CN110993231A - Surface-alloyed high-corrosion-resistance sintered NdFeB magnet and preparation method thereof - Google Patents

Surface-alloyed high-corrosion-resistance sintered NdFeB magnet and preparation method thereof Download PDF

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Publication number
CN110993231A
CN110993231A CN201911163510.XA CN201911163510A CN110993231A CN 110993231 A CN110993231 A CN 110993231A CN 201911163510 A CN201911163510 A CN 201911163510A CN 110993231 A CN110993231 A CN 110993231A
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Prior art keywords
sintered ndfeb
ndfeb magnet
magnet
embedding
corrosion resistant
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Inventor
徐光青
刘帮
杨红义
张鹏杰
吕珺
李炳山
汪冬梅
孙威
吴玉程
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Hefei University of Technology
BGRIMM Technology Group Co Ltd
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Hefei University of Technology
BGRIMM Technology Group Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
    • H01F1/047—Alloys characterised by their composition
    • H01F1/053—Alloys characterised by their composition containing rare earth metals
    • H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
    • H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
    • H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
    • H01F1/0575—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together
    • H01F1/0577—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together sintered
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
    • H01F41/0253—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Manufacturing Cores, Coils, And Magnets (AREA)
  • Hard Magnetic Materials (AREA)

Abstract

The invention discloses a surface alloying high corrosion resistance sintered NdFeB magnet, which is subjected to siliconizing by a grain boundary diffusion technology to realize surface alloying of the magnet, so that the corrosion resistance of the magnet is improved. The invention discloses a preparation method of a surface alloying high corrosion resistant sintered NdFeB magnet, which comprises the specific steps of magnet pretreatment, preparation of an embedding penetrant and an embedding siliconizing treatment process, wherein the content of Si in surface alloying and the depth of an alloy infiltration layer can be realized by adjusting the parameters of the embedding penetrant and the siliconizing treatment process. The method solves the problem of poor self corrosion resistance of the sintered NdFeB magnet, and compared with an integral doping alloying method, the method improves the self corrosion resistance of the magnet and does not influence the magnetic performance of the magnet.

