Sliding part

Abstract

The present invention provides a sliding member capable of obtaining a stable low-friction effect under a wide range of use conditions. A sliding member (20) has a sliding surface (21) that slides relative to each other. Among them, a graphite film (30) is covered on a base material (22) of the sliding member (20), and the sliding surface (21) is constituted by the graphite film (30).

Description

Technical Field

[0001] The present invention relates to a sliding member that relatively slides, for example, a sliding member used in a shaft seal device that seals a rotating shaft of a rotating machine in the fields of automobiles, general industrial machinery, or other sealing fields, or a sliding member used in a bearing of a machine in the fields of automobiles, general industrial machinery, or other bearing fields. Background Art

[0002] A sliding member has a sliding surface that relatively slides with a sliding surface on the other side, and is used as a bearing that supports a rotating or reciprocating shaft, etc., or a component of a shaft seal device that prevents leakage of a fluid to be sealed. As a shaft seal device that prevents leakage of a fluid to be sealed, for example, a mechanical seal includes a pair of annular seal members that relatively rotate and whose sliding surfaces slide against each other. For example, the sliding member shown in Patent Document 1 is formed of a soft material, carbon, so as to obtain a low friction effect by the self-lubricity of carbon. However, when foreign matter intrudes between the sliding surfaces, the sliding surface of the sliding member formed of carbon is easily scratched, and there is a problem in foreign matter resistance.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2011-58517 (page 6, Figure 1 )

[0006] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2004-225725 (page 6, Figure 2 ) Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] By forming a sliding member from a hard material, SiC (for example, Patent Document 2), foreign matter resistance can be improved. However, for example, when a mechanical seal is used in a non-lubricated environment (dry environment) where there is no liquid between the sliding surfaces, since the friction coefficient of SiC in the atmosphere is large, adhesion may occur on the sliding surface depending on the usage conditions. In addition, in Patent Document 2, the sliding surface of the sliding member is covered with a diamond-like carbon coating (hereinafter, sometimes also referred to as a DLC coating). For example, when used in a non-lubricated environment, since the DLC coating has a high hardness, adhesion may occur on the sliding surface on the other side depending on the usage conditions. In order to obtain a low friction effect, complex condition settings such as changing the hydrogen content of the DLC coating are required depending on the usage conditions, and there is a lack of generality.

[0009] The present invention has been made in view of such problems, and an object thereof is to provide a sliding member that can obtain a stable low friction effect under a wide range of usage conditions.

[0010] Means for Solving the Problem

[0011] In order to solve the above problems, the sliding member of the present invention,

[0012] which has sliding surfaces that slide relative to each other, wherein,

[0013] a graphite film is covered on the base material of the sliding member, and the sliding surface is constituted by the graphite film.

[0014] Accordingly, the base material of the sliding member is covered with a graphite film. Thus, the graphite film constituting the sliding surface is sheared between the graphite layers bonded by van der Waals forces due to friction with the sliding surface on the opposite side, and a part of the graphite film remains in the fine recesses on the surface of the base material, so that the sliding surface is smoothed, and the self-lubricity of graphite can be exerted on the sliding surface on the opposite side. Therefore, a low friction effect can be stably obtained under a wide range of use conditions such as in the fluid lubrication region, the boundary lubrication region, and the non-lubricated environment.

[0015] Alternatively, the hardness of the graphite film is less than the hardness of the sliding surface on the opposite side.

[0016] Accordingly, the graphite film is softer than the sliding surface on the opposite side, so it is not easily damaged due to friction with the sliding surface on the opposite side.

[0017] Alternatively, the hardness of the graphite film is less than the hardness of the base material.

[0018] Accordingly, the base material covered with the graphite film is harder than the graphite film. Thus, when foreign matter intrudes between the sliding surfaces, the soft graphite film is preferentially scratched, thereby promoting the smoothing of the sliding surface, and the foreign matter resistance can be improved by the exposed surface of the base material. Therefore, the self-lubricity of graphite and the foreign matter resistance can be achieved simultaneously between the sliding surfaces.

[0019] Alternatively, the thickness of the graphite film is greater than the arithmetic mean roughness Ra of the surface of the base material.

