Hard carbon film and method for forming same

Abstract

To provide a hard carbon film capable of suppressing peeling from a base material even to a member rolled and slid in the presence of lubricant to maintain excellent slidability over a long term, and a method for depositing the same.SOLUTION: A hard carbon film covering at least a part of a region having a lubricant contacted on a base material has a plurality of holes having one or more corners and formed on a surface. A method for depositing the hard carbon film comprises: a hard carbon film formation step of forming the hard carbon film on the base material; and a hole formation step of forming the plurality of holes in the formed hard carbon film. The hard carbon film formation step is a composite process step of performing film deposition by a plasma CVD method using hydrocarbon as a raw material and film deposition by a sputtering method using solid carbon as a sputtering cathode in parallel in the same vacuum chamber; and the hole formation step is a step of forming the holes by polishing and removing carbon flakes generated from the sputtering cathode and fixed on the surface of the hard carbon film.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a hard carbon film and a method for forming the same. [Background technology]

[0002] Hard carbon (DLC: diamond-like carbon) films have excellent sliding properties, such as low friction, high wear resistance, and low cohesion (seizure resistance), and are therefore widely used as sliding components in machinery and equipment, molds, cutting tools, and automotive parts.

[0003] However, when such a hard carbon film is used in the presence of a lubricant, if the sliding portion becomes poorly lubricated, the sliding properties of the hard carbon film will decrease, causing the film to peel off from the substrate, and ultimately damaging the member due to fatigue fracture.

[0004] Furthermore, with the recent trend toward lower viscosity lubricants, such poor lubrication conditions occur in a short period of time.

[0005] For these reasons, various techniques have been proposed for hard carbon films that can delay the occurrence of poor lubrication conditions, thereby suppressing peeling of the hard carbon film from the substrate and maintaining sliding properties for a long period of time.

[0006] For example, Patent Document 1 proposes forming a lubricant reservoir in a hard carbon film, and making the angle between the side wall surface of the lubricant reservoir and the outer surface of the hard carbon film greater than 90 degrees. Patent Document 2 proposes forming densely packed granular irregularities. Patent Document 3 proposes forming recesses on the sliding surface and forming a coating made of an oleophilic substance so as to cover the inner surface of the recesses. Patent Document 4 proposes forming recesses in a hard carbon film by plasma etching or the like.

[0007] These techniques basically involve forming recesses that are not in direct contact with the sliding parts, and storing lubricant in these recesses, thereby delaying the depletion of the lubricant and preventing the occurrence of poor lubrication. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-172082 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-087197 [Patent Document 3] Japanese Patent Application Laid-Open No. 2012-197900 [Patent Document 4] Patent No. 4442349 Summary of the Invention [Problem to be solved by the invention]

[0009] However, although the above-mentioned techniques are effective to some extent for general sliding, they are still not sufficient, and in particular, for rolling and sliding components such as engine components, they are insufficient in maintaining sliding properties over a long period of time, and there is a strong demand for improvement.

[0010] Therefore, an object of the present invention is to provide a hard carbon film and a method for forming the same that can suppress peeling from a substrate and maintain excellent sliding properties for a long period of time even on members that roll and slide in the presence of a lubricant. [Means for solving the problem]

[0011] As a result of extensive research into solving the above problems, the present inventors have found that the above problems can be solved by the invention described below, and have completed the present invention.

[0012] The invention described in claim 1 is A hard carbon film that covers at least a part of a portion of a substrate that comes into contact with a lubricant, When viewed from the surface, a plurality of holes each having one or more corners are formed on the surface, and the maximum valley depth Rv of the holes is less than the film thickness. the law of nature, The length of the longest part of the hole is 10 to 200 μm The hard carbon film is characterized by:

[0013] The invention described in claim 2 is A hard carbon film that covers at least a part of a portion of a substrate that comes into contact with a lubricant, When viewed from the surface, a plurality of holes each having one or more corners are formed on the surface, and the oil reservoirs of the holes The depth Rvk is 0.03 to 0.35 μm, The length of the longest part of the hole is 10 to 200 μm A hard carbon film characterized by:

[0014] Claim 3 The invention described in The ratio of the pores to the membrane surface is 7 to 23%. Claim 1 or Claim 2 The hard carbon film is described in

[0015] Claim 4 The invention described in 1 to 3, characterized in that the arithmetic mean roughness Ra of the surface is 0.01 to 0.07 μm. 3 The hard carbon film according to any one of the above items.

