JPH11219809A - Rare-earth magnet with high resistance coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rear-earth magnet with high resistance coating, in which insulation performance can be made high, and corrosion resistance and abrasion resistance can be made satisfactory, even if a thin film which is 25 μm or less in which high dimensional precision can be obtained. SOLUTION: An abrasion resistance coating which is 1-5 μm is formed as a first layer, and high resistance coating the specific resistance value of which is 10<5> Ω.cm or more which is 2-20 μm is formed as a second layer on the surface of this rare-earth magnet with a high resistance coating. In this case, at least one kind of metallic nitride film selected from among Ti, Zr, Hf, V, Nb, Ta, and Cr, or one kind of metallic film selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Ni, and Cu, or two or more kinds of alloy film selected from among Ti, Zr, Hf, V, Nb, Ta, Cr, Ni, and Cu are used for the first layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rare earth magnet with a high resistance coating having a coating on a part or the entire surface thereof, and more particularly, a corrosion resistance coating on the surface and a high resistance coating formed thereon. Accordingly, the present invention relates to a rare earth magnet with a high-resistance coating having both high insulation properties and excellent corrosion resistance and wear resistance.

[0002]

2. Description of the Related Art For example, neodymium (Nd) -iron (Fe)
So-called rare earth magnets such as boron (B) based magnets and samarium (Sm) -cobalt (Co) based magnets have excellent magnetic properties and are used in all fields. However, this magnet is inferior in corrosion resistance because it is mainly composed of iron or the like and contains a phase rich in rare earth elements which is easily corroded in crystal structure. Rare earth magnets are electrochemically corroded from the surface due to the presence of a slight amount of acid, alkali, and moisture, and the magnets are corroded to generate rust. Accompanying this, the magnet performance deteriorates.

In order to improve the corrosion resistance of rare earth magnets having poor corrosion resistance, various surface treatments such as nickel plating, aluminum chromate, epoxy resin coating, and electrodeposition coating have been conventionally applied to the surface of the magnet.

However, these surface treatment methods require a film thickness of 20 μm or more even in an environment of use in the atmosphere, and cannot be applied to precision parts requiring strict dimensional accuracy.
In addition, pre-processing and post-processing are required, which requires processing time and cost.

In the case where a conductive film such as nickel plating is formed, if there is at least one pinhole, a local battery is formed due to a potential difference from a member, and corrosion proceeds.
Further, in a use environment where abrasion resistance is required, it cannot be used because the film hardness is low.

[0006] Also, since the rare earth magnet has a low resistance value,
A local battery is easily formed. Therefore, when used in places where insulation is required, an epoxy resin, which is an insulating material, is applied to the surface of the material.However, since the paint is sprayed or dipped in the paint, a uniform shape is required for complicated shapes. It is difficult to obtain high dimensional accuracy because the film thickness is not obtained, and there is also a problem in the treatment of a solvent (for example, a thinner) used for a paint.

Further, since the resin allows moisture to permeate, the insulation resistance value changes in the surrounding environment, and further, the resin is softened in an operating environment of 150 ° C. or more, and cannot be used. Even a polyimide resin having high heat resistance has a problem that the heat resistance temperature is 300 ° C. or lower and the abrasion characteristics are poor.

[0008]

As described above, in the conventional nickel plating and painting methods, which are surface treatments, the insulation, corrosion resistance, and abrasion resistance are insufficient. It could not be applied to precision parts or complicated shapes having strict dimensional accuracy because the thickness was 20 μm or more. Further, it could not be used in places where abrasion resistance was required due to low film hardness.

Accordingly, the present invention provides a rare earth magnet with a high resistance coating having a high film thickness of 25 μm or less in order to obtain high dimensional accuracy, and having a high insulation property and excellent corrosion resistance and wear resistance even with such a thin film. The purpose is to provide.

[0010]

According to the present invention, there is provided a rare earth magnet provided with a high resistance coating having a high resistance coating as a first layer and a high resistance coating as a second layer. It is characterized by the following.

