Grain boundary diffusion method for synchronously optimizing coercive force and residual magnetism temperature coefficient of sintered neodymium-iron-boron magnet

Abstract

The invention provides a grain boundary diffusion method for synchronously optimizing the coercive force and the remanence temperature coefficient of a sintered neodymium-iron-boron magnet. The grain boundary diffusion method comprises the steps that firstly, a coating R1-A1 containing heavy rare earth elements is prepared 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 A1, Mg, Zn, Cu, Pr and Nd; 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, A < l >, Mg, Zn and Cu; after the coating R1-A1 containing the heavy rare earth element and the coating Co-A2 containing the Co element are prepared, the NdFeB magnet perpendicular to and parallel to the orientation C axis is subjected to heat treatment. The method is reasonable in conception, can realize synchronous optimization of the coercive force and the residual magnetism temperature coefficient of the sintered neodymium-iron-boron magnet, and is suitable for popularization and application.

Description

Technical Field

[0001] The invention belongs to the field of rare earth permanent magnet material surface engineering, and specifically 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 trend of the development of high-performance rare earth permanent magnet drive motors. As the core material for energy conversion in rare earth permanent magnet motors, neodymium iron boron (NdFeB) magnets have excellent magnetic properties such as ultra-high remanence Br and magnetic energy product (BH) max, showing great advantages in improving the power density and speed of motors. Among them, the remanence Br of the magnet is the decisive factor affecting the power density and speed of the motor, while the intrinsic coercive force Hcj represents the ability of the magnet to resist external magnetic field disturbances, which is inseparable from whether the motor can operate stably. However, the intrinsic coercive force Hcj of NdFeB magnets is much lower than its magnetocrystalline anisotropy field HA, and its ability to resist external magnetic field disturbances is very limited. On the other hand, the increase in motor power density and speed brings more serious eddy current losses, causing the internal ambient temperature of the motor to continue to increase. The main phase of NdFeB magnets, Nd2Fe14B compounds, has a low Curie temperature Tc, and the increase in temperature will cause a significant decrease in the Br and Hcj of the magnets. The deterioration of the former cannot provide the motor with 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 surface of the main phase. 14 B shell, that is, "shell-core" structure, to improve the coercivity, thereby compensating for the loss of coercivity at high temperature. 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 (727℃). Therefore, adding an appropriate amount of Co element to the heavy rare earth diffusion source is currently a commonly used 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 oriented 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 Co element from entering the interior of the grain. The above two factors cause a large amount of Co element to be enriched in the grain boundary phase, and it is unable to enter the interior of the grain to form enough Nd2Co 14 B compounds tend to form 1:2 type Laves soft magnetic phase. Therefore, heavy rare earth + Co co-diffusion often fails to improve the coercivity and remanence temperature stability simultaneously, but will deteriorate the magnetic properties. Therefore, it is urgent to develop a new grain boundary diffusion technology for heavy rare earth + Co co-diffusion to achieve the purpose of simultaneously optimizing the coercivity and remanence temperature coefficient of sintered NdFeB magnets. Summary of the invention

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

[0006] To solve the above technical problems, the present invention provides a grain boundary diffusion method for synchronously optimizing the coercive force and remanence temperature coefficient of a sintered NdFeB magnet, which comprises the following steps: firstly preparing a coating R1-A1 containing a heavy rare earth element on the surface of a NdFeB magnet perpendicular to an oriented 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; and then preparing a coating Co-A2 containing a Co element on the surface of a NdFeB magnet parallel to the oriented 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 magnet perpendicular to and parallel to the oriented C axis is subjected to heat treatment.

