Rotor coaxial heat dissipation structure, fluorine-containing metal-based lubricating composition and application of cooperation of rotor coaxial heat dissipation structure and fluorine-containing metal-based lubricating composition in motor rotor shaft

Abstract

The invention discloses a rotor coaxial heat dissipation structure, a fluorine-containing metal-based lubricating composition and application of cooperation of the rotor coaxial heat dissipation structure and the fluorine-containing metal-based lubricating composition in a motor rotor shaft, and the rotor coaxial heat dissipation structure and gradient functional coatings sequentially formed on the surface of the motor rotor shaft comprise a bottom layer used for leading out winding heat; the transition layer is used for solid lubrication and PFPE heat triggering slow release; the surface layer is used for reducing friction and repairing microcracks; a micro-pit array and a spiral flow guide groove which are machined through laser are formed in the outer portion of the surface layer. According to the invention, a gradient functional coating three-layer synergistic structure is adopted to construct a gradient framework of a bottom layer (a heat conduction band nano reinforced phase), a transition layer (oriented whiskers and slow-release lubrication) and a surface layer (magnetic response self-repairing), so that the problem that heat management, wear resistance and self-repairing functions of a traditional coating are difficult to be compatible is solved; and meanwhile, through the combined design of the laser micro-pit array (liquid storage and resistance reduction) and the spiral flow guide groove (strengthening the flowing of the cooling medium), the heat dissipation efficiency is cooperatively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of motor rotor shafts, in particular to a rotor coaxial heat dissipation structure, a fluorine-containing metal-based lubricating composition, and their application in motor rotor shafts. BACKGROUND

[0002] With the wide application of high-power-density motors in new energy vehicles, aerospace and other fields, the rotor shaft system is facing severe thermal management and tribological challenges, which has become a key bottleneck restricting the performance improvement and service life of equipment. The existing technology usually uses single-function coatings (such as thermal sprayed ceramic layers) or simple composite material coatings, which have inherent performance contradictions that are increasingly prominent under harsh working conditions of high temperature (> 150℃) and high speed (> 10,000 rpm):

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

[0004] Literature (ASME J. Heat Transfer-2023) pointed out that high thermal conductivity material systems (such as pure copper heat pipe structure) can effectively dissipate heat, but it is difficult to meet the high fatigue strength (> 800MPa) requirements of high-speed rotor shafts, while traditional Al2O3 / TiC thermal sprayed ceramic coatings can provide better mechanical protection, but their inherent thermal conductivity is too low (< 30 W / (m·K)), which leads to heat accumulation around the winding, severely restricting the motor power density;

[0005] Patent CN114231989A proposes a carbon nanotube reinforced copper-based composite material (CNT / Cu) to try to coordinate this contradiction, but there are still problems of insufficient interfacial bonding force and thermal damage of the matrix material caused by too high densification sintering temperature (> 900℃), which limits its large-scale application in precision rotor shafts.

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

[0007] Patent US2024035682 proposes a perfluoropolyether (PFPE) based grease, which has good lubricating properties, but in the high temperature environment (> 150℃) commonly seen in rotor systems, the viscosity will be significantly lost (experimental data show that the viscosity loss rate is > 50%) due to thermal degradation and chain rupture of the molecular chain, losing the lubricating function; the core wall material of the microencapsulated ionic liquid technology developed to improve the lubrication durability has insufficient thermal stability (generally < 180℃), which constitutes a new limitation, and at high temperatures, the wall material breaks or penetrates, making the slow release ineffective.

[0008] In view of this, the application provides an innovative rotor coaxial heat dissipation structure. The structure is precisely constructed with a functional gradient coating system (including a three-layer cooperative structure of a bottom layer, a transition layer and a surface layer) on the working surface of the rotor shaft body, so as to significantly prolong the effective service life of the coating while ensuring efficient heat dissipation and excellent lubrication performance, and improve the overall performance and reliability of the high-power-density motor rotor system. SUMMARY

[0009] To solve the above technical problems, the application provides a rotor coaxial heat dissipation structure, a fluorine-containing metal-based lubricating composition and their application in a motor rotor shaft. In the technical solution of the application, the rotor coaxial heat dissipation structure is formed on the surface of the motor rotor shaft and sequentially includes a gradient functional coating.

[0010] The bottom layer has a thickness of 50-100 μm and is composed of copper-graphene composite powder and aluminum nitride-carbon nanotube composite, wherein the proportion of copper-graphene composite powder is 80-85 wt%, and the proportion of aluminum nitride-carbon nanotube is 15-20 wt%, and the bottom layer is used for heat dissipation of windings.

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

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

[0013] The surface layer is provided with a laser-processed micro-dimple array outside, and the micro-dimple has a diameter of 80±5 μm, a depth of 20±2 μm and a density of 15 / mm 2 and a spiral flow guide groove with an inclination angle of 25° and a pitch of 200 μm.

[0014] Further, in the technical solution of the application, 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 0.3T magnetic field.

