CN106601462A - Surface crystal boundary modification method for improving corrosion resistance of sintered Nd-Fe-B magnet and product prepared by method - Google Patents
Surface crystal boundary modification method for improving corrosion resistance of sintered Nd-Fe-B magnet and product prepared by method Download PDFInfo
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- CN106601462A CN106601462A CN201611150743.2A CN201611150743A CN106601462A CN 106601462 A CN106601462 A CN 106601462A CN 201611150743 A CN201611150743 A CN 201611150743A CN 106601462 A CN106601462 A CN 106601462A
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- 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
- H01F41/026—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 protecting methods against environmental influences, e.g. oxygen, by surface treatment
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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
- H01F1/0572—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 with a protective layer
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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
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Abstract
The invention discloses a surface crystal boundary modification method for improving corrosion resistance of a sintered Nd-Fe-B magnet and a product prepared by the method, and aims to solve the problems as follows: when the sintered Nd-Fe-B magnet is protected by adopting a surface protective plating layer, the production cost of the magnet is greatly increased while environmental pollution is caused; the surface plating layer is relatively poor in binding force; and when the sintered Nd-Fe-B magnet is protected by element alloying, a magnetic dilution effect is caused and the magnetic property is reduced. According to the surface crystal boundary modification method adopted by the invention, alloy powder R<x>M<y> is used as surface modification crystal boundary alloy of the sintered Nd-Fe-B magnet; and through aging treatment, a high-potential element M is dispersed to a surface crystal boundary region of the magnet through a crystal boundary Nd-rich phase to perform surface crystal boundary modification and to form the high-potential and high-chemical-stability surface crystal boundary. By adoption of the surface crystal boundary modification method, the corrosion resistance of the Nd-Fe-B magnet can be obviously improved, the waste of the R<x>M<y> alloy powder can be reduced, the raw material utilization rate is improved, the surface plating layer is not required, the production cost is lowered, and the problems of poor binding force, air bubbles, cracks, and falling off existing in the surface plating layer can be effectively avoided.
Description
Technical field
The present invention relates to the modified field of permanent magnet material field, especially permanent magnet material, specially a kind of raising sintered Nd-
The crystal boundary modified method in surface and its product of preparation of Fe-B magnet corrosion resistances.
Background technology
Nd-Fe-B magnets as most widely used Rare Earth Functional Materials, with excellent magnetic property, its remanent magnetism and maximum
Magnetic energy product has reached respectively the 97% of theoretical value and more than 93%, is referred to as " magnetic king ".Through development for many years, sintered Nd-Fe-
B magnets have become requisite material in social and economic construction and people's daily life, be widely used in Aero-Space,
The every field such as electromotor, electronic computer, automobile, communication, medical apparatus and instruments.
Sintered nd-fe-b magnet is mainly by hard magnetic Nd2Fe14 principal phases and weak magnetic richness Nd crystal boundary phase compositions.Wherein, firmly
The chemical property of magnetic Nd2Fe14 principal phase is relatively stable, but the chemical property of weak magnetic richness Nd Grain-Boundary Phases is very active, is corrosion
The preferential position of generation.At present, the poor corrosion resistance of sintered nd-fe-b magnet has become its wide variety of maximum restriction
Factor.
The corrosion of sintered nd-fe-b magnet is broadly divided into：Electrochemical corrosion and chemical attack two types.Wherein, electrification
The power for learning corrosion mostlys come from the difference in Electrode Potential of principal phase and Grain-Boundary Phase.The atomic percent of Nd is typically accounted in rich-Nd phase
The chemical property of about 80%, Nd is very active, and its outer-shell electron is very easy to lose, cause its standard electrode potential it is very low (-
2.431 V)；And Nd2Fe14 principal phases are then relatively stable；Due to two-phase coexistent, the galvanic element of larger electrode potential difference is constituted.
Meanwhile, the shared volume fraction in magnet of rich-Nd phase be less than 10%, therefore, primary anode, the knot of big negative electrode are defined in magnet
Structure.In corrosive medium, the rich-Nd phase of anode can preferentially be corroded and dissolve, so as to cause coming off and magnetic device for main phase grain
The failure of part.
Further, since crystal boundary Nd has active chemical property, its can and air in oxygen and water reaction, reaction process with
Temperature, humidity and pressure have substantial connection.Research finds that rich-Nd phase and the oxygen reaction of magnet surface generate Nd2O3, then along
The opposite magnet internal extended of crystal boundary.In the case where there is water to participate in, rich Nd Grain-Boundary Phases react with H2O, and reaction can generating portion hydrogen
Gas, rare earth is inhaled and volumetric expansion can occur after hydrogen, so as to cause principal phase granule atomization to come off.
