Background
The neodymium iron boron permanent magnet material is a rare earth permanent magnet material with the largest usage amount at present, is widely applied to various industries such as computers, motors, wind driven generators, electric automobiles, instruments and meters, magnetic transmission bearings, high-fidelity speakers, nuclear magnetic resonance imagers, aerospace navigators and the like, and has great potential application prospects in the emerging technical fields of maglev trains and the like. China vigorously develops the industry of the neodymium iron boron magnet by virtue of the advantages of rare earth resources and production cost, and has become the first producing and consuming countries in the world.
The surface treatment of the neodymium iron boron permanent magnet material has important influence on the performance of the neodymium iron boron permanent magnet material, the existing surface treatment comprises electroplating, chemical plating, electrophoresis, vacuum deposition, coating and the like, the wear resistance of a metallic coating obtained by the traditional electroplating process is poor, the vacuum coating technology can be used for preparing metal-nonmetal alloy (such as TiN), nonmetal alloy (such as SiC) and other films besides the metallic coating, but the cost of the real-fast coating equipment is high, and the efficiency is low. Taking NiCuNi + TiN as an example, if a vacuum plating mode is adopted in the whole process, independent vacuum Ni plating equipment, Cu plating equipment and TiN plating equipment are needed, the equipment needs to wait for vacuum degree and temperature rise and fall during switching, the efficiency is low, and the cost is high. These conventional single surface treatment methods all result in limited corrosion resistance and wear resistance of the prepared surface coating, and therefore, it is an urgent need to develop a novel composite coating for the surface of a metal magnet to improve the corrosion resistance and wear resistance.
Disclosure of Invention
Technical problem to be solved by the invention
The invention aims to provide a corrosion-resistant and wear-resistant composite plating layer applicable to neodymium iron boron and a preparation method thereof, aiming at the technical problem that the wear resistance and corrosion resistance of the surface treated metal magnet materials such as neodymium iron boron in the prior art are poor.
Technical scheme
The invention provides a preparation method of a corrosion-resistant and wear-resistant composite coating applicable to neodymium iron boron, which comprises the steps of firstly plating a metal coating on the surface of a metal magnet through electroplating, and then plating a secondary coating on the surface of the metal coating through vacuum plating; the secondary plating layer is a non-metal alloy layer and/or a metal oxide layer and/or a metal nitride layer.
Preferably, the metal plating layer is a single layer or multiple layers;
and/or the metal coating is one or more of zinc, nickel, copper, tin, zinc-nickel alloy, zinc-iron alloy and nickel-phosphorus alloy;
and/or the thickness of the metal plating layer is 5-20 μm.
Preferably, the metal element in the secondary coating is Al and/or Zn and/or Ti and/or Zr;
and/or the thickness of the secondary plating layer is 2-20 μm.
Preferably, the secondary coating is oxidized to obtain a composite coating with a dense passivation layer on the surface.
Preferably, the method comprises the following specific steps:
(1) plating a metal coating on the neodymium iron boron workpiece in a mode of oil removal, rust removal, activation, electroplating and blow drying;
(2) loading a metal magnet workpiece plated with a metal coating and a buffer material by a stainless steel mesh cage, carrying out vacuum nano composite coating, allowing the mesh cage to rotate and revolve simultaneously in the coating process, and carrying out multi-arc ion plating and/or magnetron sputtering coating to obtain a secondary coating.
(3) And introducing oxidizing gas into the vacuum chamber to react with the secondary coating to obtain a compact passivation layer.
Preferably, the electroplating mode in the step (1) is barrel plating and/or rack plating; the barrel plating adopts a unidirectional rotation mode or a forward and reverse alternate rotation mode, and the rack plating adopts a cathode linear movement mode or a rotary movement mode.
Preferably, one or more of sulfuric acid, nitric acid, hydrochloric acid and organic carboxylic acid is/are used as the activation solution in the step (1), the concentration of the activation solution is 0.05-4%, and the activation time is 5-120 s.
Preferably, the net cage in the step (2) is a cylindrical cage-shaped hanger, the diameter of which is 80-180mm, and the height of which is 800-1200 mm;
and/or the revolution rotating speed in the step (2) is 2-10r/min, the rotation rotating speed is 10-20r/min, and the coating current is 20-80A.
Preferably, the oxidizing gas in step (3) is one or more of nitrogen, oxygen, ozone and nitrogen oxide,
or a mixture of one or more of nitrogen, oxygen, ozone, nitrogen oxides and an inert gas.
The invention also provides a composite coating prepared by any one of the preparation methods.
