleaning is performed at a power of 1.5kW and a scanning speed of 5m / s to remove the oxide layer; preheating is carried out at 300℃ for 30min to reduce thermal stress.

[0127] ② A 55μm thick underlayer is formed on the rotor shaft surface by spraying a mixture of 83wt% Cu@Gr and 17wt% AlN-CNT through supersonic flame spraying (HVOF) with a flame velocity of 2400m / s, an oxygen flow rate of 900L / h, and a substrate preheating of 400℃.

[0128] ③ By atmospheric plasma spraying (APS), with a current of 500A, a powder feed rate of 35g / min, and an electrostatic field of 15kV / cm, a mixture of 35wt% CaF2 nanowires, 45wt% PFPE@ZIF-8 prepared in Experimental Example 1, and 20wt% WS2 was sprayed onto the substrate to form a transition layer with a thickness of 30μm.

[0129] ④ By low-temperature cold spraying, with N2 pressure of 4MPa, carrier gas temperature of 150℃, and magnetic field positioning of 0.3T, 73wt% of WS2 and 27wt% of the microencapsulated ionic liquid mixture containing Fe3O4 magnetic core prepared in Experimental Example 4 were sprayed onto the transition layer to form a surface layer with a thickness of 6μm.

[0130] Steps ⑤, ⑥, and ⑦ are the same as in Application Example 1.

[0131] Comparative Example 1

[0132] The commercially available plasma-sprayed (APS) Al2O3-40%TiO2 rotor shaft is selected from Wafangdian Bearings, model ZWZAluCoat™.

[0133] Comparative Example 2

[0134] ① The rotor shaft surface is roughened by sandblasting to increase the contact area, Ra=4.0μm; laser cleaning is performed at a power of 1.5kW and a scanning speed of 5m / s to remove the oxide layer; preheating is carried out at 300℃ for 30min to reduce thermal stress.

[0135] ②Using high-velocity flame spraying (HVOF) with a flame velocity of 2400 m / s, an oxygen flow rate of 900 L / h, and a substrate preheating of 400 °C, Cu@Gr is sprayed to form a 55 μm thick underlayer on the rotor shaft surface.

[0136] Atmospheric plasma spraying (APS) was used to spray a mixture of 35 wt% CaF2 nanowires, 45 wt% PFPE@ZIF-8 prepared in Experimental Example 1, and 20 wt% WS2 onto the substrate to form a transition layer with a thickness of 30 μm. The mixture was sprayed on the substrate with a current of 500 A, a powder feed rate of 35 g / min, and an electrostatic field of 15 kV / cm.

[0137] By low-temperature cold spraying, with N2 pressure of 4 MPa, carrier gas temperature of 150°C, and magnetic field positioning of 0.3 T, 73 wt% WS2 and 27 wt% of microencapsulated ionic liquid mixture containing Fe3O4 magnetic core prepared in Experimental Example 4 were sprayed onto the transition layer to form a surface layer with a thickness of 6 μm.

[0138] Steps ③, ④, ⑤, ⑥, and ⑦ are the same as in Example 3.

[0139] Comparative Example 3

[0140] ① The rotor shaft surface is roughened by sandblasting to increase the contact area, Ra=4.0μm; laser cleaning is performed at a power of 1.5kW and a scanning speed of 5m / s to remove the oxide layer; preheating is carried out at 300℃ for 30min to reduce thermal stress.

[0141] ② A 55μm thick underlayer is formed on the rotor shaft surface by spraying a mixture of 83wt% Cu@Gr and 17wt% AlN-CNT through supersonic flame spraying (HVOF) with a flame velocity of 2400m / s, an oxygen flow rate of 900L / h, and a substrate preheating of 400℃.

[0142] Atmospheric plasma spraying (APS) with a current of 500A, a powder feed rate of 35g / min, and an electrostatic field of 15kV / cm, a mixture of 35wt% CaF2 nanowires, 45wt% Krytox GPL 205 perfluoropolyether (PFPE), and 20wt% WS2 was sprayed onto the substrate to form a transition layer with a thickness of 30μm.

[0143] By low-temperature cold spraying, with N2 pressure of 4 MPa, carrier gas temperature of 150°C, and magnetic field positioning of 0.3 T, 73 wt% WS2 and 27 wt% of microencapsulated ionic liquid mixture containing Fe3O4 magnetic core prepared in Experimental Example 4 were sprayed onto the transition layer to form a surface layer with a thickness of 6 μm.

