JP2689146B2 - Hard carbon film coating method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method of coating a hard carbon film on a metal base material, which enables the wear resistance of an object,
It provides lubricity and corrosion resistance.

[Prior Art] Since a hard carbon film has hardness comparable to that of diamond and is excellent in wear resistance, lubricity, and corrosion resistance, it is expected to be used in various applications. In the case of direct coating, the original excellent characteristics of the film have not always been utilized due to the problem of its adhesive force. That is, for example, as shown in the second diamond symposium proceedings, page 93 (1987), the hard carbon film is made of a metal material such as silicon or tungsten that has a high covalent bond with carbon. Is capable of directly coating a hard carbon film to form a highly adherent coating, but does not form a covalent bond with the carbon, III A, I
VA, VA, VI A, VII A, VIII A, metal belonging to Group VIII A, or when using a metal material of these alloys as the base material, in the conventional method of directly coating the hard carbon film,
It has been difficult to coat a hard carbon film having excellent hardness, wear resistance, lubricity, and corrosion resistance, and having a large adhesion to the substrate.

[Problems to be Solved by the Invention] An object of the present invention is to newly develop a method for coating a hard carbon film having good adhesion on a metal substrate.

[Means and Actions for Solving the Problems] The gist of the present invention is as follows.

(1) A coating method for a hard carbon film, which comprises carburizing a metal base material, then subjecting the surface of the base material to hydrogen plasma treatment, and then coating the hard carbon film.

(2) The method for coating a hard carbon film according to the above item 1, wherein the carburizing method on the metal substrate is an ion carburizing method.

The hard carbon film referred to in the present invention is as follows.
The element is mainly composed of carbon, has a hardness similar to that of natural diamond, is amorphous, and has a halo pattern in an electron diffraction image. Raman spectrum around 1580 cm ^-1 and 1360 cm
A broad peak peculiar to amorphous is shown near ^-1 . When a thin film of hard carbon is observed under a scanning electron microscope at a magnification of about 10,000 times, it is a uniform and smooth film with no grain boundaries.
Hard carbon is generally produced by a vapor phase synthesis method using a hydrocarbon compound as a raw material, and contains about 40 atom% or less of hydrogen. It is believed that hydrogen enters the dangling bond portion of carbon atoms, stabilizes the amorphous state, and has a high hardness structure.

It is speculated that the presence of an appropriate amount of hydrogen causes hard carbon to exhibit a high altitude similar to that of natural diamond. Too much hydrogen in the hard carbon film results in a soft organic film. Therefore, as the hard carbon film of the present invention, a hydrogen content of 35 atom% or less, preferably 5 to 30 atom% is suitable.

As a method for forming a hard carbon film used in the present invention, the adhesion of the coating to the substrate, the uniformity of the film quality, the smoothness of the film surface, the productivity, JP-A-59-174507, Sho 59
Ionization vapor deposition methods such as those disclosed in JP-A-174508 are preferable.

FIG. 1 shows the principle of the ionization vapor deposition apparatus. Carbon-hydrogen gas, which is a raw material for the hard carbon film, is introduced under reduced pressure, and is ionized by the filament 3 that is glow-discharged and red-heated, and the ions are extracted by the spreading magnetic field of the electromagnet 4.
This part covered with an electromagnet is called an ion source. The extracted ions are accelerated toward the substrate 1 to which a negative bias voltage is applied, collide with the substrate and deposit. As the raw material gas, hydrocarbons such as methane, ethane, acetylene, and benzene which can be easily introduced as a gas may be used, and among them, methane is preferable. Hydrogen gas may be used as a diluent gas for the above-mentioned raw material gas. The pressure in the container is 1 × 10 ^-6 Torr to 1 Torr because it is necessary to generate plasma and accelerate ions, but from the viewpoint of film quality and film formation rate, it is 1 × 10 ^-4 Torr. 1 x 10 ^-1 To
rr is desirable. When the substrate temperature is from room temperature (about 25 ° C) to 600 ° C, a good thin film is formed. Even within this range, room temperature (about 25 ° C) to 300 ° C is particularly preferable. When the base material temperature is higher than 600 ℃, the formed film tends to become graphitic, and even if a hard carbon film is formed, if it is left to cool to room temperature, the residual heat between the base material and the film will remain. Due to the high stress, the film is likely to peel off during subsequent use. The bias voltage between the base material and the ion source is -50V to -1500V, with -500V to -1000V being the preferred range. When the hydrocarbon ions are accelerated by the bias voltage and collide with the substrate, the collision energy breaks the C—H bond of the colliding ions and the hydrogen atoms are ejected. The amount by which the hydrogen atoms are ejected depends on the kinetic energy of the colliding ions, that is, the bias voltage,
If the bias voltage is too low, an organic soft film containing a large amount of hydrogen tends to be formed, and if the bias voltage is too high, a graphite film is formed, and further, self-sputtering of the film occurs and the film formation rate decreases. The magnetic flux density at the ion source is 100G to 10
A range of 00G is suitable, and 300G to 500G is a more preferable range. Detailed manufacturing conditions vary depending on the arrangement of gas inlets in the apparatus, the size of the ion source, the position of the base material, etc. Therefore, it is desirable to set the optimum conditions appropriately.

