Sliding member

Abstract

A sliding member according to the present disclosure comprises a base material and a coating layer that is layered directly or indirectly on at least part of the surface of the base material. The coating layer contains an engineering plastic having a pencil hardness of 3H or greater, a solid lubricant, and a silicon compound. The solid lubricant is polytetrafluoroethylene, a tetrafluoroethylene-perfluoroalkoxy ethylene copolymer, molybdenum disulfide, graphite, a tetrafluoroethylene-hexafluoropropylene copolymer, an ultra-high-molecular-weight polyethylene, or a combination thereof. The silicon compound content of the coating layer 0.01 to less than 10 mass%.

Description

Sliding member

[0001] This application claims priority to Japanese Patent Application No. 2024-012350, filed on January 30, 2024, and incorporates by reference all of the contents of the above-mentioned Japanese application.

[0002] Wear resistance and heat resistance are required for sliding members provided in rotary devices and components, such as oil pumps that pump engine oil to various locations inside an engine. Cross-linked fluororesins have been disclosed as coating agents for rotors, which serve as sliding parts in such oil pumps. Prior art has proposed, for example, coating a substrate with a fluororesin irradiated with ionizing radiation (see Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2011-208802

[0004] The sliding member of the present disclosure comprises a substrate and a coating layer laminated directly or indirectly on at least a portion of the surface of the substrate, the coating layer containing an engineering plastic having a pencil hardness of 3H or more, a solid lubricant, and a silicon compound, the solid lubricant being polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkoxyethylene copolymer, molybdenum disulfide, graphite, tetrafluoroethylene-hexafluoropropylene copolymer, ultra-high molecular weight polyethylene, or a combination thereof, and the content of the silicon compound in the coating layer is 0.01% by mass or more and less than 10% by mass.

[0005] Fig. 1 is a schematic cross-sectional view showing a sliding member according to one embodiment, Fig. 2 is a schematic cross-sectional view showing a sliding member according to another embodiment, and Fig. 3 is a schematic cross-sectional view showing a sliding member according to another embodiment.

[0006] [Problem to be Solved by the Present Disclosure] In recent years, with the increasing demand for higher rotation speeds and improved fuel efficiency in internal combustion engines and the like, further improvements in the wear resistance of sliding members provided in, for example, rotary devices and parts are being demanded. Furthermore, when a coating film using a fluororesin paint is used on a sliding member as in the prior art, the coating film is relatively soft, and therefore metallic foreign matter such as iron powder is likely to penetrate and become embedded in the surface of the coating film. As a result, scratches, tears, etc., are likely to occur on the surface of the coating film. When such scratches, tears, etc. occur on the surface of the coating film, there is a problem that, in the case of a sliding member provided in, for example, a rotary device or part, an increase in torque is caused.

[0007] An object of the present disclosure is to provide a sliding member that is excellent in surface properties and wear resistance.

[0008] [Advantages of the Present Disclosure] The sliding member of the present disclosure has excellent surface properties and wear resistance.

[0009] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described.

[0010] (1) A sliding member according to the present disclosure comprises a substrate and a coating layer laminated directly or indirectly on at least a portion of the surface of the substrate, the coating layer containing an engineering plastic having a pencil hardness of 3H or more, a solid lubricant, and a silicon compound, the solid lubricant being polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkoxyethylene copolymer, molybdenum disulfide, graphite, tetrafluoroethylene-hexafluoropropylene copolymer, ultra-high molecular weight polyethylene, or a combination thereof, and the silicon compound content in the coating layer is 0.01% by mass or more and less than 10% by mass.

[0011] The sliding member comprises a substrate and a coating layer laminated directly or indirectly on at least a portion of the surface of the substrate. The coating layer contains an engineering plastic with a pencil hardness of 3H or higher, thereby increasing the hardness of the coating layer. This improves the abrasion resistance of the coating layer during sliding, resulting in a sliding member that can withstand long-term use. Furthermore, the coating layer contains a solid lubricant, and the solid lubricant is polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkoxyethylene copolymer, molybdenum disulfide, graphite, tetrafluoroethylene-hexafluoropropylene copolymer, ultra-high molecular weight polyethylene, or a combination thereof, thereby improving the sliding properties of the sliding member. Furthermore, the coating layer contains a silicon compound, and the silicon compound content in the coating layer is 0.01% by mass or more but less than 10% by mass, thereby improving coatability. This improves the smoothness of the coating layer, thereby enhancing the sliding properties of the coating layer. Therefore, the sliding member has excellent surface properties and wear resistance. Here, "pencil hardness" refers to a value measured in accordance with JIS-K5600-5-4:1999 "General testing methods for paints - Part 5: Mechanical properties of coating films - Section 4: Scratch hardness (pencil method)." "Ultra-high molecular weight polyethylene" refers to polyethylene with a weight-average molecular weight of 500,000 or more (typically 1,000,000 or more, for example, 1,000,000 to 7,000,000). "Weight-average molecular weight" refers to the weight-average molecular weight measured by gel permeation chromatography and converted into polystyrene.

[0012] (2) In the above (1), the coating layer may have an average thickness of 3.0 μm or more. By having the average thickness of the coating layer of 3.0 μm or more, thickness unevenness of the coating layer can be reduced while maintaining a thickness that can improve wear resistance, and the surface properties and wear resistance of the coating layer of the sliding member can be further improved. The "average thickness" refers to the average value of thicknesses measured at any ten points.

