JP2013253291A - Sliding member and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a sliding member in which friction in lubricating oil is sufficiently reduced; and a method of manufacturing the sliding member.SOLUTION: A member that slides under the presence of lubricating oil includes: a base material; and a carbon film disposed at a part that slides with a mating member in the base material, wherein in the carbon film, a ratio of a carbon-hydrogen bond to a carbon-carbon bond is less than 0.59 in a surface thereof. In addition, in the carbon film, a ratio of an sp3 carbon-hydrogen bond to an sp3 carbon-carbon bond is less than 0.57 in a surface thereof.

Description

  The present invention relates to a sliding member and a manufacturing method thereof, and more particularly, to a sliding member used in an environment where lubricating oil exists and a manufacturing method thereof.

  Reducing friction in the sliding member is important not only for extending the life of the sliding member but also for improving energy efficiency. The surface characteristics of the sliding member greatly affect the friction of the sliding member. Furthermore, mechanical parts that slide in lubricating oil such as an internal combustion engine need to consider the interaction between the lubricating oil and the surface of the sliding member.

  In order to reduce the friction of the sliding member, it has been studied to form a hard carbon film such as a diamond-like carbon (DLC) film on the surface of the sliding member. Furthermore, in order to reduce the friction of the sliding member in the lubricating oil, the use of a DLC film having a low hydrogen content has been studied (for example, see Patent Document 1).

JP 2000-297373 A

  However, the interaction between the lubricating oil and the DLC film varies greatly depending on the surface state of the DLC film. For this reason, even if the hydrogen content of the entire DLC film is controlled, the required characteristics are not always obtained. The inventors of the present application have found that the state of carbon-hydrogen bonds (C—H) on the surface of the DLC film greatly affects the friction in the lubricating oil.

  The present disclosure makes it possible to realize a sliding member with sufficiently reduced friction in the lubricating oil based on the obtained knowledge.

  The sliding member of the present disclosure includes a sliding surface that slides with a mating member in the presence of lubricating oil, and a carbonaceous film provided on the sliding surface. The ratio of hydrogen bonds to carbon-carbon bonds is less than 0.59.

In the sliding member of the present disclosure, carbonaceous film, in its surface, sp ³ carbon - sp ³ carbon hydrogen bonds - the ratio carbon bonds may be less than 0.57.

In the sliding member of the present disclosure, carbonaceous film, in its surface, sp ² carbon - sp ² carbon hydrogen bonds - the ratio carbon bonds may be less than 0.58.

  In the sliding member of the present disclosure, the carbonaceous film may have a hydrogen content of 2 atomic% or less.

  In the sliding member of the present disclosure, the carbonaceous film may have an arithmetic average surface roughness Ra of 0.1 μm or less.

  In the sliding member of the present disclosure, the carbonaceous film may be provided on the surface of the member via an intermediate layer.

The manufacturing method of the 1st sliding member in this indication is provided with the process of forming a carbonaceous film on the surface of the substrate of a sliding member, and the process of forming a carbonaceous film makes graphite a target, and uses a sputtering power supply. It is performed by a sputtering method using a DC pulse power supply, the absolute value of the average output of the pulse power supply is 2.7 Wcm ^-2 or more, the pulse frequency of the pulse power supply is 250 kHz or more and 1 MHz or less, and the duty ratio of the pulse power supply is more than 15% A carbonaceous film having a large ratio of 90% or less and a ratio of carbon-hydrogen bonds to carbon-carbon bonds on the surface of less than 0.59 is formed.

The second manufacturing method of the sliding member in the present disclosure includes a step of forming a carbonaceous film on the surface of the base material of the sliding member, and the step of forming the carbonaceous film uses graphite as a target and a sputtering power source. Performed by sputtering using a direct current pulse power supply, the absolute value of the maximum current density of the pulse power supply is set to be larger than 55.8 mAcm ⁻² , the pulse frequency of the pulse power supply is set to 250 kHz or more and 1 MHz or less, and carbon-hydrogen bonds on the surface A carbonaceous film having a ratio of carbon-carbon bonds of less than 0.59 is formed.

In the first and second sliding member manufacturing methods, the absolute value of the average power density on the substrate side may be larger than 19.7 mWcm ⁻² in the step of forming the carbonaceous film.

  According to the sliding member and the manufacturing method thereof according to the present invention, it is possible to realize a sliding member in which friction in the lubricating oil is sufficiently reduced.

It is the schematic which shows an example of the film-forming apparatus.

First, the characteristics of the carbonaceous film found by the present inventors will be described. The carbonaceous film is a film containing sp ² carbon-carbon bonds (graphite bonds) and sp ³ carbon-carbon bonds (diamond bonds) represented by diamond-like carbon (DLC) films. It may be an amorphous film such as a DLC film or a crystalline film such as a diamond film. In the following description, it is assumed that the carbonaceous film is a DLC film.

