JP2018076958A - piston ring - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piston ring which is easy in film formation, and has a hard carbon film which is excellent in abrasion resistance.SOLUTION: A piston ring has a hard carbon film 4 which is formed on an external peripheral slide face 11 of a piston ring base material 1, and the hard carbon film 4 is a laminated film or a single layer film, and contains silicon in a range of 2-atom% or higher and 12-atom% or lower. An spcomponent ratio which is measured at a TEM-EELS spectrum which is obtained by combining an electronic energy loss spectrometry (EELS) to a permeation-type electronic microscope is within a range of 40% or higher and 80% or lower. A hydrogen content of the hard carbon film 4 is within a range lower than 5-atom%. A total thickness of the hard carbon film 4 is within a range of 0.5 μm or thicker and 20 μm or thinner.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a piston ring provided with a hard carbon film excellent in wear resistance.

  In recent years, piston rings used in internal combustion engines are increasingly used in severe environments of high temperatures and high pressures, and further improvements in wear resistance, initial conformability, low friction, and the like are required. In response to such a demand, for example, Patent Document 1 proposes a piston ring including a carbon-based film having low friction and wear resistance. Specifically, it is a laminated film in which two or more types of layers having different hardnesses are laminated, and the difference in hardness between the two types of layers is 500 to 1700 HV, and a layer having a high hardness is a thickness of a layer having a low hardness. And a piston ring having a thickness of 5.0 μm or more has been proposed. At this time, the low hardness layer is formed by sputtering, and the high hardness layer is formed by ion plating.

  Patent Document 2 proposes a piston ring having an amorphous hard carbon film that has excellent adhesion to the piston ring substrate, high hardness, and excellent wear resistance. Specifically, formed on the surface of the piston ring base material, the first amorphous hard carbon layer substantially containing only hydrogen and containing almost no hydrogen, and the surface of the first amorphous hard carbon layer A second amorphous hard carbon layer formed substantially only of carbon, and when viewed from the cross section, the transmission electron microscope image of the first amorphous hard carbon layer is the second amorphous A piston ring brighter than a transmission electron microscope image of a hard carbon layer has been proposed.

Patent Document 3 proposes a technique related to a hydrogen-free and high-hardness DLC film while improving the heat resistance of the DLC film formed on the surface of the lens mold. This technique relates to a DLC film to which elements other than hydrogen and carbon are added. In a Raman spectrum of a DLC film to which silicon is added, an S band having a peak between 1000 and 1200 cm ⁻¹ is obtained. It is described that a DLC film made of ta-C (tetrahedral amorphous carbon) having an sp ³ bond at a predetermined ratio or more can be obtained because an abbreviated characteristic band is detected. Silicon contained in such a DLC film is added using a silicon carbide target, and such a DLC film can impart suitable heat resistance even when the lens mold is heated.

JP 2012-202522 A JP 2007-169698 A International Publication WO2016 / 021671A1

  However, the technique of Patent Document 1 has a multilayer structure in which layers having different hardnesses are alternately and repeatedly stacked by different film forming means, and film formation is complicated. Further, when the thickness of the high hardness layer is 5 nm to 90 nm, it is difficult to maintain the wear resistance because the high hardness layer cannot always be maintained. Moreover, although the technology of Patent Document 2 describes the relationship between brightness and density and adhesion in a transmission electron microscope, whether or not it is an amorphous hard carbon layer having high hardness and excellent wear resistance. It was not fully examined.

Further, the technique of Patent Document 3 relates to a DLC film that can impart suitable heat resistance even when a lens mold is heated, and ta− mainly having sp ³ bonds (diamond structure). It is a DLC film made of C, and it has not been proposed to improve low friction and wear resistance in lubricating oil. When a Raman spectrum is measured using laser light set to a wavelength of 500 to 600 nm, and a characteristic band having a peak between 1000 and 1200 cm ⁻¹ (also referred to as an S band) is detected. , Even though it can be confirmed that sp ³ bonds (diamond structure) are included, the sp ³ content cannot be clearly determined, and it is sufficient to determine ta-C having a relatively large sp ³ content. Not considered.

  The present invention has been made in order to solve the above-mentioned problems, and its object is to form a piston having a hard carbon film that is easy to form, has low friction (mechanical friction loss), and has excellent wear resistance. To provide a ring.

The piston ring according to the present invention has a hard carbon film formed on at least an outer peripheral sliding surface of a piston ring base material, and the hard carbon film is a laminated film or a single layer film, and silicon is 2 atomic%. As mentioned above, it is contained in the range of 12 atomic% or less, and sp ² component ratio measured by the TEM-EELS spectrum which combined the electron energy loss spectroscopy (EELS) with the transmission electron microscope (TEM) is 40% or more. It is characterized by being in the range of 80% or less.

  In the piston ring according to the present invention, the hard carbon film has a hydrogen content of less than 5 atomic%.

In the piston ring according to the present invention, the laminated film may include a white layer having a large sp ² component ratio.

  The piston ring which concerns on this invention can be comprised so that the total thickness of the said hard carbon film | membrane may be in the range of 0.5 micrometer or more and 20 micrometers or less.

  The piston ring which concerns on this invention WHEREIN: The said hard carbon film | membrane can be comprised so that it may be formed on the hard carbon base film in the range whose thickness is 0.05 micrometer or more and 0.5 micrometer or less.

  According to the piston ring of the present invention, film formation is easy, friction is low, and wear resistance is excellent.

It is typical sectional drawing which shows the example of the piston ring which concerns on this invention. It is typical sectional drawing which shows an example of the sliding surface of the piston ring which concerns on this invention. It is typical sectional drawing which shows another example of the sliding surface of the piston ring which concerns on this invention. It is typical sectional drawing which shows the further another example of the sliding surface of the piston ring which concerns on this invention. It is a surface photograph of the hard carbon film of Example 1 which shows a macro particle. It is a cross-sectional TEM image of the hard carbon film which consists of laminated films. FIG. 5 is a diagram illustrating the principle of a frictional wear test using a disk-type test piece. It is a photograph which shows a SRV test result. It is a photograph which shows the SRV test result at the time of carrying out forced abrasion with a diamond (average particle diameter of 0.25 micrometer) slurry.