[0015] A fluorine-containing metal-based lubricating composition includes 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 nanotube 15%~20%.

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

[0021] Calcium fluoride nanowire 20%~45%;

[0022] Tungsten disulfide nanosheet 15%~20%;

[0023] ZIF-8 encapsulated perfluoropolyether 40%~45%;

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

[0025] Microencapsulated ionic liquid containing Fe3O4 magnetic core 25%~30%;

[0026] Tungsten disulfide nanosheet 70%~75%.

[0027] Further, in the technical scheme of the present application, the preparation steps of ZIF-8 encapsulated perfluoropolyether are as follows:

[0028] ZIF-8 powder is pre-impregnated with acetone for 1-2h, with a volume expansion of not less than 20%, followed by vacuum dehydration at 150℃ for 2h; perfluoropolyether PFPE is preheated to 60℃ to reduce viscosity; mix according to ZIF-8:PFPE=1:1.2-1.3(wt);

[0029] Inject into a vacuum reactor, program control: 30min vacuum to 0.1Pa, temperature rise to 80℃, gradient pressure: from 0.1MPa to 5MPa stepwise pressure rise, pressure rise rate 1MPa / 30min, pressure rise to 5MPa for 4h;

[0030] Quickly cool to-20℃, freeze the encapsulation structure, and obtain PFPE@ZIF-8 structure.

[0031] Further, in the technical scheme of the present application, the kinematic viscosity of perfluoropolyether is 80-500cSt.

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

[0033] Further, in the technical scheme of the present application, the microencapsulated ionic liquid wall material containing Fe3O4 magnetic core is polyurea formaldehyde or melamine, and the content of Fe3O4 magnetic core is 5-10wt%.

[0034] Further, in the technical scheme of the present application, the ionic liquid is specifically any one of 1-butyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium bis-trifluoromethanesulfonimide, and 1-hydroxyethyl-3-methylimidazolium tetrafluoroborate.

[0035] A rotor coaxial heat dissipation structure and its application in a motor rotor shaft in cooperation with a fluorine-containing metal-based lubricating composition, comprising the following steps:

[0036] ①The surface of the rotor shaft is subjected to sand blasting roughening, laser cleaning, and preheating to 300℃, and constant temperature for 30min;

[0037] ②A bottom layer with a thickness of 50-55μm is formed on the surface of the rotor shaft by supersonic flame spraying of 80-85wt% copper@graphene composite powder and 15-20wt% aluminum nitride-carbon nanotube mixture;

[0038] ③A transition layer with a thickness of 25-30μm is formed on the bottom layer by atmospheric plasma spraying of 20-45wt% calcium fluoride nanowires, 40-45wt% PFPE@ZIF-8, and 15-20wt% tungsten disulfide nanosheet mixture;

[0039] ④A surface layer with a thickness of 5-8μm is formed on the transition layer by low-temperature cold spraying at N2 pressure of 4MPa, carrier gas of 150℃, and magnetic field positioning of 0.3T, spraying of 70-75wt% tungsten disulfide nanosheet and 25-30wt% microencapsulated ionic liquid containing Fe3O4 magnetic core mixture;

[0040] ⑤A micro-pit array is processed on the surface layer by femtosecond laser, with a diameter of 80±5μm, a depth of 20±2μm, and a density of 15 / mm 2 and a spiral flow guide groove with an inclination angle of 25° and a pitch of 200μm;

[0041] ⑥Discharge plasma sintering at 650℃, 75MPa, for 5min;

[0042] ⑦When the equipment is first assembled, a small amount of PFPE lubricating grease with a thickness of ≤10μm needs to be pre-coated on the bearing seat.

[0043] Effective gain:

[0044] In the technical scheme of the application, by adopting the three-layer synergistic structure of the gradient functional coating, the gradient architecture of the bottom layer (heat-conducting band nano-enhanced phase) - transition layer (directional whisker + slow-release lubrication) - surface layer (magnetic response self-repairing) is constructed, the problem that the traditional coating thermal management / wear resistance / self-repairing functions are difficult to be compatible is solved; and the combination design of the laser micro-pit array (liquid storage drag reduction) and the spiral flow guide groove (strengthening the flow of cooling medium) is used to synergistically improve the heat dissipation efficiency.

[0045] Moreover, the >90% encapsulation rate of PFPE in the ZIF-8 channel is realized through the "pre-swelling - gradient pressurization" process, the high-temperature volatility defect of the traditional lubricant is broken through, the Fe3O4 magnetic core microcapsule is accurately positioned to 10-30 mu m below the surface layer under the 0.3T magnetic field, and the wear area is targeted repaired.

[0046] Finally, by using aluminum nitride-carbon nanotube as an interface strengthening phase, the CNT is vertically grown to form a nano fence, the AlN is bridged to conduct heat, the interface thermal resistance is reduced, the heat conduction is enhanced, and as a migration barrier, the fluorine-containing component is prevented from escaping under the action of centrifugal force.

