WO2017130587A1

WO2017130587A1 - Sliding member and production method therefor

Info

Publication number: WO2017130587A1
Application number: PCT/JP2016/087104
Authority: WO
Inventors: 勝啓辻
Original assignee: 株式会社リケン
Priority date: 2016-01-25
Filing date: 2016-12-13
Publication date: 2017-08-03
Also published as: JP2017133049A; JP6599251B2

Abstract

The present invention provides a sliding member, in which interlayer peeling is less likely to occur even under tough sliding conditions. The present invention is a sliding member 100 used with lubricating oil, and is characterized by having a base material 10, a first hard carbon layer 14 formed on the base material and not containing substantial amounts of hydrogen, and a second hard carbon layer 16 formed in contact with the first hard carbon layer and having a hydrogen content of 5-25 at.%, wherein the surface shape of the first hard carbon layer has a protruding peak height Rpk of 0.08-0.90 µm, and the thickness of the first hard carbon layer is 0.35-1.5 µm.

Description

Sliding member and manufacturing method thereof

The present invention relates to a sliding member, particularly a sliding member that requires high reliability, such as an automobile part, and a manufacturing method thereof.

In recent years, internal combustion engines such as automobile engines have been required to have higher output, longer life, and improved fuel efficiency. Therefore, for example, a hard carbon film that is known to have a low friction coefficient is generally formed on a sliding surface of a sliding member used in an internal combustion engine or the like. For this carbon film, amorphous carbon called diamond-like carbon (DLC) is used. The structural essence of DLC is a combination of diamond bonds (SP3 bonds) and graphite bonds (SP2 bonds) as carbon bonds. Therefore, DLC has hardness, wear resistance, thermal conductivity and chemical stability similar to diamond, while it has solid lubricity similar to graphite, which protects sliding members such as automobile parts. Suitable as a membrane. As the hard carbon film formed on the surface of the sliding member, one containing hydrogen (hereinafter referred to as “hydrogen-containing hard carbon layer”) and one not containing hydrogen (hereinafter referred to as “hydrogen-free hard carbon layer”). "). Although the hydrogen-containing hard carbon layer has a low friction coefficient, since a part of carbon bonding hands is terminated with hydrogen, there is a tendency that adhesion with a base material is poor. On the other hand, the hydrogen-free hard carbon layer has a high friction coefficient, but tends to be excellent in adhesion to the base material. There are the following conventional techniques combining these two.

In Patent Document 1, a hydrogen-free hard carbon layer is formed on a substrate by a vacuum arc ion plating method using a filtered cathode method, and an uppermost layer is formed on the hydrogen-free hard carbon layer by a plasma CVD method. It is described that a hydrogen-containing hard carbon layer having a hydrogen content of 0.17 to 0.34 atomic% is formed. This technique combines a low-wear property and excellent adhesion by combining a hydrogen-free hard carbon layer and a hydrogen-containing hard carbon layer. Since the hydrogen-free hard carbon layer is formed by a vacuum arc discharge method using a filtered cathode method, the surface thereof has high flatness.

In Patent Document 2, a hydrogen-free hard carbon layer having a thickness of 0.5 to 200 nm is formed on a substrate by a vacuum arc ion plating method that does not use a filtered cathode method, and further, by a vacuum arc ion plating method. It describes that a hydrogen-containing hard carbon layer having a hydrogen content of 5 to 25 atomic% is formed on a hydrogen-free hard carbon layer. In the invention described in this document, the hydrogen-free hard carbon layer is formed by a vacuum arc ion plating method that does not use a filtered cathode method, but since the thickness is as thin as 200 nm or less, the surface has high flatness. It is characterized by having

JP 2000-128516 A JP 2003-26414 A

In Patent Documents 1 and 2, the adhesion between the entire hard carbon coating and the base material is improved by interposing a hydrogen-free hard carbon layer with high adhesion between the base material and the hydrogen-containing hard carbon layer. I was paying attention to. However, Patent Documents 1 and 2 do not consider any adhesion between the hydrogen-free hard carbon layer and the hydrogen-containing hard carbon layer thereon. According to the study of the present inventor, in the prior art, peeling occurs between the hydrogen-free hard carbon layer and the hydrogen-containing hard carbon layer under severe sliding conditions, and as a result, the service life of the sliding member is shortened. It turns out that there is a problem.

