A NdFeB magnet with a surface protective film layer and a preparation method thereof

Abstract

The invention relates to the technical field of NdFeB magnet processing, and specifically to a NdFeB magnet with a surface protective film layer and a preparation method thereof. The NdFeB magnet comprises a NdFeB magnet substrate and a protective film layer, wherein the protective film layer comprises an intermediate layer and a protective layer from the inside to the outside, wherein the intermediate layer is a copper plating layer, and the protective layer is a zinc-chromium alloy plating layer. The zinc-chromium alloy plating is deposited on the surface of the NdFeB magnet by magnetron sputtering technology, and at the same time, by innovatively improving a carrier, the NdFeB magnet can be irregularly rotated and moved during the magnetron sputtering process, so that a uniform zinc-chromium alloy plating layer can be deposited on the NdFeB magnet, and the average deviation percentage of the zinc-chromium alloy plating thickness is optimized, so that there are no micro defects in the protective layer formed on the surface of the NdFeB magnet.

Description

Technical Field

[0001] The invention relates to the technical field of NdFeB magnet processing, in particular to a NdFeB magnet with a surface protective film layer and a preparation method thereof. Background Art

[0002] NdFeB magnet is a common permanent magnetic material with high magnetic properties. This magnet is composed of elements such as neodymium (Nd), iron (Fe) and boron (B), and is often used in the manufacture of various electronic products, motors, magnetic sensors and other equipment. NdFeB magnets are widely used in industry and daily life.

[0003] NdFeB magnets are usually coated on the surface to enhance their corrosion resistance and aesthetics. Common coating processes include electroplating, chemical plating and physical vapor deposition. Electroplating and chemical plating have become the mainstream industrial-scale surface protection treatment methods for NdFeB magnet substrates in China due to their high process maturity and low cost, but this type of technology itself has certain defects. First of all, both electroplating and chemical plating solutions will cause pollution to the environment. Secondly, due to the loose and porous structure of the NdFeB magnet substrate, the electroplating and chemical plating solutions may remain inside the NdFeB magnet substrate and gradually release during use, thereby destroying the surface coating. As a low-cost, waste-free, green and pollution-free physical vapor deposition technology, magnetron sputtering technology is widely used to improve the surface properties of various substrates.

[0004] In a Chinese patent application with patent number 201910314786.7, a composite modification method for surface protection of a NdFeB magnet substrate is disclosed. By combining high-power pulsed magnetron sputtering technology and plasma immersion ion implantation deposition technology, a dense coating is formed on the surface of the workpiece.

[0005] In the Chinese patent with patent application number 202010228017.8, a method for preparing a highly corrosion-resistant protective coating on the surface of a NdFeB magnet substrate is disclosed. An Al / Al2O3 multilayer film structure is formed by alternate deposition using magnetron sputtering technology, which effectively reduces the micro-defects of the coating. The uniform and dense Al2O3 layer blocks the grain boundaries that penetrate the coating, thereby significantly improving the corrosion resistance of the NdFeB magnet substrate.

[0006] However, in the above two technical solutions, vacuum aluminum plating is used as the protective layer of the NdFeB magnet, but the protective layer formed by vacuum aluminum plating has many problems in corrosion protection, and in the vacuum coating process, as described in the above two technical solutions, there will be micro defects in the thickness balance of the protective layer formed on the surface of the NdFeB magnet. Summary of the invention

[0007] In view of the above problems, the present invention provides a NdFeB magnet with a surface protective film layer and a preparation method thereof, wherein a zinc-chromium alloy coating is deposited on the surface of the NdFeB magnet by magnetron sputtering technology, and at the same time, by innovatively improving the carrier, the NdFeB magnet can be irregularly rotated and moved during the magnetron sputtering process, so that a uniform zinc-chromium alloy coating layer can be deposited on the NdFeB magnet, and the average deviation percentage of the zinc-chromium alloy coating thickness is optimized, so that the protective layer formed on the surface of the NdFeB magnet does not have micro defects.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] A neodymium iron boron magnet with a surface protective film layer, comprising:

[0010] NdFeB magnet substrate and protective film layer;

[0011] The NdFeB magnet substrate comprises the following raw materials in percentage by mass: 15-25% neodymium, 1-2.18% boron, 0.6-0.9% aluminum, 0.2-0.24% copper, 0.15-0.19% cobalt, 0.14-0.22% gallium, 1.0-1.5% silicon, 3-4.5% graphene, and the balance is iron;

[0012] The protective film layer is coated on the outside of the NdFeB magnet substrate, and the protective film layer includes an intermediate layer and a protective layer from the inside to the outside. The average thickness of the intermediate layer is 0.05-0.2 μm, and the average thickness of the protective layer is 1-3 μm.

[0013] As an improvement, the intermediate layer is a copper plating layer, the average thickness of the intermediate layer is 0.1 μm, and the average thickness deviation percentage is 0.2-0.5%.

[0014] As an improvement, the protective layer is a zinc-chromium alloy coating, the average thickness of the protective layer is 2 μm, the average thickness deviation percentage is 0.4-0.7%, and the zinc-chromium alloy coating includes the following raw materials in mass percentage: 70-90% zinc and 10-30% chromium.

[0015] In addition, the present invention also provides a method for preparing the NdFeB magnet with a surface protective film layer as described in any one of the above, comprising the following steps:

[0016] Step 1: Cleaning: Clean the NdFeB magnet substrate and the vacuum chamber of the coating equipment, and dry them;

[0017] Step 2: etching: placing the NdFeB magnet after cleaning and drying on a carrier in a vacuum chamber, evacuating the vacuum chamber with a mechanical pump and a molecular pump, and then applying a negative bias voltage to the surface of the NdFeB magnet substrate for ion etching;

[0018] Step 3: Plating the intermediate layer, using a high-energy pulsed magnetron sputtering power supply to provide a negative bias voltage to the intermediate layer target, and simultaneously using an external power supply to provide a negative high voltage to the NdFeB magnet substrate, the high-energy intermediate layer ions generated by the high-energy pulsed magnetron sputtering enter the surface of the NdFeB magnet substrate, and form a magnetron sputtering intermediate layer film with an average thickness of 0.05-0.2μm on the surface of the NdFeB magnet substrate;

[0019] Step 4: Plating the protective layer, closing the intermediate layer target, using a medium frequency magnetron sputtering power supply to provide a negative bias voltage to the protective layer target, and synchronously applying an external power supply to provide a negative bias voltage to the NdFeB magnet substrate, the protective layer ions generated by the medium frequency magnetron sputtering enter the surface of the NdFeB magnet substrate, and form a magnetron sputtering protective layer film with an average thickness of 1-3μm on the surface of the NdFeB magnet substrate;

[0020] Step 5: Output: Complete the coating work of the NdFeB magnet substrate, release the remaining gas in the vacuum chamber, and take out the cooled NdFeB magnet substrate.

