Patent Description:
Sliding components have sliding surfaces sliding relative to each other and are used as components of a bearing supporting, for example, a rotating or reciprocating shaft or a shaft sealing device preventing sealing target fluid leakage. A mechanical seal as an example of the shaft sealing device preventing sealing target fluid leakage includes a pair of annular sliding components rotating relative to each other and having sliding surfaces sliding together. For example, the sliding component illustrated in Patent Citation <NUM> is formed of carbon, which is a soft material, and thus a low-friction effect can be obtained using the self-lubricating property of carbon. However, in the event of inter-sliding surface foreign matter intrusion, the sliding surface of the sliding component formed of carbon is easily scraped and there is a problem in terms of foreign matter resistance.

To provide a mechanical seal capable of bringing a sliding surface of a static sealing ring and a sliding surface of a rotary sealing ring into a low-friction state in an early stage in a mechanical seal according to Patent Citation <NUM>, one sealing ring prepared by coating a base material with a hard carbon thin film and the other sealing ring essentially composed of ceramic are relatively rotated and slid. A sliding surface of the other sealing ring is constituted by ceramic particles having a maximum particle diameter of <NUM> or less.

Patent Citation <NUM> relates to a metal slide member and a preparation method thereof. The metal slide member comprises a metal substrate layer, a first surface layer located above the metal substrate layer, and a second surface layer located between the first surface layer and the metal substrate layer, wherein the first surface layer is made from a material with a low friction coefficient or/and high wear resistance; the material of the second surface layer comprises elements which are the same as the elements of the material of the first surface layer; and the elements are selected from any one or many of sulfur, carbon, nitrogen and fluorine. The first surface layer has the characteristics of low friction coefficient and high wear resistance, and is not liable to fall off.

To provide a sliding member with reduced friction loss on a sliding surface under a non-lubricated condition or a friction environment condition with less oil film compared to a conventional low friction material such as isotropic graphite and having good wear resistance compared with when highly oriented graphite is used on the entire sliding surface in Patent Citation <NUM> a sliding member is described wherein a surface comprising a highly oriented specific graphite in which the half-value width is equal to or less than <NUM>° in a rocking curve at a graphite -<NUM> <NUM> diffraction position by X-ray diffraction measurement, and a surface comprising an alloy more superior in wear resistance than the highly oriented specific graphite, are provided toward the sliding direction in parallel with the sliding direction at a portion of a skirt part which is the sliding surface.

Foreign matter resistance can be enhanced by a sliding component being formed of SiC, which is a hard material (for example, Patent Citation <NUM>). However, in a case where a mechanical seal is used in, for example, a non-lubricated (dry) environment in which no liquid is interposed between sliding surfaces, galling may arise on the sliding surface depending on the conditions of use due to the high friction coefficient of SiC in the atmosphere. In addition, the sliding component in Patent Citation <NUM> has a sliding surface covered with a diamond-like carbon coating (hereinafter, referred to as a DLC coating in some cases). The hardness of the DLC coating is high, and thus galling may arise on the sliding surface on the other side depending on the conditions of use in the case of use in a non-lubricated environment or the like. The sliding component in Patent Citation <NUM> is poor in versatility as a low-friction effect can be obtained only after complicated condition setting such as a change in, for example, the hydrogen content of the DLC coating in accordance with the conditions of use.

The present invention has been made in view of such problems, and an object of the present invention is to provide a sliding component capable of obtaining a stable low-friction effect under a wide range of conditions of use.

In order to solve the above problem, sliding components according to the present invention having sliding surfaces sliding relative to each other, a base material of one of the sliding components is coated with a graphite film and the sliding surface of the one of the sliding components is made of the graphite film, wherein the base material is formed of ceramics, the graphite film is brought into contact with the base material, and a surface of the base material which extends along sliding surface is entirely covered with the graphite film, wherein the graphite film is lower in hardness than the sliding surface of the remaining one of the sliding components. According to the aforesaid feature of the present invention, the base material of the sliding component is coated with the graphite film. As a result, the graphite film constituting the sliding surface is sheared between the layers of a graphite layer bonded by the van der Waals force as a result of friction with the sliding surface on the other side. A part of the graphite film remains in fine recesses of the surface of the base material, and thus the sliding surface is smoothed and the self-lubricating property of graphite can be exhibited with respect to the sliding surface on the other side. Accordingly, a stable low-friction effect can be obtained under a wide range of conditions of use such as fluid and boundary lubrication regions and a non-lubricated environment.

