Grain boundary diffusion method for simultaneous optimization of coercivity and remanence temperature coefficient of sintered NdFeB magnets

Abstract

The present invention provides a grain boundary diffusion method for synchronously optimizing the coercive force and remanent magnetization temperature coefficient of a sintered NdFeB magnet. The method comprises the following steps: first, preparing a heavy rare earth element coating R1-A1 on the surface of a NdFeB magnet perpendicular to an orientation C-axis; R1 is at least one of Tb and Dy, and A1 is at least two of Al, Mg, Zn, Cu, Pr, and Nd; then preparing a Co element coating Co-A2 on the surface of the NdFeB magnet parallel to the orientation C-axis; A2 is at least two of Gd, Nd, Al, Mg, Zn, and Cu; after the heavy rare earth element coating R1-A1 and the Co element coating Co-A2 are prepared, the NdFeB magnet perpendicular to and parallel to the orientation C-axis is heat treated. The present invention has a reasonable concept, can achieve synchronous optimization of the coercive force and remanent magnetization temperature coefficient of a sintered NdFeB magnet, and is suitable for promotion and application.

Description

Technical Field

[0001] The invention belongs to the field of rare earth permanent magnet material surface engineering, and in particular relates to a grain boundary diffusion method for synchronously optimizing the coercive force and remanence temperature coefficient of a sintered NdFeB magnet. Background Art

[0002] High power density and high speed have become the mainstream trends in the development of high-performance rare earth permanent magnet motors. As the core material for energy conversion in rare earth permanent magnet motors, neodymium iron boron (NdFeB) magnets offer significant advantages in improving motor power density and speed due to their exceptional magnetic properties, such as ultra-high remanence (Br) and magnetic energy product (BH)max. Remanence (Br) is a key factor influencing a motor's power density and speed, while intrinsic coercivity (Hcj) represents the magnet's ability to resist external magnetic field perturbations and is closely linked to the motor's stable operation. However, the intrinsic coercivity (Hcj) of NdFeB magnets is significantly lower than their magnetocrystalline anisotropy field (HA), limiting their ability to resist external magnetic field perturbations. Furthermore, increasing motor power density and speed leads to more severe eddy current losses, resulting in a continuous increase in the motor's internal ambient temperature. The Curie temperature (Tc) of the main phase of NdFeB magnets, the Nd2Fe14B compound, is low. As temperature increases, both Br and Hcj decrease significantly. This deterioration in the former prevents the motor from providing the magnetic field environment required for high power density and high speed. The deterioration of the latter further reduces the magnet's ability to resist external magnetic field disturbances, especially the inability to resist the high reverse magnetic field generated by the stator winding under high speed and high torque conditions of the motor, resulting in overall or local thermal demagnetization of the magnet, causing the motor output power to drop or even fail.

[0003] Heavy rare earth grain boundary diffusion technology is the most commonly used technology in the industry to prepare high coercivity NdFeB magnets. It forms a high magnetocrystalline anisotropy field (Nd, Dy / Tb)2Fe on the main phase surface. 14 The B shell, i.e. the "shell-core" structure, increases the coercivity, thereby compensating for the loss of coercivity at high temperatures. 14 Compound B has a higher Curie temperature T c (Nd2Fe 14 B:312℃ <Dy2Fe 14 B:319℃ <Tb2Fe 14 B: 347℃), which can play a positive role in reducing the remanence temperature coefficient to a certain extent. In addition, compared with the above compounds, Nd2Co 14 Compound B has a higher Curie temperature T c Therefore, adding an appropriate amount of Co element to the heavy rare earth diffusion source is currently a common technical means to increase the coercivity and reduce the remanence temperature coefficient.

[0004] During the grain boundary diffusion process, the diffusion source of heavy rare earth + Co is usually deposited on the surface of the magnet perpendicular to the orientation C axis, and then diffuses into the interior of the magnet along the grain boundary under high temperature driving. Since the diffusion temperature is usually higher than 800 ° C, the grain boundary phase has changed from solid phase to liquid phase, so the diffusion ability of Co element in the grain boundary is much higher than its diffusion into the interior of the grain. At the same time, the diffusion coefficient of heavy rare earth elements is relatively high, and they often diffuse into the interior of the magnet before Co elements, and form a heavy rare earth-rich shell on the surface of the main phase, which to a certain extent hinders the entry of Co elements into the interior of the grains. The above two factors cause a large amount of Co elements to be enriched in the grain boundary phase, and cannot enter the interior of the grain to form enough Nd2Co 14 B compounds tend to form a 1:2 Laves soft magnetic phase. Therefore, heavy rare earth + Co co-diffusion often fails to simultaneously improve both coercivity and remanence temperature stability, and instead deteriorates magnetic properties. Therefore, there is an urgent need to develop a new grain boundary diffusion technology for heavy rare earth + Co co-diffusion to simultaneously optimize the coercivity and remanence temperature coefficient of sintered NdFeB magnets. Summary of the Invention

[0005] In response to the technical problems existing in the above background technology, the present invention proposes a grain boundary diffusion method for synchronously optimizing the coercive force and remanent magnetization temperature coefficient of sintered NdFeB magnets. The method has a reasonable concept and can achieve synchronous optimization of the coercive force and remanent magnetization temperature coefficient of sintered NdFeB magnets.

[0006] To solve the above technical problems, the present invention provides a grain boundary diffusion method for simultaneously optimizing the coercive force and remanence temperature coefficient of a sintered NdFeB magnet. The method comprises the following steps: first, preparing a coating R1-A1 containing a heavy rare earth element on the surface of the NdFeB magnet perpendicular to the orientation C axis; R1 is at least one of Tb and Dy, and A1 is at least two of Al, Mg, Zn, Cu, Pr, and Nd; then, preparing a coating Co-A2 containing a Co element on the surface of the NdFeB magnet parallel to the orientation C axis; A2 is at least two of Gd, Nd, Al, Mg, Zn, and Cu; after preparation of the coating R1-A1 containing a heavy rare earth element and the coating Co-A2 containing a Co element, the NdFeB magnet perpendicular to and parallel to the orientation C axis is heat treated.

[0007] The grain boundary diffusion method for synchronously optimizing the coercive force and remanence temperature coefficient of sintered NdFeB magnets specifically comprises the following steps:

[0008] 1) Surface coating pretreatment of sintered NdFeB magnets

[0009] The surfaces of the NdFeB magnet perpendicular to and parallel to the orientation C axis are sequentially subjected to sandpaper grinding, polishing, alcohol ultrasonic cleaning and drying treatments; a coating deposition device is used to deposit a heavy rare earth element coating and a Co element coating, the coating deposition device comprising a vacuum chamber, a workpiece holder matched and arranged in the center of the vacuum chamber, a heavy rare earth element target, a first auxiliary element target, a second auxiliary element target, a Co element target, a third auxiliary element target, a fourth auxiliary element target and an anode layer ion source matched and arranged on the circumference of the vacuum chamber; the heavy rare earth element target is connected to a first magnetron sputtering power supply; the fourth auxiliary element target is connected to a second magnetron sputtering power supply A magnetron sputtering power supply is connected to the third auxiliary element target, the Co element target is connected to the fourth magnetron sputtering power supply, the second auxiliary element target is connected to the fifth magnetron sputtering power supply, and the first auxiliary element target is connected to the sixth magnetron sputtering power supply; an NdFeB magnet is installed in a coating fixture, the fixture includes a stainless steel base, a stainless steel pillar matched and mounted in the center of the upper part of the stainless steel base, and a stainless steel pressing block matched and mounted on the upper part of the stainless steel pillar; a circular through hole is matched on the stainless steel pressing block; specifically, the NdFeB magnet is installed in the circular through hole of the fixture and fixed with a screw, and then the coating fixture is placed on the workpiece holder;

