WO2023053380A1 - 摺動部材 - Google Patents
摺動部材 Download PDFInfo
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- WO2023053380A1 WO2023053380A1 PCT/JP2021/036227 JP2021036227W WO2023053380A1 WO 2023053380 A1 WO2023053380 A1 WO 2023053380A1 JP 2021036227 W JP2021036227 W JP 2021036227W WO 2023053380 A1 WO2023053380 A1 WO 2023053380A1
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- dlc coating
- sliding member
- plast
- test
- dlc
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- 238000000576 coating method Methods 0.000 claims abstract description 63
- 239000011248 coating agent Substances 0.000 claims abstract description 58
- 238000012360 testing method Methods 0.000 claims abstract description 49
- 230000002093 peripheral effect Effects 0.000 claims abstract description 13
- 229910052739 hydrogen Inorganic materials 0.000 claims description 6
- 239000001257 hydrogen Substances 0.000 claims description 6
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 4
- 238000011161 development Methods 0.000 abstract description 7
- 208000013201 Stress fracture Diseases 0.000 abstract description 6
- 239000000463 material Substances 0.000 description 18
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 11
- 238000007373 indentation Methods 0.000 description 10
- 229910052799 carbon Inorganic materials 0.000 description 9
- 238000002485 combustion reaction Methods 0.000 description 9
- 238000000034 method Methods 0.000 description 8
- 230000000052 comparative effect Effects 0.000 description 7
- 230000018109 developmental process Effects 0.000 description 6
- 230000005489 elastic deformation Effects 0.000 description 6
- 239000003921 oil Substances 0.000 description 6
- 239000010802 sludge Substances 0.000 description 6
- 238000005259 measurement Methods 0.000 description 5
- 230000003746 surface roughness Effects 0.000 description 4
- 229910021385 hard carbon Inorganic materials 0.000 description 3
- 238000001000 micrograph Methods 0.000 description 3
- 239000000758 substrate Substances 0.000 description 3
- 229910000838 Al alloy Inorganic materials 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 229910001018 Cast iron Inorganic materials 0.000 description 2
- 125000004432 carbon atom Chemical group C* 0.000 description 2
- 229910003460 diamond Inorganic materials 0.000 description 2
- 239000010432 diamond Substances 0.000 description 2
- 238000009499 grossing Methods 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 150000002431 hydrogen Chemical class 0.000 description 2
- 239000010687 lubricating oil Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 229910001105 martensitic stainless steel Inorganic materials 0.000 description 2
- 229910001220 stainless steel Inorganic materials 0.000 description 2
- 230000000007 visual effect Effects 0.000 description 2
- 208000010392 Bone Fractures Diseases 0.000 description 1
- 206010017076 Fracture Diseases 0.000 description 1
- 229910000639 Spring steel Inorganic materials 0.000 description 1
- 238000005299 abrasion Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000011651 chromium Substances 0.000 description 1
- DYRBFMPPJATHRF-UHFFFAOYSA-N chromium silicon Chemical compound [Si].[Cr] DYRBFMPPJATHRF-UHFFFAOYSA-N 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 229910001651 emery Inorganic materials 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 125000006850 spacer group Chemical group 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
Images
Classifications
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
- C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
- C23C14/0605—Carbon
- C23C14/0611—Diamond
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
- C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
- C23C14/0605—Carbon
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
- C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
- C23C14/24—Vacuum evaporation
- C23C14/32—Vacuum evaporation by explosion; by evaporation and subsequent ionisation of the vapours, e.g. ion-plating
- C23C14/325—Electric arc evaporation
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
- C23C28/04—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings of inorganic non-metallic material
- C23C28/046—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings of inorganic non-metallic material with at least one amorphous inorganic material layer, e.g. DLC, a-C:H, a-C:Me, the layer being doped or not
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
- C23C28/30—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer
- C23C28/34—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one inorganic non-metallic material layer, e.g. metal carbide, nitride, boride, silicide layer and their mixtures, enamels, phosphates and sulphates
- C23C28/343—Coatings combining at least one metallic layer and at least one inorganic non-metallic layer including at least one inorganic non-metallic material layer, e.g. metal carbide, nitride, boride, silicide layer and their mixtures, enamels, phosphates and sulphates with at least one DLC or an amorphous carbon based layer, the layer being doped or not
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
- F02F5/00—Piston rings, e.g. associated with piston crown
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16J—PISTONS; CYLINDERS; SEALINGS
- F16J9/00—Piston-rings, e.g. non-metallic piston-rings, seats therefor; Ring sealings of similar construction
- F16J9/26—Piston-rings, e.g. non-metallic piston-rings, seats therefor; Ring sealings of similar construction characterised by the use of particular materials
Definitions
- the present invention relates to sliding members that are mainly used in internal combustion engines.
