Fe3o4 / mxene / PAI composite coating material and preparation method and application thereof

Abstract

The application provides a Fe3O4 / MXene / PAI composite coating material and a preparation method and application thereof, and belongs to the technical field of material surface engineering. Fe3O4 is dispersed and modified first, then is mixed with PAI resin to form a slurry, and is sprayed on the surface of a metal substrate modified by a silane coupling agent; a static magnetic field is applied to induce the directional arrangement of Fe3O4 along the thickness direction of the coating, and then heat curing is performed to obtain a composite coating material. The application utilizes the magnetism of Fe3O4 and the two-dimensional self-lubricating property of MXene, realizes the ordered distribution of the reinforcing phase and the 'point-surface' synergistic reinforcement through magnetic field induction, significantly improves the wear resistance and friction reduction performance of the coating, and simultaneously enhances the interface bonding force through silane coupling agent modification, so that the process is simple and controllable and is suitable for complex-shaped workpieces such as gears.

Description

Technical Field

[0001] This invention relates to the field of materials surface engineering technology, and in particular to a Fe3O4 / MXene / PAI composite coating material, its preparation method and application. Background Technology

[0002] Gears, as core components of high-end equipment's mechanical transmission systems, possess characteristics such as high speed, high torque, and low noise, playing a crucial role in numerous fields including aerospace, rail transportation, and new energy vehicles. However, under extreme operating conditions, traditional steel gears, due to their inherent rigid meshing properties, frequently experience pitting and wear on their tooth surfaces. Furthermore, vibration and noise problems caused by limited tooth surface precision and improper gear shaping are difficult to fundamentally resolve. New-generation gear processing technologies, represented by internal meshing high-strength honing, are still monopolized by foreign companies, and the precision honing process for ultra-high-precision gears is extremely costly, necessitating the exploration of new technological pathways.

[0003] High-performance polyamide-imide (PAI) polymers possess high strength, high modulus, strong heat resistance (long-term operating temperature up to 260℃), chemical stability, and wear resistance, maintaining stable physical and chemical properties even in extreme environments. The construction of high-performance polymer composite coatings on gear surfaces will endow metal gears with self-adaptive properties, vibration reduction, noise reduction, wear resistance, and corrosion resistance, potentially fundamentally overcoming the technical bottleneck of performance limitations imposed by gear surface machining precision and high-performance industrial mother machines. However, ① traditional gearboxes mostly use lubricating oil or grease for external lubrication, but under harsh conditions such as high load, high temperature, high speed, and frequent start-stop cycles, lubricants are prone to oxidation, loss, or failure, leading to direct contact between gear surfaces and causing severe wear, pitting, or even scuffing failure. ③ Although PAI coatings possess self-lubricating properties, their transfer film formation ability is limited, making it difficult to maintain stable lubrication performance in a continuous oil-free environment; therefore, reinforcing phase particles need to be added for blending modification. ④ PAI materials have high viscosity in NMP solution, resulting in poor penetration when sprayed with air, easily leading to uneven bonding with the substrate. ⑤ Conventional particles (such as graphene and molybdenum disulfide) have a severe lack of active sites on their surfaces, resulting in poor interfacial bonding with PAI. Therefore, it is urgent to develop new technologies to solve these problems. Summary of the Invention

[0004] The purpose of this invention is to provide a Fe3O4 / MXene / PAI composite coating material, its preparation method and application, which has high wear resistance and low friction properties and can be used for surface protection of gears.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a Fe3O4 / MXene / PAI composite coating material, comprising the following steps: Fe3O4, epoxy silane coupling agent and organic solvent are mixed and subjected to first modification to obtain modified Fe3O4 dispersion; The modified Fe3O4 dispersion was mixed with MXene for a second modification to obtain a reinforced phase dispersion. The reinforcing phase dispersion was mixed with polyamide-imide resin and additives to obtain a composite coating slurry; A modified metal matrix was obtained by surface treatment of the metal matrix using an aminosilane coupling agent. The composite coating slurry is applied to the surface of a modified metal substrate, and the resulting coated metal substrate is placed in a static magnetic field for magnetic field-induced assembly to form a directional coating on the surface of the metal substrate. The directional coating is thermosetting to obtain a Fe3O4 / MXene / PAI composite coating material.