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

[0008] 1) Surface treatment of sintered NdFeB magnets before coating

[0009] The surfaces of the NdFeB magnets perpendicular to and parallel to the oriented 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 cavity, a workpiece rack matchedly arranged in the center of the vacuum cavity, 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 matchedly arranged on the circumference of the vacuum cavity; 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; The target material of the second auxiliary element is connected to the fifth magnetron sputtering power supply, the target material of the first auxiliary element is connected to the sixth magnetron sputtering power supply; the NdFeB magnet is installed in the coating fixture, the fixture includes a stainless steel base, a stainless steel pillar matched and installed in the center of the upper part of the stainless steel base, and a stainless steel pressing block matched and installed on the upper part of the stainless steel pillar; the stainless steel pressing block is matched and provided with a circular through hole; 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 rack;

[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 a bias power supply, and voltage parameters and cleaning time are set to complete the glow cleaning of the surface of the NdFeB magnet perpendicular to the oriented C axis;

[0012] 3) Heavy rare earth element coating deposition

[0013] The Ar gas flow rate is reduced to make the gas pressure of the vacuum chamber 0.5Pa-1Pa, and the workpiece holder is started to rotate; 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 loaded on 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 is cooled to room temperature, the sample is taken out from the vacuum chamber, and the heavy rare earth element coating R1-A1 is deposited; then the NdFeB magnet is loaded into the coating fixture and placed on the 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 to 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 oriented C axis;

[0018] 6) Coating deposition containing Co element

[0019] The Ar gas flow rate is reduced to make the gas pressure of the vacuum chamber 0.5Pa-1Pa, and the workpiece holder is started to rotate; 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 loaded on 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, increase the sputtering amount of the Co element, and avoid the sputtering magnetic field drop caused by the high magnetic permeability of the Co element target; then the Co element coating is deposited on the surface of the NdFeB magnet parallel to the oriented C axis;

[0020] 7) Vacuum heat treatment

[0021] After the NdFeB magnet is cooled to room temperature, the sample is taken out 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, and then the sample is placed in a vacuum diffusion furnace for heat treatment;

[0022] 8) After the NdFeB magnet has cooled 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: 3-20rpm;

[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 the 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 is -30V to -150V, pulse frequency is 20kHz to 100kHz, and duty cycle is 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-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, 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: 1-20rpm;

[0032] In the 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 is 1w / cm2-12w / cm2, pulse frequency is 30kHz-150kHz, and duty cycle is 20%-80%;

[0033] In the 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 synchronously 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 cavity 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 grain boundary diffusion method for simultaneously optimizing the coercive force and remanent temperature coefficient of sintered NdFeB magnets of the present invention is rationally conceived. Different from the prior art, the present invention does not deposit heavy rare earth elements and Co elements simultaneously on the magnet surface perpendicular to the oriented C axis, but separates the two, and proposes a new method for depositing a heavy rare earth element coating and a Co element coating on the magnet surface perpendicular to and parallel to the oriented C axis, respectively. The present invention is based on the anisotropy of the crystal structure of the Nd2Fe14B compound. Compared with the diffusion perpendicular to the oriented C axis, when the heavy rare earth elements diffuse parallel to the oriented C axis, the heavy rare earth elements replace Nd in Nd2Fe14B with a longer diffusion path, a larger diffusion activation energy and a lower diffusion coefficient. Therefore, the heavy rare earth elements are not prone to lattice diffusion, and only a heavy rare earth shell is formed on the surface of the main phase. More heavy rare earth elements enter the interior of the magnet along the grain boundary, the diffusion depth is increased, and the coercive force is further improved. When the Co element diffuses in the direction perpendicular to the oriented C axis, the Co element replaces the Fe element in Nd2Fe14B without being hindered by the Nd element, so 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 in the grain boundary phase, inducing the formation of more high Nd2Co14B compounds inside the magnet, and thus reducing the remanent magnetism temperature coefficient of the magnet. Based on the above two points, the simultaneous optimization of the coercive force and remanent magnetism temperature coefficient of the sintered NdFeB magnet is finally achieved.