- a DLC (diamond-like carbon) film is an amorphous structure (amorphous structure) film in which sp 2 bonds of carbon atoms corresponding to a graphite structure and sp 3 bonds of carbon atoms corresponding to a diamond structure are mixed. By adjusting the ratio of both binding components, DLC coatings with different properties can be formed.
- DLC coatings which have excellent wear resistance and sliding properties, are used as sliding members for internal combustion engines, which have a severe sliding environment.
- Sliding members for internal combustion engines include piston rings, cylinder liners, camshafts, and the like.
- Patent Document 1 discloses that the wear amount of the DLC coating can be reduced when the ratio Wp/We of the elastic deformation energy We to the plastic deformation energy Wp of the DLC coating is 0.60 or more.
- Patent Document 2 in a combination of an aluminum alloy cylinder of an internal combustion engine and a piston ring that slides on the inner peripheral surface of the cylinder, only hydrogen and carbon coated on the outer peripheral surface of the piston ring, or hydrogen, carbon and nitrogen
- Wp/We of the elastic deformation energy We to the plastic deformation energy Wp of the DLC coating formed by disclosed In a combination of an aluminum alloy cylinder of an internal combustion engine and a piston ring that slides on the inner peripheral surface of the cylinder, only hydrogen and carbon coated on the outer peripheral surface of the piston ring, or hydrogen, carbon and nitrogen
- the present inventors are aware of the fact that the DLC coating of the DLC-coated sliding member may wear out due to insufficient wear resistance. That is, the conventionally disclosed sliding member having a DLC coating has a problem that the wear resistance (abrasive wear resistance) is not sufficient when foreign matter such as carbon sludge is mixed. Sliding with foreign matter such as carbon sludge intervening may cause fine cracks on the sliding surface of the DLC coating.
- the present invention has been made in view of the above problems, and provides a sliding member that has wear resistance (abrasive wear resistance) even in an environment where foreign matter such as carbon sludge is present.
- the present inventors have made extensive studies to solve the above problems, and have found that a sliding member having a DLC coating on its outer peripheral sliding surface, which has a specific range of plastic deformation work measured by a nanoindentation test, is the above problem. can be solved, and completed the present invention. Specifically, the inventors have found that the toughness of the DLC coating is improved and the wear resistance of the DLC coating is improved by increasing the work of plastic deformation measured by the nanoindentation test.
- the present invention relates to a sliding member having a DLC coating on its outer peripheral sliding surface
- the DLC coating is a sliding member having a plastic deformation work (W plast ) of 5.7 nJ or more as measured by a nanoindentation test under a load of 100 mN.
- the DLC film preferably has a total work (W total ) of 18.1 nJ or more, a plastic deformation work rate ( ⁇ plast ) of 31.3% or more, and a nanoindentation hardness of
- the ratio (HIT/W plast ) of (HIT) to plastic deformation work (W plast ) is preferably 5.3 GPa/nJ or less.
- the DLC coating preferably does not substantially contain hydrogen, and the hydrogen content is preferably 0.5 at % or less, and the sliding member is preferably a piston ring.
- a sliding member coated with a DLC film which is less susceptible to microfracture on the sliding surface due to the development of cracks and can suppress an increase in abrasive wear.
- FIG. 2 shows a schematic cross-sectional view of a piston ring in which a DLC coating having a base layer is formed on a piston ring base material. It is a schematic diagram which shows the outline
- 4 is a laser microscope image showing the results of a Rockwell indentation test on the DLC coating of Example 1 (photograph substituting for drawing). 4 is a laser microscope image showing the results of a Rockwell indentation test on the DLC coating of Comparative Example 1 (photograph substituting for drawing).
- An embodiment of the present invention is a sliding member having a DLC coating on the outer peripheral sliding surface.