[0006] Preferably, the epoxy silane coupling agent comprises at least one selected from γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; the mass of the Fe3O4 is 2-10% of the mass of the polyamide-imide resin; the mass fraction of the epoxy silane coupling agent in the organic solvent is 0.5-5%; and the mass of the MXene is 1-5% of the mass of the polyamide-imide resin.

[0007] Preferably, the temperature for the first modification and the second modification are independently room temperature, and the time is independently ≥30 min.

[0008] Preferably, the mass of the organic solvent is 7 to 8 times the mass of the polyamide-imide resin; the mass fraction of the additive in the organic solvent is 0.1 to 2%. The additives include defoamers, leveling agents, and dispersants, wherein the mass ratio of the defoamers, leveling agents, and dispersants is (0~1):(0~1):(0~5) and they are not all 0 at the same time; Preferably, the aminosilane coupling agent includes at least one of γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and γ-aminopropylmethyldiethoxysilane; the surface treatment temperature is 75~85°C and the time is 15~30 min, or the temperature is room temperature and the time is 15~30 min.

[0009] Preferably, the coating thickness of the composite coating slurry on the modified metal substrate surface is 40~80 μm; the coating method is spraying.

[0010] Preferably, the magnetic field lines of the static magnetic field are perpendicular to the coating preparation surface; the time for which the coated metal substrate is placed in the static magnetic field is 1~5 minutes.

[0011] Preferably, the thermosetting temperature is 200~300℃ and the time is 1~3h.

[0012] The present invention provides a Fe3O4 / MXene / PAI composite coating material prepared by the preparation method described above.

[0013] This invention provides the application of the Fe3O4 / MXene / PAI composite coating material described in the above technical solution in gear surface protection.

[0014] This invention provides a method for preparing Fe3O4 / MXene / PAI composite coating material. Based on magnetic field-induced Fe3O4 directional alignment and MXene synergistic reinforcement of polyamide-imide (PAI) composite coating material, the method uses a static magnetic field to induce Fe3O4 directional alignment and reinforce the coating. Combined with the two-dimensional self-lubricating properties of MXene, the method achieves ordered distribution and synergistic reinforcement of the reinforcing phase, significantly improving the wear resistance, friction reduction and interfacial bonding strength of the coating.

[0015] This invention first modifies Fe3O4 with MXene through dispersion, then mixes it with PAI resin to form a slurry, which is sprayed onto the surface of a metal substrate modified with a silane coupling agent. A static magnetic field is applied to induce Fe3O4 to align along the coating thickness direction, followed by thermosetting to obtain a composite coating material. This invention utilizes the magnetic properties of Fe3O4 and the two-dimensional self-lubricating properties of MXene to achieve ordered distribution of the reinforcing phase and "point-to-surface" synergistic reinforcement through magnetic field induction, significantly improving the wear resistance and friction reduction performance of the coating. Simultaneously, the silane coupling agent modification enhances the interfacial bonding force. The process is simple and controllable, suitable for complex-shaped workpieces such as gears.

[0016] This invention utilizes the fact that MXene is rich in -OH and -O active functional groups on its surface, and that after etching, it forms a large number of unsaturated Ti atoms and structural defects, which significantly enhances its reactivity. This allows MXene to form strong interactions with the polar groups of PAI, such as covalent bonds and hydrogen bonds, thereby improving the interfacial bonding.