Metal substrates targeted by the present invention, III A, IV A, VA,
Any metal that belongs to group VI A, VII A, VIII A, or alloys thereof that is hard to form a covalent bond with carbon and can be carburized, that is, Zr, Ta, Mo, Fe, Co, Ti, etc. Although it can be used, iron and cobalt are important from a practical point of view.

In carrying out the present invention, carburizing treatment in the following order,
The hydrogen plasma treatment and the hard carbon film coating operation may be performed. First, the target metal base material is subjected to carburizing treatment. At this time, it is better to carburize the metal base material surface layer with as much carbon as possible, and a thin carbon layer is formed on the metal base material surface. Such a state may occur, but there is no problem even if the process shifts to the next hydrogen plasma treatment in such a state.

As the carburizing method used in the present invention, conventionally used methods such as a gas carburizing method and a molten salt carburizing method can be used. In addition to this, by placing the base material in a container where the hydrocarbon gas such as methane or ethane is decomposed and ionized while keeping the base material at a high temperature, the base material is carburized and the base material surface is also Ion carburizing methods can be used to form a thin film of carbon. From the viewpoint of film adhesion at the time of forming a carbon hard film in a later step, the ion carburizing method is capable of carburizing a large amount of a base material and forming a base material surface carbon thin film, and carburized carbon,
The application of the ion carburizing method is desirable in order to coat a hard carbon film, which has a strong adhesion to the carbon of the surface film and has a strong adhesive force.

Next, a hydrogen plasma treatment is applied to the metal base material which has been subjected to the carburizing treatment as described above. The hydrogen plasma treatment performed in the present invention is
Plasma C as described in JP-B-62-120
A method of leaving a substrate in a hydrogen plasma generated by a plasma PVD device disclosed in Japanese Patent Laid-Open No. 59-174507 and an ion beam as disclosed in Japanese Patent Laid-Open No. 61-122197. And a method of irradiating hydrogen plasma species with an apparatus or an ion implantation apparatus.
In essence, any method can be used as long as hydrogen atoms and hydrogen ions generated by decomposition of hydrogen molecules can be made to collide with the base material at high speed by heat or an electromagnetic field.

After that, the above-described hard carbon film forming process is performed. In a series of these carburizing, hydrogen plasma treatment, and hard carbon film formation processes, if exposed to an air atmosphere during the process, a gas such as oxygen will be adsorbed on the surface, and the adhesion of the hard carbon film will decrease. It is desirable to carry out continuous treatment with.

In the method of the present invention, the mechanism by which a hard carbon film having strong adhesion can be coated is not necessarily clear, but it is considered as follows. That is, by first carburizing the base material and forming a carbon-rich layer on the base material surface layer, between the carbon carburized on the base material and the carbon of the hard carbon film coated on the surface. It is thought that a strong bond can be made. If the base material is not carburized, it is considered that only a bond between the metal base material and carbon exists at the interface between the base material and the hard carbon film, and in general, a strong bond is formed between the metal material and carbon. Since it is not made, a film with excellent adhesiveness cannot be obtained by this method. Further, in the present invention, it is considered that the adhesion between the hard carbon film and the carbon layer is improved by activating the surface layer by performing hydrogen plasma treatment in advance.

[Example] Example 1 Pure iron (99.99%) with a thickness of 5 mm whose surface was mirror-finished
The plate was subjected to gas carburization with methane gas under the conditions that the surface equilibrium carbon concentration of the sample surface gas was 0.9%, the carburization temperature was 930 ° C., and the carburization time was 1 hour. As a result, it was confirmed by analyzing the cross section of the sample with an electron probe micro-analyzer that the carburization has progressed into pure iron over a depth of about 1 mm from the surface.