[0020] Accordingly, the thickness of the graphite film is greater than the unevenness of the surface of the base material. Therefore, a part of the graphite film easily enters the fine recesses of the base material, and the low friction effect is easily exerted.

[0021] Alternatively, the base material is formed of ceramics.

[0022] Accordingly, porous ceramics are more likely to generate surface roughness than metals, so the graphite film is easily fixed on the base material.

[0023] Alternatively, the arithmetic mean roughness Ra of the surface of the base material is 0.1 μm or more.

[0024] Accordingly, the graphite film easily enters the fine recesses on the surface of the base material. Therefore, even if the graphite film is sheared by friction with the sliding surface on the opposite side, a part of the graphite film will be retained in the fine recesses and is not easily detached.

[0025] Alternatively, the entire surface of the base material may be covered with the graphite film.

[0026] Accordingly, a state is formed in which a part of the base material side of the graphite film enters all the fine recesses on the surface of the base material. Therefore, when the graphite film is sheared, the sliding surface is easily smoothed.

[0027] Alternatively, the graphite film may be formed only on one of the sliding surfaces of the relative sliding.

[0028] Accordingly, the pieces of the sheared graphite film will transfer to the unevenness on the surface of the sliding surface on the opposite side, so that the sliding surface on the opposite side is also smoothed. Therefore, a better low-friction effect can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a longitudinal sectional view showing an example of a mechanical seal in an embodiment of the present invention;

[0030] Figure 2 is an enlarged sectional view showing the sliding surface of a rotating seal ring before use, on which a graphite film is formed, in the embodiment;

[0031] Figure 3 is an enlarged sectional view showing a state in which shear blocks are generated by the sliding of the sliding surface of a rotating seal ring on which a graphite film is formed and the sliding surface of a stationary seal ring in the embodiment;

[0032] Figure 4 is an enlarged sectional view showing the state after the sliding of the sliding surface of a rotating seal ring on which a graphite film is formed and the sliding surface of a stationary seal ring in the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0033] Hereinafter, a method for implementing the sliding member of the present invention will be described based on the embodiments.

[0034] Embodiment

[0035] Refer to Figures 1 to 4 The sliding member of the embodiment will be described. In addition, in the present embodiment, an example in which the sliding member is a mechanical seal will be described. Further, the inner diameter side of the sliding member constituting the mechanical seal is set as the leakage side, and the outer diameter side is set as the fluid side to be sealed for description.

[0036] Figure 1The mechanical seal for general industrial machinery shown is an internal type seal that seals the gas to be sealed leaking from the outer diameter side to the inner diameter side of the sliding surface in a non-lubricated environment where there is no liquid between the sliding surfaces, that is, in a dry environment, and mainly consists of the following parts: a circular rotating seal ring 20 as a sliding part, which is arranged on the rotating shaft 1 via a sleeve 2 in a state of being able to rotate together with the rotating shaft 1; and a circular stationary seal ring 10 as a sliding part, which is arranged on a seal cover 5 fixed to the housing 4 of the installed equipment in a non-rotating state and a state of being able to move axially. Among them, by applying a force to the stationary seal ring 10 axially by a spring 6, the sliding surface 11 of the stationary seal ring 10 and the sliding surface 21 of the rotating seal ring 20 are in close contact and slide with each other. In addition, the rotating seal ring 20 and the sleeve 2 are sealed by a gasket 7, and the stationary seal ring 10 and the seal cover 5 are sealed by an O-ring 8.

[0037] In this embodiment, the stationary seal ring 10 and the rotating seal ring 20 are formed of SiC (silicon carbide). In addition, the stationary seal ring 10 and the rotating seal ring 20 are not limited to being made of the same material and can also be made of different materials.

[0038] As Figure 2 shown, the rotating seal ring 20 is formed by covering a graphite film 30 on a SiC substrate 22 as a base material. That is, the substantial sliding surface 21 of the rotating seal ring 20 is formed by the surface 30a of the graphite film 30. In addition, for the sliding surface 21 of this embodiment, as will be described later, the case where the thickness of the graphite film 30 is thicker than the surface roughness of the SiC substrate 22 and the entire axial end face portion 22a of the SiC substrate 22 is covered by the graphite film 30 will be described, but it is not limited thereto. For example, the sliding surface 21 can also be such that by making the thickness of the graphite film 30 thinner, a part of the end face portion 22a of the SiC substrate 22, such as the top of the peak on the surface, is not covered by the graphite film 30 and is exposed. In addition, the graphite film 30 can be directly covered on the SiC substrate 22. Thus, compared with the case of having an intermediate layer, etc., there is no need to form an intermediate layer, and there are no restrictions on the usage conditions in cooperation with the intermediate layer.