[0017] This invention introduces iron(III) oxide (Fe3O4) into the PAI composite system, which enables tight coating of the transfer film on the paired surface, potentially extending the service life of the transfer film. After the Fe3O4 / PAI composite coating is sprayed onto a metal substrate, the Fe3O4 particles are oriented and aligned by placing the sample in a static magnetic field, resulting in a strong outer and tough inner structure after curing.

[0018] This invention utilizes the synergistic enhancement effect of Fe3O4 and MXene, and for the first time applies the "point-to-surface" synergistic enhancement mechanism of Fe3O4 and MXene to PAI composite coatings. The distribution of the reinforcing phase is controllable and the interfacial bonding is strong, which can obtain PAI composite coating materials with high wear resistance, low friction performance and long service life. Furthermore, an industrial preparation method suitable for complex-shaped workpieces such as gears has been established, which has important engineering application value.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1. Magnetic field-induced directional alignment of Fe3O4: Utilizing the magnetic properties of Fe3O4, an external magnetic field is applied before the coating is cured, which strengthens the bonding between the coating and the substrate interface, and the Fe3O4 particles are arranged in an orderly manner along the thickness direction to form a "columnar" reinforcing structure, which significantly improves the wear resistance and load-bearing capacity of the coating. 2. Synergistic reinforcement of Fe3O4 and MXene: As a two-dimensional layered material, MXene has excellent self-lubricating properties and interlayer slip characteristics. It forms a "point-to-surface" synergistic reinforcement effect with Fe3O4, which significantly reduces the coefficient of friction and greatly reduces the wear rate. 3. High interfacial bonding strength: Fe3O4 and MXene are surface modified with silane coupling agents to enhance the interfacial compatibility between the inorganic reinforcing phase and the organic PAI matrix; at the same time, the adhesion between the coating and the metal matrix is ​​improved by silane coupling agent pretreatment of the metal matrix. 4. Good process controllability: The coating + magnetic field induction + curing process is suitable for complex-shaped workpieces such as gears. It has a wide process window and is easy to promote industrialization. Attached Figure Description

[0020] Figure 1 This is a schematic diagram illustrating the mechanism of magnetic field-driven movement of iron oxide particles. Figure 2 This diagram illustrates the friction-reducing mechanism of MXene particles during gear meshing. Figure 3 The images show the gears before and after sandblasting, and the gears after being coated with the Fe3O4 / MXene / PAI coating described in Example 1. Figure 4 The results of the cross-cut test at the interface between the PAI coating in Comparative Example 3 and the Fe3O4 / MXene / PAI coating in Example 1 are shown, where a is the PAI coating in Comparative Example 3 and b is the Fe3O4 / MXene / PAI coating in Example 1. Figure 5 The friction coefficient curves are shown for the coatings in Example 1 and Comparative Examples 1-3; Figure 6 The images shown are SEM images of the scratches of the coatings in Example 1 and Comparative Examples 1-3, where a is Comparative Example 3, b is Comparative Example 2, c is Comparative Example 1, and d is Example 1. Figure 7 This is a SEM image of the Fe3O4 / MXene / PAI coating surface under magnetic field applied in Example 1. Detailed Implementation

[0021] In this invention, unless otherwise specified, the raw materials or reagents required for preparation are all commercially available products well known to those skilled in the art.

[0022] This invention provides a method for preparing a Fe3O4 / MXene / PAI composite coating material, comprising the following steps: Fe3O4, epoxy silane coupling agent and organic solvent are mixed and subjected to first modification to obtain modified Fe3O4 dispersion; The modified Fe3O4 dispersion was mixed with MXene for a second modification to obtain a reinforced phase dispersion. The reinforcing phase dispersion was mixed with polyamide-imide resin and additives to obtain a composite coating slurry; A modified metal matrix was obtained by surface treatment of the metal matrix using an aminosilane coupling agent. The composite coating slurry is applied to the surface of a modified metal substrate, and the resulting coated metal substrate is placed in a static magnetic field for magnetic field-induced assembly to form a directional coating on the surface of the metal substrate. The directional coating is thermosetting to obtain a Fe3O4 / MXene / PAI composite coating material.

