A method for infiltrating sintered neodymium-iron-boron magnets and a high-performance sintered neodymium-iron-boron magnet

Abstract

The present application provides a kind of sintered neodymium-iron-boron magnet permeation method and high-performance sintered neodymium-iron-boron magnet, the steps of sintered neodymium-iron-boron magnet permeation method include: sintered neodymium-iron-boron magnet surface deposition diffusion source, the magnet of diffusion source deposition completion is segmented gradient pressure permeation diffusion treatment, obtain high coercivity sintered neodymium-iron-boron magnet.The present application can effectively improve the efficiency of grain boundary diffusion after segmented gradient pressure permeation diffusion, and high coercivity sintered neodymium-iron-boron magnet is prepared, compared with pressureless permeation, the process can restore the perpendicularity of magnet, and it is easier to make heavy rare earth elements diffuse into the interior of magnet, can effectively improve the coercivity of sintered neodymium-iron-boron magnet, while pressure tempering treatment can effectively improve the problem of magnet deformation after diffusion heat treatment.

Description

Technical Field

[0001] This invention relates to the field of rare earth permanent magnet materials, and more specifically to a method for infiltrating sintered NdFeB magnets and high-performance sintered NdFeB magnets. Background Technology

[0002] Sintered NdFeB magnets, with their excellent magnetic properties, are widely used in various fields such as household appliances, smart electronic devices, new energy vehicles, and wind power generation. They are indispensable functional materials in emerging industries and high-tech fields, promoting the integration, intelligence, and miniaturization of modern information technology and industrial development. Through decades of technological innovation, process improvement, and equipment optimization, the maximum energy product and remanence of sintered NdFeB magnets can now reach over 90% of the theoretical values, but the coercivity is only about one-third of the theoretical value. Therefore, how to improve the coercivity of sintered NdFeB magnets while maintaining a high maximum energy product and remanence has become a research hotspot in recent years.

[0003] However, the effective diffusion depth of existing technologies using only grain boundary diffusion is very limited, and this technique can only be applied to very thin bulk magnets. Furthermore, insufficient driving force of the diffusing agent on the grain boundaries of sintered NdFeB magnets leads to uneven distribution of the diffusing agent within the magnet, resulting in higher coercivity at the magnet surface and relatively lower coercivity inside. This inevitably reduces the squareness of the magnet after diffusion. Therefore, enhancing the diffusion driving force and increasing the effective diffusion depth of the magnet are imperative.

[0004] In view of the problems and defects of the existing technology, the infiltration method for sintered NdFeB magnets needs further improvement and development. Summary of the Invention

[0005] This invention provides a sintered NdFeB magnet, an infiltration method, and a sintered NdFeB magnet with high coercivity. The specific technical solution is as follows:

[0006] A method for infiltrating sintered NdFeB magnets includes the following steps:

[0007] A diffusion source is deposited on the surface of a sintered NdFeB magnet. The magnet with the diffusion source deposited is then subjected to segmented gradient pressure infiltration diffusion treatment to obtain a sintered NdFeB magnet with high coercivity.

[0008] Furthermore, the pretreatment steps before depositing diffusion sources on the surface of sintered NdFeB magnets are as follows: after polishing the surface of the NdFeB magnets, they are ultrasonically treated with distilled water, dilute nitric acid solution, and anhydrous ethanol in sequence, followed by drying.

[0009] Furthermore, the diffusion source is heavy rare earth Dy, heavy rare earth Tb, alloys or compounds containing Dy, or alloys or compounds containing Tb.

[0010] Furthermore, the specific steps for depositing diffusion sources on the surface of sintered NdFeB magnets are as follows: depositing diffusion sources on two surfaces of the sintered NdFeB magnets that are perpendicular to the easy magnetization axis;

[0011] Furthermore, the deposition methods include, but are not limited to, magnetron sputtering, coating, and electrophoretic deposition;

[0012] Furthermore, the deposited sintered NdFeB magnets obtain a 4-10 μm Tb or Dy film;

[0013] Furthermore, the segmented gradient pressure permeation diffusion treatment is divided into diffusion heat treatment and pressure tempering treatment. The gas pressure for diffusion heat treatment is 2-10 MPa, and the gas pressure for pressure tempering treatment is 1-5 MPa.

