JP7162799B2 - Composite coating and method of forming composite coating - Google Patents

Description

TECHNICAL FIELD The present invention relates to a composite coating and a method for forming a composite coating, and more particularly to a composite coating comprising a hard carbon coating that exhibits excellent durability and adhesion and a method for forming the same.

Hard carbon (DLC: diamond-like carbon) film has excellent sliding properties such as low friction, high wear resistance, and low cohesion (seizure resistance). It is widely used as a sliding member for molds, cutting tools and automobile parts.

Various techniques have been developed to further improve these sliding properties of the hard carbon film. For example, in order to improve the adhesion to the substrate (base material) and reduce the coefficient of friction, as shown in FIG. A technique has been developed to form a two-layer structure of a lower layer 22 and an upper layer 23 of a hydrogen-containing hard carbon (aC:H) film (for example, Patent Document 1). A hydrogen-containing hard carbon film having a thickness of 2 to 10 times that of the hydrogen-free hard carbon film and a hydrogen content of 5 to 25 at% was formed on the hydrogen-free hard carbon film having a thickness of 0.5 to 200 nm. Coatings have been developed (eg, US Pat. Patent Document 2 describes that an intermediate layer 21 of W, Ti, Nb, or the like is formed on the surface of the substrate to improve the adhesion between the substrate and the hard carbon film.

In addition, in order to reduce the wear of the hard carbon film itself and the counterpart material, the Young's modulus is higher than 200 GPa, the sp ³ ratio is 50 to 90%, the hydrogen content is 20 at% or less, and the film thickness is thicker than 1 μm. aC:H layer containing Si and O with a Young's modulus lower than 200 GPa, an sp ³ ratio of 40% or less, a hydrogen content of 20-30 at%, on the body carbon (ta-C:H) layer is developed (for example, Patent Document 3).

Taking advantage of these excellent sliding properties of the hard carbon film, it is expected to be applied to coatings of members used under severer sliding conditions, such as bearings, gears, rollers, and the like.

JP-A-2000-128516 JP 2003-026414 A Japanese Patent No. 5503145

However, in the bearings, gears, rollers, etc. described above, large contact stress is repeatedly generated during sliding, so the hard carbon film formed using conventional technology cannot be said to have sufficient fracture resistance and peeling resistance. , it is known that adhesion is insufficient and sufficient durability cannot be obtained.

Therefore, the present invention is excellent in fracture resistance and peeling resistance, and can exhibit excellent adhesion even when used in applications where large contact stress is repeatedly generated during sliding, and has sufficient durability. An object of the present invention is to provide a coating and a method for forming the same.

Means for Solving the Problems As a result of intensive studies to solve the above problems, the inventors have found that the above problems can be solved by the invention described below, and have completed the present invention.

The invention according to claim 1,
A composite coating coated on a substrate, comprising:
A hard carbon film A having a hydrogen content of less than 5 at% and a film thickness of 200 to 1000 nm is formed as the lower layer,
A hard carbon film B having a hydrogen content of 5 to 30 at%, a film thickness of 210 to 5000 nm, and a Young's modulus of more than 200 GPa is formed on the upper layer,
The hard carbon film A and the hard carbon film B are directly laminated ,
The hard carbon film A is configured by laminating a plurality of hard carbon layers having different π/σ intensity ratios,
The π/σ intensity ratio of the hard carbon layer positioned as the uppermost layer is smaller than the π/σ intensity ratio of the entire hard carbon layer positioned below the hard carbon layer positioned as the uppermost layer . It is a composite coating.

When a hard carbon film is formed on bearings, gears, rollers, etc. by conventional techniques, the factors causing breakage and peeling are considered as follows.

That is, in bearings, gears, rollers, etc., a large surface pressure (load) is repeatedly applied to the coated hard carbon film during sliding, and a large contact stress is generated in the film each time. In addition, since the base material repeatedly deforms and restores in accordance with this, great fatigue occurs in the coating, and breakage or peeling occurs between the base material and the coating or between the coatings, resulting in a decrease in adhesion.