[0016] Claim 5 The invention described in 10. The method according to claim 1, wherein the maximum valley depth Rv of the hole is 0.04 to 0.23 μm. 4 The hard carbon film according to any one of the above items.

[0018] Claim 6 The invention described in formed on an intermediate layer formed on the substrate, 10. The method according to claim 1, wherein the intermediate layer is a metal-containing hard carbon layer containing chromium or tungsten. 5 The hard carbon film according to any one of the above items.

[0019] Claim 7 The invention described in 10. The substrate according to claim 1, wherein the substrate is composed of a substrate body and a metal underlayer of chromium or tungsten formed on the substrate body. 6 The hard carbon film according to any one of the above items.

[0021] The invention described in claim 8 is 7. The method for forming a hard carbon film according to claim 6, an intermediate layer forming step of forming a metal-containing, hard carbon layer containing chromium or tungsten as an intermediate layer on the substrate; a hard carbon film forming step of forming a hard carbon film on the intermediate layer; a hole forming step of forming a plurality of holes in the formed hard carbon film, the intermediate layer forming step is a composite process step in which film formation by a plasma CVD method using a hydrocarbon as a raw material and film formation by a sputtering method using chromium or tungsten as a sputtering cathode are carried out in parallel in the same vacuum chamber; the hard carbon film forming step is a composite process step in which film formation by a plasma CVD method using hydrocarbon as a raw material and film formation by a sputtering method using solid carbon as a sputtering cathode are carried out in parallel in the same vacuum chamber; The hole forming step is the intermediate layer forming step and at least one of the hard carbon film forming steps and removing carbon flakes that are generated when the carbon coating attached to the surface of the sputtering cathode breaks down, thereby forming the holes.

[0022] Claim 9 The invention described in a base material forming step for forming a metal underlayer of chromium or tungsten on the base material body to form the base material; 8 2. A method for forming a hard carbon film according to claim 1.

[0023] Claim 10 The invention described in The surface of the substrate is cleaned by exposing it in advance to plasma of at least one gas selected from the group consisting of hydrogen gas, oxygen gas, and rare gas. Claim 8 or claims 9 2. A method for forming a hard carbon film according to claim 1. [Effects of the Invention]

[0024] According to the present invention, it is possible to provide a hard carbon film and a method for forming the same, which can suppress peeling from a substrate and maintain excellent sliding properties for a long period of time even on a member that rolls and slides in the presence of a lubricant. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a SEM image of the surface of a hard carbon film according to an embodiment of the present invention. [Figure 2] 1 is a cross-sectional view schematically showing the configuration of a hard carbon film according to an embodiment of the present invention. [Figure 3] FIG. 1 is a schematic diagram illustrating an example of a film forming apparatus. [Figure 4] FIG. 2 is a schematic diagram showing the generation of carbon flakes in a film formation process. [Figure 5] FIG. 1 is a conceptual diagram illustrating the mechanism of carbon flake generation. [Figure 6] This is an SEM image of the surface of a hard carbon film formed by arc evaporation. [Figure 7] This is an SEM image of the surface of a hard carbon film formed by plasma CVD. [Figure 8] 1A to 1C are diagrams illustrating the formation of a two-layer structure of a surface layer (DLC film) and an intermediate layer in an embodiment of the present invention. [Figure 9] FIG. 1 is a diagram showing the relationship between the flake presence rate and the film thickness of a DLC film. [Figure 10] These are microscope images of DLC films, and Figures (a) to (d) are images of DLC films with film thicknesses of 0.8 μm, 1.4 μm, 2.0 μm, and 3.8 μm, respectively. [Figure 11]FIG. 1 is a diagram showing the relationship between the arithmetic mean roughness Ra of a DLC film and the film thickness. [Figure 12] FIG. 1 is a diagram showing the relationship between the maximum valley depth Rv of a DLC film and the film thickness. [Figure 13] FIG. 10 is a diagram showing the relationship between the oil reservoir depth Rvk of the DLC film and the film thickness. [Figure 14] FIG. 1 is a schematic diagram illustrating an example of a thrust testing machine. [Figure 15] 10 is a microscope image showing test results of a thrust test. DETAILED DESCRIPTION OF THE INVENTION

