Preparation and diffusion treatment method for high-performance diffusion coating used for sintered neodymium-iron-boron magnet

Abstract

A preparation and diffusion treatment method for a high-performance diffusion coating used for a sintered neodymium-iron-boron magnet. The method comprises the following steps: the preparation of alloy powders, the preparation of glue, the preparation of a diffusion coating, a pretreatment, coating with the coating, surface drying, and a heat treatment. By controlling the components and particle size of the alloy powders, the compounding of the glue, an anti-bonding powder and an auxiliary agent ensures that under the condition of a relatively small usage amount of a diffusion heavy rare earth metal, the coercive force is greatly improved, the residual magnetism is almost not reduced or is slightly reduced, and the phenomena of the shedding of the coating and the bonding of magnetic sheets after diffusion are avoided.

Description

Preparation and diffusion treatment method of high-performance sintered NdFeB diffusion coating Technical Field

[0001] The invention belongs to the field of grain boundary diffusion technology, and in particular relates to a preparation method and a diffusion treatment method of a high-performance sintered NdFeB diffusion coating. Background Art

[0002] Sintered NdFeB diffusion coatings originate from the grain boundary diffusion (GBD) technology, named by Nakamura et al. in the early 21st century. The invention of this technology laid the theoretical foundation for diffusion coatings. Depending on the diffusion source, GBD can be categorized into surface coating diffusion, surface sputtering diffusion, and vapor evaporation. The surface coating diffusion method involves mixing diffusion source materials, resins, additives, and solvents to form a diffusion coating. The coating is then applied by brushing or spraying, and the coating is dried at low temperature before undergoing high-temperature diffusion treatment. The coating diffusion method has the advantage of increasing the coercivity of the magnet without significantly reducing the remanence. Furthermore, it can effectively reduce the amount of heavy rare earth additives and is suitable for large-scale production, resulting in a major advancement in the magnetic materials industry.

[0003] However, this method currently has some shortcomings. For example, the diffusion depth is insufficient. When the coating amount increases, the effective utilization rate gradually decreases, which not only wastes the coating, but also easily causes sticking (magnetic pieces sticking to each other) and coating peeling. Sticking will directly lead to product scrapping, and coating peeling will cause the diffusion material to separate from the substrate and fail to achieve the purpose of diffusion, resulting in insufficient performance. Summary of the Invention

[0004] The purpose of the present invention is to solve the problems in the background technology and provide a preparation and diffusion treatment method of high-performance sintered NdFeB diffusion coating.

[0005] The above technical objectives of the present invention are achieved through the following technical solutions:

[0006] A method for preparing a high-performance sintered NdFeB diffusion coating comprises the following steps:

[0007] S1, preparation of alloy powder, compounding three alloy powders of M0M1, M2H and M3Fe to obtain composite alloy powder;

[0008] S2, preparation of glue, the resin is completely dissolved in the solvent under mechanical stirring to prepare the glue;

[0009] S3, preparation of diffusion coating, under the protection of inert gas, the composite alloy powder, glue, additives, and anti-adhesion powder are dispersed and stirred at high speed, and then taken out from the inert gas protection environment and continued to be stirred at high speed, and the preparation of the diffusion coating is completed.

[0010] The compounding of three different types (different element types) and sizes of alloy powders of the present invention can achieve a synergistic diffusion effect of multiple alloys, greatly improving the coercive force with a slight decrease in remanence, which is better than the effect of a single material and can also improve the utilization rate of rare earth.

[0011] Rare earths will basically not decrease, and the main reduction will be in heavy rare earths, because heavy rare earths are more expensive than general light rare earths and medium rare earths, and are also scarce.

[0012] The design and use of glue, anti-sticking powder and additives not only ensure that the coating does not fall off after diffusion, but also effectively prevent the adhesion between magnetic sheets after heat treatment.

[0013] After the bonded magnetic sheets are knocked open, there will generally be defects such as chipped corners, pits, and bulges, which will cause the product to be scrapped.