[0013] (3) In the above (1) or (2), the flatness of the surface of the coating layer may be 0.005 or less. When the flatness of the surface of the coating layer is 0.005 or less, the slipperiness of the surface of the coating layer is improved, and the surface properties and wear resistance of the coating layer in the sliding member can be further improved. Here, the "flatness" is a value measured in accordance with JIS-B0684-1:2019.

[0014] (4) In any one of (1) to (3) above, the engineering plastic may be polyimide or polyamideimide, and the silicon compound may be modified polydimethylsiloxane. By using polyimide or polyamideimide as the engineering plastic and modified polydimethylsiloxane as the silicon compound, the sliding member can have improved surface properties and wear resistance.

[0015] (5) In any one of (1) to (4) above, the substrate may be a metal sintered body. The surface of a metal sintered body has pores and an uneven shape, so that when the substrate is a metal sintered body, the adhesion between the substrate and the coating layer can be improved.

[0016] (6) In any of (1) to (5) above, at least some of the corners of the base may have chamfered portions, and the coating layer may be laminated on a region of the surface of the base that includes the chamfered portions. When the base has chamfered portions, the chamfered portions are easily pressed hard and prone to wear. However, by laminating the coating layer on a region of the surface of the base that includes the chamfered portions, the durability of the sliding member can be improved until the chamfered portions of the base and their vicinity wear down to expose the surface of the base. Furthermore, when the sliding member is used in an oil pump or compressor, the coating layer laminated on a region that includes the chamfered portions can further reduce oil leakage and improve volumetric efficiency. Thus, when at least some of the corners of the base have chamfered portions, the sliding member can more effectively achieve the effects of the present disclosure.

[0017] (7) In any of the above (1) to (6), the substrate may have a shape having a first surface and a second surface facing each other, and a coating layer may be laminated directly or indirectly on the first surface and the second surface of the substrate. By laminating the coating layer directly or indirectly on the first surface and the second surface of the substrate, the surface properties and abrasion resistance of the first surface and the second surface of the substrate can be improved.

[0018] (8) In the above (7), the parallelism of the coating layer on the first and second surfaces of the substrate may be 0.005 or less. In the sliding member, when the parallelism of the coating layer on the first and second surfaces of the substrate is 0.005 or less, the surface slipperiness of the coating layer is improved, and the surface quality and wear resistance of the coating layer in the sliding member can be further improved. The "parallelism" is a value measured in accordance with JIS-B0621:1984.

[0019] [Details of Embodiments of the Present Disclosure] Hereinafter, a sliding member according to an embodiment of the present disclosure will be described in detail with reference to the drawings.

[0020] <Slide Member> A slide member according to one embodiment of the present disclosure includes a substrate and a coating layer that is directly or indirectly laminated on at least a portion of the surface of the substrate.

[0021] The shape of the substrate is not particularly limited and can be changed appropriately depending on the application. For example, it is not limited to a plate-like, cylindrical, conical, elliptical cone-like, pyramidal, gourd-like, elliptical cylinder-like, or rectangular cylinder-like shape, and various shapes of sliding members such as rotors can be used.

[0022] Fig. 1 is a schematic cross-sectional view showing a slide member 1 according to an embodiment of the present disclosure. The slide member 1 in Fig. 1 includes a base 2 having a shape with a first surface and a second surface facing each other, and a coating layer 3 laminated directly on the first surface of the base 2.

[0023] [Substrate] The main component of the substrate 2 is not particularly limited, and examples thereof include metals, super engineering plastics, ceramics, and carbon materials. Examples of the metals include iron alloys such as stainless steel, nickel, aluminum, aluminum alloys, copper, and copper alloys. The metals can be used alone or in combination of two or more. Examples of the super engineering plastics include polyimide, polyamideimide, polyetherimide, polyetheretherketone, polyphenylene sulfide, polyarylate, liquid crystal polymer, polysulfone, and polyethersulfone. Examples of the ceramics include alumina, aluminum nitride, silicon nitride, boron nitride, silicon carbide, zirconia, cordierite, sialon, steatite, sapphire, and cermet. Examples of the carbon materials include diamond, graphite, C / C composites, and C / SiC composites. The substrate 2 may be a metal sintered body obtained by sintering the above metals. The surface of a metal sintered body has pores and an uneven shape, so that using a metal sintered body for the base 2 can improve adhesion between the base 2 and the coating layer 3. A metal sintered body is formed by compressing a metal powder material in a mold and heating the resulting powder compact at a high temperature below the melting point. The "main component" mentioned above refers to the component with the highest content ratio in terms of mass, for example, a component with a content of 60 mass% or more.

[0024] The average thickness of the substrate 2 is not particularly limited and can be appropriately changed depending on the application. The substrate 2 may have through holes.

[0025] [Coating Layer] In this embodiment, the coating layer 3 is laminated directly on the surface of the substrate 2. The coating layer 3 may be a coating layer. When the coating layer 3 is a coating layer, it becomes easy to control the accuracy of the surface roughness of the coating layer 3 and the average thickness of the coating layer 3.