[0014] Furthermore, the gas pressure for diffusion heat treatment is 8 MPa, and the gas pressure for pressurized tempering treatment is 3 MPa;

[0015] Furthermore, the diffusion temperature for diffusion heat treatment is 800-900℃, and the temperature for pressure tempering treatment is 450-490℃;

[0016] Furthermore, the diffusion time for diffusion heat treatment is 5-8 hours, and the holding time for pressure tempering treatment is 1-3 hours;

[0017] In addition, the present invention provides a high-performance sintered NdFeB magnet obtained by the above-described infiltration method for sintered NdFeB magnets.

[0018] Due to the adoption of the above technical solutions, the beneficial technical effects of the present invention are as follows:

[0019] 1. The present invention can effectively improve the efficiency of grain boundary diffusion after segmented gradient pressure infiltration diffusion, and produce high coercivity sintered NdFeB magnets. Compared with pressureless infiltration, this method can restore the perpendicularity of the magnet and make it easier for heavy rare earth elements to diffuse into the interior of the magnet, which can effectively improve the coercivity of sintered NdFeB magnets.

[0020] 2. This invention can effectively improve the problem of magnet deformation after diffusion heat treatment through pressure tempering.

[0021] 3. The enhanced diffusion driving force of the present invention can not only increase the effective diffusion depth and improve the coercivity and squareness of the magnet, but also improve the efficiency of grain boundary diffusion and reduce energy consumption. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] A permeation method for sintered NdFeB magnets includes the following steps: depositing a diffusion source on the surface of the sintered NdFeB magnet; subjecting the magnet with the deposited diffusion source to segmented gradient pressure permeation diffusion treatment to obtain a high-coercivity sintered NdFeB magnet. The segmented gradient pressure permeation diffusion treatment consists of diffusion heat treatment and pressure tempering treatment. The gas pressure for diffusion heat treatment is 2-10 MPa, and the gas pressure for pressure tempering treatment is 1-5 MPa. After segmented gradient pressure permeation diffusion, the magnet with the deposited diffusion source can effectively improve the efficiency of grain boundary diffusion, resulting in a high-coercivity sintered NdFeB magnet. The gas pressure values ​​for diffusion heat treatment and pressure tempering treatment form different gradients. Compared with pressureless permeation, this method can restore the perpendicularity of the magnet and facilitate the diffusion of heavy rare earth elements into the interior of the magnet, effectively improving the coercivity of the sintered NdFeB magnet. Simultaneously, pressure tempering can effectively improve the magnet deformation problem after diffusion heat treatment.

[0024] The pretreatment steps before depositing diffusion sources on the surface of sintered NdFeB magnets are as follows: after polishing the surface of the NdFeB magnet, it is ultrasonically treated with distilled water, dilute nitric acid solution, and anhydrous ethanol in sequence, followed by drying. The ultrasonic treatment times are 5 min, 30 s, and 5 min, respectively, to obtain a clean magnet to be deposited.

[0025] The diffusion source is heavy rare earth Dy, heavy rare earth Tb, alloys or compounds containing Dy, or alloys or compounds containing Tb. The specific steps for depositing the diffusion source on the surface of sintered NdFeB magnets are as follows: Dy or Tb is deposited on two surfaces of the sintered NdFeB magnet perpendicular to the easy magnetization axis using magnetron sputtering, coating, or electrophoretic deposition. The magnet sample to be sputtered is placed on the sample stage inside the magnetron sputtering furnace. The target material is 99.9 wt.% high-purity Tb or Dy target material, and the vacuum is evacuated to 1 × 10⁻⁶. -3 -1×10 -4 Pa is filled with argon gas, and Tb or Dy films of different thicknesses are obtained by controlling the sputtering time. The thickness of the heavy rare earth Tb film or Dy film is 4-10 μm.