[0014] Three types of alloy powders are used: M0 is one or a combination of Pr or Nd; M1 is one or more combinations of Co, Ni, Al, Cu, Zn, Ga, and Mo; in M2H, M2 is one or more combinations of Dy or Tb, and H is hydrogen; and in M3Fe, M3 is one or more combinations of Gd, Ho, La, and Ce. The alloy powders are prepared using a sequential process of smelting, hydrogen pulverization, and jet milling.

[0015] The composite alloy powder is a compound of three alloy powders: M0M1, M2H and M3Fe. The particle sizes of M0M1, M2H and M3Fe are controlled to 0.5-1μm, 1-3μm and 0.5-1.5μm respectively through smelting, hydrogen crushing and air flow grinding.

[0016] As an improvement, the mass percentages of the three alloy powders M0M1, M2H, and M3Fe are 20%-45%, 35-50%, and 15-20%, respectively.

[0017] The glue is prepared by completely dissolving a resin in a solvent under mechanical stirring. The resin is mainly selected from polyvinyl butyral, polyethylene glycol, polyvinyl alcohol, and polyvinyl pyrrolidone, and the solvent is mainly one or more of terpineol, n-butanol, propylene glycol methyl ether, propylene glycol butyl ether, ethylene glycol butyl ether, ethylene glycol butyl ether acetate, propylene glycol methyl ether acetate, and propylene glycol butyl ether acetate.

[0018] As an improvement, the viscosity of the resin in step S2 is controlled within 2-10 seconds. The viscosity of the resin of the present invention is the Saybolt viscosity, which is the number of seconds required for a certain amount of sample to flow out of 60 ml through a Saybolt viscometer at a specified temperature (e.g., 100°F, 210°F, or 122°F), measured in seconds.

[0019] As an improvement, the mass percentage of the resin in the glue described in the present invention is 60%-85%.

[0020] As an improvement, the auxiliary agent is mainly selected from one or more combinations of γ-(2,3-epoxypropoxy), propyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane.

[0021] As an improvement, the anti-adhesion powder is used to prevent the NdFeB magnetic sheets from adhering to each other during the high-temperature heat treatment process. It is mainly composed of one or more of aluminum oxide, silicon carbide, barium sulfate, titanium oxide, and titanium nitride, and the particle size is controlled within 80-120 μm.

[0022] As an improvement, the diffusion coating has a mass percentage of composite alloy powder of 60-85%, a mass fraction of glue of 13-35%, a mass fraction of additives controlled at 0.5%-1.5%, and a mass fraction of anti-adhesion powder controlled at 2%-5%.

[0023] A diffusion treatment method for high-performance sintered NdFeB diffusion coating, comprising the following steps:

[0024] (1) Pretreatment: The sintered NdFeB substrate is subjected to ultrasonic degreasing, water washing, acid washing, ultrasonic aqueous washing, water washing, pure water washing, and ethanol washing, and then water washing and drying to make its surface clean;

[0025] (2) Coating: The treated sintered NdFeB substrate is placed on a jig, and the diffusion coating is applied to the surface of the sintered NdFeB substrate by spraying, brushing or rolling;

[0026] (3) Surface drying: Level and dry the sprayed sintered NdFeB substrate at 80-130°C for 15-45 minutes, and then cool it to room temperature before discharging.

[0027] (4) Heat treatment: After the surface is dried, the sintered NdFeB substrate is tempered at 850-950℃ for 5-35h, cooled to room temperature, and then tempered at 450-680℃ for 5-10h and cooled to room temperature before discharging. The diffusion treatment is completed.

[0028] In summary, the beneficial effects of the present invention are:

[0029] 1. The compounding of three alloy powders with different structures and components is conducive to optimizing the diffusion channel and increasing the diffusion depth. It not only improves the effective utilization rate of the coating, but also optimizes the microstructure of the substrate and improves the anisotropy of the entire hard magnetic grains. Thus, under the condition of using less diffusion coating (heavy rare earth metal), the coercive force can be greatly improved, and the remanence is almost not reduced or the reduction is very small.