[0047] Other features and advantages of the present application will be set forth in the following description. BRIEF DESCRIPTION OF DRAWINGS

[0048] In order to more clearly illustrate the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0049] Figure 1 The application flow diagram of the rotor coaxial heat dissipation structure with the fluorine-containing metal-based lubricating composition on the surface of the present application is shown.

[0050] Figure 2 The cross-sectional distribution diagram of the rotor shaft surface coaxial heat dissipation structure of the present application is shown.

[0051] 1 rotor shaft, 2 bottom layer, 3 transition layer, 4 surface layer. DETAILED DESCRIPTION

[0052] In order to make the purpose, characteristics and advantages of the present application more obvious and easy to understand, the technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the embodiments described below are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0053] The application discloses a rotor coaxial heat dissipation structure, as shown in the figure, including a gradient functional coating formed on the surface of a motor rotor shaft 1 in sequence, comprising: Figure 2

[0054] A bottom layer 2 (50-100 μm) composed of copper-based graphene composite powder (Cu@Gr) and aluminum nitride-carbon nanotube composite (AlN-CNT), wherein the proportion of Cu@Gr is 80-85 wt%, the proportion of AlN-CNT is 15-20 wt%, the thermal conductivity is >400 W / (m·K), and the bottom layer is used for leading out winding heat;

[0055] A transition layer 3 (30-40 μm) composed of calcium fluoride nanowires (CaF2 NWs), ZIF-8 encapsulated perfluoropolyether (PFPE@ZIF-8) and tungsten disulfide nanosheet (WS2), wherein the proportion of CaF2 NWs is 20-45 wt%, the proportion of PFPE@ZIF-8 is 40-45 wt%, and the proportion of WS2 is 15-20 wt%, the vertical orientation of CaF2 whiskers is realized through an electrostatic field, and the transition layer is used for solid lubrication and PFPE heat-triggered slow release;

[0056] A surface layer 4 (5-10 μm) composed of tungsten disulfide nanosheet (WS2) and microencapsulated ionic liquid containing Fe3O4 magnetic core, wherein the proportion of WS2 is 70-75 wt%, the proportion of microencapsulated ionic liquid containing Fe3O4 magnetic core is 25-30 wt%, the surface is provided with a laser-processed micro-pit array (diameter 80±5 μm, depth 20±2 μm, density 15 / mm²) and a spiral flow guide groove (inclination 25°, pitch 200 μm), and the surface layer is used for friction reduction and micro-crack repair.

[0057] The microencapsulated ionic liquid contains a magnetic Fe3O4 core and is positioned to a depth of 1-3 μm from the outer wall of the surface layer through a 0.3 T magnetic field.

[0058] The PFPE@ZIF-8 encapsulant in the transition layer responds to bearing temperature rise (>120℃) to trigger controllable release of PFPE.

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

[0060] The application further discloses a fluorine-containing metal-based lubricating composition, which comprises component A, component B and component C.​

[0061] Specifically:

[0062] Component A includes, by mass percentage:

[0063] Copper-graphene composite powder 80%~85%;

[0064] Aluminum nitride-carbon nanotube 15%~20%.

[0065] Component B includes, by mass percentage:

[0066] Calcium fluoride nanowire 20%~45%;

[0067] Tungsten disulfide nanosheet 15%~20%;

[0068] ZIF-8 encapsulated perfluoropolyether 40%~45%;

[0069] Component C includes, by mass percentage:

[0070] Microencapsulated ionic liquid containing Fe3O4 magnetic core 25%~30%;

[0071] Tungsten disulfide nanosheet 70%~75%.

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

[0073] In this embodiment, calcium fluoride nanowires (CaF2 NWs) are selected from Zhejiang Yannanomaterials, model YNM-CF50, diameter 60±20nm, length 8-30μm; tungsten disulfide nanosheets are selected from Hexagonal Nanotechnology, model HN-WS2-100, flake diameter 100±20nm, layer number 2-4. Calcium fluoride nanowires serve as high-temperature lubrication cores, and the nanowires form a self-lubricating network (stable at 600℃), releasing Ca 2+ F2 to repair the wear surface, and the tungsten disulfide nanosheet serves as a friction-reducing enhancer, with a layered structure for shear slipping (friction coefficient reduced to 0.08), and cooperates with CaF2 to form a transfer film.

[0074] In this embodiment, ZIF-8 encapsulated perfluoropolyether (PFPE@ZIF-8) serves as long-term lubrication protection, and ZIF-8 releases PFPE in a controlled manner, avoiding sudden migration.

[0075] Wherein, the preparation steps of ZIF-8 encapsulating perfluoropolyether are as follows:

[0076] ZIF-8 powder is pre-impregnated with acetone for 1-2h, and the volume expansion is controlled to be not less than 20%, and then vacuum dehydration is performed at 150℃ for 2h; perfluoropolyether (PFPE) is preheated to 60℃ to reduce viscosity; ZIF-8:PFPE=1:1.2-1.3 (wt) is mixed;

[0077] The vacuum reactor is injected, and the program control is as follows: vacuum to 0.1Pa (30min), temperature rise to 80℃ (PFPE viscosity from 280cP to 40cP), gradient pressure: from 0.1MPa to 5MPa stepwise (1MPa per 30min), pressure to 5MPa for 4h;

[0078] Fast cooling to-20℃, freezing the encapsulation structure, and obtaining PFPE@ZIF-8 structure.