Next, hydrogen gas was used as a raw material on the surface of this sample at atmospheric pressure of 1 × 10
Hydrogen plasma irradiation was carried out for 30 minutes under the conditions of ^-2 Torr, substrate bias voltage -1000 V, substrate temperature 300 ° C, and ion current ² mA / cm ² . Then, by ionization deposition method, methane gas is used as a raw material and the atmospheric pressure is 1 × 10 ^-2 Torr and the substrate bias voltage is -800.
As a result of vapor deposition for 60 minutes under conditions of V, substrate temperature of 300 ° C. and ion current of ² mA / cm ² , the surface is as smooth as the substrate surface and a hard carbon film with a thickness of about 1 μm without peeling can be uniformly coated. It was The hydrogen content of this film was 26 atom%, and the electron diffraction pattern showed a halo pattern. It showed a broad peak around 1580 cm ^-1 and around 1360 cm ^-1 in the Raman spectrum. Even if the coated sample surface was scratched with a 9H pencil, neither peeling of the film nor scratches occurred. Similarly, scratching with stainless steel tweezers created a groove. This is because the iron of the base material was plastically deformed and dented into a groove shape, and even in this case, peeling of the hard carbon film was not observed.

Example 2 On a mirror-finished surface of a pure iron (99.99%) plate having a thickness of 5 mm, methane gas was used as a raw material and an atmospheric pressure was 1 × 10 ^-2 by an ion carburizing method.
Carburization was performed by performing vapor deposition for 10 minutes under the conditions of Torr, substrate bias voltage of −1000 V, substrate temperature of 760 ° C., and ion current of ² mA / cm ² . As a result, simultaneously with carburization, a graphite film having a thickness of about 0.08 μm was deposited on the surface of the base material. Since the base material temperature is high,
It was confirmed by the electron probe microanalyzer that the cross section of the sample was analyzed for carburizing into pure iron over a depth of 0.5 mm.

Next, pressure of 1 x 10 ^-2 was applied to this sample surface using hydrogen gas as a raw material.
Hydrogen plasma irradiation was performed for 60 minutes under the conditions of Torr, substrate bias voltage of −1000 V, substrate temperature of 300 ° C., and ion current of ² mA / cm ² . As a result, it was found by Raman scattering spectroscopy that the surface carbon had been modified to hard carbon, and by the ¹⁵ N resonance nuclear reaction method, the hydrogen content of 8 to 8
It was confirmed that 2 atom% existed.

Then, by ionization deposition method, atmospheric pressure of 1 × 10 ^-2 Torr using methane gas as a raw material, substrate bias voltage of -800 V,
A hard carbon film was coated for 60 minutes under the conditions of a substrate temperature of 300 ° C. and an ion current of ² mA / cm ² . The hydrogen content of this membrane is 27
atom%, and the electron diffraction pattern showed a halo pattern. It showed a broad peak around 1580 cm ^-1 and around 1360 cm ^-1 in the Raman spectrum.

This sample had a surface that was as smooth and evenly coated as the substrate surface. Even if the surface was scratched with a pencil of 9H, neither peeling of the film nor scratches occurred. Similarly, scratching with stainless steel tweezers created a groove. This is because the iron of the base material was plastically deformed and dented in the shape of a groove, and in this case as well, peeling of the hard carbon film was not observed.

Example 3 On a mirror-finished surface of a 6 mm thick cobalt (99.99%) plate,
Ion carburization method, using methane gas as a raw material, atmospheric pressure 1 ×
10 ^-2 Torr, substrate bias voltage -1000V, substrate temperature 800 ℃,
It was vapor-deposited for 10 minutes under the condition of an ion current of 3 mA / cm ² and carburized. As a result, a graphite film having a thickness of about 0.09 μm was deposited on the surface of the base material simultaneously with carburization. It was confirmed by analyzing the sample cross section with an electron probe microanalyzer that the carburization progressed into cobalt over a depth of about 0.6 mm from the interface due to the high substrate temperature.

Next, pressure of 1 x 10 ^-3 was applied to this sample surface using hydrogen gas as a raw material.
Hydrogen plasma irradiation was performed for 60 minutes under the conditions of Torr, substrate bias voltage of −1000 V, substrate temperature of 300 ° C., and ion current of 3 mA / cm ² . As a result, it was found by Raman scattering spectroscopy that the surface carbon was modified to hard carbon. Furthermore, by the ¹⁵ N resonance nuclear reaction method, hydrogen of 7 ~
It was confirmed that 2 atom% existed.