[0030] 2. The design and use of glue, anti-sticking powder and additives not only ensure that the coating does not fall off after diffusion, but also effectively prevent the adhesion between magnetic sheets after heat treatment;

[0031] 3. The high-performance diffusion coating of the present invention, through the control of alloy powder composition and particle size, and the compounding of glue, anti-adhesion powder and additives, ensures that under the use conditions of less diffused rare earth metals, the coercive force can be greatly improved, and the remanence is almost not reduced or the reduction is very small, and it is ensured that the coating does not fall off after diffusion and the bonding between the magnetic sheets occurs. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG1 is a comparison diagram of the performance of NdFeB before diffusion of the present invention and after diffusion of Examples 1-3. DETAILED DESCRIPTION

[0033] The following specific embodiments are merely explanations of the present invention and are not limitations of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to the embodiments as needed. However, as long as they are within the scope of the claims of the present invention, they are protected by patent law.

[0034] The present invention will be described in detail below with reference to the accompanying drawings using embodiments. Example 1

[0035] A method for preparing a high-performance sintered NdFeB diffusion coating comprises the following steps:

[0036] S1, preparation of alloy powder, compounding three alloy powders of M0M1, M2H and M3Fe to obtain composite alloy powder;

[0037] S2, preparation of glue, the resin is completely dissolved in the solvent under mechanical stirring to prepare the glue;

[0038] S3, preparation of diffusion coating, under nitrogen protection and oxygen content ≤0.005%, the composite alloy powder, glue, additives, and anti-adhesion powder are dispersed in a high-speed disperser at 1000 rpm for 30 minutes. After that, it is taken out from the nitrogen protection environment and stirred for 2 hours using a high-speed disperser at 1500 rpm. The diffusion coating is prepared.

[0039] Three types of alloy powders, wherein M0 is one or two combinations of Pr or Nd; M1 is one or more combinations of Co, Ni, Al, Cu, Zn, Ga, and Mo; in M2H, M2 is one or two combinations of Dy or Tb, and H is hydrogen; in M3Fe, M3 is one or more combinations of Gd, Ho, La, and Ce.

[0040] The alloy powder is prepared by smelting, hydrogen crushing and air flow milling. The particle sizes of M0M1, M2H and M3Fe are controlled at 0.5μm, 1μm and 0.5μm respectively through smelting, hydrogen crushing and air flow milling.

[0041] The mass percentages of the three alloy powders M0M1, M2H and M3Fe are 20%5%, 35% and 15% respectively.

[0042] The resin is mainly selected from polyvinyl butyral, and the solvent is mainly one or more combinations of terpineol, n-butanol, propylene glycol methyl ether, propylene glycol butyl ether, ethylene glycol butyl ether, ethylene glycol butyl ether acetate, propylene glycol methyl ether acetate, and propylene glycol butyl ether acetate.

[0043] The viscosity of the resin is controlled at 2 seconds, and the mass percentage of the resin in the glue is 60%.

[0044] The auxiliary agent is mainly selected from one or more combinations of γ-(2,3-epoxypropoxy), propyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane.

[0045] Anti-adhesion powder refers to the powder that prevents the NdFeB magnetic sheets from adhering to each other during the high-temperature heat treatment process. It is mainly composed of one or more of aluminum oxide, silicon carbide, barium sulfate, titanium oxide, and titanium nitride, and the particle size is controlled within 80μm.

[0046] Diffusion coating, the mass percentage of composite alloy powder is 60%, the mass fraction of glue is 13%, the mass fraction of additives is controlled at 0.5%, and the mass fraction of anti-adhesion powder is controlled at 2%.