[0021] As an improvement, the specific steps of step 2 include:

[0022] Step 101: Place the NdFeB magnet substrate on a carrier in a vacuum chamber, and evacuate the vacuum chamber to a vacuum degree of ≤10 -3 Pa;

[0023] Step 102, using a gas flow meter to introduce an inert gas into the vacuum chamber, the gas flow rate is 50-120 sccm, and the pressure of the vacuum chamber is controlled to be 0.5-1.5 Pa;

[0024] Step 103, providing a negative pulse power supply to the material carrier, and setting the voltage value of the negative pulse power supply to 500V-1000V, the pulse width to 50μs-100μs, and the frequency to 10Hz-100Hz;

[0025] Step 104 , continuously provide pulse power for 10 to 30 minutes to complete ion etching on the surface of the NdFeB magnet.

[0026] As an improvement, the specific steps of step three include:

[0027] Step 201, after etching and cleaning, the flow rate of the inert gas is controlled by a gas flow meter, and the gas flow rate is 40-150 sccm, so that the pressure of the vacuum chamber is maintained at 0.3 Pa-0.8 Pa;

[0028] Step 202, providing a high-energy pulsed magnetron sputtering power supply to the copper target material to apply a negative bias voltage, ensuring that the voltage value of the high-energy pulsed magnetron sputtering power supply is 700V to 800V, the pulse width is 100μs to 200μs, and the frequency is 50Hz to 300Hz;

[0029] Step 203, while providing a negative bias voltage to the copper target, a negative high voltage is provided to the carrier through an external power supply, wherein the negative high voltage has a voltage value of 10 kV to 50 kV, a pulse width of 50 μs to 200 μs, and a frequency of 50 Hz to 300 Hz;

[0030] Step 204, maintaining the nickel ion implantation and deposition on the surface of the NdFeB magnet for 10 to 20 minutes.

[0031] As an improvement, the specific steps of step 4 include:

[0032] Step 301, keep the position of the carrier unchanged, introduce inert gas through the gas flow controller, the gas flow rate is 60-200 sccm, and adjust the gas pressure of the vacuum chamber to 0.3Pa-1Pa;

[0033] Step 302, the medium frequency magnetron sputtering power supply provides a negative bias voltage to the zinc-chromium alloy target according to a predetermined current value and duty cycle, and sets the target current to 3-8A and the duty cycle to 10-80%;

[0034] Step 303, while providing a negative bias voltage to the zinc-chromium alloy target, an external power supply provides a negative bias voltage to the carrier, the negative bias voltage value is 50V to 150V, and the frequency is 10Hz to 100Hz;

[0035] Step 304: The working time of depositing the zinc-chromium alloy film on the surface of the NdFeB magnet is maintained at 30 to 60 minutes.

[0036] As an improvement, in step three and step four, the carrier rack drives the NdFeB magnet to revolve around the central axis of the carrier rack during the coating process, and synchronously, the NdFeB magnets on each group of carrier rollers on the carrier rack rotate around the axis of the carrier roller, and each group of NdFeB magnets is independently set to rotate irregularly.

[0037] As an improvement, the material carrier comprises a material carrier turntable, a rotating shaft, a planetary gear set and a material carrier set;

[0038] The material loading turntable is detachably mounted on the rotating shaft of the vacuum coating machine horizontally;

[0039] A plurality of the self-rotating shafts are arranged equidistantly on the circumference of the material-carrying turntable and are installed on the circumferential edge of the material-carrying turntable. The self-rotating shafts rotate synchronously with the material-carrying turntable.

[0040] The planetary gear set is installed between the self-rotating shaft and the material-carrying turntable, and the self-rotating shaft is arranged to rotate by the planetary gear set;

[0041] A plurality of the material loading groups are arranged equidistantly along the axial direction of the rotation shaft. The material loading groups clamp the NdFeB magnets and rotate synchronously with the rotation shaft. Synchronously, the material loading groups clamp the NdFeB magnets and perform irregular rotation adjustment.

[0042] As an improvement, the material loading group includes a driving bevel gear, a material loading seat, a driven bevel gear, a driven shaft, a material clamping seat, a material clamping head, a limit frame and a permanent magnet;

[0043] The active bevel gear is fixedly sleeved on the rotating shaft, and the active bevel gear rotates synchronously with the rotating shaft;

[0044] The material carrier is movably sleeved on the rotating shaft, and the material carrier is located below the active bevel gear;

[0045] A plurality of groups of driven shafts are arranged equidistantly around the circumference, and the driven shafts are detachably and rotatably mounted on the material carrier, and the driven shafts are meshed with the driving bevel gear via driven bevel gears;

[0046] The clamping seat is integrally connected with the driven shaft, and the clamping head is disposed opposite to the clamping seat. The clamping head is elastically adjustable and clamps the NdFeB magnet. The clamping head is made of non-magnetic material.

[0047] The limit frame is fixedly mounted on the clamping seat, the limit frame is located on the clamping head bracket, and the limit frame is located at the periphery of the clamped NdFeB magnet;

[0048] The permanent magnet is arranged at the end of the clamping seat which is not connected to the driven shaft, and the permanent magnet is arranged in a semicircular shape.