Specifically, in the case of Patent Document 2 described above, since the film thickness of the hydrogen-free hard carbon (aC) layer is as thin as 200 nm or less, the strength of the hydrogen-free hard carbon (aC) layer itself is insufficient. , easily deformed and destroyed by repeated contact stress. This breakage causes separation from the base material and the hydrogen-containing hard carbon (aC:H) layer, which is the upper layer, resulting in a decrease in adhesion.

In addition, in the case of Patent Document 3, the lower ta-C:H layer is hydrogenated, so that the adhesion to the upper layer is weak. This ta-C:H layer has a large ^sp3 ratio and high hardness, but the film thickness is thicker than 1 μm. Generally, the higher the hardness and the thicker the film thickness, the greater the residual stress of a hard carbon film. Therefore, a hard carbon film having a film thickness of more than 1 μm has a very large residual stress and is easily broken. Therefore, when an impact stress is applied, the lower layer is likely to be destroyed, the coating peels off from the substrate, and the adhesion decreases.

Since the hard carbon film having a hydrogen content of less than 5 at % in the present claim has a low hydrogen content, it has sufficient adhesion to the substrate and other hard carbon films, while having high hardness. For this reason, if the film is too thin, it cannot withstand repeated contact stresses and is likely to be deformed and broken. As a result of various experiments and studies, the present inventors have found that these problems can be solved by preferably setting the film thickness of the lower hard carbon film (hard carbon film A) to 200 to 1000 nm, and excellent adhesion can be obtained. found that it can be demonstrated.

Further, the present inventors directly applied a hard carbon film (hard carbon film B) having a hydrogen content of 5 to 30 at%, a film thickness of 210 to 5000 nm, and a Young's modulus of more than 200 GPa on the hard carbon film A. By laminating, the large load (stress) repeatedly applied during sliding can be sufficiently relieved, and by making a composite coating of these, sufficient fracture resistance and peeling resistance can be exhibited. It was found that excellent adhesion can be exhibited. The Young's modulus of the hard carbon film B is preferably 500 GPa or less from the viewpoint of preventing deterioration of chipping resistance.

When the hard carbon film A is formed as a single-layer thick film, the residual stress of the film tends to be high, and breakage and peeling are likely to occur. On the other hand, the hard carbon film A is a laminate of a plurality of thin films with different π/σ intensity ratios, and the π/σ intensity ratio of the hard carbon layer located at the top layer is When arranged so as to be smaller than the π/σ intensity ratio, the residual stress can be kept low, the occurrence of breakage and peeling can be suppressed, and excellent adhesion can be exhibited. The π/σ intensity ratio in the entire hard carbon layer means an average value after considering the film thickness of each layer when the lower layer is composed of a plurality of layers.

The π/σ intensity ratio is an index related to the ratio of sp ² bonds to ^{sp 3} bonds ⁽ sp ² /sp ³ ratio) in the hard carbon film. /σ intensity ratio becomes smaller, and when there are many sp ² bonds and few sp ³ bonds, the π/σ intensity ratio becomes large.

In the present claim, since the hard carbon film A is configured by laminating a plurality of hard carbon layers having different π/σ intensity ratios, a single-layer hard carbon film having the same π/σ intensity ratio throughout Unlike films, contact stress can be relaxed even between hard carbon layers of each layer to reduce residual stress. Then, when the π/σ intensity ratio of the uppermost hard carbon layer is set to be smaller than the π/σ intensity ratio of the entire lower hard carbon layer, the uppermost hard carbon layer is sp ³ Since there are many bonds and the hydrogen content is low, tetrahedral carbon with free bonds is sufficiently formed, and excellent adhesion to the hard carbon film B formed on the upper layer can be secured.

The invention according to claim 2 ,
2. The composite coating according to claim 1, wherein the hydrogen content of the hard carbon coating A is less than 1 at %.