[0026] Example 1

[0027] A method for infiltrating sintered NdFeB magnets, comprising the following steps:

[0028] (1) Pretreatment before depositing a diffusion source on the surface of sintered NdFeB magnets:

[0029] Sintered NdFeB magnets of grade N40H were selected as the diffusion matrix. The sintered NdFeB magnets were wire-cut into square samples of 15mm×10mm×3mm, with the sample size along the easy magnetization axis being 3mm.

[0030] Polish the surface of the magnet sample with sandpaper until it is smooth and flat. Then, sonicate the cleaned magnet sample with distilled water for 5 minutes, 5wt.% dilute nitric acid solution for 30 seconds, and anhydrous ethanol for 5 minutes in sequence. Finally, blow the magnet surface dry.

[0031] (2) Diffusion source deposition:

[0032] Tb was deposited on two surfaces of the magnet sample perpendicular to the easy magnetization axis. The magnet sample to be sputtered was placed on the sample stage inside the magnetron sputtering furnace. A 99.9 wt.% high-purity Tb target was used, and the vacuum was evacuated to 1 × 10⁻⁶. -3 Below Pa, argon gas is introduced, and the working pressure is 0.6-0.8 Pa. By controlling the sputtering time, Tb films of different thicknesses are obtained, with the thickness of the Tb coating being 6 μm for each coating surface.

[0033] (3) Segmented gradient pressure permeation diffusion treatment:

[0034] Diffusion heat treatment: The magnet sample to be diffused is subjected to diffusion heat treatment in a high-pressure argon atmosphere, with the vacuum level inside the diffusion furnace evacuated to 9 × 10⁻⁶. -3 Below Pa, argon gas is introduced at 2 MPa, and diffusion heat treatment is carried out at 2 MPa pressure; diffusion temperature: 850℃, diffusion time: 5 hours.

[0035] Tempering stage: Argon pressure is 1MPa, tempering temperature is 450℃, and holding time is 1.5 hours to obtain infiltrated sintered NdFeB magnets.

[0036] Example 2

[0037] A method for infiltrating sintered NdFeB magnets, comprising the following steps:

[0038] (1) Pretreatment before depositing a diffusion source on the surface of sintered NdFeB magnets:

[0039] Sintered NdFeB magnets of grade N40H were selected as the diffusion matrix. The sintered NdFeB magnets were wire-cut into square samples of 15mm×10mm×3mm, with the sample size along the easy magnetization axis being 3mm.

[0040] Polish the surface of the magnet sample with sandpaper until it is smooth and flat. Then, sonicate the cleaned magnet sample with distilled water for 5 minutes, 5wt.% dilute nitric acid solution for 30 seconds, and anhydrous ethanol for 5 minutes in sequence. Finally, blow the magnet surface dry.

[0041] (2) Diffusion source deposition:

[0042] Tb was deposited on two surfaces of the magnet sample perpendicular to the easy magnetization axis. The magnet sample to be sputtered was placed on the sample stage inside the magnetron sputtering furnace. A 99.9 wt.% high-purity Tb target was used, and the vacuum was evacuated to 1 × 10⁻⁶. -3 Below Pa, argon gas is introduced, and the working pressure is 0.6-0.8 Pa. By controlling the sputtering time, Tb films of different thicknesses are obtained, with the thickness of the Tb coating being 4 μm for each coating surface.

[0043] (3) Segmented gradient pressure permeation diffusion treatment:

[0044] Diffusion heat treatment: The magnet sample to be diffused is subjected to diffusion heat treatment in a high-pressure argon atmosphere. The vacuum degree in the diffusion furnace is evacuated to below 9×10-3 Pa, and argon gas is introduced at 4 MPa. Diffusion heat treatment is carried out at a pressure of 4 MPa. Diffusion temperature: 900℃, diffusion time: 6 hours.

[0045] Tempering stage: Argon pressure is 1MPa, tempering temperature is 480℃, and holding time is 1 hour to obtain infiltrated sintered NdFeB magnets.