[0026] The coating layer 3 contains an engineering plastic with a pencil hardness of 3H or higher, a solid lubricant, and a silicon compound. By including an engineering plastic with a pencil hardness of 3H or higher in the coating layer 3, the hardness of the coating layer 3 can be increased. This improves the abrasion resistance of the coating layer 3 during sliding, allowing it to be used as a sliding member that can withstand long-term use. Furthermore, when the coating layer 3 contains a solid lubricant, and the solid lubricant is polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkoxyethylene copolymer, molybdenum disulfide, graphite, tetrafluoroethylene-hexafluoropropylene copolymer, ultra-high molecular weight polyethylene, or a combination thereof, the wear resistance of the sliding member 1 is improved. Furthermore, by including a silicon compound in the coating layer 3, the surface tension of the resin composition for the coating layer that forms the coating layer 3 is significantly reduced, improving coatability. This improves the surface properties of the coating layer 3, thereby improving the slipperiness of the coating layer 3 and thereby increasing wear resistance.

[0027] The coating layer 3 does not need to cover the entire surface of the substrate 2, but only needs to cover at least the sliding surface of the substrate 2. For example, as shown in Fig. 1, the coating layer 3 may cover only the first surface of the substrate 2, or may cover both the first and second surfaces of the substrate 2. Furthermore, it is not necessary to cover the entire sliding surface of the substrate 2, but only a part of the sliding surface may be covered. Furthermore, the sliding surface of the coating layer 3 does not need to be flat, and a pattern such as grooves or dimples (recesses) may be formed on the surface.

[0028] The lower limit of the average thickness of the coating layer 3 may be 3.0 μm or 4.0 μm. When the average thickness of the coating layer 3 is 3.0 μm or more, thickness unevenness of the coating layer is reduced while maintaining a thickness that can improve wear resistance, and the surface properties and wear resistance of the coating layer in the sliding member can be further improved. On the other hand, the upper limit of the average thickness may be 60.0 μm, 50.0 μm, or 40.0 μm. When the average thickness is 60.0 μm or less, the adhesion between the base 2 and the coating layer 3 is less likely to decrease.

[0029] When the average thickness of the coating layer 3 is within the above range, the upper limit of the thickness tolerance of the coating layer 3 may be 20%, 15%, or 10% of the average thickness of the coating layer 3. By having the thickness tolerance of the coating layer 3 be 20% or less of the average thickness of the coating layer 3, it is possible to reduce thickness unevenness of the coating layer 3 while maintaining a thickness that can improve the abrasion resistance of the coating layer 3, and to further improve the surface quality and wear resistance of the coating layer 3 in the sliding member 1. The "thickness tolerance" refers to the difference between the maximum and minimum thickness measurements measured at any of the ten points above.

[0030] The flatness of the surface of the coating layer 3 may be 0.005 or less. In the sliding member 1, when the flatness of the surface of the coating layer 3 is 0.005 or less, the lubricity of the surface of the coating layer 3 is improved, and the surface properties and wear resistance of the coating layer 3 in the sliding member 1 can be further improved. The unit of flatness is mm. The flatness of the surface of the coating layer 3 may be adjusted by polishing the coating film of the coating layer 3, which will be described later.

[0031] (Engineering plastics with pencil hardness of 3H or more) The lower limit of the pencil hardness of the engineering plastics may be 3H or 4H. When the pencil hardness of the coating layer 3 is 3H or more, the surface properties of the coating layer 3 can be further improved, and the wear resistance can be increased. Furthermore, when the pencil hardness of the engineering plastics in the sliding member 1 is 3H or more, the coating layer 3 has sufficient hardness, and therefore the entrapment of foreign matter can be further reduced.

[0032] Examples of engineering plastics having a pencil hardness of 3H or more include polyimide, polyamideimide, and polybenzimidazole. Among these, the engineering plastic may be polyimide or polyamideimide from the viewpoint of further improving surface properties and abrasion resistance.

[0033] The coating layer 3 may contain a resin other than the above-mentioned engineering plastics. Examples of the other resin include thermosetting resins such as polyvinyl formal, polyurethane, alkyl resin, epoxy resin, phenoxy resin, polyester, polyesterimide, polyesteramideimide, and polyamideimide, and thermoplastic resins such as polyetherimide, polyetheretherketone, and polyethersulfone.

[0034] The lower limit of the content of the engineering plastic in the coating layer 3 may be 55 mass %, 60 mass %, or 70 mass %. When the content of the engineering plastic is 55 mass % or more, sufficient hardness can be obtained in the coating layer 3. On the other hand, the upper limit of the content of the engineering plastic in the coating layer 3 may be 95 mass %, 90 mass %, or 85 mass %. When the content of the engineering plastic is 95 mass % or less, a sufficient content of the solid lubricant can be maintained and good wear resistance can be obtained.

[0035] <Polyimide> The polyimide is a polymer having an imide bond (-CONCO-) in the main chain. Polyimide has excellent heat resistance and high toughness. Polyimide is a polymer of an aromatic tetracarboxylic dianhydride and an aromatic diamine. In other words, polyimide is a polymer having a structure in which structural units derived from an aromatic tetracarboxylic dianhydride and structural units derived from an aromatic diamine are repeatedly bonded. Here, the term "acid dianhydride" refers to a compound having a structure in which two water molecules are eliminated from four carboxylic acid groups contained in the molecule (a structure in which the molecule contains two carboxylic acid group pairs each consisting of two adjacent carboxylic acid groups, and one water molecule is eliminated from each carboxylic acid group pair).

[0036] The polyimide is formed by curing the polyimide precursor by heating the resin composition for the coating layer to form the coating layer 3. That is, the polyimide precursor undergoes a dehydration cycloreaction (imidization reaction) to form a cyclic imide, thereby becoming a polyimide. The polyimide precursor is a reaction product obtained by a polycondensation reaction between an aromatic tetracarboxylic dianhydride and an aromatic diamine. The polyimide precursor is a compound also known as a polyamic acid (polyamic acid).