The lower the hydrogen content of the hard carbon film A, the better the adhesion to the substrate and other hard carbon films. In the present invention, the hydrogen content is as low as less than 1 at %, so that the adhesion to other hard carbon films can be more sufficiently secured.

The invention according to claim 3 ,
A metal intermediate layer of Cr, W or Ti is provided between the base material and the hard carbon film A,
3. The composite coating according to claim 1 , wherein the metal intermediate layer has a thickness of 30 to 500 nm.

Cr, W and Ti have particularly high adhesion to the hard carbon layer compared to iron-based metals and alloys that are generally used for substrates. Therefore, when these metal intermediate layers are provided on the base material, peeling of the hard carbon film A from the base material is effectively suppressed. The thickness of the metal intermediate layer is preferably 30 to 500 nm, considering that if it is too thin, sufficient adhesion cannot be ensured, and if it is too thick, sufficient fracture resistance cannot be ensured.

The invention according to claim 4 ,
The hard carbon film B is
When the cross section is observed with a bright field TEM image, it has a relatively white white hard carbon layer and a relatively black black hard carbon layer,
4. The composite coating according to any one of claims 1 to 3 , wherein the white hard carbon layer and the black hard carbon layer are alternately laminated at the nano level.

Observation by bright-field TEM image shows that the relatively white white hard carbon layer has a low density, a large sp ² /sp ³ ratio, and a low hardness. On the other hand, a relatively black black hard carbon layer has a high density, a small sp ² /sp ³ ratio, and a high hardness. In the present claim, the white hard carbon layer and the black hard carbon layer having different hardnesses are alternately laminated at the nano level to constitute the hard carbon film B, so that greater stress relaxation can be obtained. It is possible to exhibit higher fracture resistance and peeling resistance, and to ensure excellent adhesion.

^In addition ^, the white hard carbon layer with a large sp ² /sp ³ ratio has insufficient wear resistance due to its low hardness as described above, but has excellent chipping resistance. Since the hard carbon layer has high hardness, it has excellent wear resistance. Therefore, the hard carbon film in which the white hard carbon layer and the black hard carbon layer are alternately laminated has both chipping resistance and wear resistance, and can exhibit excellent sliding properties.

The invention according to claim 5 ,
5. The composite coating according to claim 4 , wherein each of the white hard carbon layer and the black hard carbon layer has a thickness of 0.1 to 10 nm.

The above nano level is preferably 0.1 to 10 nm, and by laminating the white hard carbon layer and the black hard carbon layer with such a thickness, the above effects can be obtained.

Since the arc vapor deposition method is a film forming method using graphite as a film forming source, it is possible to easily form a hard carbon film A having a hydrogen content of less than 5 at %.

When this arc vapor deposition method is performed while introducing a hydrocarbon-based gas or hydrogen gas, carbon and hydrogen combine to easily form a hard carbon film B having a hydrogen content of 5 to 30 at %. can.

When the hard carbon film B is formed, by rotating the substrate on which the hard carbon film A is formed, it is possible to periodically provide a period of time during which the substrate is not irradiated with the carbon ions evaporated from the graphite. When the substrate is irradiated, it forms a black hard carbon layer (ta-C:H or aC:H) with high density and high hardness, while it is low density and low hardness when it is not irradiated. A white hard carbon layer (aC:H) can be formed, and a hard carbon film B in which a white hard carbon layer and a black hard carbon layer are alternately laminated is efficiently formed to achieve excellent adhesion. can ensure the integrity of the

According to the present invention, it is excellent in fracture resistance and peeling resistance, and can exhibit excellent adhesion and sufficient durability even when used in applications where large contact stress is repeatedly generated during sliding. It is possible to provide a coating having and a method of forming the same.