[0046] Example 3

[0047] A method for infiltrating sintered NdFeB magnets, comprising the following steps:

[0048] (1) Pretreatment before depositing a diffusion source on the surface of sintered NdFeB magnets:

[0049] Sintered NdFeB magnets of grade N40H were selected as the diffusion matrix. The sintered NdFeB magnets were wire-cut into square samples of 15mm×10mm×3mm, with the sample size along the easy magnetization axis being 3mm.

[0050] Polish the surface of the magnet sample with sandpaper until it is smooth and flat. Then, sonicate the cleaned magnet sample with distilled water for 5 minutes, 5wt.% dilute nitric acid solution for 30 seconds, and anhydrous ethanol for 5 minutes in sequence. Finally, blow the magnet surface dry.

[0051] (2) Diffusion source deposition:

[0052] Dy was deposited on two surfaces of the magnet sample perpendicular to the easy magnetization axis. The magnet sample to be sputtered was placed on the sample stage inside the magnetron sputtering furnace. The target material was 99.9 wt.% high-purity Dy target material, and the vacuum was evacuated to 1×10⁻⁶. -3 Below Pa, argon gas is introduced, and the working pressure is 0.6-0.8 Pa. By controlling the sputtering time, Dy films of different thicknesses are obtained, with the thickness of the Dy coating being 10 μm for each coating surface.

[0053] (3) Segmented gradient pressure permeation diffusion treatment:

[0054] Diffusion heat treatment: The magnet sample to be diffused is subjected to diffusion heat treatment in a high-pressure argon atmosphere, with the vacuum level inside the diffusion furnace evacuated to 9 × 10⁻⁶. -3 Below Pa, argon gas is introduced at 6 MPa, and diffusion heat treatment is carried out at 6 MPa pressure; diffusion temperature: 800℃, diffusion time: 7 hours.

[0055] Tempering stage: Argon pressure is 2MPa, tempering temperature is 480℃, and holding time is 3 hours to obtain infiltrated sintered NdFeB magnets.

[0056] Example 4

[0057] A method for infiltrating sintered NdFeB magnets, comprising the following steps:

[0058] (1) Pretreatment before depositing a diffusion source on the surface of sintered NdFeB magnets:

[0059] Sintered NdFeB magnets of grade N40H were selected as the diffusion matrix. The sintered NdFeB magnets were wire-cut into square samples of 15mm×10mm×3mm, with the sample size along the easy magnetization axis being 3mm.

[0060] Polish the surface of the magnet sample with sandpaper until it is smooth and flat. Then, sonicate the cleaned magnet sample with distilled water for 5 minutes, 5wt.% dilute nitric acid solution for 30 seconds, and anhydrous ethanol for 5 minutes in sequence. Finally, blow the magnet surface dry.

[0061] (2) Diffusion source deposition:

[0062] Tb was deposited on two surfaces of the magnet sample perpendicular to the easy magnetization axis. The magnet sample to be sputtered was placed on the sample stage inside the magnetron sputtering furnace. A 99.9 wt.% high-purity Tb target was used, and the vacuum was evacuated to 1 × 10⁻⁶. -3 Below Pa, argon gas is introduced, and the working pressure is 0.6-0.8 Pa. By controlling the sputtering time, Tb films of different thicknesses are obtained, with the thickness of the Tb coating being 8 μm for each coating surface.

[0063] (3) Segmented gradient pressure permeation diffusion treatment:

[0064] Diffusion heat treatment: The magnet sample to be diffused is subjected to diffusion heat treatment in a high-pressure argon atmosphere, with the vacuum level inside the diffusion furnace evacuated to 9 × 10⁻⁶. -3 Below Pa, argon gas is introduced at 8 MPa, and diffusion heat treatment is carried out at 8 MPa pressure; diffusion temperature: 850℃, diffusion time: 8 hours.

[0065] Tempering stage: Argon pressure is 1MPa, tempering temperature is 490℃, and holding time is 3 hours to obtain infiltrated sintered NdFeB magnets.