[0047] A diffusion treatment method for high-performance sintered NdFeB diffusion coating comprises the following steps:

[0048] (1) Pretreatment: The sintered NdFeB substrate is subjected to ultrasonic degreasing, water washing, ultrasonic aqueous washing, acid washing, water washing, pure water washing, and ethanol washing, and then water washing and drying to make its surface clean;

[0049] (2) Coating: The treated sintered NdFeB substrate is placed on the fixture, and the diffusion coating is applied to the surface of the sintered NdFeB substrate by spraying, brushing or rolling;

[0050] (3) Surface drying: Dry the sprayed sintered NdFeB substrate at 80°C for 15 minutes, cool it to room temperature and then discharge it.

[0051] (4) Heat treatment: The sintered NdFeB substrate after surface drying is tempered at 850℃ for 5h, cooled to room temperature, and then tempered at 450℃ for 5h and cooled to room temperature before discharging. The diffusion treatment is completed.

[0052] FIG1 is a comparison chart of the performance of NdFeB before diffusion and after diffusion of Example 1. Example 2

[0053] A method for preparing a high-performance sintered NdFeB diffusion coating comprises the following steps:

[0054] S1, preparation of alloy powder, compounding three alloy powders of M0M1, M2H and M3Fe to obtain composite alloy powder;

[0055] S2, preparation of glue, the resin is completely dissolved in the solvent under mechanical stirring to prepare the glue;

[0056] S3, preparation of diffusion coating, under nitrogen protection and oxygen content ≤0.005%, the composite alloy powder, glue, additives, and anti-adhesion powder are dispersed in a high-speed disperser at 1500 rpm for 20 minutes. After that, it is taken out from the nitrogen protection environment and continued to be stirred for 1 hour using a high-speed disperser at 2000 rpm. The preparation of the diffusion coating is completed.

[0057] Three types of alloy powders, wherein M0 is one or two combinations of Pr or Nd; M1 is one or more combinations of Co, Ni, Al, Cu, Zn, Ga, and Mo; in M2H, M2 is one or two combinations of Dy or Tb, and H is hydrogen; in M3Fe, M3 is one or more combinations of Gd, Ho, La, and Ce.

[0058] The alloy powder is prepared by smelting, hydrogen crushing and air flow milling. The particle sizes of M0M1, M2H and M3Fe are controlled at 1μm, 3μm and 1.5μm respectively through smelting, hydrogen crushing and air flow milling.

[0059] The mass percentages of the three alloy powders M0M1, M2H and M3Fe are 45%, 50% and 20% respectively.

[0060] The resin is mainly selected from polyethylene glycol, and the solvent is mainly one or more combinations of terpineol, n-butanol, propylene glycol methyl ether, propylene glycol butyl ether, ethylene glycol butyl ether, ethylene glycol butyl ether acetate, propylene glycol methyl ether acetate, and propylene glycol butyl ether acetate.

[0061] The viscosity of the resin is controlled within 10 seconds, and the mass percentage of the resin in the glue is 85%.

[0062] The auxiliary agent is mainly selected from one or more combinations of γ-(2,3-epoxypropoxy), propyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane.

[0063] Anti-adhesion powder refers to the powder that prevents the NdFeB magnetic sheets from adhering to each other during the high-temperature heat treatment process. It is mainly composed of one or more of aluminum oxide, silicon carbide, barium sulfate, titanium oxide, and titanium nitride, and the particle size is controlled within 120μm.

[0064] Diffusion coating, the mass percentage of composite alloy powder is 85%, the mass fraction of glue is 35%, the mass fraction of additives is controlled at 1.5%, and the mass fraction of anti-adhesion powder is controlled at 5%.