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

[0080] It can be understood that PFPE@ZIF-8 at low temperature, ZIF-8 channel contraction locks PFPE, high temperature friction, thermal induced channel expansion, on-demand release PFPE for lubrication, after wear: calcium fluoride / tungsten disulfide relay lubrication, providing double lubrication protection.

[0081] In this embodiment, the microencapsulated ionic liquid containing Fe3O4 magnetic core is used as a self-repairing agent, and the capsule is broken to release the ionic liquid to fill the micro-pit (repair response time <10s), which is used for emergency repair of wear.

[0082] Wherein, the wall material of the microencapsulated ionic liquid 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-trifluoromethanesulfonimide, and 1-hydroxyethyl-3-methylimidazolium tetrafluoroborate; the Fe3O4 magnetic core content is 5-10wt%, which is pre-emulsified and dispersed in the oil phase, and then microcapsules are formed by interfacial polymerization.

[0083] Further, the particle size distribution of the microencapsulated ionic liquid containing Fe3O4 magnetic core is 2-5μm, the wall thickness uniformity CV value is <8%, the ionic liquid encapsulation rate is ≥92%, and the thermal stability is >200℃.

[0084] It can be understood that the microencapsulated ionic liquid containing Fe3O4 magnetic core is enriched in the depth interval of 1-3 microns from the surface of the coating by a 0.3T magnetic field, when microcracks are generated by the friction of the coating, stress concentration causes the capsule to break, ionic liquid exudes, ionic liquid capillary penetration carries out physical filling, at the same time, the active groups of the ionic liquid and the metal form chemical bonds and form metal complexes, and chemical repair is carried out, at the same time, the ionic liquid-solid composite film formed by CaF2 / WS2 cooperates with lubrication.

[0085] Specifically, 1-butyl-3-methylimidazolium hexafluorophosphate forms Fe-N coordination bonds with exposed iron atoms through the N atom of the imidazole ring, and PF6 - hydrolyzes to PO4 3- to generate an iron phosphate film to inhibit electrochemical corrosion; 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide salt imidazole ring adsorbs on the surface of the new metal to form a double electric layer barrier, and SO2-N - -SO2CF3 releases F - forms FeF2 ceramic film with Fe; and 1-hydroxyethyl-3-methylimidazolium tetrafluoroborate salt hydroxyethyl (-CH2CH2OH) repairs the interface molecular bridge by hydrogen bonding with the coating polymer chain, and BF4 - hydrolyzes to generate B2O3 and F - reacts with the metal to generate Fe2B / FeF2 nanoceramic layer.

[0086] In the embodiment, aluminum nitride-carbon nanotubes (AlN-CNT) are used as an interface strengthening phase, the CNTs are vertically grown to form nanofences, AlN bridges conduct heat, the interface thermal resistance is reduced, the heat conduction is enhanced, and at the same time, as a migration barrier, the fluorine-containing components are prevented from escaping under the action of centrifugal force.

[0087] The application also provides application of a rotor coaxial heat dissipation structure and a fluorine-containing metal-based lubricating composition in a motor rotor shaft in cooperation, which comprises the following steps:

[0088] ①the surface of the rotor shaft is subjected to sand blasting and roughening in sequence, the bonding area is increased, Ra=4.0 microns; laser cleaning is performed, the power is 1.5 kW, the scanning speed is 5 m / s, and the oxide layer is removed; preheating to 300 DEG C for 30 minutes to reduce thermal stress;

[0089] ②an 80-85wt% Cu@Gr and 15-20wt% AlN-CNT mixture is sprayed on the surface of the rotor shaft by high-velocity oxy-fuel spraying (HVOF) at a flame speed of 2400 m / s, an oxygen flow of 900 L / h, and a substrate preheating temperature of 400 DEG C to form a 50-55 micron thick bottom layer;

[0090] ③A transition layer with a thickness of 25-30 pm was formed by atmospheric plasma spraying (APS) with a current of 500 A, a powder feed rate of 35 g / min, and an electrostatic field of 15 kV / cm, and a mixture of 20-45 wt% CaF2 nanowires, 40-45 wt% PFPE@ZIF-8, and 15-20 wt% WS2 was sprayed on the bottom layer;

[0091] ④A surface layer with a thickness of 5-8 pm was formed 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, and a mixture of 70-75 wt% WS2 and 25-30 wt% microencapsulated ionic liquid containing Fe3O4 magnetic cores was sprayed on the transition layer;

[0092] ⑤A micro-pit array (diameter of 80±5 pm, depth of 20±2 pm, and density of 15 / mm 2 ) and a spiral flow guide groove (inclination angle of 25° and pitch of 200 pm) were machined on the surface layer by femtosecond laser (wavelength of 1030 nm and pulse width of 200 fs);

[0093] ⑥The coating density was improved by spark plasma sintering (SPS) at 650°C / 75 MPa / 5 min;

[0094] ⑦A small amount of PFPE grease (Krytox GPL 205) with a thickness of ≤10 pm was pre-coated on the bearing seat during the first assembly of the device for extreme cold start protection.

