JPH06116711A - Method for forming alumina film - Google Patents

Abstract

(57) [Summary] [Object] To provide a film forming method of a transparent alumina film which has excellent adhesion and is free from bumping particles and has a smooth surface and a hard surface. [Composition] Alumina prepared by melting was used as a vapor deposition material on the metal surface by the ion plating method, and 1 x was used as the first layer.
Alumina was vapor-deposited at a pressure lower than 10 ^-4 Torr, and alumina was vapor-deposited with oxygen introduced as a reaction gas so that the second layer was 1 × 10 ^-4 Torr to 1 × 10 ^-3 Torr. The alumina film formation rate is maintained at 10 μm / hr or less through the layer and the second layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wear-resistant transparent protective film such as a decorative plating and a method for depositing alumina for electrical insulation on a metal material.

[0002]

2. Description of the Related Art Alumina films are used as protective films for ornaments and recording media, and also as protective films for electrical insulation. The sputtering method is used to form the protective film of the recording medium, while the ion plating method, which has a high film formation rate, is used in the case of ornaments and the like. As a method for forming an alumina film on the surface of a metal such as a decorative article, there is, for example, JP-A-57-73.
A reactive ion plating method is known in which metallic aluminum is vaporized in oxygen as shown in 178. However, this method has a problem that the range of film forming conditions is narrow, and if the condition is slightly deviated from the conditions, the film is discolored so that transparency cannot be obtained, or unreacted aluminum is deposited to impair electrical insulation. On the other hand, JP-A-63-62
As shown in 868, an alumina film having stable quality is formed by a high frequency ion plating method using alumina as a vapor deposition material.

[0003]

If an alumina film is formed by an ion plating method using alumina as an evaporation material, it is possible to obtain a hard and excellent alumina film having excellent transparency and electric insulation. Method has low adhesion,
There was a problem that it easily peeled off during use. Further, if sintered alumina is used as the evaporation material alumina, a gas during melting is likely to be generated, and bumping occurs to cause alumina particles to adhere to the surface of the substrate, resulting in surface roughness. Therefore,
An object of the present invention is to provide a film forming method of an alumina film which has excellent adhesion and is free from bumping particles, that is, has a smooth and hard surface.

[0004]

Means for Solving the Problems As a means for solving the above problems, the present invention uses alumina particles produced by melting as a vapor deposition material when forming an alumina coating film on a metal surface by an ion plating method, 1x as the first layer
Alumina was vapor-deposited at a pressure lower than 10 ^-4 Torr, and then the pressure in the vacuum chamber as the second layer was 1 × 10 ^-4 Torr.
Alumina is vapor-deposited in a state where oxygen is introduced as a reaction gas so as to be up to 1 × 10 ⁻³ Torr, and the deposition rate of the alumina film is maintained at 10 μm / hr or less through the first layer and the second layer. There are features.

[0005]

Function: The hardness, adhesion, and transparency of the alumina coating formed by using alumina as an evaporation material depend on the film forming conditions. The pressure of oxygen introduced into the film formation as a reaction gas is 1 × 10 ⁻⁴ T
If it is lower than orr, oxygen in the alumina coating becomes insufficient due to the decomposition of alumina of the evaporating material, resulting in a coating deviating from the chemical composition, and the hardness of the alumina coating is Vvs hardness of Hv70.
It becomes 0 or less. At Hv of 700 or less, the hardness is about the same as that of a metal material having high hardness. H above 1 × 10 ^-4 Torr
A film of v700 to Hv1100 is obtained. Oxygen pressure 1
When it is not less than × 10 ^-3 Torr, the tungsten filament of the electron gun used for melting the evaporation material and the substrate heater are rapidly deteriorated, which is not desirable.

[0006] The adhesion of the alumina coating formed on the SKH51 and SUS304 substrates is measured by the scratch tester (LSRH).
Was measured by manufacturing REVETEST), as opposed to the oxygen pressure dependency of hardness, the oxygen pressure is 10N or more adhesion was obtained with less than 1 × 10 ^-4 Torr, less than 10N in 1 × 10 ^-4 Torr or more I found that.

Therefore, in order to improve the adhesion without lowering the hardness of the coating film, first, 1 × 10 ^{−4 is formed} as the first layer.
Alumina was vapor-deposited at a pressure lower than Torr without introducing oxygen, and then oxygen was further added to the layer as 1 × 10 ^−4.
If alumina is vapor-deposited in a state of being introduced at Torr to 1 × 10 ⁻³ Torr, a transparent and transparent alumina film having a coating hardness Hv of 700 or more and an adhesive force of 10 N or more and having excellent adhesiveness can be formed. it can. Even if the oxygen pressure fluctuates within the above pressure range during the formation of the second layer, the characteristics of the obtained coating remain unchanged.

As the metal, case hardening steel such as S15C, S
Structural steel such as 45C, spring steel such as SUP10, SU
Bearing steel such as J2, nitrided steel such as SASM1, SKD6
Steel for hot working such as, steel for cold working such as SKD11,
Various steels such as high speed tool steel such as SKH51, heat resistant steel such as SUS301, and corrosion resistant acid resistant steel such as SUS410 can be mentioned.

Alumina as a vapor deposition material includes sintered alumina particles produced by sintering and dissolved alumina particles produced by melting. When sintered alumina is used, gas is generated from inside the alumina particles during film formation. It is apt to occur, and bumping occurs, alumina particles adhere to the substrate surface, and the substrate surface is roughened. If molten alumina is used, bumping can be suppressed considerably, and an alumina vapor deposition substrate having a smooth vapor deposition surface can be obtained. However, even if dissolved alumina is used, if the film formation rate is too fast, bumping will be a problem, so the film formation rate must be 10 μm / hr or less.