In recent years, with Oversea wind power generation, the support developed rapidly with national policy of hybrid vehicle, to high magnetic
The demand of performance improved corrosion performance magnet will be increasing, while also will propose to the corrosion resistance and service life of magnet
Higher requirement.
In order to improve the corrosion resistance of sintered nd-fe-b magnet, researcher is mainly started with terms of two, and one is in magnet
Plated surface protective coating, two is to improve the intrinsic corrosion resistance of magnet.The former mainly passes through isolation magnet and corrosive environment, so as to rise
To the effect of protection magnet.The latter starts with from the Grain-Boundary Phase of magnet, and by changing magnet composition and microstructure Grain-Boundary Phase is improved
Electrode potential and chemical stability, reaching improves the purpose of magnet corrosion resistance.
Business sintered nd-fe-b magnet is generally using sides such as plating metal, chemical plating metal, electrophoretic coating and bonderizing
Method, in sintered magnet plated surface last layer protective layer, for isolating magnet and corrosive environment, so as to extend the use longevity of magnet
Life.And the method for improving the intrinsic corrosion resistance of magnet includes：Element alloyed and based on pairing gold process crystal boundary reconstruct etc.
Method.Element alloyed referring to is preparing the dispensing link of Nd-Fe-B magnets, by adjusting component formula, in original composition
Middle one or several metals of addition, alloy or compound, by steps such as common melting, rejection tablets, prepare sintered Nd-Fe-B
Magnet.Many researchers have studied the oligo-element alloying such as Al, Co, Cu, Ga, P, Cr, Ti, Zr, Pb, to improve the resistance to of magnet
Corrosive nature.These elements can generate relatively stable crystal boundary with Nd, the Fe in Grain-Boundary Phase or B element generation chemical reaction
Phase, suppresses corrosion and dissolving of the Grain-Boundary Phase in corrosive environment, so as to prevent the failure come off with magnetic device of main phase grain.
Although magnet and the corrosive environment isolation in the external world can be effectively improved the corrosion resistance of magnet by surfacecti proteon coating
Can, but coating can greatly increase the production cost of magnet, and cause environmental pollution, while overlay coating also exist adhesion compared with
Difference, and it is cracking, bubble and the risk for coming off.The element alloyed corrosion resistance that can to a certain extent improve magnet
Can, but addition element can be partially into Nd2Fe14 principal phases, cause magnetic diluting effect, reduce the magnetic property of magnet.
For this purpose, in the urgent need to a kind of new method, to solve the above problems.
The content of the invention
The present invention goal of the invention be：During for being protected sintered nd-fe-b magnet using surfacecti proteon coating,
The production cost of magnet can be greatly increased, environmental pollution is caused, and overlay coating adhesion is poor, and it is element alloyed for burning
When knot Nd-Fe-B magnets are protected, magnetic diluting effect can be caused, reduce the problem of magnetic property, there is provided one kind improves sintered Nd-Fe-B
The crystal boundary modified method in surface and its product of preparation of magnet corrosion resistance.The present invention adopts low melting point, the conjunction of high stability
, used as the modified grain boundary alloys in surface of sintered nd-fe-b magnet, the modified alloy of design is with higher electrode for bronze end RxMy
Current potential and chemical stability, both carry out the Ageing Treatment of certain hour at a suitable temperature, allow high potential element M to pass through
Crystal boundary rich-Nd phase is diffused into the surface grain boundary area of magnet, and it is crystal boundary modified to carry out surface, and forms high potential, high chemical stability
Surface Grain-Boundary Phase.Using the present invention, the corrosion resistance of Nd-Fe-B magnets can be significantly improved, reduce RxMy alloy powders
Waste, improve raw material availability, exempt overlay coating, save production cost, the adhesion for being prevented effectively from overlay coating presence is poor,
Bubble, the problem for ftractureing and coming off.
To achieve these goals, the present invention is adopted the following technical scheme that：
A kind of crystal boundary modified method in surface for improving sintered nd-fe-b magnet corrosion resistance, comprises the steps：By eutectic
Point, the alloy powder RxMy of high stability are coated in sintered nd-fe-b magnet surface, atmosphere Ageing Treatment are carried out, so as in Nd-
Fe-B magnet surfaces form protective layer；
The R be lanthanide series metal, M be high standard electrode potential metal, x for R atomic percentage, y for M atomic percentage, x
It is 5 ~ 80 with y's and for 100, x.
