A self-lubricating high wear-resistant coating and its preparation method

Abstract

The present invention discloses a self-lubricating, highly wear-resistant coating and a preparation method thereof, belonging to the technical field of coating protection. The coating composition of the present invention comprises, by mass fraction, 10-15% of a MAX phase, 2-5% of fibers, and the remainder being TiO2, wherein the MAX phase comprises one of Ti2AlC, Ti3SiC2, and Cr2AlC. By optimizing the coating formula and combining the powder and coating treatment method of the present invention, a coating with high wear resistance, good self-lubricating properties, and excellent fracture toughness is prepared, providing long-term protection for polysilicon powder conveying equipment and pipelines, thereby further improving the purity of the polysilicon product and extending the service life of the equipment.

Description

Technical Field

[0001] The invention belongs to the technical field of polysilicon coating protection, and relates to a self-lubricating high-wear-resistant coating and a preparation method thereof. Background Art

[0002] In polysilicon powder conveying equipment and pipelines, metal components wear out after a period of use, leading to their failure. Furthermore, the metal produced by this wear can easily increase the impurity content of the polysilicon product. Currently, surface treatment techniques are commonly used to effectively improve surface wear by applying a coating to the substrate. Atmospheric plasma sprayed titanium oxide ceramic coatings offer advantages such as high strength, hardness, high wear resistance, and stable chemical properties. They are suitable for use as wear-resistant coatings in polysilicon production, significantly extending the lifespan of equipment. However, during the silicon powder scouring process, the frictional heat generated by friction can cause sintering of coating pores and grain growth, leading to increased brittleness and rapid failure of the coating.

[0003] Therefore, it is necessary to provide a self-lubricating high wear-resistant coating and its preparation method to improve the fracture toughness and lubricity of the ceramic coating, reduce the expansion of cracks in the coating during service, and reduce the damage to the coating caused by the synergistic effect of particle erosion and wear. Summary of the Invention

[0004] In order to overcome the problems in the background technology, the present invention improves the high-temperature stability and wear resistance of the coating by completely converting anatase TiO2 into rutile TiO2. By utilizing the capillary force and surface tension at the fiber interface where nano-TiO2 adheres, the thin TiO2 layer is conducive to bridging between the fiber and the plasma sprayed particles, thereby increasing the toughness of the coating. At the same time, through pre-oxidation, a stable metal oxide film (TiO2, Al2O3) is generated on the coating surface, which has a lubricating effect on wear.

[0005] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0006] In one aspect, the present invention provides a method for preparing a self-lubricating high-wear-resistant coating, the preparation method comprising the following steps:

[0007] (1) TiO2 powder, MAX phase, and fiber are wet ball-milled to obtain a composite powder, wherein the composite powder comprises 10-15% by mass of the MAX phase, 2-5% by mass of the fiber, and the balance is TiO2, wherein the MAX phase comprises one of Ti2AlC, Ti3SiC2, and Cr2AlC. The titanium oxide particle size is less than 100 nm, and the fiber aspect ratio is greater than 100.

[0008] (2) Add the composite powder obtained in step (1) to water, add polyvinyl alcohol, a dispersant, and a defoamer to the water, and continue ball milling to obtain a slurry. Deionized water is preferably used.

[0009] (3) Using the slurry obtained in step (2) to spray powder to obtain composite agglomerated powder.

[0010] (4) chemically plating nickel on the composite agglomerated powder obtained in step (3) to obtain nickel-coated powder.

[0011] (5) The nickel-coated powder obtained in step (4) is treated by a plasma spheroidization method to obtain a spraying raw material.

[0012] (6) Using supersonic plasma spraying, the coating material in step (5) is sprayed onto the surface of the component.

[0013] (7) performing isothermal pre-oxidation heat treatment on the coating sprayed in step (6).

[0014] Preferably, in step (1), the fiber comprises one of SiC, C, and Al2O3.