The DLC film can be formed by various methods such as chemical vapor deposition (CVD), laser ablation, and sputtering. In general, hydrocarbon is used as a raw material in the CVD method. When a DLC film is formed using a hydrocarbon as a raw material, hydrogen in the raw material is taken into the film, and thus the DLC film contains many sp ² carbon-hydrogen bonds and sp ³ carbon-hydrogen bonds. On the other hand, in the sputtering method or the like, a DLC film can be formed using a raw material such as graphite. If the raw material is graphite containing no hydrogen, theoretically, a DLC film containing no carbon-hydrogen bonds should be formed. However, because of the influence of moisture in the atmosphere, hydrogen is contained in the film by several% to 5% even in a DLC film formed using a raw material not containing hydrogen such as graphite.

  It is known that the concentration of hydrogen contained in the DLC film affects the friction characteristics of the DLC film. However, even with DLC films having the same hydrogen concentration, the friction characteristics may be greatly different. Analysis of hydrogen contained in a DLC film is not easy, and generally only the concentration of the entire film is required. The inventors of the present application have revealed the bonding state of hydrogen on the surface of the DLC film by using an X-ray photoelectron spectroscopy (XPS) method and curve fitting. As a result, even if the hydrogen concentration of the entire DLC film is reduced, a DLC film having good friction characteristics in the presence of lubricating oil can be obtained if the hydrogen bonding state on the surface of the DLC film is not appropriate. It became clear that there was no.

  According to the knowledge of the present inventors, the ratio [C—H] / [C—C] of the carbon-hydrogen bond (C—H) to the carbon-carbon bond (C—C) on the surface of the DLC film is made as small as possible. It is important to improve the friction characteristics in the presence of lubricating oil. Specifically, [CH] / [CC] is preferably less than 0.59. [CH] / [CC] is more preferably 0.50 or less, and further preferably 0.41 or less.

Furthermore, the ratio [sp ² C—H] / [sp ² C—C] of sp ² carbon-hydrogen bond (sp ² C—H) to sp ² carbon-carbon bond (sp ² C—C) is 0.58. Is preferably less than 0.55, more preferably 0.55 or less, and even more preferably 0.51 or less. The ratio [sp ³ C—H] / [sp ³ C—C] of sp ³ carbon-hydrogen bond (sp ³ C—H) to sp ³ carbon-carbon bond (sp ³ C—C) is less than 0.57 Preferably, it is 0.50 or less, more preferably 0.29 or less.

[C—H], [sp ² C—H], [sp ³ C—H], [C—C], [sp ² C—C] and [sp ³ C—C] It can be measured by a method using the XPS method and curve fitting described in detail.

  In order to reduce the C—H bond on the surface, it is preferable to reduce the hydrogen concentration of the entire DLC film. Therefore, the hydrogen concentration of the entire DLC film is preferably 2 atomic% (at%) or less, and more preferably 1.2 atomic% or less. The hydrogen concentration of the entire DLC film can be measured by a high resolution-elastic recoil detection analysis (HR-ERDA) described in detail in the examples. In addition, atomic% represents the number of atoms of a certain element when the number of atoms of the whole substance is 100.

  A DLC film having a small [C—H] / [C—C] on the surface can be formed using a sputtering method, an arc ion plating method, a laser ablation method, electron beam evaporation, or the like. Among these, the sputtering method is preferable because a phenomenon called droplets in which hard particles adhere to the film formation surface hardly occurs.

  In the sputtering method, sputtering gas is ionized and collided with a solid target as a raw material to eject target particles. The ejected target particles reach the workpiece (base material) side, thereby depositing target particles on the surface of the base material. To form a film. The film structure obtained by sputtering is generally shown by the “Thornton” zone model (JA Thornton: Ann. Rev. Mater. Sci., 7 (1977) 239.). It is known that changes occur in the structure. This is because atoms in the deposition process receive heat energy from the substrate and are easily moved. However, when the base material is steel, when a temperature exceeding the tempering temperature is applied, the hardness is lowered and it is difficult to maintain the wear resistance. For example, if the base material is carbon steel for machine structure or alloy steel for machine structure, the upper limit of general heating is 200 ° C. Therefore, it is preferable to change the film structure without heating the substrate as a means for controlling the film structure.

  In addition to the transfer of heat from the substrate, the coating structure is expected to change by changing the energy of the particles themselves entering the substrate. However, the target particles as the raw material are secondary particles obtained by being ejected from the target by the collision of the sputtering gas particles. Therefore, the ionization rate of the target particles is low compared with the method using electron beam or arc ion that directly sublimates the target material, and it is not easy to obtain any film structure by directly controlling the energy of the target particle ions. Absent.