In view of the above problems, an object of the present invention is to provide a sliding member in which delamination hardly occurs even under severe sliding conditions and a method for manufacturing the same.

In Patent Documents 1 and 2, when forming a hydrogen-containing hard carbon layer on a hydrogen-free hard carbon layer, it has been aimed to make the surface of the hydrogen-free hard carbon layer as flat as possible. However, in order to achieve the above object, the present inventor has conceived of roughening the surface of the hydrogen-free hard carbon layer. That is, the present inventor aimed to suppress peeling between the two layers by an anchor effect due to the unevenness by forming a hydrogen-containing hard carbon layer on a hydrogen-free hard carbon layer having many unevenness on the surface. And not only simply roughening the surface of the hydrogen-free hard carbon layer, but also when the surface has a specific surface shape (uneven structure), it has been found that peeling between the two layers can be sufficiently suppressed. The invention has been completed.

That is, the gist configuration of the present invention is as follows.
(1) a base material;
A first hard carbon layer substantially free of hydrogen formed on the substrate;
A second hard carbon layer having a hydrogen content of 5 atomic% or more and 25 atomic% or less formed on the first hard carbon layer;
The surface shape of the first hard carbon layer satisfies a protruding peak height Rpk: 0.08 μm or more and 0.90 μm or less,
A sliding member used under lubricating oil, wherein the thickness of the first hard carbon layer is 0.35 µm or more and 1.5 µm or less.

(2) The sliding member according to (1), wherein the hydrogen content of the second hard carbon layer is more than 10 atomic% and not more than 20 atomic%.

(3) The sliding member according to (1) or (2), wherein a total thickness of the first hard carbon layer and the second hard carbon layer is 5 μm or more.

(4) An inclined layer in which the hydrogen content increases from the first hard carbon layer toward the second hard carbon layer between the first hard carbon layer and the second hard carbon layer. The sliding member according to any one of the above (1) to (3).

(5) Between the base material and the first hard carbon layer, an intermediate layer composed of one or more selected from Cr, Ti, Si and W, carbides, nitrides, and carbonitrides thereof, The sliding member according to any one of (1) to (4) above.

(6) Forming a first hard carbon layer having a thickness substantially not containing hydrogen of 0.35 μm or more and 1.5 μm or less on the substrate by a vacuum arc ion plating method that does not use the filtered cathode method. The first step,
Second step of forming a second hard carbon layer having a hydrogen content of 5 atomic% or more and 25 atomic% or less on the first hard carbon layer by a vacuum arc ion plating method that does not use a filtered cathode method When,
And the first step is performed so that the surface shape of the first hard carbon layer satisfies the protruding peak height Rpk: 0.08 μm or more and 0.90 μm or less. Manufacturing method of sliding member used.

The sliding member of the present invention hardly causes delamination even under severe sliding conditions. Moreover, the manufacturing method of the sliding member of this invention can manufacture the sliding member which is hard to produce delamination under severe sliding conditions with high productivity.

It is a schematic cross section of the sliding member 100 by one Embodiment of this invention. In one embodiment of the present invention, it is a schematic diagram of a film forming apparatus used for forming a first hard carbon layer and a second hard carbon layer. In FIG. 2, it is a figure explaining the condition which forms the 2nd hard carbon layer (hydrogen containing hard carbon layer) 16 into a film. It is a typical graph which shows the time-dependent change of the thickness of the 2nd hard carbon layer (hydrogen containing hard carbon layer) in the work holder A of FIG. 3, and the flow volume of hydrocarbon type gas. It is a schematic diagram which shows the form of a reciprocating sliding test. (A) is a schematic graph explaining the method of measuring the surface shape of a hard carbon film in an experimental example, (B) explains the method of calculating the wear part cross-sectional area of a hard carbon film in an experimental example. It is a schematic graph.