[0026] [1] Hard carbon film according to the present invention 1. Overview of hard carbon films First, an outline of the hard carbon film (hereinafter also referred to as "DLC film") according to the present invention will be described. The hard carbon film according to the present invention is a hard carbon film that covers at least a part of the portion of a substrate that comes into contact with a lubricant, and From the surface, A plurality of holes with one or more corners are formed on the surface of the hard carbon film. and the maximum valley depth Rv of the hole is less than the film thickness. It is characterized by the following.

[0027] In the presence of a lubricant, the plurality of holes provided on the surface of the hard carbon film can each hold the lubricant and serve as oil pockets that supply the lubricant to the sliding surface, so that even when rolling and sliding members repeatedly come into contact with the surface in the presence of the lubricant, the lubricant is prevented from running out on the sliding surface. As a result, peeling from the substrate and deterioration in sliding properties and rolling wear resistance can be prevented for a long period of time, and excellent sliding properties can be maintained for a long period of time.

[0028] In the present invention, each hole has one or more corners, unlike the circular droplets that form during film formation using methods such as arc evaporation. Providing one or more corners in the holes makes it easier to retain the lubricant used in the parts compared to simple circular depressions, and therefore allows the film to maintain excellent sliding properties for a much longer period of time than conventional hard carbon films that only have circular depressions. Examples of lubricants include engine oil, low-viscosity oil, refrigeration base oil, and grease.

[0029] [2] Specific embodiments Hereinafter, the present invention will be specifically described based on embodiments with reference to the drawings.

[0030] 1.Hard carbon film (1) Surface condition First, the surface condition of the hard carbon film will be described. FIG. 1 is an SEM image of the surface of the DLC film according to this embodiment, taken from the surface of Sample A in the examples described below. As shown in FIG. 1, numerous fine pores are formed on the surface of the DLC film, and the pores are distributed almost uniformly across the surface of the DLC film. Furthermore, when the film is viewed from the surface, each pore is not circular but irregular in shape, with one or more corners.

[0031] The holes with corners have a better lubricant retention function than the conventional holes without corners, and because they are larger in size, they function better as oil pockets and can store a larger amount of lubricant.

[0032] (2) Composition The type and thickness of the DLC film are not particularly limited, and a known DLC film can be used with a known thickness.

[0033] Specifically, for example, a DLC film containing hydrogen (aC:H) with a hydrogen content of 5 to 25 at % and a thickness of several nm to several μm can be mentioned.

[0034] Furthermore, for example, in order to improve adhesion to the substrate (base material) and reduce the coefficient of friction, a two-layer structure may be used, consisting of a lower layer made of low-hydrogen or hydrogen-free DLC (aC) with a hydrogen content of, for example, less than 5 at %, and an upper layer made of the above-mentioned hydrogen-containing DLC ​​(aC:H).

[0035] 2. DLC film deposition method Next, a method for forming a DLC film will be described. Figure 2 is a cross-sectional view showing a schematic configuration of a DLC film according to this embodiment, where (a) shows the state before hole formation and (b) shows the state after hole formation. In Figure 2, 1 is a DLC film, 2 is a substrate, F is a carbon flake (hereinafter also simply referred to as "flake"), and H is a hole. In Figure 2, a base 3 is formed between the DLC film 1 and the substrate 2.