  On the other hand, in the sputtering method, the sputtering gas particles are ionized in addition to the target particles. Sputtering gas particles go to the target and partly go directly to the substrate. In addition, some of the sputtered gas particles directed toward the target are reflected on the surface of the target and travel toward the substrate. As described above, in the formation of the DLC film by the sputtering method, it is expected that the film structure is changed not only by the energy of the target particles but also by the energy of the sputter gas particles colliding with the surface of the film in the deposition process.

  Next, regarding the sputtering power source, when a pulse power source is used as the sputtering power source, it is expected that the transient power characteristics of the pulse will affect the energy of the sputtering gas particles and the target particles. When discharge is generated by a pulse power supply, the current flowing through the target increases greatly at the moment when power is applied. That is, a transient current flows at the rise of the pulse power. It became clear that the transient power at the rise of the pulse power is increased by increasing the pulse frequency. It is expected that the energy of the sputter gas particles will increase as the transient power at the rise of the pulse power increases. When the energy of the sputtering gas particles is increased, the energy when the sputtering gas particles collide with the workpiece can be increased. For this reason, it is considered that light hydrogen atoms are repelled from the surface of the workpiece, and carbon-hydrogen bonds on the surface of the DLC film can be reduced. However, it is known that if the pulse frequency is increased too much, the target current decreases conversely (for example, M. Yamashita J. Vac. Sci. Technol. A, 7 (1989) 2752.).

  The pulse duty ratio also affects the transient power at the rise of the pulse power. When the duty ratio decreases, the transient power at the rise of the pulse power decreases, and when the duty ratio increases, the transient power at the rise of the pulse power increases. For this reason, the duty ratio is preferably larger than 15%, more preferably 20% or more, and further preferably 40% or more. However, if the duty ratio becomes too large, the merit of pulse power for suppressing arcing is impaired, so 90% or less is preferable, and 80% or less is more preferable.

  On the other hand, it is also important to make particles enter the work efficiently. By using an unbalanced magnetron sputtering method in which the magnetic field is directed toward the substrate, particles can be efficiently incident on the substrate. Further, by using an auxiliary electrode that forms plasma in a magnetic field region facing the substrate, it is possible to control the ion density toward the substrate. Therefore, by arranging an auxiliary magnetic pole for the purpose of introducing a magnetic field toward the substrate and by arranging an auxiliary electrode for the purpose of controlling the ion density toward the substrate, it is possible to control particles even when sputtering difficult to ionize carbon. The efficiency can be improved, and the energy of the sputtering gas particles directed toward the substrate can be easily controlled, and the power input to the workpiece, that is, the amount and energy of ions can be increased.

  For this reason, when forming a DLC film, it is preferable to use a direct current pulse power supply as a sputtering power supply and to make the frequency as high as possible. Specifically, the pulse frequency is preferably 250 kHz or more, and more preferably 300 kHz or more. However, if the pulse frequency is set too high, the target current will decrease, conversely, it is preferably 1 MHz or less.

The absolute value of the average power density of the target (cathode) side is preferably set to 2.7Wcm ^-2 or more, and even more preferably from 3.6Wcm ^-2 or more. The maximum current density of the target (cathode) side is preferably larger than 55.8MAcm ^-2, more preferably to 60.0MAcm ^-2 or more, and even more preferably from 67.3MAcm ^-2 or . The absolute value of the average power density of the workpiece side is preferably larger than 19.7MWcm ^-2, more preferably to 25.0MWcm ^-2 or more, and even more preferably from 28.0MWcm ^-2 or more. The temperature of the substrate is desirably 200 ° C. or lower.

  Generally, argon is used as the sputtering gas, but other rare gases such as krypton and xenon, nitrogen, or the like may be used.

  Any apparatus may be used for forming the DLC film. For example, a magnetron sputtering apparatus as shown in FIG. 1 can be used. As shown in FIG. 1, a target base 211 incorporating a magnet is provided in the lower portion of the chamber 221, and a target 207 is disposed on the target base 211. Above the chamber 221, a work holder 210 that is in an electrically floating state (floating) and to which a bias voltage can be applied is provided, and the work 208 is held by the work holder 210. Inside the target table 211, a central magnet 201 is disposed at a position corresponding to the center of the target 207, and outer peripheral magnets 202 are disposed at equal intervals at a position corresponding to the periphery of the target 207. The center magnet 201 is arranged with the S pole facing the target 207, and the outer peripheral magnet 202 is arranged with the N pole facing the target 207.

  On the outer side of the outer wall of the chamber 221, four first external magnets 203 and four second external magnets 204 are arranged so as to overlap each other corresponding to each of the four outer peripheral magnets. The first external magnet 203 and the second external magnet 204 are respectively arranged with the north pole as the central magnet 201 side. The first external magnet 203 and the second external magnet 204 each function as an auxiliary magnetic pole.