[0010] 2) Glow cleaning of NdFeB magnet surface perpendicular to the orientation C axis

[0011] Pump the vacuum chamber to 5*10 -3 Pa or less; then, Ar gas is introduced into the vacuum chamber and the gas flow rate is adjusted to make the vacuum degree of the vacuum chamber 1Pa to 3Pa; a negative bias power supply is applied to the workpiece holder through the bias power supply, and the voltage parameters and cleaning time are set to complete the glow cleaning of the NdFeB magnet surface perpendicular to the orientation C axis;

[0012] 3) Deposition of coatings containing heavy rare earth elements

[0013] The Ar gas flow rate is reduced to adjust the pressure of the vacuum chamber to 0.5 Pa-1 Pa, and the rotation of the workpiece holder is started; the first magnetron sputtering power supply, the sixth magnetron sputtering power supply, and the second magnetron sputtering power supply are turned on to co-sputter the heavy rare earth element target, the first auxiliary element target, and the fourth auxiliary element target; a negative bias power supply is applied to the workpiece holder, and then a heavy rare earth element-containing coating is deposited on the surface of the NdFeB magnet perpendicular to the orientation C axis;

[0014] 4) Replace the coating fixture

[0015] After the NdFeB magnet cools to room temperature, the sample is removed from the vacuum chamber and the heavy rare earth element coating R1-A1 is deposited. The NdFeB magnet is then placed in a coating fixture and placed on a workpiece holder.

[0016] 5) Glow cleaning of NdFeB magnet surface parallel to the orientation C axis

[0017] Pump the vacuum chamber of the coating deposition device to 5*10 -3 Pa or less; then introduce Ar gas and adjust the gas flow rate to make the vacuum degree of the vacuum chamber 1Pa ~ 3Pa; load the workpiece holder with a negative bias power supply through the bias power supply, and set the voltage parameters and cleaning time to complete the glow cleaning of the NdFeB magnet surface parallel to the orientation C axis;

[0018] 6) Co-containing coating deposition

[0019] The Ar gas flow rate is reduced to make the gas pressure of the vacuum chamber 0.5Pa-1Pa, and the rotation of the workpiece holder is started; the fourth magnetron sputtering power supply, the fifth magnetron sputtering power supply and the third magnetron sputtering power supply are turned on to co-sputter the Co element target, the second auxiliary element target and the third auxiliary element target; a negative bias power supply is applied to the workpiece holder, and a DC pulse power supply is turned on at the same time to start the anode layer ion source, increase the ion density, and increase the sputtering amount of the Co element, thereby avoiding a decrease in the sputtering magnetic field due to the high magnetic permeability of the Co element target; and then a Co element-containing coating is deposited on the surface of the NdFeB magnet parallel to the orientation C axis;

[0020] 7) Vacuum heat treatment

[0021] After the NdFeB magnet cools to room temperature, the sample is removed from the vacuum chamber, and the deposition of the heavy rare earth element coating R1-A1 and the Co element coating Co-A2 is completed. The sample is then placed in a vacuum diffusion furnace for heat treatment.

[0022] 8) After the NdFeB magnet cools to room temperature, take out the sample and perform magnetic property testing.

[0023] The grain boundary diffusion method for synchronously optimizing the coercive force and remanence temperature coefficient of sintered NdFeB magnets, wherein: the specific parameter setting range of the vacuum cavity in the step 2) is: voltage value -400V to -600V, frequency 20kHz to 100kHz, duty cycle 20% to 80%, and cleaning time 5min to 30min.

[0024] The grain boundary diffusion method for simultaneously optimizing the coercive force and remanence temperature coefficient of sintered NdFeB magnets, wherein: the heavy rare earth element target in step 3) contains at least one of Tb and Dy, the first auxiliary element target contains at least one of Al, Mg, Zn, Cu, Pr, and Nd, the fourth auxiliary element target contains at least one of Al, Mg, Zn, Cu, Pr, and Nd, and the elements contained in the first auxiliary element target and the fourth auxiliary element target should not overlap.

[0025] The grain boundary diffusion method for synchronously optimizing the coercive force and remanence temperature coefficient of sintered NdFeB magnets, wherein: the rotation speed range of the workpiece holder in step 3) is: 3-20 rpm;

[0026] The parameter ranges of the first magnetron sputtering power supply, the sixth magnetron sputtering power supply, and the second magnetron sputtering power supply in step 3) are: sputtering power density is 1w / cm2-12w / cm2, pulse frequency is 30kHz-150kHz, and duty cycle is 20%-80%;

[0027] The specific parameter range of the negative bias power supply in step 3) is: bias voltage of -30V to -150V, pulse frequency of 20kHz to 100kHz, and duty cycle of 20% to 80%;

[0028] In the step 3), the deposition time of the heavy rare earth element-containing coating on the surface of the NdFeB magnet perpendicular to the oriented C axis is 30 min to 60 min.

[0029] The grain boundary diffusion method for synchronously optimizing the coercive force and remanence temperature coefficient of sintered NdFeB magnets, wherein: in step 4), the NdFeB magnet is installed between the stainless steel support and the stainless steel pressing block of the coating fixture.

[0030] The grain boundary diffusion method for simultaneously optimizing the coercive force and remanence temperature coefficient of sintered NdFeB magnets, wherein: the second auxiliary element target in step 6) contains at least one of Gd, Nd, Al, Mg, Zn, and Cu, and the third auxiliary element target contains at least one of Gd, Nd, Al, Mg, Zn, and Cu, and the elements contained in the second auxiliary element target and the third auxiliary element target should not overlap.

[0031] The grain boundary diffusion method for synchronously optimizing the coercive force and remanence temperature coefficient of sintered NdFeB magnets, wherein: the rotation speed range of the workpiece holder in step 6) is: 1-20 rpm;

[0032] In step 6), the parameter ranges of the fourth magnetron sputtering power supply, the fifth magnetron sputtering power supply, and the third magnetron sputtering power supply are: sputtering power density of 1w / cm2-12w / cm2, pulse frequency of 30kHz-150kHz, and duty cycle of 20%-80%;

[0033] In step 6), the negative bias power supply parameter range is: bias voltage is -20V to -250V, pulse frequency is 20kHz to 100kHz, and duty cycle is 20% to 80%; the DC pulse power supply parameter range is: power 2kW to 5kW, frequency is 40kHz to 150kHz, and duty cycle is 20% to 80%;

[0034] In the step 6), the Co-containing coating is deposited on the surface of the NdFeB magnet parallel to the oriented C axis for a deposition time of 30 min to 90 min.

[0035] The grain boundary diffusion method for simultaneously optimizing the coercive force and remanence temperature coefficient of sintered NdFeB magnets, wherein: the heat treatment in step 7) includes high-temperature thermal diffusion and low-temperature annealing; the parameter range of the high-temperature thermal diffusion is: diffusion temperature 800°C-950°C, time 5-10 hours; the parameter range of the low-temperature annealing is: annealing temperature 450°C-520°C, time 4-6 hours; the vacuum degree of the vacuum chamber in step 7) is less than 10-2Pa.