1 is a schematic cross-sectional view showing the configuration of a composite coating according to one embodiment of the present invention; FIG. FIG. 2 is a schematic cross-sectional view illustrating how a hard carbon film A is configured by laminating a plurality of hard carbon layers in a composite coating according to an embodiment of the present invention. FIG. 4 is a schematic cross-sectional view illustrating how a hard carbon film B is formed by laminating a plurality of hard carbon layers in the composite coating according to one embodiment of the present invention. 4 is a photograph of a cross section of an example of hard carbon film B. FIG. 4 is a photograph of a cross section of an example of hard carbon film B. FIG. 1 is a schematic diagram showing a main part of an arc-type PVD apparatus used for forming a composite coating in one embodiment of the present invention; FIG. It is a schematic diagram of the cross section of the conventional film. It is a schematic diagram which shows an example of a thrust test machine.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described based on embodiments with reference to the drawings. In addition, although the vacuum arc vapor deposition method is mentioned as an example as an arc vapor deposition method below, this invention is not limited to this.

[1] Structure of composite coating 1. Overview of Composite Coating First, the configuration of the composite coating will be described. FIG. 1 is a schematic cross-sectional view showing the configuration of the composite coating according to this embodiment. As shown in FIG. 1, the composite coating 1 according to the present embodiment comprises a substrate B, a metal intermediate layer 11, a lower hard carbon film (hard carbon film A) 12, an upper hard carbon film (hard carbon The film B) 13 is laminated in order.

2. Hard carbon film A
The lower hard carbon film (hard carbon film A) is a hard carbon film having a hydrogen content of less than 5 atomic %.

By setting the hydrogen content to less than 5 at %, it is possible to sufficiently ensure adhesion to the substrate and other hard carbon films. It should be noted that the lower the hydrogen content, the more the adhesiveness to the base material and other hard carbon films can be improved, so it is more preferable that the hydrogen content is less than 1 at %.

On the other hand, a hard carbon film with a hydrogen content of less than 5 at% has high hardness. Unbearable and easily destroyed. Therefore, in this embodiment, the thickness is set to 200 to 1000 nm.

A specific example of such a hard carbon film is a hydrogen-free tetrahedral carbon (ta-C) film.

In the present embodiment, the lower hard carbon film (hard carbon film A) is preferably formed by laminating a plurality of hard carbon layers having different π/σ intensity ratios.

FIG. 2 is a schematic cross-sectional view illustrating how a hard carbon film A is formed by laminating a plurality of hard carbon layers in the composite coating 1 . As shown in FIG. 2, the lower hard carbon film (hard carbon film A) is composed of a plurality of layers arranged under the top layer 12T.

At this time, it is preferable to make the π/σ intensity ratio of the top layer 12T smaller than the π/σ intensity ratio of the whole hard carbon layer located in the lower layer therebelow. Residual stress can be reduced in the top layer 12T by reducing the π/σ intensity ratio of the top layer 12T. As a result, excellent adhesion to the substrate can be secured. Here, the ``π/σ intensity ratio in the entire hard carbon layer located in the lower layer'' means that when the hard carbon layer located in the lower layer is composed of a plurality of layers, the thickness of each layer is taken into consideration. Means the calculated average value.

A small π/σ intensity ratio indicates that there are many sp ³ bonds and the hydrogen content is low, and as a result, tetrahedral carbon with free bonds is sufficiently formed on the surface of the hard carbon layer. Therefore, it is possible to ensure excellent adhesion with the upper hard carbon film (hard carbon film B) 13 .

3. Hard carbon film B
The upper hard carbon film (hard carbon film B) 13 is a hard carbon film having a hydrogen content of 5 to 30 at %, a film thickness of 210 to 5000 nm, and a Young's modulus of more than 200 GPa. As a result, a large load (stress) repeatedly applied during sliding can be sufficiently relieved. By directly laminating the carbon film A) 12 on the hard carbon film A) 12, sufficient fracture resistance and peeling resistance can be exhibited, and excellent adhesion can be ensured.