[0049] The beneficial effects of the present invention are:

[0050] (1) The present invention forms a protective layer by depositing a zinc-chromium alloy coating on the surface of the NdFeB magnet through magnetron sputtering technology. Vacuum zinc plating can provide the NdFeB magnet with anti-rust, anti-corrosion, wear resistance and other properties, while vacuum chromium plating can provide the NdFeB magnet with a long-lasting bright and smooth surface layer, which is used to reduce the damage to the protective film layer caused by the friction of the NdFeB magnet, thereby improving the durability and anti-rust and anti-corrosion properties of the protective film layer;

[0051] (2) The present invention first physically deposits copper plating on the surface of the NdFeB magnet to form an intermediate layer, and then uses the intermediate layer as the basis for the external zinc plating and chromium plating protective layer. The copper-plated intermediate layer is used to improve the compatibility of the protective layer with the NdFeB magnet, thereby improving the firmness of the protective layer and the NdFeB magnet coating, and improving the service life of the NdFeB magnet protective layer;

[0052] (3) The preparation method of the present invention utilizes the irregular rotation movement adjustment of the NdFeB magnet during the physical deposition coating process of magnetron sputtering, so that during the physical deposition coating process, all parts of the NdFeB magnet can be uniformly coated, and there is no fixed clamping point during the coating process of the NdFeB magnet, so that a coating layer with uniform thickness can be formed on the surface of the NdFeB magnet, so that the average thickness deviation percentage is reduced to 0.4-0.7%;

[0053] (4) The present invention utilizes the self-rotation of the rotating shaft to drive the carrier group to rotate, and utilizes the adsorption of the permanent magnets between the carrier groups to fix the carrier group, and then realizes the rotation of the driven shaft through the cooperation of the active bevel gear and the driven bevel gear, thereby realizing the rotation adjustment of the NdFeB magnet without a fixed clamping point, so that the NdFeB magnet can be intermittently rotated and adjusted, and a balanced physical deposition coating is achieved.

[0054] In summary, the present invention has the advantages of NdFeB magnets being wear-resistant and corrosion-resistant, providing a lasting bright and smooth outer layer, and having a uniform coating thickness, and is particularly suitable for the technical field of NdFeB magnet processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 This is a physical picture of the coated NdFeB magnet of Example 1 of the present invention;

[0056] Figure 2 This is a schematic diagram of the process for preparing a coated NdFeB magnet according to the present invention;

[0057] Figure 3 A three-dimensional diagram of the magnetron sputtering device of the present invention;

[0058] Figure 4 It is a schematic diagram of the three-dimensional structure of the material carrier of the present invention;

[0059] Figure 5 This is a schematic diagram of the bottom structure of the material carrier of the present invention;

[0060] Figure 6 This is a schematic diagram of the front view structure of the rotation axis of the present invention;

[0061] Figure 7 This is a schematic diagram of the magnetic adsorption state of the rotating shaft of the material carrier of the present invention;

[0062] Figure 8 This is a schematic diagram of the three-dimensional structure of the material loading assembly of the present invention;

[0063] Fig. 9 for Figure 8 The enlarged structural diagram at A in the middle;

[0064] Fig.10 This is a schematic diagram of the three-dimensional structure of the material carrier of the present invention;

[0065] Fig.11 It is a schematic diagram of the three-dimensional structure of the driven shaft of the present invention;

[0066] Fig.12 This is a schematic cross-sectional view of the structure of the material loading assembly of the present invention;

[0067] Fig.13 for Fig.12 Enlarged structural diagram at B in the middle.

[0068] In the figure: 1, material loading rack, 10, rotating shaft, 100, NdFeB magnet, 11, material loading turntable, 12, rotating shaft, 13, planetary gear set, 131, sun gear, 132, planetary gear, 14, material loading set, 141, driving bevel gear, 142, material loading seat, 1421, base, 1422, clamp, 1423, positioning groove, 143, driven bevel gear, 144, driven shaft, 145, material clamping seat, 146, material clamping head, 147, limit frame, 148 permanent magnet, 149, spring member. DETAILED DESCRIPTION

[0069] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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.

[0070] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0071] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0072] Embodiment 1:

[0073] like Figure 1As shown, a neodymium iron boron magnet with a surface protective film layer comprises:

[0074] NdFeB magnet substrate and protective film layer;

[0075] The NdFeB magnet substrate comprises the following raw materials in percentage by mass: 15-25% neodymium, 1-2.18% boron, 0.6-0.9% aluminum, 0.2-0.24% copper, 0.15-0.19% cobalt, 0.14-0.22% gallium, 1.0-1.5% silicon, 3-4.5% graphene, and the balance is iron;

[0076] The protective film layer is coated on the outside of the NdFeB magnet substrate, and the protective film layer includes an intermediate layer and a protective layer from the inside to the outside. The average thickness of the intermediate layer is 0.05-0.2 μm, and the average thickness of the protective layer is 1-3 μm.

[0077] Wherein, the intermediate layer is a copper plating layer, the average thickness of the intermediate layer is 0.1 μm, and the average thickness deviation percentage is 0.2-0.5%.

[0078] Furthermore, the protective layer is a zinc-chromium alloy coating, the average thickness of the protective layer is 2 μm, the average thickness deviation percentage is 0.4-0.7%, and the zinc-chromium alloy coating includes the following raw materials in mass percentage: 70-90% zinc and 10-30% chromium.

[0079] Whether zinc plating or chromium plating is performed on the surface of the NdFeB magnet, it is the existing conventional coating technology. The difference between the present invention and the existing coating technology is that the present invention uses zinc-chromium alloy to be coated on the surface of the NdFeB magnet in the form of physical deposition through magnetron sputtering.

[0080] Galvanizing can effectively prevent NdFeB magnets from chemically reacting with oxygen and moisture in the external environment such as air and water, thereby preventing NdFeB magnets from rusting and corroding. It can increase the surface hardness of NdFeB magnets, improve their wear resistance and extend their service life. Chromium plating gives NdFeB magnets an extremely bright and smooth appearance, and the appearance is durable, which can effectively reduce the wear between NdFeB magnets.