[0036] By adopting the above technical solution, the present invention has the following beneficial effects:

[0037] The present invention proposes a novel grain boundary diffusion method for simultaneously optimizing the coercivity and remanence temperature coefficient of sintered NdFeB magnets. Unlike existing methods, the present invention does not simultaneously deposit heavy rare earth elements and Co on the magnet surface perpendicular to the orientation C-axis. Instead, it separates the two and proposes a novel method for depositing a heavy rare earth element coating and a Co element coating on the magnet surface perpendicular and parallel to the orientation C-axis, respectively. This method, based on the anisotropy of the Nd2Fe14B compound crystal structure, demonstrates that when heavy rare earth elements diffuse parallel to the orientation C-axis, they replace Nd in Nd2Fe14B with a longer diffusion path, a greater diffusion activation energy, and a lower diffusion coefficient than when they diffuse perpendicular to the orientation C-axis. Consequently, the heavy rare earth elements are less likely to undergo lattice diffusion, forming only a heavy rare earth shell on the main phase surface. This allows more heavy rare earth elements to enter the magnet interior along the grain boundaries, increasing the diffusion depth and further improving the coercivity. When the Co element diffuses perpendicular to the orientation C axis, it replaces the Fe element in Nd2Fe14B without being hindered by the Nd element. Therefore, its lattice diffusion coefficient is high and the diffusion activation energy is low, making it easier for the Co element to enter the main phase, thereby inhibiting the aggregation of the Co element at the grain boundary phase and inducing the formation of more high-Nd2Co14B compounds inside the magnet, thereby reducing the remanent magnetization temperature coefficient of the magnet. Based on the above two points, it is finally possible to achieve the simultaneous optimization of the coercive force and remanent magnetization temperature coefficient of sintered NdFeB magnets.

[0038] To address the problem of low Co sputtering yields caused by a drop in the sputtering magnetic field due to the high magnetic permeability of the Co target, the present invention proposes the use of magnetron sputtering combined with an auxiliary anode layer ion source to prepare a Co-containing coating. This anode layer ion source excites a high-density plasma, increasing the Ar ion concentration in the vacuum atmosphere, allowing more Ar ions to sputter the Co target. This method achieves a high Co sputtering yield even when the sputtering magnetic field is weakened, ensuring a high deposition rate for the Co-containing coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0040] Figure 1 Schematic diagram of the deposition of a heavy rare earth element coating and a Co element coating on the surface of a sintered NdFeB magnet involved in the grain boundary diffusion method for simultaneously optimizing the coercive force and remanence temperature coefficient of a sintered NdFeB magnet according to the present invention ( Figure 1 The orientation "C axis" in is the S pole or the N pole);

[0041] Figure 2 Schematic diagram of the structure of the coating deposition device containing heavy rare earth elements and the coating containing Co element involved in the grain boundary diffusion method for simultaneously optimizing the coercive force and remanence temperature coefficient of sintered NdFeB magnets of the present invention;

[0042] Figure 3 A schematic structural diagram of a coating fixture for depositing a coating on the surface of a magnet perpendicular to the orientation C-axis involved in the grain boundary diffusion method for simultaneously optimizing the coercive force and remanence temperature coefficient of a sintered NdFeB magnet according to the present invention;

[0043] Figure 4 A schematic structural diagram of a coating fixture for depositing a coating on the magnet surface parallel to the orientation C-axis involved in the grain boundary diffusion method for simultaneously optimizing the coercive force and remanence temperature coefficient of a sintered NdFeB magnet according to the present invention;

[0044] Figure 5 Demagnetization curves of the substrate at 20°C and 180°C involved in the grain boundary diffusion method for simultaneously optimizing the coercive force and remanence temperature coefficient of sintered NdFeB magnets of the present invention;

[0045] Figure 6 Graph showing demagnetization curves of the diffused magnet at 20° C. and 180° C. involved in the grain boundary diffusion method for simultaneously optimizing the coercive force and remanence temperature coefficient of sintered NdFeB magnets according to Example 1 of the present invention;

[0046] Figure 7 Graph showing demagnetization curves of a diffused magnet at 20° C. and 180° C. involved in the grain boundary diffusion method for simultaneously optimizing the coercive force and remanence temperature coefficient of a sintered NdFeB magnet according to Example 2 of the present invention;

[0047] Figure 8 This is a demagnetization curve diagram of the diffused magnet at 20° C. and 180° C. involved in the grain boundary diffusion method for simultaneously optimizing the coercive force and remanence temperature coefficient of sintered NdFeB magnets according to Example 3 of the present invention. DETAILED DESCRIPTION

[0048] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0049] The present invention will be further explained below with reference to specific embodiments.

[0050] like Figure 1 As shown, the grain boundary diffusion method for simultaneously optimizing the coercive force and remanence temperature coefficient of sintered NdFeB magnets of the present invention comprises the following steps: first, a coating R1-A1 containing heavy rare earth elements is prepared on the surface of the NdFeB magnet 2 perpendicular to the orientation C-axis; R1 is at least one of Tb and Dy, and A1 is at least two of Al, Mg, Zn, Cu, Pr, and Nd; then, a coating Co-A2 containing Co elements is prepared on the surface of the NdFeB magnet 2 parallel to the orientation C-axis; A2 is at least two of Gd, Nd, Al, Mg, Zn, and Cu; after the coating is prepared, the NdFeB magnet 2 perpendicular to and parallel to the orientation C-axis is heat treated.

[0051] The grain boundary diffusion method for simultaneously optimizing the coercive force and remanence temperature coefficient of sintered NdFeB magnets of the present invention specifically comprises the following steps:

[0052] S001, Surface coating pretreatment of sintered NdFeB magnet 2

[0053] The surfaces of the NdFeB magnet 2 perpendicular to and parallel to the orientation C axis are sequentially subjected to sandpaper grinding, polishing, alcohol ultrasonic cleaning and drying treatments; a coating deposition device is used to deposit a heavy rare earth element coating and a Co element coating; wherein the coating deposition device comprises a vacuum chamber 1, a workpiece holder 3 matched and arranged in the center of the vacuum chamber 1, a heavy rare earth element target 4, a first auxiliary element target 5, a second auxiliary element target 6, a Co element target 7, a third auxiliary element target 8, and a plurality of other targets matched and arranged on the circumference of the vacuum chamber 1. The heavy rare earth element target 8, the fourth auxiliary element target 9 and the anode layer ion source 17; the heavy rare earth element target 4 is connected to the first magnetron sputtering power supply 10; the fourth auxiliary element target 9 is connected to the second magnetron sputtering power supply 11, the third auxiliary element target 8 is connected to the third magnetron sputtering power supply 12, the Co element target 7 is connected to the fourth magnetron sputtering power supply 13, the second auxiliary element target 6 is connected to the fifth magnetron sputtering power supply 14, and the first auxiliary element target 5 is connected to the sixth magnetron sputtering power supply 15; the NdFeB magnet 2 is installed as shown in FIG. Figure 3The coating fixture shown (the coating fixture includes a stainless steel base 05, a stainless steel pillar 04 matched with the center of the upper part of the stainless steel base 05, and a stainless steel pressing block 01 matched with the upper part of the stainless steel pillar 04; the stainless steel pressing block 01 is matched with a plurality of circular through holes 02) is placed in the through hole and the NdFeB magnet 2 is fixed with screws 03. Then the coating fixture is placed on the workpiece holder 3.

[0054] S002. Glow cleaning of the surface of NdFeB magnet 2 perpendicular to the orientation C axis

[0055] Pump the vacuum chamber 1 to 5*10 -3 Pa or less; Ar gas is then introduced into the vacuum chamber 1 and the gas flow rate is adjusted to achieve a vacuum level of 1 Pa to 3 Pa; a negative bias voltage is applied to the workpiece holder 3 via the bias power supply 16, and the voltage parameters and cleaning time are set to complete the glow cleaning of the surface of the NdFeB magnet 2 perpendicular to the oriented C axis. The specific parameter settings for the vacuum chamber 1 are: voltage value -400 V to -600 V, frequency 20 kHz to 100 kHz, duty cycle 20% to 80%, and cleaning time 5 minutes to 30 minutes.