(Sliding member)
Referring to FIG. 1, a sliding member 100 according to an embodiment of the present invention is used under lubricating oil, and is formed on a base material 10 and a surface (sliding surface side) of the base material. The intermediate layer 12, the first hard carbon layer 14 (hydrogen-free hard carbon layer) substantially free of hydrogen formed on the intermediate layer, and the first hard carbon layer in contact therewith And a second hard carbon layer 16 (hydrogen-containing hard carbon layer) having a hydrogen content of 5 atomic% to 25 atomic%. In the present specification, the first hard carbon layer 14 and the second hard carbon layer 16 as well as any gradient layer described later are collectively referred to as a “hard carbon coating 18”.

(Base material)
The material of the base material 10 is not particularly limited as long as it has a strength necessary for the base material of the sliding member. When the sliding member 100 of the present embodiment is a piston ring, preferable materials for the substrate 10 include steel, martensitic stainless steel, austenitic stainless steel, high-grade cast iron, and the like.

(Middle layer)
The intermediate layer 12 has a function of relaxing the stress at the interface with the base material 10 and improving the adhesion of the hard carbon film 18 by being formed between the base material 10 and the hard carbon film 18. From the viewpoint of exerting this function, the intermediate layer 12 is preferably made of one or more selected from Cr, Ti, Si and W, carbides, nitrides, and carbonitrides thereof. The intermediate layer is not limited to a single layer made of a metal or a compound selected from the above, and may have a multilayer structure in which a plurality of layers are stacked. The thickness of the intermediate layer 12 is preferably 0.02 μm or more and 0.6 μm or less. If the thickness is less than 0.02 μm, sufficient adhesion to the hard carbon coating 18 may not be obtained. If the thickness exceeds 0.6 μm, plastic flow tends to occur, and the intermediate layer 12 It is because it becomes easy to peel.

Examples of the method for forming the intermediate layer 12 include a sputtering method. The substrate 10 after cleaning is placed in a vacuum chamber of a PVD film forming apparatus, and Ar gas is introduced, using a sputtering source 22 (see FIG. 2) having a Cr, Ti, or WC target. Layer 12 can be deposited. When SiC is formed as the intermediate layer, a hydrocarbon gas containing Si as a constituent element such as tetramethylsilane (TMS) is introduced, and the intermediate layer 12 can be formed by plasma CVD. In this case, the sputtering source 22 is not used. The thickness of the intermediate layer 12 can be adjusted by the discharge time.

(Hard carbon coating)
The hard carbon coating 18 is in contact with the substrate 10 or preferably the first hard carbon layer 14 formed in contact with the intermediate layer 12 and the first hard carbon layer 14 formed in contact with the first hard carbon layer. Two hard carbon layers 16.

The first hard carbon layer 14 does not substantially contain hydrogen and consists of amorphous carbon (DLC) only. Amorphous carbon can be confirmed by Raman spectrum measurement using a Raman spectrophotometer (Ar laser). Here, in the present invention, “substantially does not contain hydrogen” means a gas that is inevitably generated during film formation, or gas that is adsorbed on the inner wall of the film formation chamber as it is released during film formation. This means that the first hard carbon layer 14 is formed without introducing a compound containing hydrogen, such as methane, diborane, and silane, from the outside, specifically, by HFS (Hydrogen-Forward-Scattering) analysis. It means that the hydrogen content in the hard carbon coating is 3 atomic% or less. The first hard carbon layer 14 increases the adhesion between the base material 10 and the intermediate layer 12 and the hard carbon coating 18.