[0036] As shown in Figure 2(a), before holes are formed, flakes F are fixed to the DLC film 1 in a state where they are partially embedded in the DLC film 1, and the parts protruding from the surface are covered with an extremely thin DLC film 1. Because the adhesion of flakes F to the DLC film 1 is weak, flakes F can be easily detached from the DLC film 1 by simply applying a small external force to the protruding parts. Then, as shown in Figure 2(b), holes H of the same shape and size as flakes F are formed in the marks left by the detached flakes F.

[0037] The DLC film before hole formation shown in Figure 2(a) is formed by a combined process in which plasma CVD using hydrocarbon as a raw material and sputtering deposition using solid carbon as a sputtering cathode are performed in parallel in the same vacuum chamber.

[0038] Fig. 3 is a schematic diagram showing an example of a film formation apparatus. Fig. 4 is a schematic diagram showing the generation of carbon flakes in the DLC film formation process. Fig. 5 is a conceptual diagram explaining the mechanism of carbon flake generation. In Figs. 3 to 5, 4 is a film formation apparatus, 41 is a vacuum chamber, and 42 is a sputtering cathode. As mentioned above, 2 is a substrate.

[0039] 3, the film forming apparatus 4 includes a cylindrical vacuum chamber 41 rotatably supported at the center of the circular bottom surface, a sputtering cathode 42 fixed to the side wall surface of the vacuum chamber 41, a circular substrate support stand, and a bias power supply. The vacuum chamber 41 is equipped with an air inlet and an exhaust port.

[0040] During film formation, first, the gas inside the vacuum chamber 41 is evacuated, and then a mixed gas of Ar and a hydrocarbon such as methane or ethane is supplied to maintain a predetermined gas pressure inside the vacuum chamber 41. Next, a predetermined DC or pulsed bias voltage is applied to the sputter cathode 42 to generate Ar plasma inside the sputter cathode 42. This generated Ar plasma converts the hydrocarbon into plasma, generating hydrocarbon ions, and a DLC film is deposited as a layer on the surfaces of the substrate 2 and the sputter cathode 42.

[0041] 4 and 5, the surface of the sputtering cathode 42 is simultaneously sputtered by Ar plasma, causing the deposited DLC layer to crumble. The crumbled DLC turns into flakes F, which scatter around and adhere to the DLC film-formed surface of the opposing substrate 2, where they are fixed.

[0042] During film formation, multiple substrates 2 (on which a base is formed as necessary) are rotatably set up at equal intervals around the periphery of a substrate support table. During film formation, the vacuum chamber 41 and substrates 2 are rotated. This allows all substrates 2 to face the sputtering cathode 42 at equal intervals, at a fixed distance, for a fixed period of time. Furthermore, the entire side surface of the substrate 2 can face the sputtering cathode under the same conditions.

[0043] The flakes F that have adhered and fixed to the surface on which the DLC film is formed are then removed by polishing the surface of the DLC film using a technique such as lapping, and holes are formed in their traces.

[0044] 3. Comparison of shape with conventional DLC films As mentioned above, the DLC film of this embodiment is characterized by the fact that, when viewed from the surface, the individual pores are not circular but irregular, have one or more corners, and are large in size. To clarify this, a comparison was made with a conventional DLC film. Figures 6 and 7 show SEM images of the surface of a conventional DLC film. Figure 6 is an SEM image of a DLC film formed by arc evaporation, and Figure 7 is an SEM image of a DLC film formed by plasma CVD. These images were taken of the surfaces of Sample B and Sample C, respectively, in the examples described below.

[0045] As shown in Figure 6, the surface of the DLC film formed by arc evaporation has many pores, but they are round, without corners, and small in size. As shown in Figure 7, the surface of the DLC film formed by plasma CVD has very few pores, although they are not completely absent, and the pores are round, without corners, and small in size.