[0039] In addition, in this embodiment, the graphite film 30 has a conventionally known layered structure of carbon, mainly consists of carbon atoms, is a kind of carbon material, mainly has a crystal structure of a hexagonal system, and is a general term for thin films of substances analyzed by Raman spectroscopy analysis, etc. In addition, in this embodiment, no graphite film is formed on the sliding surface 11 of the stationary seal ring 10 (refer to Figure 3 ).

[0040] Specifically, the graphite film 30 of this embodiment is a thin film having a composition in which the ratio of the region with significant characteristic manifestations of the graphite component in the surface is 50% to 100%. In the graphite film 30, carbon atoms are covalently bonded to each other to form a sheet crystal structure arranged in a hexagonal crystal system, and the thin sheet crystal structures are combined into a layered structure by van der Waals forces, thereby forming a graphite layer. In addition, a part of the carbon atoms may also form a vitreous carbon region composed of amorphous carbon that is not crystallized.

[0041] The graphite film 30 is formed as follows: A precursor solution obtained by dissolving one or more thermosetting resins selected from phenolic resin, melamine resin, urea resin, epoxy resin, unsaturated polyester resin, silicone resin, diallyl phthalate resin, polyimide resin, polyurethane resin, etc. in an organic solvent is directly coated so as to cover one end face 22a in the axial direction of the SiC substrate 22 constituting the rotary seal ring 20. After drying and curing treatment, it is heated and cured at a temperature of 800 °C or higher, preferably 1200 °C or higher, and then fired. In addition, by forming the graphite film 30 into a thin film with a specified thickness range, breakage of the film can be prevented, and the thermosetting resin can be graphitized by firing at a relatively low temperature. In addition, the graphite film 30 before initial use can also be formed to have a thickness of 1 μm to 100 μm. If the film thickness is thinner than the above value, peeling will occur between the SiC substrate 22, and if the film thickness is thicker than the above value, cracks will occur during film formation.

[0042] In addition, the arithmetic mean roughness Ra of the surface of the end face 22a of the SiC substrate 22 covered by the graphite film 30 is 0.1 μm or more, and the graphite film 30 is formed in a state where a part of the graphite film 30 enters the fine recesses 22b of the end face 22a of the SiC substrate 22.

[0043] In addition, the hardness of the graphite film 30 and the SiC substrate 12 was measured by a nanoindenter, and it was confirmed that the SiC substrate 12 exhibited a harder value than the graphite film 30.

[0044] As described above, the graphite film 30 of this embodiment forms a graphite layer by firing a thermosetting resin. In addition, the composition of the film in the graphite film 30 can be discriminated by analyzing the composition of the film through, for example, XRD, Raman spectroscopy, and thermal analysis.

[0045] Next, regarding the rotary seal ring 20 formed with the graphite film 30 in this embodiment, the results of the Ring-on-Ring friction / wear test made by changing the degree of graphitization and carried out under the following conditions will be described. In addition, the graphite film 30 of the rotary seal ring 20 is formed in a state where the thickness is uniform at 20 μm. In addition, as described above, the stationary seal ring 10 does not form a graphite film, and at least the sliding surface 11 is formed of SiC.

[0046] Load = 10 N

[0047] Surface pressure of the sliding surface of the stationary seal ring = 0.25 MPa

[0048] Rotational speed of the rotating seal ring = 74 rpm

[0049] PV value = 0.008 MPa·m / sec

[0050] Test time = until the sliding distance reaches 1000 m

[0051] Fluid to be sealed = atmosphere

[0052] In addition, regarding the graphite film 30 of the rotating seal ring 20 in this embodiment, the area region of graphitization on the surface was analyzed by Raman spectroscopy. In addition, in the analysis of the degree of graphitization on the surface of the graphite film 30, a spectroscopic analysis device manufactured by Nanophotonics was used, and the measurement was performed at a central wave number of 2082.24 cm -1 , an excitation wavelength of 532.36 nm, and a laser intensity of 0.8 mW. IG is the intensity of the G peak that appears at a central wave number of 1574 - 1576 cm -1 . ID is the intensity of the D peak that appears at a central wave number of 1344 - 1348 cm -1 . Multiple points in a specific region were measured in the specimen, and the intensity ratio ID / IG was calculated based on the intensities of the G and D peaks of the average spectrum, and a determination of whether it is graphite was made.

