JP2000040610A - Film coated rare earth magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the anti-corrosion of rare earth magnet, by a method wherein an Si film is formed by ion plating process on the surface of a rare earth magnet as a base metal so as to form the second layer made of an Si oxide material on this Si film. SOLUTION: The first layer made of an Si layer as for a base material is formed by ion plating process on the surface so as to form the second layer made of an Si oxide film on the first layer. The base material is either an Nd-Fe-B base sintered magnet or a bond magnet, etc., coupled with nylon. At this time, it is recommended that the surface pollution of a rare earth magnet as a base material is removed using alcohol, etc., before forming a film while in the case of the sintered magnet as the base material, and it is preferable that the vacuum degasification is performed since there is a possibility of either producing gas from inside or the decline in adherence. Furthermore, it is recommended that film thickness of the Si film formed as the first layer is 0.5-2.0 μm and that as the second layer is 1-5 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated rare earth magnet, and more particularly, to a coated rare earth magnet having an improved corrosion resistance by forming a Si film and a Si oxide film on the surface of the rare earth magnet by an ion plating method. About magnets.

[0002]

2. Description of the Related Art Neodymium (Nd) -iron (Fe) -boron (B) magnets have excellent magnetic properties and are used in various fields. However, this magnet is disadvantageous in that it is inferior in corrosion resistance because it is mainly composed of iron and contains a neodymium-rich phase which is easily corroded in crystal structure. That is, due to the presence of a slight amount of acid, alkali, and moisture, corrosion progresses electrochemically from the surface, the magnet is corroded, rust is generated, and magnet performance is deteriorated.

In order to improve the corrosion resistance of a neodymium-iron-boron magnet, various surface treatments such as nickel plating, aluminum chromate, epoxy resin coating, and electrodeposition coating have been applied to the surface of the magnet. However, in order to maintain the corrosion resistance of the magnet by the coating formed by these surface treatments, the thickness of the coating needs to be 20 μm or more even in the use environment in the atmosphere. For this reason, the magnet formed with the film by the above-mentioned surface treatment has problems that the magnetic properties are deteriorated and that it cannot be applied to precision parts requiring strict dimensional accuracy or parts having complicated shapes. In order to be applicable to the above components without deteriorating the magnetic properties, it is necessary to suppress the thickness of the coating to 10 μm or less. In the above-mentioned surface treatment, post-processing is also required, which takes time and costs.

In addition, there is a problem that the resin coating cannot be used in a use environment of 150 ° C. or higher, and the use of a polyimide resin having high heat resistance can be used at 300 ° C. or lower.

In addition to the above treatment, there is a method of coating a ceramic film such as a TiN film by a wet plating method such as an ion plating method. However, no matter how thick the film is, there is a problem in corrosion resistance due to the presence of pinholes. was there.

[0006]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention provides a rare earth magnet which is excellent in corrosion resistance even with a coating having a thickness of 10 .mu.m or less formed by an ion plating method whose processing step is simpler than a wet plating method. The purpose is to:

[0007]

According to the present invention, there is provided a coated rare earth magnet according to the present invention, comprising:
A layer is formed, a second layer made of a Si oxide film is formed on the first layer, and the thickness of the first layer is 0.5 to 2 μm.
m, the second layer is 1.0 to 5 μm, and the sum of the first and second layers is 10 μm or less.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The base material in the present invention is Nd-F
eB sintered magnets, bonded magnets bonded with nylon, and the like. A first layer made of a Si film is formed on the surface of the base material by an ion plating method, and a second layer made of a Si oxide film is formed on the first layer.

It is desirable that the surface of the base metal rare earth magnet be cleaned with alcohol or the like before the film is formed. Further, when the base material is a sintered magnet, it is desirable to perform vacuum degassing because there is a possibility that a gas will be generated from the inside by heating during the formation of the coating and the magnet surface may be soiled, or the adhesion may decrease. In the vacuum degassing process, the inside of the vacuum chamber is 10 ^−4.
After exhausting to Torr or lower, the base material is heated to 300 to 7 with a heater.
It can be carried out by heating to 00 ° C. It is also desirable not to raise the temperature rapidly so that the base material does not crack due to thermal shock.

It is desirable that the base material before film formation is not magnetized. This is because, when magnetized, the plasma and the evaporating particles are affected when the ion plating process is performed, and the film thickness distribution and film quality are unfavorable.

In order to clean the surface of the base material, heat the base material, and improve the adhesion between the base material and the coating, a bombardment treatment is performed. In the bombardment process, an Ar gas is introduced into a vacuum chamber, and a bias voltage of -500 V or more is applied to the base material.
What is necessary is just to process for 1 minute or more.

In order to obtain a higher adhesion, it is preferable to carry out a metal bombarding process after the bombarding process. The metal bombardment process is performed on the S layer formed on the first layer.
It is sufficient to melt the raw material of the i-film, ionize the evaporated particles, apply a bias voltage of −500 V or more to the base material, and perform the treatment for 1 to 5 minutes. A treatment longer than 5 minutes is not preferable because the surface of the base material becomes rough.

It is preferable to use a Si-10 at% Ta alloy as a raw material of a film formed on the first layer and the second layer. Although Si alone can be used as an evaporating material, bumping can be suppressed by adding Ta. Ta
Is about 8 orders of magnitude lower than the vapor pressure of Si, so that Si will evaporate preferentially.

