JP2006008853A - Hard carbon film sliding member and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hard carbon film sliding member that can readily smoothen its sliding surfaces and shows a low friction coefficient and provide a method for producing such a hard carbon film sliding member. <P>SOLUTION: By varying the hydrogen partial pressure in the film-forming atmosphere during formation of the hard carbon film by the vapor phase process, the hard carbon film is made a multi-layered structure composed at least of a soft-layer 1 on the outermost surface and a hard layer 2 under the soft layer 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hard carbon film sliding member having excellent low friction characteristics, and particularly to a hard carbon film sliding member suitable for use in a lubricating oil such as engine oil and transmission oil, and such a sliding material. The present invention relates to a method for manufacturing a moving member.

The hard carbon film is a film made of amorphous carbon or amorphous hydrogenated carbon, and includes aC: H (amorphous carbon or hydrogenated amorphous carbon), iC (eye carbon), DLC (diamond-like). (Carbon or DLC).
In order to form such a hard carbon film, a plasma CVD method in which a hydrocarbon gas is plasma-decomposed, an ion beam evaporation method using carbon or hydrocarbon ions, an arc ion plating method, a magnetron sputtering method, or the like. A known thin film synthesis method such as the method is used.

This hard carbon film has a high hardness, a smooth surface, excellent wear resistance, a low coefficient of friction due to its solid lubricity, and excellent sliding characteristics.
For example, the friction coefficient of non-lubricated surface of a normal smooth steel material is 0.5 to 1.0, whereas in the hard carbon film, the friction coefficient of non-lubricated is about 0.1. .

  The hard carbon film makes use of the above-mentioned excellent characteristics and is a non-lubricating tool such as a cutting tool such as a drill blade or grinding tool, a metal mold for plastic processing, a valve cock or a capstan roller. It is applied to sliding parts below.

On the other hand, in mechanical parts such as internal combustion engines that slide in lubricating oil, there is a demand to reduce mechanical loss as much as possible from the viewpoint of energy consumption and environmental problems. Application of a hard carbon film is being studied. In that case, it is necessary to determine the specifications of the film and select the lubricating oil in consideration of the surface roughness, sliding speed, surface pressure, lubricating oil and interaction with additives contained in the lubricating oil. (For example, refer to Patent Document 1).
JP 2000-297373 A

  In general, the surface roughness of a sliding member greatly affects the friction characteristics and wear characteristics. Hard carbon film is no exception, and not only in non-lubricated conditions, but also when used in lubricating oil, the conditions of high surface pressure, low relative sliding speed, or low oil viscosity In so-called boundary lubrication conditions, the friction coefficient is strongly influenced by the surface roughness. Of course, the smoother the surface, the better for reducing the coefficient of friction.

  The present invention has been made paying attention to the above-mentioned problems related to the surface shape of the hard carbon film, and the object is to obtain a smooth surface more easily than the conventional hard carbon film. Then, as a result, it is providing the hard carbon film sliding member which shows a low friction coefficient, and the manufacturing method of such a hard carbon film sliding member.

  In order to achieve the above object, the present inventors have conducted extensive studies on the types and components of the hard carbon film, the film forming method, and the like. As a result, the hard carbon film has a multilayer structure of at least two hard and soft layers, and the surface side is The present inventors have found that the above object can be achieved by using a soft layer, and have completed the present invention.

  That is, the hard carbon film sliding member of the present invention has a laminated structure composed of two or more layers of hard carbon film, and the hardness of the lower layer is higher than the hardness of the outermost layer. In the method for producing a hard carbon film sliding member of the present invention, when forming the laminated structure of the hard carbon film sliding member, hydrogen in the atmosphere is formed during the formation of the hard carbon film by a vapor phase method. The partial pressure is changed, and the outermost surface layer is polished as necessary after the formation of the laminated structure.