[0046] 4. Preferred Embodiments In this embodiment, the above-described DLC film and the method for forming the film preferably take the following forms.

[0047] (1) Preferred morphology of DLC film The DLC film preferably takes the following forms.

[0048] (a) Pore size The size of the holes H is preferably such that the length of the longest part is 10 to 200 μm, which allows the holes to function properly as lubricant reservoirs.

[0049] (b) Ratio of pores to membrane surface The ratio (area ratio) of the pores H to the film surface is preferably 7 to 23%. This allows the lubricant to be appropriately supplied from the pores as lubricant reservoirs. The ratio of the film surface occupied by the pores H can be calculated, for example, by the ratio of the number of pixels of the pores H to the total number of pixels in the image data of the film surface taken by a microscope.

[0050] (c) Surface roughness The arithmetic mean roughness Ra of the surface of the DLC film is preferably 0.01 to 0.07 μm. This allows the DLC film to exhibit appropriate sliding properties. Note that the "arithmetic mean roughness Ra" refers to the arithmetic mean roughness of the surface roughness measured by a method conforming to JIS B601:2013.

[0051] (d) Maximum valley depth of the hole The maximum valley depth Rv of the pores is preferably 0.04 to 0.23 μm. This allows the pores to function properly as lubricant reservoirs. Note that the "maximum valley depth Rv" refers to the maximum valley depth in the surface roughness measured by a method conforming to JIS B601:2013.

[0052] (e) Depth of oil reservoir in the hole The oil reservoir depth Rvk of the hole is preferably 0.03 to 0.35 μm. This allows the hole to function properly as a lubricant reservoir. The "oil reservoir depth Rvk of the hole" is defined as follows: JIS B671-2:2002 It refers to the protruding valley depth in the surface roughness measured by a method according to

[0053] (f) Membrane composition The DLC film is preferably formed on a metal underlayer containing chromium (Cr) or tungsten (W) as an adhesive layer on a substrate, and then on a metal-containing hard carbon layer containing chromium (Cr) or tungsten (W) formed as an intermediate layer, which improves the adhesion between the DLC film and the substrate.

[0054] (g) Base material In this embodiment, the substrate preferably comprises a substrate body and a metal underlayer of Cr or W formed on the substrate body. This allows the DLC film to adhere more closely to the substrate. The thickness of the metal underlayer is preferably about 0.2 to 0.7 μm, and the metal underlayer can be formed by, for example, sputtering deposition or arc deposition.

[0055] (2) Preferred form of DLC film formation method The method for forming the DLC film preferably takes the following forms.

[0056] (a) Formation of DLC film As mentioned above, the DLC film is preferably formed on a metal-containing, hard carbon layer containing chromium (Cr) or tungsten (W) that is formed as an intermediate layer on a substrate. Fig. 8 is a diagram illustrating the formation of this two-layer structure consisting of a surface layer (DLC film) and an intermediate layer. In Fig. 8, 11 denotes the surface layer, and 12 denotes the intermediate layer.

[0057] When forming the DLC film 1, flakes F are fixed to the DLC film 1 during film formation, and after film formation, the flakes 1 are detached from the DLC film to form holes H. At this time, it is preferable to form the DLC film 1 in the order of intermediate layer 12 and surface layer 11, each formed by the following methods.

[0058] First, the intermediate layer 12 is formed by a combined process in which film formation by plasma CVD using hydrocarbon as a raw material and film formation by sputtering using Cr or W as a sputtering cathode are carried out in parallel in the same vacuum chamber.

[0059] When Cr or W is used as the sputtering cathode, the frequency of flake generation increases dramatically, making it possible to deposit more flakes F, and as a result, the holes H can be distributed efficiently and at a desirable density.

[0060] Next, the surface layer 11 is formed by a combined process in which film formation by plasma CVD using hydrocarbon as a raw material and film formation by sputtering using solid carbon as a sputtering cathode are carried out in parallel in the same vacuum chamber.