  A coil 205 that functions as an auxiliary electrode is provided inside the chamber 221. The coil 205 is wound in a spiral shape, and one end is connected to the high-frequency power source 213 via the matching circuit 212. In FIG. 1, the other end of the coil 205 is free and not connected anywhere, but may be connected to ground or a high-frequency power source.

  A sputtering power source 215 is connected to the target table 211 via a low-pass filter 214. A bias power source 218 is connected to the work holder 210 via a low pass filter 216.

  By providing the second external magnet 204, a strong magnetic field directed toward the workpiece 208 can be formed. Thereby, ions can be efficiently incident on the surface of the workpiece 208 along the magnetic field. Further, by providing the coil 205, the plasma density incident on the workpiece surface can be increased, and a dense and uniform DLC film can be formed at high speed. Since ions include Ar ions of the sputtering gas in addition to the target carbon particles, the effect of repelling light hydrogen while depositing carbon is improved. For this reason, the effect which reduces the carbon-hydrogen bond in the surface of a DLC film can be made higher. However, the DLC film may be formed using such a normal multi-pole magnetron sputtering apparatus that does not have the second external magnet and coil, or a normal flat-plate magnetron sputtering apparatus that does not have an external magnet. .

  The thickness of the DLC film is preferably thick to some extent, preferably 0.001 μm or more, and more preferably 0.005 μm or more. However, since it becomes difficult to form as the film thickness increases, the thickness is preferably 10 μm or less, and more preferably 3 μm or less. Also, friction is reduced when the surface of the DLC film is as smooth as possible. For this reason, it is preferable that arithmetic mean roughness Ra on the surface is 0.1 μm or less.

The DLC film can be directly formed on the surface of the coating target, but an intermediate layer may be provided between the coating target and the DLC film in order to make the coating target and the DLC film adhere more firmly.
Good.

  As the material of the intermediate layer, various materials can be used depending on the type of the object to be coated, but from silicon (Si), titanium (Ti), chromium (Cr), tungsten (W), or aluminum (Al). An amorphous film or the like can be used. Alternatively, an amorphous film in which these elements and at least one of carbon (C) and nitrogen (N) are mixed can be used. The thickness is not particularly limited, but is preferably 0.001 μm or more, and more preferably 0.005 μm or more. Moreover, 1 micrometer or less is preferable and 0.3 micrometer or less is more preferable. The intermediate layer may be formed using, for example, a sputtering method, a CVD method, a plasma CVD method, a thermal spraying method, an ion plating method, an arc ion plating method, or a vacuum deposition method. Further, wet chrome plating may be used.

  The DLC film may contain elements other than carbon and hydrogen. For example, silicon (Si) or fluorine (F) may be added. In addition, titanium (Ti), chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni), zinc (Zn), gallium (Ga), niobium (Nb), molybdenum (Mo) or tungsten (W ) Etc. may be included. Titanium (Ti), chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni), zinc (Zn), gallium (Ga), niobium (Nb), molybdenum (Mo), tungsten (W), etc. As a result, an additive film is formed on the surface of the DLC film, and the effect of obtaining a low coefficient of friction is obtained. On the other hand, in order to more easily control the bonding state of hydrogen on the surface of the DLC film, an element other than carbon and hydrogen may be included. In addition, the structure which does not contain another element said here includes the case where it contains a trace amount of impurities.

  The friction characteristics of the DLC film in the lubricating oil are also affected by the surface roughness of the DLC film. The friction characteristic improves as the surface roughness of the DLC film is as small as possible. Further, the opponent's aggression property for wearing the counterpart material can be reduced when the surface roughness is small. Specifically, the arithmetic average surface roughness Ra on the surface of the DLC film is preferably 0.1 μm or less.

  The DLC film should just be formed in the sliding surface of a pair of sliding member which mutually slides in the environment where lubricating oil exists. A DLC film may be formed on each of the pair of sliding surfaces, or a DLC film may be formed only on one of the sliding surfaces. When a DLC film is formed on each of the sliding surfaces, a DLC film having the same composition may be formed on both sides, or DLC films having different compositions may be formed on both sides. Moreover, the DLC film may be formed also in parts other than the sliding surface of a sliding member.

  The sliding member on which the DLC film is formed can be applied to any member that requires sliding in an environment where lubricating oil is present. Specifically, valve lifters, piston rings, piston pins, piston skirts, cam lobes, cam journals, crankshafts, connecting rods, mission gears, mission primary shafts, mission secondary shafts, spline shafts, friction plates, separator plates, clutch housings The present invention can be applied to a differential gear, a rotary vane, a timing chain, and the like, and these two or more types may be targeted. The base material of the sliding member may be any material. Specifically, metal, ceramics, resin, or a composite material thereof can be used.

