JPH10106816A - Anticorrosive permanent magnet and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase anticorrosive property and adhesiveness with an underlying layer, by forming a Ti1-x Alx N film layer having a specified thickness via an Al film having a specified thickness on a Ti film having a specified thickness and being formed on a surface of a R-Fe-B permanent magnet body in which a main phase is made of a tetragonal phase. SOLUTION: On a cleaned surface of a R-Fe-B permanent magnet body in which a main phase is made of a tetragonal phase, a Ti film having a thickness of approximately 0.1 to 3.0μm is formed by a thin film deposition method. Then, an Al film having a thickness of approximately 0.1 to 5μm is formed on the Ti film. In addition, a Ti1-x Alx N film layer (where 0.03<x<0.70) having a thickness of approximately 0.5 to 10μm is formed on the Al film. By thus causing the Al film layer to exist as an intermediate layer, the Al film layer functions as a sacrifice layer with respect to a permanent magnet and the Ti film of the underlying layer. Thus, adhesiveness with the Ti film is significantly improved, and excellent anticorrosive property and wear resistance are realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an R-Fe-based alloy having a high magnetic property, excellent adhesion, and a corrosion-resistant coating having excellent corrosion resistance, acid resistance, alkali resistance and abrasion resistance.
The present invention relates to a B-based permanent magnet, and more particularly to a corrosion-resistant permanent magnet having extremely stable magnet properties with little rust in a salt spray test and little deterioration from initial magnet properties, and a method for producing the same.

[0002]

2. Description of the Related Art First, using rare earths, which are abundant in resources, mainly Nd and Pr, B and Fe as main components, do not contain expensive Sm and Co, and are the highest among conventional rare earth cobalt magnets. As a new high-performance permanent magnet that greatly exceeds the characteristics,
-Fe-B permanent magnets have been proposed (Japanese Patent Laid-Open No. 59-5978).
46008, JP-A-59-89401).

The Curie point of the above magnet alloy is generally 30
0 ° C. to 370 ° C., but having a higher Curie point by substituting part of Fe with Co.
B-based permanent magnets (JP-A-59-64733, JP-A-59-64733)
-132104), and has a Curie point equal to or higher than that of the R-Fe-B-based rare earth permanent magnet containing Co and a higher (BH) max, and improves its temperature characteristics, particularly iHc. Therefore, as a rare earth element (R), a Co-containing R centered on a light rare earth such as Nd or Pr.
By including at least one of heavy rare earths such as Dy and Tb in a part of R of the Fe-B based rare earth permanent magnet, iHc can be further increased while retaining a very high (BH) max of 25 MGOe or more. Improved Co-containing R
-Fe-B rare earth permanent magnet proposed (Japanese Patent Laid-Open No. 60-34)
005).

However, the permanent magnet made of the R-Fe-B-based magnetic anisotropic sintered body having excellent magnetic properties has an active compound structure containing a rare earth element and iron as its main components. When incorporated in a magnetic circuit,
Oxide generated on the surface of the magnet causes a reduction in output of the magnetic circuit and variations between the magnetic circuits, and there is a problem of contamination of peripheral devices due to dropout of the surface oxide.

[0005]

Therefore, the above R-F
In order to improve the corrosion resistance of e-B permanent magnets, a permanent magnet having a corrosion-resistant metal plating layer coated on the surface of the magnet body by electroless plating or electrolytic plating (Japanese Patent Publication No. 3-74012)
No.) has been proposed.

In the above-mentioned plating method, since the permanent magnet body is a sintered body and porous, an acidic solution or an alkaline solution in the pre-plating treatment remains in the pores, and may corrode with aging. Due to the poor chemical resistance of the body, there has been a problem that the magnet surface is corroded during plating, resulting in poor adhesion and corrosion resistance. In addition, even when the corrosion-resistant plating was provided, the initial magnet characteristics were degraded by 10% or more in the corrosion resistance test at a temperature of 60 ° C. and a relative humidity of 90% for 100 hours, and the magnet characteristics were very unstable. .