[0066] Example 5

[0067] A method for infiltrating sintered NdFeB magnets, comprising the following steps:

[0068] (1) Pretreatment before depositing a diffusion source on the surface of sintered NdFeB magnets:

[0069] Sintered NdFeB magnets of grade N40H were selected as the diffusion matrix. The sintered NdFeB magnets were wire-cut into square samples of 15mm×10mm×3mm, with the sample size along the easy magnetization axis being 3mm.

[0070] Polish the surface of the magnet sample with sandpaper until it is smooth and flat. Then, sonicate the cleaned magnet sample with distilled water for 5 minutes, 5wt.% dilute nitric acid solution for 30 seconds, and anhydrous ethanol for 5 minutes in sequence. Finally, blow the magnet surface dry.

[0071] (2) Diffusion source deposition:

[0072] Tb was deposited on two surfaces of the magnet sample perpendicular to the easy magnetization axis. The magnet sample to be sputtered was placed on the sample stage inside the magnetron sputtering furnace. A 99.9 wt.% high-purity Tb target was used, and the vacuum was evacuated to 1 × 10⁻⁶. -3 Below Pa, argon gas is introduced, and the working pressure is 0.6-0.8 Pa. By controlling the sputtering time, Tb films of different thicknesses are obtained, with the thickness of the Tb coating being 8 μm for each coating surface.

[0073] (3) Segmented gradient pressure permeation diffusion treatment:

[0074] Diffusion heat treatment: The magnet sample to be diffused is subjected to diffusion heat treatment in a high-pressure argon atmosphere, with the vacuum level inside the diffusion furnace evacuated to 9 × 10⁻⁶. -3 Below Pa, argon gas is introduced at 10 MPa, and diffusion heat treatment is carried out at a pressure of 10 MPa; diffusion temperature: 850℃, diffusion time: 8 hours.

[0075] Tempering stage: Argon pressure is 1MPa, tempering temperature is 490℃, and holding time is 3 hours to obtain infiltrated sintered NdFeB magnets.

[0076] Example 6

[0077] The parts that are the same as in Example 1 will not be repeated here. The difference is that the vacuum degree inside the furnace is evacuated to 9×10. -3 Below Pa, argon gas is introduced at 8 MPa, and diffusion heat treatment is carried out at a pressure of 8 MPa; the argon gas pressure during the tempering stage is 3 MPa.

[0078] Example 7

[0079] The parts that are the same as in Example 1 will not be repeated here. The difference is that the vacuum degree inside the furnace is evacuated to 9×10. -3 Below Pa, argon gas is introduced at 8 MPa, and diffusion heat treatment is performed at 8 MPa pressure; the argon gas pressure during the tempering stage is 5 MPa.

[0080] Comparative Example 1

[0081] The parts of this comparative example that are the same as those in Example 1 will not be repeated here. The differences are as follows:

[0082] The heat treatment process is a conventional heat treatment process and does not involve pressurization. The parameters for the heat treatment process are: diffusion temperature: 850℃, diffusion time: 5 hours, tempering temperature: 450℃, and holding time: 1.5 hours.

[0083] Comparative Example 2

[0084] The parts of this comparative example that are the same as those in Example 1 will not be repeated here. The difference is that the vacuum degree inside the furnace is evacuated to 9×10⁻⁶. -3 Below Pa, argon gas is introduced at 8 MPa, and diffusion heat treatment is carried out at 8 MPa pressure; the tempering stage is not carried out by holding pressure.

[0085] The magnetic properties of the high-performance NdFeB permanent magnet materials obtained in Examples 1-7 and Comparative Examples 1-2 under different pressure diffusion processes are shown in Table 1.

[0086] Table 1 shows the magnetic properties of NdFeB permanent magnet materials obtained in Examples 1-7 and Comparative Examples 1-2 under different pressure diffusion processes.