[0037] When the aromatic tetracarboxylic dianhydride contains pyromellitic dianhydride (PMDA), the heat resistance of the coating layer 3 can be improved. This is because PMDA has a rigid and linear molecular structure. The aromatic tetracarboxylic dianhydride may contain an aromatic tetracarboxylic dianhydride other than PMDA (hereinafter, also referred to as "another aromatic tetracarboxylic dianhydride").

[0038] Examples of the other aromatic tetracarboxylic dianhydrides include 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA), 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA), 2,2',3,3'-biphenyltetracarboxylic dianhydride (i-BPDA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 4,4'-oxydiphthalic dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, and 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride. Examples of the other aromatic tetracarboxylic dianhydrides include bis(2,3-dicarboxyphenyl)propane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, bis(3,4-dicarboxyphenyl)ether dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, and 2,3,6,7-naphthalenetetracarboxylic dianhydride. These other aromatic tetracarboxylic dianhydrides may be used alone or in combination of two or more.

[0039] When the other aromatic tetracarboxylic dianhydride is biphenyltetracarboxylic dianhydride (BPDA), the hydrolysis resistance of the polyimide precursor can be improved.

[0040] The lower limit of the amount of PMDA relative to 100 mol% of the aromatic tetracarboxylic dianhydride may be 10 mol%, 20 mol%, or 30 mol%, and the upper limit of the amount of PMDA relative to 100 mol% of the aromatic tetracarboxylic dianhydride may be 100 mol%, 90 mol%, 80 mol%, or 70 mol%.

[0041] The content of the other aromatic tetracarboxylic dianhydride relative to 100 mol% of the aromatic tetracarboxylic dianhydride can be appropriately determined within a range that does not impair the effects of the present disclosure. The upper limit of the content may be 30 mol% or 20 mol%. The lower limit of the content may be 0 mol% or 10 mol%.

[0042] When the aromatic diamine contains diaminodiphenyl ether (ODA), the heat resistance of the coating layer 3 can be improved. This is because ODA has a rigid and linear molecular structure. Examples of diaminodiphenyl ethers include 4,4'-diaminodiphenyl ether (4,4'-ODA), 3,4'-diaminodiphenyl ether (3,4'-ODA), 3,3'-diaminodiphenyl ether (3,3'-ODA), 2,4'-diaminodiphenyl ether (2,4'-ODA), and 2,2'-diaminodiphenyl ether (2,2'-ODA). 4,4'-diaminodiphenyl ether (4,4'-ODA) can improve the film elongation of the coating layer 3.

[0043] The lower limit of the ODA content relative to 100 mol% of the aromatic diamine may be 50 mol%, 60 mol%, or 70 mol%, and the upper limit of the ODA content relative to 100 mol% of the aromatic diamine may be 100 mol% or 90 mol%.

[0044] The aromatic diamine may further contain an aromatic diamine other than ODA (hereinafter also referred to as "other aromatic diamine"). Examples of the other aromatic diamine include 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 4,4'-bis(4-aminophenoxy)biphenyl (BAPB), 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 2,4'-diaminodiphenylmethane, 2,2'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 3,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, 2,4'-diaminodiphenylsulfone, 2,2'-diaminodiphenylsulfone, 4,4' Examples of the other aromatic diamines include 4,4'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 2,4'-diaminodiphenyl sulfide, 2,2'-diaminodiphenyl sulfide, paraphenylenediamine, metaphenylenediamine, p-xylylenediamine, m-xylylenediamine, 2,2'-dimethyl-4,4'-diaminobiphenyl (mTBHG), 1,5-diaminonaphthalene, 4,4'-benzophenonediamine, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, and 3,3',5,5'-tetramethyl-4,4'-diaminodiphenylmethane. The other aromatic diamines may be used alone or in combination of two or more.

[0045] The content of the other aromatic diamine relative to 100 mol% of the aromatic diamine can be appropriately determined within a range that does not impair the effects of the present disclosure. The upper limit of the content may be 40 mol% or 30 mol%. The lower limit of the content may be 0 mol% or 10 mol%.

[0046] The molar ratio of the aromatic tetracarboxylic dianhydride to the aromatic diamine used as raw materials for the polyimide precursor (aromatic tetracarboxylic dianhydride:aromatic diamine) may be, for example, 95:105 or more and 105:95 or less, 97:103 or more and 103:97 or less, or 99:101 or more and 101:99 or less, from the viewpoint of ease of synthesis of the polyimide precursor. The aromatic tetracarboxylic dianhydride and the aromatic diamine may be substantially equimolar amounts. In this case, the molecular weight of the polyimide precursor can be easily increased. The term "substantially equimolar amount" refers to a molar ratio of the aromatic tetracarboxylic dianhydride to the aromatic diamine (aromatic tetracarboxylic dianhydride:aromatic diamine) in the range of 99:101 or more and 101:99 or less.

[0047] <Polyamideimide> Polyamideimide is a resin having an amide bond and an imide bond in the molecule, and can be obtained, for example, by polymerizing a diisocyanate compound with an acid component.

[0048] Examples of the diisocyanate compound include aromatic diisocyanate compounds such as diphenylmethane-4,4'-diisocyanate (MDI), diphenylmethane-3,3'-diisocyanate, diphenylmethane-3,4'-diisocyanate, diphenylether-4,4'-diisocyanate, benzophenone-4,4'-diisocyanate, diphenylsulfone-4,4'-diisocyanate, etc. The diisocyanate compounds can be used alone or in combination of two or more.