Description

Surface-alloyed high-corrosion-resistance sintered NdFeB magnet and preparation method thereof
Technical Field
The invention belongs to the field of surface protection and alloying corrosion resistance of magnetic materials, and particularly relates to surface alloying of a sintered NdFeB magnet and a preparation method thereof.
Background
Since the advent of the world, the NdFeB permanent magnet material has been widely used in high-tech fields such as aviation, aerospace, maglev trains, magnetic medical technology and the like due to its excellent properties such as high magnetic energy product, high coercive force, high remanence and the like. China is rich in rare earth resources, and the NdFeB permanent magnet material industry gradually takes China as the leading factor. With consequent concern for corrosion and failure. Sintered NdFeB magnets have a multi-phase structure (mainly including a main phase, an Nd-rich phase, and a B-rich phase) prepared by powder metallurgy, and a neodymium-rich phase surrounds the main phase as grain boundaries, and a boron-rich phase is also present in the grain boundaries in many cases, and the potential difference between the phases is large. The Nd-rich phase has the highest electrochemical activity due to high Nd content, anodic dissolution occurs at a lower potential, and the magnet undergoes grain boundary corrosion to cause premature failure, thereby seriously limiting the further expansion of the application field of the sintered NdFeB magnet. Therefore, a method for improving the corrosion resistance of sintered NdFeB magnets has received great attention.
The surface coating and the alloy are mainly added in the industrial production, the electroplating process and the deposition process are usually adopted for the surface coating, the electroplating cost is low, the corrosion resistance of the coating is good, the application is more, but along with the gradual increase of the environmental protection consciousness, the three wastes generated by electroplating always restrict the development of the coating. The deposition mainly includes PVD (physical vapor deposition) and CVD (chemical vapor deposition). The physical vapor method can be divided into vacuum evaporation and magnetron sputtering, the PVD obtains the characteristics of compact film, small thickness, no pollution and the like, but the production cost is high, and the large-scale development of the application industry is yet to be researched. CVD is promising as a new field of research, but the complexity and uncontrollable nature of gas phase doping during deposition exists. The alloying method is a method of reducing grain boundary corrosion by adding an alloy element to improve the composition of an intercrystalline phase and reduce the potential difference between phases inside a magnet. In the traditional alloying method, Dy, Al, Nd, Ga, Ti, W, Mo and other elements are added to partially replace a neodymium-rich phase in a grain boundary in the powder sintering process, so that the corrosion resistance of the magnet can be improved. However, the intergranular phase formed by the addition of the alloy element is a non-magnetic phase, which causes the magnetic properties of the magnet to be lowered.
Therefore, it is of great practical value to develop a sintered NdFeB magnet surface alloying and a method for preparing the same to overcome the above disadvantages.
Disclosure of Invention
The invention aims to: the surface alloying is realized by siliconizing the sintered NdFeB magnet, the corrosion resistance is improved, and the magnetic performance of the magnet is not influenced.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a surface-alloyed high-corrosion-resistance sintered NdFeB magnet is obtained by siliconizing the sintered NdFeB magnet through a grain boundary diffusion technology.
A preparation method of a surface alloying high corrosion resistant sintered NdFeB magnet is characterized in that: the method comprises the following specific steps:
(1) magnet pretreatment
Firstly, carrying out sand blowing treatment on a sintered NdFeB magnet, and then carrying out drying treatment after acid washing and ultrasonic cleaning;
(2) preparation of embedding penetrant
Mixing a silicon source, silicon dioxide powder and ammonium chloride, and putting the mixture into a ball mill for ball milling to obtain an embedding infiltration agent with uniform mixed materials;
(3) siliconizing treatment
And placing the pre-treated sintered NdFeB magnet in a burning boat with a cover, covering the magnet with an embedding and permeating agent, placing the magnet in a vacuum furnace, and carrying out siliconizing treatment under vacuum to obtain the sintered NdFeB magnet with alloyed surface.
Further, nitric acid with the mass fraction of 3% is adopted during acid washing in the step (1), and the acid washing time is 30-60 s.
Further, the ultrasonic cleaning time in the step (1) is 1-5 min.
Further, in the step (2), the silicon source is one or a mixture of silicon iron powder and silicon powder.
Further, the mass ratio of the silicon dioxide to the silicon source in the step (2) is 1:5.5-1: 6.5; the mass ratio of the ammonium chloride to the silicon source is 1:45-1: 60.
Further, the rotation speed of the ball mill in the step (2) is 100-.
Further, the specific process of step (3) is as follows: and placing the pre-treated sintered NdFeB magnet in a burning boat with a cover, covering the magnet with a penetrating agent, compacting, placing in a vacuum furnace, heating to 800 ℃ at the speed of 4-6 ℃/min under a vacuum state, and preserving heat for 30-120min to carry out siliconizing treatment to obtain the sintered NdFeB magnet with alloyed surface.
Compared with the prior art, the invention has the beneficial effects that:
the preparation method for surface alloying of the sintered NdFeB magnet can realize surface alloying of the sintered NdFeB magnet and improve the self corrosion resistance of the sintered NdFeB magnet. Compared with the traditional method that the performance of the magnet is reduced by adding alloying, the invention forms alloying on the surface layer, improves the corrosion resistance of the matrix and ensures that the magnetic performance is not reduced.
Drawings
FIG. 1 is an SEM topography of an untreated sintered NdFeB magnet;
fig. 2 is an SEM topography of the surface alloyed high corrosion resistant sintered NdFeB magnet obtained in example 1;
(compare with figure 1 and figure 2, the sintered NdFeB magnet has more complete surface, more compact grain arrangement and alloy formation of rich neodymium phase and silicon at the grain boundary after siliconizing treatment.)
Fig. 3 is an SEM morphology of the cross section of the surface alloyed high corrosion resistant sintered NdFeB magnet obtained in example 2.
Detailed Description
The present invention is further described with reference to the following examples, which are intended to be illustrative and illustrative only, and various modifications, additions and substitutions for the specific embodiments described herein may be made by those skilled in the art without departing from the spirit of the invention or exceeding the scope of the claims.
The present invention will be described with reference to specific examples.
Example 1:
(1) magnet pretreatment
Firstly, carrying out sand blowing treatment on a sintered NdFeB magnet, then carrying out acid washing for 30s by using a 3% nitric acid solution, carrying out ultrasonic cleaning for 3min by using deionized water, and then carrying out cold-air low-angle blow-drying treatment.
(2) Preparation of embedding penetrant
The ferrosilicon powder, the silicon dioxide powder and the ammonium chloride are mixed according to the mass ratio of 85: 13.5: 1.5, mixing, putting the mixture into a high-energy planetary ball mill for ball milling (the ball milling speed is 200r/min, and the ball milling time is 6 hours) to obtain the embedding infiltration agent with uniform mixed materials.
(3) Siliconizing treatment
And (3) placing the pre-treated sintered NdFeB magnet in a burning boat with a cover, covering the magnet with an embedding and permeating agent, slightly compacting, placing in a vacuum furnace, heating to 600 ℃ at the speed of 5 ℃/min in a vacuum state, and preserving heat for 1h for siliconizing to obtain the sintered NdFeB magnet with alloyed surface.
Comparative example 1 is an untreated sintered NdFeB magnet. The corrosion potential is-1.0589V and the self-corrosion current density is 344.38 muA cm after electrochemical polarization curve test-2Soaking in 3.5 wt% NaCl solution for 10min to corrode;
the sintered NdFeB magnet with alloyed surface layer obtained according to the steps has the corrosion potential of-0.9782V and the self-corrosion current density of 49.46V in the electrochemical corrosion test8μA·cm-2And the corrosion appears after the glass is soaked in 3.5 wt% NaCl solution for 4 hours, and the comprehensive corrosion resistance of the glass is obviously better than that of the comparative example.
Example 2:
this example was prepared in the same manner as in example 1 except that the heating temperature in step (3) was 585 ℃.
Tests show that the sintered NdFeB magnet with alloyed surface layer obtained according to the steps has the corrosion potential of-1.010V and the self-corrosion current density of 106.32 muA cm in an electrochemical corrosion test-2And the corrosion appears after being soaked in 3.5 wt% NaCl solution for 4 hours, and the comprehensive corrosion resistance of the corrosion inhibitor is better than that of the comparative example.
Example 3:
this example was prepared in the same manner as in example 1 except that the heating temperature in step (3) was 550 ℃.
Tests show that the sintered NdFeB magnet with alloyed surface layer obtained according to the steps has the corrosion potential of-1.018V and the self-corrosion current density of 169.05 muA cm in an electrochemical corrosion test-2And the corrosion appears after the glass is soaked in 3.5 wt% NaCl solution for 3.5h, and the comprehensive corrosion resistance of the glass is obviously better than that of the comparative example.
Example 4:
this example was prepared in the same manner as in example 1 except that the heating temperature in step (3) was 500 ℃.
Tests show that the sintered NdFeB magnet with alloyed surface layer obtained according to the steps has the corrosion potential of-1.048V and the self-corrosion current density of 138.56 mu A cm in the electrochemical corrosion test-2And the corrosion appears after the glass is soaked in 3.5 wt% NaCl solution for 3 hours, and the comprehensive corrosion resistance of the glass is obviously better than that of the comparative example.
Example 5:
the preparation method of this example is the same as example 1, except that ferrosilicon powder is replaced by silica powder in step (2), and the heating temperature in step (3) is 700 ℃.
Tests show that the sintered NdFeB magnet with alloyed surface layer obtained according to the steps has the corrosion potential of-1.015V and the self-corrosion current density of 12.14 muA cm in an electrochemical corrosion test-2The corrosion appears after being soaked in 3.5 wt% NaCl solution for 12 hours, and the composite resistance is realizedThe corrosion performance was significantly better than the control example.
Example 6:
this example was prepared in the same manner as in example 5 except that the heating temperature in step (3) was 800 ℃.
Tests show that the sintered NdFeB magnet with alloyed surface layer obtained according to the steps has the corrosion potential of-0.932V and the self-corrosion current density of 11.284 muA cm in the electrochemical corrosion test-2And the corrosion appears after the glass is soaked in 3.5 wt% NaCl solution for 18 hours, and the comprehensive corrosion resistance of the glass is obviously better than that of the comparative example.