Atmosphere Ageing Treatment is carried out, high potential element M is made inside surface grain boundary decision to Nd-Fe-B magnets, Nd- is improved
The electrode potential and chemical stability of Fe-B magnet surface crystal boundaries.
The fusing point of the RxMy is below 900 DEG C.
The particle diameter of the alloy powder RxMy is 0.1-100 μm.
The R is one or more in La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, and the M is in Cu, Ni, Fe, Co
One or more.
First Nd-Fe-B magnets are carried out into surface polishing, cleaning, after removing Nd-Fe-B magnet surface powder, greasy dirt, then will
Alloy powder RxMy is coated on sintered nd-fe-b magnet surface.
Alloy powder RxMy is made into slurry, and slurry is coated in into sintered nd-fe-b magnet surface.
The temperature of atmosphere Ageing Treatment is 300-900 DEG C, and the time is 0.5-10 hours, and protective atmosphere is noble gases.
The noble gases are argon.
Using the product prepared by the aforementioned crystal boundary modified method in surface for improving sintered nd-fe-b magnet corrosion resistance.
Crystal boundary reconstruct is to be distributed to prepare the crystal-boundary phase alloy of main-phase alloy and high potential using pairing gold process, and is prepared
The method of sintered magnet, can design the composition of grain boundary alloys according to designer's wish.In recent years, researcher passes through surface crystal boundary
It is modified to be diffused into magnet surface Grain-Boundary Phase to improve the magnetocrystalline anisotropy field of Grain-Boundary Phase by the oxide containing heavy rare earth, fluoride
With the coercivity of magnet.
Applicant's research finds that crystal boundary rich-Nd phase can become the passage of diffusion into the surface, and the research is using low melting point, height
The alloyed powder of current potential carries out the crystal boundary modified sintered nd-fe-b magnet corrosion resistance that improves in surface and provides feasibility in theory.It is brilliant
Boundary's reconstruct can make to be distributed in Grain-Boundary Phase in high stability element set, improve the electrode potential of Grain-Boundary Phase, reduce principal phase and crystal boundary
The difference in Electrode Potential of phase, improves magnet corrosion resistance.Based on this, the present invention provides a kind of sintered nd-fe-b magnet that improves and resists
The crystal boundary modified method in surface and its product of preparation of corrosive nature.
The present invention is modified using the alloy powder RxMy of low melting point, high stability as the surface of sintered nd-fe-b magnet
Grain boundary alloys, the modified alloy of design has higher electrode potential and chemical stability, and both are carried out at a suitable temperature
The Ageing Treatment of certain hour, allows high potential element M that the surface grain boundary area of magnet is diffused into by crystal boundary rich-Nd phase, carries out table
Face is crystal boundary modified, and forms the surface Grain-Boundary Phase of high potential, high chemical stability.The present invention can reduce and Nd2Fe14 principal phases
Difference in Electrode Potential, reduces electrochemical corrosion driving force, hence it is evident that improve the corrosion resistance of magnet.Meanwhile, the alloyed powder of the present invention
End can reuse, and reduce the waste to material.In addition, the crystal boundary modified method in the surface of the present invention can exempt plated surface
Layer, saves production cost, and the adhesion for being prevented effectively from overlay coating presence is poor, bubble, the problem for ftractureing and coming off.
In the method, Nd-Fe-B magnets through surface polish and pickling processes, without obvious powder and greasy dirt after, complete pre-
Process, it is standby.Again the alloy powder RxMy of low melting point, high stability is coated in into pretreated sintered nd-fe-b magnet table
Face, carries out atmosphere Ageing Treatment, makes the high potential element M in RxMy inside surface grain boundary decision to Nd-Fe-B magnets, improves
The electrode potential and chemical stability of Nd-Fe-B magnet surface crystal boundaries.In RxMy alloys, R be lanthanide series metal La, Ce, Pr, Nd,
One or more in Sm, Gd, Tb, Dy, Ho, M is one or more in high standard electrode potential Ni metal, Ni, Fe, Co.x
With the atomic percentage that y is respectively R and M, 5≤x≤80,20≤y≤95.The fusing point of alloy RxMy is less than 900 DEG C, powder
Granularity is 0.1-100 μm.