[0015] Preferably, in step (1), the ball-to-material ratio is 3:1, the ball milling speed is 500 r / min, and the ball milling time is 2 h.

[0016] Preferably, in step (2), the dispersant is polyethylene glycol, the defoaming agent is tributyl phosphate, and after the composite powder is added to water, the solid content in the liquid is 40%, the added mass of polyvinyl alcohol is 3% of the total mass of the liquid, the added amount of the dispersant is 0.1% of the total mass of the liquid, the added amount of the defoaming agent is 0.1% of the total mass of the liquid, and the ball milling time is 2 hours.

[0017] Preferably, in step (3), the spray powdering air inlet temperature is 235-255° C., the air outlet temperature is 95-105° C., the pressure in the tower is 0.05 kPa, the peristaltic pump opening is 26%, and the atomizer speed is 25000 RPM.

[0018] Preferably, in step (4), the specific method of chemical nickel plating is: first, adding 3-3.2% of NiSiO4·6H2O by weight of water, 3-3.3% of Na3C6H5O7·6H2O by weight of water, 3.5-3.8% of NaHPO2·H2O by weight of water and 3.5-4% of HBO3 by weight of water to water to prepare a nickel plating solution; then adding HNO3 to the nickel plating solution to adjust the pH of the nickel plating solution to pH=9; thereafter, heating the nickel plating solution to 50-60°C, and adding 10-15% of the total mass of the composite agglomerated powder to the nickel plating solution under stirring, after nickel plating for 30-60 minutes, filtering the nickel plating solution to obtain powder, and then drying the powder to obtain nickel-coated powder.

[0019] Preferably, in the step (5), the powder feeding rate is 15 to 20 g / min, the system pressure is 50 to 82.68 kPa, the power is 30 to 35 kW, the carrier gas is N2, the carrier gas flow rate is 3 L / min, the central gas is a mixed gas of Ar and H2, wherein the volume of H2 accounts for 30% of the total volume of the mixed gas, the mixed gas flow rate is 35 to 45 L / min, and the powder particle size of the coating raw material obtained after plasma spheroidization is 15 to 45 μm.

[0020] Preferably, in the step (6), the supersonic plasma spraying power is 58 kW, the spraying voltage is 130 V, the spraying current is 500 A, the Ar gas flow rate is 220 L / min, the H2 flow rate is 11 L / min, the powder feeding rate is 15 g / min, the spray gun moving speed is 300 mm / s, the spraying angle is 90°, the number of depositions is 5 times, and the spraying distance is 120 mm.

[0021] Preferably, in step (7), the specific process of the isothermal pre-oxidation heat treatment is: heating the coating to 1200-1300° C. in a heat treatment muffle furnace, keeping the temperature for 10-15 hours, and then allowing the coating to cool naturally to room temperature.

[0022] Another aspect of the present invention provides a self-lubricating and highly wear-resistant coating, which is prepared by the above-mentioned preparation method.

[0023] Beneficial effects of the present invention:

[0024] 1. In the fiber-doped coating, anatase TiO2 is completely transformed into rutile TiO2. Rutile TiO2 has better high-temperature stability and wear resistance.

[0025] 2. The fibers form a network skeleton structure in the coating, and capillary force and surface tension occur at the fiber interface where nano-TiO2 adheres. The thin TiO2 layer is conducive to the bridging between the fibers and the plasma sprayed particles, thereby increasing the toughness of the coating.

[0026] 3. The composite powder prepared by nanopowder spray drying has uniform distribution of fiber and MAX phase.

[0027] 4. The Ni-coated powder is treated by plasma spheroidization. The melted softer metal Ni particles can fill the gaps between the particles, improve the sphericity and density of the powder, and ensure the integrity of the powder during spraying.

[0028] 5. The coating is subjected to isothermal pre-oxidation heat treatment to dissolve the grain boundaries of the coating structure, grow rapidly, and rearrange the atoms in the lattice. The original pores will become smaller or filled. On the one hand, the porosity of the coating can be reduced. On the other hand, the stable metal oxide film (TiO2, Al2O3) generated on the surface of the coating plays a lubricating role on wear.