  A piston ring according to the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments as long as it has the technical features.

As shown in FIGS. 1 to 4, the piston ring 10 according to the present invention has a hard carbon film 4 formed on at least the outer peripheral sliding surface 11 of the piston ring base material 1. And the hard carbon film 4 is a laminated film or a single layer film, and silicon is contained in the range of 2 atomic% or more and 12 atomic% or less. Further, the hard carbon film 4 has a sp ² component ratio measured by a TEM-EELS spectrum in which a transmission electron microscope (TEM) is combined with an electron energy loss spectroscopy (EELS) in a range of 40% to 80%. Is within. Such a hard carbon film 4 has low friction and high wear resistance. The hard carbon film 4 is a hydrogen-free film having a hydrogen content of less than 5 atomic%.

  Hereinafter, the components of the piston ring will be described in detail.

(Piston ring base material)
Examples of the piston ring base material 1 include various types used as a base material for the piston ring 10, and are not particularly limited. For example, various steel materials, stainless steel materials, cast materials, cast steel materials, and the like can be applied. Among these, martensitic stainless steel, chromium manganese steel (SUP9 material), chromium vanadium steel (SUP10 material), silicon chromium steel (SWOSC-V material), and the like can be given.

  The piston ring substrate 1 may be previously nitrided to form a nitrided layer (not shown). Or wear-resistant film (not shown) such as Cr-N, Cr-BN, Cr-BVN, Cr-BV-Ti-N, Ti-N, etc. in advance. It may be formed. Among these, it is preferable to form a wear-resistant film such as Cr—N, Cr—B—N, Cr—B—V—N, or Ti—N. The piston ring 10 according to the present invention exhibits excellent wear resistance without providing such a nitriding treatment or Cr-based or Ti-based wear-resistant coating, so that nitriding treatment or Cr-based or Ti-based wear resistance is provided. The protective film is not an essential component and can be provided as necessary.

  The piston ring base material 1 may be pretreated as necessary. As pretreatment, it is preferable to adjust the surface roughness by surface polishing. The surface roughness is preferably adjusted by, for example, a method of lapping the surface of the piston ring substrate 1 with diamond abrasive grains and polishing the surface. By adjusting the surface roughness, the surface roughness of the piston ring substrate 1 is within a preferable range of 0.02 μm or more and 0.07 μm or less in arithmetic average roughness Ra in JIS B 0601 (2001), ISO 4287: 1997. Can be adjusted. The piston ring base material 1 adjusted in this way is used as a pretreatment before forming the hard carbon base film 3 described later or as a pretreatment of the base film 2 provided in advance before forming the hard carbon base film 3. It can be preferably applied.

(Undercoat)
As shown in FIG. 4, the piston ring substrate 1 may be provided with a base film 2 such as titanium or chromium. The base film 2 is not necessarily provided, and its formation is arbitrary. The base film 2 such as titanium or chromium can be formed by various film forming means. For example, a film forming means such as a vacuum deposition method, a sputtering method, or an ion plating method can be applied to the base film 2 such as titanium or chromium. The thickness of the base film 2 is not particularly limited, but is preferably in the range of 0.05 μm or more and 2 μm or less. The base film 2 is preferably formed at least on the outer peripheral sliding surface 11 on which the piston ring 10 slides in contact with a cylinder liner (not shown). However, other surfaces such as the upper surface 12, the lower surface 13, and the inner peripheral surface 14 of the piston ring 10 may be formed.

  The undercoat film 2 is formed, for example, by setting the piston ring base material 1 in the chamber, evacuating the chamber, introducing pre-heating, ion cleaning, or the like to introduce an inert gas, and performing vacuum deposition or ion plating. It can be performed by means such as a ting method.

  As shown in FIG. 4, the base film 2 may be directly formed on the piston ring base material 1, and the hard carbon base film 3 described later is formed on the base film 2 described above. It is desirable that The base film 2 improves the adhesion between the piston ring substrate 1, the hard carbon base film 3 and the hard carbon film 4, and forms the hard carbon base film 3 on the base film 2, thereby forming the hard carbon. Nucleation and nucleus growth when the base film 3 is formed at a low speed can be further suppressed. As a result, the hard carbon film 4 formed on the hard carbon base film 3 can be formed as a smooth film with small surface irregularities.

(Hard carbon base film)
It is preferable that the hard carbon base film 3 is provided on the piston ring base material 1. Specifically, the hard carbon base film 3 is preferably formed at least on the outer peripheral sliding surface 11 on which the piston ring 10 slides in contact with a cylinder liner (not shown). However, other surfaces such as the upper surface 12, the lower surface 13, and the inner peripheral surface 14 of the piston ring 10 can be arbitrarily formed.

  As shown in FIGS. 1 to 3, the hard carbon base film 3 may be directly provided on the piston ring substrate 1, or may be provided on the surface after nitriding described above or an abrasion-resistant film. Alternatively, as shown in FIGS. 4A and 4B, it may be provided on the base film 2 such as titanium or chromium described above. It is preferable that a hard carbon film 4 to be described later is directly provided on the hard carbon base film 3 without interposing another film.

  The hard carbon base film 3 may be the same hard carbon film as a component of the later-described hard carbon film 4 containing silicon, or may be a hard carbon film having less silicon content than the hard carbon film 4. Further, it may be a hard carbon film not containing silicon. Since this hard carbon base film 3 is formed in the process before the formation of the hard carbon film 4, it is easy to manufacture that it is the same as the components of the hard carbon film 4 described later containing silicon. Although it is advantageous from the viewpoint of improving the wear resistance, it is not limited to this.

