Machine component and method for manufacturing machine component

Abstract

To improve lubricating property under a self-lubricating condition.SOLUTION: A machine component according to the present disclosure comprises a substrate and a thin film layer provided above the substrate, the thin film layer being formed of a carbon film composed of a network of amorphous carbon atoms. The thin film layer is impregnated with a lubricating liquid.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a machine component and a method for manufacturing a machine component. [Background technology]

[0002] In order to improve the lubrication properties of machine parts, development of solid lubricating films such as hydrocarbon films such as diamond-like carbon (DLC) is underway. For example, Patent Document 1 below discloses technology related to DLC films that are suitable for lubrication with lubricating oil. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-89644 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, self-lubricating bearings and other sliding components (one example of a machine component) have come into widespread use from the perspectives of sustainability and environmental adaptability. However, achieving the required high level of lubrication is difficult using only solid lubricant films.

[0005] Therefore, the present invention has been made in consideration of the above problems, and an object of the present invention is to provide a machine component and a method for manufacturing a machine component that can further improve lubrication characteristics in self-lubrication. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, according to one aspect of the present invention, there is provided a machine component comprising: a substrate; and a thin film layer formed on the substrate by a hydrocarbon film constituted by an amorphous network of carbon atoms, the thin film layer being impregnated with a lubricating liquid.

[0007] In order to solve the above-mentioned problems, according to another aspect of the present invention, there is provided a method for manufacturing a machine component, the method including the steps of forming a thin film layer containing a hydrocarbon film composed of an amorphous network of carbon atoms above a substrate, and impregnating the thin film layer with a lubricating liquid. [Effects of the Invention]

[0008] As described above, according to the present invention, it is possible to further improve the lubrication characteristics in self-lubrication. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram showing an example of the configuration of a sliding member 1 according to the present embodiment. [Figure 2] 3 is a schematic diagram showing an example of a lubrication mechanism when the sliding member 1 according to the embodiment is used. FIG. [Figure 3] FIG. 1 is a diagram showing an example of evaluation of a DLC film by Raman spectroscopy. [Figure 4] 10 is an example of parameters indicating the structural characteristics of the DLC film 3 according to the present embodiment. [Figure 5] 10 is an example of parameters indicating the structural characteristics of the DLC film 3 according to the same example. [Figure 6] 10 is an example of parameters indicating the structural characteristics of the DLC film 3 according to the same example. [Figure 7] 10 is a graph showing the change in the coefficient of friction of a DLC film without fluorine addition when the film is formed using a negative pressure pulse of −10 kV according to the same example. [Figure 8]10 is an optical microscope image showing the wear marks of a test piece and an iron ball after a friction test of a DLC film without fluorine addition when formed using a negative pressure pulse of −10 kV according to the same example. [Figure 9] 10 is a graph showing the change in the coefficient of friction of a DLC film without fluorine addition when the film is formed using a negative pressure pulse of −1.5 kV according to the same example. [Figure 10] 10 is an optical microscope image showing the wear marks of a test piece and an iron ball after a friction test of a DLC film without fluorine addition formed using a negative pressure pulse of −1.5 kV according to the same example. [Figure 11] 10 is a graph showing the change in the product coefficient of the fluorine-added DLC film when the film is formed using each negative pressure pulse according to the same example. [Figure 12] 10 is an optical microscope image showing the wear marks of a test piece and an iron ball after a friction test of a fluorine-added DLC film formed using a negative pressure pulse of −3 kV according to the same example. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant explanations will be omitted.

[0011] One embodiment of the present invention relates to a technology for a sliding member in which opposing structures, such as bearings, piston rings, and cylinders, come into contact with each other and friction occurs. Such a sliding member (an example of a machine member) can be formed by impregnating a lubricant into the interior of a DLC film formed on a substrate. That is, the sliding member according to this embodiment is a so-called self-lubricating type, and more specifically, the DLC film is impregnated with oil.

[0012] Fig. 1 is a diagram showing an example of the configuration of a sliding member 1 according to this embodiment. Note that Fig. 1 merely shows a part of the surface of the sliding member 1. For the sake of explanation, the surface of the sliding member 1 shown in Fig. 1 is flat, but it may be curved, for example, like a bearing, a piston ring, or a ball.

[0013] As shown in FIG. 1, a sliding member 1 according to this embodiment includes a substrate 2, a DLC film 3, and a lubricating liquid 4 impregnated in the DLC film 3.