[0081] However, if zinc plating and chromium plating are performed separately to form a composite coating, the bonding adhesion with the NdFeB magnet will be greatly reduced. The present invention performs coating by magnetron sputtering to ionize zinc and chromium. The ionized zinc and chromium are deposited on the surface of the NdFeB magnet to form a composite coating. Compared with the composite coating of individual layers, the ionized zinc and chromium coating has a tighter bonding between zinc and chromium.

[0082] It is further explained that the present invention also uses a copper plating layer as an intermediate layer to improve the adhesion between the zinc-chromium plating layer and the neodymium iron boron magnet, thereby preventing the zinc-chromium plating layer from falling off after long-term operation.

[0083] To further illustrate, the calculation formula for the average deviation percentage of thickness is: △t=(t-t0) / t0×100%, t0 is the nominal thickness, t is the average thickness, and the calculation formula for the average thickness is [\text{average thickness}=\frac{\sum_{i=1}^{n}t_i}{n}], where (t_i) is the thickness of the (i)th measurement point, and (n) is the total number of measurement points.

[0084] The coating thickness is tested by magnetic weather meter. The smaller the average thickness deviation percentage is, the more balanced the coating thickness of NdFeB magnet is.

[0085] Compared with the existing vacuum magnetic sputtering coating, the present invention can control the average thickness deviation percentage to be much smaller than the existing technical level. The reason is that the present invention eliminates the existence of clamping points, and the surface of the NdFeB magnet can be evenly coated without microscopic defects such as cracks and holes.

[0086] Embodiment 2:

[0087] like Figure 2 As shown, referring to Example 1, Example 2 of the present invention describes a method for preparing the NdFeB magnet with a surface protective film layer as described in Example 1, comprising the following steps:

[0088] Step 1: Cleaning: Clean the NdFeB magnet substrate and the vacuum chamber of the coating equipment, and dry them;

[0089] Step 2: etching: placing the NdFeB magnet after cleaning and drying on a carrier in a vacuum chamber, evacuating the vacuum chamber with a mechanical pump and a molecular pump, and then applying a negative bias voltage to the surface of the NdFeB magnet substrate for ion etching;

[0090] The specific steps of etching include:

[0091] Step 101: Place the NdFeB magnet substrate on a carrier in a vacuum chamber, and evacuate the vacuum chamber to a vacuum degree of ≤10 -3 Pa;

[0092] Step 102, using a gas flow meter to introduce an inert gas into the vacuum chamber, the gas flow rate is 50-120 sccm, and the pressure of the vacuum chamber is controlled to be 0.5-1.5 Pa;

[0093] Step 103, providing a negative pulse power supply to the material carrier, and setting the voltage value of the negative pulse power supply to 500V-1000V, the pulse width to 50μs-100μs, and the frequency to 10Hz-100Hz;

[0094] Step 104 , continuously provide pulse power for 10 to 30 minutes to complete ion etching on the surface of the NdFeB magnet.

[0095] Ion etching is the most common form of dry etching. Its principle is that the gas exposed to the electron area forms plasma. The resulting ionized gas and the gas composed of released high-energy electrons form plasma or ions. When the ionized gas atoms are accelerated by the electric field, they will release enough force to impact the surface of the NdFeB magnet substrate and remove the oxidized impurities in the NdFeB magnet substrate.

[0096] Step 3: Plating the intermediate layer, using a high-energy pulsed magnetron sputtering power supply to provide a negative bias voltage to the intermediate layer target, and simultaneously using an external power supply to provide a negative high voltage to the NdFeB magnet substrate, the high-energy intermediate layer ions generated by the high-energy pulsed magnetron sputtering enter the surface of the NdFeB magnet substrate, and form a magnetron sputtering intermediate layer film with an average thickness of 0.05-0.2μm on the surface of the NdFeB magnet substrate;

[0097] The specific steps of plating the intermediate layer include:

[0098] Step 201, after etching and cleaning, the flow rate of the inert gas is controlled by a gas flow meter, and the gas flow rate is 40-150 sccm, so that the pressure of the vacuum chamber is maintained at 0.3 Pa-0.8 Pa;

[0099] Step 202, providing a high-energy pulsed magnetron sputtering power supply to the copper target material to apply a negative bias voltage, ensuring that the voltage value of the high-energy pulsed magnetron sputtering power supply is 700V to 800V, the pulse width is 100μs to 200μs, and the frequency is 50Hz to 300Hz;

[0100] Step 203, while providing a negative bias voltage to the copper target, a negative high voltage is provided to the carrier through an external power supply, wherein the negative high voltage has a voltage value of 10 kV to 50 kV, a pulse width of 50 μs to 200 μs, and a frequency of 50 Hz to 300 Hz;

[0101] Step 204, maintaining the nickel ion implantation and deposition on the surface of the NdFeB magnet for 10 to 20 minutes.

[0102] A high-energy pulsed magnetron sputtering power supply is used to provide a negative bias voltage to the copper target to generate a high-density copper plasma. A higher pulse peak power and a lower pulse duty cycle are used to increase the density of the plasma. At the same time, an external power supply is used to provide a negative high voltage to the workpiece holder, and the pulse waveforms of the two are matched to complete the copper plasma immersion of the NdFeB magnet, realize ion implantation deposition, and form a copper coating on the surface of the NdFeB magnet, which is used as an intermediate layer to improve the adhesion of the NdFeB magnet to zinc and chromium.

[0103] Step 4: Plating the protective layer, closing the intermediate layer target, using a medium frequency magnetron sputtering power supply to provide a negative bias voltage to the protective layer target, and synchronously applying an external power supply to provide a negative bias voltage to the NdFeB magnet substrate, the protective layer ions generated by the medium frequency magnetron sputtering enter the surface of the NdFeB magnet substrate, and form a magnetron sputtering protective layer film with an average thickness of 1-3μm on the surface of the NdFeB magnet substrate;

[0104] The specific steps of plating the protective layer include:

[0105] Step 301, keep the position of the carrier unchanged, introduce inert gas through the gas flow controller, the gas flow rate is 60-200 sccm, and adjust the gas pressure of the vacuum chamber to 0.3Pa-1Pa;

[0106] Step 302, the medium frequency magnetron sputtering power supply provides a negative bias voltage to the zinc-chromium alloy target according to a predetermined current value and duty cycle, and sets the target current to 3-8A and the duty cycle to 10-80%;

[0107] Step 303, while providing a negative bias voltage to the zinc-chromium alloy target, an external power supply provides a negative bias voltage to the carrier, the negative bias voltage value is 50V to 150V, and the frequency is 10Hz to 100Hz;

[0108] Step 304: The working time of depositing the zinc-chromium alloy film on the surface of the NdFeB magnet is maintained at 30 to 60 minutes.