According to the present invention, the outermost layer in the hard carbon film having a laminated structure of two or more layers is a relatively soft layer, and the innermost layer has a hard layer having a hardness higher than the outermost layer. The protrusions of the surface wear relatively quickly, and the smoothness of the surface of the sliding member can be improved by polishing immediately after the start of sliding or in advance, and the friction coefficient can be reduced. The hard carbon film sliding member according to the present invention can be used even without lubrication, but the effect is remarkably exhibited especially when used in lubricating oil.
Further, in forming the laminated structure as described above, since the hydrogen partial pressure in the atmosphere is changed during the formation of the hard carbon film by the vapor phase method, the hydrogen atom concentration of each layer of the hard carbon film and The hardness can be controlled to a desired state, and a hard carbon film sliding member having the above hardness distribution can be easily manufactured.

Hereinafter, the present invention will be described in more detail.
As shown in FIG. 1 (a), the hard carbon film in the hard carbon film sliding member of the present invention has at least a layer 2 (hereinafter referred to as "hard layer") having high hardness and not easily worn on the base material 3. And a layer 1 having a relatively low hardness (hereinafter referred to as “soft layer”) on the surface side.
When the sliding member covered with the film having such a laminated structure slides with respect to the counterpart member, the convex part of the film is worn relatively quickly as compared with the case where the whole is constituted by the hard layer. On the other hand, the soft layer remains embedded in the recess. As a result, as shown in FIG. 1B, the smoothness during use is improved early as compared with the case where the entirety is formed of a hard layer. At this time, if necessary, it is possible to improve the smoothness from the initial state of use by adding a polishing step after film formation.

Generally, when two members are slid in a lubricant, the coefficient of friction is closely related to the surface roughness of each member. When the thickness of the lubricant film is h, the surface roughness (root mean square roughness) of one member is Rq1, and the other surface roughness (root mean square roughness) is Rq2, the following formula (1) In order to reduce friction, it is desirable to increase the value of the oil film parameter Λ as much as possible and bring the sliding condition closer to the fluid lubrication condition. Specifically, it is said that fluid lubrication occurs when Λ is approximately 3 or more, and mixed lubrication occurs within a range of 1 to 3. When the ratio is less than 1, boundary lubrication is significantly affected by solid contact, and the effect of the lubricant is hardly exhibited, and the friction coefficient is increased.
Λ = h ÷ (Rq1 ² + Rq2 ² ) ^1/2 (1)

Here, h is determined by the surface pressure, the macroscopic shape near the sliding portion, and the property of the lubricant. Accordingly, it goes without saying that in order to increase Λ, at least one of Rq1 and Rq2 should be reduced on the member side.
As described above, one of the solutions is the early smoothing by providing a relatively soft layer on the hard layer, but the effect of the present invention is not limited to the improvement of the surface roughness.

  That is, in the hard carbon film sliding member of the present invention, the hard layer exposed at the convex portion of the base material due to the abrasion of the outermost layer (soft layer) plays an important role as described below, and thereby friction The coefficient can be further reduced, and the friction can be further reduced in combination with the above-described improvement in surface smoothness.

There are several methods for adjusting the hardness of the hard carbon film, but in the hard carbon film sliding member of the present invention, a method of reducing the proportion of hydrogen atoms in the layer is preferable in forming the hard layer. In this case, the proportion of hydrogen atoms is 1 atomic% or less, preferably 0.3% or less. Here, if the content of hydrogen atoms exceeds 1 atomic%, the desired hardness may not be obtained. Moreover, even if hydrogen exceeds 1 atomic%, it may become a desired hardness, but it turned out that the friction reduction effect described below becomes difficult to obtain.
As a result of previous studies, the present inventors have found that when the hard carbon film slides in the lubricant, the friction coefficient decreases as the amount of hydrogen in the film decreases. The mechanism is not completely elucidated yet, but the less hydrogen in the layer, the stronger the interaction with the base oil and additives in the lubricant, and the more base oil molecules and additive molecules are on the surface. It is considered that the direct contact with the counterpart material is prevented by adsorption, that is, an effect equivalent to increasing the value of h in the formula (1) is obtained. For this purpose, the proportion of hydrogen atoms is preferably 1 atom% or less, preferably 0.3% or less.