In the present invention, the alloy powder RxMy of low melting point, high stability is coated in into the side on sintered nd-fe-b magnet surface
Method includes：1）Nd-Fe-B magnets are embedded in alloy powder RxMy, 2）Alloy powder RxMy is made after slurry, it is uniform to apply
In magnet surface.When carrying out Ageing Treatment, using noble gases argon as protective atmosphere, the timeliness in 300-900 DEG C of temperature
Process 0.5-10 hours.
In sum, the present invention relates to a kind of improve sintered NdFeB（Nd-Fe-B）The surface of magnet corrosion resistance is brilliant
Boundary's method of modifying.The present invention by the alloyed powder RxMy of low melting point, high stability by being coated in sintered nd-fe-b magnet surface simultaneously
Appropriate Ageing Treatment is carried out, makes alloying element inside surface grain boundary decision to magnet, magnet surface crystal boundary is modified,
Greatly reduce the potential difference of rich Nd Grain-Boundary Phases and Nd2Fe14 principal phases, i.e. electrochemical corrosion driving force.
Jing is determined, and the corrosion potential of product prepared by the present invention in 3.5 wt.% sodium-chloride water solutions is higher than -0.75V,
At 120 DEG C, the weight loss for corroding in the environment of 2 atmospheric pressure and 100% relative humidity 96 hours is less than 0.7mg/cm2.Experiment knot
Fruit shows that the surface by low melting point of the present invention, high stability alloy powder RxMy is crystal boundary modified, the anti-corruption of Nd-Fe-B magnets
Corrosion can be significantly improved.This shows that the crystal boundary modified method in surface of the present invention can significantly improve the anticorrosive of magnet
Performance, extends magnet service life.
Specific embodiment
All features disclosed in this specification, or disclosed all methods or during the step of, except mutually exclusive
Feature and/or step beyond, can combine by any way.
Any feature disclosed in this specification, unless specifically stated otherwise, can be equivalent or with similar purpose by other
Alternative features are replaced.I.e., unless specifically stated otherwise, each feature is an example in a series of equivalent or similar characteristics
.
Embodiment 1
（1）Prepare low melting point, high potential alloy
According to Nd-Co binary alloy phase diagrams, the eutectic composition that atomic percent is Nd64Co36 is selected as surface modified alloy,
Its fusing point is 566 DEG C.During melting ingredient, the quality of Nd is higher than the 1-3% of required quality, to supplement fusion process in Nd wave
Send out loss.In fusion process, argon protection, and melt back 3-5 time are kept, to ensure that composition is uniform.Melting is uniform
Alloy block is placed in the glove box of argon gas atmosphere, carries out coarse crushing, and to granularity 500 μm are less than, and obtains powder body.By the powder body for obtaining
Load ball grinder in the lump with appropriate isopropanol protection liquid, ball milling 30 hours, drum's speed of rotation is 300 rpms, is obtained
Ball milling slurry.
（2）Pretreatment Nd-Fe-B magnets
Commercial sintered nd-fe-b magnet surface is polishing to into light, and pickling degreasing is carried out with dilute sulfuric acid, be put into argon glove box
In, it is standby.
（3）Interface modification
The ball milling slurry obtained after ball milling is coated uniformly on into pretreated sintered nd-fe-b magnet surface, after a period of time,
Slurry forms one layer of encasement in magnet surface, and sintered nd-fe-b magnet has been coated by low melting point, high stability alloy powder
Into.Afterwards, the Nd-Fe-B magnets of alloyed powder heat treatment 5 hours at 550 DEG C will have been coated, surface has been carried out crystal boundary modified.Treat magnetic
After body cooling, the residual powder on surface is cleaned out with hairbrush, obtain final product product.
To carrying out electro-chemical test and weightless test test through the crystal boundary modified magnet in Nd64Co36 alloyed powders surface.Knot
Fruit shows that corrosion potential of the magnet in 25 DEG C, 3.5wt.% sodium chloride solutions is -0.723V, higher than the corrosion of untreated samples
Current potential -0.957V.At 120 DEG C, the weight loss corroded 96 hours in the environment of 2 atmospheric pressure and 100% relative humidity is magnet
0.47mg/cm2。
Embodiment 2
（1）Prepare low melting point, high potential alloy
According to Nd-Ni binary alloy phase diagrams, the eutectic composition that atomic percent is Nd65Ni35 is selected as surface modified alloy,
Its fusing point is 540 DEG C.During melting ingredient, the quality of Nd is higher than the 1-3% of required quality, to supplement fusion process in Nd wave
Send out loss.In fusion process, keep argon protection and repeatedly, melting 3-5 time, to ensure that composition is uniform.Melting is uniform
Alloy block is placed in the glove box of argon gas atmosphere, carries out coarse crushing, and powder body is obtained less than 500 μm to granularity.By the powder body for obtaining
Load ball grinder in the lump with appropriate isopropanol protection liquid, afterwards ball milling 30 hours, drum's speed of rotation is 300 rpms,
Obtain ball milling slurry.