- the sliding member may be used in internal combustion engines or may be used in other than internal combustion engines, but it is particularly suitable for use in internal combustion engines.
- Sliding members used in internal combustion engines include piston rings, cylinder liners, camshafts, etc.
- description will be made using a piston ring as a typical example of the sliding member.
- the DLC coating of the sliding member has a work of plastic deformation (W plast ) of 5.7 nJ or more as measured by a nanoindentation test under a load of 100 mN.
- the plastic deformation work (plastic deformation energy) (W plast ) is the amount of work that the indenter pushed from the coating surface in the nanoindentation test spends on deformation of the coating, and the amount of work that the coating remains deformed even when the indenter is unloaded. is the amount of work expended in plastic deformation to the state.
- the elastic deformation work (elastic deformation energy) (W elast ) is the work released when the indenter is unloaded and the film returns to its original state.
- the plastic deformation work rate ( ⁇ plast ) is an index that characterizes a coating that is likely to be plastically deformed when foreign matter is pushed into the coating surface.
- the present inventors have found that when the plastic deformation work (W plast ) measured at a load of 100 mN by a nanoindentation test is 5.7 nJ or more, microfractures occur on the sliding surface due to the development of cracks in the DLC coating. It was found that the increase in abrasive wear can be suppressed. Furthermore, the work of plastic deformation (W plast ) measured by the nanoindentation test is preferably 6.2 nJ or more. Although the upper limit of the plastic deformation work is not particularly limited, it is preferably 8.0 nJ or less.
- the nanoindentation test uses a nanoindentation measuring instrument manufactured by Fisher Instruments, model HM-2000, using a Vickers indenter, an indentation load of 100 mN, a load time of 30 s (seconds) until the maximum indentation load, and a holding time of 5 s. (seconds) and an unloading time of 30 s (seconds).
- the plastic deformation work and elastic deformation work of the DLC film, the nanoindentation hardness, and the Young's modulus described later are calculated using the load-indentation depth curve obtained in the nanoindentation test.
- the measurement value is a total of 4 points at each of 3 positions, the position on the opposite side of the gap of the piston ring and the position 90° on both sides from the gap. An average value of 12 measurements was taken.
- the total work (also referred to as total deformation work, W total ) calculated by the following formula (1) measured by the nanoindentation test is preferably 18.1 nJ or more.
- the upper limit of the total amount of work is not particularly limited, but is preferably 23.0 nJ or less. Satisfying the above range is preferable because microfractures on the sliding surface due to the development of cracks in the DLC coating are less likely to occur, and an increase in abrasive wear can be suppressed.
- W total W plast + W elast (1)
- the plastic deformation power ( ⁇ plast ) calculated by the following formula (2) measured by the nanoindentation test is preferably 31.3% or more, and the plastic deformation power is 32.3%. It is more preferably 4% or more, and even more preferably 33.0% or more.
- the upper limit of the plastic deformation work rate is not particularly limited, it is preferably 38.0% or less. Satisfying the above range is preferable because microfractures on the sliding surface due to the development of cracks in the DLC coating are less likely to occur, and an increase in abrasive wear can be suppressed.
- ⁇ plast ( Wplast / Wtotal ) x 100 (%) (2)
- the ratio (HIT/W plast ) of nanoindentation hardness (HIT) to plastic deformation work (W plast ) measured by the nanoindentation test is preferably 5.3 GPa/nJ or less. , 4.1 GPa/nJ or less.
- the lower limit of the ratio (HIT/W plast ) of nanoindentation hardness (HIT) to plastic deformation work (W plast ) is not particularly limited, it is preferably 2.0 GPa/nJ or more. Satisfying the above range is preferable because microfractures on the sliding surface due to the development of cracks in the DLC coating are less likely to occur, and an increase in abrasive wear can be suppressed.
- the plastic deformation work measured by the nanoindentation test can be adjusted to a desired value by adjusting the manufacturing method of the DLC film. More specifically, when forming a DLC coating using a filtered cathode vacuum arc (FCVA) method, the applied pulse bias voltage is, for example, -500 V to -2500 V, preferably - 700V to -2500V. In addition, a desired value can be obtained by adjusting the substrate temperature, chamber pressure (vacuum degree), arc current, target purity, etc. during the formation of the DLC film.