[0023] In this invention, before using Fe3O4, it is preferable to place Fe3O4 powder in an oven and dry it at 80~120℃ (more preferably 100℃) for 2~4h (more preferably 3h) to remove adsorbed moisture.

[0024] In this invention, the epoxy silane coupling agent preferably includes at least one of γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; when the epoxy silane coupling agent is two or more of the above, this invention does not have a special limitation on the ratio of different types of epoxy silane coupling agents, and any ratio is acceptable.

[0025] In this invention, the organic solvent is preferably at least one of N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO); the mass of the organic solvent is preferably 7 to 8 times the mass of the polyamide-imide resin, more preferably 7.5 to 8 times, and even more preferably 7.9 times.

[0026] In this invention, the mass of Fe3O4 is 2-10% of the mass of the polyamide-imide resin, more preferably 3-8%, and even more preferably 5-6.5%; the mass fraction of the epoxy silane coupling agent in the organic solvent is 0.5-5%, more preferably 1-4%, and even more preferably 2-3%; and the mass of MXene is 1-5% of the mass of the polyamide-imide resin, more preferably 1.5-3%.

[0027] In this invention, dried Fe3O4 and an epoxy-based silane coupling agent are added to an organic solvent and mechanically stirred to disperse the Fe3O4 powder and perform a first modification. Subsequently, MXene powder is added and stirring continues to uniformly disperse the MXene powder for a second modification, resulting in a reinforcing phase dispersion. This invention does not impose a specific limit on the stirring rate; stirring can be performed according to procedures well-known in the art to achieve uniform dispersion.

[0028] In this invention, the temperature of the first modification and the second modification are preferably room temperature, and the time is preferably ≥30 min, more preferably 30 min.

[0029] The present invention preferably involves adding polyamide-imide (PAI) resin and additives to the reinforcing phase dispersion, stirring evenly, to obtain a composite coating slurry.

[0030] In this invention, the mass fraction of the additive in the organic solvent is 0.1-2%, more preferably 0.5-1.5%.

[0031] In this invention, the additives preferably include defoamers, leveling agents and dispersants, and the mass ratio of the defoamers, leveling agents and dispersants is preferably (0~1):(0~1):(0~5) and not all of them are 0 at the same time, more preferably 1:1:5.

[0032] In this invention, the defoamer preferably includes BYK-052, EFKA-2020, or BYK-066N; the leveling agent is preferably BYK-358N, BYK-361N, or BYK-391; and the dispersant is preferably Disperbyk-163, BYK-9076, or EFKA-4310. This invention does not impose any specific limitations on the amount of the defoamer, leveling agent, and dispersant added; adjustments can be made according to the actual slurry state using methods well-known in the art.

[0033] The present invention does not have any particular limitation on the type of metal matrix, and gear steel known in the art is acceptable.

[0034] In this invention, before surface treatment of the metal substrate using an aminosilane coupling agent, it is preferable to sequentially perform sandblasting, ethanol cleaning of surface oil stains, and acid pickling on the metal substrate; the sandblasting mesh size for planar blocks and gear-shaped metal substrates is preferably 80-150 mesh, more preferably 100 mesh.

[0035] The preferred pickling method is as follows: for non-corrosion-resistant steel workpieces, use 10-15% dilute hydrochloric acid for 10 minutes, followed by rinsing with pure water and ethanol once each; for corrosion-resistant steel workpieces, use a mixed solution of 20% nitric acid, 5% hydrofluoric acid and the remainder water for 30 minutes, followed by rinsing with pure water and ethanol once each.

[0036] In this invention, the aminosilane coupling agent preferably includes at least one of γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane (KH-550 / A-1100), and γ-aminopropylmethyldiethoxysilane; when the aminosilane coupling agent is two or more of the above, this invention does not have a special limitation on the ratio of different types of aminosilane coupling agents, and any ratio is acceptable.