[0014] The substrate 2 is a component of the sliding member 1 and has a sliding surface that can slide against other structures. The substrate 2 is made of any material. Such a material may be, for example, any metal or alloy material such as steel, copper, brass, or aluminum, or may be a ceramic material or resin. The sliding surface of the substrate 2 (i.e., the interface with the DLC film 3) may be subjected to any surface treatment to improve the adhesion of the DLC film 3 or to increase the retention of the lubricating liquid 4 impregnated therein, as described below, or may be provided with an auxiliary film (e.g., a metal film of Ti, Cr, etc.) to improve adhesion to the DLC film 3.

[0015] The DLC film 3 is an example of a carbon film composed of a network of amorphous carbon atoms. The DLC film 3 is composed of a network of sp2- or sp3-bonded carbon atoms, and some of the carbon atoms are terminated with hydrogen, fluorine, or the like. In this technology, the carbon film may be, for example, a hydrocarbon film, a fluorine-doped DLC (F-DLC), or a hydrogen-free film. A hydrogen-free film is an amorphous film composed only of carbon.

[0016] It is known that the properties of the DLC film 3 vary significantly depending on the configuration of the carbon atom network. These properties can be estimated from parameters obtained by analysis using, for example, Raman spectroscopy. These will be described later.

[0017] The lubricating liquid 4 is a lubricating liquid used as a liquid lubricant. The lubricating liquid 4 is not particularly limited, but may be, for example, a lubricating oil. The type of lubricating oil is not particularly limited, but synthetic lubricating oil, mineral oil, water, silicone oil, etc. are preferred.

[0018] FIG. 2 is a schematic diagram illustrating an example of a lubrication mechanism when the sliding member 1 according to this embodiment is used. As shown in FIG. 2, in the sliding member 1 according to this embodiment, a lubricating liquid 4 is impregnated into the DLC film 3. When another structure 5 (schematically represented as a pin) contacts and slides against the sliding member 1, the pressure from the other structure 5 against the sliding member 1 causes the lubricating liquid 4 impregnated in the DLC film 3 to seep out toward the surface of the sliding surface 7. As the lubricating liquid 4 continues to seep out toward the sliding surface 7, a liquid film 6 can be formed on the sliding surface 7. As a result, the interface between the sliding surface 7 and the other structure 5 can transition from a solid lubrication or boundary lubrication state to an elastohydrodynamic lubrication (EHL) state. This allows a superlubrication state to be achieved at the interface.

[0019] Generally, DLC films 3 are composed of a network of carbon atoms with a mixture of sp2 hybrid orbitals (graphite-like bonds) and sp3 hybrid orbitals (diamond-like bonds), and therefore, due to the size of the polymer molecules in the lubricating oil, it is difficult for a lubricating liquid 4 such as a lubricating oil to penetrate into the DLC film 3. For this reason, while DLC films 3 have often been used in combination with lubricating oils in the past, it has been difficult to impregnate the DLC film 3 with lubricating oils or the like.

[0020] As a result of intensive research by the present inventors, they have succeeded in developing an impregnated DLC film that has a specific structural state, which is easily impregnated with a lubricant or the like and exhibits the above-mentioned superlubricity as a self-lubricating film. The structure of the DLC film 3 of the sliding member 1 according to this embodiment will be described in detail below.

[0021] In this embodiment, Raman spectroscopy was used as a method for evaluating the structural characteristics of the DLC film 3. FIG. 3 shows an example of evaluation of a DLC film by Raman spectroscopy. In this embodiment, the DLC film 3 was irradiated with light having a wavelength of 532 nm, and the baseline was subtracted from the Raman spectrum obtained by this irradiation, and two peaks (D peak: 1365 cm) were obtained. -1 Peak centered around the G peak: 1540 cm -1 The DLC film 3 was separated into peaks centered around the center of the DLC film 3 (although the position of the peak varies depending on the structure of the DLC film 3), and the characteristics of the DLC film 3 were summarized using parameters obtained for these peaks.

[0022] Here, ID is the intensity of the D peak, and IG is the intensity of the G peak. The ratio of ID to IG (ID / IG) correlates with the proportion of carbon atoms with sp2 hybrid orbitals in the DLC film 3. Pos(G) is the position of the peak of the G peak and is an index of the graphitization of the DLC film 3. Furthermore, FWHM(G) is the width of the peak at half maximum of the G peak and is an index of the amorphous state of the DLC film 3.

[0023] The hardness of the DLC film 3 was measured by nanoindentation. The nanoindentation device used was the ENT-NEXUS manufactured by Elionix. A Berkovich-type diamond indenter was used, and the indentation load was 1 mN.

