JPH06228754A - Formation of carbon coating film on metal substrate - Google Patents

Abstract

PURPOSE:To provide a forming method of a carbon film on a metal substrate by which a carbon coating film excellent in adhesion property can be efficiently formed on a metal substrate by low temp. CVD method. CONSTITUTION:After the surface of a metal substrate is plated with nickel, the surface is irradiated with radiation in a range to increase the temp. of the plating film to 200-600 deg.C. Then, a carbon coating film is deposited in a vapor phase by CVD method which thermally decomposes hydrocarbon gas on the irradiated surface. As for the radiation, Ir, visible or UV rays are preferably used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a carbon film on a metal substrate, which allows a carbon film having excellent adhesion to be uniformly coated on the surface of the metal substrate by a CVD operation at a relatively low temperature.

[0002]

2. Description of the Related Art Since carbon has excellent self-lubricating property as an intrinsic property, it has been widely used as a solid lubricant for a long time. The shape of carbon used as a lubricant is generally in the form of fine particles, but in order to impart lubricity to various members, means for forming a carbon coating layer on the surface of the target member Is effective. Therefore, there is a need for a technique for coating the surface of a metal material that occupies most of the mechanical member with carbon with good adhesion.

Conventionally, as a most typical coating technique for forming a carbon film, there is a CVD method (chemical vapor deposition method) in which a carbon layer is vapor-deposited on a substrate surface by thermally decomposing a hydrocarbon gas. Are known. However, CV
In order to efficiently deposit a carbon film by the D method, it is necessary to maintain the base material temperature at least around 800 to 1100 ° C. Therefore, for example, a material such as a metal having a coefficient of thermal expansion extremely different from that of carbon is used as the base material. And if
During cooling, a phenomenon occurs in which the formed carbon coating film peels off due to the difference in thermal expansion (thermal stress) between the materials. In addition, the metal base material itself may be deteriorated by heat, resulting in deterioration of material characteristics.

In order to solve such a problem of the CVD method, the plasma CVD in which the substrate temperature hardly rises
A method of forming a carbon film on a metal surface using the method (Japanese Patent Laid-Open No. 2-30755) has been proposed. However, plasma CVD has a drawback that the deposition rate for forming a film is extremely slow. Although this deposition rate can be increased by increasing the power density, the higher power density increases the energy consumption of the process and causes damage to the metal substrate.

In addition, in order to improve the adhesion between the metal base material and the carbon coating, a method for providing a composite intermediate layer of metal particles and carbon between them for the purpose of relaxing thermal stress (JP-A-59-59). (143498 gazette, JP-A-3-191065 gazette)
However, there is a problem that the manufacturing process becomes complicated and the production cost rises. Further, as a carbon coating means other than the CVD method, a thermosetting resin liquid having a high carbonization yield such as a phenol type or a furan type is applied to the surface of a metal base material, and the applied layer is baked and carbonized to be converted into a carbon layer. However, since the applied resin layer is greatly shrunk during carbonization, the peeling phenomenon is unavoidable.

The present inventor has applied nickel oxide to the surface of a metal base material as an effective means for forming a carbon coating on the surface of the metal base material with good adhesion by applying CVD. Has developed a method for depositing a carbon coating on the coated surface by thermal decomposition of hydrocarbon gas, and has already proposed it as Japanese Patent Application No. 4-271180. According to this carbon coating method, nickel oxide previously supported on the surface of the metal base material has a catalytic function, and by this action, good adhesion is obtained even in a low temperature CVD operation in which the holding temperature of the metal base material is 400 ° C. or lower. It becomes possible to form a carbon coating layer.

[0007]

As a result of repeated research on means for coating a metal base material with carbon capable of low-temperature CVD operation, the present inventors have formed a nickel plating layer on the surface of the metal base material which has been previously irradiated with radiation. After that, it was confirmed that when the CVD operation was applied, the carbon film could be coated with good adhesion in the substrate holding temperature range of about 400 ° C.