[0037] In this invention, the aminosilane coupling agent is preferably dissolved in isopropanol, stirred evenly, and the resulting aminosilane solution is sprayed onto the surface of a metal substrate for surface treatment; the concentration of the aminosilane solution is preferably 5 wt.%.

[0038] The present invention does not impose any special limitation on the amount of the aminosilane coupling agent; it can be adjusted according to requirements.

[0039] In this invention, the surface treatment temperature is preferably 75~85℃, more preferably 75~80℃, and the time is preferably 15~30min, more preferably 15~20min, or the temperature is preferably room temperature and the time is preferably 15~30min, more preferably 20~30min.

[0040] In this invention, the coating thickness of the composite coating slurry on the modified metal substrate surface is preferably 40-80 μm, more preferably 50-70 μm, and even more preferably 60 μm; the coating method is preferably spraying, more preferably air spraying. This invention does not impose any special limitations on the spraying parameters; spraying can be performed according to processes well known in the art.

[0041] After the composite coating slurry is applied to the surface of the metal substrate, a static magnetic field is immediately set above the metal substrate for static treatment. Under the induction of the magnetic field, Fe3O4 is oriented along the coating thickness direction into a one-dimensional chain structure and moves to the coating surface to form an oriented structure.

[0042] In this invention, the magnetic field lines of the static magnetic field are perpendicular to the coating preparation surface; the static treatment time of the coating metal substrate in the static magnetic field is preferably 1~5 min, more preferably 3~5 min.

[0043] After magnetic field-induced self-assembly is completed, the present invention preferably places the metal substrate in an oven for thermosetting, and then naturally cools it to room temperature to obtain a composite coating material.

[0044] In this invention, the temperature for heat curing is preferably 200~300℃, more preferably 250℃, and the time is preferably 1~3h, more preferably 2h.

[0045] The present invention provides a Fe3O4 / MXene / PAI composite coating material prepared by the preparation method described above.

[0046] This invention provides the application of the Fe3O4 / MXene / PAI composite coating material described above in gear surface protection. This invention does not specifically limit the method of application; any method well-known in the art can be used.

[0047] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0048] Unless otherwise specified, the experimental methods described in the various embodiments of this invention are conventional methods; unless otherwise specified, the raw materials used are all commercially available products, and the proportions are all by mass percentage.

[0049] Example 1

[0050] Preparation of Fe3O4 / MXene / PAI composite coating: (1) Pretreatment of reinforcing phase powder 130g of polyamide-imide (PAI) resin; 8.4g of Fe3O4; 2g of MXene; 30.9g of epoxy silane coupling agent; 20.6g of additives; Fe3O4 powder was placed in an oven and dried at 100℃ for 3 hours. The dried Fe3O4 powder was weighed and added to γ-glycidoxypropyltrimethoxysilane. The resulting mixture was added to 1000 mL of NMP solvent and mechanically stirred for 30 minutes to obtain a modified Fe3O4 dispersion. Add the required amount of MXene powder to the above modified Fe3O4 dispersion and continue mechanical stirring for 30 min to obtain the reinforced phase dispersion; Weigh the required amounts of PAI resin, defoamer BYK-052, leveling agent BYK-358N, and dispersant Disperbyk-163 (the mass ratio of defoamer, leveling agent, and dispersant is 1:1:5), add them to the above-mentioned reinforcing phase dispersion, and stir evenly to obtain Fe3O4 / MXene / PAI composite coating slurry.

[0051] (2) Pretreatment of the metal matrix

[0052] The No. 45 steel metal substrate was sandblasted with 100 mesh. First, the surface oil of the substrate was cleaned with ethanol, then pickled with 12% dilute hydrochloric acid for 10 minutes, and then cleaned again with pure water and ethanol respectively. 25g of γ-aminopropyltrimethoxysilane was dissolved in 500g of isopropanol to a concentration of 5 wt.%, and after being mechanically stirred evenly, it was sprayed onto the surface of the pickled metal substrate and dried at 75℃ for 15 min to obtain the modified metal substrate.