[0029] 6. During the wear process of silicon particles, wear-resistant phases such as Ti3SiC2, SiO2, SiO2-Al2O3, SiC, and TiAl can be generated in situ, further improving the wear resistance of the coating.

[0030] 7. The coating porosity after spraying of the present invention is ≤0.1%, the friction coefficient is ≤0.25, and the hardness is ≥500HV 0.3 , wear rate ≤ 2×10 -17 m 3 / (N·m). BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a microscopic morphology of the coating prepared in Example 1 of the present invention, wherein Figure (b) is a partial enlarged view of Figure (a). DETAILED DESCRIPTION

[0032] The present invention is further described in detail below with reference to specific embodiments, but the protection scope of the present invention is not limited to the contents described above.

[0033] In the examples and comparative examples of the present invention, chemical reagents not otherwise specified were all commercially available analytically pure for the experiments.

[0034] The coating compositions of the embodiments of the present invention and the comparative examples are shown in Table 1.

[0035] Table 1

[0036]

[0037] Example 1

[0038] This example prepared the coating as follows:

[0039] (1) Weigh TiO2 nanoceramic powder with a particle size less than 100 nm, MAX phase, and SiC fiber with an aspect ratio greater than 100 according to the mass fractions shown in Table 1. The total mass of the coating raw materials is determined according to conventional specifications.

[0040] (2) First, TiO2 nanoceramic powder, Max phase, and fibers were placed in a planetary ball mill and wet-milled for 2 h at a ball-to-material ratio of 3:1 and a rotation speed of 500 r / min to obtain a composite powder. The powders were mixed evenly. Wet milling can avoid destroying the layered structure of the MAX phase and the rod-like structure of the fibers compared to dry milling.

[0041] (3) The composite powder was made into a slurry with deionized water. After the composite powder was added to the water, the solid content in the liquid was 40%. Then, polyvinyl alcohol (PVA) at 3% of the total mass of the liquid, a dispersant (PEG) at 0.1% of the total mass of the liquid, and a defoaming agent (tributyl phosphate) at 0.1% of the total mass of the liquid were added to the liquid, and ball milling was continued for 2 h.

[0042] (4) A centrifugal spray dryer was used to spray powder at an air inlet temperature of 245°C, an air outlet temperature of 100°C, a tower pressure of 0.05 kPa, a peristaltic pump opening of 26%, and an atomizer speed of 25000 RPM to obtain a composite agglomerated powder.

[0043] (5) The agglomerated powder is coated with a chemical nickel plating process to obtain a nickel-coated powder. First, deionized water is taken and NiSiO4·6H2O, Na3C6H5O7·6H2O, NaHPO2·H2O, and HBO3 are added to the deionized water, wherein NiSiO4·6H2O is 3.1% by weight of the deionized water, Na3C6H5O7·6H2O is 3.2% by weight of the deionized water, NaHPO2·H2O is 3.6% by weight of the deionized water, and HBO3 is 3.8% by weight of the deionized water to prepare a nickel plating solution; secondly, the pH value of the solution is adjusted with HNO3 to pH=9; then, a magnetic stirrer is adjusted and, at a temperature of 55°C, 12% of the total mass of the composite agglomerated powder is added to the solution and stirred for 45 minutes. Finally, the powder is filtered out with a filter funnel and dried to obtain a nickel-coated powder.

[0044] (6) Densification of the nickel-coated powder was performed using plasma spheroidization. In the control system, the system pressure, central gas flow rate, and power were set, and the system was started to begin powder feeding. The powder feeding rate was 18 g / min, the system pressure was 60 kPa, the power was 32 kW, the carrier gas was N2, the carrier gas flow rate was 3 L / min, and the central gas was Ar + 30 vol.% H2, with a flow rate of 40 L / min. The resulting powder had a particle size of 15 to 45 μm and was used as a spraying material.