According to the present invention that the graphite film is lower in hardness than the sliding surface of remaining one of the sliding components. According to this configuration, the graphite film is softer than the sliding surface of the remaining one of the sliding components, and thus the sliding surface of the remaining one of the sliding components is unlikely to be damaged by friction.

It may be preferable that the graphite film is lower in hardness than the base material. According to this preferable configuration, the base material covered with the graphite film is harder than the graphite film. Accordingly, the soft graphite film is preferentially scraped and smoothing of the sliding surface is promoted in the event of foreign matter intrusion between the sliding surfaces, foreign matter resistance can be enhanced by the exposed base material surface, and thus both the self-lubricating property of graphite and foreign matter resistance can be achieved between the sliding surfaces.

It may be preferable that the graphite film has a thickness larger than an arithmetic mean roughness Ra of a surface of the base material. According to this preferable configuration, the thickness of the graphite film is larger than the unevenness of the base material surface, and thus a part of the graphite film easily enters the fine recesses of
the base material and a low-friction effect is exhibited with ease.

According to the present invention the base material is formed of ceramics. According to this configuration, the surface roughness of the porous ceramics is more likely to appear than that of a metal, and thus the graphite film is easily fixed on the base material.

It may be preferable that an arithmetic mean roughness Ra of a surface of the base material is <NUM> or more. According to this preferable configuration, the graphite film easily enters the fine recesses of the base material surface. Accordingly, even in the event of shearing of the graphite film attributable to friction with the sliding surface on the other side, a part of the graphite film is held in the fine recesses and is unlikely to fall off.

According to the present invention the surface of the base material is entirely covered with the graphite film. According to this configuration, a part of the graphite film on the base material side enters every fine recess of the base material surface, and thus the sliding surface is easily smoothed by the graphite film being sheared.

surface on the other side, a part of the graphite film is held in the fine recesses and is unlikely to fall off.

It may be preferable that the graphite film is formed on only the sliding surface of the one of the sliding components sliding relative to each other. According to this preferable configuration, the mass of the sheared graphite film transfers to the unevenness of the sliding surface of the remaining one of the sliding components, and thus the sliding surface of the remaining one of the sliding components is also smoothed and a more satisfactory low-friction effect can be obtained.

A mode for implementing the sliding component according to the present invention will be described below based on an embodiment.

The sliding components according to the embodiment of the present invention will be described with reference to <FIG>. It should be noted that a mode in which the sliding component is a mechanical seal will be described as an example in the present embodiment. In addition, in the following description, the inner diameter side of the sliding component constituting the mechanical seal is a low-pressure fluid side as a leak side and the outer diameter side is a high-pressure fluid side (e.g., sealing target gas side) as a sealing target fluid side.

The mechanical seal for general industrial machinery illustrated in <FIG> is an inside-type mechanical seal that seals a sealing target gas to leak from the outer diameter side toward the inner diameter side of a sliding surface in a non-lubricated (that is, dry) environment in which no liquid is interposed between the sliding surfaces. The mechanical seal mainly includes an annular rotating seal ring <NUM>, which is a sliding component provided on a rotary shaft <NUM> in a state of being rotatable together with the rotary shaft <NUM> via a sleeve <NUM>, and an annular stationary seal ring <NUM>, which is a sliding component provided on a seal cover <NUM> fixed to a housing <NUM> of an attachment target device in a non-rotating state and a state of being movable in the axial direction. A sliding surface <NUM> of the stationary seal ring <NUM> and a sliding surface <NUM> of the rotating seal ring <NUM> slide closely with each other by a spring <NUM> urging the stationary seal ring <NUM> in the axial direction. In addition, the space between the rotating seal ring <NUM> and the sleeve <NUM> is sealed by a gasket <NUM> and the space between the stationary seal ring <NUM> and the seal cover <NUM> is sealed by an O-ring <NUM>.

The stationary seal ring <NUM> and the rotating seal ring <NUM> in the present embodiment are formed of silicon carbide (abbreviated as SiC). It should be noted that the stationary seal ring <NUM> and the rotating seal ring <NUM> may be made of different materials without being limited to those made of the same material.