[0053] (3) Spraying and magnetic field induction

[0054] The Fe3O4 / MXene / PAI composite coating slurry was sprayed onto the surface of the modified metal substrate with air, and the coating thickness was 60 μm. After spraying, the metal substrate was immediately placed in a static magnetic field with the magnetic field lines perpendicular to the coating preparation surface for 5 minutes.

[0055] (4) Curing

[0056] After magnetic field induction, the metal substrate was placed in an oven for thermal curing at a temperature of 250°C for 2 hours. It was then allowed to cool naturally to room temperature to obtain the Fe3O4 / MXene / PAI composite coating material.

[0057] Comparative Example 1

[0058] The only difference from Example 1 is that MXene powder is not added. The Fe3O4 / PAI composite coating material is prepared by following these steps: (1) Pretreatment of reinforcing phase powder 130g of polyamide-imide PAI resin; 8.4g of Fe3O4; 30.9g of silane coupling agent; 20.6g of additives; Fe3O4 powder was placed in an oven and dried at 100℃ for 3 hours. The dried Fe3O4 powder was weighed and added to γ-glycidoxypropyltrimethoxysilane. The resulting mixture was added to 1000 mL of NMP solvent and mechanically stirred for 30 minutes to obtain a modified Fe3O4 dispersion. Weigh the required amounts of PAI resin, defoamer BYK-052, leveling agent BYK-358N, and dispersant Disperbyk-163 (the mass ratio of defoamer, leveling agent, and dispersant is 1:1:5), add them to the above modified Fe3O4 dispersion, and stir evenly to obtain Fe3O4 / PAI composite coating slurry.

[0059] (2) Pretreatment of the metal matrix

[0060] The No. 45 steel metal substrate was sandblasted with 100 mesh. First, the surface oil of the substrate was cleaned with ethanol, then pickled with 12% dilute hydrochloric acid for 10 minutes, and then cleaned again with pure water and ethanol respectively. 25g of γ-aminopropyltrimethoxysilane was dissolved in 500g of isopropanol to a concentration of 5 wt.%, and after being mechanically stirred evenly, it was sprayed onto the surface of the pickled metal substrate and dried at 75℃ for 15 min to obtain the modified metal substrate.

[0061] (3) Spraying and magnetic field induction

[0062] The Fe3O4 / PAI composite coating slurry was sprayed onto the surface of the modified metal substrate with air, and the coating thickness was 60 μm. After spraying, the metal substrate was immediately placed in a static magnetic field with the magnetic field lines perpendicular to the coating preparation surface for 5 minutes.

[0063] (4) Curing

[0064] After magnetic field induction, the metal substrate was placed in an oven for thermal curing at a temperature of 250°C for 2 hours. It was then allowed to cool naturally to room temperature to obtain the Fe3O4 / PAI composite coating material.

[0065] Comparative Example 2

[0066] The only difference from Example 1 is that MXene powder is not added, and the sprayed metal substrate is not placed in a static magnetic field to prepare the Fe3O4 / PAI composite coating material. (1) Pretreatment of reinforcing phase powder 130g of polyamide-imide PAI resin; 8.4g of Fe3O4; 30.9g of epoxy silane coupling agent; 20.6g of additives; Fe3O4 powder was placed in an oven and dried at 100℃ for 3 hours. The dried Fe3O4 powder was weighed and added to γ-glycidoxypropyltrimethoxysilane. The resulting mixture was added to 1000 mL of NMP solvent and mechanically stirred for 30 minutes to obtain a modified Fe3O4 dispersion. Weigh the required amounts of PAI resin, defoamer BYK-052, leveling agent BYK-358N, and dispersant Disperbyk-163 (the mass ratio of defoamer, leveling agent, and dispersant is 1:1:5), add them to the above modified Fe3O4 dispersion, and stir evenly to obtain Fe3O4 / PAI composite coating slurry.