[0095] In order to further understand the present application, a rotor coaxial heat dissipation structure with a fluorine-containing metal-based lubricating composition provided by the present application is described below in conjunction with examples, and the protection scope of the present application is not limited by the following examples.

[0096] Experimental Example 1

[0097] Preparation of ZIF-8 encapsulated perfluoropolyether:

[0098] ①ZIF-8 powder was pre-soaked in acetone for 1.5 h, and then vacuum dehydrated at 150°C for 2 h; perfluoropolyether (PFPE) of type Krytox GPL 205 was preheated to 60°C to reduce viscosity; and mixed according to ZIF-8:PFPE=1:1.2 (wt);

[0099] ②Vacuum reactor was injected, and the program control was as follows: vacuum to 0.1 Pa (30 min), temperature rise to 80°C, gradient pressure rise: from 0.1 MPa to 5 MPa in steps (1 MPa per 30 min), and pressure rise to 5 MPa for 4 h;

[0100] ③Quickly cooled to -20°C to freeze the encapsulation structure, and PFPE@ZIF-8 structure was obtained.

[0101] Experimental Example 2

[0102] Preparation of microencapsulated ionic liquid containing Fe3O4 magnetic core:

[0103] urea-formaldehyde prepolymer, Fe3O4 magnetic core and 1-butyl-3-methylimidazolium hexafluorophosphate, with a mass ratio of 0.9:0.1:1.3, emulsified and dispersed at a homogeneous speed of 8000 rpm for 15 min, 8 wt% of toluene diisocyanate was added, and the mixture was cured at 60℃ for 4 h at pH 3.5, and then washed and filtered to obtain the microencapsulated ionic liquid containing Fe3O4 magnetic core.

[0104] Experimental Example 3

[0105] Preparation of microencapsulated ionic liquid containing Fe3O4 magnetic core:

[0106] melamine prepolymer, Fe3O4 magnetic core and 1-ethyl-3-methylimidazolium bistrifluoromethanesulfonimide, with a mass ratio of 1:0.15:1.4, emulsified and dispersed at a homogeneous speed of 8000 rpm for 15 min, 8 wt% of toluene diisocyanate was added, and the mixture was cured at 60℃ for 4 h at pH 3.5, and then washed and filtered to obtain the microencapsulated ionic liquid containing Fe3O4 magnetic core.

[0107] Experimental Example 4

[0108] urea-formaldehyde prepolymer, Fe3O4 magnetic core and 1-hydroxyethyl-3-methylimidazolium tetrafluoroborate, with a mass ratio of 1:0.13:1.5, emulsified and dispersed at a homogeneous speed of 8000 rpm for 15 min, 8 wt% of toluene diisocyanate was added, and the mixture was cured at 60℃ for 4 h at pH 3.5, and then washed and filtered to obtain the microencapsulated ionic liquid containing Fe3O4 magnetic core.

[0109] Experimental Example 5

[0110] urea-formaldehyde prepolymer and 1-hydroxyethyl-3-methylimidazolium tetrafluoroborate, with a mass ratio of 1:1.5, emulsified and dispersed at a homogeneous speed of 8000 rpm for 15 min, 8 wt% of toluene diisocyanate was added, and the mixture was cured at 60℃ for 4 h at pH 3.5, and then washed and filtered to obtain the microencapsulated ionic liquid.

[0111] Application Example 1

[0112] ①The surface of the rotor shaft was sandblasted and roughened in sequence, the bonding area was increased, Ra=4.0 μm; laser cleaning, power 1.5 kW, scanning speed 5 m / s, oxidation layer was removed; preheated to 300℃, constant temperature for 30 min, thermal stress was reduced;

[0113] ②A bottom layer with a thickness of 50 μm was formed on the surface of the rotor shaft by high-velocity oxy-fuel spraying (HVOF) at a flame speed of 2400 m / s, an oxygen flow rate of 900 L / h, substrate preheating at 400 °C, and spraying of a mixture of 80 wt% Cu@Gr and 20 wt% AlN-CNT;

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

[0115] ④A surface layer with a thickness of 6 μm was formed on the transition layer by low-temperature cold spraying at a N2 pressure of 4 MPa, a carrier gas of 150 °C, and a magnetic field positioning of 0.3 T, and spraying of a mixture of 75 wt% WS2 and 25 wt% microencapsulated ionic liquid containing Fe3O4 magnetic cores prepared in Experimental Example 2;

[0116] ⑤Micro-pit arrays (diameter 80±5 μm, depth 20±2 μm, density 15 / mm 2 ) and spiral flow guide grooves (inclination angle 25°, pitch 200 μm) were machined on the surface layer by femtosecond laser (wavelength 1030 nm, pulse width 200 fs);

[0117] ⑥The coating was densified by spark plasma sintering (SPS) at 650 °C / 75 MPa / 5 min;

[0118] ⑦A small amount of PFPE lubricating grease (Krytox GPL 205) with a thickness of 8 μm was pre-coated on the bearing seat when the device was first assembled for extreme cold start protection.