[0049] Examples of the acid component include trimellitic anhydride (TMA), 1,2,5-trimellitic acid (1,2,5-ETM), biphenyltetracarboxylic dianhydride, benzophenonetetracarboxylic dianhydride, diphenylsulfonetetracarboxylic dianhydride, oxydiphthalic dianhydride (OPDA), pyromellitic dianhydride (PMDA), and 4,4'-(2,2'-hexafluoroisopropylidene)diphthalic dianhydride. The acid components can be used alone or in combination of two or more.

[0050] <Polybenzimidazole> Polybenzimidazole can be obtained by polymerizing a tetraamine with a dicarboxylic acid, which is an acid component, or the corresponding dicarboxylic acid chloride or dicarboxylic acid activated ester. In general, polybenzimidazole can be obtained by dehydrating and cyclizing a polyaminoamide, which is one of polybenzimidazole precursors obtained by reacting a bisaminophenol compound with a dicarboxylic acid, through heating or a chemical treatment with phosphoric anhydride, a base, a carbodiimide compound, or the like.

[0051] (Solid Lubricant) The coating layer 3 contains a solid lubricant. When the coating layer 3 contains a solid lubricant, the wear resistance of the sliding member 1 is improved. The solid lubricant is polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkoxyethylene copolymer, molybdenum disulfide, graphite, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), ultra-high molecular weight polyethylene, or a combination thereof. Among these, polytetrafluoroethylene and tetrafluoroethylene-perfluoroalkoxyethylene copolymer can exhibit superior wear resistance.

[0052] The lower limit of the content of the solid lubricant in the coating layer 3 may be 5 vol%, 10 vol%, or 15 vol%. When the content of the solid lubricant is 5 vol% or more, the surface properties and wear resistance of the coating layer 3 are improved. On the other hand, the upper limit of the content of the solid lubricant may be 30 vol% or 25 vol%. When the content of the solid lubricant is 30 vol% or less, the hardness of the coating layer 3 can be improved and the wear resistance can be improved.

[0053] The lower limit of the average particle size of the solid lubricant may be 0.1 μm or 0.2 μm. When the average particle size of the solid lubricant is 0.1 μm or more, the coating layer 3 is less likely to soften, and deterioration of wear resistance and inclusion of foreign matter can be further reduced. On the other hand, the upper limit of the average particle size of the solid lubricant may be 10.0 μm or 9.0 μm. When the average particle size of the solid lubricant is 10.0 μm or less, the surface roughness of the coating layer 3 is further reduced, and the amount of wear and torque of the coating layer 3 are less likely to increase. The "average particle size" refers to the median diameter (D50), which is the value at which the volume-based cumulative distribution calculated in accordance with JIS-Z-8819-2:2001 is 50%. Specifically, the median diameter (D50) can be measured using the following method. Measurement is performed using a laser diffraction particle size distribution analyzer. A scattering measurement mode is adopted, and a laser beam is irradiated onto a wet cell in which a dispersion liquid in which particles of the sample to be measured are dispersed in a dispersion solvent is circulated, and a scattered light distribution is obtained from the measured sample. The scattered light distribution is then approximated by a log-normal distribution, and the particle diameter at a cumulative degree of 50% (D50) is taken as the median diameter.

[0054] (Silicon Compound) The coating layer 3 contains a silicon compound. By containing a silicon compound as an additive in the coating layer 3, the surface properties of the coating layer 3 are improved. This improves the slipperiness of the coating layer 3, and the abrasion resistance of the coating layer 3 can be increased.

[0055] The silicon compound may be modified polydimethylsiloxane. Modified polydimethylsiloxane has a structure in which a substituent is introduced into a portion of a silicone having a siloxane bond as its main skeleton. When the coating layer 3 contains modified polydimethylsiloxane as an additive, the surface tension of the resin composition for the coating layer that forms the coating layer 3 is significantly reduced, effectively acting as a leveling agent during application and improving film thickness accuracy. This improves the surface properties of the coating layer 3, further improving the slipperiness of the coating layer 3 and thereby increasing abrasion resistance. Furthermore, thixotropy suitable for application of the resin composition for the coating layer can be imparted.

[0056] The modified polydimethylsiloxane may be either a linear modified polydimethylsiloxane or a cyclic modified polydimethylsiloxane. A mixture of a linear modified polydimethylsiloxane and a cyclic modified polydimethylsiloxane may also be used. A mixture of modified polydimethylsiloxanes with different molecular weights may also be used. Examples of modified polydimethylsiloxanes include modified polydimethylsiloxanes having a structure substituted with hydroxyl groups, amino groups, (poly)ether groups, epoxy groups, carboxy groups, carbinol groups, mercapto groups, phenol groups, ester groups, alkoxy groups, halogen atoms, aralkyl groups, aralkyl groups, long-chain alkyl groups, higher fatty acid ester-modified, higher aliphatic amide groups, etc. Specific examples of modified polydimethylsiloxanes include polyether-modified polydimethylsiloxanes, polyester-modified polydimethylsiloxanes, hydroxyl-containing polyester-modified polydimethylsiloxanes, polyarakyl-modified polydimethylsiloxanes, and epoxy-functional polyether-modified polydimethylsiloxanes. Among these, the modified polydimethylsiloxane may be a polyether-modified polydimethylsiloxane having a polyether-modifying group, from the viewpoint of the effect of reducing surface tension.