[0038] In order to solve the problem that the high magnetic permeability of the Co element target causes the sputtering magnetic field to decrease, resulting in a small amount of Co element sputtering, the present invention proposes magnetron sputtering + auxiliary anode layer ion source to prepare a Co element coating, and excites high-density plasma through the anode layer ion source to increase the Ar ion concentration in the vacuum atmosphere, so that more Ar ions can sputter the Co element target. Based on this, even when the sputtering magnetic field is weakened, a high amount of Co element sputtering can still be obtained, ensuring the deposition rate of the Co element coating. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0040] Figure 1 Schematic diagram of the deposition of a coating containing heavy rare earth elements and a coating containing Co 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 It is a schematic structural diagram of a coating deposition device containing heavy rare earth elements and a coating containing Co element involved in the grain boundary diffusion method for simultaneously optimizing the coercive force and remanence temperature coefficient of a sintered NdFeB magnet of the present invention;

[0042] Figure 3 A schematic structural diagram of a coating fixture for depositing a coating on a magnet surface 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 of the present invention;

[0043] Figure 4 A schematic structural diagram of a coating fixture for depositing a coating on the surface of a magnet 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 of the present invention;

[0044] Figure 5 The 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 the sintered NdFeB magnet of the present invention;

[0045] Figure 6 The 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 The 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 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 in Example 3 of the present invention. DETAILED DESCRIPTION

[0048] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] The present invention is further explained below in conjunction with specific implementation modes.

[0050] like Figure 1 As shown, the grain boundary diffusion method for synchronously optimizing the coercive force and remanence temperature coefficient of sintered NdFeB magnets of the present invention comprises the following steps: firstly, a coating R1-A1 containing heavy rare earth elements is prepared on the surface of the NdFeB magnet 2 perpendicular to the oriented 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 oriented 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 oriented C-axis is heat treated.

[0051] The grain boundary diffusion method for synchronously 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 oriented 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 rack 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 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 the figure. Figure 3The coating fixture shown (the coating fixture includes a stainless steel base 05, a stainless steel pillar 04 matched and installed at the center of the upper part of the stainless steel base 05, and a stainless steel pressing block 01 matched and installed at the upper part of the stainless steel pillar 04; the stainless steel pressing block 01 is matched and provided with a plurality of circular through holes 02) is inserted into the through hole, and the NdFeB magnet 2 is fixed with screws 03, and 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; then Ar gas is introduced into the vacuum chamber 1 and the gas flow rate is adjusted so that the vacuum degree of the vacuum chamber 1 is 1Pa-3Pa; a negative bias power supply 16 is applied to the workpiece holder 3 through 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. Among them, the specific parameter setting range of the vacuum chamber 1 is: voltage value -400V--600V, frequency 20kHz-100kHz, duty cycle 20%-80%, cleaning time 5min-30min.

[0056] S003, Heavy rare earth element coating deposition

[0057] The Ar gas flow rate is reduced to make the gas pressure of the vacuum chamber 1 0.5Pa-1Pa, 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 loaded on the workpiece holder 3, and then the heavy rare earth element coating is deposited on the surface of the NdFeB magnet 2 perpendicular to the oriented C axis. Among them, the elements contained in the aforementioned heavy rare earth element target 4 are at least one of Tb and Dy, the elements contained in the first auxiliary element target 5 are at least one of Al, Mg, Zn, Cu, Pr, and Nd, and the elements contained in the fourth auxiliary element target 9 are at least one of Al, Mg, Zn, Cu, Pr, and Nd, and the elements contained in the first auxiliary element target 5 and the fourth auxiliary element target 9 should not overlap. The rotation 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 is cooled to room temperature, the sample is taken out from the vacuum chamber 1, and the heavy rare earth element coating deposition R1-A1 is completed; then the NdFeB magnet 2 is loaded into the coating fixture (specifically, the NdFeB magnet 2 is loaded between the stainless steel support 04 and the stainless steel block 01 of the coating fixture), and placed on the workpiece rack 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; load the workpiece holder 3 with a negative bias power supply 16 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 oriented 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, and 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 turn on the DC pulse power supply 18 at the same time, start the anode layer ion source 17, increase the ion density, increase the sputtering amount of the Co element, and avoid the sputtering magnetic field drop caused by 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 second auxiliary element target 6 contains at least one of Gd, Nd, Al, Mg, Zn and Cu, and the third auxiliary element target 8 contains at least one of Gd, Nd, A l, at least one of Mg, Zn, and Cu, 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 oriented C axis for a deposition time of 30min-90min.