[0065] A diffusion treatment method for high-performance sintered NdFeB diffusion coating comprises the following steps:

[0066] (1) Pretreatment: The sintered NdFeB substrate is subjected to ultrasonic degreasing, water washing, ultrasonic aqueous washing, acid washing, water washing, pure water washing, and ethanol washing, and then water washing and drying to make its surface clean;

[0067] (2) Coating: The treated sintered NdFeB substrate is placed on the fixture, and the diffusion coating is applied to the surface of the sintered NdFeB substrate by spraying, brushing or rolling;

[0068] (3) Surface drying: The sprayed sintered NdFeB substrate is leveled and dried at 130°C for 45 minutes, and then cooled to room temperature before discharging.

[0069] (4) Heat treatment: The sintered NdFeB substrate after surface drying is tempered at 950℃ for 35h, cooled to room temperature, and then tempered at 680℃ for 10h and cooled to room temperature before discharging. The diffusion treatment is completed. Example 3

[0070] A method for preparing a high-performance sintered NdFeB diffusion coating comprises the following steps:

[0071] S1, preparation of alloy powder, compounding three alloy powders of M0M1, M2H and M3Fe to obtain composite alloy powder;

[0072] S2, preparation of glue, the resin is completely dissolved in the solvent under mechanical stirring to prepare the glue;

[0073] S3, preparation of diffusion coating, under nitrogen protection and oxygen content ≤0.005%, the composite alloy powder, glue, additives, and anti-adhesion powder are dispersed in a high-speed disperser at 1250 rpm for 25 minutes. After that, it is taken out from the nitrogen protection environment and stirred in a high-speed disperser at 1750 rpm for 1.5 hours. The diffusion coating is prepared.

[0074] Three types of alloy powders, wherein M0 is one or two combinations of Pr or Nd; M1 is one or more combinations of Co, Ni, Al, Cu, Zn, Ga, and Mo; in M2H, M2 is one or two combinations of Dy or Tb, and H is hydrogen; in M3Fe, M3 is one or more combinations of Gd, Ho, La, and Ce.

[0075] The alloy powder is prepared by smelting, hydrogen crushing and air flow milling. The particle sizes of M0M1, M2H and M3Fe are controlled at 0.7μm, 2μm and 1μm respectively through smelting, hydrogen crushing and air flow milling.

[0076] The mass percentages of the three alloy powders M0M1, M2H and M3Fe are 33%, 43% and 17% respectively.

[0077] The resin is mainly selected from polyvinyl pyrrolidone, and the solvent is mainly one or more combinations of terpineol, n-butanol, propylene glycol methyl ether, propylene glycol butyl ether, ethylene glycol butyl ether, ethylene glycol butyl ether acetate, propylene glycol methyl ether acetate, and propylene glycol butyl ether acetate.

[0078] The viscosity of the resin is controlled at 6 seconds, and the mass percentage of the resin in the glue is 73%.

[0079] The auxiliary agent is mainly selected from one or more combinations of γ-(2,3-epoxypropoxy), propyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane.

[0080] Anti-adhesion powder refers to the powder that prevents NdFeB magnetic sheets from adhering to each other during high-temperature heat treatment. It is mainly composed of one or more of aluminum oxide, silicon carbide, barium sulfate, titanium oxide, and titanium nitride, and its particle size is controlled within 100μm.

[0081] Diffusion coating, the mass percentage of composite alloy powder is 73%, the mass fraction of glue is 24%, the mass fraction of additives is controlled at 1%, and the mass fraction of anti-adhesion powder is controlled at 3.5%.

[0082] A diffusion treatment method for high-performance sintered NdFeB diffusion coating comprises the following steps:

[0083] (1) Pretreatment: The sintered NdFeB substrate is subjected to ultrasonic degreasing, water washing, ultrasonic aqueous washing, acid washing, water washing, pure water washing, and ethanol washing, and then water washing and drying to make its surface clean;

[0084] (2) Coating: The treated sintered NdFeB substrate is placed on the fixture, and the diffusion coating is applied to the surface of the sintered NdFeB substrate by spraying, brushing or rolling;

[0085] (3) Surface drying: Dry the sprayed sintered NdFeB substrate at 105°C for 30 minutes, cool it to room temperature and then discharge it.