As illustrated in <FIG>, the rotating seal ring <NUM> is configured by a graphite film <NUM> covering a SiC base material <NUM> as a base material. In other words, the substantially sliding surface <NUM> of the rotating seal ring <NUM> is configured by a surface 30a of the graphite film <NUM>. It should be noted that an aspect in which the thickness of the graphite film <NUM> is thicker than the surface roughness of the SiC base material <NUM> and the graphite film <NUM> covers the entire surface of an axial end surface portion 22a of the SiC base material <NUM> as will be described later will be described as to the sliding surface <NUM> of the present embodiment and yet the present invention is not limited thereto. For example, as for the sliding surface <NUM>, a part of the end surface portion 22a of the SiC base material <NUM> (such as the top of the mountain of the surface) may be exposed without being covered with the graphite film <NUM> by the graphite film <NUM> being thin. In addition, the graphite film <NUM> may directly cover the SiC base material <NUM>. In this case as compared with a case where an intermediate layer or the like is provided, there is no need to form an intermediate layer and there are no restrictions on the conditions of use put by the intermediate layer.

In addition, in the present embodiment, the graphite film <NUM> has an existing and known layered structure of carbon and is a general term for thin films of substances mainly configured by carbon atoms, mainly having a hexagonal crystal structure as a type of carbon material, and analyzed by Raman spectroscopic analysis or the like. In addition, in the present embodiment, no graphite film is formed on the sliding surface <NUM> of the stationary seal ring <NUM> (see <FIG>).

Specifically, the graphite film <NUM> of the present embodiment is a thin film having a composition in which the ratio of the surface region where graphite component characteristics are conspicuous is <NUM>% to <NUM>%. In the graphite film <NUM>, carbon atoms constitute a sheet-shaped crystal structure in a hexagonal system by a covalent bond and the thin sheet-shaped crystal structure is bonded in layers by the van der Waals force to form a graphite layer. It should be noted that some of the carbon atoms may form a glassy carbon region configured by uncrystallized amorphous carbon.

The graphite film <NUM> is formed by directly applying a precursor solution so as to cover the axial end surface portion 22a of the SiC base material <NUM> constituting the rotating seal ring <NUM>, performing drying and curing, and then performing firing after thermal curing at a temperature of <NUM> or higher (preferably <NUM> or higher). The precursor solution is obtained by dissolving, in an organic solvent, one or more thermosetting resins selected from phenol resin, melamine resin, urea resin, epoxy resin, unsaturated polyester resin, silicone resin, diallyl phthalate resin, polyimide resin, polyurethane resin, etc. It should be noted that the graphite film <NUM> can be prevented from being torn by being formed into a thin film having a thickness in a predetermined range and the thermosetting resin can be graphitized by firing at a relatively low temperature. Further, it should be noted that the graphite film <NUM> before initial use may be formed so as to have a thickness of <NUM> to <NUM>. Peeling occurs in relation to the SiC base material <NUM> at a film thickness exceeded by the value, and cracking occurs during the film formation at a film thickness exceeding the value.

In addition, the surface of the end surface portion 22a of the SiC base material <NUM> covered with the graphite film <NUM> has an arithmetic mean roughness Ra of <NUM> or more and the graphite film <NUM> is formed with a part of the graphite film <NUM> inserted in fine recesses 22b of the end surface portion 22a of the SiC base material <NUM>.

In addition, a test was conducted using a nanoindenter in measuring the hardness of the graphite film <NUM> and the hardness of a SiC base material <NUM> and it was confirmed that the SiC base material <NUM> showed a harder value than the graphite film <NUM>.

As described above, a graphite layer is formed by thermosetting resin firing in the graphite film <NUM> of the present embodiment. It should be noted that the film composition in the graphite film <NUM> can be determined by film composition analysis by, for example, XRD, Raman spectroscopic analysis, or thermal analysis.

Next, the result of preparation at different degrees of graphitization and a Ring-on-Ring friction/wear test under the following conditions will be described with regard to the rotating seal ring <NUM> where the graphite film <NUM> in the present embodiment is formed. It should be noted that the graphite film <NUM> of the rotating seal ring <NUM> is formed at a uniform thickness of <NUM>. In addition, the stationary seal ring <NUM> is graphite film-less as described above and at least the sliding surface <NUM> is formed of SiC.

In addition, the graphitized area region of the surface of the graphite film <NUM> of the rotating seal ring <NUM> in the present embodiment was analyzed by Raman spectroscopic analysis. It should be noted that the degree of graphitization of the surface of the graphite film <NUM> was analyzed using a spectroscopic analyzer manufactured by Nanophoton Corporation and measurement was performed at a central wavenumber of <NUM>-<NUM>, an excitation wavelength of <NUM>, and a laser intensity of <NUM> mW. IG is the intensity of the G peak at a central wavenumber of <NUM> to <NUM>-<NUM>. ID is the intensity of the D peak at a central wavenumber of <NUM> to <NUM>-<NUM>. A plurality of points in a specific region were measured in the sample and intensity ratio ID/IG was calculated from the G peak intensity and the D peak intensity of the averaged spectrum in carrying out the graphite or non-graphite determination.