The present invention was developed on the basis of the above-mentioned findings, and an object thereof is a metal base material capable of efficiently forming a carbon coating film having excellent adhesion on the surface of a metal base material by a low temperature CVD method. Another object of the present invention is to provide a method for forming a carbon film on the substrate.

[0009]

The method for forming a carbon coating on a metal substrate according to the present invention for achieving the above object comprises:
After nickel-plating the surface of the metal substrate, the nickel-plated surface is irradiated with radiation in an energy range in which the surface temperature rises to 200 to 600 ° C., and then the radiation-coated surface is subjected to CVD by thermal decomposition of hydrocarbon gas. The constitutional feature is that the carbon coating layer is vapor-deposited through the intermediate layer.

The metal material used as the base material of the present invention is 600
Metals having a melting point of 0 ° C. or higher are used, and typically iron, copper or alloys thereof are used as the target substrate. There is no particular limitation on the plating method for forming the nickel coating on the surface of the metal substrate. Therefore, an ordinary electroplating method can be used, but for the purpose of the present invention, an electroless plating method by a commonly used building bath method is preferably applied.

CVD is applied to the nickel-plated surface thus formed.
Radiation is applied to enhance the catalytic activity that makes the carbon coating efficient by. The radiation that can be used is
Microwaves, infrared rays, visible rays, ultraviolet rays, X-rays, γ-rays and the like can be mentioned, but it is preferable to use infrared rays, visible rays or ultraviolet rays from the viewpoint of workability and safety. When the radiation is applied, the surface temperature of the nickel-plated surface is 2
It is necessary to perform in the energy range which rises to 00-600 degreeC. Irradiation with a surface temperature rise of less than 200 ° C. cannot sufficiently enhance the catalytic activity of the nickel plating layer, while irradiation with radiation over 600 ° C. causes the carbon coating formed in the subsequent CVD step to peel off, The radiant energy is too strong and causes a phenomenon such as damage to the metal substrate. In addition, there are no restrictions on the atmosphere during radiation irradiation, which may be air, vacuum, or an inert gas atmosphere, and the irradiation time is set appropriately in consideration of the energy density of the applied radiation and the degree of increase in surface temperature. To be done.

The metal base material having the nickel plating layer whose surface is irradiated with radiation is then set in a CVD furnace and heated, and a hydrocarbon gas is introduced into the furnace for thermal decomposition. As the hydrocarbon gas serving as a carbon source, for example, methane,
Examples thereof include ethane, propane, ethylene, and acetylene, all of which are effectively used for the purpose of the present invention. In this CVD process, it is sufficient to keep the heating temperature of the metal base material in the range of 300 to 400 ° C., and in this low temperature range, a uniform carbon coating is formed on the radiation-exposed surface of the nickel plating layer with good adhesion. .

[0013]

In order to efficiently form a carbon coating on the surface of a metal base material by the CVD method by thermally decomposing a hydrocarbon gas, it is necessary to keep the temperature of the metal base material at 800 ° C. or higher as a processing condition. It is a condition. In this case, if a transition metal such as nickel or cobalt intervenes on the substrate surface,
It is known that the carbon deposition temperature is lowered by the catalytic action, but in the present invention, the catalytic activity is further enhanced by irradiating the surface of the nickel plating layer previously formed on the surface of the metal substrate with a specific energy amount of radiation. It is an elevated one.

That is, the deposition of the carbon coating by CVD proceeds by the thermal decomposition of the hydrocarbon gas on the base material, but in order to facilitate this deposition and form a carbon coating with good adhesion, the hydrocarbon gas Must be efficiently adsorbed on the substrate surface. According to the present invention, a number of fine lattice defects are formed by irradiating the nickel-plated surface with radiation, and the lattice-defect surface plays a role of promoting adsorption of hydrocarbon gas to enhance the catalytic activity of the nickel-plated layer. It works to improve dramatically.

Through such a function, the metal base material is heated to 400 ° C.
It is possible to efficiently deposit a carbon coating that is homogeneous and has excellent adhesiveness even under the CVD conditions maintained at a certain level. Therefore, a thin carbon film can be formed without causing cracks or peeling phenomena on the surface of the metal substrate.