[0086] (4) Heat treatment: The sintered NdFeB substrate after surface drying is tempered at 900℃ for 20h, cooled to room temperature, and then tempered at 565℃ for 7.5h and cooled to room temperature before discharging. The diffusion treatment is completed. Example 4

[0087] A method for preparing a high-performance sintered NdFeB diffusion coating comprises the following steps:

[0088] S1, preparation of alloy powder, compounding three alloy powders of M0M1, M2H and M3Fe to obtain composite alloy powder;

[0089] S2, preparation of glue, the resin is completely dissolved in the solvent under mechanical stirring to prepare the glue;

[0090] S3, preparation of diffusion coating, under the protection of inert gas, the composite alloy powder, glue, additives, and anti-adhesion powder are dispersed and stirred at high speed for 15 minutes through a high-speed stirring device. After that, the mixture is taken out from the inert gas protection environment and continued to be stirred at high speed for 0.5 hours through a secondary stirring mechanism. The preparation of the diffusion coating is completed.

[0091] Three types of alloy powders, wherein M0 is one or two combinations of Pr or Nd; M1 is one or more combinations of Co, Ni, Al, Cu, Zn, Ga, and Mo; in M2H, M2 is one or two combinations of Dy or Tb, and H is hydrogen; in M3Fe, M3 is one or more combinations of Gd, Ho, La, and Ce.

[0092] The alloy powder is prepared by smelting, hydrogen crushing and air flow milling. The particle sizes of M0M1, M2H and M3Fe are controlled at 0.5μm, 1μm and 0.5μm respectively through smelting, hydrogen crushing and air flow milling.

[0093] The mass percentages of the three alloy powders M0M1, M2H and M3Fe are 20%5%, 35% and 15% respectively.

[0094] The resin is mainly selected from polyvinyl alcohol, and the solvent is mainly one or more combinations of terpineol, n-butanol, propylene glycol methyl ether, propylene glycol butyl ether, ethylene glycol butyl ether, ethylene glycol butyl ether acetate, propylene glycol methyl ether acetate, and propylene glycol butyl ether acetate.

[0095] The viscosity of the resin is controlled at 2 seconds, and the mass percentage of the resin in the glue is 60%.

[0096] The auxiliary agent is mainly selected from one or more combinations of γ-(2,3-epoxypropoxy), propyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane.

[0097] Anti-adhesion powder refers to the powder that prevents the NdFeB magnetic sheets from adhering to each other during the high-temperature heat treatment process. It is mainly composed of one or more of aluminum oxide, silicon carbide, barium sulfate, titanium oxide, and titanium nitride, and the particle size is controlled within 80μm.

[0098] Diffusion coating, the mass percentage of composite alloy powder is 60%, the mass fraction of glue is 13%, the mass fraction of additives is controlled at 0.5%, and the mass fraction of anti-adhesion powder is controlled at 2%.

[0099] A diffusion treatment method for high-performance sintered NdFeB diffusion coating comprises the following steps:

[0100] (1) Pretreatment: The sintered NdFeB substrate is subjected to ultrasonic degreasing, water washing, ultrasonic aqueous washing, acid washing, water washing, pure water washing, and ethanol washing, and then water washing and drying to make its surface clean;

[0101] (2) Coating: The treated sintered NdFeB substrate is placed on the fixture, and the diffusion coating is applied to the surface of the sintered NdFeB substrate by spraying, brushing or rolling;

[0102] (3) Surface drying: Dry the sprayed sintered NdFeB substrate at 80°C for 15 minutes, cool it to room temperature and then discharge it.