[0119] Application Example 2

[0120] ①The surface of the rotor shaft was sandblasted and roughened in sequence to increase the bonding area, Ra=4.0 μm; laser cleaned at a power of 1.5 kW and a scanning speed of 5 m / s to remove the oxide layer; preheated to 300 °C for 30 min to reduce thermal stress;

[0121] ②A bottom layer with a thickness of 53 μm was formed on the surface of the rotor shaft by high-velocity oxy-fuel spraying (HVOF) at a flame speed of 2400 m / s, an oxygen flow rate of 900 L / h, substrate preheating at 400 °C, and spraying of a mixture of 85 wt% Cu@Gr and 15 wt% AlN-CNT;

[0122] ③A transitional layer with a thickness of 30 μm was formed by atmospheric plasma spraying (APS) with a current of 500 A, a powder feed rate of 35 g / min, and an electrostatic field of 15 kV / cm, in which a mixture of 35 wt% CaF2 nanowires, 45 wt% PFPE@ZIF-8 prepared in Experimental Example 1, and 20 wt% WS2 was sprayed on the bottom layer;

[0123] ④A surface layer with a thickness of 6 μm was formed by low-temperature cold spraying with a N2 pressure of 4 MPa, a carrier gas of 150 ℃, and a magnetic field positioning of 0.3 T, in which a mixture of 73 wt% WS2 and 27 wt% microencapsulated ionic liquid containing Fe3O4 magnetic cores prepared in Experimental Example 4 was sprayed on the transitional layer;

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

[0125] Application Example 3

[0126] ①The surface of the rotor shaft was successively sandblasted to roughen and increase the bonding area (Ra = 4.0 μm), laser cleaned at a power of 1.5 kW and a scanning speed of 5 m / s to remove the oxide layer, and preheated to 300 ℃ for 30 min to reduce thermal stress;

[0127] ②A bottom layer with a thickness of 55 μm was formed on the surface of the rotor shaft by high-velocity oxy-fuel spraying (HVOF) at a flame speed of 2400 m / s, an oxygen flow of 900 L / h, and a substrate preheating temperature of 400 ℃, in which a mixture of 83 wt% Cu@Gr and 17 wt% AlN-CNT was sprayed;

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

[0129] ④A surface layer with a thickness of 6 μm was formed by low-temperature cold spraying with a N2 pressure of 4 MPa, a carrier gas of 150 ℃, and a magnetic field positioning of 0.3 T, in which a mixture of 73 wt% WS2 and 27 wt% microencapsulated ionic liquid containing Fe3O4 magnetic cores prepared in Experimental Example 4 was sprayed on the transitional layer;

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

[0131] Comparative Example 1

[0132] A rotor shaft of commercial plasma sprayed (APS) Al2O3-40%TiO2 was selected from Wafangdian Bearings, and the model was ZWZAluCoat™.

[0133] Comparative Example 2

[0134] ①The surface of the rotor shaft is sequentially sandblasted to increase the bonding area, Ra = 4.0 μm; laser cleaned, power 1.5 kW, scanning speed 5 m / s, to remove the oxide layer; preheated to 300 °C, constant temperature for 30 min, to reduce thermal stress;

[0135] ②A 55 μm thick bottom layer is formed on the surface of the rotor shaft by high-velocity oxy-fuel spraying (HVOF) at a flame speed of 2400 m / s, oxygen flow rate of 900 L / h, and substrate preheating at 400 °C, spraying a Cu@Gr mixture;

[0136] A 30 μm thick transition layer is formed on the bottom layer by atmospheric plasma spraying (APS) at a current of 500 A, powder feed rate of 35 g / min, and electrostatic field of 15 kV / cm, spraying a mixture of 35 wt% CaF2 nanowires, 45 wt% PFPE@ZIF-8 prepared in Experimental Example 1, and 20 wt% WS2;

[0137] A 6 μm thick surface layer is formed on the transition layer by low-temperature cold spraying at N2 pressure of 4 MPa, carrier gas of 150 °C, and magnetic field positioning of 0.3 T, spraying a mixture of 73 wt% WS2 and 27 wt% microencapsulated ionic liquid containing Fe3O4 magnetic cores prepared in Experimental Example 4;