Table <NUM> shows analysis results on the degree of graphitization (e.g., area%) of the surface of the graphite film <NUM> of the rotating seal ring <NUM> in the present embodiment and the result of the Ring-on-Ring friction/wear test. It should be noted that usability was determined with regard to the Ring-on-Ring friction/wear test, in a non-lubricated environment, and based on whether or not seizure of the sliding surface was exhibited (O indicating seizure-free). Further, it should be noted that the presence or absence of transfer film formation on the sliding surface <NUM> of the stationary seal ring <NUM> was checked after the Ring-on-Ring friction/wear test. In checking the presence or absence, it was determined that the sliding surface <NUM> of the stationary seal ring <NUM> is transfer film-less on condition that a transfer film has an intra-contact range area ratio of <NUM>% or less at a magnification of optical microscope 5x with deposits removed by air blowing on the sliding surface <NUM> of the stationary seal ring <NUM>.

Regarding the graphite film <NUM> of the rotating seal ring <NUM> lacking sliding surface seizure with a transfer film formed on the sliding surface <NUM> of the stationary seal ring <NUM> in the non-lubricated environment, it was found that the degree of graphitization of the surface was <NUM>% or more (see Samples A, B, and C).

Next, the result of a Ring-on-Ring friction/wear test under the following conditions will be described with regard to the rotating seal ring <NUM> where the graphite film <NUM> is formed with a degree of graphitization of <NUM>%. In addition, the stationary seal ring <NUM> is graphite film-less as described above and at least the sliding surface <NUM> is formed of SiC. <MAT> <MAT> <MAT> <MAT> <MAT> Sealing target fluid = atmosphere.

Table <NUM> shows the film formation result of the graphite film <NUM> of the rotating seal ring <NUM> (see Samples F to G) in the present embodiment and the result of the Ring-on-Ring friction/wear test. It should be noted that usability was determined with regard to the Ring-on-Ring friction/wear test, in a non-lubricated environment, and based on whether or not seizure of the sliding surface was exhibited as in the case of Table <NUM>. Further, it should be noted that the presence or absence of peeling of the graphite film <NUM> from the sliding surface <NUM> of the rotating seal ring <NUM> and the presence or absence of cracking were checked after the Ring-on-Ring friction/wear test. In checking the presence or absence of peeling, it was determined that the peeling from the sliding surface <NUM> of the rotating seal ring <NUM> occurred on condition that the residue of the graphite film <NUM> in the fine recesses 22b of the end surface portion 22a has an intra-contact range area ratio of <NUM>% or less at a magnification of optical microscope 5x with deposits removed by air blowing on the sliding surface <NUM> of the rotating seal ring <NUM>. The presence or absence of graphite film cracking was checked with deposits removed by air blowing on the sliding surface <NUM> of the rotating seal ring <NUM>.

Regarding the graphite film <NUM> of the rotating seal ring <NUM> lacking sliding surface seizure, peeling of the graphite film <NUM> from the sliding surface <NUM> of the rotating seal ring <NUM>, and cracking in the non-lubricated environment, it was found that the thickness was <NUM> to <NUM> (see Samples F, G, H, I, and K).

It should be noted that foreign matter is caught in the sliding surface <NUM> of the stationary seal ring <NUM> formed of soft carbon as a result of foreign matter intrusion between the sliding surfaces <NUM> and <NUM>, the surface is roughened by the sliding surface <NUM> being scraped, the smoothness of the sliding surface is lost, and the friction coefficient is adversely affected in a case where the stationary seal ring <NUM> on the other side is formed of carbon (as a soft material) with respect to the sliding surface <NUM> lacking the graphite film <NUM> as in the case of the rotating seal ring <NUM> of Sample K described above. As described above, a sliding surface of a sliding component formed of carbon is problematic in terms of foreign matter resistance. On the other hand, the rotating seal ring <NUM> in the present embodiment is configured by the graphite film <NUM> covering the hard SiC base material <NUM>, the stationary seal ring <NUM> on the other side is also formed of SiC (hard material), and thus the soft graphite film <NUM> is preferentially scraped against foreign matter intrusion between the sliding surfaces <NUM> and <NUM> and surface roughening of the SiC base materials <NUM> and <NUM> to adversely affect the friction coefficient of the sliding surface is unlikely to occur.