[0024] The density of the DLC film 3 was also obtained by X-ray reflectivity. For the X-ray reflectivity, a SmartLab manufactured by Rigaku Corporation was used. The characteristic X-rays used were copper Kα1 (wavelength: 0.1542 nm), and the reflectivity according to the angle of incidence of the characteristic X-rays was obtained at scan angles between 0° and 4°.

[0025] The impregnation of the DLC film 3 with the lubricating liquid 4 is carried out as follows. First, the substrate 2 on which the DLC film 3 has been formed is placed on a spin coater, and the lubricating liquid 4 is dropped onto the surface of the DLC film 3. The spin coater is then used to spread the lubricating liquid 4 over the entire DLC film 3. After the application of the lubricating liquid 4 by the spin coater is complete, the DLC film 3 is left to stand, and the lubricating liquid 4 is allowed to penetrate into the DLC film 3. If any lubricating liquid 4 remains on the surface of the DLC film 3 after a sufficient amount of time has passed, this lubricating liquid 4 is removed.

[0026] When the DLC film 3 did not contain fluorine, the hydrogen content in the DLC film 3 was measured using elastic recoil detection analysis.

[0027] Furthermore, when the DLC film 3 contains fluorine, the fluorine content in the DLC film 3 is measured by X-ray photoelectron spectroscopy. For X-ray photoelectron spectroscopy, a PHI5000 manufactured by ULVAC-PHI was used. The characteristic X-rays used were aluminum Kα (photon energy: 1486.6 eV), and a spectrum was obtained by integrating 10 repeated measurements. Background correction of the obtained spectrum was performed using the Shirley method. To calculate the fluorine content, the spectral area was corrected using the relative sensitivity coefficient of each atom.

[0028] The DLC film 3 according to this embodiment is formed by the PBII&D (Plasma-Based Ion Implantation & Deposition) method. The PBII method involves placing a substrate in a vacuum chamber, drawing a vacuum, and then repeatedly applying alternating positive and negative pulse voltages to the substrate while introducing raw materials (e.g., toluene, methane, acetylene, benzene, etc.). This generates plasma from the raw materials around the substrate, and then introduces ions in the plasma into the substrate, thereby forming a film. While the PBII method is one example of a manufacturing method, the manufacturing method is not particularly limited as long as it is capable of producing a DLC film having the structural characteristics described below.

[0029] The DLC film 3 according to this embodiment can be roughly divided into ordinary DLC and fluorine-added DLC. First, the structural characteristics of ordinary DLC (that is, DLC that does not contain fluorine) will be described.

[0030] For the DLC according to this embodiment, ID / IG is preferably 0.75 or more, and more preferably 0.9 or more. This allows the DLC film 3 to have a sufficiently graphitized structure, making it easier for the lubricating liquid 4 to penetrate, and increasing the effect of the lubricating liquid 4 seeping out to the contact interface of the DLC film 3 during sliding. There is no particular upper limit to ID / IG, but in practice the upper limit may be around 1.2.

[0031] For the DLC according to this embodiment, the position of the G peak is 1550 cm -1 This allows the DLC film 3 to have a sufficiently graphitized structure, which facilitates impregnation with the lubricating liquid 4 and increases the effect of the lubricating liquid 4 seeping out to the contact interface of the DLC film 3 during sliding. There is no particular upper limit to the position of the G peak, but in practice, it is set to 1620 cm -1 can be an upper limit.

[0032] In addition, for the DLC according to this embodiment, the G peak position is 1545 cm -1 If it is more than 170cm, FWHM(G) is 170cm -1 It can be the following:

[0033] The hardness of the DLC according to this embodiment can be about 5 GPa to 20 GPa. The density of the DLC according to this embodiment can be 1.4 g / cm. 3 to 1.8 g / cm 3 The time required for the lubricating liquid 4 to be impregnated tends to be shorter as graphitization progresses. The estimated hydrogen content of the DLC according to this embodiment may be between 15 at.% and 50 at.%.

[0034] Next, the structural characteristics of fluorine-doped DLC will be explained.

[0035] For the fluorine-doped DLC according to this embodiment, ID / IG is preferably 0.5 or more, and more preferably 0.9 or more. This allows the DLC film 3 to have a sufficiently graphitized structure, making it easier for the lubricant 4 to penetrate, and increasing the effect of the lubricant 4 seeping out to the contact interface of the DLC film 3 during sliding. There is no particular upper limit to ID / IG, but in practice the upper limit may be around 1.2.