[0064] S007, vacuum heat treatment

[0065] After the NdFeB magnet 2 is cooled to room temperature, the sample is taken out of the vacuum chamber, and the deposition of the heavy rare earth element coating R1-A1 and the Co element coating Co-A2 is completed, and then placed in a vacuum diffusion furnace for heat treatment. The heat treatment includes high-temperature thermal diffusion and low-temperature annealing; the parameter range of the high-temperature thermal diffusion is: diffusion temperature 800℃-950℃, time is 5-10 hours; the parameter range of the low-temperature annealing is: annealing temperature 450℃-520℃, time is 4-6 hours; the vacuum degree of the vacuum chamber in step 7) is less than 10-2Pa.

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

[0067] The present invention is a method for simultaneously optimizing the coercive force and remanent temperature coefficient of a sintered NdFeB magnet by grain boundary diffusion. 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. A pulse magnetic field intensity meter is used to detect the magnetic properties of the NdFeB magnet 2. The demagnetization curve, remanence, coercive force, and remanent temperature coefficient are shown in FIG. Figure 5 The results are shown in Table 1. Then, the NdFeB magnets 2 from this batch were used as substrates to carry out the following three examples.

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

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

[0070] Embodiment 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 in the Co-containing element coating Co-A2 are the elements Gd and Cu, corresponding to Figure 2 The second auxiliary element target 6 and the third auxiliary element target 8 in the embodiment are respectively deposited with a heavy rare earth element coating and a Co element coating on the surface of the NdFeB magnet 2 perpendicular to and parallel to the oriented C axis by magnetron sputtering, 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 orientation C axis are sequentially subjected to sandpaper grinding, polishing, alcohol ultrasonic cleaning and drying. Figure 2 The coating deposition device shown in the figure deposits the coating containing heavy rare earth elements and the coating containing Co elements. Figure 3 The NdFeB magnet 2 is fixed with screws 03, and then the coating fixture is placed in the circular through hole 02 of the coating fixture. 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 make the vacuum degree of the vacuum chamber 1 to be 1.2Pa; a negative bias power supply 16 is applied to the workpiece holder 3 through 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 setting range of the vacuum chamber 1 is: voltage value -450V, frequency 40kHz, duty cycle 60%, cleaning time 15min.

[0076] S103, Heavy rare earth element coating deposition

[0077] The Ar gas flow rate is reduced to make the gas pressure of the vacuum chamber 1 0.55 Pa, 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 (Tb target), the first auxiliary element target 5 (Mg target) and the fourth auxiliary element target 9 (Pr target). A negative bias power supply 16 is loaded on the workpiece holder 3, and then the heavy rare earth element coating is deposited on the surface of the NdFeB magnet 2 perpendicular to the oriented 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 cools to room temperature, the sample is taken out of the vacuum chamber to complete the TbMgPr coating deposition. 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 make the vacuum degree of the vacuum chamber 1 to be 1.2Pa; a negative bias power supply 16 is applied to the workpiece holder 3 through 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. The specific parameter setting range of the vacuum chamber 1 is: voltage value -450V, frequency 40kHz, duty cycle 60%, cleaning time 15min.

[0082] S106, Co-containing coating deposition

[0083] Reduce the Ar gas flow rate to make the gas pressure of the vacuum chamber 1 0.6Pa, 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 (Cu target). Load the workpiece holder 3 with a negative bias power supply 16, turn on the DC pulse power supply 18 at the same time, start the anode layer ion source 17, increase the ion density, increase the sputtering amount of the Co element, and avoid the sputtering magnetic field drop caused by the high magnetic permeability of the Co element target 7. Then 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, the pulse frequency is 50kHz, and the duty cycle is 60%; the parameters of the DC pulse power supply 18 are: power 3kW, frequency 80kHz, duty cycle 50%; deposition time 70min.