Technical effects
Compared with the prior art, the invention has the beneficial effects that:
1. according to the corrosion-resistant and wear-resistant composite coating applicable to neodymium iron boron, the metal coating is plated on the surface of the metal magnet through electroplating, and then the secondary coating is plated on the surface of the metal coating through vacuum plating, wherein the secondary coating is a metal layer and/or a metal oxide layer and/or a metal nitride layer, and the prepared composite coating can effectively improve the wear resistance and the corrosion resistance.
2. According to the preparation method of the corrosion-resistant and wear-resistant composite coating applicable to neodymium iron boron, the secondary coating is oxidized to obtain the composite coating with the surface containing the compact passivation layer, and the surface of the composite coating is passivated after the preparation of the composite coating is completed, so that the surface roughness of the composite coating can be improved, the wear-resistant performance of the composite coating is improved, the corrosion-resistant performance of the composite coating is improved, and the penetration of corrosive liquid is prevented.
3. The corrosion-resistant and wear-resistant composite coating applicable to neodymium iron boron and the preparation method thereof have the advantages of simple preparation process, economic materials and wide application prospect.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments; moreover, the embodiments are not relatively independent, and can be combined with each other according to needs, so that a better effect is achieved. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
The embodiment provides a preparation method of a corrosion-resistant and wear-resistant composite coating applicable to neodymium iron boron, which comprises the following specific steps:
step (1): loading 3kg of 20mm by 5mm neodymium iron boron magnet and 3kg of steel balls into a roller together, and removing oil at the temperature of 55 ℃ for 10 min;
step (2): performing acid cleaning and rust removal on the product obtained in the step (1) after twice water cleaning, wherein the acid cleaning time is 3min, and the acid cleaning conductivity is 100 mS/cm;
and (3): performing two-time washing on the product obtained in the step (2), then performing ultrasonic cleaning, and immediately activating after the cleaning is finished, wherein the activation time is 1 min; wherein, the activation adopts sulphuric acid as the activation liquid, and the concentration of the activation liquid is 0.05 percent;
and (4): performing two times of water washing on the product obtained in the step (3), then putting the product into a nickel tank for electroplating, controlling the film thickness to be 3 microns, wherein the current is 40A, and the time is 60 min;
and (5): and (5) washing the product obtained in the step (4) with three times of water, and activating for 1 min. Then copper plating is carried out after two times of water washing, the current is 30A, the time is 90min, and the film thickness is controlled to be 5 microns;
and (6): drying the product obtained in the step (5) by blanking and drying, loading the product in a stainless steel net cage, then placing the product in vacuum coating equipment, heating the product to 100 ℃, and vacuumizing the vacuum coating equipment to 9 x 10-3pa;
And (7): performing vacuum coating by adopting magnetron sputtering AlN plating, wherein revolution and rotation are performed simultaneously in the coating process, and the film layer is controlled to be 2 microns; wherein the net cage is a cylindrical cage-shaped hanger, the diameter of the net cage is 80mm, the height of the net cage is 800mm, the revolution speed is 5r/min, the rotation speed is 10r/min, and the coating current is 20A;
and (8): and (4) closing the target power supply after the film coating is finished, continuously filling oxygen until the vacuum degree is 2 x 10pa, and oxidizing for 20min to obtain a compact passivation layer.
The embodiment also provides the corrosion-resistant and wear-resistant composite coating which is prepared by the method and can be applied to the neodymium iron boron.
The composite coating obtained in the embodiment has high appearance consistency, high binding force grade 0 in a Baige test (GB/T9286-1998 paint and varnish paint film lattice test), high Vickers hardness 3301HV and excellent wear resistance;
as can be seen from figure 1, the composite plating layer subjected to the neutral salt spray test has a perfect surface and effectively prevents the invasion of corrosive liquid, and the neutral salt spray test is more than 200 hours; as can be seen from the SEM of fig. 2, the composite plating layer has a dense surface, small and few pores, can effectively prevent corrosive substances from entering, and has excellent corrosion resistance.