The second hard carbon layer 16 has a hydrogen content of 5 atomic% to 25 atomic%. Within this range, wear acceleration during sliding in an oil lubrication environment containing an organomolybdenum compound is small, and a high film formation rate can be achieved at the same time. The hydrogen content is preferably more than 10 atomic% and not more than 20 atomic%. When the hydrogen content is less than 5 atomic%, the wear resistance is good, but the deposition rate is slow and the productivity is low. On the other hand, when the hydrogen content exceeds 25 atomic%, a high film formation speed can be obtained, but there is a large amount of wear and wear by organic molybdenum compounds may be promoted. Not suitable for use in

Here, in the present invention, the surface shape of the first hard carbon layer 14 (that is, the shape of the interface between the first hard carbon layer 14 and the second hard carbon layer 16) is the protruding peak height Rpk: 0.08. It is important to satisfy the range of μm to 0.90 μm. When Rpk is less than 0.08 μm, peeling between the first hard carbon layer 14 and the second hard carbon layer 16 occurs, and as a result, the service life of the sliding member is shortened. On the other hand, if Rpk exceeds 0.90 μm, the surface roughness of the second hard carbon layer 16 formed on the first hard carbon layer 14 becomes too large, and post-processing is required. From the above viewpoint, Rpk is preferably 0.08 μm or more and 0.55 μm or less.

Here, an example of a method for measuring and determining the thickness of the intermediate layer, the first hard carbon layer, the second hard carbon layer, and the Rpk of the surface of the first hard carbon layer is shown below. A cross-sectional sample in the film thickness direction of the hard carbon coating 18 is manufactured by focused ion beam (FIB) processing, and a transmission electron microscope image (TEM image) is observed. The cross-sectional shape of the base material is the boundary between the base material and the intermediate layer, the cross-sectional shape of the intermediate layer is the boundary between the intermediate layer and the first hard carbon layer, and the cross-sectional shape of the first hard carbon layer is the first hard The change in luminance of the obtained TEM image is the boundary between the carbon layer and the second hard carbon layer, the cross-sectional shape of the second hard carbon layer is the surface of this layer or the boundary with the protective layer provided before FIB processing. Ask for. Specifically, the surface shape (cross-sectional shape) of the base material, the intermediate layer, the first hard carbon layer, and the second hard carbon layer, with the location where the luminance change becomes ½ as the boundary between adjacent layers And

First, the calculation method of the thickness of each layer is as follows. A regression line is obtained by the least square method for each measurement point constituting the cross-sectional shape of the substrate, and this straight line is taken as the x-axis and the normal direction as the y-axis. And the coordinate of the measurement point of each cross-sectional shape of an intermediate | middle layer, a 1st hard carbon layer, and a 2nd hard carbon layer is converted into xy coordinate defined here. At this time, the height of the cross-sectional shape of each layer from the base material is the average value of the y-coordinates of the respective cross-sectional shapes. Accordingly, the thickness of the intermediate layer is calculated from the average value of the y coordinates of the cross-sectional shape of the intermediate layer from the x axis. Similarly, the thickness of the first hard carbon layer is calculated by subtracting the thickness of the intermediate layer from the average value of the y coordinates of the cross-sectional shape of this layer, and the thickness of the second hard carbon layer is It is calculated by subtracting the average value of the y-coordinates of the cross-sectional shape of the first hard carbon layer from the average value of the y-coordinates of the cross-sectional shape.

The Rpk of the surface of the first hard carbon layer is calculated based on the cross-sectional shape of the obtained first hard carbon layer using surface roughness measurement software or the like according to JIS B0671-2: 2002.

The first hard carbon layer 14 and the second hard carbon layer 16 are formed by an ion plating method by vacuum arc discharge using a carbon target without using a filtered cathode method. When the first hard carbon layer 14 is formed by evaporating and ionizing a carbon cathode (made of graphite) using vacuum arc discharge, carbon fine particles (drops) released from the cathode along with the arc discharge A lett) is taken into the first hard carbon layer to form a convex portion on the surface thereof. In the present invention, it is important to obtain a convex structure satisfying the above Rpk by employing predetermined film forming conditions.

With reference to FIGS. 2 to 4, the film formation of the first hard carbon layer 14 and the second hard carbon layer 16 in this embodiment will be described.