  The hard carbon base film 3 can usually be formed by a film forming means such as an ion plating method by vacuum arc discharge using a carbon target. For example, when the hard carbon base film 3 is formed by an ion plating method using vacuum arc discharge (hereinafter referred to as “arc ion plating method”), specifically, the piston ring substrate 1 or the wear resistance in advance. After the piston ring base material 1 provided with the film, the base film 2 and the like is set in a chamber and the inside of the chamber is evacuated, carbon plasma can be emitted from the carbon target to form a film. The hard carbon base film 3 containing silicon can be obtained by forming a film using a carbon target containing silicon. The silicon content in the carbon target is set so that the silicon content in the hard carbon base film 3 after film formation is within a desired range. For example, similarly to the hard carbon film 4 described later, when silicon is to be contained within the range of 2 atomic% or more and 12 atomic% or less, the carbon target is placed so that the content is within the above range. What is necessary is just to contain a fixed amount of silicon.

  The hard carbon base film 3 may be formed by controlling the film formation speed of the hard carbon film 4 to be described later so as to decrease the film formation speed. That is, the film may be formed under low-speed film formation conditions. As a method for reducing the film forming conditions, a means for reducing the arc current in the arc ion plating method can be mentioned. In particular, it is preferable to form a film by an arc ion plating method in which the arc current is in the range of 40A to 100A and the pulse bias voltage is in the range of −2000V to −100V.

  The arc current described above when the hard carbon base film 3 is formed at a lower deposition rate is smaller than the arc current when forming the hard carbon film 4 described later. Therefore, there is an advantage that it is possible to suppress poor adhesion due to a sudden increase in arc current that is likely to occur when the hard carbon film 4 is formed without forming the hard carbon base film 3 on the piston ring substrate 1. . Furthermore, the formation of the hard carbon base film 3 with a small arc current has the advantage that it can suppress nucleation, suppress nucleation, and suppress increase in macro particles. In order to suppress such increase in macro particles, the hard carbon film 4 described later can be formed as a smooth film with small surface irregularities that is not affected by the hard carbon base film 3.

  When reducing the arc current, it is preferable to set the arc current value to 80% or less of the arc current value when the hard carbon film 4 is formed. When formed with an arc current value of 80% or less, the function as the hard carbon base film 3 can be effectively expressed. That is, the hard carbon base film 3 formed under the low-speed film formation conditions suppresses nucleation and also suppresses nucleation. Therefore, the hard carbon film 4 formed on the hard carbon base film 3 can suppress adhesion failure due to a sudden increase in arc current, and can further suppress an increase in macro particles in the hard carbon film 4. . In order to suppress the increase in macro particles, the hard carbon film 4 can be formed as a smooth film with small surface irregularities that is not affected by the hard carbon base film 3. As a result, the wear resistance of the hard carbon film 4 can be improved. The arc current value at this time is preferably 50% of the arc current value at the time of forming the hard carbon film 4 in order to make it act as the hard carbon base film 3 preferably.

  The above-described action of the hard carbon base film 3 formed under the low-speed film formation condition can be effectively realized when the hard carbon base film 3 has a thickness of 0.05 μm or more and 0.5 μm or less. If the thickness of the hard carbon base film 3 is too thin, such as less than 0.05 μm, there is a problem that the macro particle suppression effect in the hard carbon film 4 cannot be obtained. On the other hand, if the thickness of the hard carbon base film 3 is too thick so as to exceed 0.5 μm, there is a problem that the formation of the hard carbon base film 3 is delayed and the cost is increased.

  The hardness of the hard carbon base film 3 thus formed is in the range of about 2000 HV0.05 to 4000 HV0.05 in terms of Vickers hardness. In addition, since the hard carbon base film 3 in the above-described thickness range is too thin and it is difficult to measure the Vickers hardness of the hard carbon base film 3 itself, the Vickers hardness (JIS B 7725, ISO) when formed to be as thick as about 5 μm under the same film formation conditions. 6507). The measurement can be performed using a Vickers hardness tester (manufactured by Futuretec Co., Ltd.) or the like, and “HV0.05” means Vickers hardness at 50 gf load. Further, when the hardness of the hard carbon base film 3 is measured by the nanoindentation method, the indentation hardness HIT (15 mN load) is in the range of 20 GPa or more and 45 GPa or less. The measurement by the nanoindentation method can be performed using, for example, nanoindentation manufactured by Elionix Corporation.

(Hard carbon film)
As shown in FIGS. 1, 2 and 4A, the hard carbon film 4 is formed at least on the outer peripheral sliding surface 11 on which the piston ring 10 slides in contact with a cylinder liner (not shown). The hard carbon film 4 may be arbitrarily formed on other surfaces other than the outer peripheral sliding surface 11, for example, the upper surface 12, the lower surface 13, and the inner peripheral surface 14 of the piston ring 10.

  The hard carbon film 4 may be a laminated film or a single layer film. In the case of a laminated film, it is a film composed of a plurality of layers (also referred to as a nano laminated film), and may be a film in which layers having the same thickness or different thicknesses are laminated, and gradually increases in thickness. Alternatively, it may be a gradient film laminated so as to be thin, a film in which thick layers and thin layers are alternately or periodically laminated, or other various lamination modes. A laminated film may be used. The thickness of each layer constituting the laminated film is not particularly limited, but is preferably in the range of 1 nm to 20 nm per layer, and more preferably in the range of 3 nm to 10 nm. The hard carbon film 4 which is a laminated film in which such thin layers are laminated is excellent in wear resistance.