[0057] The lower limit of the content of the silicon compound in the coating layer 3 is 0.01% by mass, or may be 0.02% by mass, or may be 0.03% by mass. When the content of the silicon compound is 0.01% by mass or more, the surface properties and abrasion resistance of the coating layer 3 can be improved. On the other hand, the upper limit of the content of the silicon compound is less than 10% by mass, or may be 9% by mass, or may be 8% by mass. When the content of the silicon compound is less than 10% by mass, the hardness and surface properties of the coating layer 3 can be improved.

[0058] If necessary, the coating layer 3 may contain additives other than the silicon compound, such as anti-settling agents, dispersants, anti-foaming agents, coloring pigments, antioxidants, ultraviolet absorbers, antistatic agents, and surfactants.

[0059] [Method for Manufacturing Sliding Member] A method for manufacturing the sliding member according to one embodiment includes a step of directly or indirectly laminating a coating layer containing an engineering plastic having a pencil hardness of 3H or more, a solid lubricant, and a silicon compound on at least a part of the surface of a substrate.

[0060] In this step, a coating layer containing an engineering plastic having a pencil hardness of 3H or more, a solid lubricant, and a silicon compound is directly or indirectly laminated onto at least a portion of the surface of the substrate. Examples of the silicon compound include modified polydimethylsiloxane.

[0061] Examples of the lamination method include precision coating with an air spray, a roll coater, a bar coater, a doctor blade, an ink jet, a dispenser, dip coating, and screen printing, which are methods for applying the coating material to the surface of the substrate.

[0062] Examples of the coating material include a coating material in which a resin composition for a coating layer containing a polyimide precursor, a polyamideimide precursor, or a polybenzimidazole precursor, a solid lubricant, and a silicon compound is dispersed or dissolved in a solvent. Examples of the solvent include amide-based solvents such as N-methylpyrrolidone, 2-pyrrolidone, dimethylacetamide, N,N-dimethylformamide, and N,N-diethylformamide, as well as mixtures of the amide-based solvents with other solvents such as water, alcohols, ketones, ethers, esters, amines, and combinations thereof. The coating material can be prepared by mechanically stirring and mixing a resin composition for a coating layer, which contains predetermined amounts of the polyimide precursor, solid lubricant, and silicon compound, in the solvent.

[0063] The lower limit of the solids concentration of the coating material may be 2 mass%, 25 mass%, or 40 mass%, while the upper limit of the solids concentration of the coating material may be 60 mass%, 50 mass%, or 45 mass%. By setting the solids concentration of the coating material within the above range, coatability can be improved, and as a result, a coating film with few coating defects can be easily and reliably formed.

[0064] Next, a coating material is applied to the surface of the substrate on which the coating layer will be laminated using a bar coater. The inclusion of a silicon compound in the coating material improves coating properties. When the silicon compound is a modified polydimethylsiloxane, leaving the coating for 5 minutes after application causes the coating film to level, become smoother, and improve film thickness precision.

[0065] After coating the surface of the substrate with a coating material, the substrate is placed in a heating furnace and heated to bake the layer-shaped resin composition for the coating layer. This baking process removes the solvent from the coating material and forms a coating layer. The heating temperature for baking the coating film of the resin composition for the coating layer can be, for example, 350°C or higher and 400°C or lower. The heating time for baking the coating film can be, for example, 5 minutes or higher and 60 minutes or lower. By maintaining the heating temperature and heating time within the above ranges, a film with excellent density can be formed while suppressing resin decomposition. The surface of the coating film may be polished after cooling the substrate. Polishing the surface of the coating film can improve the surface properties of the coating layer, the flatness and parallelism of the coating layer surface, and the perpendicularity between the side surface and the surface of the coating layer. Because the coating layer of the sliding member has good flatness and parallelism even before polishing, it can be polished to a high-precision shape with a flatness of 0.005 or less and a parallelism of 0.005 or less at low cost. In this way, a coating layer is laminated on the surface of the substrate. Details of other components in the slide member obtained by the above-mentioned method for producing a slide member are as described above.

[0066] In order to improve the adhesion between the substrate and the coating film, the surface of the substrate may be subjected to a surface treatment or roughening treatment such as sandblasting, shot peening, etching, zinc phosphate treatment, zinc calcium phosphate treatment, manganese phosphate treatment, nickel plating, zinc plating, other plating, or roughening treatment by sanding.

[0067] As described above, the coating layer does not need to be laminated on the entire surface of the substrate, but it is sufficient that it is laminated at least on the sliding surface of the substrate.

[0068] The sliding member has excellent surface properties and wear resistance, and is therefore suitable for use as a sliding member for rotor-type or swing-type compressors such as vanes, shoes, side plates, and pistons, as well as for rotary devices such as oil pump rotors, and as a sliding member provided in devices that move in a plane such as dies.

[0069] [Other Embodiments] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is not limited to the configurations of the above-described embodiments, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0070] In the sliding member, when at least a portion of the corners of the base body has a chamfered portion, the coating layer may be laminated in a region of the surface of the base body that includes the chamfered portion. When the base body has a chamfered portion, the chamfered portion is easily pressed by other components and easily wears. However, by laminating a coating layer in a peripheral region including the chamfered portion of the base body, the sliding member can improve durability until the chamfered portion of the base body and the coating layer laminated in its vicinity wears away and the surface of the base body is exposed. Thus, in the sliding member, when at least a portion of the corners of the base body has a chamfered portion, the effects of the present disclosure can be more effectively achieved. Note that the shape of the chamfered portion is not particularly limited.