（2）Pretreatment Nd-Fe-B magnets
Commercial sintered nd-fe-b magnet surface is polishing to into light, and pickling degreasing is carried out with dilute sulfuric acid, be put into argon glove box
In, it is standby.
（3）Interface modification
The ball milling slurry obtained after ball milling is coated uniformly on into pretreated sintered nd-fe-b magnet surface, after a period of time,
Slurry forms one layer of encasement in magnet surface, and sintered nd-fe-b magnet magnet is coated by low melting point, high stability alloy powder
Complete.Afterwards, the Nd-Fe-B magnets of alloyed powder heat treatment 4 hours at 530 DEG C will have been coated, surface has been carried out crystal boundary modified.Treat
After magnet cooling, the residual powder on surface is cleaned out with hairbrush, obtain final product product.
To carrying out electro-chemical test and weightless test test through the crystal boundary modified magnet in Nd65Ni35 alloyed powders surface.Knot
Fruit shows that corrosion potential of the magnet in 25 DEG C, 3.5wt.% sodium chloride solutions is -0.715V, higher than the corrosion of untreated samples
Current potential -0.957V.At 120 DEG C, the weight loss corroded 96 hours in the environment of 2 atmospheric pressure and 100% relative humidity is magnet
0.41mg/cm2。
Embodiment 3
（1）Prepare low melting point, high potential alloy
According to Dy-Co binary alloy phase diagrams, the eutectic composition that atomic percent is Dy60Co40 is selected as surface modified alloy,
Its fusing point is 745 DEG C.During melting ingredient, the quality of Dy is higher than the 1-3% of required quality, to supplement fusion process in Dy wave
Send out loss.In fusion process, argon protection, and melt back 3-5 time are kept, to ensure that composition is uniform.Melting is uniform
Alloy block is placed in the glove box of argon gas atmosphere, carries out coarse crushing, and to granularity 500 μm are less than, and obtains powder body.By the powder body for obtaining
Load ball grinder in the lump with appropriate isopropanol protection liquid, ball milling 30 hours, drum's speed of rotation is 300 rpms, is obtained
Ball milling slurry.
（2）Pretreatment Nd-Fe-B magnets
Commercial sintered nd-fe-b magnet surface is polishing to into light, and pickling degreasing is carried out with dilute sulfuric acid, be put into argon glove box
In, it is standby.
（3）Interface modification
The ball milling slurry obtained after ball milling is coated uniformly on into pretreated sintered nd-fe-b magnet surface, after a period of time,
Slurry forms one layer of encasement in magnet surface, and sintered nd-fe-b magnet has been coated by low melting point, high stability alloy powder
Into.Afterwards, the Nd-Fe-B magnets of alloyed powder heat treatment 8 hours at 730 DEG C will have been coated, surface has been carried out crystal boundary modified.Treat magnetic
After body cooling, the residual powder on surface is cleaned out with hairbrush, obtain final product product.
To carrying out electro-chemical test and weightless test test through the crystal boundary modified magnet in Dy60Co40 alloyed powders surface.Knot
Fruit shows that corrosion potential of the magnet in 25 DEG C, 3.5wt.% sodium chloride solutions is -0.708V, higher than the corrosion of untreated samples
Current potential -0.957V.At 120 DEG C, the weight loss corroded 96 hours in the environment of 2 atmospheric pressure and 100% relative humidity is magnet
0.37mg/cm2。
Embodiment 4
（1）Prepare low melting point, high potential alloy
Research shows that Nd30Co65Cu5 alloys carry out crystal boundary reconstruct to sintered nd-fe-b magnet and can form stable in grain boundaries
Grain-Boundary Phase and effectively improve the corrosion resistance of magnet.We select atomic percent to change as surface for Nd30Co65Cu5
Property alloy, its fusing point be 605 DEG C.In melting ingredient, the quality of Nd is higher than the 1-3% of required quality, to supplement fusion process
The volatilization loss of middle Nd.In fusion process, argon protection, and melt back 3-5 time are kept, to ensure that composition is uniform.Will be molten
Refine uniform alloy block to be placed in the glove box of argon gas atmosphere, carry out coarse crushing, to granularity 500 μm are less than, obtain powder body.Will
To powder body and appropriate isopropanol protection liquid load ball grinder, ball milling 30 hours in the lump, drum's speed of rotation be 300 turns per point
Clock, obtains ball milling slurry.