  The total thickness of the hard carbon film 4 made of a laminated film or a single layer film is preferably in the range of 0.5 μm or more and 20 μm or less. The total thickness of the hard carbon film 4 may be a relatively thin range within a range of 0.5 μm or more and less than 2 μm, or may be a relatively thick range within a range of 2 μm or more and 20 μm or less. Even if the total thickness of the hard carbon film 4 is thin, the initial conformability can be improved and the wear resistance can be improved. However, if the total thickness is large, the effect is further sustained. .

  The hard carbon film 4 made of a laminated film has an arc current in the range of 80 A (however, larger than the arc current of the hard carbon base film 3) to 120 A, and a pulse bias voltage in the range of −2000 V to −100 V. It is preferable to form a film by an ion plating method. FIG. 6 is a cross-sectional TEM image of the hard carbon film 4 made of a laminated film. Such a laminated film can be formed, for example, by repeatedly changing film forming conditions such as arc current and bias voltage over time.

In the laminated film shown in FIG. 6, a thin white layer is periodically present. This white layer is, sp ² components more than sp ³ components, sp ² components ratio ^{(sp 2 / (sp 2 +} sp 3)) is rich layer, specifically, this layer is, sp ² components A layer having a ratio (sp ² / (sp ² + sp ³ )) of 50% or more and 60% or less. This white layer is a layer having a richer graphite structure than the diamond structure, and has the property of relaxing the film stress. Therefore, it is possible to improve the film toughness of the hard carbon film 4 made of a laminated film. It is believed that there is.

  The hard carbon film 4 made of a laminated film can be formed by alternately applying two or more different bias voltages in the form of pulses, and can have a laminated form as shown in FIG. As an example, 1) a predetermined low bias voltage and a predetermined high bias voltage can be alternately applied in a pulsed manner. For example, a low bias voltage of −140 V and a high bias voltage of −220 V are pulsed. Alternatively, the films may be alternately formed. 2) A predetermined low bias voltage and a gradually increasing bias voltage can be alternately applied in a pulsed manner as a pulse voltage. For example, a low bias voltage of −140 V and a high bias voltage gradually increasing from −220 V to −160 V Alternatively, the film may be alternately formed in a pulse shape. 3) A predetermined low bias voltage and a predetermined high bias voltage can be alternately applied in a pulse shape. For example, a low bias voltage of −140V, a high bias voltage of −220V, a low bias voltage of −150V, and − The film may be formed by applying a high bias voltage of 1800 V in the form of pulses in the order of the cycles. An example in which two or more different bias voltages are alternately applied in the form of pulses is not limited to the above 1) to 3), and other examples may be applied. Note that the number of repetitions of the pulse bias voltage is set so that the thickness of the laminated film is within the above-described range.

  Note that the thin white layer appearing in the laminated film shown in FIG. 6 is a layer having a richer graphite structure than the diamond structure as described above. Such a white layer can be formed, for example, by increasing the bias voltage or by increasing the application time of the high bias voltage when alternately applying the high bias voltage and the low bias voltage. As shown in FIG. 6, if it is formed at regular intervals, it is preferable in terms of improving the film toughness. However, it may be present irregularly, and the film toughness can be improved even without a regular or irregular white layer. If it can be secured to some extent, the white layer may not be formed.

  The hard carbon film 4 made of a single layer film has an arc current in the range of 80 A (but larger than the arc current of the hard carbon base film 3) to 120 A, and a pulse bias voltage in the range of −2000 V to −100 V. Films can be formed by arc ion plating. The single layer film can be formed, for example, by keeping the film formation conditions such as arc current and pulse bias voltage constant over time. The term “single layer film” is used to include an inclined film that cannot be observed with a TEM image or the like, such as a laminated film. For example, the film formation conditions such as arc current and bias voltage are gradually increased. An altered gradient film is also included.

  In the present invention, when the hard carbon film 4 contains silicon, the friction (mechanical friction loss) can be reduced and the wear resistance can be remarkably improved. It is preferable that silicon in the hard carbon film 4 is contained within a range of 2 atomic% or more and 12 atomic% or less. It should be noted that when the silicon content was less than 2 atomic%, the wear resistance could not be remarkably increased. In addition, it was difficult for the silicon content to exceed 12 atomic%. A more preferable silicon content can be in the range of 2 atomic% or more and 10 atomic% or less for the manufacturing reason that the film formation rate is lowered by the increase in the content. The silicon content in the hard carbon film 4 is expressed as a result of measurement by a quantitative analysis method using an electron probe microanalyzer (EPMA).

  The hard carbon film 4 containing silicon can be obtained by forming a film using a carbon target containing silicon. The silicon content in the carbon target is set so that the silicon content in the hard carbon film 4 after film formation is within the above range, and the content is in the range of 2 atomic% or more and 12 atomic% or less. A predetermined amount of silicon is contained in the carbon target so as to be inside.

  The hard carbon film 4 does not substantially contain hydrogen and is, for example, less than 5 atomic%, and is usually 2 atomic% or less in the film forming method of the present invention. The lower limit of the hydrogen content is not particularly limited, but is not included (0 atomic%) or about 0.1 atomic%. In the present invention, the formation of the hard carbon film 4 and the formation of the hard carbon base film 3 described above are performed under conditions that do not include a hydrogen component. The hard carbon base film 3 and the hard carbon film 4 can be preferably formed by an arc ion plating method using a carbon target containing silicon. As a result, since hydrogen or hydride is not included in the film forming process, the hard carbon base film 3 and the hard carbon film 4 are substantially free of hydrogen components or inevitably included therein. Only. The term “substantially free” or “inevitable” means that the hydrogen content contained in the hard carbon base film 3 and the hard carbon film 4 is less than 5 atomic%. Yes. The hydrogen content means the content of the hard carbon film 4 as a whole. The hydrogen content in the hard carbon film 4 is represented by the result measured by the RBS / HFS analysis method. RBS is an abbreviation for Rutherford Backscattering Spectrometry, and HFS is an abbreviation for Hydrogen Forward Scattering.