In the present embodiment, the upper hard carbon film (hard carbon film B) 13 is preferably formed by laminating a plurality of layers. Specifically, when a cross section of the upper hard carbon film (hard carbon film B) 13 is observed with a bright-field TEM image, a relatively white hard carbon layer and a relatively black black hard carbon layer are alternately formed. It is preferably laminated.

FIG. 3 is a schematic cross-sectional view illustrating how a hard carbon film B is formed by laminating a plurality of hard carbon layers in the composite coating 1 . In the case of FIG. 3, the upper hard carbon film (hard carbon film B) is formed by alternately laminating white hard carbon layers 13W and black hard carbon layers 13B.

The black hard carbon layer 13B has a high density and a small sp ² /sp ³ ratio, so it has high hardness. On the other hand, the white hard carbon layer 13W has a low density and a large sp ² /sp ³ ratio, so it has a low hardness. By alternately laminating the white hard carbon layers 13W and the black hard carbon layers 13B having different hardnesses in this way, it is possible to obtain greater stress relaxation, exhibiting higher fracture resistance and peeling resistance, Excellent adhesion can be secured.

Specific examples of the white hard carbon layer 13W include a hydrogenated amorphous carbon (aC:H) layer, and the black hard carbon layer 13B includes a hydrogenated tetrahedral carbon (taC:H) layer. and a hydrogenated amorphous carbon (aC:H) layer having a higher hardness than the white hard carbon layer 13W.

At this time, it is preferable that each of the white hard carbon layer 13W and the black hard carbon layer 13B is laminated at a nano level with a thickness of 0.1 to 10 nm.

4. Intermediate Layer The hard carbon film may be formed directly on the base material, but depending on the type of base material, sufficient adhesion may not be ensured. For example, in addition to ferrous base materials generally used as base materials, base materials such as non-ferrous metals or ceramics, hard composite materials, specifically carbon steel, alloy steel, hardened steel, high-speed tool steel, cast iron , aluminum alloys, Mg alloys, cemented carbides, etc., do not have sufficient adhesion to the hard carbon film.

Therefore, as shown in FIG. 1, it is preferable to appropriately provide the metal intermediate layer 11 on the base material B according to the type of the base material B. and the composite coating 1 can be sufficiently adhered. Further, the provided metal intermediate layer 11 is preferable because it also contributes to the improvement of wear resistance.

Examples of metal elements that can be used for such a metal intermediate layer include Cr, Ti, Si, W, and B. Among these, Cr, Ti, and W are preferred.

The thickness of the metal intermediate layer 11 is preferably 30-500 nm, more preferably 40-400 nm, and particularly preferably 50-300 nm.

5. Substrate In the present invention, the substrate on which the composite coating is formed is not particularly limited, and substrates such as iron-based, non-ferrous metals, ceramics, and hard composite materials can be used. Examples include chromium molybdenum steel (SCM), carbon steel, alloy steel, hardened steel, high-speed tool steel, cast iron, aluminum alloys, Mg alloys, and cemented carbide. Then, substrates whose properties do not significantly deteriorate at temperatures exceeding 200° C. are preferred.

[2] Method for Forming Composite Coating The composite coating according to the present embodiment described above can be manufactured according to the steps shown below.

1. Preparation of Substrate First, a substrate B on which a hard carbon film is to be formed is prepared and set in a film forming tank. At this time, a rare gas such as Ar gas or hydrogen gas is introduced into the film forming tank to generate plasma, and a bias voltage is applied to the substrate B, thereby forming a hard carbon film on the substrate B. It is preferable to remove stains and oxide layers on the surface (surface on which the hard carbon film is formed).

2. Formation of Metal Intermediate Layer Then, a metal intermediate layer 11 is formed, if necessary, on the hard carbon film formation surface from which dirt and oxide layers have been removed. This metal intermediate layer 11 is preferably formed by an arc evaporation method (arc ion plating method) using a metal raw material such as Cr, W or Ti as an arc evaporation source.