Therefore, in order to improve and improve the corrosion resistance of the R—Fe—B permanent magnet, TiN, AN is applied to the magnet surface by ion plating, ion sputtering or the like.
(1) It has been proposed that a Ti coating be applied to improve and improve corrosion resistance (Japanese Patent Publication No. 5-15043).

[0008] The TiN film has poor adhesion due to differences in the thermal expansion coefficient, ductility, etc., besides the crystal structure of the R-Fe-B magnet, and the Ti or Al film has good adhesion and corrosion resistance. However, there are drawbacks such as low wear resistance, and to solve this, Ti-Fe-B based permanent magnet
It is proposed to apply a laminated film of TiN and
No. 9919). However, since the Ti film and the TiN film have different crystal structures, thermal expansion coefficients, ductility, and the like, there is a problem that the adhesion is poor and peeling or the like occurs, leading to a reduction in corrosion resistance.

The present invention has an object to improve the abrasion resistance and corrosion resistance with excellent adhesion to an R-Fe-B-based permanent magnet base, and particularly to a temperature of 34 ° C. to 36 ° C. using a 5% neutral NaCl solution. In the salt spray test, deterioration from the initial magnet characteristics is minimized even in a long-time test, and stable high magnet characteristics,
An object of the present invention is to provide an R-Fe-B-based permanent magnet having abrasion resistance and corrosion resistance, and a method for producing the same.

[0010]

Means for Solving the Problems The present inventors can improve the corrosion resistance, especially the time until rusting by spraying salt water with a temperature of 34 ° C. to 36 ° C. and 5% neutral NaCl solution for a long time. R-F with excellent magnet adhesion and stable magnet properties due to the corrosion resistance and abrasion resistance of the applied corrosion resistant coating
For the purpose of e-B permanent magnet, Ti
As a result of various studies on the _1-x Al _x N film forming method, the potential of the R-Fe-B based magnet as a whole when the underlying film is the Ti film proposed above or only the Al film is Ti
Alternatively, since there is a locally very “base” part such as the Nd part in the magnet, which is more noble than Al, the salt spray test of the severe corrosion resistance test starts through a slight pinhole of the TiN film. It was found that rust easily occurred.

The inventors have further studied the method of forming a Ti _1-x Al _x N film. As a result, a Ti film layer was first formed on the surface of the permanent magnet body as a base of the Ti _1-x Al _x N film.
Then, by providing an Al coating layer, Al is electrochemically slightly "base" compared to Ti, so that the Al coating layer acts as a sacrificial coating on the Ti coating layer, and Ti ₁ Even if corrosion occurs from a slight pinhole in the _-x Al _x N film, the underlying Ti film and the surface layer Ti _1-x Al _x N do not penetrate through the under film at a stretch to the base magnet body.
As long as an Al film is present as an intermediate layer between the films, the R-Fe-B permanent magnet coated on the Ti film of the underlayer is protected, and a Ti _1-x Al _x N film is formed on the Al film. By doing so, the interface becomes Ti _{1- ■} Al _■ N _■
A composite film of i, Al, and N is formed, and the Ti _{1- ■} Al 2 _■
N _■ composition, thickness, substrate temperature, varies with the bias voltage, film formation speed, Ti _1-x Al x N composition, etc., Ti
_The composition is such that Ti and N continuously increase toward the _1-x Al _x N interface, whereby the Al film and the Ti _1-x A
The inventors have found that the adhesion to the l _x N coating can be remarkably improved, and have completed the present invention.