  The hard carbon film 4 does not substantially contain oxygen due to the manufacturing method. For example, oxygen is less than 5 atomic%, and in the film forming method of the present invention, it is usually 2 atomic% or less. The reason why oxygen is not substantially contained is that oxygen and oxide are not included in the process of forming the hard carbon film 4. That is, the hard carbon film 4 includes only unavoidable impurities inevitably included in the process other than carbon and silicon, and does not substantially contain hydrogen or oxygen. The oxygen content means the content of the hard carbon film 4 as a whole, and if an arbitrary one point is analyzed, there may be a portion where oxygen inevitably mixed is 5 atomic% or more. The oxygen content in the hard carbon film 4 is expressed as a result of measurement by a TEM-EDX semi-quantitative method. EDX is an abbreviation for Energy Dispersive X-ray Spectroscopy.

  When the hard carbon film 4 is a laminated film, a carbon film not containing silicon may exist between a plurality of layers constituting the laminated film. The carbon film not containing silicon can be formed by adjusting the film forming conditions, and has an effect of relaxing the stress of each hard carbon film containing silicon. The thickness of the carbon film is not particularly limited, but can be in the range of, for example, 2 nm or more and 10 nm or less.

  Since the hard carbon film 4 is provided directly on the hard carbon base film 3 formed under low-speed film formation conditions to suppress nucleation and growth and suppress increase in macro particles, the surface is smooth with small surface irregularities. It can be formed as a simple film. The amount of macro particles appearing on the surface of the hard carbon film 4 is in the range of 0.1% to 10% in terms of area ratio. As a result, wear resistance and initial conformability can be made excellent. If the amount of macro particles exceeds 10% in terms of area ratio, surface irregularities may increase, and it may not be possible to achieve excellent wear resistance. On the other hand, when the amount of macro particles is less than 0.1% in terms of area ratio, excellent wear resistance can be realized, but film formation itself may be difficult, and manufacturing management and costs are somewhat difficult. . FIG. 5 is a surface photograph of the hard carbon film (silicon-containing hard carbon film) of Example 1 showing macro particles.

  The area ratio of the macro particle amount can be obtained by performing image analysis using a confocal microscope (OPTELICS H1200) manufactured by Lasertec Corporation. Specifically, the outer periphery of the piston ring was photographed (objective lens 100 times, monochrome confocal image), and automatic binarization was performed. The threshold value determination method was a discriminant analysis method, and after adjusting so as to exclude polishing scratches and the like, the area ratio was extracted from the binarized image. The area ratio of the macroparticles was determined by measuring five points on the film at an average value.

  In the present invention, by providing the hard carbon film 4 made of a laminated film or a single layer film on the hard carbon base film 3, there is an advantage that film peeling can be further suppressed. The reason for this is that in the case of a laminated film, a film formed at a lower bias voltage among two or more different bias voltages functions as a stress relaxation film, so that the piston ring base material 1 and the hard carbon base film 3 It acts to reduce the load applied to the interface. Further, when the base film 2 is formed, it acts to reduce the load applied to the interface between the base film 2 and the hard carbon base film 3. Also, in the case of a single layer film (including a gradient film), it is formed with a relatively low bias voltage, so that it functions as a stress relaxation film and is added to the interface between the piston ring substrate 1 and the hard carbon base film 3. Acts to reduce the load.

  In the piston ring 10 provided with such a hard carbon film 4, it can be preferably applied to an abutting portion where the contact is strengthened when temperature is applied, and in particular, it is possible to eliminate peeling of the film made of the hard carbon film 4 at the abutting portion. preferable.

  The hardness of the hard carbon film 4 is in the range of about 1000 HV0.05 to 2000 HV0.05 in terms of Vickers hardness. The hardness of the hard carbon film 4 is in the range of 10 GPa or more and 25 GPa or less in terms of the indentation hardness HIT (15 mN load) as measured by the nanoindentation method. The Vickers hardness (JIS B 7725, ISO 6507) can be measured using a micro Vickers hardness tester (Futuretec Co., Ltd.) or the like, and “HV0.05” is Vickers hardness at 50 gf Is meant to indicate. Moreover, the measurement by the nanoindentation method can be measured by using, for example, nanoindentation manufactured by Elionix Corporation.

The hard carbon film is a film in which a carbon bond sp ² bond typified by graphite and a carbon bond sp ³ bond typified by diamond are mixed. The sp ² component ratio, shows the graphite component of the hard carbon film (sp ²⁾ and the component ratio of the graphite component to the diamond component ^{(sp 3) (sp 2)} (sp 2 / (sp 2 + sp 3)) . In transmission electron microscope (TEM) observation, the layer rich in the sp ² component appears relatively white compared to the layer rich in the sp ³ component.

The hard carbon film 4 has a sp ² component ratio in the range of 40% or more and 80% or less, as measured by TEM-EELS in which a transmission electron microscope (TEM) is combined with electron energy loss spectroscopy (EELS). preferable. When the sp ² component ratio is less than 40%, the diamond component (sp ³ ) is mainly used, so that the film quality is dense but the toughness is low, which is not preferable for forming a hard carbon film. If the sp ² component ratio exceeds 80%, the graphite component (sp ² ) is the main component, which makes it difficult to form a hard carbon film, which is not preferable. As a preferable sp ² component ratio, as shown in Table 1 below, a range of 40% to 60% can be given. Such a covalent bond ratio can be measured by an EELS analyzer (manufactured by Gatan, Model 863 GIF Tridiem). This measurement can be performed by the following procedure.