3. Formation of hard carbon film A Next, using an arc vapor deposition method using a graphite cathode as an arc vapor source, a hydrogen-free tetrahedral carbon ( ta-C) forming a film; At this time, the film thickness is controlled to 200 to 1000 nm and the hydrogen content of the formed hard carbon film is controlled to less than 5 at% by appropriately adjusting the temperature in the film forming tank, the arc current, etc. .

The hydrogen content can be measured by HFS (Hydrogen Forward Scattering) analysis.

As described above, in forming the lower hard carbon film (hard carbon film A) 12, it is preferable to laminate hard carbon layers having different π/σ intensity ratios. By appropriately adjusting the voltage (bias voltage) applied to the substrate, the π/σ intensity ratio can be controlled and hard carbon layers having different π/σ intensity ratios can be laminated.

In this embodiment, the π/σ intensity ratio of the top layer 12T is controlled to be smaller than the π/σ intensity ratio of all the lower layers, thereby increasing sp ³ bonds. As a result, a hard carbon film in which tetrahedral carbon with free bonds is sufficiently formed is formed on the top layer 12T, and sufficient adhesion to the hard carbon film (hard carbon film B) 13 formed on the upper layer is achieved. can be secured.

The π/σ intensity ratio is obtained by measuring 1s→π ^* intensity and 1sσ ^* intensity by EELS analysis (Electron Energy-Loss Spectroscopy), and comparing the measured π ^* intensity and σ ^* intensity. It is a value obtained as a ratio, and is known to be correlated with the ratio of sp ² and sp ³ bonds (sp ² /sp ³ ratio) in the hard carbon film.

Specifically, when the hard carbon film has ^few sp ² bonds and many sp ³ bonds ^, the π/σ intensity ratio decreases. Since the σ intensity ratio increases, the sp ² /sp ³ ratio can be grasped based on the value of the π/σ intensity ratio.

4. Formation of hard carbon film B Next, plasma is generated by introducing a hydrocarbon-based gas or hydrogen gas together with Ar gas into the film-forming cavities while using an arc evaporation method using a graphite cathode as an arc evaporation source. A hydrogenated amorphous carbon (aC:H) film is formed as an upper hard carbon film (hard carbon film B) 13 on the lower hard carbon film (hard carbon film A) 12 . In addition, the lower hard carbon film (hard carbon film A) 12 is formed using an arc vapor deposition method, and then a hydrocarbon-based gas or hydrogen gas is introduced to form the lower hard carbon film (hard carbon film A) 12. The upper hard carbon film (hard carbon film B) 13 may be formed by forming a hard carbon film having a higher hydrogen content than the above. In this case, both the upper layer and the lower layer of the formed hard carbon film are hydrogenated tetrahedral carbon (ta-C:H) films.

The hard carbon film B may be formed using a film forming apparatus different from the film forming apparatus used for forming the hard carbon film A. In this case, the surface of the previously formed hard carbon film is exposed to the atmosphere and dirt, and the adhesion of the hard carbon film B to the hard carbon film A may deteriorate. Film formation of B is preferred.

As in the case of the hard carbon film A, the film thickness of the hard carbon film B is controlled to 210 to 5000 nm by appropriately adjusting the temperature in the film forming tank, the arc current, and the like. At the same time, the hydrogen content of the formed hard carbon film is controlled to 5 to 30 atomic %. At the same time, the Young's modulus of the hard carbon film is controlled to be greater than 200 GPa.

The Young's modulus can be measured by a nanoindentation method conforming to ISO 14577, for example, using a dynamic hardness tester ENT1100a manufactured by Elionix (load: 300 g).

As described above, in forming the upper hard carbon film (hard carbon film B), it is preferable to laminate hard carbon layers having different densities.