（2）Pretreatment Nd-Fe-B magnets
Commercial sintered nd-fe-b magnet surface is polishing to into light, and pickling degreasing is carried out with dilute sulfuric acid, be put into argon glove box
In, it is standby.
（3）Interface modification
The ball milling slurry obtained after ball milling is coated uniformly on into pretreated sintered nd-fe-b magnet surface, after a period of time,
Slurry forms one layer of encasement in magnet surface, and sintered magnet is covered to complete by low melting point, high stability alloy powder.Afterwards,
The magnet of alloyed powder heat treatment 6 hours at 590 DEG C will have been coated, surface has been carried out crystal boundary modified.After magnet cooling, hairbrush is used
The residual powder on surface is cleaned out, product is obtained final product.
To carrying out electro-chemical test and weightless test survey through the crystal boundary modified magnet in Nd30Co65Cu5 alloyed powders surface
Examination.As a result show, corrosion potential of the magnet in 25 DEG C, 3.5wt.% sodium chloride solutions is -0.702V, higher than untreated samples
Corrosion potential -0.957V.Magnet corrodes the weightlessness of 96 hours at 120 DEG C, in the environment of 2 atmospheric pressure and 100% relative humidity
Measure as 0.25mg/cm2.
The invention is not limited in aforesaid specific embodiment.The present invention is expanded to and any in this manual disclosed
New feature or any new combination, and the arbitrary new method that discloses or the step of process or any new combination.
Claims (10)
1. it is a kind of improve sintered nd-fe-b magnet corrosion resistance the crystal boundary modified method in surface, it is characterised in that including as follows
Step：The alloy powder RxMy of low melting point, high stability is coated in into sintered nd-fe-b magnet surface, is carried out at atmosphere timeliness
Reason, so as to form protective layer in Nd-Fe-B magnet surfaces；
The R be lanthanide series metal, M be high standard electrode potential metal, x for R atomic percentage, y for M atomic percentage, x
It is 5 ~ 80 with y's and for 100, x.
2. the crystal boundary modified method in surface of sintered nd-fe-b magnet corrosion resistance, its feature are improved according to claim 1
It is to carry out atmosphere Ageing Treatment, makes high potential element M inside surface grain boundary decision to Nd-Fe-B magnets, improves Nd-Fe-
The electrode potential and chemical stability of B magnet surface crystal boundaries.
3. the crystal boundary modified method in surface of sintered nd-fe-b magnet corrosion resistance, its feature are improved according to claim 1
It is that the fusing point of the RxMy is below 900 DEG C.
4. the crystal boundary modified method in surface of sintered nd-fe-b magnet corrosion resistance, its feature are improved according to claim 3
It is that the particle diameter of the alloy powder RxMy is 0.1-100 μm.
5. the crystal boundary modified side in surface that sintered nd-fe-b magnet corrosion resistance is improved according to any one of claim 1-4
Method, it is characterised in that the R be La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho in one or more, the M be Cu, Ni,
One or more in Fe, Co.
6. the crystal boundary modified side in surface that sintered nd-fe-b magnet corrosion resistance is improved according to any one of claim 1-5
Method, it is characterised in that first Nd-Fe-B magnets are carried out into surface polishing, cleaning, remove Nd-Fe-B magnet surface powder, greasy dirt
Afterwards, then by alloy powder RxMy it is coated on sintered nd-fe-b magnet surface.
7. the crystal boundary modified side in surface that sintered nd-fe-b magnet corrosion resistance is improved according to any one of claim 1-6
Method, it is characterised in that alloy powder RxMy is made into slurry, and slurry is coated in into sintered nd-fe-b magnet surface.
8. the crystal boundary modified side in surface that sintered nd-fe-b magnet corrosion resistance is improved according to any one of claim 1-7
Method, it is characterised in that the temperature of atmosphere Ageing Treatment is 300-900 DEG C, and the time is 0.5-10 hours, and protective atmosphere is indifferent gas
Body.
9. the crystal boundary modified method in surface of sintered nd-fe-b magnet corrosion resistance, its feature are improved according to claim 8
It is that the noble gases are argon.
10. changed using the surface crystal boundary that sintered nd-fe-b magnet corrosion resistance is improved described in aforementioned any one of claim 1-9
Property method prepare product.
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