[0045] (7) Spray coating. The spraying raw material was sprayed onto the workpiece surface using supersonic plasma spraying technology. During the spraying process, the spraying power was 58 kW, the spraying voltage was 130 V, the spraying current was 500 A, the Ar gas flow rate was 220 L / min, the H2 flow rate was 11 L / min, the powder feeding rate was 15 g / min, the spray gun moving speed was 300 mm / s, the spraying angle was 90°, the number of depositions was 5 times, and the spraying distance was 120 mm.

[0046] (8) Isothermal pre-oxidation heat treatment of the coating: Heat the sprayed coating to 1250°C in a muffle furnace and keep it warm for 13 hours. Then turn off the power of the heating furnace and allow the coating to cool naturally to room temperature.

[0047] The microstructure of the coating prepared in this embodiment is as follows Figure 1 As shown, through Figure 1 It can be seen that the powder and whiskers are tightly combined, the whiskers are evenly distributed in the coating, and the whiskers are wrapped by powder particles. This thin layer is conducive to the bridging of whiskers between plasma sprayed particles, which can effectively transfer and disperse stress and prevent the expansion of cracks, thereby improving the overall strength and toughness of the coating.

[0048] The friction coefficient and fracture toughness of the coating prepared in this example were measured, and the results are shown in Table 2.

[0049] Example 2

[0050] This example prepared the coating as follows:

[0051] (1) Weigh TiO2 nanoceramic powder with a particle size less than 100 nm, MAX phase, and C fibers with an aspect ratio greater than 100 according to the mass fractions in Table 1. The total mass of the coating raw materials is determined according to conventional specifications.

[0052] (2) First, TiO2 nanoceramic powder, Max phase, and fibers were placed in a planetary ball mill and wet-milled for 2 h at a ball-to-material ratio of 3:1 and a rotation speed of 500 r / min to obtain a composite powder. The powders were mixed evenly. Wet milling can avoid destroying the layered structure of the MAX phase and the rod-like structure of the fibers compared to dry milling.

[0053] (3) The composite powder was made into a slurry with deionized water. After the composite powder was added to the water, the solid content in the liquid was 40%. Then, polyvinyl alcohol (PVA) at 3% of the total mass of the liquid, a dispersant (PEG) at 0.1% of the total mass of the liquid, and a defoaming agent (tributyl phosphate) at 0.1% of the total mass of the liquid were added to the liquid, and ball milling was continued for 2 h.

[0054] (4) A centrifugal spray dryer was used to spray powder at an air inlet temperature of 235°C, an air outlet temperature of 95°C, a tower pressure of 0.05 kPa, a peristaltic pump opening of 26%, and an atomizer speed of 25000 RPM to obtain a composite agglomerated powder.

[0055] (5) The agglomerated powder is coated with a chemical nickel plating process to obtain a nickel-coated powder. First, deionized water is taken and NiSiO4·6H2O, Na3C6H5O7·6H2O, NaHPO2·H2O, and HBO3 are added to the deionized water, wherein NiSiO4·6H2O is 3% by weight of the deionized water, Na3C6H5O7·6H2O is 3% by weight of the deionized water, NaHPO2·H2O is 3.5% by weight of the deionized water, and HBO3 is 3.5% by weight of the deionized water to prepare a nickel plating solution; secondly, the pH value of the solution is adjusted with HNO3 to pH=9; then, a magnetic stirrer is adjusted and, at a temperature of 50°C, 15% of the total mass of the composite agglomerated powder is added to the solution and stirred for 60 minutes. Finally, the powder is filtered out with a filter funnel and dried to obtain a nickel-coated powder.