(1) An EELS spectrum is measured by an EELS analyzer. For the measured EELS spectrum, a pre-peak is fitted with a linear function, a post-peak is fitted with a cubic function, and the peak intensity is normalized. (2) After that, the diamond data and the graphite data are compared, and the energy calibration is performed by aligning the peak start positions. (3) An area within the range of 280 eV to 310 eV is obtained for the calibrated data. (4) Two peaks in the range of 280 eV to 295 eV (one is a peak of sp ² and the other is a peak of CH or amorphous) and a peak area near 285 eV is obtained. (5) The area in the range of 280 eV to 310 eV in (3) above and the peak area in the vicinity of 285 eV in (4) above are taken. For this area ratio, graphite is set to 100, diamond is set to 0, and the sp ² component ratio is obtained from the relative value. The value thus obtained is used as the sp ² component ratio.

The sp ² component ratio of the hard carbon film is evaluated by obtaining a plurality of points as measurement points at equal intervals in the film thickness direction. The number of measurement points is not particularly limited, but may be 10 points as shown in the examples described later. In the present application, the “sp ² component ratio” obtained at a plurality of measurement points is represented by an average value of the film.

(Outermost film)
In the present invention, an outermost surface film 5 may be further provided on the hard carbon film 4 as necessary. Similar to the hard carbon film 4 described above, the outermost surface film 5 may be a laminate of thin hard carbon films (nanothin films) as shown in FIGS. 3 and 4B, or a single layer film. It may be. This outermost surface film 5 can act to further improve the initial conformability.

  When the outermost surface film 5 is a laminated film, the film is formed by repeating the high bias voltage process and the low bias voltage process by the arc ion plating method a plurality of times at a predetermined interval, like the hard carbon film 4 described above. can do. For example, while maintaining the arc current at 100 A to 150 A, which is about the same as the condition for forming the hard carbon film 4, the high bias voltage processing within the range of -2000V to -800V for the pulse bias voltage and -200V for the pulse bias voltage. The low bias voltage treatment within the range of -100V may be repeated a plurality of times at a predetermined interval. The predetermined interval is an interval of about 1 second to 10 seconds. The outermost film 5 thus formed has high hardness and increased toughness to prevent cracks and chips, and good initial conformability.

  Even when the outermost surface film 5 is a single layer film, it can be formed by changing the bias voltage in the arc ion plating method constant or gradually as in the case of the hard carbon film 4 described above. In the outermost surface film 5 as well, the single-layer film includes an inclined film.

  The total thickness of the outermost surface film 5 is formed within a range of about 0.05 μm or more and 1 μm or less. If the thickness of the outermost surface film 5 is too thin, there is a drawback that the effect of the initial conformability cannot be obtained. On the other hand, even if the thickness of the outermost surface film 5 is too thick, the effect of the initial conformability does not change. When the outermost surface film 5 is a laminated film, the thickness of each layer is in a range of about 0.01 μm or more and 0.02 μm or less, and a plurality of layers having a thickness within the range are laminated. ing. The thickness of the outermost surface film 5 can be measured with a transmission electron microscope (TEM). It is preferable that the hardness of the outermost surface after the process treatment of the outermost surface film 5 is formed to about 2000 HV0.05 in terms of Vickers hardness.

  As described above, in the piston ring 10 according to the present invention, since the hard carbon film 4 that is a laminated film or a single layer film contains silicon within the above range, the friction is low and the wear resistance is further improved. Can do.

  Hereinafter, the piston ring according to the present invention will be described in more detail with reference to examples, comparative examples, and conventional examples.

[Example 1]
C: 0.55 atomic%, Si: 1.35 atomic%, Mn: 0.65 atomic%, Cr: 0.70 atomic%, Cu: 0.03 atomic%, P: 0.02 atomic%, S: The piston ring base material 1 equivalent to SWOSC-V material was used in accordance with JIS standards consisting of 0.02 atomic%, balance: iron and inevitable impurities. A 30 μm Cr—N film (abrasion resistant film) was formed on the piston ring substrate 1 by an ion plating method. The surface roughness was adjusted by lapping polishing, and then a titanium film having a thickness of 0.08 μm was formed as the base film 2 by introducing an inert gas (Ar) by an ion plating method.

A hard carbon base film 3 made of an amorphous carbon film was formed on the base film 2. For the film formation, an arc ion plating apparatus is used, a carbon target containing 10 atomic% of silicon is used, and an arc current is 90 A and a pulse bias voltage is −130 V in a high vacuum chamber of 1.0 × 10 ⁻³ Pa or less. Was formed to a thickness of 0.2 μm under the condition of 12 minutes.

  A silicon-containing hard carbon film 4 made of a laminated film was formed on the hard carbon base film 3 using the same arc ion plating apparatus. This film formation was performed by applying an arc current of 120 A and a predetermined low bias voltage and a predetermined high bias voltage alternately in a pulsed manner. Specifically, a low bias voltage of -150 V and a high bias voltage of -1800 V were applied in a pulse form for 1 second each (total 320 minutes) to form a film.

  The total thickness of the hard carbon film 4 was 2.7 μm, and the thickness per layer was about 3 nm. Silicon in the hard carbon film 4 was measured by EPMA quantitative analysis and had a content of 9.6 atomic% (equivalent to 20 mass%). The hydrogen content of the hard carbon film 4 was 1.5 atomic% as a result of measurement by the RBS / HFS method. The balance was carbon, which was about 88.9 atomic% (equivalent to about 80% by mass). Moreover, the oxygen content of the hard carbon film 4 was 0.3 atomic% as a result of measurement by semi-quantitative EDX. Others are inevitable impurities.

As shown in Table 1, the sp ² component ratio was measured at 10 points equally spaced in the thickness direction of the film. As a result, the sp ² component ratio was in the range of 45% to 56%, and the average was 55%. In Table 1, the peak area (near 285 eV), the peak area (280 to 310 eV), and the sp ² peak area ratio are also shown.