[0016]

EXAMPLES Examples of the present invention will be specifically described below in comparison with comparative examples.

Examples 1 to 3 A steel material [S45C manufactured by Shin Nippon Steel Co., Ltd.] was immersed in an aqueous hydrochloric acid solution in which palladium chloride was dissolved to carry out activation treatment, and then nickel sulfate and sodium hypophosphite. The electroless plating reaction was carried out by immersing in a plating bath (temperature 60 ° C., pH 5) having a composition of (reducing agent), sodium citrate (feeding agent) and sodium acetate (pH buffer). The metal substrate thus nickel-plated by the electroless plating method was irradiated with infrared rays at an energy amount such that the surface temperature of the nickel-plated surface increased to 200 ° C, 400 ° C and 600 ° C.

Then, the metal base material after the infrared irradiation is subjected to CVD.
It was set in a furnace, ethylene gas was introduced into the furnace while heating and holding the substrate at a temperature of 400 ° C., and the CVD operation was continued for 1 hour. It was confirmed that the carbon coatings deposited on the metal substrate surface by this operation were extremely homogeneous and had excellent adhesion. The film thickness and film properties of each of the obtained carbon films are shown in Table 1 in comparison with the applied varying conditions.

Example 4 A carbon film was formed on the surface of a metal substrate under the same conditions as in Example 1 except that the radiation was changed to visible light and the nickel plating surface was irradiated with an energy amount such that the surface temperature increased to 400 ° C. did. The obtained carbon coating was extremely homogeneous and had excellent adhesion. Table 1 also shows the film thickness and the film properties.

Example 5 A carbon coating was formed on the surface of a metal substrate under the same conditions as in Example 1, except that the radiation was changed to ultraviolet rays and the nickel plating surface was irradiated with an energy amount such that the surface temperature rose to 400 ° C. . The obtained carbon coating was a coating layer that was extremely homogeneous and had excellent adhesion. Table 1 also shows the film thickness and the film properties.

COMPARATIVE EXAMPLE 1 The same metal substrate surface as in Example 1 was irradiated with infrared rays with an amount of energy such that the surface temperature rose to 400 ° C. without nickel plating. Then, CVD is performed under the same conditions as in Example 1.
When the operation was carried out, no carbon film was deposited.

Comparative Example 2 A metal base material plated with nickel under the same conditions as in Example 1 was set in a CVD furnace without being irradiated with radiation, and a CVD operation was performed under the same conditions as in Example. No film deposition was observed.

Comparative Example 3 The infrared irradiation condition was that the surface temperature of the nickel-plated surface was 1
The amount of energy was set so low as to reach 50 ° C. Under all other conditions, the same conditions as in Example 1 were used to form a carbon coating on the metal substrate surface. In this example, the carbon coating formed as shown in Table 1 was extremely thin.

Comparative Example 4 The infrared irradiation condition was that the surface temperature of the nickel-plated surface was 6
The amount of energy was set to a high value such that the temperature increased to 50 ° C. In this example, it was confirmed that the carbon coating formed as shown in Table 1 was peeled off, and the metal base material was damaged and the material strength was lowered due to thermal deterioration.

[0025]

[Table 1]

[0026]

As described above, according to the method for forming a carbon film on a metal substrate according to the present invention, a simple pretreatment step for forming a nickel plating layer irradiated with radiation on the surface of the metal substrate and a low temperature CVD operation. It is possible to efficiently form a carbon coating film having good adhesion on the surface of the metal base material via. Therefore, it is extremely useful as an industrial carbon film forming means for various metal substrates.

Claims (2)

[Claims] 1. The surface temperature of the nickel-plated surface is 200 to 60 after nickel-plating the surface of the metal base material.
Forming a carbon coating film on a metal substrate, which comprises irradiating radiation in an energy range rising to 0 ° C., and then vapor-depositing a carbon coating layer on the irradiation surface through CVD by thermal decomposition of hydrocarbon gas Law. 2. The method for forming a carbon film on a metal substrate according to claim 1, wherein infrared rays, visible rays or ultraviolet rays are used as the radiation.