[0053] The analysis results of the degree of graphitization (area %) on the surface of the graphite film 30 of the rotating seal ring 20 in this embodiment and the test results of the Ring-on-Ring friction / wear test are shown in Table 1. In addition, regarding the Ring-on-Ring friction / wear test, a determination of whether it can be used was made based on whether galling of the sliding surface was found in a non-lubricated environment (〇 indicates no galling occurred). Furthermore, after the Ring-on-Ring friction / wear test, it was confirmed whether a transfer film was formed on the sliding surface 11 of the stationary seal ring 10. Regarding the confirmation of whether a transfer film was formed, the attached substances were removed by blowing air onto the sliding surface 11 of the stationary seal ring 10. At a magnification of 5 times with an optical microscope, if the transfer film accounted for 5% or less of the area within the contact range, it was determined that no transfer film was formed on the sliding surface 11 of the stationary seal ring 10.

[0054] [Table 1]

[0055] Sample Graphitization degree (area%) Usable or not Form transfer film A 90 ○ Yes B 70 ○ Yes C 50 ○ Yes D 30 × Yes E 10 × No

[0056] Regarding the graphite film 30 of the rotary seal ring 20 that exhibits galling without a sliding surface in a non-lubricated environment and has a transfer film formed on the sliding surface 11 of the stationary seal ring 10, it was found that the graphitization degree of the surface was 50% or more (Samples A, B, and C).

[0057] Next, regarding the rotary seal ring 20 with a graphite film 30 having a graphitization degree of 70%, the results of the Ring-on-Ring friction / wear test conducted under the following conditions will be described. Additionally, as described above, the stationary seal ring 10 does not form a graphite film, and at least the sliding surface 11 is made of SiC.

[0058] Load = 10 N

[0059] Surface pressure of the sliding surface of the stationary seal ring = 0.25 MPa

[0060] Rotational speed of the rotary seal ring = 74 rpm

[0061] PV value = 0.008 MPa·m / sec

[0062] Test time = until the sliding distance reaches 1000 m

[0063] Sealed fluid = atmosphere

[0064] The film formation results of the graphite film 30 of the rotary seal ring 20 (Samples F - G) and the test results of the Ring-on-Ring friction / wear test in this example are shown in Table 2. In addition, regarding the Ring-on-Ring friction / wear test, similar to Table 1, the determination of usability is based on whether galling of the sliding surface is found in a non-lubricated environment. Furthermore, after the Ring-on-Ring friction / wear test, it is confirmed whether the graphite film 30 has peeled off from the sliding surface 21 of the rotary seal ring 20 and whether there are cracks. Regarding the confirmation of whether the graphite film has peeled off, the adherents are removed by blowing air onto the sliding surface 21 of the rotary seal ring 20. If the remaining graphite film 30 in the fine recesses 22b of the end face portion 22a is 80% or less in terms of the area ratio within the contact range at a magnification of 5 times under an optical microscope, it is determined that there is peeling from the sliding surface 21 of the rotary seal ring 20. Regarding the confirmation of whether there are cracks in the graphite film, the adherents are removed by blowing air onto the sliding surface 21 of the rotary seal ring 20, and the presence of cracks is confirmed.

[0065] [Table 2]

[0066] Sample Film thickness (μm) Usable or not Peel off Crack F 1 ○ No No G 10 ○ No No H 20 ○ No No I 50 ○ No No K 100 ○ No No L 0.5 — Yes No M 120 — No Yes

[0067] Regarding the graphite film 30 of the rotary seal ring 20 that experiences sticking without a sliding surface in a non-lubricated environment and does not peel or crack from the sliding surface 21 of the rotary seal ring 20, it was found that the thickness is 1 μm to 100 μm (samples F, G, H, I, K).