As shown in FIGS. 2 and 3, in a film forming apparatus having a certain scale of productivity, an arc evaporation source 20 having a carbon cathode and a sputtering source 22 having a metal cathode for forming an intermediate layer are turned. It is often arranged in a positional relationship facing each other across the table. This is because, for example, when the arc evaporation source 20 having a carbon cathode is discharged and formed into a film, the turntable can be used as a screen to suppress the coating of the sputtering source Cr, such as Cr, with the carbon surface by carbon. It is. When forming a film on a non-planar substrate having a generally rotationally symmetric shape such as a piston ring, it is common to use a multi-axis turntable having a plurality of rotational axes that rotate and revolve ( Figures 2 and 3).

An arc-type evaporation source 20 having a carbon cathode is operated to form a first hard carbon layer 14 not containing hydrogen having a predetermined thickness. Thereafter, a hard carbon layer containing hydrogen is subsequently formed. At that time, a hydrocarbon gas such as methane or acetylene is introduced from a gas introduction path (not shown) while maintaining the discharge in order to maintain the continuity of the film formation.

At this time, it is preferable to control the flow rate of the hydrocarbon-based gas so as to increase with the lapse of time so as not to cause a sudden change in film quality, and thereafter to maintain a constant flow rate. Thereby, an inclined layer in which the hydrogen content increases from the first hard carbon layer 14 toward the second hard carbon layer 16 between the first hard carbon layer 14 and the second hard carbon layer 16 is provided. Can be formed.

The coating on the surface of the workpiece fixed to the workpiece holder 28 (the workpiece fixing jig having a rotation axis parallel to the rotation axis of the turntable) at the position A in FIG. Focusing on the formation, FIG. 4 schematically shows the relationship between the thickness of the coating formed on the surface of the workpiece located in the region P at the start of introduction of the hydrocarbon-based gas and the flow rate of the hydrocarbon gas. In the region P, the plasma generated by the arc evaporation source is shielded by the work of the other rotation axis located near the arc evaporation source, so that almost no film is formed.

When time passes and the region Q is exposed to the plasma generated by the arc evaporation source, film formation starts and the film thickness increases as the processing time elapses. When the region Q is shifted to the region P, the film formation is temporarily stopped. While this situation is repeated, film formation proceeds. For this reason, the rate of film formation before and after staying in the region Q and the ratio of the contribution of carbon released from the carbon cathode by the arc discharge forming the coating and the contribution from the hydrocarbon-based gas component are discontinuous, and thus formed. The film quality of the coated film becomes discontinuous. For this reason, a discontinuous interface tends to occur between the hard carbon layer that does not contain hydrogen and the hydrogen-containing hard carbon layer, and delamination occurs when used in harsh sliding environments such as piston rings There is.

In the present invention, when the surface shape of the first hard carbon layer 14 satisfies the protruding peak height Rpk: 0.08 μm or more and 0.90 μm or less, such delamination can be suppressed. From the viewpoint of forming such a surface shape, the conditions for forming the first hard carbon layer 14 are preferably as follows. That is, the bias voltage is preferably −150 V or more and 0 V or less, the arc discharge current is preferably 40 A or more and 90 A or less, and the substrate temperature before the first hard carbon layer 14 is formed is preferably 110 ° C. or less. 80 ° C. or lower is more preferable.

The thickness of the first hard carbon layer 14 can be controlled by the film formation time, and is 0.35 μm or more and 1.5 μm or less. This is because if the thickness is less than 0.35 μm, it is difficult to roughen the surface of the first hard carbon layer 14, so that it is difficult to make Rpk within the range of the present invention. On the other hand, when the thickness exceeds 1.5 μm, the surface of the first hard carbon layer 14 becomes too rough due to the carbon microparticles emitted from the cathode along with the arc discharge, and the carbon microparticles are integrated with the surrounding coating. This is because the boundary and voids (voids) are generated, and delamination occurs.

The conditions for forming the second hard carbon layer 16 are not particularly limited, but are preferably as follows. That is, the bias voltage is preferably −150 V to 0 V, the arc discharge current is preferably 40 A to 90 A, and the hydrocarbon gas flow rate is preferably 50 sccm to 250 sccm.