[0087]

[0088] As shown in Table 1, compared with the original magnet and Comparative Example 1, the sintered NdFeB magnet of the present invention, after segmented pressure diffusion heat treatment, can effectively improve the coercivity of the magnet. Compared with Comparative Example 1, the squareness after pressure diffusion infiltration has a certain degree of recovery, which indicates that the consistency of coercivity has been improved, making the distribution of coercivity inside and outside the magnet more uniform, and effectively increasing the depth of Tb diffusion at grain boundaries. At the same time, comparing Examples 1-7 with Comparative Example 1, the coercivity of the magnets obtained by segmented pressure diffusion has been improved. In Example 6, the coercivity is the largest when the pressure of diffusion heat treatment is 8 MPa and the pressure of tempering stage is 3 MPa, which is 6.36 kOe higher than that of the original magnet. In Examples 5 and 7, the pressure of diffusion heat treatment is 10 MPa, which increases the coercivity of the original magnet by 5.6 kOe and 5.14 kOe, respectively, but the remanence is also reduced significantly, with remanence losses of 0.49 kGs and 0.51 kGs, respectively. This may be related to the excessive pressure, which leads to more heavy rare earth element Tb entering the main phase.

[0089] Comparing Examples 4, 6-7, and Comparative Example 2, the performance of the magnets varied significantly depending on the pressure applied during the tempering stage. Compared to Comparative Example 2 without pressure during tempering, the coercivity of the magnets in Examples 4 and 6-7 increased to some extent. This indicates that the pressure during tempering promotes the formation of rare-earth-rich phases around the grain boundaries, thus enhancing the coercivity of the magnets. On the other hand, comparing Examples 4 and 6-7, the coercivity was highest at a tempering stage pressure of 3 MPa. Beyond 3 MPa, both coercivity and remanence decreased, which may be related to the incorporation of rare-earth-rich phases into the main phase. Furthermore, the surface of the sample in Comparative Example 2 warped, hindering subsequent processing. The surface warping of the sample in Example 4 was slightly improved, and the deformation and warping issues of the magnet samples in Examples 6-7 were resolved, with no warping observed.

[0090] In summary, the sample with the optimal diffusion heat treatment pressure of 8 MPa and the tempering stage pressure of 3 MPa exhibits the best performance.

[0091] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for infiltrating sintered NdFeB magnets, characterized in that, A diffusion source is deposited on the surface of a sintered NdFeB magnet. The magnet with the diffusion source deposited is then subjected to segmented gradient pressure infiltration diffusion treatment to obtain a high-performance sintered NdFeB magnet. The segmented gradient pressure permeation diffusion treatment is divided into diffusion heat treatment and pressurized tempering treatment. The gas pressure for diffusion heat treatment is 8 MPa, and the gas pressure for pressurized tempering treatment is 3 MPa. The diffusion temperature for diffusion heat treatment is 800-900℃, and the temperature for pressure tempering is 450-490℃.

2. The infiltration method for a sintered NdFeB magnet according to claim 1, characterized in that, The pretreatment steps before depositing a diffusion source on the surface of sintered NdFeB magnets are as follows: after polishing the surface of the NdFeB magnets, they are ultrasonically treated with distilled water, dilute nitric acid solution, and anhydrous ethanol in sequence, followed by drying.

3. The infiltration method for a sintered NdFeB magnet according to claim 1, characterized in that, The diffusion source is heavy rare earth Dy, heavy rare earth Tb, alloys or compounds containing Dy, or alloys or compounds containing Tb.

4. The infiltration method for a sintered NdFeB magnet according to claim 3, characterized in that, The specific steps for depositing diffusion sources on the surface of the sintered NdFeB magnet are as follows: depositing diffusion sources on two surfaces of the sintered NdFeB magnet that are perpendicular to the easy magnetization axis.

5. The infiltration method for a sintered NdFeB magnet according to claim 4, characterized in that, The deposited sintered NdFeB magnets yielded Tb or Dy films of 4-10 μm.

6. The infiltration method for a sintered NdFeB magnet according to claim 1, characterized in that, The diffusion time for diffusion heat treatment is 5-8 hours, and the holding time for pressure tempering is 1-3 hours.

7. A high-performance sintered NdFeB magnet obtained by an infiltration method for a sintered NdFeB magnet according to any one of claims 1-6.

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