[0036] For the fluorine-doped DLC according to this embodiment, the position of the G peak is 1550 cm -1 This allows the DLC film 3 to have a sufficiently graphitized structure, which facilitates impregnation with the lubricating liquid 4 and increases the effect of the lubricating liquid 4 seeping out to the contact interface of the DLC film 3 during sliding. There is no particular upper limit to the position of the G peak, but in practice, it is set to 1620 cm -1 can be an upper limit.

[0037] In addition, for the DLC according to this embodiment, the G peak position is 1550 cm -1 If it is more than 160cm, FWHM(G) is 160cm -1 It can be the following:

[0038] The hardness of the DLC according to this embodiment can be about 3 GPa to 5 GPa. The density of the DLC according to this embodiment can be 1.2 g / cm. 3 to 1.6 g / cm 3 The time required for the lubricating liquid 4 to be impregnated tends to be shorter as graphitization progresses. The fluorine content of the fluorine-added DLC according to this embodiment may be between 15 at.% and 27 at.%. [Example]

[0039] Next, an example of a friction test of the sliding member 1 will be described.

[0040] In this example, test specimens were first prepared by impregnating each of the DLC films 3 formed on the substrate 2 using the PBII&D method with a lubricating liquid 4. Next, a friction test was performed on each test specimen under the same conditions, and the friction coefficient and wear marks after the friction test were evaluated.

[0041] First, we will explain how to prepare the test specimen. For the PBII&D method, we used KJ08-3696 manufactured by Kurita Manufacturing Co., Ltd. The base pressure was 10 -4 The pressure during film formation was 0.4 Pa. The frequency of the applied pulse was 4 kHz, and the duty ratio (ratio of the pulse width in one cycle) was 2%.

[0042] A silicon wafer was used as the substrate. Substrate 2 was fixed to a stage, and after evacuation, pre-sputtering was performed using a mixed gas of argon and hydrogen to clean the surface. The positive pressure pulse voltage was 1.5 kV and the negative pressure pulse voltage was -5.0 kV, and the process was carried out for 30 minutes.

[0043] After pre-sputtering, film formation was carried out for DLC without fluorine addition and DLC with fluorine addition under the following conditions. Positive pressure pulse: 1.5kV Negative pressure pulse: No fluoride added: -1.5kV, -5kV, -10kV Fluorine added: -1kV, -1.5kV, -3kV, -5kV, -7kV, -10kV Raw materials: No fluorine added: Toluene (C7F8) Fluorine added: hexafluorobenzene (C6F6)

[0044] Raman spectrum data was obtained for each of the coated test pieces using Raman spectroscopy. Renishaw's inVia was used for Raman spectroscopy. The wavelength of the light source used was 532 nm, and the spectrum was acquired five times and integrated, which was used as the Raman spectrum data. Peak separation was performed on these spectra using a Gaussian function, and the various parameters mentioned above were obtained.

[0045] A lubricant was then applied to the coated test specimen using a spin coater, allowing the DLC film to be impregnated. An ester-based synthetic lubricant was used as the lubricant. After impregnation, a friction test was performed using a pin-on-disk tribometer (Type: 20, manufactured by Shinto Scientific Co., Ltd.). A φ10 SUJ2 steel ball was used as the counterpart structure. The friction test was performed in the atmosphere. The room temperature during the test was approximately 25°C, and the maximum humidity was 25%. The load was 1 N, and the rotation radius was 1 mm. The Hertzian contact pressure in this case was 383.1 MPa. The rotation speed was 200 RPM (approximately 20.9 mm / s), and 20,000 cycles were performed. After 20,000 cycles, the surfaces of the steel ball and test specimen were observed using an optical microscope.

[0046] 4 to 6 are lists of parameters showing the structural characteristics of the DLC film for each film formation condition.

[0047] Figures 7 and 8 are graphs showing the change in the friction coefficient of a non-fluorinated DLC film formed using a negative pressure pulse of -10 kV, as well as optical microscope images showing the wear scars on the test piece and iron ball after the friction test. Figures 9 and 10 are graphs showing the change in the friction coefficient of a non-fluorinated DLC film formed using a negative pressure pulse of -1.5 kV, as well as optical microscope images showing the wear scars on the test piece and iron ball after the friction test. As shown in these figures, when DLC formed at -10 kV (i.e., highly graphitized DLC) was impregnated with an ester-based synthetic lubricant, the friction coefficient was 0.018 after 20,000 cycles, demonstrating a fairly low level. Furthermore, only slight scratches were observed in the wear scar of the iron ball, suggesting little solid-state contact. A liquid film was also visible on the wear scar of the test piece immediately after the test. Furthermore, as time passed after the test, the liquid film of lubricating oil that had formed on the surface disappeared, and it was observed that it was again impregnated into the DLC film. On the other hand, the DLC film formed at -1.5kV (i.e., DLC with advanced polymerization) showed a very high coefficient of friction, and a large amount of wear debris was observed on the iron ball, suggesting that solid contact occurred, accelerating wear.