As described above, the graphite film <NUM> covers the SiC base material <NUM> of the rotating seal ring <NUM> according to the present invention. As a result, the graphite film <NUM> constituting the sliding surface <NUM> is sheared between the layers of the graphite layer bonded by a weak van der Waals force as a result of friction with the sliding surface <NUM> of the stationary seal ring <NUM> (see the enlarged part in <FIG>). In addition, the pressure contact force between the sliding surfaces <NUM> and <NUM> results in inward pushing in the axial direction, a part of the graphite film <NUM> enters and remains in the fine recesses 22b of the end surface portion 22a of the SiC base material <NUM>, and the sliding surface <NUM> is smoothed (see the enlarged part in <FIG>). As a result, the graphite film <NUM> remaining in the fine recesses 22b is capable of exhibiting the self-lubricating property of graphite with respect to the sliding surface <NUM> of the stationary seal ring <NUM>, and thus a stable low-friction effect can be obtained under a wide range of conditions of use such as fluid and boundary lubrication regions and a non-lubricated environment. Further, the graphite film <NUM> is formed only on the sliding surface <NUM> of the rotating seal ring <NUM>, and thus a shear mass P30 (see the enlarged part in <FIG>) derived from the graphite film <NUM> and generated between the sliding surfaces <NUM> and <NUM> is axially pushed in by the pressure contact force between the sliding surfaces <NUM> and <NUM>, enters and transfers into fine recesses 12b of an end surface portion 12a of the SiC base material <NUM> constituting the sliding surface <NUM> of the stationary seal ring <NUM>, and forms a transfer film <NUM>. As a result, the sliding surface <NUM> of the stationary seal ring <NUM> is also smoothed (see the enlarged part in <FIG>), the ratio of the SiC-graphite or graphite-graphite sliding part increases between the sliding surfaces <NUM> and <NUM>, and thus a more satisfactory low-friction effect can be obtained.

In addition, the hardness of the graphite film <NUM> is lower than the hardness of the sliding surface <NUM> of the stationary seal ring <NUM>, that is, the SiC base material <NUM>. Accordingly, the graphite film <NUM> is softer than the sliding surface <NUM> of the stationary seal ring <NUM> and the sliding surface <NUM> of the stationary seal ring <NUM> is unlikely to be damaged by friction. Further, the hardness of the graphite film <NUM> is lower than the hardness of the SiC base material <NUM> of the rotating seal ring <NUM>. Accordingly, the soft graphite film <NUM> is preferentially sheared and smoothing of the sliding surface <NUM> is promoted in the event of foreign matter intrusion between the sliding surfaces <NUM> and <NUM>, foreign matter resistance can be enhanced by the end surface portion 22a of the exposed hard SiC base material <NUM>, and thus both the self-lubricating property of graphite and foreign matter resistance can be achieved between the sliding surfaces <NUM> and <NUM>.

In addition, the base material of the rotating seal ring <NUM> is formed of SiC as ceramics and the SiC base material <NUM> is porous. Accordingly, the end surface portion 22a has the multiple fine recesses 22b, where a part of the graphite film <NUM> enters, surface roughness is more likely to appear than in a metal, and thus the graphite film <NUM> is likely to be fixed on the base material surface. Further, the arithmetic mean roughness Ra of the surface of the end surface portion 22a of the SiC base material <NUM>, where the graphite film <NUM> is formed, is <NUM> or more, and thus a part of the graphite film <NUM> is more likely to enter the fine recesses 22b of the end surface portion 22a. Accordingly, even in the event of shearing of the graphite film <NUM> attributable to friction with the sliding surface <NUM> of the stationary seal ring <NUM>, a part of the graphite film <NUM> is held in the fine recesses 22b and is unlikely to fall off between the sliding surfaces <NUM> and <NUM>.

In addition, the graphite film <NUM> covers the entire surface of the end surface portion 22a of the SiC base material <NUM>. In other words, the base material surface is not exposed. As a result, a part of the graphite film <NUM> is in every fine recesses 22b in the end surface portion 22a, and thus the sliding surface <NUM> is easily smoothed by the graphite film <NUM> being sheared.