  The method for forming the soft layer covering the hard layer is not particularly limited, but there is a simple method in which hydrogen is contained in the film. The hard carbon film containing hydrogen is known as hydrogenated amorphous carbon, and can be formed by a known method such as chemical vapor synthesis (CVD method) using a hydrocarbon gas as a raw material. In addition, even in a method of forming a film using only carbon as a raw material, such as an arc ion plating method or a magnetron sputtering method, by introducing hydrogen gas or hydrocarbon gas into a part of the atmosphere during film formation, Hydrogen can also be contained in the film.

The thickness of the soft layer is determined in consideration of the surface roughness of the hard layer. The surface roughness of the hard layer is represented by an Rq value (root mean square roughness) defined in Japanese Industrial Standard, and a soft layer having a thickness of about 0.7 to 2 times is preferably provided. That is, if it is too thin, the effect of flattening the surface is small, and if it is too thick, it takes time until the underlying hard layer appears on the surface and friction starts to decrease.
In order to measure the surface roughness of the hard layer, a sample in which film formation has been completed up to the hard layer is made by a preliminary experiment, and it is measured with an appropriate surface roughness meter. It is easy to calculate the thickness of the soft layer on which the surface is to be coated.

  In the hard carbon film sliding member of the present invention, the surface soft layer formed on the hard layer may have a structure of two or more layers. In that case, what is necessary is just to design so that the hardness of any surface soft layer may become smaller than the hardness of the said hard layer. Further, an appropriate known intermediate layer may be provided between the hard layer and the base for the purpose of stress relaxation and adhesion improvement. In this case, the intermediate layer includes a hard carbon film containing hydrogen (hydrogenated amorphous carbon) as an option.

The method for producing the hard carbon film sliding member of the present invention is not particularly limited as long as a soft layer is formed on the surface side and a hard layer is formed on the base side. Therefore, a hard carbon film can be formed, which is advantageous in terms of cost.
That is, a desired hard layer is first formed using a film forming method that does not involve hydrogen in the manufacturing process, such as arc ion plating and magnetron sputtering, and then a film forming atmosphere is subsequently formed. Hydrogen or a hydrocarbon is introduced into the substrate to form a soft layer containing hydrogen.

The film formation rates of the hard layer that does not substantially contain hydrogen and the soft layer that contains hydrogen are determined through separate preliminary experiments. Depending on the film formation rate, film formation is performed in an atmosphere that does not contain hydrogen or hydrocarbons for a certain period of time from the start of film formation, and then hydrogen or hydrocarbons are added to the atmosphere for a time corresponding to the desired soft layer thickness. May be formed to form a soft layer.
The amount of hydrogen in the soft layer is obtained by conducting a preliminary experiment to determine the relationship between the “amount of hydrocarbon or hydrogen introduced” and the “amount of hydrogen in the film”, and an appropriate amount of hydrogen or hydrocarbon in the atmosphere. It can be introduced and controlled.

Even during the formation of the soft layer, it is not necessary to make the introduction amount of hydrogen or hydrocarbon constant, and for example, it may be changed continuously. That is, even in the soft layer, it is possible to have a gradient distribution in which the amount of hydrogen near the base is low and the amount of hydrogen near the surface is large.
Further, the hydrogen concentration in the film after film formation and the distribution in the depth direction can be obtained using a method such as secondary ion mass spectrometry.

  Examples of the present invention will be described below together with comparative examples. Needless to say, the embodiment described below is not necessarily required as long as it satisfies the claims of the present invention.

Example 1
In this example, a film is formed by an arc ion plating method, and a hard layer and a soft layer are separately formed by changing the composition of the atmospheric gas.
First, a disk made of carburized steel (JIS G4105 SCM415) having a diameter of 30 mm and a thickness of 2.6 mm was prepared as a base material, and the surface thereof was superfinished. When the surface roughness was measured with a stylus type surface roughness meter, it was Rq = 0.037 μm. Thereafter, ultrasonic cleaning was performed in hexane to remove dirt and oil.