[0061] The sputtering method, which uses graphite as a solid raw material, has the disadvantage of being a slow film formation method, but if hydrocarbon gas is flowed into the furnace, a hard carbon film can be formed using the same principle as the plasma CVD method, and the film formation speed is significantly improved compared to the sputtering deposition method, which does not use hydrocarbon gas.

[0062] Therefore, by forming a hard carbon film using a combined process that combines sputtering and plasma CVD, the film formation speed can be improved compared to when each method is used alone.

[0063] (b) Pore formation The holes H are preferably formed by polishing the formed DLC film 1, for example, by lapping. This allows the flakes F adhering to the surface to be efficiently removed. Specifically, brush lapping, film lapping, barrel polishing, etc. are used.

[0064] (c) Control of hole area ratio There is a correlation between the abundance of F flakes, i.e., the area ratio of F flakes to the film surface, and the thickness of the DLC film. Figure 9 shows the relationship between the abundance of F flakes, determined from microscope image data of the DLC film surface with thicknesses of 0.8 μm, 1.4 μm, 2.0 μm, and 3.8 μm, and the thickness of the DLC film. Figure 9 shows that there is a high correlation between the abundance of F flakes and the thickness of the DLC film.

[0065] As mentioned above, the pores H are the traces of the flakes F that have been removed, and the area ratio of the pores H can be adjusted to a desired value by controlling the film thickness. Figure 10 shows microscope images of the film surface after the formation of pores H in the DLC film, with (a) to (d) being images of DLC films with film thicknesses of 0.8 μm, 1.4 μm, 2.0 μm, and 3.8 μm, respectively. These image data show that the area ratio of the pores H can be adjusted by controlling the film thickness, and that by controlling the film thickness to 0.8 to 3.8 μm, the area ratio of the pores H can be adjusted to a desirable range of 7 to 23%.

[0066] (d) Control of film surface roughness In addition, the arithmetic mean roughness Ra and maximum valley depth of the DLC film Rv,There is a correlation between the oil reservoir depth Rvk and the film thickness of the DLC film. Figures 11 to 13 show the arithmetic mean roughness Ra and maximum valley depth for DLC films with film thicknesses of 0.8 μm, 1.4 μm, 2.0 μm, and 3.8 μm, respectively. Rv, These figures show the relationship between the oil reservoir depth Rvk and the film thickness. These figures show that the arithmetic mean roughness Ra and the maximum valley depth Rvk can be controlled by controlling the film thickness. Rv, It has been shown that it is possible to adjust the oil reservoir depth Rvk, and based on these correlations, the arithmetic mean roughness Ra, maximum valley depth Rv , the oil reservoir depth Rvk can be adjusted to a desired value.

[0067] (e) Pretreatment of the substrate Before forming the DLC film, it is preferable to clean the surface of the substrate by exposing it to plasma of at least one gas selected from the group consisting of hydrogen gas, oxygen gas, and rare gases. This removes impurities from the surface of the substrate, leaving it in a clean state and improving the adhesion between the DLC film and the substrate.

[0068] This method is advantageous in that it allows the substrate to be pretreated and then processed without being removed from the vacuum chamber, thereby reliably preventing contamination of the substrate surface. Furthermore, it is efficient because the pretreatment and the film formation can be carried out in a continuous process. [Example]

[0069] Next, the present invention will be described more specifically based on examples.

[0070] In this example, samples were prepared in which three types of DLC films were formed on a substrate, and the peel resistance of each film was evaluated.

[0071] [1] Sample preparation 1. Base material As shown in Table 1, a substrate made of carburized SCM415 (HRC60) with a diameter of 30 mm and a thickness of 3 mm was prepared.