[0084] S107, vacuum heat treatment

[0085] After the NdFeB magnet 2 is cooled to room temperature, the sample is taken out from the vacuum chamber, the TbMgPr coating and the CoGdCu coating are completed, and then it is placed in a vacuum diffusion furnace for heat treatment; heat treatment parameters: diffusion temperature is 900°C, time is 7.5 hours; annealing temperature is 500°C, time is 4 hours; vacuum degree is 5*10-3Pa.

[0086] S108, after the NdFeB magnet 2 is cooled 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 pulse 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 coercive force of diffused NdFeB magnet 2 increased by 5.44kOe and the remanent temperature coefficient decreased significantly by 0.007% / °C, which confirmed that this method can achieve the synchronous optimization of the coercive force and remanent 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 magnetism 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] Embodiment 2:

[0091] In this embodiment 2, R1 of 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 are the elements 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 oriented C axis by magnetron sputtering, and then vacuum heat treatment is performed.

[0092] The specific processing process is as follows:

[0093] S201, sintered NdFeB magnet surface coating pretreatment

[0094] 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. Figure 2 The coating deposition device shown in the figure deposits the coating containing heavy rare earth elements and the coating containing Co elements. Figure 3 The NdFeB magnet 2 is fixed with screws 03, and then the coating fixture is placed in the circular through hole 02 of the coating fixture. 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; introduce Ar gas and adjust the gas flow rate to make the vacuum degree of the vacuum chamber 1 2Pa; load the workpiece holder 3 with a negative bias power supply 16 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 perpendicular to the oriented C axis. The specific parameters of the vacuum chamber 1 are: voltage value -500V, frequency 80kHz, duty cycle 80%, cleaning time 20min.

[0097] S203, Heavy rare earth element coating deposition

[0098] The Ar gas flow rate is reduced to make the gas pressure of the vacuum chamber 1 0.7 Pa, 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 (Tb target), the first auxiliary element target 5 (Al target) and the fourth auxiliary element target 9 (Nd target). A negative bias power supply 16 is loaded on the workpiece holder 3, and then the heavy rare earth element coating is deposited on the surface of the NdFeB magnet 2 perpendicular to the oriented 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% respectively; 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 cools to room temperature, the sample is taken out of the vacuum chamber to complete the TbAlNd coating deposition. 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 make the vacuum degree of the vacuum chamber 1 2Pa; a negative bias power supply 16 is applied to the workpiece holder 3 through 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. The specific parameters of the vacuum chamber 1 are: voltage value -500V, frequency 80kHz, duty cycle 80%, and cleaning time 20min.

[0103] S206, Co-containing coating deposition

[0104] Reduce the Ar gas flow rate to make the gas pressure of the vacuum chamber 1 0.8Pa, 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 (selected as Zn target) and the third auxiliary element target 8 (selected as Mg target). Load the workpiece holder 3 with a negative bias voltage, turn on the DC pulse power supply 18 at the same time, start the anode layer ion source 17, increase the ion density, increase the sputtering amount of the Co element, and avoid the sputtering magnetic field drop caused by the high magnetic permeability of the Co element target 7. Then 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% respectively; the parameters of the bias power supply 16 are as follows: the bias voltage is -50 V, the pulse frequency is 60 kHz and the duty cycle is 80%; the parameters of the DC pulse power supply 18 are as follows: the power is 5 kW, the frequency is 120 kHz and the duty cycle is 60%; and the deposition time is 80 min.

[0105] S207, vacuum heat treatment

[0106] After the NdFeB magnet 2 is cooled to room temperature, the sample is taken out of the vacuum chamber and the TbAlNd coating and CoZnMg coating are completed. Then, it is placed in a vacuum diffusion furnace for heat treatment. The heat treatment parameters are: diffusion temperature of 870°C for 10 hours; annealing temperature of 480°C for 5 hours; vacuum degree of 7*10-3Pa.