[0048] Figures 11 and 12 show graphs showing the change in the product coefficient of the fluorinated DLC film deposited with each negative pressure pulse, as well as optical microscope images of the wear scars on the test specimen and iron ball after friction tests on the fluorinated DLC film deposited with a -3 kV negative pressure pulse. Both DLC films demonstrate superlubricity of approximately 0.01 after 20,000 cycles. Furthermore, as shown in Figure 12, no scratches or wear debris were observed in the wear scars on the test specimens. Furthermore, immediately after the test, a liquid film formed on the wear scars of the test specimens was visually observed. Furthermore, as time passed after the test, the liquid film formed by the lubricating oil on the surface disappeared and was again impregnated into the DLC film.

[0049] In this embodiment, an example in which the lubricating liquid 4 is impregnated into the DLC film 3 has been described, but the present disclosure is not limited to such an example. For example, the slide member 1 including the DLC film 3 may be used for lubrication in oil. In this case, the lubricating liquid 4 may also be impregnated into the DLC film 3.

[0050] Finally, while various embodiments of the present disclosure have been described, they are presented as examples and are not intended to limit the scope of the invention. The novel embodiments may be embodied in various other forms, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. Such embodiments and modifications are intended to be included within the scope and spirit of the invention, as well as within the scope of the inventions and their equivalents as defined in the claims.

[0051] The following embodiments are also included in the scope of the present invention. (Item 1) A machine component, A substrate; a thin film layer provided above the substrate and formed of a carbon film composed of an amorphous carbon atom network; The thin film layer is impregnated with a lubricating liquid therein. (Item 2) The machine member according to item 1, At least a part of the carbon atoms constituting the carbon film is bonded to fluorine. Machine parts. (Item 3) The machine member according to item 2, ID / IG, which is a ratio of a D peak intensity to a G peak intensity as determined by a spectrum of the carbon film based on Raman spectroscopy, is 0.5 or more and 1.2 or less. Machine parts. (Item 4) The machine member according to item 2, The position of the G peak identified by the spectrum based on Raman spectroscopy of the carbon film is 1550 cm -1 That's all. Machine parts. (Item 5) The machine member according to item 1, I / I, which is a ratio of a D peak intensity to a G peak intensity as determined by a spectrum based on Raman spectroscopy of the carbon film, is 0.75 or more; The position of the G peak identified by the spectrum based on Raman spectroscopy of the carbon film is 1550 cm -1 That's all. Machine parts. (Item 6) A method for manufacturing a machine component, comprising: forming a thin film layer including a carbon film composed of an amorphous carbon atom network above a substrate; impregnating the thin film layer with a lubricating liquid; A method for manufacturing a machine member, comprising: [Explanation of symbols]

[0052] 1. Sliding parts (machine parts) 2 Base material 3 DLC film 4. Lubricant

Claims

1. A machine component, A substrate; a thin film layer provided above the substrate and formed of a carbon film composed of an amorphous carbon atom network; The thin film layer is impregnated with a lubricating liquid therein.

2. The machine component according to claim 1, At least a part of the carbon atoms constituting the carbon film is bonded to fluorine. Machine parts.

3. The machine member according to claim 2, I / I, which is a ratio of a D peak intensity to a G peak intensity as determined by a spectrum of the carbon film based on Raman spectroscopy, is 0.5 or more and 1.2 or less. Machine parts.

4. The machine member according to claim 2, The position of the G peak identified by the spectrum based on Raman spectroscopy of the carbon film is 1550 cm －１ That's all. Machine parts.

5. The machine component according to claim 1, I / I, which is a ratio of a D peak intensity to a G peak intensity as determined by a spectrum of the carbon film based on Raman spectroscopy, is 0.75 or more; The position of the G peak identified by the spectrum based on Raman spectroscopy of the carbon film is 1550 cm －１ That's all. Machine parts.

6. A method for manufacturing a machine component, comprising: forming a thin film layer including a carbon film composed of an amorphous carbon atom network above a substrate; impregnating the thin film layer with a lubricating liquid; A method for manufacturing a machine member, comprising:

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