Next, the base material 7 obtained by the above was accommodated in the vacuum vessel 4 as shown in FIG. 2, and it exhausted to 10 ^<-4> Pa through the exhaust port 9 to a vacuum pump. Thereafter, argon was introduced as an atmospheric gas from the gas system pipe 5 and the flow rate was adjusted so that the internal pressure became 1 Pa.
Subsequently, the voltage of the DC power supply 10 was set to 50 to 100 V, and control was performed so that a constant current of 50 A would flow, so that arc discharge occurred between the carbon electrode 6. The carbon plasma generated by this was attracted to the base material 7 by a bias from the DC power source 8 so that a hard carbon film was formed on the base material 7. The bias voltage of the substrate was −200 volts.

  First, film formation was performed in an argon-only atmosphere without adding methane to the atmosphere for 30 minutes under this condition (corresponding to a hard layer), and then methane (argon: methane in a volume ratio) for 1 minute. In this case, the film was formed by adding 2: 1 to the vacuum vessel. This condition was determined based on the results of the following preliminary experiment.

[Preliminary test 1]
[1] Measurement of film-forming rate Using the same base material 7 as described above, a film was formed for 30 minutes under the same conditions and without adding methane to the atmosphere. After film formation, the film thickness was measured with a film thickness tester (Carotest). As a result, a film thickness of 1.2 μm was obtained by film formation for 30 minutes, and therefore the film formation rate when methane was not added (corresponding to a hard layer) was calculated to be 40 nm per minute.
Next, another new base material 7 is prepared, set in the vacuum container 4 in the same manner, and methane is added to the atmosphere, and the other conditions (bias voltage, etc.) are made to be the same, and film formation is performed. Was used as a sample B. The internal pressure of the vacuum vessel at this time is 1.3 Pa. It is the same that the volume ratio of argon and methane is controlled to be 2: 1. In this case, since a film having a thickness of 1.5 μm was formed by the film formation for 30 minutes, the film formation rate was calculated to be 50 nm per minute.
[2] Measurement of surface roughness About sample (a) created by said [1], surface roughness was measured with the stylus type surface roughness meter. As a result, Rq = 0.032 μm. In consideration of filling the valley, the surface soft layer was provided with a thickness of 50 nm, and the film formation time of the soft layer was determined as 1 minute from the film formation rate obtained in [1].
[3] Measurement of hardness The samples A and B prepared in [1] above were measured for micro Vickers hardness by an indentation method using an ultra-micro hardness meter (manufactured by Shimadzu Corporation). The measurement load at this time was 49 × 10 ⁻³ N. As a result, 42 GPa was obtained for the sample A film, and 18 GPa was obtained for the sample B film.
[4] Measurement of hydrogen content Sample A was measured for hydrogen content using Rutherford backscattering method (RBS). As a result, the amount of hydrogen in the film of Sample A was determined to be 0.1 atomic% or less. The amount of hydrogen in the film of sample B was 29 atomic%.

  A base material 7 on which a hard carbon film having a laminated structure of a hard layer and a soft layer (hereinafter referred to as “composite carbon film”) is formed is taken out of the vacuum vessel 4 and the average amount of hydrogen from the surface to 20 nm is 2 Determined by secondary ion mass spectrometry (SIMS). This measured value corresponds to the amount of hydrogen in the soft layer, and as a result of measurement, it was found that 26 atomic% of hydrogen was contained. The amount of hydrogen in the hard layer was estimated to be the same as the value of sample (a) obtained in [4] of the preliminary test (0.1 atomic% or less).

  Moreover, it was Rq = 0.030micrometer when the surface roughness was measured with the stylus type surface roughness meter. In addition, since it is difficult to directly measure the hardness of the hard layer and the soft layer of this composite carbon film, it is estimated that it is equivalent to the hardness of sample A and b in the preliminary experiment, and these values are respectively used. It was decided to replace the measured value.