Comparative example 1
The comparative example provides a preparation method of a coating applicable to neodymium iron boron, which is different from the preparation method of example 1 in that only nickel and copper electroplating is carried out, subsequent magnetron sputtering coating is not carried out, and the rest steps are substantially the same, and the specific preparation method comprises the following steps:
step (1): loading 3kg of 20mm by 5mm neodymium iron boron magnetic steel and 3kg of steel balls into a roller together, and performing ultrasonic oil removal at the oil removal temperature of 55 ℃, for 10min and at the roller rotation speed of 4 r/min;
step (2): performing acid washing and rust removal on the product obtained in the step (1) after twice water washing, wherein the acid washing time is 3min, the acid washing conductivity is 100mS/cm, and the roller rotating speed is 4 r/min;
and (3): performing two-time washing on the product obtained in the step (2), then performing ultrasonic cleaning, and immediately activating after the cleaning is finished, wherein the activation time is 1min, and the rotating speed of a roller is 4 r/min;
and (4): performing two times of water washing on the product obtained in the step (3), then putting the product into a nickel tank for electroplating, controlling the current to be 40A, the time to be 60min, the rotating speed of a roller to be 4r/min, and controlling the film thickness to be 3 microns;
and (5): and (5) washing the product obtained in the step (4) with three times of water, and activating for 1 min. Then copper plating is carried out after two times of water washing, the current is 30A, the time is 90min, the film thickness is controlled to be 5 microns, and the rotating speed of a roller is 4 r/min;
and (6): and (5) washing the product obtained in the step (5) with three times of water, and activating for 1 min. Then, after two times of water washing, nickel plating is carried out, the current is 30A, the time is 90min, the film thickness is controlled to be 2 microns, and the rotating speed of a roller is 4 r/min;
and (7): and (4) drying the product obtained in the step (6) at a temperature of 80 ℃ for 1 h.
This comparative example also provides a coating prepared as described above.
The composite coating obtained by the comparative example has high appearance consistency, and the binding force is in the grade of 0 in the Baige test (GB/T9286-1998 paint and varnish test), the neutral salt spray test is carried out for 72h, the rust is generated, and the Vickers hardness is 550 HV.
Comparing comparative example 1 with example 1, it can be seen that the corrosion resistance and wear resistance of the plating layer obtained by the single electroplating method are reduced, which shows the excellent performance of the composite plating layer of example 1 of the present invention.
Comparative example 2
The comparative example provides a preparation method of a coating applicable to neodymium iron boron, which is different from the preparation method of example 1 in that only magnetron sputtering coating is carried out, electroplating is not carried out, and the rest steps are approximately the same, and the specific preparation method comprises the following steps:
step (1): loading 3kg of 20mm by 5mm neodymium iron boron magnetic steel and 3kg of steel balls into a roller together, and performing ultrasonic oil removal at the oil removal temperature of 55 ℃, for 10min and at the roller rotation speed of 4 r/min;
step (2): performing acid washing and rust removal on the product obtained in the step (1) after twice water washing, wherein the acid washing time is 3min, the acid washing conductivity is 100mS/cm, and the roller rotating speed is 4 r/min;
and (3): washing the product obtained in the step (2) twice, blanking and drying;
and (4): putting the product obtained in the step (3) and 3kg of steel balls into a stainless steel mesh cage, heating the stainless steel mesh cage to 100 ℃ in vacuum coating equipment, and vacuumizing the vacuum coating equipment to 9 x 10-3pa;
And (5): performing vacuum coating by adopting magnetron sputtering AlN plating, and controlling the film layer to be 5 microns;
and (6): and (3) closing the target power supply after the film coating is finished, continuously filling oxygen to the vacuum degree of 2 x 10pa, oxidizing for 20min, cooling to the temperature below 80 ℃, and discharging.
This comparative example also provides a coating prepared as described above.
The composite plating layer obtained by the comparative example has high appearance consistency and binding force of grade 0 (GB/T9286-1998 paint and varnish test), and the composite plating layer rusts in 48h of neutral salt spray test and has Vickers hardness of 2905 HV.
It can be seen that the vacuum-coated layer exhibited poor corrosion resistance and wear resistance in the absence of the electroplated layer in this comparative example.
The invention has been described in detail hereinabove with reference to specific exemplary embodiments thereof. It will, however, be understood that various modifications and changes may be made without departing from the scope of the invention as defined in the appended claims. The detailed description and drawings are to be regarded as illustrative rather than restrictive, and any such modifications and variations are intended to be included within the scope of the present invention as described herein. Furthermore, the background is intended to be illustrative of the state of the art as developed and the meaning of the present technology and is not intended to limit the scope of the invention or the application and field of application of the invention.
More specifically, although exemplary embodiments of the invention have been described herein, the invention is not limited to these embodiments, but includes any and all embodiments modified, omitted, combined (e.g., between various embodiments), adapted and/or substituted as would be recognized by those skilled in the art from the foregoing detailed description, and which may be combined as desired. The limitations in the claims are to be interpreted broadly based the language employed in the claims and not limited to examples described in the foregoing detailed description or during the prosecution of the application, which examples are to be construed as non-exclusive. Any steps recited in any method or process claims may be executed in any order and are not limited to the order presented in the claims. The scope of the invention should, therefore, be determined only by the appended claims and their legal equivalents, rather than by the descriptions and examples given above.