[0056] (6) Densification of the nickel-coated powder was performed using plasma spheroidization. In the control system, the system pressure, central gas flow rate, and power were set, and the system was started to begin powder feeding. The powder feeding rate was 15 g / min, the system pressure was 50 kPa, the power was 30 kW, the carrier gas was N2, the carrier gas flow rate was 3 L / min, and the central gas was Ar + 30 vol.% H2, with a flow rate of 35 L / min. The resulting powder had a particle size of 15 to 45 μm and was used as a spraying material.

[0057] (7) Spray coating. The spraying raw material was sprayed onto the workpiece surface using supersonic plasma spraying technology. During the spraying process, the spraying power was 58 kW, the spraying voltage was 130 V, the spraying current was 500 A, the Ar gas flow rate was 220 L / min, the H2 flow rate was 11 L / min, the powder feeding rate was 15 g / min, the spray gun moving speed was 300 mm / s, the spraying angle was 90°, the number of depositions was 5 times, and the spraying distance was 120 mm.

[0058] (8) Isothermal pre-oxidation heat treatment of the coating: Heat the sprayed coating to 1200°C in an argon atmosphere and keep it warm for 15 hours. Then turn off the power of the heating furnace and allow the coating to cool naturally to room temperature.

[0059] The coating properties prepared in this example are similar to those in Example 1.

[0060] Example 3

[0061] This example prepared the coating as follows:

[0062] (1) Weigh TiO2 nanoceramic powder with a particle size less than 100 nm, MAX phase, and Al2O3 fibers with an aspect ratio greater than 100 according to the mass fractions shown in Table 1. The total mass of the coating raw materials is determined according to conventional specifications.

[0063] (2) First, TiO2 nanoceramic powder, Max phase, and fibers were placed in a planetary ball mill and wet-milled for 2 h at a ball-to-material ratio of 3:1 and a rotation speed of 500 r / min to obtain a composite powder. The powders were mixed evenly. Wet milling can avoid destroying the layered structure of the MAX phase and the rod-like structure of the fibers compared to dry milling.

[0064] (3) The composite powder was made into a slurry with deionized water. After the composite powder was added to the water, the solid content in the liquid was 40%. Then, polyvinyl alcohol (PVA) at 3% of the total mass of the liquid, a dispersant (PEG) at 0.1% of the total mass of the liquid, and a defoaming agent (tributyl phosphate) at 0.1% of the total mass of the liquid were added to the liquid, and ball milling was continued for 2 h.

[0065] (4) A centrifugal spray dryer was used to spray powder at an air inlet temperature of 255°C, an air outlet temperature of 105°C, a tower pressure of 0.05 kPa, a peristaltic pump opening of 26%, and an atomizer speed of 25000 RPM to obtain a composite agglomerated powder.

[0066] (5) The agglomerated powder is coated with a chemical nickel plating process to obtain a nickel-coated powder. First, deionized water is taken and NiSiO4·6H2O, Na3C6H5O7·6H2O, NaHPO2·H2O, and HBO3 are added to the deionized water, wherein NiSiO4·6H2O is 3.2% by weight of the deionized water, Na3C6H5O7·6H2O is 3.3% by weight of the deionized water, NaHPO2·H2O is 3.8% by weight of the deionized water, and HBO3 is 4% by weight of the deionized water. The nickel plating solution is then prepared. The pH value of the solution is adjusted with HNO3 to 9. Then, a magnetic stirrer is adjusted and, at a temperature of 60°C, 10% of the total mass of the composite agglomerated powder is added to the solution and stirred for 30 minutes. Finally, the powder is filtered out with a filter funnel and dried to obtain the nickel-coated powder.

[0067] (6) Densification of the nickel-coated powder was performed using plasma spheroidization. In the control system, the system pressure, central gas flow rate, and power were set, and the system was started to begin powder feeding. The powder feeding rate was 20 g / min, the system pressure was 82.68 kPa, the power was 35 kW, the carrier gas was N2, the carrier gas flow rate was 3 L / min, and the central gas was Ar + 30 vol.% H2, with a flow rate of 45 L / min. The resulting powder had a particle size of 15 to 45 μm and was used as a spraying material.