[0109] Zinc itself has a sacrificial protective effect. When the surface is corroded, zinc is more easily oxidized, thereby protecting the internal iron and neodymium. Combined with the high oxidation resistance of chromium, the two work together to form a very stable and durable protective layer, which is especially suitable for use in harsh environments. In addition, the two are ion-plated to eliminate the crystal interface between the zinc layer and the chromium layer, forming a nano-crystalline structure with stronger anti-rust and anti-corrosion capabilities. It can withstand neutral salt spray tests for more than 750 hours, and make the neodymium iron boron magnet have ultra-high hardness (18GPa), extremely low friction coefficient (0.1), and good coating adhesion (greater than 55N).

[0110] Step 5: Output: Complete the coating work of the NdFeB magnet substrate, release the remaining gas in the vacuum chamber, and take out the cooled NdFeB magnet substrate.

[0111] Embodiment 3:

[0112] like Figures 3 to 13 As shown, with reference to Example 2, Example 3 of the present invention is described, which is a material carrier structure used for vacuum coating of NdFeB magnets.

[0113] Specifically, in order to improve the balance of the coating thickness of the NdFeB magnets and eliminate the uneven coating caused by the carrier frame on the clamping points of the NdFeB magnets, so that the average deviation percentage of the coating thickness reaches 0.4-0.7%, the present invention also uses a special carrier frame in the steps three and four, which drives the NdFeB magnets to revolve around the central axis of the carrier frame. Synchronously, the NdFeB magnets on each group of carrier rollers on the carrier frame rotate around the axis of the carrier roller, and each group of NdFeB magnets is independently arranged to rotate irregularly, and the clamping point is dynamically changed.

[0114] As a preferred specific structure, the material carrier 1 includes a material carrier turntable 11, a rotating shaft 12, a planetary gear set 13 and a material carrier set 14;

[0115] The material loading turntable 11 is horizontally detachably mounted on the rotating shaft 10 of the vacuum coating machine, and the rotation of the rotating shaft 10 drives the material loading turntable 11 to rotate actively;

[0116] A plurality of the self-rotating shafts 12 are arranged equidistantly on the circumference of the material loading turntable 11, and the self-rotating shafts 12 rotate synchronously with the material loading turntable 11;

[0117] The planetary gear set 13 is installed between the rotating shaft 12 and the loading turntable 11. The rotating shaft 12 is arranged to rotate by the planetary gear set 13. The planetary gear set 13 includes a fixed sun gear 131 and a planetary gear 132 sleeved on the rotating shaft 12. The sun gear 131 is sleeved outside the rotating shaft 10. The sun gear 131 is fixed and does not rotate, while the planetary gear 132 rotates with the rotating shaft 12. The planetary gear 132 cooperates with the sun gear 131 to drive the rotating shaft 12 to rotate.

[0118] A plurality of the loading groups 14 are arranged equidistantly along the axial direction of the rotating shaft 12. The loading groups 14 clamp the NdFeB magnets and rotate synchronously with the rotating shaft 12. Synchronously, the loading groups 14 clamp the NdFeB magnets and perform irregular rotation adjustment.

[0119] As a preferred specific structure, the material loading group 14 includes a driving bevel gear 141, a material loading seat 142, a driven bevel gear 143, a driven shaft 144, a material clamping seat 145, a material clamping head 146, a limit frame 147 and a permanent magnet 148;

[0120] The active bevel gear 141 is fixedly sleeved on the rotating shaft 12, and the active bevel gear 141 rotates synchronously with the rotating shaft 12;

[0121] The material carrier 142 is movably sleeved on the rotating shaft 12, and the material carrier 142 is located below the active bevel gear 141. The material carrier 142 can rotate relative to the rotating shaft 12. The material carrier 142 is supported by a disk portion fixedly connected to the rotating shaft 12 below, and the disk portion holds the material carrier 142. The material carrier 142 includes a base 1421 at a lower portion and a clamp 1422 swingably arranged at an upper portion. A positioning groove 1423 for positioning a bearing on a driven shaft 144 is arranged on the base 1421, and the clamp 1422 is arranged at the positioning groove 1423. The clamp 1422 cooperates with the positioning groove 1423 to hold the driven shaft 144 tightly, and the driven shaft 144 can rotate at the same time. The locking structure of the clamp 1422 and the base 1421 adopts a latch rotation locking method, which can be quickly disassembled and assembled;

[0122] A plurality of groups of driven shafts 144 are arranged equidistantly around the circumference, and the driven shafts 144 are detachably and rotatably mounted on the material carrier 142, and the driven shafts 144 are meshed with the driving bevel gear 141 through the driven bevel gear 143. When the rotating shaft 12 rotates, the driven shafts 144 rotate along with the rotating shaft 12 around the axial direction of the rotating shaft 12;

[0123] The clamping seat 145 is integrally connected with the driven shaft 144, and the clamping head 146 is oppositely arranged on the clamping seat 145. The clamping head 146 is elastically adjusted by a sleeved spring member 149, and the clamping head 146 clamps the NdFeB magnet, and the clamping end of the clamping head 146 is hemispherical, and the clamping head 146 is point-contacted with the NdFeB magnet. The clamping head 146 is made of non-magnetic material, and relative movement occurs between the clamping head 146 and the NdFeB magnet during plating;