As the first layer, Ti, Zr, Hf, V,
A nitride film of at least one metal selected from Nb, Ta, and Cr, or Ti, Zr, Hf, V,
1 selected from Nb, Ta, Cr, Ni, and Cu
Seed metal film, or Ti, Zr, Hf, V, Nb,
Two or more alloy films selected from Ta, Cr, Ni, and Cu are preferable, and the film thickness is preferably 1 to 5 μm.

The thickness of the nitride film, metal film or metal alloy film formed as the first layer is preferably 1 to 5 μm. 1
If the thickness is less than μm, there are many pinholes and sufficient environmental barrier properties cannot be obtained. On the other hand, if the thickness exceeds 5 μm, the stress of the film is increased, so that peeling and cracking occur and the cost is reduced, and the overall film thickness is increased and the dimensional accuracy is deteriorated.

For example, if the first layer film is a CrN film or a TiN film which is a metal nitride film, a 1 μm thick film may have a pinhole ratio of 0.1 to 0.2% and a Cr metal film. If
It becomes 0.01-0.02%, and there is a sufficient environmental barrier property.

The high-resistance film formed as the second layer preferably has a specific resistance value of 10 ⁵ Ω · cm or more, and preferably has a thickness of 2 to 20 μm. Specific resistance value 1
If it is less than 0 ⁵ Ω · cm, a local battery is easily formed in the case of a pinhole, and the progress of corrosion becomes faster. If the film thickness is less than 2 μm, there are many pinholes in the film, and there is a possibility of conducting electricity with the underlying film.
This is because the abrasion resistance is insufficient. On the other hand, the film thickness is 20 μm
This is because, if it exceeds, the overall film thickness becomes large and the dimensional accuracy deteriorates.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The members used in the present invention include Nd-Fe-B based magnets, Sm-Co based magnets, Sm-
Fe-N based magnets, sintered magnets thereof, bond magnets (resin magnets) bonded with nylon resin, epoxy resin or the like can be used. It is desirable that the film is not magnetized when forming the film. This is because a magnetized member affects plasma and evaporated particles when ion plating is performed, which affects the film thickness distribution and film quality.

Before the formation of the film, it is desirable to remove stains on the member surface with alcohol or the like. Particularly, when a film is formed on a sintered magnet, a gas is generated from the inside of the magnet when heated during the film formation, and the magnet surface may be soiled or the adhesion may be reduced. The vacuum degassing step can be performed, for example, by evacuating the vacuum chamber to 10 ^-4 Torr or less, and then heating the member to 300 to 700 ° C. with a heater. In the vacuum degassing step, it is desirable not to raise the temperature abruptly so that the member is not cracked by thermal shock.

In order to clean the surface of the member, heat the member, and improve the adhesion between the member and the film, it is preferable to perform a bombarding treatment. As a method of the bombardment treatment, for example, Ar gas is introduced into a vacuum chamber, a bias voltage of -500 V or more is applied to a member, and the treatment is performed for one minute or more.

In order to obtain a higher adhesion, it is preferable to subsequently carry out a metal bombarding treatment. In the metal bombarding process, for example, a metal serving as a raw material of the first layer is melted,
The evaporated particles are ionized, and the bias voltage is applied to the member by -50.
Apply 0 V or more and process for 1 to 5 minutes. It is not preferable to perform the heating for 5 minutes or more because the surface of the member becomes rough.

The first layer and the second layer can be formed by known PVD (physical vapor deposition), but in the present invention, the reactive ion platen in which the first layer and the second layer can be easily coated continuously. Is preferred. The ionization method may be any of known methods such as arc discharge, glow discharge, hollow cathode discharge, and high frequency discharge.

The specific resistance formed on the second layer is 10 ⁵ Ω · cm.
Al ₂ O ₃ , SiO ₂ , Mg
Examples include oxide films such as O and ZrO ₂ , and nitride films such as AlN and Si ₃ N ₄ , which can be appropriately selected according to the required resistance value of the application site.