[0103] (4) Heat treatment: The sintered NdFeB substrate after surface drying is tempered at 850℃ for 5h, cooled to room temperature, and then tempered at 450℃ for 5h and cooled to room temperature before discharging. The diffusion treatment is completed. Example 5

[0104] A method for preparing a high-performance sintered NdFeB diffusion coating comprises the following steps:

[0105] S1, preparation of alloy powder, compounding three alloy powders of M0M1, M2H and M3Fe to obtain composite alloy powder;

[0106] S2, preparation of glue, the resin is completely dissolved in the solvent under mechanical stirring to prepare the glue;

[0107] S3, preparation of diffusion coating, under the protection of inert gas, the composite alloy powder, glue, additives, and anti-adhesion powder are dispersed and stirred at high speed for 15 minutes through a high-speed stirring device. After that, the mixture is taken out from the inert gas protection environment and continued to be stirred at high speed for 0.5 hours through a secondary stirring mechanism. The preparation of the diffusion coating is completed.

[0108] Three types of alloy powders, wherein M0 is one or two combinations of Pr or Nd; M1 is one or more combinations of Co, Ni, Al, Cu, Zn, Ga, and Mo; in M2H, M2 is one or two combinations of Dy or Tb, and H is hydrogen; in M3Fe, M3 is one or more combinations of Gd, Ho, La, and Ce.

[0109] The alloy powder is prepared by smelting, hydrogen crushing and air flow milling. The particle sizes of M0M1, M2H and M3Fe are controlled at 0.5μm, 1μm and 0.5μm respectively through smelting, hydrogen crushing and air flow milling.

[0110] The mass percentages of the three alloy powders M0M1, M2H and M3Fe are 20%5%, 35% and 15% respectively.

[0111] The resin is mainly selected from polyvinyl alcohol, and the solvent is mainly one or more combinations of terpineol, n-butanol, propylene glycol methyl ether, propylene glycol butyl ether, ethylene glycol butyl ether, ethylene glycol butyl ether acetate, propylene glycol methyl ether acetate, and propylene glycol butyl ether acetate.

[0112] The viscosity of the resin is controlled at 2 seconds, and the mass percentage of the resin in the glue is 60%.

[0113] The auxiliary agent is mainly selected from one or more combinations of γ-(2,3-epoxypropoxy), propyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane.

[0114] Anti-adhesion powder refers to the powder that prevents the NdFeB magnetic sheets from adhering to each other during the high-temperature heat treatment process. It is mainly composed of one or more of aluminum oxide, silicon carbide, barium sulfate, titanium oxide, and titanium nitride, and the particle size is controlled within 80μm.

[0115] Diffusion coating, the mass percentage of composite alloy powder is 60%, the mass fraction of glue is 13%, the mass fraction of additives is controlled at 0.5%, and the mass fraction of anti-adhesion powder is controlled at 2%.

[0116] A diffusion treatment method for high-performance sintered NdFeB diffusion coating comprises the following steps:

[0117] (1) Pretreatment: The sintered NdFeB substrate is subjected to ultrasonic degreasing, water washing, ultrasonic aqueous washing, acid washing, water washing, pure water washing, and ethanol washing, and then water washing and drying to make its surface clean;

[0118] (2) Coating: The treated sintered NdFeB substrate is placed on the fixture, and the diffusion coating is applied to the surface of the sintered NdFeB substrate by spraying, brushing or rolling;

[0119] (3) Surface drying: Dry the sprayed sintered NdFeB substrate at 80°C for 15 minutes, cool it to room temperature and then discharge it.

[0120] (4) Heat treatment: The sintered NdFeB substrate after surface drying is tempered at 850℃ for 5h, cooled to room temperature, and then tempered at 450℃ for 5h and cooled to room temperature before discharging. The diffusion treatment is completed.

Claims

1. A method for preparing a high-performance sintered NdFeB diffusion coating, characterized in that: The following steps are involved: S1, preparation of alloy powder, compounding three alloy powders of M0M1, M2H and M3Fe to obtain composite alloy powder; S2, preparation of glue, the resin is completely dissolved in the solvent under mechanical stirring to prepare the glue; S3, preparation of diffusion coating, under the protection of inert gas, the composite alloy powder, glue, additives, and anti-adhesion powder are dispersed and stirred at high speed, and then taken out from the inert gas protection environment and continued to be stirred at high speed, and the preparation of diffusion coating is completed.