  The environment in which the lubricating oil is present only needs to be a layer of lubricating oil having a thickness of a monomolecular layer or more at the interface between the pair of sliding surfaces. This includes not only the case where the lubricating oil is present on the entire interface, but also the case where the lubricating oil is present on a part of the interface. Moreover, the case where a part or all of the sliding member having the sliding surface is immersed in the lubricating oil is also included as long as the lubricating oil exists at the interface.

  The lubricating oil that can be combined with the sliding member is not particularly limited, and any type of lubricating oil can be used as long as it is normally used as a lubricating oil such as mineral oil, synthetic oil, fat or a mixture thereof. be able to. More preferably, a lubricating oil containing an oily material made of ester is desirable. In addition to the base oil, the lubricating oil may contain components such as a stabilizer, an antioxidant, a dispersant, a detergent, and a viscosity modifier. The lubricating oil also includes semi-solid grease.

  Next, the present invention will be described in more detail with reference to examples. The present invention is not limited to the following examples, and various improvements and design changes may be made without departing from the spirit of the present invention.

(DLC film composition evaluation method)
-Hydrogen concentration-
The concentration of hydrogen contained in the DLC film was measured by a high resolution elastic recoil detection analysis (HR-ERDA). For the measurement, a high resolution RBS analyzer HRBS500 manufactured by Kobe Steel was used. The sample was irradiated with N ₂ ⁺ ions at an angle of 70 degrees with respect to the normal of the sample surface, and the recoiled hydrogen ions were detected by a polarized magnetic field energy analyzer. Incident ions have an energy per atomic nucleus of 240 KeV. The scattering angle of hydrogen ions was 30 degrees. The ion irradiation amount was determined by vibrating the pendulum in the beam path and measuring the amount of current irradiated to the pendulum. The sample current was about 2 nA, and the irradiation dose was about 0.3 μC.

With respect to the obtained data, a process of converting the channel on the horizontal axis into the energy of recoil ions and a process of subtracting the background of the system were performed with reference to the midpoint of the edge on the high energy side in the hydrogen peak. Simulation fitting was performed on the processed data, and a hydrogen depth profile was obtained for a range from the surface to 12 nm. Furthermore, it converted into the ratio (at%) of the hydrogen atom with respect to all the atoms contained in a DLC film. At this time, it was assumed that the constituent elements of the sample were only carbon and hydrogen. When the horizontal axis of the depth profile was converted to nm units, the density of the DLC film was assumed to be that of graphite (2.25 g / cm ³ ). The quantitative value was calibrated by measuring a DLC film having a known concentration formed by a sputtering method. It was also assumed that there was a contaminated layer consisting of hydrocarbons on the outermost surface. The density of the contaminated layer was paraffin density (0.89 g / cm ³ ).

(DLC film composition analysis method)
The DLC film composition was evaluated by X-ray photoelectron spectroscopy (XPS) measurement. JPS-9010 manufactured by JEOL Ltd. was used for XPS measurement. The XPS measurement conditions were such that the detection angle with respect to the sample was 90 degrees, Al was used as the X-ray source, and the X-ray irradiation energy was 100 W. One measurement time was 0.2 ms, and one sample was measured 32 times. Considering the inelastic mean free process of photoelectrons traveling in carbon, it is considered that the measurement is performed in the range from the surface to 9 nm. Furthermore, the photoelectrons become difficult to escape as they get deeper from the surface, and the detection of photoelectrons attenuates as they get deeper from the surface. Therefore, it is considered that 50% of the information measured this time is occupied by information on the outermost layer from the surface to approximately 1.5 nm.

The carbon 1s (C1s) peak obtained by XPS measurement is represented by sp ³ C—C in which the carbons are sp ³ bonded, sp ² C—C in which the carbons are sp ² bonded, and sp in which carbon and hydrogen are sp ³ bonded. ^It was decomposed by curve fitting into 4 components of ³ C—H and sp ² C—H in which carbon and hydrogen were sp ² bonded. The bond energy of sp ³ C—C is 283.8 eV, the bond energy of sp ² C—C is 284.3 eV, the bond energy of sp ³ C—H is 284.8 eV, and the bond energy of sp ² C—H is 285. 3 eV. The area of each peak obtained by curve fitting is the area of the peak of sp ³ C—C, the area of the peak of sp ² C—C, the area of the peak of sp ³ C—H, and the area of the peak of sp ² C—H. The value divided by the total sum of the values was taken as the composition ratio of each component. The sum of the composition ratio of sp ³ C—C and the composition ratio of sp ² C—C is the composition ratio of C—C, and the sum of the composition ratio of sp ³ C—H and the composition ratio of sp ² C—H is The composition ratio was C—H.