[0071] FIG. 2 is a schematic cross-sectional view showing a slide member 10 according to another embodiment. As shown in FIG. 2 , the slide member 10 includes a base 12 having a first surface and a second surface facing each other, and a coating layer 13 coating the first surface 14 of the base 12. The base 12 also has chamfered portions 15 and 16 at both ends of the first surface 14. The coating layer 13 is laminated on the surface of the base 12 in a region including the chamfered portions 15 and 16, making it difficult for the first surface 14, the chamfered portions 15 and 16, and their neighboring regions to be exposed. This reduces wear of the slide member 10. Furthermore, the coating layer 13 is laminated on the first surface 14 as well as the chamfered portions 15 and 16 in the slide member 10, thereby further reducing oil leakage and improving volumetric efficiency when the slide member 10 is used in an oil pump or compressor.

[0072] In the above embodiment, the coating layer is laminated only on the first surface (one side) of the substrate. However, the coating layer may be laminated directly or indirectly on the first and second surfaces (both surfaces) of the substrate, which face each other. FIG. 3 is a schematic cross-sectional view showing a slide member 20 according to another embodiment. As shown in FIG. 3 , the slide member 20 includes a substrate 2 having a first and second surface, which face each other, a coating layer 3 laminated directly on the first surface of the substrate 2, and a coating layer 23 laminated directly on the second surface of the substrate 2. By including the coating layer 3 laminated directly on the first surface of the substrate 2 and the coating layer 23 laminated directly on the second surface of the substrate 2, the slide member 20 can improve the smoothness and wear resistance of the first and second surfaces of the substrate 2. When the coating layer 3 and the coating layer 23 are laminated facing each other on the first and second surfaces (both surfaces) of the substrate 2, the parallelism of the facing coating layer 3 and the coating layer 23 may be 0.005 or less. In the sliding member 20, when the parallelism of the opposing coating layers 3 and 23 is 0.005 or less, the sliding properties of the surfaces of the coating layers 3 and 23 are improved, and the smoothness and wear resistance of the coating layers 3 and 23 in the sliding member 20 can be further increased. The unit of parallelism is mm. The parallelism of the surfaces of the coating layers 3 and 23 may be adjusted by polishing the coating films of the coating layers 3 and 23.

[0073] In the above embodiment, the coating layer is laminated directly on the surface of the substrate, but an intermediate layer may be further provided between the substrate and the coating layer. By providing the sliding member with an intermediate layer, the hardness of the coating layer can be further increased. An example of the intermediate layer is a resin layer mainly composed of an engineering plastic having a pencil hardness of 3H or more.

[0074] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to the following examples.

[0075] <Sliding Members No. 1 to No. 48> [No. 1 to No. 48] A stainless steel (SUS430) plate measuring 40 mm in length, 40 mm in width, and 5 mm in average thickness was used as the substrate. A coating layer containing an engineering plastic, a solid lubricant, and a silicon compound listed in Tables 1 to 3 was directly laminated on the plate using the following procedure. First, the solid lubricant and silicon compound listed in Tables 1 to 3 were added to the engineering plastic listed in Tables 1 to 3 in the amounts listed in Tables 1 to 3. The engineering plastic was blended so that the total content of the solid lubricant and silicon compound in the coating layer was 100% by mass, and the solid lubricant and silicon compound contents were as listed in Tables 1 to 3. The mixture was then stirred for 3 hours at 1200 rpm using a magnetic stirrer. Table 3 shows the results when different types of solid lubricants were used, with the contents shown in mass % and volume %. Next, the prepared coating material was dropped onto the surface of the substrate and coated using AS ONE Corporation's "Non-wire bar coater OSP-05-L60" so that the dry film thickness would be the average thickness shown in Tables 1 to 3. After drying at 100°C for 10 minutes, the coating material was baked at 360°C for 15 minutes to prepare test specimens.

[0076] The materials used are as follows: (Engineering plastics) (1) Polyimide 1 (PI) "UPIA-AT-1001" manufactured by UBE, glass transition temperature 274°C to 278°C (2) Polyamideimide (PAI) "Vylomax HR-11NN" manufactured by Toyobo, glass transition temperature 300°C (Silicon compound) Modified polydimethylsiloxane: "BYK-306" manufactured by BKY (Solid lubricant) (1) Molybdenum disulfide (MoS ２ ) "T Powder" manufactured by Daizo Co., Ltd., average particle size 3.5 μm (2) Polytetrafluoroethylene 1 (PTFE1) "L5" manufactured by Daikin Industries, Ltd., average particle size 5.0 μm (3) Tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA) "EA-2000 PW10" manufactured by AGC Inc., average particle size 2.0 μm (4) Tetrafluoroethylene-hexafluoropropylene copolymer (FEP) "NCX-11" manufactured by Daikin Industries, Ltd. (5) Graphite "J-CPB" manufactured by Nippon Graphite Industries Co., Ltd.