[0056] S003, coating deposition containing heavy rare earth elements

[0057] The Ar gas flow rate is reduced to a pressure of 0.5 Pa to 1 Pa in the vacuum chamber 1, and the workpiece holder 3 is started to rotate. The first magnetron sputtering power supply 10, the sixth magnetron sputtering power supply 15, and the second magnetron sputtering power supply 11 are turned on to co-sputter the heavy rare earth element target 4, the first auxiliary element target 5, and the fourth auxiliary element target 9. A negative bias power supply 16 is applied to the workpiece holder 3, and then a heavy rare earth element-containing coating is deposited on the surface of the NdFeB magnet 2 perpendicular to the orientation C axis. The heavy rare earth element target 4 contains at least one of Tb and Dy, the first auxiliary element target 5 contains at least one of Al, Mg, Zn, Cu, Pr, and Nd, and the fourth auxiliary element target 9 contains at least one of Al, Mg, Zn, Cu, Pr, and Nd. The elements contained in the first auxiliary element target 5 and the fourth auxiliary element target 9 should not overlap. The speed range of the workpiece holder 3 is: 3-20rpm; the parameter ranges of the first magnetron sputtering power supply 10, the sixth magnetron sputtering power supply 15 and the second magnetron sputtering power supply 11 are: sputtering power density is 1w / cm2-12w / cm2, the pulse frequency is 30kHz-150kHz, and the duty cycle is 20%-80%; the specific parameter range of the negative bias power supply 16 is: bias is -30V~-150V, the pulse frequency is 20kHz-100kHz, and the duty cycle is 20%-80%; the deposition time of the heavy rare earth element coating on the surface of the NdFeB magnet 2 perpendicular to the oriented C axis is 30min-60min.

[0058] S004. Replace the coating fixture

[0059] After the NdFeB magnet 2 cools to room temperature, the sample is removed from the vacuum chamber 1 and the heavy rare earth element coating R1-A1 is deposited. The NdFeB magnet 2 is then placed in a coating fixture (specifically, between the stainless steel support 04 and the stainless steel block 01 of the coating fixture) and placed on the workpiece holder 3 of the coating deposition device.

[0060] S005. Glow cleaning of the surface of NdFeB magnet 2 parallel to the orientation C axis

[0061] Pump the vacuum chamber 1 of the coating deposition device to 5*10 -3 Pa or less; then introduce Ar gas and adjust the gas flow rate so that the vacuum degree of the vacuum chamber 1 is 1Pa to 3Pa; apply a negative bias power supply 16 to the workpiece holder 3 through the bias power supply 16, and set the voltage parameters and cleaning time to complete the glow cleaning of the surface of the NdFeB magnet 2 parallel to the orientation C axis;

[0062] S006, Co-containing coating deposition

[0063] Reduce the Ar gas flow rate to make the gas pressure of the vacuum chamber 1 0.5Pa-1Pa, and start the rotation of the workpiece holder 3; turn on the fourth magnetron sputtering power supply 13, the fifth magnetron sputtering power supply 14 and the third magnetron sputtering power supply 12 to co-sputter the Co element target 7, the second auxiliary element target 6 and the third auxiliary element target 8; load the workpiece holder 3 with a negative bias power supply 16, and at the same time turn on the DC pulse power supply 18 and start the anode layer ion source 17 to increase the ion density and the amount of Co element sputtering, thereby avoiding the drop of the sputtering magnetic field due to the high magnetic permeability of the Co element target 7; then deposit the Co element coating on the surface of the NdFeB magnet 2 parallel to the oriented C axis. The elements contained in the aforementioned second auxiliary element target 6 are at least one of Gd, Nd, Al, Mg, Zn and Cu, and the elements contained in the third auxiliary element target 8 are Gd, Nd, Al, Mg, Zn and Cu. l, Mg, Zn, Cu at least one, and the elements contained in the second auxiliary element target 6 and the third auxiliary element target 8 should not overlap; the rotation speed range of the workpiece holder 3 is: 1-20rpm; the parameter ranges of the fourth magnetron sputtering power supply 13, the fifth magnetron sputtering power supply 14 and the third magnetron sputtering power supply 12 are: sputtering power density is 1w / cm2-12w / cm2, the pulse frequency is 30kHz-150kHz, and the duty cycle is 20%-80%; the parameter range of the negative bias power supply 16 is: bias is -20V~-250V, the pulse frequency is 20kHz-100kHz, and the duty cycle is 20%-80%; the parameter range of the DC pulse power supply 18 is: power 2kW-5kW, frequency is 40kHz-150kHz, and duty cycle is 20%-80%; the Co element coating is deposited on the surface of the NdFeB magnet 2 parallel to the orientation C axis for a deposition time of 30min-90min.

[0064] S007, vacuum heat treatment

[0065] After cooling the NdFeB magnet 2 to room temperature, remove the sample from the vacuum chamber and deposit the heavy rare earth element coating R1-A1 and the Co-containing coating Co-A2. The sample is then placed in a vacuum diffusion furnace for heat treatment. The heat treatment includes high-temperature thermal diffusion and low-temperature annealing. The high-temperature thermal diffusion parameters range from 800°C to 950°C for 5-10 hours, and the low-temperature annealing parameters range from 450°C to 520°C for 4-6 hours. The vacuum chamber in step 7) maintains a vacuum level of less than 10-2 Pa.

[0066] S008. After the NdFeB magnet 2 cools to room temperature, take out the sample and perform magnetic property testing.

[0067] The present invention uses a grain boundary diffusion method for simultaneously optimizing the coercive force and remanence temperature coefficient of a sintered NdFeB magnet. A sintered NdFeB magnet 2 with a grade of 45SH, a diameter of 10 mm, and a thickness of 3 mm is used as an experimental sample. The magnetic properties of the NdFeB magnet 2 are tested using a pulse magnetic field intensity meter. The demagnetization curve, remanence, coercive force, and remanence temperature coefficient are shown in FIG. Figure 5 and as shown in Table 1. Subsequently, the following three examples were carried out using the NdFeB magnet 2 from this batch as the substrate.

[0068] Table 1 Remanence, coercivity and remanence temperature coefficient of substrate

[0069] <![CDATA[Residual magnetism B r (20 °C)]]> <![CDATA[Coercive force H cj (at 20 °C)]]> <![CDATA[Remanence temperature coefficient | α(B r ) | (20 °C - 180 °C)]]> 13.61kGs 21.83kOe 0.137％ / ℃

[0070] Example 1:

[0071] In this embodiment 1, R1 of the heavy rare earth element coating R1-A1 is the heavy rare earth element Tb, and A1 is the element Mg and Pr, corresponding to Figure 2 The first auxiliary element target 5 and the fourth auxiliary element target 9. A2 in the Co-containing element coating Co-A2 is the element Gd and Cu, corresponding to Figure 2 The second auxiliary element target 6 and the third auxiliary element target 8 are deposited on the surface of the NdFeB magnet 2 perpendicular to and parallel to the orientation C axis using magnetron sputtering, respectively, and then vacuum heat treatment is performed. The specific treatment process is as follows:

[0072] S101, sintered NdFeB magnet 2 surface coating pretreatment

[0073] The surfaces of the NdFeB magnet 2 perpendicular to and parallel to the C-axis of the orientation are sequentially subjected to sandpaper grinding, polishing, alcohol ultrasonic cleaning and drying. Figure 2 The coating deposition device shown in FIG. 1 is used to deposit a coating containing heavy rare earth elements and a coating containing Co elements. The NdFeB magnet 2 is placed in the Figure 3 The NdFeB magnet 2 is fixed with screws 03 into the circular through hole 02 of the coating fixture shown in FIG. Figure 2 On the workpiece holder 3 in the coating deposition device shown.