- FCVA filtered cathode vacuum arc
- a specific embodiment of the present invention will be described below, taking as an example the case where the sliding member is a piston ring.
- a piston ring 10 shown in FIG. 1 is mounted in a piston ring groove (not shown) formed in a piston, and reciprocates while sliding on the inner peripheral surface of a cylinder bore (not shown) by the reciprocating motion of the piston.
- the piston ring 10 may be used as a top ring, a second ring, or an oil ring.
- the oil ring body When applied to an oil ring, the oil ring body of a two-piece configuration oil ring consisting of an oil ring body and a coil expander, and a three-piece configuration consisting of two segments (also called side rails) and an expander spacer. It can be applied to any segment of the oil ring.
- the piston ring is attached to an aluminum alloy piston and used as a piston ring for a cast iron cylinder bore, but the material of the piston and cylinder is not limited to these.
- the material of the piston ring base material 11 is not particularly limited as long as it is a material conventionally used as a piston ring base material.
- stainless steel, spring steel, etc. are preferably used.
- martensitic stainless steel, silicon chromium steel, etc. are preferably used.
- a piston ring 10 shown in FIG. 1 has an underlying layer 13 containing Cr, Ti, Si, or the like on the smoothed outer peripheral surface of a piston ring base material 11, and has a DLC coating 12 thereon.
- the thickness of the underlying layer 13 is preferably 0.2 ⁇ m or more and 2.0 ⁇ m or less. By setting it as such a film thickness, the adhesiveness of the DLC film 12 and the piston ring base material 11 can be improved more.
- the DLC coating 12 may be formed directly on the smoothed outer peripheral surface of the piston ring base material 11 without providing the base layer 13 .
- the method for smoothing the outer peripheral surface of the piston ring base material 11 before forming the DLC coating 12 is not particularly limited, but it is preferable to perform grinding or buffing to adjust the surface roughness. In addition, when the surface roughness of the outer peripheral surface of the piston ring base material 11 is small, smoothing processing is not necessary.
- the DLC film 12 is preferably selected from aC and taC having a hydrogen content of 0.5 at% or less (substantially hydrogen-free).
- the thickness of the DLC coating 12 is preferably 1 ⁇ m or more, except for the underlying layer.
- the upper limit is not particularly limited, it is preferably 30 ⁇ m or less, and more preferably 20 ⁇ m or less, because an excessively thick film may lead to a decrease in productivity and an increase in cost.
- the DLC coating 12 satisfies the parameters of the plastic deformation work and the elastic deformation work measured by the nanoindentation test, and desirable physical properties as a coating are described below.
- Nanoindentation hardness The DLC coating 12 may have a nanoindentation hardness of 15.0 GPa to 30.0 GPa, 28.0 GPa or less, and 26.0 GPa or less. Considering wear resistance, it is usually preferable to have a coating with a high hardness. Due to the coating formed on the outer peripheral surface of the ring, the coating may be broken when deformation is involved during assembly work to the piston, etc. Therefore, in the present embodiment, it is preferable to set the hardness in the above range, which is not excessively hard.
- the DLC coating 12 preferably has a Young's modulus of 335 GPa or less, more preferably 310 GPa or less.
- Young's modulus exceeds 335 GPa, when deposits such as carbon sludge or foreign matter such as abrasion powder and dust generated by sliding pass through the surface of the DLC coating, brittle fracture appears in the outermost layer of the DLC coating, increasing wear.
- the lower limit is not particularly limited, when the Young's modulus is 120 GPa or more, peeling inside the film is less likely to occur.
- the method for manufacturing the hard carbon coating according to this embodiment is not particularly limited.
- One example is a method of forming a coating using a filtered cathode vacuum arc (FCVA) method.
- FCVA filtered cathode vacuum arc
- a DLC film may be formed under a single condition, and the applied pulse bias voltage, substrate temperature, chamber pressure (vacuum degree), arc current, target purity, etc. are changed, or pulse
- the DLC coating may be formed by depositing multiple times without changing the bias voltage.
- the applied pulse bias voltage is higher than usual, for example -500V to -2500V, preferably -700V to -2500V, more preferably -1000V to -2500V.