[0144] Steps ③, ④, ⑤, ⑥, and ⑦ are the same as in Example 3.

[0145] Comparative Example 4

[0146] ① The rotor shaft surface is roughened by sandblasting to increase the contact area, Ra=4.0μm; laser cleaning is performed at a power of 1.5kW and a scanning speed of 5m / s to remove the oxide layer; preheating is carried out at 300℃ for 30min to reduce thermal stress.

[0147] ② A 55μm thick underlayer is formed on the rotor shaft surface by spraying a mixture of 83wt% Cu@Gr and 17wt% AlN-CNT through supersonic flame spraying (HVOF) with a flame velocity of 2400m / s, an oxygen flow rate of 900L / h, and a substrate preheating of 400℃.

[0148] Atmospheric plasma spraying (APS) was used to spray a mixture of 35 wt% CaF2 nanowires, 45 wt% PFPE@ZIF-8 prepared in Experimental Example 1, and 20 wt% WS2 onto the substrate to form a transition layer with a thickness of 30 μm. The mixture was sprayed on the substrate with a current of 500 A, a powder feed rate of 35 g / min, and an electrostatic field of 15 kV / cm.

[0149] By low-temperature cold spraying, with N2 pressure of 4 MPa, carrier gas temperature of 150°C, and magnetic field positioning of 0.3 T, a mixture of 73 wt% WS2 and 27 wt% microencapsulated ionic liquid prepared in Experimental Example 5 was sprayed onto the transition layer to form a surface layer with a thickness of 6 μm.

[0150] Steps ③, ④, ⑤, ⑥, and ⑦ are the same as in Example 3.

[0151] Comparative Example 5

[0152] Steps ①②③④ are the same as in application example 3;

[0153] ⑤ The coating density is improved by treating it with spark plasma sintering (SPS) at 650℃ / 75MPa / 5min;

[0154] ⑥ When assembling the equipment for the first time, a small amount of PFPE grease (Krytox GPL 205) with a thickness of 8μm should be pre-applied to the bearing housing for extreme cold start protection.

[0155] Test example:

[0156] The coating bonding strength of rotor shafts with heat dissipation structures prepared according to test cases 1-3 of ASTM C633 and comparative examples 1-5 was tested, and the test results are recorded in Table 1.

[0157] The thermal conductivity of the rotor shafts with heat dissipation structures prepared according to test cases 1-3 of LFA 467 and the rotor shaft coatings of comparative examples 1-5 were tested, and the test results are recorded in Table 1.

[0158] The rotor shafts with heat dissipation structures prepared according to test cases 1-3 of ASTM D2714 and the rotor shaft coating friction coefficients of comparative examples 1-5 were tested, and the test results are recorded in Table 1.

[0159] The coating repair performance of rotor shafts with heat dissipation structures prepared by artificial scratches (SEM observation) corresponding to cases 1-3 and comparative cases 1-5 was tested, and the test results are recorded in Table 1.

[0160] Table 1. Statistical Table of Performance Tests for Experimental Examples and Comparative Examples

[0161]

[0162] The temperature rise of the rotor shaft with heat dissipation structure prepared according to test case 1-3 of IEC 60034-29 and the rotor shaft coated bearing of comparative example 1-5 were tested, and the test results are recorded in Table 2.

[0163] Accelerated life tests were conducted on rotor shafts with heat dissipation structures prepared according to test cases 1-3 of ISO 281 and rotor shaft coatings of comparative examples 1-5, and the test results are recorded in Table 2.

[0164] Table 2. Statistical Table of Industrial Test Data for Experimental Examples and Comparative Examples

[0165]

[0166] In summary, this invention provides a rotor coaxial heat dissipation structure that applies a multi-level gradient functional coating structure to the surface of a high-speed motor rotor shaft to achieve synergistic optimization of thermal management, friction reduction and wear resistance, and self-repair functions. The functional gradient coating architecture includes a bottom layer, which is constructed by synergistically using copper@graphene composite powder and aluminum nitride-carbon nanotube composite to efficiently dissipate winding heat; a transition layer, which consists of electrostatically oriented calcium fluoride nanowires, ZIF-8 encapsulated perfluoropolyether, and tungsten disulfide nanosheets to improve solid lubrication performance and achieve controllable slow release of perfluoropolyether under operating conditions above 150°C; and a surface layer, in which tungsten disulfide nanosheets and microencapsulated ionic liquid containing Fe3O4 magnetic cores constitute an intelligent functional layer. Under a 0.3T magnetic field, the microcapsules are precisely positioned in the 10-30μm region below the surface to achieve targeted repair of microcracks.