Next, the surface of the composite carbon film having a laminated structure of the hard layer and the soft layer was polished using diamond abrasive grains (# 8000), and the soft layer of the convex portion was worn to expose the underlying hard layer. The amount to be polished is determined by the surface roughness of the hard layer and the lamination thickness of the soft layer, but is a field that removes about 1 to 2 times, preferably about 1.2 to 1.6 times the lamination thickness of the soft layer. Is good. If the thickness to be removed is small, the hard layer does not appear on the surface, so the coefficient of friction is difficult to decrease. If the thickness to be removed is increased more than necessary, the processing will be expensive.
When the surface roughness after polishing was measured in the same manner, it was Rq = 0.016 μm.
In this example, artificial polishing was performed in order to evaluate the effect at an early stage, but without using polishing, wear generated during use as a sliding part, in particular, initial wear was used. The soft layer on the convex surface may be worn away.

  Next, the friction characteristics of this sample were evaluated by a tribometer (manufactured by CSM, Switzerland). The ball-on-disk method was used for the test. In this test, the ball was fixed on the disk-shaped sample so as not to roll, and the ball was slid. The load was 18 N, the peripheral speed of the pin was 0.01 m / s, and the ball material was carburized. Steel (JIS G4805 SUJ2 material), its diameter is 6 mm.

As the lubricant, commercially available automotive engine oil 5W-30SL was used, and the entire ball and pin were immersed in the lubricant. The oil temperature was set to 80 ° C. with a temperature controller, and after the sample was immersed in oil, the measurement was started after a sufficient time had passed until the temperature of the sample coincided with the temperature of the oil. In consideration of the initial familiarity effect, the measured value at the time when 5 minutes passed from the start of the test was regarded as the friction coefficient of the material. Furthermore, in order to investigate the friction characteristics of the film in more detail, the same samples were evaluated using the following four types of lubricants.
[1] Polyalphaolefin (kinematic viscosity at 80 ° C .: 8.4 cSt)
[2] Add glycerin monooleate to polyalphaolefin of [1] to 1% by mass of total [3] Add 2.5 g of glycerin monooleate to polyalphaolefin of [1] Added to the polyalphaolefin of [4] and [1] to add 1% by mass of trimethylolpropane.

In the above friction characteristic test, except for changing the type of lubricant, the same conditions as the evaluation using the original engine oil 5W-30SL (test machine structure, sliding speed, lubricant temperature, Partner member). Further, since the evaluation is performed while changing the lubricant in the same sample, it goes without saying that the sample and the apparatus are cleaned each time.
Table 1 shows the results of measurement of the coefficient of friction under each condition.

(Comparative Example 1)
In this example, only the hard layer was formed by the arc ion plating method.
That is, as in Example 1 above, disks of the same size made of the same steel type were prepared as the base material and subjected to the same superfinishing process. The surface roughness at this time was Rq = 0.035 μm. Then, ultrasonic cleaning was performed with hexane to remove dirt and oil.

Next, as in Example 1, the base material 7 is housed in the vacuum vessel 4 shown in FIG. 2, and after exhausting to 10 ⁻⁴ Pa through the exhaust port 9 to the vacuum pump, argon is used as the atmospheric gas in the gas system. It was introduced from the pipe 5 and the flow rate was adjusted so that the internal pressure was 1.3 Pa.
Subsequently, only film formation in an argon atmosphere was performed for 30 minutes under the same conditions as in Example 1.

  As a result of measuring the surface roughness of the obtained single-layer hard carbon film with a stylus type surface roughness meter, it was Rq = 0.031 μm. Further, the micro Vickers hardness was 40 GPa, and the amount of hydrogen in the film measured by Rutherford backscattering method (RBS) was 0.1 atomic% or less. Furthermore, the film thickness determined by the Calotest method was 1.4 μm.

  In order to make the conditions uniform, after polishing using diamond abrasive grains for the same time as in Example 1, the friction characteristics were evaluated under the same conditions as in Example 1 above. The results are also shown in Table 1. The surface roughness after polishing with diamond abrasive grains was Rq = 0.030 μm.