(DLC film surface roughness)
The surface roughness of the DLC film was evaluated by the arithmetic average surface roughness Ra. The arithmetic average surface roughness Ra was determined according to JIS B-0601. For the measurement of the surface roughness, a surface roughness measuring machine (Mitutoyo Corp .: SurfTest501) was used.

Example 1
A DLC film was formed on the end face of a disk made of alloy tool steel (JIS: SKD11) adjusted to HRC hardness 60 using the magnetron sputtering apparatus shown in FIG. Tetramethylsilane (Si (CH ₃ ) ₄ ) was introduced into the chamber, a bias voltage of 1 kV was applied to the substrate, and discharge was performed for 30 minutes. Graphite was used for the target 207 and argon was used for the sputtering gas. A DC pulse power source was used as the sputtering power source 215, the pulse frequency was 300 kHz, the duty ratio was 40%, and the absolute value of the average power density on the target side was 3.6 Wcm ⁻² . The absolute value of the maximum current density was 68.2 mAcm ⁻² . Argon was used as the sputtering gas.

The absolute value of the average power density on the workpiece side, which is an index of the energy of particles that reached the workpiece side, was 28.0 mW / cm ² . The power density was obtained from the current value obtained by the current measuring means, the bias voltage applied to the work holder 210, and the surface area of the work holder 210. Film formation was performed for 60 minutes, the average value of the power density during that time was determined, and the value divided by the substrate surface area was taken as the average power density. Further, the pulse waveform was analyzed to obtain the maximum current in one pulse section, and the value divided by the target area was taken as the maximum current density. For the pulse waveform, a current probe was installed on the target power output cable, and the pulse output waveform during discharge was measured with an oscilloscope (LECROY: WS64Xs).

The friction coefficient of the disk on which the DLC film was formed was measured according to JIS-K7218. For the measurement, a friction wear tester (Orientec Co., Ltd .: EKM-III1010) was used, and the measurement was performed by a ring-on-disk method. The ring was made of high carbon steel for machine structure (S45C) with HRC hardness adjusted to 50. The inner diameter of the ring was 20 mm, and the outer diameter was 25.6 mm. The ring was pressed against the disk on which the DLC film was formed with a load of 100 kgf and rotated at a rotation speed of 200 rpm. The frictional force received by the torque arm due to rotation was measured with a load cell, and the friction coefficient μ was determined from the average frictional force using the following equation (1). The position for measuring the frictional force was set at a distance of 150 mm from the center of rotation via the torque arm. The test was performed in a normal temperature lubricating oil. As the lubricating oil, chemically synthesized oil 0W-40 (SN standard) was used.
μ = (F × R) / (W × r) (1)
Where F is the frictional force, W is the pressing load, R is the distance from the rotational center of the frictional force gauge, and r is the value obtained by dividing the sum of the ring outer radius and the ring inner radius by 2, that is, the ring radius center.

The hydrogen concentration of the obtained DLC film was 0.9 atomic%. [Sp ³ C—C] was 0.34, [sp ² C—C] was 0.37, [sp ³ C—H] was 0.10, and [sp ² C—H] was 0.19. . Therefore, [C-C] was 0.71, [C-H] was 0.29, and [C-H] / [C-C] was 0.41. [Sp ² C—H] / [sp ² C—C] was 0.51, and [sp ³ C—H] / [sp ³ C—C] was 0.29. The friction coefficient μ was 0.23. The arithmetic average surface roughness Ra on the surface of the obtained DLC film was 0.1 μm or less.

(Example 2)
A DLC film was formed in the same manner as in Example 1 with a pulse frequency of 350 kHz when forming the DLC film, and the friction coefficient was measured. The absolute value of the average power density on the target side was 4.1 W / cm ² , and the absolute value of the maximum current density was 67.3 cm ⁻² . The absolute value of the average power density on the workpiece side was 28.7 mW / cm ² .

The hydrogen concentration of the obtained DLC film was 1.1 atomic%. [Sp ³ C—C] was 0.38, [sp ² C—C] was 0.39, [sp ³ C—H] was 0.06, and [sp ² C—H] was 0.17. . Therefore, [C-C] was 0.77, [C-H] was 0.23, and [C-H] / [C-C] was 0.30. [Sp ² C—H] / [sp ² C—C] was 0.44, and [sp ³ C—H] / [sp ³ C—C] was 0.16. The coefficient of friction was 0.023. The arithmetic average surface roughness Ra on the surface of the obtained DLC film was 0.1 μm or less.

(Comparative Example 1)
The DLC film was formed in the same manner as in Example 1 with the pulse frequency when forming the DLC film being 100 kHz, and the friction coefficient was measured. The absolute value of the average power density on the target side was 2.0 W / cm ² , and the absolute value of the maximum current density was 20.6 mAcm ⁻² . The absolute value of the average power density on the workpiece side was 17.2 mW / cm ² .