- Example/Comparative Example With the piston ring base material set in the apparatus, the inside of the apparatus was evacuated to reduce the pressure, and then the base material was heated. After that, by appropriately changing the substrate temperature, pulse bias voltage, chamber pressure (degree of vacuum), arc current, target purity, etc., by the FCVA method, as shown in Table 1, Example 1 Piston rings having a hard carbon coating of Comparative Examples 1 to 4 were obtained. A nanoindentation test was performed on the obtained hard carbon coating of the piston ring under the following conditions. Measured values are 4 points at each of 3 points in the circumferential direction of one piston ring, the position on the opposite side of the gap of the piston ring and the position 90° on both sides from the gap, 4 points in total, 12 points in total.
- FIG. 2 shows an outline of the pin-on-plate type reciprocating friction and wear test.
- martensitic stainless steel was used as a piston ring base material having a nominal diameter of 86 mm and a width in the sliding direction of 1.2 mm.
- a piston ring with a machined surface was prepared.
- a piston ring member having a circumference of 20 mm was cut out from each of three positions, namely, the position on the opposite side of the joint of the piston ring and the position at 90° on both sides from the joint, and tested.
- the cut piston ring member was subjected to final finishing, and the surface roughness of the piston ring member after final finishing had a plateau-shaped roughness curve and a maximum height Rz of 1.0 ⁇ m.
- the lower test piece 110 is a material equivalent to JIS FC250, and a plate having a width of 17 mm, a length of 70 mm, and a thickness of 14 mm is prepared to simulate a flake graphite cast iron cylinder bore having a hardness of HRB 100 and carbide precipitation of 3%.
- Surface finishing was performed with #600 emery paper and the surface roughness was 1.2 ⁇ m at maximum height Rz.
- the test conditions for the wear amount measurement test are shown below.
- the sliding surfaces of the upper test piece 100 and the lower test piece 110 were lubricated with 150 ⁇ L (microliters) of engine lubricating oil 0W-20 in which carbon sludge and the like generated during actual engine operation were concentrated for one hour of the test.
- ⁇ Test conditions> ⁇ Stroke: 50mm ⁇ Load: 50N ⁇ Speed: 300 cycles/min ⁇ Temperature of lower test piece: 80°C (using heater 122 for heating lower test piece provided on movable block 120)
- ⁇ Test time 60 minutes