That is, according to the present invention, a Ti coating having a thickness of 0.1 μm to 3.0 μm formed on the surface of an R—Fe—B-based permanent magnet having a tetragonal phase as a main phase is formed on a Ti coating having a thickness of 0.1 μm to 3.0 μm. 1μ
0.5 μm to 10 μm in thickness through an Al coating of m to 5 μm
m Ti _1-x Al _x N (where 0.03 <x <0.70)
It is a corrosion-resistant permanent magnet having a coating layer.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention provides an R-Fe-B-based permanent magnet having a tetragonal phase as a main phase, having a cleaned surface.
By a thin film forming method, Ti having a thickness of 0.1 μm to 3.0 μm is used.
After forming the film, a film thickness of 0.1 μm to 5 μm is formed on the Ti film.
m Al film is formed, and a film thickness of 0.5 μm is formed on the Al film.
m to ₁₀ μm of Ti _1-x Al _x N (0.03 <x <
0.70) A coating layer is formed. An example of a method for manufacturing a corrosion-resistant permanent magnet will be described in detail below.

1) For example, after evacuating the vacuum vessel to an ultimate vacuum of 1 × 10 ⁻³ pa or less using an arc ion plating apparatus, an Ar gas pressure of 10 pa and −500 is used.
R-Fe-B by surface sputtering with Ar ions at V
Clean the surface of the system magnet body. Next, Ar gas pressure 0.1p
a, Ti of a target is evaporated by a bias voltage of -80 V, and a Ti coating layer having a thickness of 0.1 μm to 3.0 μm is formed on the surface of the magnet body by an arc ion plating method.

2) Next, the target Al is evaporated by an Ar gas pressure of 0.1 pa and a bias voltage of -50 V, and a thickness of 0.1 μm to 5 μm is formed on the Ti coating layer by an arc ion plating method. An Al coating layer is formed.

3) Subsequently, as a target, alloy Ti
_{Using 1-y} Al _y (however, 0.03 <y <0.80), the magnet temperature of the substrate was kept at 250 ° C., the N ₂ gas pressure was 3 pa,
Under the condition of a bias voltage of -120 V, a specific thickness of Ti _1-x Al _x N (0.03 <x <0.7
0) Form a coating layer.

In the present invention, a Ti film layer, an Al film layer, and a Ti _1-x A film adhered to the surface of an R—Fe—B-based permanent magnet body.
As a method for forming the l _x N coating layer, a known thin film forming method such as an ion plating method or a vapor deposition method can be appropriately selected. However, for reasons such as the denseness, uniformity, and film forming speed of the film, the ion plating method is used. Method and an ion reaction plating method are preferred.

The temperature of the substrate magnet at the time of film formation is 200 ° C.
Preferably, the temperature is set at 500 ° C. If the temperature is lower than 200 ° C, the reaction adhesion with the substrate magnet is not sufficient, and if the temperature exceeds 500 ° C, the temperature difference from the normal temperature (-25 ° C) becomes large, and the cooling process after the treatment causes The temperature of the substrate magnet is set to 200 ° C. to 500 ° C., since the coating is cracked and partially peels off from the substrate.

In the present invention, the reason why the Ti coating thickness on the surface of the magnet body is limited to 0.1 μm to 3.0 μm is as follows.
If it is less than μm, the adhesion to the magnet surface is not sufficient, and
When the thickness exceeds μm, there is no problem effectively, but the cost of the underlayer is increased, which is not practical and not preferable. Therefore, the thickness of the Ti coating is set to 0.1 μm to 3.0 μm.

In the present invention, the reason why the thickness of the Al coating formed on the Ti coating is limited to 0.1 μm to 5 μm is that if it is less than 0.1 μm, it is difficult for Al to uniformly adhere to the surface of the Ti coating, and The effect as a film is not sufficient, and if it exceeds 5 μm, there is no problem. However, it is not preferable because the cost of the intermediate layer is increased, so that the thickness of the Al coating is set to 0.1 μm to 5 μm.

In addition, Ti _1-x Al _x N (however, 0.03 <
x <0.70) The reason for limiting the coating thickness to 0.5 μm to 10 μm is that if the coating thickness is less than 0.5 μm, the corrosion resistance and abrasion resistance of the Ti _1-x Al _x N coating are not sufficient, and if it exceeds 10 μm, the effect is increased. Although there is no problem in terms of production, it is not preferable because it causes an increase in manufacturing cost. In the Ti _1-x Al _x N coating,
The reason for limiting the value of x is that if it is less than 0.03, Ti _1-x A
l _x N film as the performance of the (corrosion, wear resistance) is not obtained, also because is not obtained improvement in performance beyond 0.70.