[0068] (7) Spray coating. The spraying raw material was sprayed onto the workpiece surface using supersonic plasma spraying technology. During the spraying process, the spraying power was 58 kW, the spraying voltage was 130 V, the spraying current was 500 A, the Ar gas flow rate was 220 L / min, the H2 flow rate was 11 L / min, the powder feeding rate was 15 g / min, the spray gun moving speed was 300 mm / s, the spraying angle was 90°, the number of depositions was 5 times, and the spraying distance was 120 mm.

[0069] (8) Isothermal pre-oxidation heat treatment of the coating: Heat the sprayed coating to 1300°C in an argon atmosphere and keep it warm for 10 hours. Then turn off the power of the heating furnace and allow the coating to cool naturally to room temperature.

[0070] The coating properties prepared in this example are similar to those in Example 1.

[0071] Comparative Example 1

[0072] The coating of this comparative example was prepared by the same method as in Example 1, except that the coating of this comparative example did not contain MAX phase and fibers (as shown in Table 1).

[0073] The friction coefficient and fracture toughness of the coating prepared in this comparative example were measured, and the results are shown in Table 2.

[0074] Comparative Example 2

[0075] The coating of this comparative example was prepared by the same method as in Example 1, except that the coating of this comparative example did not contain the MAX phase (as shown in Table 1).

[0076] The friction coefficient and fracture toughness of the coating prepared in this comparative example were measured, and the results are shown in Table 2.

[0077] Comparative Example 3

[0078] The coating of this comparative example was prepared by the same method as in Example 1, except that the coating of this comparative example did not contain fibers (as shown in Table 1).

[0079] The friction coefficient and fracture toughness of the coating prepared in this comparative example were measured, and the results are shown in Table 2.

[0080] Table 2

[0081] Friction coefficient <![CDATA[Fracture toughness / MPa·m 1 / 2 > Example 1 0.32 4.47 Comparative Example 1 0.56 1.25 Comparative Example 2 0.51 4.58 Comparative Example 3 0.34 1.38

[0082] The comparison in Table 2 shows that the MAX phase plays a primary role in self-lubrication. The self-lubrication principle of MAX phase materials lies in the fact that, under the influence of friction and thermal forces, the M-site (metal) and A-site (aluminum or metalloid) elements diffuse to the material surface and combine with oxygen in the environment to continuously form a stable oxide lubricating film. This lubricating film effectively reduces the material's coefficient of friction and wear rate.

[0083] It can also be seen from the comparison in Table 2 that the addition of fibers is beneficial to the toughening of the coating. The principle of fiber toughening is:

[0084] (1) Crack deflection: When the bonding force between the fiber and the coating molten particles is weak, the crack will deviate from the original path during the propagation process and propagate along the bonding surface between the fiber and the coating molten particles, causing debonding of the fiber-coating molten particle interface, thereby hindering crack propagation.

[0085] (2) Fiber pull-out: During crack propagation, the fiber will be debonded from the coating molten particles and pulled out. The fiber pull-out will relax the stress at the crack tip, slow down the crack propagation, and consume the energy of crack propagation.

[0086] (3) Bridge Effect: When the fibers in the coating form a bridge, their two ends will pull the two crack surfaces, that is, compressive stress will be generated on the crack surface, offsetting part of the external pressure and preventing further expansion of the crack.

[0087] In summary, the coating of the present invention has excellent wear resistance, self-lubricating properties and fracture toughness, and can provide long-term protection for polysilicon powder conveying equipment and pipelines, thereby further improving the purity of polysilicon products and extending the service life of the equipment.