[0072] 2. DLC film formation (1) Sample A Sample A is a sample in which a DLC film was formed on the above-mentioned substrate using a combination of sputter deposition and plasma CVD according to the present invention. Specifically, the film was formed under the following conditions, and a film thickness of 0.8 μm was formed on the substrate. Cleaning process: Ar 150 ccm, pressure 0.4 Pa Filament emission current 8A Substrate bias voltage 800V Metallic substrate (Cr) process: Ar 250 ccm, pressure 0.9 Pa Sputtering power output 5kW Substrate bias voltage 150V Cr-containing DLC ​​(intermediate layer) process: Ar500ccm, C2H210~200ccm Pressure 0.8~1.0Pa Sputter power output 3kW Substrate bias voltage 100 to 600V DLC process: Ar250ccm, C2H2100ccm Pressure 0.5Pa Sputter power output 4kW Substrate bias voltage 550V

[0073] (2) Sample B Sample B is a sample in which a DLC film was formed on the above substrate by arc evaporation. Specifically, the film was formed under the following conditions to a thickness of 1.0 μm on the substrate. Cleaning process: Ar 200 ccm, pressure 1.0 Pa Substrate bias voltage 1000V Metal substrate (Cr) process: Ar 10 ccm, pressure 0.1 Pa Arc current 45A Substrate bias voltage 400V DLC process: Ar 10 ccm, pressure 0.1 Pa Arc current 45A Substrate bias voltage 45V

[0074] (3) Sample C Sample C is a sample in which a DLC film was formed on the above substrate by plasma CVD. Specifically, the film was formed under the following conditions, and a film thickness of 3.0 μm was formed on the substrate. Cleaning process: Ar 50 ccm, pressure 0.2 Pa Discharge current 20A, electromagnetic coil current 5A Substrate bias voltage 500V Sputtering process: Ar 50 ccm, pressure 0.3 Pa Discharge current 20A, electromagnetic coil current 0A Substrate bias voltage 100V 40 hours Si-containing DLC ​​process: Ar50ccm, TMS100ccm, C2H2100ccm Pressure 0.1Pa Discharge current 20A, electromagnetic coil current 5A Substrate bias 500V DLC process: Ar 50 ccm, C2H2 100 ccm, pressure 0.1 Pa Discharge current 20A, electromagnetic coil current 5A Substrate bias 500V

[0075] [2] Evaluation of peel resistance Next, the adhesion of the DLC film on each sample was evaluated by a rolling test (thrust test) using a bearing.

[0076] 1. Test Method The test was carried out using the thrust testing machine shown in Figure 14. Specifically, a predetermined amount of lubricant was applied to the surface of the DLC film of each sample 54 on which the DLC film was formed, and then a steel ball 51 attached to a raceway 52 was pressed with a constant load, and the raceway 52 was caused to roll along the same track, repeatedly applying the load to the orbital portion of the steel ball 51 a predetermined number of times. Details of the test conditions are shown in Table 1.

[0077] [Table 1]

[0078] 2. Test Results (1) Surface condition during film formation As SEM images showing the surface state of each sample during film formation, Figure 1 shows the surface state of sample A, Figure 6 shows that of sample B, and Figure 7 shows that of sample C.

[0079] Figure 1 shows that when arc evaporation and plasma CVD are used together, holes with one or more corners are formed. Figure 6 shows that when arc evaporation is used, small granular (spherical) depressions without corners are formed. Figure 7 shows that when plasma CVD is used, even smaller granular (spherical) depressions are formed than those in Figure 6.

[0080] (2) Thrust test results The results of the thrust test are shown in Figure 15. Figure 15 shows SEM images of the surface of the raceway of each sample after the thrust test.

[0081] As can be seen from Figure 15, in the case of Sample A, which is an example of the present invention, no peeling of the DLC film occurred in both the 225,000-cycle fatigue test and the 1.26 million-cycle fatigue test. Such excellent fatigue resistance was achieved because the lubricating function of the lubricant was maintained during the fatigue test, keeping friction due to rolling contact low, which in turn suppressed the stress generated between DLC films and at the interface between the DLC film and the substrate.