(Comparative Example 2)
In this example, only the soft layer was formed by the arc ion plating method.
That is, as in Example 1 above, disks of the same size made of the same steel type were prepared as the base material and subjected to the same superfinishing process. The surface roughness after superfinishing was Rq = 0.040 μm. Similarly, ultrasonic cleaning was performed with hexane to remove dirt and oil.

Next, as in Example 1, the base material 7 is housed in the vacuum vessel 4 shown in FIG. 2, and after exhausting to 10 ⁻⁴ Pa through the exhaust port 9 to the vacuum pump, argon and methane gas are used as the atmospheric gases. It was introduced from the gas system pipe 5 so that the volume ratio was 2: 1, and the flow rate was adjusted so that the internal pressure was 1.3 Pa.
Subsequently, film formation was performed in an argon and methane gas atmosphere for 30 minutes under the same conditions as in Example 1 above.

  As a result of measuring the surface roughness of the obtained single layer carbon film with a stylus type surface roughness meter, Rq was 0.032 μm. Further, the micro Vickers hardness was 18 GPa, and the amount of hydrogen in the film measured by secondary ion mass spectrometry (average of 20 nm from the surface) was 27 atomic%. The film thickness determined by the Calotest method was 2.1 μm.

  Furthermore, after performing polishing using diamond abrasive grains for the same time under the same conditions as in Example 1, the friction characteristics were evaluated under the same conditions as in Example 1 above. The results are also shown in Table 1. The surface roughness after polishing with diamond abrasive grains was Rq = 0.111 μm.

(Example 2)
In this example, a film was formed by a magnetron sputtering method, and the hard gas layer and the soft layer were separately formed by changing the composition of the atmospheric gas as in the first example.
First, as in Example 1 above, disks of the same size made of the same steel type were prepared as the base material, and the same superfinishing process was performed. The surface roughness at this time was Rq = 0.034 μm. Then, ultrasonic cleaning was performed with hexane to remove dirt and oil.

Next, the base material 7 was placed in a vacuum vessel 4 as shown in FIG. 3 and evacuated to 10 ⁻⁴ Pa through an exhaust port 9 to a vacuum pump. Thereafter, argon was introduced as an atmospheric gas from the gas system pipe 5 and the flow rate was adjusted so that the internal pressure became 1 Pa.
Subsequently, a high frequency of 13.56 MHz was sent from the high frequency power supply 11 at an output of 300 W, and carbon plasma was generated from the carbon target 12. A bias was applied to the substrate 7 by a DC power source 8 so that the carbon plasma was attracted to the substrate 7 side. The bias voltage of the substrate was −250V.

  First, film formation was performed in an atmosphere containing only argon without adding methane to the atmosphere for 30 minutes under these conditions (corresponding to a hard layer), and then methane (argon: methane was in a volume ratio) for 2 minutes. In this case, the film was formed by adding 2: 1 to the vacuum vessel. This condition was determined by conducting the following preliminary experiment.

[Preliminary test 2]
[1] Measurement of film formation rate Using the same base material 7 as described above, a film was formed for 30 minutes under the same conditions, but without adding methane to the atmosphere. As a result of measuring the film thickness with a film thickness tester (Carotest) after film formation, a film thickness of 0.6 μm was obtained by film formation for 30 minutes, so when no methane was added (corresponding to a hard layer) The film formation rate was calculated to be 20 nm per minute.
Next, another new base material 7 is prepared and set in the vacuum vessel 4 in the same manner, while methane is added to the atmosphere, and other conditions (bias voltage, etc.) are formed under the same conditions. Was used as a sample D. The internal pressure of the vacuum vessel at this time is 1.3 Pa. It is the same that the volume ratio of argon and methane is controlled to be 2: 1. In this case, since a film having a thickness of 0.75 μm was formed by the film formation for 30 minutes, the film formation rate was calculated to be 25 nm per minute.
[2] Measurement of surface roughness With respect to the sample C prepared in the above [1], the surface roughness was measured with a stylus type surface roughness meter. As a result, Rq = 0.033 μm. In consideration of filling the valley, the surface soft layer was provided with a thickness of 50 nm, and the film formation time of the soft layer was determined to be 2 minutes from the film formation rate obtained in [1].
[3] Measurement of hardness The sample V and d prepared in [1] above were measured for micro Vickers hardness by an indentation method. The measurement load was 49 × 10 ⁻³ N. As a result, 41 GPa was determined for the sample film and 20 GPa for the sample film.
[4] Measurement of hydrogen content For sample c, the hydrogen content was measured using Rutherford backscattering method (RBS). As a result, the amount of hydrogen in the film of Sample A was determined to be 0.1 atomic% or less. The amount of hydrogen in the sample film was 32 atomic%.