When the hard carbon film B is formed, by rotating the substrate on which the hard carbon film A is formed, it is possible to periodically provide a period of time during which the substrate is not irradiated with the carbon ions evaporated from the graphite. When the substrate is irradiated, a high density and high hardness black hard carbon layer (ta-C:H or aC:H) is formed, while when it is not irradiated, the hydrocarbon-based gas is used as the raw material. It is possible to form a white hard carbon layer (aC:H) with a low density and low hardness. As a result, low-density aC:H and high-density taC:H can be alternately laminated.

That is, when the base material is irradiated with carbon ions evaporated from graphite, the collision energy is large, so that black hard carbon with a high density and high hardness and a small sp ² /sp ³ ratio tends to be formed. The carbon ions having a low collision energy are formed as a white hard carbon layer (aC:H) having a low density, a low hardness, and a large sp ² /sp ³ ratio. As a result, the hard carbon film formed while rotating and revolving the substrate has a structure in which white hard carbon and black hard carbon are laminated.

FIG. 6 is a schematic diagram of a main part of an arc-type PVD apparatus equipped with a rotating/revolving jig used for forming multiple layers as described above. As shown in FIG. 6, this arc PVD apparatus includes a vacuum chamber 42, a plasma generator (not shown), a heater 43, a rotation jig 44 as a substrate supporting device, a thermocouple 45 as a temperature measuring device, and a A bias power supply (not shown) and a pressure regulator (not shown) for adjusting the pressure in the furnace are provided. Note that T is a target (carbon target), and 41 is a base material on which an intermediate layer is formed.

A hard carbon film in which white hard carbon and black hard carbon are laminated can be obtained by holding the base material 41 on the rotating shaft of the rotation jig 44 and rotating it in the direction of the arrow.

In addition, such a laminated structure of the hard carbon film B is obtained by observing the hard carbon film B thinned by FIB (Focused Ion Beam) with a TEM (Transmission Electron Microscope) at an accelerating voltage of 200 kV, for example. It can be confirmed by observing a field-of-view TEM image. That is, when the cross section is observed with a bright-field TEM image, the lower the density of the hard carbon layer, the more the amount of electron beam transmission increases and the more white it appears. By observation, as shown in FIGS. 4 and 5, it can be confirmed that the hard carbon films are alternately laminated at the nano level. Note that the magnification is 200,000 times in FIG. 4, and the magnification is 500,000 times in FIG.

EXAMPLES Next, the present invention will be described more specifically based on examples.

1. Preparation of test piece A composite coating consisting of a hard carbon film A and a hard carbon film B was formed on a substrate (SCM415 carburized) to prepare a test piece. The composite coating has a two-layer structure in which a hydrogen-free hard carbon film (hard carbon film A) and a hydrogen-containing hard carbon film (hard carbon film B) having multiple layers with different π / σ strength ratios are laminated. 6 levels of 0 nm, 100 nm, 200 nm, 500 nm, 1000 nm, and 1500 nm for the film A, and 5 levels of 100 nm, 210 nm, 2500 nm, 5000 nm, and 7500 nm for the hard carbon film B. Test pieces on which 30 kinds of composite coatings were formed were prepared. Specifically, each test piece was prepared according to the following procedure.

(1) Formation of Hard Carbon Film A Using an SCM415 carburized disk (φ30 mm×t3 mm, HRC60, surface roughness Ra<0.01 μm) as a substrate, according to the method for producing a hard carbon film according to the present embodiment, Using an arc PVD apparatus, a hydrogen-free tetrahedral carbon (ta-C) film of each thickness was formed on the substrate under the film forming conditions of a bias voltage of 175 V and a film forming temperature of 180 ° C., and a hard carbon film A was formed. and The film formation temperature was controlled by a cooling process so that the maximum temperature reached 180°C. When the hydrogen content of the formed hard carbon film A was measured by HFS analysis, the hydrogen content was 0.1 at %. Prior to the formation of the hard carbon film A, dirt on the surface of the base material was removed, and a Cr metal intermediate layer (thickness: 200 nm) was provided using an arc ion plating method.