[0107] S208, after the NdFeB magnet 2 is cooled 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 pulse 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 coercive force of diffused NdFeB magnet 2 increased by 6.31 kOe and the remanent temperature coefficient decreased significantly by 0.004% / °C, which confirmed that this method can achieve the synchronous optimization of the coercive force and remanent 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 magnetism B r (20 °C)]]> <![CDATA[Coercive force H cj (at 20 °C)]]> <![CDATA[Residual magnetic temperature coefficient | α(B r ) | (20 °C - 180 °C)]]> 13.35kGs 28.14kOe 0.133％ / ℃

[0111] Embodiment 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 in the Co-containing element coating Co-A2 are the elements 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 perpendicularly and parallel to the oriented C axis by magnetron sputtering, and then vacuum heat treatment is performed.

[0113] The specific processing process is as follows:

[0114] S301, sintered NdFeB magnet surface coating pretreatment

[0115] 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. Figure 2 The apparatus shown in the figure is used to deposit the coating containing heavy rare earth elements and the coating containing Co elements. The NdFeB magnet 2 is placed in the Figure 3 The coating fixture is inserted into the through hole 02 of the coating fixture shown in FIG. 1 and the NdFeB magnet 2 is fixed with screws 03. The coating fixture is then placed in a position 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 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 make the vacuum degree of the vacuum chamber 1 3Pa; a negative bias power supply 16 is applied to the workpiece holder 3 through 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 setting range of the vacuum chamber 1 is: voltage value -600V, frequency 30kHz, duty cycle 50%, cleaning time 30min.

[0118] S303, Heavy rare earth element coating deposition

[0119] The Ar gas flow rate is reduced to make the gas pressure of the vacuum chamber 1 0.9 Pa, 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 (Tb target), the first auxiliary element target 5 (Zn target) and the fourth auxiliary element target 9 (Cu target). A negative bias power supply 16 is loaded on the workpiece holder 3, and then the heavy rare earth element coating is deposited on the surface of the NdFeB magnet 2 perpendicular to the oriented 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 both 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 cools to room temperature, the sample is taken out of the vacuum chamber to complete the TbZnCu coating deposition. 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 NdFeB magnet 2 parallel to the orientation C axis

[0123] Pump the vacuum chamber 1 to 4.5*10 -3 Pa; introduce Ar gas and adjust the gas flow rate to make the vacuum degree of the vacuum chamber 1 3Pa; load the workpiece holder 3 with a negative bias power supply 16 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 oriented C axis. The specific parameters of the vacuum chamber 1 are: voltage value -600V, frequency 30kHz, duty cycle 50%, cleaning time 30min.

[0124] S306, Co-containing coating deposition

[0125] Reduce the Ar gas flow rate to make the gas pressure of the vacuum chamber 1 0.5Pa, 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, 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, turn on the DC pulse power supply 18 at the same time, start the anode layer ion source 17, increase the ion density, increase the sputtering amount of the Co element, and avoid the sputtering magnetic field drop caused by the high magnetic permeability of the Co element target 7. Then 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% respectively; 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; the deposition time is 70 min.

[0126] S307, vacuum heat treatment

[0127] After the NdFeB magnet 2 is cooled to room temperature, the sample is taken out of the vacuum chamber and the TbZnCu coating and the CoGdAl coating are completed; then it is placed in a vacuum diffusion furnace for heat treatment; heat treatment parameters: diffusion temperature is 930°C, time is 6 hours; annealing temperature is 490°C, time is 6 hours; vacuum degree is 3*10-3Pa.

[0128] S308, after the NdFeB magnet 2 is cooled to room temperature, take out the sample and perform magnetic property testing.