[0067] (2) Pretreatment of the metal matrix

[0068] The No. 45 steel metal substrate was sandblasted with 100 mesh. First, the surface oil of the substrate was cleaned with ethanol, then pickled with 12% dilute hydrochloric acid for 10 minutes, and then cleaned again with pure water and ethanol respectively. 25g of γ-aminopropyltrimethoxysilane was dissolved in 500g of isopropanol to a concentration of 5 wt.%, and after being mechanically stirred evenly, it was sprayed onto the surface of the pickled metal substrate and dried at 75℃ for 15 min to obtain the modified metal substrate.

[0069] (3) Spraying

[0070] The Fe3O4 / PAI composite coating slurry was air-sprayed onto the surface of the modified metal substrate, and the resulting coating thickness was 60 μm.

[0071] (4) Curing

[0072] The sprayed metal substrate was placed in an oven for heat curing at 250°C for 2 hours, and then allowed to cool naturally to room temperature to obtain the Fe3O4 / PAI composite coating material.

[0073] Comparative Example 3

[0074] The only difference from Example 1 is that MXene and Fe3O4 powders are not added, and the sprayed metal substrate is not placed in a magnetic field to prepare the PAI coating material. (1) Pretreatment of resin powder 130g of polyamide-imide and 20.6g of additives (same as in Example 1) were added to 1000mL of NMP solvent and mechanically stirred for 30min to obtain PAI coating slurry.

[0075] (2) Pretreatment of the metal matrix

[0076] The No. 45 steel metal substrate was sandblasted with 100 mesh. First, the surface oil of the substrate was cleaned with ethanol, then pickled with 12% dilute hydrochloric acid for 10 minutes, and then cleaned again with pure water and ethanol respectively. 25g of γ-aminopropyltrimethoxysilane was dissolved in 500g of isopropanol to a concentration of 5 wt.%, and after being mechanically stirred evenly, it was sprayed onto the surface of the pickled metal substrate and dried at 75℃ for 15 min to obtain the modified metal substrate.

[0077] (3) Spraying

[0078] The PAI coating slurry was air-sprayed onto the surface of the modified metal substrate, and the resulting coating thickness was 60 μm.

[0079] (4) Curing

[0080] The sprayed metal substrate is placed in an oven for heat curing at a temperature of 250°C for 2 hours, and then allowed to cool naturally to room temperature to obtain the PAI coating material.

[0081] Characterization and performance testing

[0082] Figure 1 This is a schematic diagram illustrating the mechanism of magnetic field-driven movement of iron(III) oxide particles, as shown below. Figure 1 As shown, Fe3O4 particles are oriented under the influence of a magnetic field.

[0083] Figure 2 The diagram shows the friction reduction mechanism of MXene particles during gear meshing, as follows. Figure 2 As shown, MXene can promote the formation of a two-dimensional transfer film and reduce friction during gear meshing.

[0084] Figure 3 The images show the gears before and after sandblasting, and the gears coated with the Fe3O4 / MXene / PAI coating from Example 1. The smooth, flat surfaces are beneficial for reducing friction during gear meshing.

[0085] Figure 4 The results of the cross-cut test at the interface between the PAI coating in Comparative Example 3 and the Fe3O4 / MXene / PAI coating in Example 1 are shown, where a is the PAI coating in Comparative Example 3 and b is the Fe3O4 / MXene / PAI coating in Example 1; Figure 4 As shown, in Example 1, the coating did not peel off from the metal substrate interface, and the interface bonding was good, indicating that the interface bonding level of the example did not decrease and met the national standard.

[0086] Figure 5 The friction coefficient curves are for the coatings in Example 1 and Comparative Examples 1-3; Figure 5 It can be seen that the friction coefficient of the Fe3O4 / MXene / PAI coating under the applied magnetic field decreases sharply and is more stable than that of comparative examples 1 to 3, and the friction performance is greatly improved.