[0074] S102, Glow cleaning of the surface of NdFeB magnet 2 perpendicular to the orientation C axis

[0075] Pump the vacuum chamber 1 to 3*10 -3Pa; Ar gas is introduced and the gas flow rate is adjusted to achieve a vacuum level of 1.2 Pa in the vacuum chamber 1; a negative bias voltage is applied to the workpiece holder 3 via the bias power supply 16, and the voltage parameters and cleaning time are set to complete the glow cleaning of the surface of the NdFeB magnet 2 perpendicular to the oriented C axis. The specific parameter settings of the vacuum chamber 1 are: voltage value of -450 V, frequency of 40 kHz, duty cycle of 60%, and cleaning time of 15 minutes.

[0076] S103, Deposition of coating containing heavy rare earth elements

[0077] The Ar gas flow rate is reduced to a pressure of 0.55 Pa in the vacuum chamber 1, and the workpiece holder 3 is activated for rotation. The first magnetron sputtering power supply 10, the sixth magnetron sputtering power supply 15, and the second magnetron sputtering power supply 11 are activated to co-sputter the heavy rare earth element target 4 (a Tb target), the first auxiliary element target 5 (a Mg target), and the fourth auxiliary element target 9 (a Pr target). A negative bias power supply 16 is applied to the workpiece holder 3, and a heavy rare earth element coating is subsequently deposited on the surface of the NdFeB magnet 2 perpendicular to the orientation C-axis. Among them, the rotation speed of the workpiece holder 3 is: 5rpm; the sputtering power density of the first magnetron sputtering power supply 10, the sixth magnetron sputtering power supply 15 and the second magnetron sputtering power supply 11 are 10w / cm2, 5w / cm2 and 3w / cm2 respectively, and the pulse frequency and duty cycle of the three are 60kHz and 80%; the voltage of the bias power supply 16 is -100V, the pulse frequency is 60kHz, the duty cycle is 80%, and the deposition time is 55min.

[0078] S104, Replace the coating fixture

[0079] After the NdFeB magnet 2 is cooled to room temperature, the sample is taken out from the vacuum chamber and the TbMgPr coating is deposited. Figure 4 The coating fixture shown (between the stainless steel support 04 and the stainless steel pressing block 01) is placed as shown in FIG. Figure 2 On the workpiece stand 3 of the coating deposition device shown.

[0080] S105, Glow cleaning of the surface of NdFeB magnet 2 parallel to the orientation C axis

[0081] Pump the vacuum chamber 1 to 3*10 -3 Pa; Ar gas is introduced and the gas flow rate is adjusted to achieve a vacuum level of 1.2 Pa in the vacuum chamber 1; a negative bias voltage is applied to the workpiece holder 3 via the bias power supply 16, and the voltage parameters and cleaning time are set to complete the glow cleaning of the surface of the NdFeB magnet 2 parallel to the orientation C axis. The specific parameter settings of the vacuum chamber 1 are: voltage value of -450V, frequency of 40kHz, duty cycle of 60%, and cleaning time of 15 minutes.

[0082] S106, Co-containing coating deposition

[0083] Reduce the Ar gas flow rate to make the air pressure of the vacuum chamber 1 0.6 Pa, and start the rotation of the workpiece holder 3. Turn on the fourth magnetron sputtering power supply 13, the fifth magnetron sputtering power supply 14 and the third magnetron sputtering power supply 12 to co-sputter the Co element target 7, the second auxiliary element target 6 (Gd target) and the third auxiliary element target 8 (Cu target). Load the workpiece holder 3 with a negative bias power supply 16, and at the same time turn on the DC pulse power supply 18 and start the anode layer ion source 17 to increase the ion density and the amount of Co element sputtering, thereby avoiding the drop in the sputtering magnetic field due to the high magnetic permeability of the Co element target 7. Subsequently, the Co element coating is deposited on the surface of the NdFeB magnet 2 parallel to the oriented C axis. Among them, the rotation speed of the workpiece holder 3 is: 5rpm; the sputtering powers of the fourth magnetron sputtering power supply 13, the fifth magnetron sputtering power supply 14, and the third magnetron sputtering power supply 12 are 11w / cm2, 5w / cm2, and 2w / cm2 respectively, and the pulse frequency and duty cycle of the three are 50kHz and 60%; the parameters of the bias power supply 16 are: bias is -150V, pulse frequency is 50kHz, and duty cycle is 60%; parameters of the DC pulse power supply 18 are: power 3kW, frequency 80kHz, duty cycle 50%; deposition time is 70min.

[0084] S107, vacuum heat treatment

[0085] After the NdFeB magnet 2 cools to room temperature, the sample is removed from the vacuum chamber, coated with TbMgPr and CoGdCu, and then placed in a vacuum diffusion furnace for heat treatment. Heat treatment parameters include: diffusion temperature of 900°C for 7.5 hours; annealing temperature of 500°C for 4 hours; and vacuum degree of 5*10-3Pa.

[0086] S108. After the NdFeB magnet 2 cools to room temperature, take out the sample and perform magnetic property testing.

[0087] The magnetic properties of the diffused NdFeB magnet 2 were tested using a pulsed magnetic field intensity meter. The demagnetization curve, remanence, coercive force and remanence temperature coefficient were as follows: Figure 6 and as shown in Table 2. Compared with the magnetic properties of the substrate (such as Figure 5 and Table 1), under the premise of no significant decrease in remanence, the coercivity of diffused NdFeB magnet 2 increased by 5.44kOe and the remanence temperature coefficient decreased significantly by 0.007% / ℃, which confirmed that this method can achieve the synchronous optimization of the coercivity and remanence temperature coefficient of sintered NdFeB magnets.

[0088] Table 2 Remanence, coercivity and remanence temperature coefficient of diffused NdFeB magnet 2 in Example 1

[0089] <![CDATA[Residual magnetic flux density B r (20 °C)]]> <![CDATA[Coercive force H cj (20 °C)]]> <![CDATA[Remanence temperature coefficient | α(B r ) | (20 °C - 180 °C)]]> 13.36kGs 27.27kOe 0.130％ / ℃

[0090] Example 2:

[0091] In this embodiment 2, R1 in the heavy rare earth element coating R1-A1 is the heavy rare earth element Tb, and A1 is the element Al and Nd, corresponding to Figure 2 The first auxiliary element target 5 and the fourth auxiliary element target 9. In the Co-containing element coating Co-A2, A2 is the element Zn and Mg, corresponding to Figure 2 The second auxiliary element target 6 and the third auxiliary element target 8 are respectively deposited on the surface of the NdFeB magnet 2 perpendicular to and parallel to the orientation C axis by magnetron sputtering, and then vacuum heat treatment is performed.

[0092] The specific processing process is as follows:

[0093] S201, Pretreatment of Surface Coating of Sintered NdFeB Magnets

[0094] The surfaces of the NdFeB magnet 2 perpendicular to and parallel to the C-axis of the orientation are sequentially subjected to sandpaper grinding, polishing, alcohol ultrasonic cleaning and drying. Figure 2 The coating deposition device shown in FIG. 1 is used to deposit a coating containing heavy rare earth elements and a coating containing Co elements. The NdFeB magnet 2 is placed in the Figure 3 The NdFeB magnet 2 is fixed with screws 03 into the circular through hole 02 of the coating fixture shown in FIG. Figure 2 On the workpiece holder 3 in the coating deposition device shown.