[0129] The magnetic properties of the diffused magnets were tested using a pulsed magnetic field intensity meter. The demagnetization curve, remanence, coercive force and remanence temperature coefficient were shown in the table below. 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 coercive force of diffused NdFeB magnet 2 increased by 6.3kOe and the remanence temperature coefficient decreased significantly by 0.006% / °C, which proved that this method can achieve the synchronous optimization of the coercive force 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 (at 20 °C)]]> <![CDATA[Coercive force H cj (20 °C)]]> <![CDATA[Remanence temperature coefficient | 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 aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned 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 coercive force and remanence temperature coefficient of sintered NdFeB magnets, characterized in that: First, a coating R1-A1 containing heavy rare earth elements is prepared on the surface of a NdFeB magnet perpendicular to the oriented 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 parallel to the oriented C axis; A2 is at least two of Gd, Nd, Al, Mg, Zn, and Cu; after the preparation of the coating R1-A1 containing heavy rare earth elements and the coating Co-A2 containing Co elements, the NdFeB magnet perpendicular to and parallel to the oriented C axis is 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 treatment of sintered NdFeB magnets before coating The surfaces of the NdFeB magnets perpendicular to and parallel to the oriented 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 cavity, a workpiece rack matchedly arranged in the center of the vacuum cavity, 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 matchedly arranged on the circumference of the vacuum cavity; 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; The target material of the second auxiliary element is connected to the fifth magnetron sputtering power supply, the target material of the first auxiliary element is connected to the sixth magnetron sputtering power supply; the NdFeB magnet is installed in the coating fixture, the fixture includes a stainless steel base, a stainless steel pillar matched and installed in the center of the upper part of the stainless steel base, and a stainless steel pressing block matched and installed on the upper part of the stainless steel pillar; the stainless steel pressing block is matched and provided with a circular through hole; 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 rack; 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 a bias power supply, and voltage parameters and cleaning time are set to complete the glow cleaning of the surface of the NdFeB magnet perpendicular to the oriented C axis; 3) Heavy rare earth element coating deposition The Ar gas flow rate is reduced to make the gas pressure of the vacuum chamber 0.5Pa-1Pa, and the workpiece holder is started to rotate; 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 loaded on 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 is cooled to room temperature, the sample is taken out from the vacuum chamber, and the heavy rare earth element coating R1-A1 is deposited; then the NdFeB magnet is loaded into the coating fixture and placed on the 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 to 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 oriented C axis; 6) Coating deposition containing Co element The Ar gas flow rate is reduced to make the gas pressure of the vacuum chamber 0.5Pa-1Pa, and the workpiece holder is started to rotate; 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 loaded on 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, increase the sputtering amount of the Co element, and avoid the sputtering magnetic field drop caused by the high magnetic permeability of the Co element target; then the Co element coating is deposited on the surface of the NdFeB magnet parallel to the oriented C axis; 7) Vacuum heat treatment After the NdFeB magnet is cooled to room temperature, the sample is taken out 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, and then the sample is placed in a vacuum diffusion furnace for heat treatment; 8) After the NdFeB magnet has cooled 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 as claimed in 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 as claimed in claim 2, characterized in that: The heavy rare earth element target in the 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.

5. The grain boundary diffusion method for simultaneously optimizing the coercive force and remanence temperature coefficient of sintered NdFeB magnets as claimed in claim 2, characterized in that: The workpiece rack speed range in step 3) is: 3-20rpm; The parameter ranges of the first magnetron sputtering power supply, the sixth magnetron sputtering power supply and the second magnetron sputtering power supply in the 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 is -30V to -150V, pulse frequency is 20kHz to 100kHz, and duty cycle is 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-60 min.

6. The grain boundary diffusion method for simultaneously optimizing the coercive force and remanence temperature coefficient of sintered NdFeB magnets as claimed in 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 as claimed in 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 as claimed in claim 2, characterized in that: The rotation speed range of the workpiece rack in step 6) is: 1-20 rpm; In the 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 is 1w / cm2-12w / cm2, pulse frequency is 30kHz-150kHz, and duty cycle is 20%-80%; In the 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 as claimed in 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, time is 5-10 hours; the parameter range of the low-temperature annealing is: annealing temperature is 450°C-520°C, time is 4-6 hours; the vacuum degree of the vacuum chamber in step 7) is less than 10-2Pa.

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