[0167] Surface microstructure design: A micro-dimple array processed by femtosecond laser is used as a lubricant storage unit, combined with a 25° inclined spiral guide groove (200μm pitch) to enhance the turbulence intensity of the cooling medium and significantly improve the convective heat dissipation efficiency.

[0168] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A rotor coaxial heat dissipation structure, comprising a motor rotor shaft (1), characterized in that, The motor rotor shaft surface sequentially forms a gradient functional coating, comprising: a bottom layer (2) with a thickness of 50-100 μm, composed of copper@graphene composite powder and aluminum nitride-carbon nanotube composite, wherein the copper-based graphene composite powder accounts for 80-85 wt%, and the aluminum nitride-carbon nanotube accounts for 15-20 wt%, for exporting winding heat; a transition layer (3) with a thickness of 30-40 μm, composed of calcium fluoride nanowires, ZIF-8 encapsulated perfluoropolyether, and tungsten disulfide nanosheets, wherein the calcium fluoride nanowires account for 20-45 wt%, the ZIF-8 encapsulated perfluoropolyether accounts for 40-45 wt%, and the tungsten disulfide nanosheets account for 15-20 wt%, vertical orientation of calcium fluoride nanowire whiskers is achieved through electrostatic field assistance, for solid lubrication and PFPE thermal trigger slow release; a surface layer (4) with a thickness of 5-10 μm, composed of tungsten disulfide nanosheets and microencapsulated ionic liquids containing Fe3O4 magnetic cores, wherein the tungsten disulfide nanosheets account for 70-75 wt%, and the microencapsulated ionic liquids containing Fe3O4 magnetic cores account for 25-30 wt%, for friction reduction and microcrack repair; Wherein, the surface layer (4) is externally provided with a laser-processed micro-pit array, the micro-pit has a diameter of 80±5 μm, a depth of 20±2 μm, and a density of 15 pieces / mm 2 and a spiral flow guide groove with an inclination angle of 25° and a pitch of 200 μm.

2. The rotor coaxial heat dissipation structure according to claim 1, characterized in that, The microencapsulated ionic liquids containing Fe3O4 magnetic cores are positioned to a depth of 1-3 μm from the outer wall of the surface layer by a 0.3 T magnetic field.

3. A method of manufacturing the rotor coaxial heat dissipation structure according to claim 1 or 2, characterized by, The method comprises the following steps: ①The rotor shaft surface is sequentially sandblasted, laser cleaned, and preheated to 300℃ for 30 min; ②An 80-85 wt% copper@graphene composite powder and 15-20 wt% aluminum nitride-carbon nanotube mixture is sprayed on the rotor shaft surface by supersonic flame spraying to form a bottom layer with a thickness of 50-55 μm; ③A 20-45 wt% calcium fluoride nanowire, 40-45 wt% PFPE@ZIF-8, and 15-20 wt% tungsten disulfide nanosheet mixture is sprayed on the bottom layer by atmospheric plasma spraying to form a transition layer with a thickness of 25-30 μm; ④A 70-75 wt% tungsten disulfide nanosheet and 25-30 wt% microencapsulated ionic liquid containing Fe3O4 magnetic cores mixture is sprayed on the transition layer by low-temperature cold spraying at a N2 pressure of 4 MPa, a carrier gas of 150℃, and a magnetic field positioning of 0.3 T to form a surface layer with a thickness of 5-8 μm; (5) Micro-pit array with diameter of 80±5 μm, depth of 20±2 μm and density of 15 / mm is processed on the surface layer by femtosecond laser 2 and helical flow guide grooves with inclination angle of 25° and pitch of 200 μm; by spark plasma sintering at 650 °C, 75 MPa for 5 min; ⑥When the equipment is first assembled, a small amount of PFPE lubricating grease is pre-coated on the bearing seat with a thickness of ≤10 μm.

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