[0095] S202, glow cleaning of the surface of NdFeB magnet 2 perpendicular to the orientation C axis

[0096] Pump the vacuum chamber 1 to 2*10 -3 Pa; Ar gas is introduced and the gas flow rate is adjusted to achieve a vacuum level of 2 Pa in the vacuum chamber 1; a negative bias voltage is applied to the workpiece holder 3 via the bias power supply 16, and the voltage parameters and cleaning time are set to complete the glow cleaning of the surface of the NdFeB magnet 2 perpendicular to the oriented C axis. Specific parameters of the vacuum chamber 1 are: voltage value of -500 V, frequency of 80 kHz, duty cycle of 80%, and cleaning time of 20 minutes.

[0097] S203, heavy rare earth element coating deposition

[0098] The Ar gas flow rate is reduced to a pressure of 0.7 Pa in the vacuum chamber 1, and the workpiece holder 3 is started to rotate. The first magnetron sputtering power supply 10, the sixth magnetron sputtering power supply 15, and the second magnetron sputtering power supply 11 are turned on to co-sputter the heavy rare earth element target 4 (a Tb target), the first auxiliary element target 5 (an Al target), and the fourth auxiliary element target 9 (an Nd target). A negative bias power supply 16 is applied to the workpiece holder 3, and a heavy rare earth element coating is then deposited on the surface of the NdFeB magnet 2 perpendicular to the orientation C-axis. The rotation speed of the workpiece holder 3 is 15 rpm; the sputtering power densities of the first magnetron sputtering power supply 10, the sixth magnetron sputtering power supply 15 and the second magnetron sputtering power supply 11 are 11 w / cm2, 2 w / cm2 and 4 w / cm2 respectively, and the pulse frequencies and duty cycles of the three are 90 kHz and 70%; the voltage of the bias power supply 16 is -150 V, the pulse frequency is 90 kHz, the duty cycle is 70%, and the deposition time is 60 min.

[0099] S204, Replace the coating fixture

[0100] After the NdFeB magnet 2 is cooled to room temperature, the sample is taken out from the vacuum chamber and the TbAlNd coating is deposited. Figure 4 The coating fixture shown (between the stainless steel support 04 and the stainless steel pressing block 01) is placed as shown in FIG. Figure 2 On the workpiece stand 3 of the coating deposition device shown.

[0101] S205, Glow cleaning of the surface of NdFeB magnet 2 parallel to the orientation C axis

[0102] Pump the vacuum chamber 1 to 2*10 -3 Pa; Ar gas is introduced and the gas flow rate is adjusted to achieve a vacuum level of 2 Pa in the vacuum chamber 1; a negative bias voltage is applied to the workpiece holder 3 via the bias power supply 16, and the voltage parameters and cleaning time are set to complete the glow cleaning of the surface of the NdFeB magnet 2 parallel to the orientation C axis. Specific parameters of the vacuum chamber 1 are: voltage value of -500 V, frequency of 80 kHz, duty cycle of 80%, and cleaning time of 20 minutes.

[0103] S206, Co-containing coating deposition

[0104] Reduce the Ar gas flow rate to 0.8 Pa, and start the rotation of the workpiece holder 3. Turn on the fourth magnetron sputtering power supply 13, the fifth magnetron sputtering power supply 14, and the third magnetron sputtering power supply 12 to co-sputter the Co element target 7, the second auxiliary element target 6 (a Zn target is selected), and the third auxiliary element target 8 (a Mg target is selected). Load the workpiece holder 3 with a negative bias voltage, and at the same time turn on the DC pulse power supply 18 and the anode layer ion source 17 to increase the ion density and the amount of Co element sputtering, thereby avoiding the drop in the sputtering magnetic field due to the high magnetic permeability of the Co element target 7. Subsequently, the Co element coating is deposited on the surface of the NdFeB magnet 2 parallel to the oriented C axis. The workpiece holder rotation speed is 15 rpm; the sputtering powers of the fourth magnetron sputtering power supply 13, the fifth magnetron sputtering power supply 14, and the third magnetron sputtering power supply 12 are 9 w / cm2, 3 w / cm2, and 3 w / cm2 respectively, and the pulse frequencies and duty cycles of the three are 150 kHz and 50%; the parameters of the bias power supply 16 are: bias voltage is -50 V, pulse frequency is 60 kHz, and duty cycle is 80%; the parameters of the DC pulse power supply 18 are: power is 5 kW, frequency is 120 kHz, and duty cycle is 60%; the deposition time is 80 min.

[0105] S207, vacuum heat treatment

[0106] After cooling the NdFeB magnet 2 to room temperature, the sample was removed from the vacuum chamber and coated with TbAlNd and CoZnMg. It was then placed in a vacuum diffusion furnace for heat treatment. Heat treatment parameters included a diffusion temperature of 870°C for 10 hours, an annealing temperature of 480°C for 5 hours, and a vacuum of 7 × 10-3 Pa.

[0107] S208. After the NdFeB magnet 2 cools to room temperature, take out the sample and perform magnetic property testing.

[0108] The magnetic properties of the diffused NdFeB magnet 2 were tested using a pulsed magnetic field intensity meter. The demagnetization curve, remanence, coercive force and remanence temperature coefficient were as follows: Figure 7 and as shown in Table 3. Compared with the magnetic properties of the substrate (such as Figure 5 and Table 1), under the premise of no significant decrease in remanence, the coercivity of diffused NdFeB magnet 2 increased by 6.31kOe and the remanence temperature coefficient decreased significantly by 0.004% / °C, confirming that this method can achieve the synchronous optimization of the coercivity and remanence temperature coefficient of sintered NdFeB magnets.

[0109] Table 3 Remanence, coercivity and remanence temperature coefficient of diffused NdFeB magnet 2 in Example 2

[0110] <![CDATA[Residual magnetic flux density B r (at 20°C)]]> <![CDATA[Coercive force H cj (20 °C)]]> <![CDATA[Remanence temperature coefficient | α(B r ) | (20 °C - 180 °C)]]> 13.35kGs 28.14kOe 0.133％ / ℃

[0111] Example 3:

[0112] In this embodiment 3, R1 of the heavy rare earth element coating R1-A1 is the heavy rare earth element Tb, and A1 is the element Zn and Cu, corresponding to Figure 2 The first auxiliary element target 5 and the fourth auxiliary element target 9. A2 in the Co-containing element coating Co-A2 is the element Gd and Al, corresponding to Figure 2 The second auxiliary element target 6 and the third auxiliary element target 8 are respectively deposited on the surface of the NdFeB magnet 2 perpendicular to and parallel to the orientation C axis by magnetron sputtering, and then vacuum heat treatment is performed.

[0113] The specific processing process is as follows:

[0114] S301, Pretreatment of Surface Coating of Sintered NdFeB Magnets

[0115] The surfaces of the NdFeB magnet 2 perpendicular to and parallel to the C-axis of the orientation are sequentially subjected to sandpaper grinding, polishing, alcohol ultrasonic cleaning and drying. Figure 2 The device shown in the figure is used to deposit the coating containing heavy rare earth elements and the coating containing Co elements. Figure 3 The coating fixture is inserted into the through hole 02 of the coating fixture and the NdFeB magnet 2 is fixed with screws 03. The coating fixture is then placed as shown in FIG. Figure 2 On the workpiece holder 3 in the coating deposition device shown.

[0116] S302, glow cleaning of the surface of the NdFeB magnet 2 perpendicular to the orientation C axis

[0117] Pump the vacuum chamber 1 to 4.5*10 -3 Pa; Ar gas is introduced and the gas flow rate is adjusted to achieve a vacuum level of 3 Pa in the vacuum chamber 1; a negative bias voltage is applied to the workpiece holder 3 via the bias power supply 16, and the voltage parameters and cleaning time are set to complete the glow cleaning of the surface of the NdFeB magnet 2 perpendicular to the oriented C axis. The specific parameter settings of the vacuum chamber 1 are: voltage value of -600 V, frequency of 30 kHz, duty cycle of 50%, and cleaning time of 30 minutes.