2. The method for preparing a high-performance sintered NdFeB diffusion coating according to claim 1, characterized in that: Three types of alloy powders, wherein M0 is one or two combinations of Pr or Nd; M1 is one or more combinations of Co, Ni, Al, Cu, Zn, Ga, and Mo; in M2H, M2 is one or two combinations of Dy or Tb, and H is hydrogen; in M3Fe, M3 is one or more combinations of Gd, Ho, La, and Ce.

3. The method for preparing a high performance sintered NdFeB diffusion coating according to claim 1, characterized in that: The mass percentages of the three alloy powders M0M1, M2H and M3Fe are 20%-45%, 35-50% and 15-20% respectively; the composite alloy powder is a compound of the three alloy powders M0M1, M2H and M3Fe. The particle sizes of M0M1, M2H and M3Fe are controlled at 0.5-1μm, 1-3μm and 0.5-1.5μm respectively through smelting, hydrogen crushing and air flow grinding.

4. The method for preparing a high-performance sintered NdFeB diffusion coating according to claim 1, characterized in that: The diffusion coating has a composite alloy powder content of 60-85%, a glue content of 13-35%, an auxiliary agent content of 0.5-1.5%, and an anti-adhesion powder content of 2-5%.

5. The method for preparing a high performance sintered NdFeB diffusion coating according to claim 1, characterized in that: The resin in step S2 is mainly selected from polyvinyl butyral, polyethylene glycol, polyvinyl alcohol, and polyvinyl pyrrolidone, and the solvent is mainly one or more combinations of terpineol, n-butanol, propylene glycol methyl ether, propylene glycol butyl ether, ethylene glycol butyl ether, ethylene glycol butyl ether acetate, propylene glycol methyl ether acetate, and propylene glycol butyl ether acetate.

6. The method for preparing a high performance sintered NdFeB diffusion coating according to claim 1, characterized in that: The viscosity of the resin in step S2 is controlled at 2-10 seconds, and the mass percentage of the resin is 60%-85%.

7. The method for preparing a high performance sintered NdFeB diffusion coating according to claim 1, characterized in that: The auxiliary agent of S3 is mainly selected from one or more combinations of γ-(2,3-epoxypropoxy), propyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane.

8. The method for preparing a high performance sintered NdFeB diffusion coating according to claim 1, characterized in that: The anti-adhesion powder described in S3 is used to prevent adhesion between NdFeB magnetic sheets during high-temperature heat treatment, and is mainly one or more of aluminum oxide, silicon carbide, barium sulfate, titanium oxide, and titanium nitride, with a particle size controlled within 80-120 μm.

9. A diffusion treatment method for a diffusion coating prepared according to the method for preparing a high-performance sintered NdFeB diffusion coating according to any one of claims 1 to 8, characterized in that: The following steps are involved: (1) Pretreatment: The sintered NdFeB substrate is subjected to ultrasonic degreasing, water washing, ultrasonic aqueous washing, acid washing, water washing, pure water washing, and ethanol washing, and then water washing and drying to make its surface clean; (2) Coating: The treated sintered NdFeB substrate is placed on a jig, and the diffusion coating is applied to the surface of the sintered NdFeB substrate by spraying, brushing or rolling; (3) Surface drying: Level and dry the sprayed sintered NdFeB substrate at 80-130°C for 15-45 minutes, and cool to room temperature before discharging; (4) Heat treatment: After surface drying, the sintered NdFeB substrate is tempered at 850-950℃ for 5-35h, cooled to room temperature, and then tempered at 450-680℃ for 5-10h and cooled to room temperature before discharging. The diffusion treatment is completed.

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