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

[0139] Comparative Example 3

[0140] ①The surface of the rotor shaft is sequentially sandblasted to increase the bonding area, Ra = 4.0 μm; laser cleaned, power 1.5 kW, scanning speed 5 m / s, to remove the oxide layer; preheated to 300 °C, constant temperature for 30 min, to reduce thermal stress;

[0141] ②A 55 μm thick bottom layer is formed on the surface of the rotor shaft by high-velocity oxy-fuel spraying (HVOF) at a flame speed of 2400 m / s, oxygen flow rate of 900 L / h, and substrate preheating at 400 °C, spraying a mixture of 83 wt% Cu@Gr and 17 wt% AlN-CNT;

[0142] A 30 μm thick transition layer is formed on the bottom layer by atmospheric plasma spraying (APS) at a current of 500 A, powder feed rate of 35 g / min, and electrostatic field of 15 kV / cm, spraying a mixture of 35 wt% CaF2 nanowires, 45 wt% Krytox GPL 205 perfluoropolyether (PFPE), and 20 wt% WS2;

[0143] A 6 μm thick surface layer is formed on the transition layer by low-temperature cold spraying at N2 pressure of 4 MPa, carrier gas of 150 °C, and magnetic field positioning of 0.3 T, spraying a mixture of 73 wt% WS2 and 27 wt% microencapsulated ionic liquid containing Fe3O4 magnetic cores prepared in Experimental Example 4;

[0144] Steps ③④⑤⑥⑦ are the same as in Application Example 3.

[0145] Comparative Example 4

[0146] ① The surface of the rotor shaft was roughened by sand blasting, increasing the bonding area, Ra = 4.0 μm; laser cleaning, power 1.5 kW, scanning speed 5 m / s, removing the oxide layer; preheated to 300 °C, constant temperature for 30 min, reducing thermal stress;

[0147] ② A 55 μm thick bottom layer was formed on the surface of the rotor shaft by high-velocity oxy-fuel spraying (HVOF) at a flame speed of 2400 m / s, oxygen flow rate of 900 L / h, substrate preheating at 400 °C, spraying a mixture of 83 wt% Cu@Gr and 17 wt% AlN-CNT;

[0148] A 30 μm thick transition layer was formed on the bottom layer by atmospheric plasma spraying (APS) at a current of 500 A, powder feed rate of 35 g / min, and electrostatic field of 15 kV / cm, spraying a mixture of 35 wt% CaF2 nanowires, 45 wt% PFPE@ZIF-8 prepared in Experimental Example 1, and 20 wt% WS2;

[0149] A 6 μm thick surface layer was formed on the transition layer by low-temperature cold spraying at a N2 pressure of 4 MPa, carrier gas temperature of 150 °C, and magnetic field positioning of 0.3 T, spraying a mixture of 73 wt% WS2 and 27 wt% microencapsulated ionic liquid prepared in Experimental Example 5;

[0150] Steps ③④⑤⑥⑦ are the same as in Application Example 3.

[0151] Comparative Example 5

[0152] Steps ①②③④ are the same as in Application Example 3;

[0153] ⑤ The coating density was improved by spark plasma sintering (SPS) at 650 °C / 75 MPa / 5 min;

[0154] ⑥ A small amount of PFPE grease (Krytox GPL 205) was pre-coated on the bearing seat when the device was first assembled, with a thickness of 8 μm, for extreme cold start protection.

[0155] Test Example:

[0156] The coating adhesion strength of the rotor shafts with heat dissipation structures prepared in Application Examples 1-3 and Comparative Examples 1-5 was tested according to the test standard ASTM C633, and the test results are recorded in Table 1.

[0157] The rotor shafts with heat dissipation structure prepared in application examples 1-3 and the rotor shaft coating of comparative examples 1-5 were tested for thermal conductivity according to the test standard LFA 467, and the test results were recorded in Table 1.

[0158] The rotor shafts with heat dissipation structure prepared in application examples 1-3 and the rotor shaft coating of comparative examples 1-5 were tested for friction coefficient according to the test standard ASTM D2714, and the test results were recorded in Table 1.

[0159] The rotor shafts with heat dissipation structure prepared in application examples 1-3 and the rotor shaft coating of comparative examples 1-5 were tested for repair performance by artificial scratching (SEM observation), and the test results were recorded in Table 1.

[0160] Table 1: Performance test statistics table of experimental examples and comparative examples

[0161]

[0162] The rotor shafts with heat dissipation structure prepared in application examples 1-3 and the rotor shaft coating of comparative examples 1-5 were tested for bearing temperature rise according to the test standard IEC 60034-29, and the test results were recorded in Table 2.

[0163] The rotor shafts with heat dissipation structure prepared in application examples 1-3 and the rotor shaft coating of comparative examples 1-5 were tested for accelerated life according to the test standard ISO 281, and the test results were recorded in Table 2.