When the above-mentioned oxide film is formed on the second layer, oxygen gas can be used as a reaction gas. When oxygen gas is used as the reaction gas, the rare-earth magnet of the member is easily oxidized. Therefore, it is desirable to select a nitride film or a metal film as the first layer to avoid contact with oxygen.

[0022]

(Example 1) A 10 × 10 × 5 mm non-magnetized Nd—Fe—B based sintered magnet was used as a member, and after ultrasonic cleaning, it was placed 35 cm away from the evaporating material in a vapor deposition apparatus. It was attached to face. As the evaporating material of the first layer, an ingot of a Cr-35 at% Ti alloy was used, and as the evaporating material of the second layer, granular Al ₂ O ₃ (dissolved and pulverized product) having a diameter of 2 to 3 mm was used. Filled in hearth.

As an evaporation apparatus, an ion plating apparatus manufactured by Shinko Seiki, AIF-850SB was used. In this apparatus, a 270 degree deflection electron gun manufactured by JEOL Ltd. is used for melting the evaporating material, and ionization generates plasma between the evaporating material and an ionization electrode provided on the evaporating material.

After setting the members and the evaporating material,
The inside of the vacuum chamber was evacuated to 1 × 10 ⁻⁵ Torr, heated to 300 ° C. by an internal heater, and kept for 2 hours. Next, 0.03 Torr of Ar gas was introduced, −800 V was applied to the members, and ion bombardment was reduced to 1%.
Performed for 0 minutes.

Next, a Cr-35 at% Ti alloy was irradiated with an electron beam of 10 kV and -200 mA to dissolve it. The use of this alloy increases the ionization rate because more thermoelectrons are generated than when Cr metal is used as the evaporating material, and allows only Cr to be selectively evaporated due to a difference in vapor pressure.

The Cr is evaporated by the above method, and -8 is added to the member.
A bias voltage of 00 V was applied, and metal bombardment was performed for 2 minutes with Cr ions. Subsequently, the bias voltage was lowered to -200 V, and a Cr metal film was formed for 12 minutes.
Next, the evaporating material was changed to Al ₂ O ₃ and the electron beam was changed to 10 k.
V, -400 mA irradiation, oxygen was introduced until the pressure reached 5 × 10 ⁻⁴ Torr, and a film was formed for 25 minutes.

The thickness of the obtained Cr metal film of the first layer was 1.1 μm, and the thickness of the Al ₂ O ₃ film of the second layer was 4.3 μm. The film thickness distribution was uniform within the measurement error range.

A cross-cut was made on the two-layer film formed on the rare earth magnet, and a tape adhesion test was carried out. As a result, the film was not damaged and the film was not peeled off with a cutter knife. The surface film hardness was HV800 in Vickers hardness. As a result of measuring the volume resistance with an LCR meter, 1 × 10
The resistance was ¹⁵ Ω · cm. Since the volume resistivity of the bulk material at room temperature is 10 ¹⁴ Ω · cm or more, it was possible to substantially achieve the bulk material resistivity with the thin film.

This rare earth magnet with a high resistance coating has no rust even when exposed to 48H during spraying with 5% salt water, and has high corrosion resistance to the extent that spot rust is generated on the surface even after 96H. Was.

Example 2 5 × 10 ⁻⁴ at the time of forming the first layer
The same processing as in Example 1 was performed except that a nitrogen gas was introduced up to Torr and a film was formed for 30 minutes. The resulting coating is Cr
The N film had a uniform thickness of 2.1 μm.

Next, an Al ₂ O ₃ film was formed in the same manner as in Example 1 for 120 minutes. The film thickness was uniformly 17.5 μm. Even when the underlayer was a CrN film, no peeling or cracking occurred between the member and the Al ₂ O ₃ film. The volume resistance was the same as in Example 1.

(Embodiment 3) An MgO film of 8 μm in the second layer
The same processing as in Example 2 was performed except that the film was formed. MgO used as a vapor deposition material was obtained by crushing a single crystal and increasing the size to 3 × 3 × 1 mm.