Then, by ionization deposition method, atmospheric pressure of 1 × 10 ^-2 Torr using methane gas as a raw material, substrate bias voltage of -800 V,
A hard carbon film was coated for 60 minutes under the conditions of a substrate temperature of 300 ° C. and an ion current of 3 mA / cm ² . The hydrogen content of this membrane is 26
atom%, and the electron diffraction pattern showed a halo pattern. It showed a broad peak around 1580 cm ^-1 and around 1360 cm ^-1 in the Raman spectrum.

This sample had a surface that was as smooth and evenly coated as the substrate surface. Even if the surface was scratched with a pencil of 9H, neither peeling of the film nor scratches occurred. Similarly, scratching with stainless steel tweezers created a groove. This is because the cobalt of the substrate was plastically deformed and dented in the shape of a groove, and in this case as well, peeling of the hard carbon film was not observed.

Example 4 On a mirror-finished surface of an iron-12% cobalt-15% molybdenum alloy plate having a thickness of 10 mm, methane gas was used as a raw material and an atmospheric pressure was 1 × 10 ^-2 Torr and a substrate bias voltage was -1000.
Carburization was performed by vapor deposition for 10 minutes under the conditions of V, substrate temperature 700 ° C., and ion current ² mA / cm ² . As a result, about 0.08
A μm thick graphite film was deposited on the surface of the substrate. It was confirmed by analyzing the cross section of the sample with an electron probe microanalyzer that the carburization progressed into the alloy at a depth of about 0.6 mm from the interface due to the high substrate temperature.

Next, pressure of 1 x 10 ^-3 was applied to this sample surface using hydrogen gas as a raw material.
Hydrogen plasma irradiation was performed for 60 minutes under the conditions of Torr, substrate bias voltage of −1000 V, substrate temperature of 300 ° C., and ion current of 3 mA / cm ² . As a result, it was found by Raman scattering spectroscopy that the surface carbon had been modified to hard carbon, and by the ¹⁵ N resonance nuclear reaction method, the hydrogen content of 8 to 8
It was confirmed that 2 atom% existed.

Then, by ionization deposition method, atmospheric pressure of methane gas as a raw material was 1 × 10 ^-2 Torr, substrate bias voltage was -800V,
A hard carbon film was coated for 60 minutes under the conditions of a substrate temperature of 300 ° C. and an ion current of 3 mA / cm ² . The hydrogen content of this membrane is 26
atom%, and the electron diffraction pattern showed a halo pattern. It showed a broad peak around 1580 cm ^-1 and around 1360 cm ^-1 in the Raman spectrum.

This sample had a surface that was as smooth and evenly coated as the substrate surface. No film, peeling, or scratches were formed even when the surface was scratched with a 9H pencil. Similarly, when scratched with zirconia ceramic tweezers, a groove was formed. This is because the alloy of the base material was plastically deformed and dented in the shape of a groove, and in this case as well, peeling of the hard carbon film was not observed.

In addition, in Examples 1, 2, 3 and 4, when neither carburizing nor hydrogen plasma treatment was performed, all films were peeled off.

[Effects of the Invention] According to the present invention, various materials such as iron, cobalt or alloys thereof, which have been difficult to directly coat a hard carbon film excellent in lubricity, wear resistance and corrosion resistance, have been used. It has become possible to coat the metal materials of the above with a strong adhesive force, and has opened up applications as a lubricious coating and an abrasion resistant coating.

[Brief description of the drawings]

FIG. 1 is a principle diagram of an ionization vapor deposition apparatus. 1 is the base material,
2 is a grid, 3 is a filament, 4 is an electromagnet, and 5 is a source gas introduction tube.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C23C 16/02 C23C 16/02 (72) Inventor Maki Sato 1618 Ida, Nakahara-ku, Kawasaki-shi, Kanagawa Shin (72) Inventor Kenichi Fujimoto, 1618 Ida, Nakahara-ku, Kawasaki-shi, Kanagawa Nippon Steel Co., Ltd.

Claims (2)

(57) [Claims] 1. A method for coating a hard carbon film, which comprises subjecting a metal substrate to a carburizing treatment, subjecting the surface of the substrate to a hydrogen plasma treatment, and then coating a hard carbon film. 2. The method for coating a hard carbon film according to claim 1, wherein the method of carburizing the metal substrate is an ion carburizing method.