[0068] In addition, with respect to the sliding surface 21 of the rotary seal ring 20 such as sample K above that does not form a graphite film 30, when the stationary seal ring 10 on the opposite side is made of a soft material, carbon, due to the intrusion of foreign matter between the sliding surfaces 11 and 21, the foreign matter bites into the sliding surface 11 of the stationary seal ring 10 made of soft carbon, the sliding surface 11 is scratched, resulting in surface roughness, and the smoothness of the sliding surface is lost, which has an adverse effect on the friction coefficient. Thus, there is a problem with the foreign matter resistance of the sliding surface of the sliding member made of carbon. In contrast, in the present embodiment, the rotary seal ring 20 is configured to have a graphite film 30 covering the hard SiC substrate 22, and the stationary seal ring 10 on the opposite side is also made of the hard material SiC. Therefore, for the intrusion of foreign matter between the sliding surfaces 11 and 21, the soft graphite film 30 is preferentially scratched, and it is not easy to generate surface roughness of the SiC substrates 12 and 22 that has an adverse effect on the friction coefficient of the sliding surface.

[0069] As described above, the SiC substrate 22 of the rotary seal ring 20 of the present invention is covered with the graphite film 30. Thus, the graphite film 30 constituting the sliding surface 21 is sheared between the layers of the graphite layers bonded by weak van der Waals forces by friction with the sliding surface 11 of the stationary seal ring 10 (refer to the enlarged portion of Figure 3 ), and is pressed axially by the pressing force between the sliding surfaces 11 and 21. A part of the graphite film 30 enters and remains in the fine recesses 22b of the end face portion 22a of the SiC substrate 22. Thus, the sliding surface 21 is smoothed (refer to the enlarged portion of Figure 4 ). Thus, the graphite film 30 remaining in the fine recesses 22b can exhibit the self-lubricity of graphite for the sliding surface 11 of the stationary seal ring 10. Therefore, a low friction effect can be stably obtained under a wide range of use conditions such as in the fluid lubrication region, boundary lubrication region, and non-lubricated environment. Moreover, the graphite film 30 is only formed on the sliding surface 21 of the rotary seal ring 20. Thus, the shear blocks P30 from the graphite film 30 generated between the sliding surfaces 11 and 21 (refer to the enlarged portion of Figure 3 ) are pressed axially by the pressing force between the sliding surfaces 11 and 21, enter and transfer to the fine recesses 12b of the end face portion 12a of the SiC substrate 12 constituting the sliding surface 11 of the stationary seal ring 10, and form a transfer film 31. Thus, the sliding surface 11 of the stationary seal ring 10 is also smoothed (refer to the enlarged portion of Figure 4(in the enlarged portion). Thus, between the sliding surfaces 11 and 21, the proportion of the sliding portions of SiC and graphite or graphite with each other becomes larger, so that a better low-friction effect can be obtained.

[0070] In addition, the hardness of the graphite film 30 is less than that of the sliding surfaces 11 of the stationary seal ring 10, that is, the hardness of the SiC substrate 12. Thus, the graphite film 30 is softer than the sliding surfaces 11 of the stationary seal ring 10 and is not easily damaged due to friction to the sliding surfaces 11 of the stationary seal ring 10. Moreover, the hardness of the graphite film 30 is less than that of the SiC substrate 22 of the rotating seal ring 20. Thus, when foreign matter intrudes between the sliding surfaces 11 and 21, the soft graphite film 30 is preferentially sheared, thereby promoting the smoothing of the sliding surface 21. The foreign matter resistance can be improved by the end face portion 22a of the exposed hard SiC substrate 22. Therefore, the self-lubricity of graphite and the foreign matter resistance can be achieved simultaneously between the sliding surfaces 11 and 21.

[0071] In addition, the substrate of the rotating seal ring 20 is formed of SiC as a ceramic, and the SiC substrate 22 is porous. Thus, there are many fine recesses 22b on the end face portion 22a for a part of the graphite film 30 to enter. Compared with metals, the surface roughness is more likely to occur. Therefore, the graphite film 30 is easily fixed on the substrate surface. Moreover, the arithmetic mean roughness Ra of the surface of the end face portion 22a of the SiC substrate 22 forming the graphite film 30 is 0.1 μm or more. Thus, a part of the graphite film 30 is more likely to enter the fine recesses 22b of the end face portion 22a. Therefore, even if the graphite film 30 is sheared due to friction with the sliding surfaces 11 of the stationary seal ring 10, a part of the graphite film 30 will be held in the fine recesses 22b and is not easily detached from between the sliding surfaces 11 and 21.