The rare earth element R used in the permanent magnet of the present invention
Accounts for 10 to 30 atomic% of the composition, but Nd,
At least one of Pr, Dy, Ho, and Tb; or La, Ce, Sm, Gd, Er, Eu, T
Those containing at least one of m, Yb, Lu, and Y are preferable. Also, usually one of R is sufficient,
In practice, a mixture of two or more kinds (mish metal, dymium, etc.) can be used for reasons such as convenience in obtaining. Note that R may not be a pure rare earth element, and may contain impurities which are unavoidable in production within the industrially available range.

R is an essential element in the above-mentioned permanent magnets. If it is less than 10 atomic%, the crystal structure becomes a cubic structure having the same structure as that of α-iron, so that high magnetic properties, especially high coercive force cannot be obtained. , More than 30 atomic%, the R-rich nonmagnetic phase increases, the residual magnetic flux density (Br) decreases, and a permanent magnet having excellent characteristics cannot be obtained. Therefore, R10 atomic% or more
A range of 30 atomic% is desirable.

B is an essential element in the above-mentioned permanent magnets. If it is less than 2 atomic%, the rhombohedral structure becomes the main phase, a high coercive force (iHc) cannot be obtained, and if it exceeds 28 atomic%, B becomes rich. Increase in non-magnetic phase, residual magnetic flux density (Br)
, The excellent permanent magnet cannot be obtained. Therefore, B is desirably in the range of 2 to 28 atomic%.

Fe is an essential element in the above permanent magnets. When the content is less than 65 at%, the residual magnetic flux density (Br) decreases, and when it exceeds 80 at%, a high coercive force cannot be obtained. % To 80 atomic%.
Further, substituting a part of Fe with Co can improve the temperature characteristics without impairing the magnetic characteristics of the obtained magnet. However, when the Co substitution amount exceeds 20% of Fe, conversely, It is not preferable because the magnetic properties deteriorate. When the substitution amount of Co is 5 atomic% to 15 atomic% in the total amount of Fe and Co, (Br) increases as compared with the case where the substitution is not performed, so that it is preferable to obtain a high magnetic flux density.

In addition to R, B, and Fe, the presence of unavoidable impurities in industrial production can be tolerated. For example, a part of B may be 4.0 wt% or less of C, 2.0 wt% or less of P, .0
By replacing at least one of S by wt% or less and Cu by 2.0 wt% or less with a total amount of 2.0 wt% or less, it is possible to improve the productivity and reduce the cost of the permanent magnet.

Further, Al, Ti, V, Cr, Mn, B
i, Nb, Ta, Mo, W, Sb, Ge, Sn, Zr,
At least one of Ni, Si, Zn, and Hf is R
-It can be added to the Fe-B-based permanent magnet material because it is effective for improving the coercive force and the squareness of the demagnetization curve, improving the productivity, and reducing the price. The upper limit of the addition amount is preferably in a range that satisfies the above condition, since Br needs to be at least 9 kG or more in order to make (BH) max of the magnet material 20 MGOe or more.

The permanent magnet of the present invention comprises a compound having a tetragonal crystal structure having an average crystal grain size in the range of 1 to 80 μm as a main phase, and a nonmagnetic phase (1% to 50% by volume). (Excluding the oxide phase). The permanent magnet according to the present invention exhibits a coercive force iHc ≧ 1 kOe, a residual magnetic flux density Br> 4 kG, and a maximum energy product (BH) m
ax indicates (BH) max ≧ 10 MGOe, and the maximum value reaches 25 MGOe or more.

[0029]

【Example】

Example 1 A known casting ingot was pulverized, finely pulverized, molded, sintered and heat-treated to obtain a magnet test piece having a composition of 15Nd-1Dy76Fe-8B and having a diameter of 12 mm and a thickness of 2 mm.
Table 1 shows the magnet characteristics.