The coating obtained was HV5 in Vickers hardness.
It was 31. Like the Al ₂ O ₃ film, no peeling or cracking was observed, and no peeling was observed in the tape adhesion test. The volume resistance value was 5 × 10 ⁶ Ω · cm. Also,
When a salt spray test was performed in the same manner as in Example 1, no rust was generated even after 48 hours.

(Conventional Example 1) When an Nd-Fe-B based sintered magnet without any surface treatment was left in the air, iron rust was generated at 24H.

(Conventional Example 2) Nd-Fe same as Conventional Example 1
In a corrosion resistance test in which 5% salt water was sprayed on a magnet obtained by applying a conventional surface treatment of nickel plating to a 20-μm nickel-based sintered magnet, rust was generated on the surface at 48H.

(Conventional Example 3) The same members as in Example 1 were subjected to ultrasonic cleaning with ethanol, then washed with an alkaline cleaning agent to which a water-soluble rust inhibitor was added, and further washed with water. Then, 10%
Pickling was performed with a hydrochloric acid solution, followed by washing with water. afterwards,
While maintaining a current density of 4 A / cm ² , the sample was immersed in a Ni plating bath for 10 minutes, the sample was changed, and further immersed in a Ni plating bath for 10 minutes to form a Ni film of 20 μm.
The Ni plating film had a Vickers hardness of 530 and was electrically conductive.

(Conventional Example 4) An epoxy resin base material: a curing agent: a diluted thinner was mixed at a ratio of 1: 1: 2, and the mixture was applied by a spray gun. The average film thickness was 23 μm, and a film thickness distribution of 5 μm was generated at the thin and thick portions.

(Conventional Example 5) Nd-Fe same as Conventional Example 1
5 CrN film on the -B sintered magnet by ion plating
As a result of performing a 5% salt spray test for 72 hours, rust was generated on the entire surface.

Comparative Example 1 A CrN film having a thickness of 0.5 μm
A film was formed in the same manner as in Example 1 except that an l ₂ O ₃ film was formed to a thickness of 1 μm. As a result, the volume resistance was 1 × 10 ¹² Ω · cm. When the same salt spray test as in Example 1 was performed,
After 8 hours, it was rusting.

Comparative Example 2 A film was formed in the same manner as in Example 1 except that a CrN film was formed to a thickness of 7 μm, and peeling was observed at the corners of the magnet in a 5% salt spray test.

[0041]

According to the present invention, it is possible to provide a rare-earth magnet with a high-resistance coating, which has high insulating properties even with a thin film of 25 μm or less, which can obtain high dimensional accuracy, and is excellent in corrosion resistance and wear resistance.

Claims (4)

[Claims] 1. A wear-resistant coating as a first layer on the surface,
A rare earth magnet with a high resistance coating having a high resistance coating formed as a second layer. 2. Ti, Zr, H as a first layer on the surface.
a nitride film of at least one metal selected from f, V, Nb, Ta, and Cr is formed in a thickness of 1 to 5 μm;
2 high-resistance films with a specific resistance of 10 ⁵ Ω · cm or more
Rare earth magnet with high resistance coating formed to 20 μm. 3. On the surface, Ti, Zr, H as a first layer
One type of metal film selected from f, V, Nb, Ta, Cr, Ni, and Cu is formed in a thickness of 1 to 5 μm, and a high-resistance film having a specific resistance of 10 ⁵ Ω · cm or more is formed as a second layer. 20
A rare earth magnet with a high resistance coating formed in μm. 4. Ti, Zr, H as a first layer on the surface
Two or more alloy films selected from f, V, Nb, Ta, Cr, Ni, and Cu are formed in a thickness of 1 to 5 μm, and a high-resistance film having a specific resistance of 10 ⁵ Ω · cm or more is formed as a second layer. ~
Rare earth magnet with a high resistance coating, formed 20 μm.