[0072] In addition, the entire end face portion 22a of the SiC substrate 22 is covered with the graphite film 30. In other words, the substrate surface is not exposed. Thus, it becomes a state where a part of the graphite film 30 enters all the fine recesses 22b of the end face portion 22a. Therefore, the sliding surface 21 is easily smoothed by the shearing of the graphite film 30.

[0073] In addition, the thickness of the graphite film 30 is 1 μm to 100 μm. Thus, it is possible to prevent the graphite film 30 from peeling off from the end face portion 22a of the SiC substrate 22 and to prevent the graphite film 30 from cracking. Therefore, it can be used as a film of a sliding member.

[0074] Moreover, the thickness of the graphite film 30 is greater than the arithmetic mean roughness Ra of the surface of the end face portion 22a of the SiC substrate 22, that is, the thickness of the graphite film 30 is greater than the unevenness of the surface of the end face portion 22a of the SiC substrate 22. Thus, a part of the graphite film 30 easily enters into the fine recesses 22b of the SiC substrate 22. The graphite film 30 is reliably sheared by the friction with the sliding surface 11 of the stationary seal ring 10. Therefore, a part of the graphite film 30 easily remains in the fine recesses 22b and can easily exhibit a low friction effect.

[0075] In addition, the graphite film 30 contains a vitreous carbon region in part. Thus, the shear blocks P30 generated by the shearing of the graphite film 30 are liable to become small, and the shear blocks P30 easily enter deep into the fine recesses 12b of the SiC substrate 12 constituting the stationary seal ring 10 on the opposite side. Therefore, it is easy to form a transfer film 31 on the sliding surface 11 of the stationary seal ring 10. Furthermore, even if the graphite film 30 contains a vitreous carbon region in part, it is mainly composed of graphite regions formed by graphite layers. Thus, the self-lubricity of graphite can be exhibited by the friction with the sliding surface 11 of the stationary seal ring 10.

[0076] In addition, the graphite film 30 is directly formed on the end face portion 22a of the SiC substrate 22. Thus, the adhesion to the end face portion 22a of the SiC substrate 22 is low. Therefore, compared with the case where the graphite film 30 is joined via an adhesive, for example, the graphite film 30 is liable to be sheared by the friction with the sliding surface 11 of the stationary seal ring 10. Thus, peeling of the graphite film 30 can be prevented.

[0077] In addition, the base material and the sliding surface of the rotary seal ring 20 can be formed of different materials. Thus, the base material can have the rigidity of ceramics such as SiC, and the self-lubricity can be imparted by the graphite film 30 on the sliding surface 21. Moreover, by changing the base material to an inexpensive material, the cost of the sliding member can be reduced.

[0078] As described above, the embodiments of the present invention have been described with reference to the drawings. However, the specific structure is not limited to these embodiments, and even if changes and additions are made without departing from the gist of the present invention, they are included in the present invention.

[0079] For example, in the above embodiment, as the sliding member, a mechanical seal for general industrial machinery is taken as an example for description, but it may also be other mechanical seals for automobiles, water pumps, etc. In addition, it is not limited to mechanical seals, and it may also be a sliding member other than mechanical seals such as a sliding bearing. Moreover, the graphite film 30 can also be formed on the inner peripheral surface of the bearing, and thus can also be applied to sliding members constituting a radial bearing or the like.

[0080] In addition, in the above-described embodiments, the case where the mechanical seal using the sliding member is used in a non-lubricated environment has been described. However, it is not limited thereto, and it may also be used in a fluid lubrication region or a boundary lubrication region where a liquid as the fluid to be sealed exists between the sliding surfaces.

[0081] In addition, in the above-described embodiments, an example in which the graphite film 30 is provided only on the rotating seal ring 20 has been described. However, the graphite film 30 may also be provided only on the stationary seal ring 10, or may be provided on both the rotating seal ring 20 and the stationary seal ring 10.