The resulting DLC film had a hydrogen concentration of 1.2 atomic%. [Sp ³ C—C] was 0.23, [sp ² C—C] was 0.40, [sp ³ C—H] was 0.13, and [sp ² C—H] was 0.23. . Therefore, [C—C] was 0.63, [C—H] was 0.36, and [C—H] / [C—C] was 0.61. [Sp ² C—H] / [sp ² C—C] was 0.62, and [sp ³ C—H] / [sp ³ C—C] was 0.59. The coefficient of friction was 0.045. The arithmetic average surface roughness Ra on the surface of the obtained DLC film was 0.1 μm or less.

(Comparative Example 2)
The DLC film was formed in the same manner as in Example 1 with the pulse frequency when forming the DLC film being 200 kHz, and the friction coefficient was measured. The absolute value of the average power density on the target side was 2.6 W / cm ² , and the absolute value of the maximum current density was 55.8 mAcm ⁻² . The absolute value of the average power density on the workpiece side was 19.7 mW / cm ² .

The hydrogen concentration of the obtained DLC film was 0.9 atomic%. [Sp ³ C—C] was 0.23, [sp ² C—C] was 0.40, [sp ³ C—H] was 0.14, and [sp ² C—H] was 0.23. . Therefore, [C-C] was 0.63, [C-H] was 0.37, and [C-H] / [C-C] was 0.59. [Sp ² C—H] / [sp ² C—C] was 0.58, and [sp ³ C—H] / [sp ³ C—C] was 0.61. The coefficient of friction was 0.047. The arithmetic average surface roughness Ra on the surface of the obtained DLC film was 0.1 μm or less.

(Comparative Example 3)
A DLC film was formed in the same manner as in Example 1 except that the DC power source was used instead of the DC pulse power source for forming the DLC film, and the friction coefficient was measured. The absolute value of the average power density on the target side was 0.5 W / cm ² , and the absolute value of the average power density on the workpiece side was 0 W / cm ² .

The resulting DLC film had a hydrogen concentration of 1.2 atomic%. [Sp ³ C—C] was 0.15, [sp ² C—C] was 0.39, [sp ³ C—H] was 0.16, and [sp ² C—H] was 0.29. . Therefore, [C—C] was 0.54, [C—H] was 0.46, and [C—H] / [C—C] was 0.85. [Sp ² C—H] / [sp ² C—C] was 0.74, and [sp ³ C—H] / [sp ³ C—C] was 1.07. The coefficient of friction was 0.048. The arithmetic average surface roughness Ra on the surface of the obtained DLC film was 0.1 μm or less.

(Comparative Example 4)
A DLC film was formed in the same manner as in “Example 1” with a pulse frequency at the time of forming the DLC film of 300 kHz and a duty ratio of 15%, and the friction coefficient was measured. The absolute value of the average power density on the target side was 3.3 W / cm ² , and the absolute value of the maximum current density was 48.8 mAcm ⁻² . The absolute value of the average power density on the workpiece side was 24.8 mW / cm ² .

The hydrogen concentration of the obtained DLC film was 0.9 atomic%. [Sp ³ C—C] was 0.22, [sp ² C—C] was 0.37, [sp ³ C—H] was 0.16, and [sp ² C—H] was 0.25. . Therefore, [C-C] was 0.59, [C-H] was 0.41, and [C-H] / [C-C] was 0.69. [Sp ² C—H] / [sp ² C—C] was 0.68, and [sp ³ C—H] / [sp ³ C—C] was 0.73. The coefficient of friction was 0.045. The arithmetic average surface roughness Ra on the surface of the obtained DLC film was 0.1 μm or less.

<Comparative Example 5>
Instead of the sputtering method, a DLC film was formed on the end face of the disk by ionization vapor deposition using benzene (C ₆ H ₆ ) as a source gas, and the friction coefficient was measured. C ₆ H ₆ is ionized by performing discharge while continuously introducing C ₆ H ₆ at a rate of 30 ml / min at a gas pressure of 10 ⁻³ Torr, and ionized vapor deposition is performed for about 10 minutes. A 1 μm DLC film was formed on the surface of the substrate.

  When forming the DLC film, the workpiece side voltage is 1.5 kV, the workpiece side current is 50 mA, the filament voltage is 14 V, the filament current is 30 A, the anode voltage is 50 V, the anode current is 0.6 A, the reflector voltage is 50 V, and the reflector current. Was 6 mA.

The hydrogen concentration of the obtained DLC film was 19.3 atomic%. [Sp ³ C—C] was 0.05, [sp ² C—C] was 0.27, [sp ³ C—H] was 0.29, and [sp ² C—H] was 0.39. . Therefore, [C-C] was 0.32, [C-H] was 0.68, and [C-H] / [C-C] was 2.13. [Sp ² C—H] / [sp ² C—C] was 1.44, and [sp ³ C—H] / [sp ³ C—C] was 5.80. The coefficient of friction was 0.07. The arithmetic average surface roughness Ra on the surface of the obtained DLC film was 0.1 μm or less.