The base material 7 on which the composite carbon film was formed was taken out of the vacuum vessel 4 and the average amount of hydrogen from the surface to 20 nm was determined by secondary ion mass spectrometry (SIMS). This measured value corresponds to the amount of hydrogen in the soft layer and was found to contain 34 atomic% of hydrogen. The amount of hydrogen in the hard layer was estimated to be equivalent to the value of sample C obtained in [4] of the preliminary test (0.1 atomic% or less). The surface roughness was Rq = 0.035 μm.
In addition, since it is difficult to directly measure the hardness of the hard layer and the soft layer of the composite carbon film, the measured values of the sample C and d in the preliminary experiment were replaced with the respective measured values.

Next, the surface of the composite carbon film was polished with diamond abrasive grains (# 8000), and the soft layer of the convex portion was abraded so that the underlying hard layer was exposed. When the surface roughness after polishing was measured in the same manner, it was Rq = 0.014 μm.
Then, the friction characteristics of the obtained sample were evaluated by the same method as in Example 1. The results are also shown in Table 1.

(Comparative Example 3)
In this example, only the hard layer was formed by the magnetron sputtering method as in Comparative Example 1 above.
First, as in Example 1 above, disks of the same size made of the same steel type were prepared as the base material, and the same superfinishing process was performed. The surface roughness was Rq = 0.037 μm. Then, ultrasonic cleaning was performed in hexane to remove dirt and oil.

Next, as in Example 2, the base material 7 is housed in the vacuum vessel 4 shown in FIG. 3, and after exhausting to 10 ⁻⁴ Pa through the exhaust port 9 to the vacuum pump, argon is used as the atmospheric gas. It was introduced from the system pipe 5 and the flow rate was adjusted so that the internal pressure became 1 Pa.
Subsequently, film formation was performed in an argon atmosphere for 60 minutes under the same conditions as in Example 2 above.

  As a result of measuring the surface roughness of the obtained single-layer hard carbon film with a stylus type surface roughness meter, Rq was 0.035 μm. Further, the micro Vickers hardness was 39 GPa, and the hydrogen content in the film measured by Rutherford backscattering method (RBS) was 0.1 atomic% or less. Furthermore, the film thickness determined by the Calotest method was 1.1 μm.

  Similarly, in order to make the conditions uniform, after performing polishing using diamond abrasive grains for the same time under the same conditions as in Example 1, the friction characteristics were evaluated under the same conditions as in Example 1 above. did. The results are also shown in Table 1. The surface roughness after polishing with diamond abrasive grains was Rq = 0.030 μm.

(Comparative Example 4)
In this example, only the soft layer was formed by the magnetron sputtering method as in Comparative Example 1 above.
That is, as in Example 1 above, disks of the same size made of the same steel type were prepared as the base material and subjected to the same superfinishing process. The surface roughness after superfinishing was Rq = 0.040 μm. Similarly, ultrasonic cleaning was performed with hexane to remove dirt and oil.

Next, as in Example 2, the base material 7 was housed in the vacuum vessel 4 shown in FIG. 3 and evacuated to 10 ⁻⁴ Pa through the exhaust port 9 to the vacuum pump. Was introduced from the gas system pipe 5 so that the volume ratio was 2: 1, and the flow rate was adjusted so that the internal pressure was 1.3 Pa.
Subsequently, film formation was performed in an argon and methane gas atmosphere for 40 minutes under the same conditions as in Example 2 above.