[0118] S303, heavy rare earth element coating deposition

[0119] The Ar gas flow rate is reduced to a pressure of 0.9 Pa in the vacuum chamber 1, and the workpiece holder 3 is activated for rotation. The first magnetron sputtering power supply 10, the sixth magnetron sputtering power supply 15, and the second magnetron sputtering power supply 11 are activated to co-sputter the heavy rare earth element target 4 (a Tb target), the first auxiliary element target 5 (a Zn target), and the fourth auxiliary element target 9 (a Cu target). A negative bias power supply 16 is applied to the workpiece holder 3, and a heavy rare earth element coating is subsequently deposited on the surface of the NdFeB magnet 2 perpendicular to the orientation C-axis. The rotation speed of the workpiece holder 3 is 10 rpm; the sputtering power densities of the first magnetron sputtering power supply 10, the sixth magnetron sputtering power supply 15 and the second magnetron sputtering power supply 11 are 12 w / cm2, 3 w / cm2 and 6 w / cm2 respectively, and the pulse frequencies and duty cycles of the three are 120 kHz and 80%; the voltage of the bias power supply 16 is -100 V, the pulse frequency is 30 kHz, the duty cycle is 50%, and the deposition time is 35 min.

[0120] S304, Replace the coating fixture

[0121] After the NdFeB magnet 2 is cooled to room temperature, the sample is taken out from the vacuum chamber and the TbZnCu coating is deposited. Figure 4 The coating fixture shown (between the stainless steel support 04 and the stainless steel pressing block 01) is placed as shown in FIG. Figure 2 On the workpiece stand 3 of the coating deposition device shown.

[0122] S305, glow cleaning of the surface of the NdFeB magnet 2 parallel to the orientation C axis

[0123] Pump the vacuum chamber 1 to 4.5*10 -3 Pa; Ar gas is introduced and the gas flow rate is adjusted to achieve a vacuum level of 3 Pa in the vacuum chamber 1; a negative bias voltage is applied to the workpiece holder 3 via the bias power supply 16, and the voltage parameters and cleaning time are set to complete the glow cleaning of the surface of the NdFeB magnet 2 parallel to the oriented C axis. Specific parameters of the vacuum chamber 1 are: voltage value of -600 V, frequency of 30 kHz, duty cycle of 50%, and cleaning time of 30 minutes.

[0124] S306, Co-containing coating deposition

[0125] Reduce the Ar gas flow rate to make the air pressure of the vacuum chamber 1 0.5 Pa, and start the workpiece holder 3 to rotate. Turn on the fourth magnetron sputtering power supply 13, the fifth magnetron sputtering power supply 14 and the third magnetron sputtering power supply 12, and co-sputter the Co element target 7, the second auxiliary element target 6 (Gd target) and the third auxiliary element target 8 (Al target). Load the workpiece holder 3 with a negative bias power supply 16, and at the same time turn on the DC pulse power supply 18 and start the anode layer ion source 17 to increase the ion density and the amount of Co element sputtering, thereby avoiding the drop in the sputtering magnetic field due to the high magnetic permeability of the Co element target 7. Subsequently, the Co element coating is deposited on the surface of the NdFeB magnet 2 parallel to the oriented C axis. The rotation speed of the workpiece holder 3 is 10 rpm; the sputtering powers of the fourth magnetron sputtering power supply 13, the fifth magnetron sputtering power supply 14, and the third magnetron sputtering power supply 12 are 11 w / cm2, 1 w / cm2, and 4 w / cm2 respectively, and the pulse frequencies and duty cycles of the three are 120 kHz and 60%; the parameters of the bias power supply 16 are -75 V bias, 80 kHz pulse frequency, and 80% duty cycle; the parameters of the DC pulse power supply 18 are 2 kW power, 150 kHz frequency, and 80% duty cycle; and the deposition time is 70 min.

[0126] S307, vacuum heat treatment

[0127] After the NdFeB magnet 2 cools to room temperature, the sample is removed from the vacuum chamber and coated with TbZnCu and CoGdAl. It is then placed in a vacuum diffusion furnace for heat treatment. Heat treatment parameters are: diffusion temperature of 930°C for 6 hours; annealing temperature of 490°C for 6 hours; and vacuum degree of 3*10-3Pa.

[0128] S308 , after the NdFeB magnet 2 is cooled to room temperature, the sample is taken out and magnetic properties are tested.

[0129] The magnetic properties of the diffused magnet were tested using a pulsed magnetic field intensity meter. The demagnetization curve, remanence, coercive force and remanence temperature coefficient were as follows: Figure 8 and as shown in Table 4. Compared with the magnetic properties of the substrate (such as Figure 5 and Table 1), under the premise of no significant decrease in remanence, the coercivity of diffused NdFeB magnet 2 increased by 6.3kOe and the remanence temperature coefficient decreased significantly by 0.006% / °C, confirming that this method can achieve the synchronous optimization of the coercivity and remanence temperature coefficient of sintered NdFeB magnets.

[0130] Table 4 Remanence, coercivity and remanence temperature coefficient of diffused NdFeB magnet 2 in Example 3

[0131] <![CDATA[Residual magnetism B r (20 °C)]]> <![CDATA[Coercive force H cj (20 °C)]]> <![CDATA[Temperature coefficient of remanence | α(B r ) | (20 °C - 180 °C)]]> 13.58kGs 28.13kOe 0.131％ / ℃

[0132] The invention has a reasonable concept, can realize the synchronous optimization of the coercive force and the remanence temperature coefficient of the sintered NdFeB magnet, and is suitable for promotion and application.

[0133] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A grain boundary diffusion method for simultaneously optimizing the coercivity and remanence temperature coefficient of sintered NdFeB magnets, characterized by: First, a coating R1-A1 containing a heavy rare earth element is prepared on the surface of a NdFeB magnet perpendicular to the orientation C axis; R1 is at least one of Tb and Dy, and A1 is at least two of Al, Mg, Zn, Cu, Pr, and Nd; then, a coating Co-A2 containing a Co element is prepared on the surface of the NdFeB magnet parallel to the orientation C axis; A2 is at least two of Gd, Nd, Al, Mg, Zn, and Cu; after the preparation of the coating R1-A1 containing a heavy rare earth element and the coating Co-A2 containing a Co element, the NdFeB magnets perpendicular to and parallel to the orientation C axis are heat treated.