(2) Formation of hard carbon film B Next, using the same arc PVD apparatus, CH ₄ gas is introduced at the time of film formation to generate plasma, so that hydrogen-containing A hard carbon film (aC:H) was formed under film forming conditions of a bias voltage of 50 V and a film forming temperature of 130° C. to obtain a hard carbon film B.

2. Evaluation of Adhesion Adhesion in the film portion of the composite coating in each test piece was evaluated by a rolling test (thrust test) using a bearing.

(1) Test method A test was conducted using a thrust tester shown in FIG. Specifically, a steel ball 51 attached to a bearing ring 52 is pressed against each test piece 54 on which a composite coating is formed under a constant load in an oil 53, and the bearing ring 52 is rolled along the same raceway. It was carried out by revolving the steel ball 51 and repeatedly applying a load to the revolving orbit portion of the steel ball 51 a predetermined number of times. Details of the test conditions are shown in Table 1.

The film portion after repeated load application was observed, and the state thereof was evaluated using the film adhesion evaluation index shown in Table 2 on a 5-point scale. In the film adhesion evaluation index, 1 indicates low peeling resistance, and 5 indicates high peeling resistance.

(2) Results The results are shown in Table 3 in which the film thickness of the hard carbon film A and the film thickness of the hard carbon film B are arranged in a matrix.

From Table 3, when the thickness of the hard carbon film A is 200 to 1000 nm and the thickness of the hard carbon film B is 210 to 5000 nm (areas surrounded by thick lines), excellent peeling resistance is obtained. It was confirmed that especially excellent peeling resistance was obtained when the thickness of the film A was 500 nm and the thickness of the hard carbon film B was 2500 nm. In the case of the hard carbon film A having a film thickness of 1500 nm, peeling had already occurred before the test was conducted, so the table simply indicates "peeling".

Although the present invention has been described above based on the embodiments, the present invention is not limited to the above embodiments. Various modifications can be made to the above embodiment within the same and equivalent scope of the present invention.

REFERENCE SIGNS LIST 1 composite coating 2 coating 11 metal intermediate layer 12 hard carbon coating A
12T Top layer 13 Hard carbon film B
13B black hard carbon layer 13W white hard carbon layer 21 intermediate layer 22 lower layer 23 upper layer 41, B substrate 42 vacuum chamber 43 heater 44 rotation/revolution jig (substrate support device)
45 thermocouple 51 steel ball 52 bearing ring 53 oil 54 test piece T target

Claims (5)

A composite coating coated on a substrate, comprising:
A hard carbon film A having a hydrogen content of less than 5 at% and a film thickness of 200 to 1000 nm is formed as the lower layer,
A hard carbon film B having a hydrogen content of 5 to 30 at%, a film thickness of 210 to 5000 nm, and a Young's modulus of more than 200 GPa is formed on the upper layer,
The hard carbon film A and the hard carbon film B are directly laminated ,
The hard carbon film A is configured by laminating a plurality of hard carbon layers having different π/σ intensity ratios,
The π/σ intensity ratio of the hard carbon layer positioned as the uppermost layer is smaller than the π/σ intensity ratio of the entire hard carbon layer positioned below the hard carbon layer positioned as the uppermost layer . Composite coating. 2. The composite coating according to claim 1, wherein the hydrogen content of said hard carbon coating A is less than 1 at %. A metal intermediate layer of Cr, W or Ti is provided between the base material and the hard carbon film A,
3. The composite coating according to claim 1 , wherein the metal intermediate layer has a thickness of 30 to 500 nm. The hard carbon film B is
When the cross section is observed with a bright field TEM image, it has a relatively white white hard carbon layer and a relatively black black hard carbon layer,
4. The composite coating according to any one of claims 1 to 3 , wherein the white hard carbon layer and the black hard carbon layer are alternately laminated at the nano level. 5. The composite coating according to claim 4 , wherein each of the white hard carbon layer and the black hard carbon layer has a thickness of 0.1 to 10 nm.

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