- the wear amount in Table 2 is a relative value with the value of Comparative Example 1 set to 1.
- Example 1 the DLC coatings of Example 1, Examples 3-4, Examples 6-7, and Comparative Example 1 were formed on SKD11 material plates, and Rockwell indentation tests and scratch tests were performed as follows. Table 3 shows the results. A Rockwell indentation test and a scratch test were performed to evaluate the crack generation conditions (length, number of cracks, etc.), and it was confirmed that the more cracks and the longer the cracks, the greater the amount of wear. Further, FIG. 3 shows an electron microscope image of cracks generated on the DLC coating surface in actual machine operation, and FIG. 4 and FIG. Microscopic images are shown.
- Piston ring 11 Piston ring base material 12 DLC coating 13 Base layer 100
- Upper test piece 110 Lower test piece 120 Movable block 122
Abstract
Description
すなわち、従来開示されているDLC被膜を有する摺動部材では、カーボンスラッジ等の異物が混入時の耐摩耗性(耐アブレシブ摩耗性)は十分ではないという問題がある。
カーボンスラッジ等の異物が介在した状態で摺動することにより、DLC被膜の摺動面に微細なクラックが生じることがあり、こうしたクラックの進展により摺動面の微小破壊が生じ、摩耗が増大すると本発明者らは推定している。
本発明は、上記問題に鑑みてなされたものであり、カーボンスラッジ等の異物が存在する環境下でも耐摩耗性(耐アブレシブ摩耗性)を有する摺動部材を提供するものである。
前記DLC被膜は、ナノインデンテーション試験により荷重100mNで測定された、塑性変形仕事量(Wplast)が5.7nJ以上である摺動部材である。
内燃機関で用いられる摺動部材としては、ピストンリング、シリンダライナ、カムシャフト等があげられ、以下、摺動部材の典型例としてピストンリングを用いて説明する。
更に、前記ナノインデンテーション試験により測定された、塑性変形仕事量(Wplast)は6.2nJ以上であることが好ましい。また、塑性変形仕事量の上限値は特に限定されないが、8.0nJ以下であれば好適である。
上記範囲を満たすことで、DLC被膜にクラックの進展による摺動面の微小破壊が生じにくく、アブレシブ摩耗の増大を抑制できるため、好ましい。
Wtotal = Wplast + Welast (1)
上記範囲を満たすことで、DLC被膜にクラックの進展による摺動面の微小破壊が生じにくく、アブレシブ摩耗の増大を抑制できるため、好ましい。
ηplast = (Wplast / Wtotal)×100(%) (2)
上記範囲を満たすことで、DLC被膜にクラックの進展による摺動面の微小破壊が生じにくく、アブレシブ摩耗の増大を抑制できるため、好ましい。
図1に示すピストンリング10は、ピストンに形成されたピストンリング溝(不図示)に装着され、ピストンの往復運動によってシリンダボア(不図示)の内周面を摺動しながら往復運動する。
ピストンリング10は、トップリング、セカンドリング、オイルリングの何れのピストンリングとして用いてもよい。なお、オイルリングに適用する場合は、オイルリング本体とコイルエキスパンダからなる2ピース構成オイルリングのオイルリング本体、及び2本のセグメント(サイドレールともいう)とエキスパンダ・スペーサからなる3ピース構成オイルリングのセグメント、のいずれにも適用することができる。なお一形態では、ピストンリングは、アルミニウム合金製ピストンに装着され、鋳鉄製シリンダボアに対するピストンリングとして用いられるが、ピストンやシリンダの材質はこれらに限られるものではない。
下地層13の膜厚は0.2μm以上2.0μm以下であることが好ましい。このような膜厚とすることで、DLC被膜12とピストンリング基材11との密着性をより向上させることができる。尚、下地層13を備えることなく、ピストンリング基材11の平滑化加工された外周面に直接DLC被膜12を成膜してもよい。
DLC被膜12の成膜前におけるピストンリング基材11の外周面の平滑化加工の方法は特に限定されないが、研削加工またはバフ研磨加工等を施し、表面粗さを調整することが好ましい。なお、ピストンリング基材11の外周面の表面粗さが小さい場合には、平滑化加工しなくてもよい。
[ナノインデンテーション硬さ]
DLC被膜12は、ナノインデンテーション硬さが15.0GPa以上30.0GPa以下であってよく、28.0GPa以下であってよく、26.0GPa以下であってよい。通常、耐摩耗性を考慮すると、被膜の硬さは高い方が好まれるが、被膜の硬さが高すぎる場合にはシリンダボア摺動面攻撃性が高くなる傾向にあること、及びDLC被膜はピストンリング外周面に形成する被膜のため、ピストンへの組み付け作業時等の変形を伴う場合の被膜破壊が発生することから、本実施形態では過度に硬すぎない上記範囲とすることが好ましい。