[0124] The limit frame 147 is fixedly mounted on the clamping seat 145, the limit frame 147 is located between the clamping heads 146, and the limit frame 147 is located at the periphery of the clamped NdFeB magnet, the limit frame 147 is fixed to the clamping seat 145 by a lock nut and a screw, and the limit frame 147 can be replaced according to the shape of the NdFeB magnet; the shape of the limit frame 147 is in the shape of the NdFeB magnet, and the limit frame 147 is slightly larger than the NdFeB magnet. The NdFeB magnet can move irregularly in the limit frame 147, but will not leave the limit frame 147, thereby realizing the dynamic change of the clamping point of the NdFeB magnet 100 by the clamping head 146, so that all surfaces of the NdFeB magnet can be coated, even the clamping point can be coated. In addition, when the NdFeB magnet is annular, the clamping head 146 clamps the blank area in the center of the NdFeB magnet, and can also realize the full surface balanced coating of the annular NdFeB magnet;

[0125] The permanent magnet 148 is disposed at the end of the clamping seat 145 that is not connected to the driven shaft 144. The permanent magnet 148 is disposed in a semicircular shape, and the other semicircular portion next to the permanent magnet 148 is made of non-magnetic material.

[0126] Specifically, when vacuum coating is performed, the carrier rotates in the vacuum chamber. During rotation, the NdFeB magnet is clamped in the limit frame 147, and the two sides are limited by the clamping head 146. As the carrier 1 revolves, the rotation shaft 12 rotates. When the two adjacent groups of rotation shafts 12 rotate, the driven shaft 144 is just in the same straight line. At this time, the permanent magnets 148 located at the ends of the clamping seat 145 will dock with each other to form adsorption, so that the carrier 142 no longer rotates with the rotation shaft 12. At this time, the driven shaft 144 no longer rotates around the rotation shaft 12, but instead drives the driven shaft 144 to rotate around the rotation shaft 12 through the cooperation of the active bevel gear 141 and the driven bevel gear 143. The driven shaft 144 rotates axially, and the semicircular permanent magnet 148 will be staggered with the self-rotation, so that the permanent magnet 148 is no longer adsorbed. At this time, the driven shaft 144 that has lost the adsorption of the permanent magnet 148 rotates again with the self-rotation shaft 12 until the driven shaft 144 is located in the same straight line again, forming adsorption, so that the driven shaft 144 is fixed again, and when the driven shaft 144 rotates, the clamping head 146 will rotate with the NdFeB magnet, and the NdFeB magnet moves in the limit frame 147 with the rotation, so that the clamping point on the NdFeB magnet changes, thereby completing the setting of the NdFeB magnet without a fixed clamping point, so that the entire surface of the NdFeB magnet is plated.

[0127] It is further explained that when the driven shaft 144 is self-rotating by magnetic adsorption, the remaining driven shafts 144 on each group of loading seats 142 also self-rotate synchronously, and the driven shaft 144 has just completed six self-rotation cycles from adsorption and docking to re-adsorption and docking, so that the permanent magnet 148 has just returned to the initial position, so that the driven shaft 144 on the adjacent rotating shaft 12 can be docked and adsorbed again, and this cycle is repeated, so that during the vacuum coating process, the clamping points on the NdFeB magnet are always in an alternating state, which can achieve a balanced coating on the surface of the NdFeB magnet.

[0128] Example 4

[0129] The coated NdFeB magnet sheets in Example 1 were prepared by using the preparation method in Example 2 and the carrier in Example 3. The size of the NdFeB magnet sheets was 30*12.5*2.5 mm.

[0130] Among them, the nominal thickness of the middle layer is set to 0.05μm, and the average thickness of the protective layer is 1μm. The average thickness of the middle layer is measured by a magnetic thickness gauge to be 0.0501μm, and the average thickness of the protective layer is 1.005μm. The average deviation percentage of the thickness of the middle layer is calculated to be 0.02%, and the average deviation percentage of the thickness of the protective layer is 0.5%. The neutral salt spray test scheme of the national standard GB6458-86 salt spray test is adopted, and it is measured that the neodymium iron boron magnet can withstand the neutral salt spray test for more than 753h. The dynamic friction coefficient is measured by a rotary friction testing machine to be 0.07.

[0131] Example 5

[0132] The coated NdFeB magnet sheets in Example 1 were prepared by using the preparation method in Example 2 and the carrier in Example 3. The size of the NdFeB magnet sheets was 30*12.5*2.5 mm.

[0133] Among them, the nominal thickness of the middle layer is set to 0.2μm, and the average thickness of the protective layer is 3μm. The average thickness of the middle layer is measured by a magnetic thickness gauge to be 0.201μm, and the average thickness of the protective layer is 3.02μm. The average deviation percentage of the thickness of the middle layer is calculated to be 0.05%, and the average deviation percentage of the thickness of the protective layer is 0.67%. The neutral salt spray test scheme of the national standard GB6458-86 salt spray test is adopted, and it is measured that the neodymium iron boron magnet can withstand the neutral salt spray test for more than 950h. The dynamic friction coefficient is measured by a rotary friction testing machine to be 0.067.

[0134] Example 6

[0135] The coated NdFeB magnet sheets in Example 1 were prepared by using the preparation method in Example 2 and the carrier in Example 3. The size of the NdFeB magnet sheets was 30*12.5*2.5 mm.

[0136] Among them, the nominal thickness of the middle layer is set to 0.1μm, and the average thickness of the protective layer is 2μm. The average thickness of the middle layer is measured by a magnetic thickness gauge to be 0.1005μm, and the average thickness of the protective layer is 2.012μm. The average deviation percentage of the thickness of the middle layer is calculated to be 0.05%, and the average deviation percentage of the thickness of the protective layer is 0.6%. The neutral salt spray test scheme of the national standard GB6458-86 salt spray test is adopted, and it is measured that the neodymium iron boron magnet can withstand the neutral salt spray test for more than 878h. The dynamic friction coefficient is measured by a rotary friction testing machine to be 0.069.

[0137] Comparative Example 1

[0138] The preparation method in Example 2 was adopted, a conventional material carrier was used, and the protective layer target material was a pure zinc target material, and a NdFeB magnet sheet with a size of 30*12.5*2.5 mm was obtained.