  Table 1 summarizes the results of the examples and comparative examples. As shown in Table 1, by forming a DLC film by sputtering, the hydrogen concentration can be made much smaller than when ionized vapor deposition using benzene gas as a raw material is used. [C−H] / [C−C] can also be greatly reduced, and the friction coefficient μ can be reduced.

  When a DC pulse power supply is used to form a DLC film by sputtering and the pulse frequency is increased, the power density on the target side is greatly increased, and the sputtered particles are effectively desorbed from the target. Is clear. Further, the absolute value of the average power density on the workpiece side is also greatly increased, and it is clear that sputtered particles having large energy have reached the workpiece. In addition, the higher the pulse frequency, the higher the absolute value of the maximum current density of the target, and the absolute values of the power density on the target side and workpiece side are increased, so that sputtered particles having larger energy can reach the workpiece. It shows that you can. Even if the pulse frequency is increased, the hydrogen concentration of the entire DLC film obtained by ERDA is not significantly changed, but indicates the amount of hydrogen bonded to carbon on the surface of the DLC film obtained by XPS [CH] / The value of [C-C] became small. By increasing the pulse frequency and decreasing [C−H] / [C−C], the friction coefficient μ can be greatly reduced.

In addition, when [C-H] is decreased by increasing the pulse frequency, [sp ² C-C] does not change greatly, whereas [sp ³ C-C] increases, It is considered that a DLC film having high hardness is formed.

  When the pulse frequency was the same, the higher the duty ratio, the larger the absolute value of the maximum current density on the target side, and the smaller the value of [C−H] / [C−C].

  The sliding member and the manufacturing method thereof according to the present invention can sufficiently reduce friction in the lubricating oil, and are useful as a sliding member used in an environment where the lubricating oil exists, a manufacturing method thereof, and the like.

201 Central magnet 202 Outer magnet 203 First external magnet 204 Second external magnet 205 Coil 207 Target 208 Work 210 Work holder 211 Target base 212 Matching circuit 213 High-frequency power source 214 Sputtering power source 214 Low-pass filter 215 Sputtering power source 216 Low-pass filter 218 Bias power source 221 Chamber

Claims (9)

A sliding surface that slides with the mating member in the presence of lubricating oil;
A carbonaceous film provided on the sliding surface,
The carbonaceous film has a surface on which a ratio of carbon-hydrogen bonds to carbon-carbon bonds is less than 0.59. The carbonaceous film has at its surface, sp ³ carbon - hydrogen bond of sp ³ carbon - sliding member according to claim 1, ratio carbon bonds and less than 0.57. The carbonaceous film has at its surface, sp ² carbon - hydrogen bond of sp ² carbon - sliding member according to claim 1 or 2 carbon ratio bonds and less than 0.58.   The sliding member according to any one of claims 1 to 3, wherein the carbonaceous film has a hydrogen content of 2 atom% or less.   5. The sliding member according to claim 1, wherein the carbonaceous film has an arithmetic average surface roughness Ra of 0.1 μm or less.   The said carbonaceous film is provided on the surface of the said member through the intermediate | middle layer, The sliding member of any one of Claims 1-5 characterized by the above-mentioned. Comprising a step of forming a carbonaceous film on the surface of the base material of the sliding member;
The step of forming the carbonaceous film includes
Performed by a sputtering method using graphite as a target and a sputtering power source as a direct current pulse power source,
The absolute value of the average output of the pulse power supply is 2.7 Wcm ⁻² or more, the pulse frequency of the pulse power supply is 250 kHz or more and 1 MHz or less,
The duty ratio of the pulse power source is greater than 15% and 90% or less,
A method for producing a sliding member, comprising forming a carbonaceous film having a ratio of carbon-hydrogen bonds to carbon-carbon bonds on the surface of less than 0.59. Comprising a step of forming a carbonaceous film on the surface of the base material of the sliding member;
The step of forming the carbonaceous film includes
Performed by a sputtering method using graphite as a target and a sputtering power source as a direct current pulse power source,
The absolute value of the maximum current density of the pulse power supply is set to be larger than 55.8 mAcm ⁻² , and the pulse frequency of the pulse power supply is set to 250 kHz or more and 1 MHz or less,
A method for producing a sliding member, comprising forming a carbonaceous film having a ratio of carbon-hydrogen bonds to carbon-carbon bonds on the surface of less than 0.59. The method for manufacturing a sliding member according to claim 7 or 8, wherein, in the step of forming the carbonaceous film, an absolute value of an average power density on the base material side is made larger than 19.7 mWcm ^-2. .

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