The inside of the vacuum vessel is evacuated to 1 × 10 ⁻³ pa or less, and surface sputtering is performed for 20 minutes at an Ar gas pressure of 10 pa and −500 V to clean the surface of the magnet body.
An r gas pressure of 0.1 pa, a bias voltage of −80 V, a substrate magnet temperature of 280 ° C., a metal Ti as a target is formed by an arc ion plating method to form a 1 μm thick Ti coating layer on the surface of the magnet body.

After that, an Ar gas pressure of 0.1 pa, a bias voltage of -50 V, a substrate magnet temperature of 250 ° C., a metal Al as a target, and a 2 μm thick Al film were formed on the surface of the Ti film by arc ion plating. A coating layer was formed. Next, a substrate magnet temperature of 320 ° C. and a bias voltage −
A Ti _1-x Al _x N coating layer having a thickness of 2 μm was formed on the Al coating surface by arc ion plating at 100 V and 1 pa of N ₂ gas using an alloy Ti _0.45 Al _0.55 as a target. The composition of the resulting film was Ti _0.5 Al _0.5 N.

Then, after standing to cool, the obtained permanent magnet having a TiN coating on the surface was subjected to a salt spray test (JIS Z2371) under the conditions of a temperature of 35 ° C. and a 5% neutral NaCl solution, and the rusting time was measured. The results are shown in Table 2 together with the magnet characteristics.

Comparative Example 1 Using a magnet test piece having the same composition as in Example 1,
After forming a 3 μm-thick Ti coating layer on the magnet test piece under the same conditions as in Example 1, a Ti film having the same thickness (2 μm) was used under the same conditions as in Example 1.
After forming the _0.5 Al _0.5 N coating layer, a salt spray test was performed under the same conditions as in Example 1 and the rusting time was measured. The results are shown in Table 2 together with the magnet properties.

Comparative Example 2 An Al coating layer was formed to a thickness of 3 μm on the magnet body surface under the same conditions as in Example 1 using a magnet body test piece having the same composition as in Example 1, and then under the same conditions as in Example 1. , Ti _0.5 A of the same thickness
After forming the l _0.5 N coating layer, a salt spray test was conducted under the same conditions as in Example 1 to measure the rusting time. The results are shown in Table 2 together with the magnet properties.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

According to the present invention, after the surface of an R-Fe-B permanent magnet body is cleaned by an ion sputtering method or the like, a Ti film is formed on the surface of the magnet body by a thin film forming method such as an ion plating method. Further, after forming an Al film as an intermediate layer, a Ti _1-x Al _x N film is formed by a thin film forming method such as ion reaction plating in N ₂ gas, and the Al film layer is formed as the intermediate layer. In the presence of, it acts as a sacrificial coating on the permanent magnet body and the Ti coating of the underlying layer, significantly improving the adhesion between the Ti coatings, and the rusting time in the salt spray test of the severe corrosion resistance test. To extend corrosion resistance and wear resistance,
An R-Fe-B permanent magnet having stable magnet properties can be obtained.

Claims (2)

[Claims] 1. A film thickness of 0.1 μm to 3.0 μm formed on the surface of an R—Fe—B permanent magnet body whose main phase is a tetragonal phase.
A Ti _1-x Al _x N film having a thickness of 0.5 μm to 10 μm on a Ti film having a thickness of 0.1 μm to 5 μm through an Al film
(However, 0.03 <x <0.70) Corrosion-resistant permanent magnet having a coating layer. 2. A method for forming a thin film on a cleaned surface of an R—Fe—B permanent magnet body having a tetragonal phase as a main phase.
After forming a Ti film having a thickness of 0.1 μm to 3.0 μm, an Al film having a thickness of 0.1 μm to 5 μm is formed on the Ti film, and a Ti film having a thickness of 0.5 μm to 10 μm is formed on the Al film.
_A method for producing a corrosion-resistant permanent magnet which forms a _1-x Al _x N (0.03 <x <0.70) coating layer.