  As a result of measuring the surface roughness of the obtained single layer carbon film with a stylus type surface roughness meter, Rq was 0.028 μm. Moreover, the micro Vickers hardness was 17 GPa, and the amount of hydrogen in the film measured by secondary ion mass spectrometry was 25 atomic%. And the film thickness calculated | required by the Calotest method was 1.0 micrometer.

  Further, after polishing was performed using diamond abrasive grains for the same time under the same conditions as in Example 1, the friction characteristics were evaluated under the same conditions as in Example 1 above. The results are also shown in Table 1. The surface roughness after polishing with diamond abrasive grains was Rq = 0.014 μm.

From the above results, in the hard carbon film having the same laminated structure as the hard carbon film sliding member of the present invention, as can be seen from the comparison between Example 1 and Comparative Example 1, the whole is a hard layer. In comparison, a smooth surface can be easily obtained and the friction coefficient is reduced. The same applies to the comparison between Example 2 and Comparative Example 3.
In addition, as can be seen from the comparison between Example 1 and Comparative Example 2, even though the ease of obtaining a smooth surface is the same as in the case where the whole is a soft layer, It was confirmed that a lower coefficient of friction was exhibited by the appearance of the base hard layer on the surface after the abrasion due to the effect considered to be the affinity relationship with the lubricant and additive. This is the same in the comparison between Example 2 and Comparative Example 4.

As described above, in the hard carbon film sliding member of the present invention, a low coefficient of friction can be easily obtained in the simplicity of film formation while being equivalent to a sliding member having a conventional hard carbon film. It has excellent characteristics.
Further, from the above results, an example in which the hard carbon film of Example 1 is used in combination with a lubricating oil of 2.5% by mass of polyalphaolefin + glycerin monooleate is most preferable.

It is sectional drawing which shows typically the laminated structure of the hard carbon film in the sliding member of this invention. It is a schematic explanatory drawing which shows the film-forming apparatus by an arc ion plating method. It is a schematic explanatory drawing which shows the film-forming apparatus by a magnetron sputtering method.

Explanation of symbols

1 Soft layer (outermost layer)
2 Hard layer 3 Base material

Claims (12)

  A hard carbon film sliding member having a laminated structure of hard carbon films composed of two or more layers, and comprising a hard layer having a hardness higher than that of the outermost layer on the lower layer side of the outermost layer.   The hard carbon film sliding member according to claim 1, wherein a ratio of hydrogen atoms in the outermost layer is higher than that of the hard layer.   The hard carbon film sliding member according to claim 1 or 2, wherein a ratio of hydrogen atoms in the hard layer is 1 atomic% or less.   The hard carbon film sliding member according to claim 1 or 2, wherein a ratio of hydrogen atoms in a layer located on the most surface side among layers having higher hardness than the outermost layer is 1 atomic% or less.   The hard carbon film sliding member according to any one of claims 1 to 4, wherein the hard carbon film sliding member is used in a lubricant.   The hard carbon film sliding member according to claim 5, wherein the base oil of the lubricant is polyalphaolefin.   The hard carbon film sliding member according to claim 5 or 6, wherein the lubricant contains at least one additive having a hydroxyl group.   The hard carbon film sliding member according to claim 7, wherein at least one of the additives contained in the lubricant contains two or more hydroxyl groups in the molecule.   The hard carbon film sliding member according to any one of claims 5 to 8, wherein at least one of the additives contained in the lubricant is an ester.   The hard carbon film sliding member according to claim 9, wherein the ester is a monoester of glycerin.   When forming the laminated structure of the hard carbon film sliding member according to any one of claims 1 to 10, the hydrogen partial pressure or hydrocarbon gas partial pressure in the atmosphere is changed during film formation by a vapor phase method. A manufacturing method of a hard carbon film sliding member characterized by making it.   The method for producing a hard carbon film sliding member according to claim 11, wherein the outermost surface layer is polished after forming the laminated structure.

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