2. The grain boundary diffusion method for simultaneously optimizing the coercive force and remanence temperature coefficient of sintered NdFeB magnets according to claim 1, characterized in that: The method specifically comprises the following steps: 1) Surface coating pretreatment of sintered NdFeB magnets The surfaces of the NdFeB magnet perpendicular to and parallel to the orientation C axis are sequentially subjected to sandpaper grinding, polishing, alcohol ultrasonic cleaning and drying treatments; a coating deposition device is used to deposit a heavy rare earth element coating and a Co element coating, the coating deposition device comprising a vacuum chamber, a workpiece holder matched and arranged in the center of the vacuum chamber, a heavy rare earth element target, a first auxiliary element target, a second auxiliary element target, a Co element target, a third auxiliary element target, a fourth auxiliary element target and an anode layer ion source matched and arranged on the circumference of the vacuum chamber; the heavy rare earth element target is connected to a first magnetron sputtering power supply; the fourth auxiliary element target is connected to a second magnetron sputtering power supply A magnetron sputtering power supply is connected to the third auxiliary element target, the Co element target is connected to the fourth magnetron sputtering power supply, the second auxiliary element target is connected to the fifth magnetron sputtering power supply, and the first auxiliary element target is connected to the sixth magnetron sputtering power supply; an NdFeB magnet is installed in a coating fixture, the fixture includes a stainless steel base, a stainless steel pillar matched and mounted in the center of the upper part of the stainless steel base, and a stainless steel pressing block matched and mounted on the upper part of the stainless steel pillar; a circular through hole is matched on the stainless steel pressing block; specifically, the NdFeB magnet is installed in the circular through hole of the fixture and fixed with a screw, and then the coating fixture is placed on the workpiece holder; 2) Glow cleaning of NdFeB magnet surface perpendicular to the orientation C axis Pump the vacuum chamber to 5*10 -3 Pa or less; then, Ar gas is introduced into the vacuum chamber and the gas flow rate is adjusted to make the vacuum degree of the vacuum chamber 1Pa to 3Pa; a negative bias power supply is applied to the workpiece holder through the bias power supply, and the voltage parameters and cleaning time are set to complete the glow cleaning of the NdFeB magnet surface perpendicular to the orientation C axis; 3) Deposition of coatings containing heavy rare earth elements The Ar gas flow rate is reduced to adjust the pressure of the vacuum chamber to 0.5 Pa-1 Pa, and the rotation of the workpiece holder is started; the first magnetron sputtering power supply, the sixth magnetron sputtering power supply, and the second magnetron sputtering power supply are turned on to co-sputter the heavy rare earth element target, the first auxiliary element target, and the fourth auxiliary element target; a negative bias power supply is applied to the workpiece holder, and then a heavy rare earth element-containing coating is deposited on the surface of the NdFeB magnet perpendicular to the orientation C axis; 4) Replace the coating fixture After the NdFeB magnet cools to room temperature, the sample is removed from the vacuum chamber and the heavy rare earth element coating R1-A1 is deposited. The NdFeB magnet is then placed in a coating fixture and placed on a workpiece holder. 5) Glow cleaning of NdFeB magnet surface parallel to the orientation C axis Pump the vacuum chamber of the coating deposition device to 5*10 -3 Pa or less; then introduce Ar gas and adjust the gas flow rate to make the vacuum degree of the vacuum chamber 1Pa ~ 3Pa; load the workpiece holder with a negative bias power supply through the bias power supply, and set the voltage parameters and cleaning time to complete the glow cleaning of the NdFeB magnet surface parallel to the orientation C axis; 6) Co-containing coating deposition The Ar gas flow rate is reduced to make the gas pressure of the vacuum chamber 0.5Pa-1Pa, and the rotation of the workpiece holder is started; the fourth magnetron sputtering power supply, the fifth magnetron sputtering power supply and the third magnetron sputtering power supply are turned on to co-sputter the Co element target, the second auxiliary element target and the third auxiliary element target; a negative bias power supply is applied to the workpiece holder, and a DC pulse power supply is turned on at the same time to start the anode layer ion source, increase the ion density, and increase the sputtering amount of the Co element, thereby avoiding a decrease in the sputtering magnetic field due to the high magnetic permeability of the Co element target; and then a Co element-containing coating is deposited on the surface of the NdFeB magnet parallel to the orientation C axis; 7) Vacuum heat treatment After the NdFeB magnet cools to room temperature, the sample is removed from the vacuum chamber, and the deposition of the heavy rare earth element coating R1-A1 and the Co element coating Co-A2 is completed. The sample is then placed in a vacuum diffusion furnace for heat treatment. 8) After the NdFeB magnet cools to room temperature, take out the sample and perform magnetic property testing.

3. The grain boundary diffusion method for simultaneously optimizing the coercive force and remanence temperature coefficient of sintered NdFeB magnets according to claim 2, characterized in that: The specific parameter setting range of the vacuum chamber in step 2) is: voltage value -400V to -600V, frequency 20kHz to 100kHz, duty cycle 20% to 80%, and cleaning time 5min to 30min.

4. The grain boundary diffusion method for simultaneously optimizing the coercive force and remanence temperature coefficient of sintered NdFeB magnets according to claim 2, characterized in that: The heavy rare earth element target in step 3) contains at least one of Tb and Dy, the first auxiliary element target contains at least one of Al, Mg, Zn, Cu, Pr, and Nd, and the fourth auxiliary element target contains at least one of Al, Mg, Zn, Cu, Pr, and Nd, and the elements contained in the first auxiliary element target and the fourth auxiliary element target should not overlap.

5. The grain boundary diffusion method for simultaneously optimizing the coercive force and remanence temperature coefficient of sintered NdFeB magnets according to claim 2, characterized in that: The workpiece support speed range in step 3) is: 3-20 rpm; The parameter ranges of the first magnetron sputtering power supply, the sixth magnetron sputtering power supply, and the second magnetron sputtering power supply in step 3) are: sputtering power density is 1w / cm2-12w / cm2, pulse frequency is 30kHz-150kHz, and duty cycle is 20%-80%; The specific parameter range of the negative bias power supply in step 3) is: bias voltage of -30V to -150V, pulse frequency of 20kHz to 100kHz, and duty cycle of 20% to 80%; In the step 3), the deposition time of the heavy rare earth element-containing coating on the surface of the NdFeB magnet perpendicular to the oriented C axis is 30 min to 60 min.

6. The grain boundary diffusion method for simultaneously optimizing the coercive force and remanence temperature coefficient of sintered NdFeB magnets according to claim 2, characterized in that: In the step 4), the NdFeB magnet is installed between the stainless steel support and the stainless steel pressing block of the coating fixture.

7. The grain boundary diffusion method for simultaneously optimizing the coercive force and remanence temperature coefficient of sintered NdFeB magnets according to claim 2, characterized in that: The second auxiliary element target in step 6) contains at least one of Gd, Nd, Al, Mg, Zn, and Cu, and the third auxiliary element target contains at least one of Gd, Nd, Al, Mg, Zn, and Cu, and the elements contained in the second auxiliary element target and the third auxiliary element target should not overlap.

8. The grain boundary diffusion method for simultaneously optimizing the coercive force and remanence temperature coefficient of sintered NdFeB magnets according to claim 2, characterized in that: The rotation speed range of the workpiece holder in step 6) is: 1-20 rpm; In step 6), the parameter ranges of the fourth magnetron sputtering power supply, the fifth magnetron sputtering power supply, and the third magnetron sputtering power supply are: sputtering power density of 1w / cm2-12w / cm2, pulse frequency of 30kHz-150kHz, and duty cycle of 20%-80%; In step 6), the negative bias power supply parameter range is: bias voltage is -20V to -250V, pulse frequency is 20kHz to 100kHz, and duty cycle is 20% to 80%; the DC pulse power supply parameter range is: power 2kW to 5kW, frequency is 40kHz to 150kHz, and duty cycle is 20% to 80%; In the step 6), the Co-containing coating is deposited on the surface of the NdFeB magnet parallel to the oriented C axis for a deposition time of 30 min to 90 min.

9. The grain boundary diffusion method for simultaneously optimizing the coercive force and remanence temperature coefficient of sintered NdFeB magnets according to claim 2, characterized in that: The heat treatment in step 7) includes high-temperature thermal diffusion and low-temperature annealing; the parameter range of the high-temperature thermal diffusion is: diffusion temperature 800°C-950°C, and time is 5-10 hours; the parameter range of the low-temperature annealing is: annealing temperature 450°C-520°C, and time is 4-6 hours; the vacuum degree of the vacuum chamber in step 7) is less than 10-2Pa.

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