The hard carbon film 4 made of the laminated film shown in FIG. 6 has a thin white layer (having a thickness of about 5 nm) periodically. This white layer has an sp ² component ratio (sp ² / (sp ² + sp ³ )) was a sp ² component rich layer with 50% or more and 60% or less. This white layer is a layer having a richer graphite structure than a diamond structure, and is considered to have an effect of improving the film toughness of the hard carbon film 4. As described above, this white layer is periodically formed in the process of forming a laminated film by applying a pulse of a low bias voltage of −150 V and a high bias voltage of −1800 V to the hard carbon film 4 − It is formed by extending the application time of the bias voltage of 1800V.

  The macro particle area ratio appearing on the surface of the hard carbon film 4 was 0.8%. FIG. 5 is a surface photograph showing macro particles of the hard carbon film 4. The obtained hard carbon film 4 had a Vickers hardness of 1273HV0.05. For the measurement, a Vickers hardness tester (manufactured by Futuretec Co., Ltd.) was used. Moreover, the indentation hardness HIT (15 mN load) which is the surface hardness of the hard carbon film 4 when measured using nanoindentation manufactured by Elionix Co., Ltd. was 13 GPa.

[Example 2]
In Example 1, a carbon target containing 5 atomic% of silicon was used. Other than that was carried out similarly to Example 1, and obtained the piston ring of Example 2. FIG.

The total thickness of the hard carbon film 4 was 3.0 μm, and the thickness per layer was about 5 nm. Silicon in the hard carbon film 4 was measured by EPMA quantitative analysis and had a content of 6.3 atomic%. The hydrogen content of the hard carbon film 4 was 1.3 atomic% as measured by the RBS / HFS method. Moreover, the oxygen content of the hard carbon film 4 was 1.0 atomic% as a result of measurement by semi-quantitative EDX. Others are inevitable impurities. Hard carbon film 4 composed of a laminated film, as in Example 1, as shown in Figure 6, although regularly thin white layer (thickness of about 5nm longitudinal) were present, the white layer be sp ² The sp ² component-rich layer having a component ratio (sp ² / (sp ² + sp ³ )) of 50% or more and 60% or less. The macro particle area ratio appearing on the surface of the hard carbon film 4 was 1.7%. The obtained hard carbon film 4 had a Vickers hardness of 1338HV0.05. The indentation hardness HIT (15 mN load) of the hard carbon film 4 was evaluated in the same manner as in Example 1 and was 14 GPa.

[Example 3]
In Example 1, a carbon target containing 2 atomic% of silicon was used. Other than that was carried out similarly to Example 1, and obtained the piston ring of Example 3. FIG.

The total thickness of the hard carbon film 4 was 3.0 μm, and the thickness per layer was about 10 nm. Silicon in the hard carbon film 4 was measured by EPMA quantitative analysis and had a content of 3.8 atomic%. The hydrogen content of the hard carbon film 4 was 1.3 atomic% as measured by the RBS / HFS method. In addition, the oxygen content of the hard carbon film 4 was 1.2 atomic% as a result of measurement by semi-quantitative EDX. Others are inevitable impurities. Hard carbon film 4 composed of a laminated film, as in Example 1, as shown in FIG. 6, but regularly thin white layer (thickness of about 5nm longitudinal) were present, the white layer be sp ² The sp ² component-rich layer having a component ratio (sp ² / (sp ² + sp ³ )) of 50% or more and 60% or less. The macro particle area ratio appearing on the surface of the hard carbon film 4 was 1.1%. The obtained hard carbon film 4 had a Vickers hardness of 1480 HV0.05. The indentation hardness HIT (15 mN load) of the hard carbon film 4 was evaluated in the same manner as in Example 1 and was 15 GPa.

[Example 4]
In Example 1, a single layer film was formed by changing the film formation conditions without using a laminated film. Other than that was carried out similarly to Example 1, and obtained the piston ring of Example 4. FIG.

  Specifically, a silicon-containing hard carbon film 4 made of a single layer film was formed on the hard carbon base film 3 using the same arc ion plating apparatus. This film formation was performed with an arc current of 120 A and a predetermined bias voltage (−1800 V) applied. The thickness of the hard carbon film 4 made of a single layer film was 2.7 μm. Silicon in the hard carbon film 4 was measured by EPMA quantitative analysis and had a content of 9.3 atomic%. The hydrogen content of the hard carbon film 4 was 1.5 atomic% as a result of measurement by the RBS / HFS method. Further, the oxygen content of the hard carbon film 4 was 1.5 atomic% as a result of the semi-quantitative measurement of EDX. Others are inevitable impurities. Since the hard carbon film 4 is a single layer film, there is no white layer as shown in FIG. The macro particle area ratio appearing on the surface of the hard carbon film 4 was 5.0%. The Vickers hardness of the obtained hard carbon film 4 was 1100HV0.05. The indentation hardness HIT (15 mN load) of the hard carbon film 4 was evaluated in the same manner as in Example 1 and was 11 GPa.

[Reference Example 1]
In Example 1, the hard carbon base film 3 and the hard carbon film 4 were formed using a carbon target not containing silicon. Other than that was carried out similarly to Example 1, and obtained the piston ring of the reference example 1. FIG.

The total thickness of the hard carbon film 4 was 4.7 μm, and the thickness per layer was about 0.2 nm. The hard carbon film 4 did not contain silicon. The hydrogen content of the hard carbon film 4 was 0.3 atomic% as measured by the RBS / HFS method. Further, the oxygen content of the hard carbon film 4 was 0 atomic% as a result of measurement by semi-quantitative EDX. Others are inevitable impurities. The sp ² component ratio was measured at two points, and was 52% at the analysis point on the surface side. The macro particle area ratio appearing on the surface of the hard carbon film 4 was 3.1%. The Vickers hardness of the obtained hard carbon film 4 was 1710HV0.05. The indentation hardness HIT (15 mN load) of the hard carbon film 4 was evaluated in the same manner as in Example 1 and was 18.5 GPa.