[0139] Among them, the nominal thickness of the middle layer is set to 0.1μm, and the average thickness of the protective layer is 2μm. The average thickness of the middle layer is measured by a magnetic thickness gauge to be 0.101μm, and the average thickness of the protective layer is 2.03μm. The average deviation percentage of the thickness of the middle layer is calculated to be 1%, and the average deviation percentage of the thickness of the protective layer is 1.5%. The neutral salt spray test scheme of the national standard GB6458-86 salt spray test is adopted, and it is measured that the neodymium iron boron magnet can withstand the neutral salt spray test for more than 700h. The dynamic friction coefficient is measured by a rotary friction testing machine to be 0.12.

[0140] Comparative Example 2

[0141] The preparation method in Example 2 was adopted, a conventional material carrier was used, and the protective layer target material was a pure chromium target material, and a NdFeB magnet sheet with a size of 30*12.5*2.5 mm was obtained.

[0142] Among them, the nominal thickness of the middle layer is set to 0.1μm, and the average thickness of the protective layer is 2μm. The average thickness of the middle layer is measured by a magnetic thickness gauge to be 0.102μm, and the average thickness of the protective layer is 2.032μm. The average deviation percentage of the thickness of the middle layer is calculated to be 2%, and the average deviation percentage of the thickness of the protective layer is 1.6%. The neutral salt spray test scheme of the national standard GB6458-86 salt spray test is adopted, and it is measured that the neodymium iron boron magnet can withstand the neutral salt spray test for more than 704h. The dynamic friction coefficient is measured by a rotary friction testing machine and is 0.10.

[0143] Comparative Example 3

[0144] The preparation method in Example 2 and the carrier in Example 3 are used, the target material of the protective layer is a pure zinc target material, and the size of the NdFeB magnet sheet is 30*12.5*2.5mm.

[0145] Among them, the nominal thickness of the middle layer is set to 0.1μm, and the average thickness of the protective layer is 2μm. The average thickness of the middle layer is measured by a magnetic thickness gauge to be 0.1004μm, and the average thickness of the protective layer is 2.014μm. The average deviation percentage of the thickness of the middle layer is calculated to be 0.4%, and the average deviation percentage of the thickness of the protective layer is 0.7%. The neutral salt spray test scheme of the national standard GB6458-86 salt spray test is adopted, and it is measured that the neodymium iron boron magnet can withstand the neutral salt spray test for more than 715h. The dynamic friction coefficient is measured by a rotary friction testing machine to be 0.11.

[0146] Comparative Example 4

[0147] The preparation method in Example 2 and a conventional material carrier are used, the protective layer target material is a zinc-chromium alloy target material, and the size of the NdFeB magnet sheet is 30*12.5*2.5 mm.

[0148] Among them, the nominal thickness of the middle layer is set to 0.1μm, and the average thickness of the protective layer is 2μm. The average thickness of the middle layer is measured by a magnetic thickness gauge to be 0.1010μm, and the average thickness of the protective layer is 2.05μm. The average thickness deviation percentage of the middle layer is calculated to be 1%, and the average thickness deviation percentage of the protective layer is 2.5%. The neutral salt spray test scheme of the national standard GB6458-86 salt spray test is adopted, and it is measured that the neodymium iron boron magnet can withstand the neutral salt spray test for more than 850h. The dynamic friction coefficient is measured by a rotary friction testing machine to be 0.08.

[0149] The data comparison of Examples 4 to 6 and Comparative Examples 1 to 4 is shown in the following table:

[0150]

[0151]

[0152] From the comparison in the above table, it can be seen that the coating balance of conventional pure zinc or pure chromium-plated NdFeB magnets is far inferior to that of the zinc-chromium alloy-plated NdFeB magnets of the present invention. At the same time, the corrosion resistance is also far inferior to that of the zinc-chromium alloy-plated NdFeB magnets of the present invention. The degree of wear during friction is also far greater than that of the zinc-chromium alloy-plated NdFeB magnets of the present invention.

[0153] In addition, for the neodymium iron boron magnets with zinc-chromium alloy coating, the balance, corrosion resistance and wear service life of the coating are greatly reduced without using the improved carrier of the present invention.

[0154] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A neodymium iron boron magnet with a surface protective film layer, characterized in that: include: NdFeB magnet substrate and protective film layer; The NdFeB magnet substrate comprises the following raw materials in percentage by mass: 15-25% neodymium, 1-2.18% boron, 0.6-0.9% aluminum, 0.2-0.24% copper, 0.15-0.19% cobalt, 0.14-0.22% gallium, 1.0-1.5% silicon, 3-4.5% graphene, and the balance is iron; The protective film layer is coated on the outside of the NdFeB magnet substrate, and the protective film layer includes an intermediate layer and a protective layer from the inside to the outside. The average thickness of the intermediate layer is 0.05-0.2μm, the intermediate layer is a copper plating layer, and the average thickness deviation percentage is 0.2-0.5%. The average thickness of the protective layer is 1-3μm, the protective layer is a zinc-chromium alloy plating layer, and the average thickness deviation percentage is 0.4-0.7%, and the zinc-chromium alloy plating layer includes the following raw materials in mass percentage: 70-90% zinc and 10-30% chromium.

2. The NdFeB magnet with a surface protective film layer according to claim 1, characterized in that: The intermediate layer has an average thickness of 0.1 μm.

3. The NdFeB magnet with a surface protective film layer according to claim 1, characterized in that: The average thickness of the protective layer is 2 μm.