[0077] <Evaluation> [Wear Resistance: Limiting PV Value in Dry Ring-on-Disk Wear Test] For sliding members No. 1 to No. 46, the limiting PV value [MPa m / min] of the outer surface of the coating layer was measured by ring-on-disk wear testing using the following procedure. After adjusting the temperature at 23±2°C, the load was kept constant at 10 MPa, and the speed was increased step by step to measure the limiting PV value. Specifically, a ring-shaped mating member made of S45C (carbon steel for mechanical structures) with ring dimensions (outer diameter / inner diameter) of φ11.6 mm / φ7.4 mm was used. Then, under dry lubricated conditions, a load of 10 MPa (contact pressure: P) was applied to the mating member, and the test piece was rotated at a predetermined speed (rotational speed: V) to measure the limiting PV value. The speed started at 1 m / min in step (1), increased to 5 m / min in step (2), and increased to 10 m / min in step (3). Thereafter, the speed was increased by 10 m / min for each step up to step (10). From step (11) onwards, the speed was increased by 10 m / min for each step up, and the PV value was measured. In the present disclosure, the PV value just before the substrate was exposed was defined as the limit PV value. For the above measurements, an "EFM-3-1010-S" test device manufactured by AND was used.

[0078] [Surface Properties (Slipperiness): Travel Distance in Dry Ring-on-Disk Abrasion Test] The cumulative travel distance [m] until the limit PV value was reached in the dry ring-on-disk abrasion test was measured, and the surface properties (slipperiness) were evaluated. The cumulative travel distances of the sliding members No. 1 to No. 46 were evaluated according to the following three levels, and those with an evaluation of A or B were judged to pass. A: Cumulative travel distance exceeds 1000 m B: Cumulative travel distance exceeds 700 m and is 1000 m or less C: Cumulative travel distance is 700 m or less

[0079] [Adhesion Strength Between Substrate and Coating Layer] The adhesion strength [N / mm] between the substrate and the coating layer was measured by a surface-interface cutting method according to the following procedure. The peel strength at the interface between the substrate and the coating layer can be measured using a SAICAS (Surface and Interfacial Cutting Analysis System). The surface-interface cutting method is a method for measuring shear strength and peel strength by using a sharp cutting blade to cut at an ultra-low speed from the sample surface to the adhesive interface between the substrate and the adherend, or by moving the cutting blade horizontally near the adhesive interface. Specifically, a SAICAS-NN model manufactured by Daipla Wintes was used in constant speed mode (vertical speed 0.2 μm / sec and horizontal speed 2 μm / sec), and a 1 mm wide cutting blade (rake angle 20 degrees, relief angle 10 degrees) was used to measure the horizontal load while cutting parallel to the interface between the substrate and the coating layer on a 1 mm wide sample, and the peel strength between the substrate and the coating layer was determined.

[0080]

[0081]

[0082]

[0083] As shown in Tables 1 to 3, samples Nos. 3 to 6, 10, 12, 14 to 30, and 34 to 46, in which the coating layer contained an engineering plastic with a pencil hardness of 3H or higher, a solid lubricant, and a silicon compound, the solid lubricant being polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkoxyethylene copolymer, molybdenum disulfide, graphite, tetrafluoroethylene-hexafluoropropylene copolymer, ultra-high molecular weight polyethylene, or a combination thereof, and the content of the silicon compound in the coating layer was 0.01% by mass or more but less than 10% by mass, exhibited favorable results in terms of limit PV value and cumulative travel distance. Furthermore, as shown in Nos. 31 and 32, the adhesion between the substrate and the coating layer was also favorable. Note that a decrease in adhesion was observed when the average thickness of the coating layer was increased to 70 μm.

[0084] On the other hand, samples No. 1, No. 9, No. 11, and No. 13, which did not contain silicon compounds, and No. 2, which contained less than 0.01% by mass of silicon compounds, had low PV limit values ​​and cumulative travel distances. Samples No. 7 and No. 8, which contained 10% or more by mass of silicon compounds, also had low PV limit values ​​and cumulative travel distances.

[0085] As a result, it was shown that the sliding member had excellent surface properties and wear resistance.

[0086] 1, 10, 20 Sliding member 2, 12 Base body 3, 13, 23 Coating layer 14 First surface 15, 16 Chamfered portion

Claims

1. A sliding member comprising: a substrate; and a coating layer laminated directly or indirectly on at least a portion of the surface of the substrate, wherein the coating layer contains an engineering plastic having a pencil hardness of 3H or more, a solid lubricant, and a silicon compound, wherein the solid lubricant is polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkoxyethylene copolymer, molybdenum disulfide, graphite, tetrafluoroethylene-hexafluoropropylene copolymer, ultra-high molecular weight polyethylene, or a combination thereof, and wherein the silicon compound content in the coating layer is 0.01% by mass or more but less than 10% by mass.

2. The sliding member according to claim 1, wherein the coating layer has an average thickness of 3.0 μm or more.

3. A sliding member according to claim 1 or 2, wherein the flatness of the surface of said coating layer is 0.005 or less.

4. A sliding member according to any one of claims 1 to 3, wherein the engineering plastic is polyimide or polyamideimide, and the silicon compound is modified polydimethylsiloxane.

5. A sliding member according to any one of claims 1 to 4, wherein the substrate is a sintered metal body.

6. A sliding member according to any one of claims 1 to 5, wherein at least some of the corners of the base have chamfered portions, and the coating layer is laminated on an area of the surface of the base that includes the chamfered portions.

7. A sliding member according to any one of claims 1 to 6, wherein the base has a shape having a first surface and a second surface facing each other, and the coating layer is laminated directly or indirectly on the first surface and the second surface of the base.

8. The sliding member according to claim 7, wherein the parallelism of the coating layer on the first and second surfaces of the substrate is 0.005 or less.

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