[Measurement of sp ² component ratio]
The sp ² component ratio was calculated by the following procedures (1) to (5). (1) An EELS spectrum is measured with an EELS analyzer (manufactured by Gatan, Model 863 GIF Tridiem). For the measured EELS spectrum, a pre-peak is fitted with a linear function, a post-peak is fitted with a cubic function, and the peak intensity is normalized. (2) After that, the diamond data and the graphite data are compared, and the energy calibration is performed by aligning the peak start positions. (3) An area within the range of 280 eV to 310 eV is obtained for the calibrated data. (4) Two peaks in the range of 280 eV to 295 eV (one is a peak of sp ² and the other is a peak of CH or amorphous) and a peak area near 285 eV is obtained. (5) The area ratio of the area in the range of 280 eV to 310 eV in (3) above and the peak area in the vicinity of 285 eV in (4) above is taken. For this area ratio, graphite is set to 100, diamond is set to 0, and the sp ² component ratio is obtained from the relative value. The value obtained in this way was used as the sp ² component ratio. Ten locations were analyzed at equal intervals in the thickness direction of the hard carbon film 4.

[Friction and wear test (SRV test)]
On the surface (outer peripheral sliding surface 11) of the piston ring base material 1 (equivalent to SWOSC-V material of JIS standard, material of Example 1) having a ring diameter of φ80 mm, Cr— An N film (abrasion resistant film), a titanium film (undercoat film 2), a hard carbon undercoat film 3, and a hard carbon film 4 were sequentially formed. The obtained sample was subjected to a frictional wear test (SRV test / Schwingungs Reihungund und Verschleiss) in the manner shown in FIG. 7, and the presence or absence of abrasion was observed. In addition, μ (coefficient of friction between the object and the sliding surface) was measured.

  The test conditions are as follows. The piston ring was cut into a length of 20 mm and used as a sliding side test piece (pin type test piece) 20. As the counterpart test piece (disk type test piece) 21, a test piece having a diameter of 24 mm and a length of 7.9 mm (hardness HRC 62 or more) was cut out from SUJ2 steel defined as a high carbon chromium bearing steel in JIS G4805. The SRV test was conducted under the following conditions. In addition, the code | symbol Y in FIG. 7 showed the sliding direction, and the sliding width of the sliding direction was 3 mm.

・ Test equipment: SRV test equipment (see Fig. 7)
・ Load: 500N, 1000N
・ Frequency: 50Hz
Test temperature: 80 ° C
・ Sliding width: 3mm
・ Lubricant: 5W-30, 125mL / hr
・ Test time: 10 minutes, 60 minutes, 120 minutes

  The obtained friction coefficient μ is shown in Table 2. The coefficient of friction μ was evaluated at a test time of 60 minutes. From the results in Table 2, it can be seen that the friction coefficient μ decreases when silicon is contained.

  FIG. 8 is a photograph showing the SRV test results. FIG. 8A shows the test result of 10 minutes at 1000 N using the sample of Example 1. FIG. 8B is a test result for 60 minutes at 1000 N using the sample of Example 1. FIG. 8C shows a test result of 120 minutes at 1000 N using the sample of Example 1. FIG. 8D shows the test result of 10 minutes at 1000 N using the sample of Reference Example 1. In the sample of Example 1, although the thickness was as thin as 2.7 μm, the abrasion did not progress even at a test of 1000 N for 120 minutes, the friction (mechanical friction loss) was low, and the wear resistance was extremely excellent. showed that. On the other hand, the sample of Reference Example 1 was not worn in the test at 500 N for 10 minutes and showed high wear resistance, but was worn in the test at 1000 N for 10 minutes.

  FIG. 9 is a photograph showing the results of forced wear with a slurry containing diamond particles having an average particle diameter of 0.25 μm in the SRV test shown in FIG. 7. FIG. 9A shows the test result of 3 minutes at 20 N using the sample of Example 1. FIG. 9B is a test result for 3 minutes at 20 N using the sample of Reference Example 1. The sample of Example 1 showed excellent durability without swelling or peeling.

  The Vickers hardness of the hard carbon film 4 in Example 1 was 1273 HV0.05, whereas the Vickers hardness of the hard carbon film 4 in Reference Example 1 was 1710 HV0.05. Although it is considered that the hard carbon film 4 in Example 1 contained silicon and the hardness was lowered, the friction (mechanical friction loss) was low and the wear resistance was excellent, so that the toughness was improved. It is thought that.

DESCRIPTION OF SYMBOLS 1 Piston ring base material 2 Base film 3 Hard carbon base film 4 Hard carbon film 5 Outermost surface film 10, 10A, 10B, 10C, 10D Piston ring 11 Sliding surface (outer peripheral sliding surface)
12 upper surface 13 lower surface 14 inner peripheral surface 20 sliding side test piece (pin type test piece)
21 Counterpart test piece (disk type test piece)
P load

Claims (5)

Having a hard carbon film formed on at least the outer peripheral sliding surface of the piston ring substrate;
The hard carbon film is a laminated film or a single layer film, and contains silicon in the range of 2 atomic% to 12 atomic%, and the transmission electron microscope (TEM) has electron energy loss spectroscopy (EELS). A piston ring characterized in that the sp ² component ratio measured by a TEM-EELS spectrum in combination is a range of 40% to 80%.   The piston ring according to claim 1, wherein the hard carbon film has a hydrogen content of less than 5 atomic%. The piston ring according to claim 1, wherein the laminated film includes a white layer having a large sp ² component ratio.   The piston ring according to any one of claims 1 to 3, wherein a total thickness of the hard carbon film is in a range of 0.5 µm or more and 20 µm or less. The piston ring according to any one of claims 1 to 4, wherein the hard carbon film is formed on a hard carbon base film having a thickness in a range of 0.05 µm to 0.5 µm.