4. A method for preparing a NdFeB magnet having a surface protective film layer as claimed in any one of claims 1 to 3, characterized in that: The following steps are involved: Step 1: Cleaning: Clean the NdFeB magnet substrate and the vacuum chamber of the coating equipment, and dry them; Step 2: etching: placing the NdFeB magnet after cleaning and drying on a carrier in a vacuum chamber, evacuating the vacuum chamber with a mechanical pump and a molecular pump, and then applying a negative bias voltage to the surface of the NdFeB magnet substrate for ion etching; Step 3: Plating the intermediate layer, using a high-energy pulsed magnetron sputtering power supply to provide a negative bias voltage to the intermediate layer target, and simultaneously using an external power supply to provide a negative high voltage to the NdFeB magnet substrate, the high-energy intermediate layer ions generated by the high-energy pulsed magnetron sputtering enter the surface of the NdFeB magnet substrate, and form a magnetron sputtering intermediate layer film with an average thickness of 0.05-0.2μm on the surface of the NdFeB magnet substrate; Step 4: Plating the protective layer, closing the intermediate layer target, using a medium frequency magnetron sputtering power supply to provide a negative bias voltage to the protective layer target, and synchronously applying an external power supply to provide a negative bias voltage to the NdFeB magnet substrate, the protective layer ions generated by the medium frequency magnetron sputtering enter the surface of the NdFeB magnet substrate, and form a magnetron sputtering protective layer film with an average thickness of 1-3μm on the surface of the NdFeB magnet substrate; Step 5: Output: Complete the coating work of the NdFeB magnet substrate, release the remaining gas in the vacuum chamber, and take out the cooled NdFeB magnet substrate.

5. The NdFeB magnet with a surface protective film layer according to claim 4, characterized in that: The specific steps of step 2 include: Step 101: Place the NdFeB magnet substrate on a carrier in a vacuum chamber, and evacuate the vacuum chamber to a vacuum degree of ≤10 -3 Pa; Step 102, using a gas flow meter to introduce an inert gas into the vacuum chamber, the gas flow rate is 50-120 sccm, and the pressure of the vacuum chamber is controlled to be 0.5-1.5 Pa; Step 103, providing a negative pulse power supply to the material carrier, and setting the voltage value of the negative pulse power supply to 500V-1000V, the pulse width to 50μs-100μs, and the frequency to 10Hz-100Hz; Step 104 , continuously provide pulse power for 10 to 30 minutes to complete ion etching on the surface of the NdFeB magnet.

6. The NdFeB magnet with a surface protective film layer according to claim 4, characterized in that: The specific steps of step three include: Step 201, after etching and cleaning, the flow rate of the inert gas is controlled by a gas flow meter, and the gas flow rate is 40-150 sccm, so that the pressure of the vacuum chamber is maintained at 0.3 Pa-0.8 Pa; Step 202, providing a high-energy pulsed magnetron sputtering power supply to the copper target material to apply a negative bias voltage, ensuring that the voltage value of the high-energy pulsed magnetron sputtering power supply is 700V to 800V, the pulse width is 100μs to 200μs, and the frequency is 50Hz to 300Hz; Step 203, while providing a negative bias voltage to the copper target, a negative high voltage is provided to the carrier through an external power supply, wherein the negative high voltage has a voltage value of 10 kV to 50 kV, a pulse width of 50 μs to 200 μs, and a frequency of 50 Hz to 300 Hz; Step 204, maintaining the nickel ion implantation and deposition on the surface of the NdFeB magnet for 10 to 20 minutes.

7. The NdFeB magnet with a surface protective film layer according to claim 4, characterized in that: The specific steps of step 4 include: Step 301, keep the position of the carrier unchanged, introduce inert gas through the gas flow controller, the gas flow rate is 60-200 sccm, and adjust the gas pressure of the vacuum chamber to 0.3Pa-1Pa; Step 302, the medium frequency magnetron sputtering power supply provides a negative bias voltage to the zinc-chromium alloy target according to a predetermined current value and duty cycle, and sets the target current to 3-8A and the duty cycle to 10-80%; Step 303, while providing a negative bias voltage to the zinc-chromium alloy target, an external power supply provides a negative bias voltage to the carrier, the negative bias voltage value is 50V to 150V, and the frequency is 10Hz to 100Hz; Step 304: The working time of depositing the zinc-chromium alloy film on the surface of the NdFeB magnet is maintained at 30 to 60 minutes.

8. The NdFeB magnet with a surface protective film layer according to claim 4, characterized in that: In step three and step four, during the coating process, the carrier rack drives the NdFeB magnet to revolve around the central axis of the carrier rack. Synchronously, the NdFeB magnets on each group of carrier rollers on the carrier rack rotate around the axis of the carrier roller, and each group of NdFeB magnets is independently set to rotate irregularly.

9. The NdFeB magnet with a surface protective film layer according to claim 8, characterized in that: The material carrier comprises a material carrier turntable, a rotating shaft, a planetary gear set and a material carrier set; The material loading turntable is detachably mounted on the rotating shaft of the vacuum coating machine horizontally; A plurality of the self-rotating shafts are arranged equidistantly on the circumference of the material-carrying turntable and are installed on the circumferential edge of the material-carrying turntable. The self-rotating shafts rotate synchronously with the material-carrying turntable. The planetary gear set is installed between the self-rotating shaft and the material-carrying turntable, and the self-rotating shaft is arranged to rotate by the planetary gear set; A plurality of the material loading groups are arranged equidistantly along the axial direction of the rotation shaft. The material loading groups clamp the NdFeB magnets and rotate synchronously with the rotation shaft. Synchronously, the material loading groups clamp the NdFeB magnets and perform irregular rotation adjustment.

10. The NdFeB magnet with a surface protective film layer according to claim 9, characterized in that: The material loading group includes a driving bevel gear, a material loading seat, a driven bevel gear, a driven shaft, a material clamping seat, a material clamping head, a limit frame and a permanent magnet; The active bevel gear is fixedly sleeved on the rotating shaft, and the active bevel gear rotates synchronously with the rotating shaft; The material carrier is movably sleeved on the rotating shaft, and the material carrier is located below the active bevel gear; A plurality of groups of driven shafts are arranged equidistantly around the circumference, and the driven shafts are detachably and rotatably mounted on the material carrier, and the driven shafts are meshed with the driving bevel gear via driven bevel gears; The clamping seat is integrally connected with the driven shaft, and the clamping head is disposed opposite to the clamping seat. The clamping head is elastically adjustable and clamps the NdFeB magnet. The limit frame is fixedly mounted on the clamping seat, the limit frame is located between the clamping heads, and the limit frame is located at the periphery of the clamped NdFeB magnet; The permanent magnet is arranged at the end of the clamping seat which is not connected to the driven shaft, and the permanent magnet is arranged in a semicircular shape.

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