[0082] In addition, in the above-described embodiments, the case where the stationary seal ring 10 and the rotating seal ring 20 are formed of SiC has been described. However, it is not limited thereto, and it can be applied as long as the sliding material is used as a sliding material for a mechanical seal. In addition, as SiC, materials composed of two or more phases with different compositions, such as a sintered body obtained by using boron, aluminum, carbon, etc. as sintering aids, can be used. For example, SiC in which graphite particles are dispersed, reaction-sintered SiC composed of SiC and Si, etc. In addition, in addition to the above sliding materials, other ceramics such as alumina, zirconia, silicon nitride (Si3N4), metal materials, resin materials, composite materials, etc. can also be applied.

[0083] Symbol Explanation

[0084] 10: Stationary seal ring (sliding member); 11: Sliding surface; 12: SiC substrate (substrate); 12a: End face portion; 12b: Microscopic recess; 20: Rotating seal ring (sliding member); 21: Sliding surface; 22: SiC substrate (substrate); 22a: End face portion; 22b: Microscopic recess; 30: Graphite film; 30a: Surface; 31: Transfer film; P30: Shearing block.

Claims

1. A sliding member having sliding surfaces that slide relative to each other, wherein, a graphite film is covered on the base material of the sliding member, and the sliding surface is constituted by the graphite film; the base material is formed of ceramics; the graphite film is in contact with the base material; the graphite film includes a vitreous carbon region; the thickness of the graphite film is greater than the arithmetic mean roughness Ra of the surface of the base material; the graphite film is formed by firing a resin and has a graphitized surface region containing a graphite component; the ratio of the graphitized surface region to the surface area of the graphite film is 50%-90%; microscopic recesses are formed on the other sliding surface.

2. The sliding member according to claim 1, wherein, the hardness of the graphite film is less than the hardness of the sliding surface on the opposite side.

3. The sliding member according to claim 1 or 2, wherein, the hardness of the graphite film is less than the hardness of the base material.

4. The sliding member according to claim 1 or 2, wherein, the arithmetic mean roughness Ra of the surface of the base material is 0.1 μm or more.

5. The sliding member according to claim 1 or 2, wherein, the entire surface of the base material is covered by the graphite film.

6. The sliding member according to claim 1 or 2, wherein, the graphite film is formed only on one of the sliding surfaces that slide relative to each other.

7. A sliding member having sliding surfaces that slide relative to each other, wherein, a graphite film is covered on the base material of the sliding member, and the sliding surface is constituted by the graphite film; the base material is formed of ceramics; the graphite film is in contact with the base material; the graphite film includes a vitreous carbon region; the arithmetic mean roughness Ra of the surface of the base material is 0.1 μm or more; the graphite film is formed by firing a resin and has a graphitized surface region containing a graphite component; the ratio of the graphitized surface region to the surface area of the graphite film is 50%-90%; microscopic recesses are formed on the other sliding surface.

8. The sliding member according to claim 7, wherein, the hardness of the graphite film is less than the hardness of the sliding surface on the opposite side.

9. The sliding member according to claim 7 or 8, wherein, the hardness of the graphite film is less than the hardness of the base material.

10. The sliding member according to claim 7 or 8, wherein, the thickness of the graphite film is greater than the arithmetic mean roughness Ra of the surface of the base material.

11. The sliding member according to claim 7 or 8, wherein, the entire surface of the base material is covered by the graphite film.

12. The sliding member according to claim 7 or 8, wherein, the graphite film is formed only on one of the sliding surfaces that slide relative to each other.

13. A pair of sliding members whose sliding surfaces slide relative to each other, wherein, a graphite film is covered on the base material of one sliding member; the sliding surface of the one sliding member is constituted by the graphite film; the hardness of the graphite film is less than the hardness of the sliding surface of the other sliding member; the graphite film is formed by firing a resin and has a graphitized surface region containing a graphite component; the graphite film includes a vitreous carbon region; The ratio of the graphitized surface area region to the surface area of the graphite film is 50%-90%; Fine recesses are formed on the sliding surface on the other side.

14. The pair of sliding members according to claim 13, wherein, The base material of the other sliding member is formed of ceramic, and the sliding surface of the other sliding member is formed of ceramic.

15. The pair of sliding members according to claim 13 or 14, wherein, The base material of one sliding member is formed of ceramic.

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