Claims (8)

1. A surface layer alloying high corrosion resistant sintered NdFeB magnet is characterized in that: and siliconizing the sintered NdFeB magnet by a grain boundary diffusion technology to obtain the surface-alloyed high-corrosion-resistance sintered NdFeB magnet.
2. A method for producing the surface-alloyed high-corrosion-resistant sintered NdFeB magnet according to claim 1, characterized in that: the method comprises the following specific steps:
(1) magnet pretreatment
Firstly, carrying out sand blowing treatment on a sintered NdFeB magnet, and then carrying out drying treatment after acid washing and ultrasonic cleaning;
(2) preparation of embedding penetrant
Mixing a silicon source, silicon dioxide powder and ammonium chloride, and putting the mixture into a ball mill for ball milling to obtain an embedding infiltration agent with uniform mixed materials;
(3) siliconizing treatment
And placing the pre-treated sintered NdFeB magnet in a burning boat with a cover, covering the magnet with an embedding and permeating agent, placing the magnet in a vacuum furnace, and carrying out siliconizing treatment under vacuum to obtain the sintered NdFeB magnet with alloyed surface.
3. The method for preparing a surface alloyed high corrosion resistant sintered NdFeB magnet according to claim 2, characterized in that: nitric acid with the mass fraction of 3% is adopted during acid washing in the step (1), and the acid washing time is 30-60 s.
4. The method for preparing a surface alloyed high corrosion resistant sintered NdFeB magnet according to claim 3, wherein: the ultrasonic cleaning time in the step (1) is 1-5 min.
5. The method for preparing a surface alloyed high corrosion resistant sintered NdFeB magnet according to claim 2, characterized in that: in the step (2), the silicon source is one or a mixture of silicon iron powder and silicon powder.
6. The method for preparing a surface alloyed high corrosion resistant sintered NdFeB magnet according to claim 2, characterized in that: in the step (2), the mass ratio of the silicon dioxide to the silicon source is 1:5.5-1: 6.5; the mass ratio of the ammonium chloride to the silicon source is 1:45-1: 60.
7. The method for preparing a surface alloyed high corrosion resistant sintered NdFeB magnet according to claim 2, characterized in that: in the step (2), the rotating speed of the ball mill is 100-.
8. The method for preparing a surface alloyed high corrosion resistant sintered NdFeB magnet according to claim 2, characterized in that: the specific process of the step (3) is as follows:
and placing the pre-treated sintered NdFeB magnet in a burning boat with a cover, covering the magnet with an embedding and permeating agent, compacting, placing in a vacuum furnace, heating to 800 ℃ at 4-6 ℃/min under a vacuum state, and preserving heat for 30-120min to carry out siliconizing treatment to obtain the sintered NdFeB magnet with alloyed surface.
CN201911163510.XA 2019-11-25 2019-11-25 Surface-alloyed high-corrosion-resistance sintered NdFeB magnet and preparation method thereof Pending CN110993231A (en)

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CN112992521A (en) * 2021-03-09 2021-06-18 合肥工业大学 Preparation method of low-weight-loss sintered NdFeB magnet
CN114639540A (en) * 2020-12-15 2022-06-17 太原理工大学 Neodymium iron boron permanent magnet surface copper-infiltrated layer and preparation method thereof

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Publication number Priority date Publication date Assignee Title
CN114639540A (en) * 2020-12-15 2022-06-17 太原理工大学 Neodymium iron boron permanent magnet surface copper-infiltrated layer and preparation method thereof
CN112992521A (en) * 2021-03-09 2021-06-18 合肥工业大学 Preparation method of low-weight-loss sintered NdFeB magnet

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Application publication date: 20200410