In addition, the graphite film <NUM> has a thickness of <NUM> to <NUM>, and thus peeling of the graphite film <NUM> from the end surface portion 22a of the SiC base material <NUM> and cracking of the graphite film <NUM> can be prevented. Accordingly, the graphite film <NUM> can be used as a sliding component film.

Further, the thickness of the graphite film <NUM> is larger than the arithmetic mean roughness Ra of the surface of the end surface portion 22a of the SiC base material <NUM>. In other words, the thickness of the graphite film <NUM> is larger than the unevenness of the surface of the end surface portion 22a of the SiC base material <NUM>. Accordingly, a part of the graphite film <NUM> easily enters the fine recesses 22b of the SiC base material <NUM>, the graphite film <NUM> is reliably sheared by friction with the sliding surface <NUM> of the stationary seal ring <NUM>, and thus a part of the graphite film <NUM> easily remains in the fine recesses 22b and a low-friction effect is exhibited with ease.

In addition, the graphite film <NUM> partially contains a glassy carbon region. Accordingly, the shear mass P30 resulting from the shearing of the graphite film <NUM> is likely to be small, the shear mass P30 is likely to fully enter the fine recesses 12b of the SiC base material <NUM> constituting the stationary seal ring <NUM> on the other side, and thus the transfer film <NUM> is likely to be formed on the sliding surface <NUM> of the stationary seal ring <NUM>. It should be noted that the main region of the graphite film <NUM> is the graphite region made of a graphite layer although the graphite film <NUM> partially contains the glassy carbon region, and thus the self-lubricating property of graphite can be exhibited by friction with the sliding surface <NUM> of the stationary seal ring <NUM>.

In addition, the graphite film <NUM> is formed directly on the end surface portion 22a of the SiC base material <NUM>. As a result, adhesiveness is low in relation to the end surface portion 22a of the SiC base material <NUM>. Accordingly, the graphite film <NUM> is more likely to be sheared as a result of friction with the sliding surface <NUM> of the stationary seal ring <NUM> than in a case where, for example, the graphite film <NUM> is bonded via an adhesive. As a result, peeling of the graphite film <NUM> can be prevented.

In addition, the base material of the rotating seal ring <NUM> and the sliding surface can be formed of different materials, and thus the self-lubricating property of graphite can be given by the graphite film <NUM> on the sliding surface <NUM> while the base material is given the rigidity of ceramics such as SiC. Further, the cost of the sliding component can be reduced by changing the base material to an inexpensive material.

Although an embodiment of the present invention has been described above with reference to the drawings, the specific configurations are not limited to the embodiment and any changes or additions within the scope of the present invention are included in the present invention.

For example, although the mechanical seal for general industrial machinery has been described as an example of the sliding component in the above embodiment, the mechanical seal may be replaced with another mechanical seal for an automobile, a water pump, or the like. In addition, the present invention is not limited to the mechanical seal and may be a sliding component other than a mechanical seal, examples of which include a slide bearing. Further, the graphite film <NUM> can be formed on the inner peripheral surface of a bearing as well and thus is also applicable to a sliding component constituting a radial bearing or the like.

In addition, although the mechanical seal to which the sliding component is applied is used in a non-lubricated environment in the above embodiment, the present invention is not limited thereto and it may be used in a fluid or boundary lubrication region in which a liquid as a sealing target fluid is interposed between the sliding surfaces.

In addition, although an example in which the graphite film <NUM> is provided only on the rotating seal ring <NUM> has been described in the above embodiment, the graphite film <NUM> may be provided only on the stationary seal ring <NUM> or may be provided on both the rotating seal ring <NUM> and the stationary seal ring <NUM>.

Claim 1:
Sliding components (<NUM>, <NUM>) having sliding surfaces (<NUM>, <NUM>) sliding relative to each other,
wherein a base material (<NUM>, <NUM>) of one of the sliding components (<NUM>, <NUM>) is coated with a graphite film (<NUM>) and the sliding surface (<NUM>, <NUM>) of the one of the sliding components (<NUM>, <NUM>) is made of the graphite film (<NUM>),
wherein
the base material (<NUM>, <NUM>) is formed of ceramics,
the graphite film (<NUM>) is brought into contact with the base material (<NUM>, <NUM>),
and
a surface of the base material (<NUM>, <NUM>) which extends along sliding surface (<NUM>, <NUM>) is entirely covered with the graphite film (<NUM>),
characterized in that
the graphite film (<NUM>) is lower in hardness than the sliding surface (<NUM>, <NUM>) of the remaining one of the sliding components (<NUM>, <NUM>).