The total thickness of the first hard carbon layer 14 and the second hard carbon layer 16 is preferably 5 μm or more, and more preferably 7 μm or more. When the total thickness is 5 μm or more, it is possible to sufficiently obtain the effect of shortening the film formation rate compared to the case where all the thicknesses are assumed to be formed by the first hard carbon layer having a low film formation rate. it can. The total thickness is preferably 30 μm or less. Even if it exceeds 30 μm, there is no functional problem, but the film thickness is excessive and the film formation cost increases.

(Sliding member)
A sliding member according to an embodiment of the present invention includes a piston ring, a piston, a piston pin, a tappet, a valve lifter, and the like used for a sliding part of an internal combustion engine in which a lubricating oil containing an organic molybdenum compound such as engine oil is interposed. It can be applied to shims, rocker arms, cams, camshafts, timing gears, and timing chains.

The sliding member of the present invention is preferably used in the presence of a lubricating oil containing an organomolybdenum compound. Since the outermost layer has a hydrogen content of 5 to 25 at%, the progress of wear due to the reaction with the Mo oxide can be relatively suppressed even under lubricating oil containing an organomolybdenum compound.

The organomolybdenum compound in the lubricating oil is preferably one or more organomolybdenum compounds selected from molybdenum dithiocarbamate (Mo-DTC) or molybdenum dithiophosphate (Mo-DTP).

As a test piece, a SUJ2 cylinder having a diameter of 6 mm and a length of 12 mm was used as a base material, and an intermediate layer and a hard carbon film were formed on the curved surface as shown in the Examples and Comparative Examples described in Table 1 under the following conditions. The base material was arrange | positioned in the vacuum chamber of the film-forming apparatus provided with an arc type evaporation source as shown in FIG.

The film was formed not on the entire curved surface but on a part of the curved surface along the axial direction. The base material was held on the work holder 28 for film formation using the part where the film was not formed. The used turntable 26 has a plurality of work holders having rotation axes. C. D. Is 600 mm. A film-forming jig holding a substrate was attached to one of the axes. A dummy pole made of SUS304TPD of φ89 was disposed on the remaining rotation axis. The rotation speed of the turntable was 4 rpm, and the rotation axis was 4 × 127/23 = 22.1 rpm.

Prior to the formation of the hard carbon film, the SUJ2 cylinder is cleaned, evacuated after being placed on one rotating shaft of the turntable, and heated using a heater 30 within a temperature range of 200 ° C. or less. Urged the release of adsorbed components. Then, discharge cleaning and formation of an intermediate layer were performed.

After forming the intermediate layer, the first hard carbon layer was formed in the same chamber, and the second hard carbon layer was further formed. A graphite carbon cathode (carbon: 99 atomic% or more) was attached to the arc evaporation source. At the time of forming the second hard carbon layer, argon was mixed with acetylene as a hydrocarbon gas and introduced. The first hard carbon layer of the example has a bias voltage of −150 V or more and 0 V or less, an arc discharge current of 40 A or more and 90 A or less, and a substrate temperature before forming the first hard carbon layer: 110 ° C. or less for a predetermined time. It formed by performing film-forming. The first hard carbon layers of Comparative Example 1 and Comparative Example 2 were formed by changing the film formation time under the same conditions as in the above Examples. The second hard carbon layer of the example was formed by forming a film for a predetermined time under conditions of bias voltage: −150 V to 0 V, arc discharge current: 40 A to 90 A, and hydrocarbon gas flow rate: 50 sccm to 250 sccm. . The second hard carbon layers of Comparative Example 3 and Comparative Example 4 were formed with the hydrocarbon gas flow rate outside the stated range for the conditions of the above Examples.

(Evaluation of Rpk, film thickness, deposition rate)
Rpk on the surface of the first hard carbon layer was determined from the TEM image by the method described above. Moreover, the thickness of the intermediate | middle layer, the 1st hard carbon layer, and the 2nd hard carbon layer was calculated | required by the method as stated above using the same TEM image. The results are shown in Table 1. The film formation rate was calculated by dividing the thickness of the obtained hard carbon film by the film formation time. Formation of the whole of the first and second hard carbon layers (hard carbon coating) when the average value of the film formation rate of the first hard carbon layer in Examples 1 to 5 and Comparative Examples 1 to 4 is 1. The film speed is indexed and shown in Table 1.