The raw material of the film formed on the second layer is SiO 2
₂ may be used. However, in this case, the first layer and the second layer cannot be continuously processed unless an apparatus having a plurality of hearths is used.

The first layer and the second layer can be formed by PVD (physical vapor deposition), but a reactive ion plating method is preferred, in which the first layer and the second layer can be formed continuously and easily. . The method of ionization is a known arc discharge,
Any method such as glow discharge, hollow cathode discharge, and high frequency discharge may be used.

When forming the second Si oxide film, oxygen gas can be used as a reaction gas. Since rare earth magnets are easily oxidized, it is necessary to form a Si film as the first layer to avoid contact with oxygen.

The thickness of the Si film formed as the first layer is
0.5 to 2.0 μm is desirable. When the thickness is less than 0.5 μm, the adhesion and oxidation prevention are insufficient, and when the thickness is more than 2.0 μm, the overall film thickness becomes large and the dimensional accuracy is deteriorated.

The thickness of the Si oxide film formed as the second layer is preferably 1 to 5 μm. If it is less than 1 μm, there are many pinholes, so that sufficient corrosion resistance cannot be obtained.
Exceeding the range results in poor dimensional accuracy and is disadvantageous in terms of productivity and economy.

The first-layer Si film and the second-layer Si oxide film usually have pinholes because they are formed by a known ion plating method. However, since the Si oxide film is excellent in water repellency, the liquid hardly penetrates into the pinhole, and is excellent in corrosion resistance.

[0020]

EXAMPLES Example 1 A non-magnetized Nd—Fe—B-based sintered magnet having a size of 10 × 10 × 5 mm was used as a base material.
After ultrasonic cleaning, this was set so as to face a position 35 cm away from the evaporating material. Si-10at% for evaporation material
A Ta alloy ingot was used and filled into a Cu hearth. As an evaporation apparatus, an ion plating apparatus manufactured by Shinko Seiki, "AIF-850SB" was used. In this apparatus, a 270 ° deflection electron gun manufactured by JEOL is used for melting the evaporating material, and ionization is performed by generating plasma between the ionizing electrode provided on the evaporating material and the evaporating material. .

After setting the base material and the evaporating material, the inside of the vacuum chamber was evacuated to 1 × 10 ⁻⁵ Torr, heated to 300 ° C. by the internal heater, and kept for 2 hours. Next, 0.03 Torr of Ar gas was introduced, −800 V was applied to the base material, and ion bombardment was performed for 30 minutes. Next, an electron beam of 10 kV-500 mA is applied to S
The i-10at% Ta alloy was irradiated and melted. Si was evaporated by the above method, a bias voltage of -800 V was applied to the base material, and metal bombardment was performed for 2 minutes with Si ions.

Subsequently, the bias voltage was lowered to -200 V, and Si metal was coated for 2 minutes. Next, oxygen was introduced at 50 SCCM, and coating was performed for 12 minutes.

The obtained film thickness was 1.1 μm for the first-layer Si metal film and 3.5 μm for the second-layer Si oxide film. The coated magnet was placed in a 5% salt spray for 96 hours.
Even when exposed to H, there was no rust and high corrosion resistance.

Example 2 SiO ₂ was used as an evaporator for the _second Si oxide film, and 5 × 1 was used during coating.
The same processing as in Example 1 was performed except that oxygen gas was introduced to 0 ^-4 Torr and coating was performed for 30 minutes.

The obtained film thickness was 1.0 μm for the first Si metal film and 2.3 μm for the second Si oxide film. As a result of the same corrosion resistance test as in Example 1, equivalent results were obtained.

(Conventional Example 1) When a Nd-Fe-B sintered magnet without any surface treatment was left in the air, iron rust was generated at 24H. A magnet with nickel plating of 20 μm, which is a conventional surface treatment, was
In the corrosion resistance test by spraying with salt water, 48H rust was generated on the surface.

(Conventional Example 2) When an epoxy resin base material: a curing agent and a diluted thinner are mixed in a ratio of 1: 1: 2 and applied by a spray gun, the average thickness is 23 μm, and the thin and thick portions are thick. At this point, a film thickness distribution of 5 μm was generated.

Comparative Example 1 A Ni—Fe—B sintered magnet was coated with a TiN film having a thickness of 5 μm by an ion plating method, and exposed to 96H in a 5% salt water spray. As a result, rust was generated on the entire surface.

[0029]

According to the present invention, it is possible to provide a rare earth magnet which can provide sufficient corrosion resistance with a film thickness of 20 μm or less, has high dimensional accuracy, and can be manufactured.

Claims (3)

[Claims] 1. A first layer made of a Si film is formed on a surface of a rare earth magnet as a base material by an ion plating method.
A coated rare earth magnet in which a second layer made of an i-oxide film is formed on the first layer. 2. A first layer made of a Si film is formed on the surface of a base metal rare earth magnet by an ion plating method.
a second layer comprising an i-oxide film is formed on the first layer, and the thickness is 0.5 to 2 μm for the first layer and 1.0 to 5 μm for the second layer. magnet. 3. A first layer made of a Si film is formed on a surface of a base material rare earth magnet by an ion plating method.
a second layer made of an i-oxide film is formed on the first layer, and the thickness is 0.5 to 2 μm for the first layer, 1.0 to 5 μm for the second layer, and The sum of the layer and the second layer is 10μ
m.