[0087] Figure 6SEM micrographs of the wear tracks of the coatings in Example 1 and Comparative Examples 1-3, where a is Comparative Example 3, b is Comparative Example 2, c is Comparative Example 1, and d is Example 1; from Figure 6 It can be seen that compared with Comparative Examples 2 and 3, the wear track width of the Fe3O4 / PAI coating with a magnetic field applied in Comparative Example 1 is very small, and the wear amount is significantly reduced; compared with Comparative Examples 1, 2, and 3, the wear track of the Fe3O4 / MXene / PAI coating with a magnetic field applied in Example 1 completely disappears, the wear amount is almost 0, and the wear resistance is the highest.

[0088] Figure 7 SEM micrograph of the surface of the Fe3O4 / MXene / PAI coating with a magnetic field applied in Example 1; from Figure 7 It can be seen that the Fe3O4 particles form a one-dimensional chain structure under the magnetic field.

[0089] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a Fe3O4 / MXene / PAI composite coating material, characterized in that, Includes the following steps: Fe3O4, epoxy silane coupling agent and organic solvent are mixed and subjected to first modification to obtain modified Fe3O4 dispersion; The modified Fe3O4 dispersion was mixed with MXene for a second modification to obtain a reinforced phase dispersion. The reinforcing phase dispersion was mixed with polyamide-imide resin and additives to obtain a composite coating slurry; A modified metal matrix was obtained by surface treatment of the metal matrix using an aminosilane coupling agent. The composite coating slurry is applied to the surface of a modified metal substrate, and the resulting coated metal substrate is placed in a static magnetic field for magnetic field-induced assembly to form a directional coating on the surface of the metal substrate. The directional coating is thermosetting to obtain a Fe3O4 / MXene / PAI composite coating material.

2. The preparation method according to claim 1, characterized in that, The epoxy silane coupling agent includes at least one selected from γ-glycidyl etheroxypropyltrimethoxysilane, γ-glycidyl etheroxypropyltriethoxysilane, γ-glycidyl etheroxypropylmethyldimethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; the mass of the Fe3O4 is 2-10% of the mass of the polyamide-imide resin; the mass fraction of the epoxy silane coupling agent in the organic solvent is 0.5-5%; and the mass of the MXene is 1-5% of the mass of the polyamide-imide resin.

3. The preparation method according to claim 1, characterized in that, The first and second modifications were performed at room temperature and for ≥30 min independently.

4. The preparation method according to claim 1, characterized in that, The mass of the organic solvent is 7 to 8 times the mass of the polyamide-imide resin; the mass fraction of the additive in the organic solvent is 0.1 to 2%. The additives include defoamers, leveling agents, and dispersants, and the mass ratio of the defoamers, leveling agents, and dispersants is (0~1):(0~1):(0~5) and they are not all 0 at the same time.

5. The preparation method according to claim 1, characterized in that, The aminosilane coupling agent includes at least one of γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane and γ-aminopropylmethyldiethoxysilane; The surface treatment is performed at a temperature of 75-85°C for 15-30 minutes, or at room temperature for 15-30 minutes.

6. The preparation method according to claim 1, characterized in that, The composite coating slurry has a coating thickness of 40~80 μm on the surface of the modified metal substrate; the coating method is spraying.

7. The preparation method according to claim 1, characterized in that, The magnetic field lines of the static magnetic field are perpendicular to the coating preparation surface; the coating metal substrate is placed in the static magnetic field for 1 to 5 minutes.

8. The preparation method according to claim 1, characterized in that, The thermosetting temperature is 200~300℃, and the time is 1~3h.

9. The Fe3O4 / MXene / PAI composite coating material prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the Fe3O4 / MXene / PAI composite coating material of claim 9 in gear surface protection.

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