(Measurement of hydrogen content of the second hard carbon layer)
The hydrogen content of the hard carbon film is measured by RBS (Rutherford Backscattering Spectrometry) / HFS (Hydrogen Forward Scattering Spectrometer) of a film formed in a region that is flat or has a sufficiently large radius of curvature and can be regarded as a flat surface for measurement.

First, the hydrogen content (unit: atomic%) in a film is measured by RBS / HFS on a plurality of reference samples on which a film with different hydrogen contents is formed on a plane. Next, the secondary ion intensity of each of hydrogen and carbon is measured for this reference sample by SIMS (Secondary Ion Mass Spectrometry: Secondary Ion-microprobe Mass Spectrometry). And carbon content is calculated | required from these ratios and the hydrogen content calculated | required by RBS / HFS.

As a reference sample, a carbon film was formed on a mirror-polished flat test piece (quenched SKH51 material disc, φ25 × thickness 5 (mm), hardness HRC60-63, surface roughness Ra 0.02 μm or less).

The film formation of the reference sample was performed using a reactive sputtering method and introducing acetylene, argon, and hydrogen as the atmospheric gas. The amount of hydrogen contained in the coating film of the first reference sample was adjusted by changing the flow rate of introduced hydrogen and the overall pressure. In this way, hard carbon films composed of only hydrogen and carbon and having different hydrogen contents were formed, and the carbon film compositions (all elements including hydrogen) of these reference samples were evaluated by RBS / HFS. Then, it was confirmed that the total of hydrogen and carbon was 98 atomic% or more among the components of the entire hard carbon film formed on the reference sample, and that carbon was 97 atomic% or more among the components excluding hydrogen.

Next, the coating of the reference sample was analyzed by SIMS, and the secondary ion intensity of hydrogen and carbon was measured. Here, the SIMS analysis can be performed on a non-planar part such as a piston ring or a camshaft. Therefore, for the same coating of the reference sample, an empirical formula showing the relationship between the amount of hydrogen and carbon (unit: atomic%) obtained by RBS / HFS and the ratio of secondary ion intensity of hydrogen and carbon obtained by SIMS. By obtaining the (calibration curve), the amount of hydrogen and the amount of carbon can be calculated from the SIMS hydrogen and carbon secondary ion intensity measured for the actual sliding member.

Next, the coating film formed on the actual sliding member was analyzed by SIMS, and the ratio between the hydrogen amount and the carbon amount was determined using the above empirical formula. In addition, the value of the secondary ion intensity by SIMS adopted the average value of the secondary ion intensity of each element observed at least at a depth of 20 nm or more from the coating surface and in the range of 50 nm. Further, elements other than hydrogen including carbon were further measured by EDX (Energy Dispersive X-ray spectroscopy) and WDX (Wavelength-dispersive X-ray spectroscopy). From these results, the composition ratio of the coating film containing hydrogen can be evaluated. The hydrogen content of the second hard carbon layer measured in this way is shown in Table 1.

(Evaluation of coating wear)
The surface on which the hard carbon film of the test piece prepared in the example and the comparative example was formed was polished with a wrapping film (diamond # 4000) so as to have an arithmetic average roughness Ra of 0.03 μm or less. A reciprocating test was performed.

FIG. 5 schematically shows the test piece of each example and comparative example using a sliding mating material (SUJ2 disc adjusted to a surface roughness Ra of 0.05 to 0.08 μm by polishing in a random direction). A reciprocating motion test was performed under the following test conditions by a vibration friction wear test (Optimol Co., Ltd .: SRV4 testing machine) shown in the figure, and a friction coefficient at the end of the test was measured.
Test time: 60 min
Load: 400N
Reciprocating frequency: 50Hz
Amplitude: 3 mm
Lubricating oil: Engine oil (OW-20 / organic Mo added oil) Lubricating oil temperature: 80 ° C