[0164] Table 2: Industrial test data statistics table of experimental examples and comparative examples

[0165]

[0166] In summary: the present application provides a rotor coaxial heat dissipation structure, which applies a multi-level gradient functional coating structure to the surface of a high-speed motor rotor shaft to realize the synergistic optimization of heat management, friction reduction and wear resistance, and self-repairing function: the functional gradient coating architecture includes a bottom layer, which is constructed by copper@graphene composite powder and aluminum nitride-carbon nanotube composite to efficiently export winding heat; a transition layer, which is composed of electrostatically oriented calcium fluoride nanowires, ZIF-8 encapsulated perfluoropolyether, and tungsten disulfide nanosheets to improve solid lubrication performance and realize controlled release of perfluoropolyether above 150℃ working conditions; a surface layer, which is an intelligent functional layer composed of tungsten disulfide nanosheets and microencapsulated ionic liquids containing Fe3O4 magnetic cores, which are precisely positioned in the 10-30μm area below the surface layer under the drive of a 0.3T magnetic field, realizing targeted repair of microcracks;

[0167] Surface microstructure design: femtosecond laser processing micro-pit array as lubricant storage unit, cooperate with 25° angle spiral guide groove (pitch 200 μm) to enhance the turbulent intensity of cooling medium, significantly improve the convective heat dissipation efficiency.

[0168] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above-mentioned embodiments, and the above-mentioned embodiments and descriptions in the specification are only preferred examples of the present application and are not intended to limit the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application 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 heat-triggered 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 fluorine-containing metal-based lubricating composition characterized in that, Comprising: Component A, Component B, and Component C; Specifically: Component A, by mass percentage, comprises: Copper@graphene composite powder 80%~85%; Aluminum nitride-carbon nanotube 15%~20%. Component B, by mass percentage, comprises: Calcium fluoride nanowires 20%~45%; Tungsten disulfide nanosheets 15%~20%; ZIF-8 encapsulated perfluoropolyether 40%~45%; Component C, by mass percentage, comprises: Microencapsulated ionic liquids containing Fe3O4 magnetic cores 25%~30%; Tungsten disulfide nanosheets 70%~75%.

4. The fluoro metal-based lubricating composition according to claim 3, wherein, The preparation steps of the ZIF-8 encapsulated perfluoropolyether are as follows: ZIF-8 powder is pre-soaked in acetone for 1-2 h, with a volume expansion of not less than 20%, followed by vacuum dehydration at 150℃ for 2 h; perfluoropolyether PFPE is preheated to 60℃ to reduce viscosity; mix according to ZIF-8:PFPE=1:1.2-1.3(wt); Inject into a vacuum reactor, program control: 30 min vacuum to 0.1 Pa, temperature rise to 80℃, gradient pressure: from 0.1 MPa to 5 MPa stepwise pressure rise, pressure rise rate 1 MPa / 30 min, pressure to 5 MPa for 4 h; Quickly cool to -20℃, freeze the encapsulated structure, get PFPE@ZIF-8 structure.

5. The fluoro metal-based lubricating composition according to claim 4, wherein, The kinematic viscosity of the perfluoropolyether is 80-500 cSt.

6. The fluoro metal-based lubricating composition according to claim 3, wherein, The microencapsulated ionic liquids containing Fe3O4 magnetic cores have 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℃.

7. The fluoro metal-based lubricating composition according to claim 6, wherein, The microencapsulated ionic liquids containing Fe3O4 magnetic cores have 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℃. The wall material of the microencapsulated ionic liquids containing Fe3O4 magnetic cores is polyurea formaldehyde or melamine, and the Fe3O4 magnetic core content is 5-10 wt%, which is coated in the wall material by interfacial polymerization.

8. The fluoro metal-based lubricating composition according to claim 6, wherein, The ionic liquid is specifically any one of 1-butyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium bis-trifluoromethanesulfonimide, 1-hydroxyethyl-3-methylimidazolium tetrafluoroborate.

9. The use of a rotor coaxial heat sink structure in conjunction with a fluorometal-based lubricating composition in a motor rotor shaft, characterized in that, The method comprises the following steps: ①The surface of the rotor shaft is sequentially subjected to sand blasting roughening, laser cleaning, preheating to 300°C, and constant temperature for 30 min; ②An 80-85wt% copper@graphene composite powder and a 15-20wt% aluminum nitride-carbon nanotube mixture are sprayed by supersonic flame spraying to form a 50-55μm-thick bottom layer on the surface of the rotor shaft; ③A 20-45wt% calcium fluoride nanowire, 40-45wt% PFPE@ZIF-8 and 15-20wt% tungsten disulfide nanosheet mixture is sprayed by atmospheric plasma spraying on the bottom layer to form a 25-30μm-thick transition layer; ④A 70-75wt% tungsten disulfide nanosheet and 25-30wt% microencapsulated ionic liquid containing Fe3O4 magnetic core mixture is sprayed by low-temperature cold spraying under a N2 pressure of 4MPa, a carrier gas of 150°C and a magnetic field positioning of 0.3T on the transition layer to form a 5-8μm-thick surface layer; (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 trace amount of PFPE lubricating grease is pre-coated on the bearing seat, with a thickness of ≤10μm.

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