[0088] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A method for preparing a self-lubricating and highly wear-resistant coating, characterized in that: The preparation method comprises the following steps: (1) Wet ball milling TiO2 powder, MAX phase, and fiber to obtain a composite powder, wherein the composite powder has a MAX phase mass fraction of 10-15%, a fiber mass fraction of 2-5%, and the balance is TiO2, and the MAX phase includes one of Ti2AlC, Ti3SiC2, and Cr2AlC; (2) adding the composite powder obtained in step (1) into water, adding polyvinyl alcohol, a dispersant, and a defoaming agent into the water, and continuing ball milling to obtain a slurry; (3) using the slurry obtained in step (2) to spray powder to obtain composite agglomerated powder; (4) performing chemical nickel plating on the composite agglomerated powder obtained in step (3) to obtain nickel-coated powder; (5) treating the nickel-coated powder obtained in step (4) using a plasma spheroidization method to obtain a spraying raw material; (6) spraying the coating material in step (5) onto the surface of the component using supersonic plasma spraying; (7) performing isothermal pre-oxidation heat treatment on the coating sprayed in step (6).

2. The preparation method according to claim 1, wherein: In the step (1), the fiber comprises one of SiC, C, and Al2O3.

3. The preparation method according to claim 1, wherein: In the step (1), the ball-to-material ratio is 3:1, the ball milling speed is 500 r / min, and the ball milling time is 2 h.

4. The preparation method according to claim 1, wherein: In the step (2), the dispersant is polyethylene glycol, the defoaming agent is tributyl phosphate, and after the composite powder is added to water, the solid content in the liquid is 40%, the added mass of the polyvinyl alcohol is 3% of the total mass of the liquid, the added amount of the dispersant is 0.1% of the total mass of the liquid, and the added amount of the defoaming agent is 0.1% of the total mass of the liquid. The ball milling time is 2 hours.

5. The preparation method according to claim 1, wherein: In the step (3), the inlet air temperature of the spray powder making is 235-255°C, the outlet air temperature is 95-105°C, the pressure in the tower is 0.05 kPa, the peristaltic pump opening is 26%, and the atomizer speed is 25000 RPM.

6. The preparation method according to claim 1, wherein: In the step (4), the specific method of chemical nickel plating is: first, adding 3-3.2% of NiSiO4·6H2O by weight of water, 3-3.3% of Na3C6H5O7·6H2O by weight of water, 3.5-3.8% of NaHPO2·H2O by weight of water, and 3.5-4% of HBO3 by weight of water to water to prepare a nickel plating solution; then adding HNO3 to the nickel plating solution to adjust the pH of the nickel plating solution to pH=9; Afterwards, the nickel plating solution is heated to 50-60° C., and under stirring, 10-15% of the total mass of the composite agglomerated powder is added to the nickel plating solution. After nickel plating for 30-60 minutes, the nickel plating solution is filtered to obtain powder, and then the powder is dried to obtain nickel-coated powder.

7. The preparation method according to claim 1, wherein: In the step (5), the powder feeding rate is 15 to 20 g / min, the system pressure is 50 to 82.68 kPa, the power is 30 to 35 kW, the carrier gas is N2, the carrier gas flow rate is 3 L / min, the central gas is a mixed gas of Ar and H2, wherein the volume of H2 accounts for 30% of the total volume of the mixed gas, the mixed gas flow rate is 35 to 45 L / min, and the powder particle size of the coating raw material obtained after plasma spheroidization is 15 to 45 μm.

8. The preparation method according to claim 1, wherein: In the step (6), the supersonic plasma spraying power is 58 kW, the spraying voltage is 130 V, the spraying current is 500 A, the Ar gas flow rate is 220 L / min, the H2 flow rate is 11 L / min, the powder feeding rate is 15 g / min, the spray gun moving speed is 300 mm / s, the spraying angle is 90°, the number of depositions is 5 times, and the spraying distance is 120 mm.

9. The preparation method according to claim 1, wherein: In step (7), the specific process of the isothermal pre-oxidation heat treatment is: heating the coating to 1200-1300° C., keeping the temperature for 10-15 hours, and then allowing the coating to cool naturally to room temperature.

10. The self-lubricating and highly wear-resistant coating prepared by the preparation method according to any one of claims 1 to 9.

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