The amount of coating wear by such a reciprocating test was obtained by the following method. Using a confocal laser microscope (Olympus, model: LEXT OLS4000), the three-dimensional shape of the coating surface including the vicinity of the sliding portion after the reciprocating test was measured. First, the three-dimensional shape of the side surface of the cylinder on which the coating film before being subjected to the reciprocating test was formed was measured, and the surface shape in the vertical direction (sliding direction) with respect to the rotational symmetry axis of the cylinder was measured at 10 locations (FIG. 6 ( A)). And the average of the nth shape was calculated | required from the 1st shape. Ten points were similarly measured in the vicinity of the sliding portion after the test, and the average value of the surface shapes parallel to the sliding direction was obtained. From the difference between these shapes, the cross-sectional area of the coating worn by the reciprocating test was calculated (FIG. 6B). The results are shown in Table 1 as index values based on the coating wear amount of Example 1 as a reference (1.00).

(Evaluation of film damage)
The sliding surface (surface) of the test piece was observed visually or with an optical microscope (100 to 400 times), and the presence or absence of film damage was evaluated according to the following criteria. The case where pits with a size of 100 μm or more are observed on the sliding surface of the test piece is “pit missing”, and the case where the first hard carbon layer and the second hard carbon layer are separated is called “delamination”. Indicated.

As apparent from Table 1, when the surface shape of the first hard carbon layer satisfies the protruding peak height Rpk: 0.08 μm to 0.90 μm, the first hard carbon layer and the second hard carbon layer There was no separation between the two.

The sliding member of the present invention can reduce the coefficient of friction while maintaining high wear resistance during sliding under lubricating oil containing an organomolybdenum compound, and is less likely to cause delamination.

DESCRIPTION OF SYMBOLS 100 Sliding member 10 Base material 12 Intermediate layer 14 1st hard carbon layer (non-hydrogen containing hard carbon layer)
16 Second hard carbon layer (hydrogen-containing hard carbon layer)
18 Hard carbon coating 20 Arc type evaporation source with carbon cathode 22 Sputtering source with metal cathode 24 Vacuum vessel 26 Turntable 28 Rotating work holder 30 Heater 60 Test piece (SUS2 cylinder)
68 Sliding mating material (SUS2 disc)

Claims

A substrate;
A first hard carbon layer substantially free of hydrogen formed on the substrate;
A second hard carbon layer having a hydrogen content of 5 atomic% or more and 25 atomic% or less formed on the first hard carbon layer;
The surface shape of the first hard carbon layer satisfies a protruding peak height Rpk: 0.08 μm or more and 0.90 μm or less,
A sliding member used under lubricating oil, wherein the thickness of the first hard carbon layer is 0.35 µm or more and 1.5 µm or less.
The sliding member according to claim 1, wherein the hydrogen content of the second hard carbon layer is more than 10 atomic% and not more than 20 atomic%.
The sliding member according to claim 1 or 2, wherein a total thickness of the first hard carbon layer and the second hard carbon layer is 5 µm or more.
Between the first hard carbon layer and the second hard carbon layer, there is an inclined layer in which the hydrogen content increases from the first hard carbon layer toward the second hard carbon layer. Item 4. The sliding member according to any one of Items 1 to 3.
An intermediate layer made of one or more materials selected from Cr, Ti, Si, and W, carbides, nitrides, and carbonitrides thereof is provided between the base material and the first hard carbon layer. Item 5. The sliding member according to any one of Items 1 to 4.
First step of forming a first hard carbon layer having a thickness substantially not containing hydrogen of 0.35 μm or more and 1.5 μm or less on a substrate by a vacuum arc ion plating method without using a filtered cathode method When,
Second step of forming a second hard carbon layer having a hydrogen content of 5 atomic% or more and 25 atomic% or less on the first hard carbon layer by a vacuum arc ion plating method that does not use a filtered cathode method When,
And the first step is performed so that the surface shape of the first hard carbon layer satisfies the protruding peak height Rpk: 0.08 μm or more and 0.90 μm or less. Manufacturing method of sliding member used.