The ion plating method used in the present invention may be any method that uses a method involving melting of the evaporation material such as resistance heating or electron gun heating as the evaporation material evaporation method, and ionization of the evaporation material. Any of the methods such as arc discharge, glow discharge, and high frequency discharge may be used.

The bias voltage applied to the substrate is 0 to -50.
It is better to set it to 0V or less. When the electrical insulation of the alumina film is not so required, the adhesion force can be improved by applying a bias voltage, but when high electrical insulation is required, a large bias voltage is applied to cause the alumina film to break down. I will wake you up.

The temperature during film formation can be appropriately selected according to the type of substrate and the application, and can be controlled by various heaters.

[0013]

【Example】

(Example 1) As an example of the present invention, using a high frequency ion plating method and using alumina prepared by a melting method as a vapor deposition material, a hardness change and an adhesion force of an alumina film vapor-deposited on a SKH51 material due to oxygen pressure The changes are shown in FIGS. 1 and 2, respectively. Oxygen pressure is 1 × 10 ^-4 Tor
If it is lower than r, the hardness of the alumina coating is Vickers hardness H.
v700 or less. A coating of Hv700 to Hv1100 can be obtained at 1 × 10 ⁻⁴ Torr or more. Adhesion of the alumina coating, as opposed to the oxygen pressure dependency of hardness, the oxygen pressure is 10N or more adhesion was obtained with less than 1 × 10 ^-4 Torr, becomes less than 10N in 1 × 10 ^-4 Torr or more Will end up.

SKH51 material was used as the substrate to be coated. After washing this substrate with an organic solvent, it was set in a vacuum reaction tank and the pressure in the vacuum reaction tank was evacuated to a vacuum of 1 × 10 ⁻⁵ Torr or more. After reaching the target vacuum degree, 300 ℃
Heat for 1 hour and then Ar ion bombard treatment for 1 hour
It went for 0 minutes. As the vapor deposition material, alumina particles having a particle diameter of 1 mm to 3 mm prepared by a melting method were used. By applying accelerated electrons of 9 kV-300 mA to this vapor deposition source to heat and melt it to evaporate alumina, the first layer is vapor-deposited for 30 minutes without introducing oxygen as a reaction gas. afterwards,
20 cc of oxygen was introduced, the pressure was set to 3 × 10 ⁻⁴ Torr, and the second layer was vapor-deposited for 30 minutes. The evaporation material is not ionized by high frequency through the first layer and the second layer, and the bias voltage is not applied to the substrate. The temperature during film formation was 300 ° C., and the film formation rate was 3 μm / hr.

By the film formation under the above conditions, a 3 μm alumina coating film was obtained. The hardness of this coating is Hv950,
The adhesion was 16 N, and a transparent alumina film having high hardness and high adhesion was obtained. The maximum roughness R _max of the coating is 0.3.
It was 2 μm.

(Example 2) An alumina film was formed under the same conditions as in Example 1 except that a high frequency of 200 W was applied to the ionization electrode in order to ionize the evaporation material during the film formation of the first and second layers. did. The thickness of the obtained film was 2.8 μm,
The hardness of the coating was Hv1050 and the adhesion was 17N.

(Example 3) An alumina film was formed under the same conditions as in Example 1 except that a bias voltage of -100 V was applied to the substrate during the formation of the first layer. The film thickness of the obtained film is 3.
The coating hardness was Hv970 and the adhesion was 20 N.

Comparative Example 1 An alumina film was formed in the same manner as in Example 1 except that alumina particles produced by sintering were used as the evaporation material. The thickness of the obtained film is 3.4 μm
The hardness is Hv 930, the adhesion is 16 N, which is almost the same as the case of using fused alumina, but the surface roughness is R.
_{At a maximum of} 0.9 μm, a large number of particles that were thought to be attached by bumping were observed on the surface.

(Comparative Example 2) An alumina film was formed under the same conditions as in Example 1 except that the pressure of oxygen in the film formation of the second layer was 7 × 10 ^-5 Torr. The thickness of the obtained film is 3.5.
In μm, the hardness was Hv630 and the adhesion was 15N.

Comparative Example 3 An accelerating voltage of 9 kV-300 mA was applied to the evaporation source through the film formation of the first layer and the second layer,
Example 1 except that the film forming rate of the film was 13 μm / hr.
An alumina film was formed under the same conditions as above. Coating hardness is Hv
880, adhesion was 15 N, but surface roughness is R _max
At 1.2 μm, a large number of particles that were thought to be attached by bumping were observed on the surface.

[0021]

As described above, by using the film forming method according to the present invention, it is possible to form a transparent alumina film having a hard surface, excellent adhesion, and a smooth surface on a metal material. It is possible to greatly improve the wear resistance of the above.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between oxygen pressure and coating hardness.

FIG. 2 is a diagram showing the relationship between oxygen pressure and adhesion.

Claims (1)

[Claims] 1. When forming an alumina coating on a metal surface by an ion plating method, (1) alumina particles produced by dissolution are used as a vapor deposition material, and (2) 1 × 10 ⁻⁴ Torr as a first layer. Alumina is deposited at a lower pressure, and (3) after that, the pressure in the vacuum chamber as the second layer is 1 ×.
Alumina is vapor-deposited in a state where oxygen is introduced as a reaction gas so as to be 10 ⁻⁴ Torr to 1 × 10 ⁻³ Torr,
(4) A method for forming an alumina film, characterized in that the film forming rate of the alumina film is maintained at 10 μm / hr or less through the first layer and the second layer.