[0082] On the other hand, in the case of sample B, no peeling occurred in the 225,000-cycle fatigue test, but peeling occurred around the entire circumference of the DLC film on the raceway in the 1.26 million-cycle fatigue test.

[0083] In the case of sample C, the DLC film had already peeled off in part of the raceway after a 225,000-cycle fatigue test, and peeled off around the entire circumference of the DLC film in the raceway after a 1.26 million-cycle fatigue test.

[0084] As a result of the above, it was confirmed that a film with excellent performance can be obtained by forming a DLC film with one or more corners in the pores using a combination of arc evaporation and plasma CVD according to the present invention.

[0085] Although the present invention has been described above based on the embodiments, the present invention is not limited to the above-described embodiments. Various modifications can be made to the above-described embodiments within the scope of the same or equivalent to the present invention. [Explanation of symbols]

[0086] 1 DLC film 2 Base material 3. Base 4 Film deposition equipment 11 Surface layer 12 Middle Class 41 Vacuum Chamber 42 Sputtering cathode 51 steel ball 52 Raceway ring 53 Oil 54 samples F Carbon flakes (flakes) H hole

Claims

1. A hard carbon film that covers at least a part of a portion of a substrate that comes into contact with a lubricant, a plurality of holes each having one or more corners are formed on the surface as viewed from the surface, and a maximum valley depth Rv of the holes is less than the film thickness; A hard carbon film characterized in that the length of the longest part of the pores is 10 to 200 μm.

2. A hard carbon film that covers at least a part of a portion of a substrate that comes into contact with a lubricant, A plurality of holes having one or more corners are formed on the surface when viewed from the surface, and the oil reservoir depth Rvk of the holes is 0.03 to 0.35 μm; A hard carbon film characterized in that the length of the longest part of the pores is 10 to 200 μm.

3. 3. The hard carbon film according to claim 1, wherein the pores account for 7 to 23% of the film surface.

4. 4. The hard carbon film according to claim 1, wherein the arithmetic mean roughness Ra of the surface is 0.01 to 0.07 μm.

5. 5. The hard carbon film according to claim 1, wherein the maximum valley depth Rv of the pores is 0.04 to 0.23 μm.

6. formed on an intermediate layer formed on the substrate, 6. The hard carbon film according to claim 1, wherein the intermediate layer is a metal-containing, hard carbon layer containing chromium or tungsten.

7. 7. The hard carbon film according to claim 1, wherein the substrate is composed of a substrate main body and a metal underlayer of chromium or tungsten formed on the substrate main body.

8. 7. The method for forming a hard carbon film according to claim 6, an intermediate layer forming step of forming a metal-containing, hard carbon layer containing chromium or tungsten as an intermediate layer on the substrate; a hard carbon film forming step of forming a hard carbon film on the intermediate layer; a hole forming step of forming a plurality of holes in the formed hard carbon film, the intermediate layer forming step is a composite process step in which film formation by a plasma CVD method using a hydrocarbon as a raw material and film formation by a sputtering method using chromium or tungsten as a sputtering cathode are carried out in parallel in the same vacuum chamber; the hard carbon film forming step is a composite process step in which film formation by a plasma CVD method using hydrocarbon as a raw material and film formation by a sputtering method using solid carbon as a sputtering cathode are carried out in parallel in the same vacuum chamber; a step of forming the holes by removing carbon flakes generated by the breakdown of the carbon coating adhered to the surface of the sputtering cathode in at least one of the intermediate layer forming step and the hard carbon film forming step.

9. 9. The method for forming a hard carbon film according to claim 8, further comprising a substrate forming step of forming a metal underlayer of chromium or tungsten on the substrate body to form the substrate.

10. 10. The method for forming a hard carbon film according to claim 8, wherein the surface of the substrate is cleaned in advance by exposing it to plasma of at least one gas selected from the group consisting of hydrogen gas, oxygen gas, and rare gases.

Images