DLC被膜12は、ヤング率が335GPa以下であることが好適であり、310GPa以下であることがより好ましい。ヤング率が335GPaを超えると、カーボンスラッジ等によるデポジットまたは摺動によって生じた摩耗粉やダスト等の異物がDLC被膜表面を通り抜ける際、DLC被膜の最表面層は脆性破壊が出現し損耗が増大する。一方、下限は特に限定されないが、ヤング率が120GPa以上であることで、膜内部の剥離が生じにくくなる。
ピストンリング基材を装置内にセットした状態で、装置内を真空排気して減圧した後、基材を加熱した。その後に基材に対して、FCVA法により、基板温度、パルスバイアス電圧、チャンバの圧力(真空度)、アーク電流、ターゲットの純度などを適宜変化させることで、表1に示すとおり、実施例1~7及び比較例1~4の硬質炭素被膜を有するピストンリングを得た。
得られたピストンリングの硬質炭素被膜に対し、以下の条件でナノインデンテーション試験を実施した。測定値は、一つのピストンリングの周方向において、ピストンリングの合い口の反対側の位置と、合い口からそれぞれ両側に90°の位置、計3箇所の各位置において、それぞれ4点総計12点の測定値の平均値とした。
装置名:フィッシャー・インストルメンツ製ナノインデンテーション測定器、型式HM-2000
押し込み荷重:100mN
負荷時間:30s(秒)
保持時間:5s(秒)
除荷時間:30s(秒)
得られた荷重-押し込み深さ曲線を解析し、結果を表1にまとめた。
図2に、ピンオンプレート式往復動摩擦摩耗試験の概要を示す。まず、マルテンサイト系ステンレス鋼を呼び径86mm、摺動方向の幅が1.2mmのピストンリング基材とし、その外周面に上記各実施例、比較例のDLC被膜を成膜し、外周摺動面を加工したピストンリングを準備した。該ピストンリングの合い口の反対側の位置と、合い口からそれぞれ両側90°の位置、計3箇所の各位置において、周長20mmのピストンリング部材を切り出し、供試した。切り出したピストンリング部材は最終仕上げを行い、最終仕上げ後のピストンリング部材の表面粗さは、粗さ曲線がプラトー形状であり、最大高さRz1.0μmとし、上試験片100とした。
下試験片110は、JIS FC250相当材であり、硬さがHRB100、炭化物析出が3%の片状黒鉛鋳鉄製シリンダボアを見立てた幅17mm、長さ70mm、厚さ14mmのプレートを作製し、最終表面仕上げを#600エメリーペーパーにより行って、表面粗さは最大高さRzで1.2μmであった。
<試験条件>
・ストローク:50mm
・荷重:50N
・速度:300cycle/min
・下試験片の温度:80℃(可動ブロック120に設けた下試験片加熱用ヒータ122使用)
・試験時間:60min
摩耗量(n=3の平均値)の測定結果を表2に示した。なお、表2の摩耗量は、比較例1の値を1とした相対値である。
また、図3に、実機運転におけるDLC被膜表面に生じたクラックの電子顕微鏡画像を示し、図4及び図5に、それぞれ実施例1及び比較例1のDLC被膜に対するロックウェル圧痕試験結果を示すレーザー顕微鏡画像を示す。
ISO26443に準拠し、先端半径0.2mmのダイヤモンド圧子を、荷重150kgfでDLC被膜に押し込み、DLC被膜表面をレーザー顕微鏡で観察した。圧痕の上下左右4視野を拡大(レンズ倍率50倍)し、それぞれの視野内における最も長いクラックから(長い順)3本の長さの平均値を計算した。1サンプルについて3回計測し、その平均値を採用した(n=12)。結果を表3に示す。
Anton Paar製スクラッチ試験機を用い、荷重を1Nで一定とし、速度10mm/minで水平に2mm移動させた。スクラッチ試験の結果を電子顕微鏡で観察し、クラックの発生について評価した(n=3)。評価基準は以下のとおりであり、結果を表3に示す。
A:スクラッチ試験後のDLC被膜表面にクラックは発生していなかった。
B:スクラッチ試験後のDLC被膜表面にクラックは発生していたが、その数は比較的少なかった。
C:スクラッチ試験後のDLC被膜表面にクラックがある程度の数発生していた。
D:スクラッチ試験後のDLC被膜表面にクラックが相当多く発生していた。
11 ピストンリング基材
12 DLC被膜
13 下地層
100 上試験片
110 下試験片
120 可動ブロック
122 下試験片加熱用ヒータ
Claims (6)
- 外周摺動面にDLC被膜を有する摺動部材であって、
前記DLC被膜は、ナノインデンテーション試験により荷重100mNで測定された、塑性変形仕事量(Wplast)が5.7nJ以上である、摺動部材。 - 前記DLC被膜は、前記ナノインデンテーション試験により測定された、下記式(1)で計算される全仕事量(Wtotal)が18.1nJ以上である、請求項1に記載の摺動部材。
Wtotal = Wplast + Welast (1) - 前記DLC被膜は、前記ナノインデンテーション試験により測定された、下記式(2)で計算される塑性変形仕事率(ηplast)が31.3%以上である、請求項1又は2に記載の摺動部材。
ηplast = (Wplast / Wtotal)×100(%) (2) - 前記DLC被膜は、前記ナノインデンテーション試験により測定された、ナノインデンテーション硬さ(HIT)と塑性変形仕事量(Wplast)の比率(HIT/Wplast)が5.3GPa/nJ以下である、請求項1~3のいずれか1項に記載の摺動部材。
- 前記DLC被膜は、水素含有量が0.5at%以下である、請求項1~4のいずれか1項に記載の摺動部材。
- ピストンリングである、請求項1~5のいずれか1項に記載の摺動部材。
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