JP2010215950A - Sliding member and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sliding member which reduces the initial coefficient of friction of the amorphous carbon coating film and also can enhance its initial affinity, and to provide a method for manufacturing the same. <P>SOLUTION: This manufacturing method includes the steps of: forming the amorphous carbon coating film containing hydrogen on a surface of a substrate; and irradiating the surface of the amorphous carbon coating film with ultraviolet rays. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a sliding member having a hard carbon film formed on a sliding surface and a method for manufacturing the same, and more particularly to a sliding member excellent in initial conformability and a method for manufacturing the same.

  Traditionally, tribology has played an important role in Japanese key industries such as the automobile industry. For example, in the automobile industry, various efforts are currently being made to reduce carbon dioxide emitted from automobiles in order to protect the global environment. One example is the use of energy efficient power sources such as hybrid systems. Development is well known. However, in order to achieve further low fuel consumption, not only the development of the power source but also the reduction of energy transmission loss due to friction in the engine and in the drive system becomes an important issue.

  In view of such problems, the sliding surface of the sliding member made of structural steel or high alloy steel is coated in order to reduce the friction coefficient of the sliding member in power system equipment and to improve the wear resistance. Amorphous carbon material (DLC) is attracting attention as a new tribological material.

  As an example of the sliding member using such an amorphous carbon material, a sliding member in which an amorphous carbon film is formed on the surface of a base material, A sliding member containing at most hydrogen atoms, a sliding member containing 20 to 40 atomic% hydrogen atoms, and a sliding member containing 20 to 50 atomic% hydrogen atoms are disclosed. (For example, refer to Patent Documents 1 to 3). These sliding members can ensure the desired surface hardness and improve the adhesion strength of the coating by containing a predetermined proportion of hydrogen in the amorphous carbon coating.

JP 2005-3094 A JP 2005-314454 A JP 2005-336456 A

  However, even when such sliding members are used, it cannot be said that the initial familiarity of these sliding members is necessarily good in the atmosphere and in the lubricating oil. That is, when these sliding members are slid with the mating member, the friction coefficient tends to increase due to the influence of the surface undulation and the roughness of the sliding surface in the initial stage of sliding. . As a result, damage to the sliding surface of the sliding member (the surface of the amorphous carbon coating) also increases, and there is a concern that the friction coefficient may increase further and the amount of wear associated therewith may increase.

  The present invention has been made in view of such problems, and the object of the present invention is to improve initial conformability of the amorphous carbon coating in a sliding member on which the amorphous carbon coating is formed. An object of the present invention is to provide a sliding member that can be made and a manufacturing method thereof.

  In view of the above problems, the present inventors have intensively studied, and as a result, the initial conformability is improved by increasing the graphite structure on the surface of the amorphous carbon coating. We obtained new knowledge that the graphitization of this material is manifested by irradiating the carbon material with ultraviolet rays.

More specifically, an amorphous carbon material constituting an amorphous carbon film containing a hydrogen element generally has a diamond structure corresponding to sp ³ bonds, a graphite structure corresponding to sp ² bonds, and these bonds. According to the inventors' experiment, when the amorphous carbon film contains a hydrogen element, the surface layer of the amorphous carbon film is particularly affected by the irradiation energy of ultraviolet rays. Obtained new knowledge that it is easy to be transformed into a graphite structure.

  The present invention is based on the above-mentioned new knowledge of the inventors, and the manufacturing method of the sliding member according to the first aspect of the present invention forms an amorphous carbon film containing hydrogen on the surface of a substrate. And a step of irradiating the surface of the amorphous carbon film with ultraviolet rays.

  According to the present invention, by irradiating the surface of the amorphous carbon film formed (deposited) on the surface of the substrate with ultraviolet rays, the surface layer of the amorphous carbon film is graphitized. Thereby, since this surface layer contains more graphite structures compared with the other part of the amorphous carbon which has not performed ultraviolet irradiation, the initial familiarity of a sliding member can be improved. Moreover, since only the surface layer is graphitized, the strength of the amorphous carbon coating itself is ensured.

  Further, the manufacturing method of the sliding member according to the second invention is characterized in that an amorphous carbon film containing hydrogen is formed on the surface of the base material while irradiating the base material with ultraviolet rays. To do.

  According to the present invention, the film is formed while irradiating the surface of the substrate with ultraviolet rays, so the formed amorphous carbon film is compared with the amorphous carbon film formed without irradiating ultraviolet rays. , The graphite content can be increased. Further, compared with the first invention, the layer irradiated with ultraviolet rays (the layer containing a lot of graphite by the ultraviolet irradiation) can be thickened, so that it is difficult to wear during sliding and the friction coefficient of the sliding member is low. The state can be sustained. The base material in this another aspect may be a base material on which an amorphous carbon film whose surface is not irradiated with ultraviolet rays is formed in advance.

  Thus, in any of the above-described methods, the sliding member on which the amorphous carbon film containing hydrogen is formed has a layer in which at least the surface layer is irradiated with ultraviolet rays on the amorphous carbon film, That is, it can include a surface layer graphitized by irradiation with ultraviolet rays (when the film is formed while being irradiated with ultraviolet rays, the entire coating film contains more graphite).

  Further, “graphitization” here refers to a phenomenon in which at least a part of an amorphous structure or the like of an amorphous carbon material changes to a graphite structure. In addition, the “graphitized layer by ultraviolet rays” means that the amorphous carbon film is irradiated with ultraviolet rays, or is partially irradiated with graphite, or is not irradiated when the film is formed while being irradiated with ultraviolet rays. In some cases, it refers to a layer having an increased graphite content.

  In the case of forming a film while irradiating with ultraviolet rays, it is more preferable to form the film while intermittently irradiating with ultraviolet rays. According to the present invention, the amorphous carbon film formed by intermittently irradiating ultraviolet rays has a layer irradiated with ultraviolet rays (a layer graphitized by irradiation with ultraviolet rays) in the film thickness direction. , It will be laminated intermittently. That is, the formed amorphous carbon film is formed by alternately laminating a layer made of an amorphous carbon material irradiated with ultraviolet rays and a layer made of an amorphous carbon material not irradiated with ultraviolet rays. Become.

  When the film is formed in this manner, the layer made of the amorphous carbon material graphitized by irradiation with ultraviolet rays is a layer having excellent slidability, and the amorphous carbon material not irradiated with ultraviolet rays is used. Since the layer to be formed is a hard layer, the sliding member including these layers can improve wear resistance and slidability. Furthermore, since the layer irradiated with ultraviolet rays contains more graphite, the compressive stress generated in the amorphous carbon coating can be relaxed. Thereby, an amorphous carbon film having a larger film thickness can be formed as compared with the conventional methods.

  If the amorphous carbon material can be graphitized by the energy of ultraviolet rays by irradiation with ultraviolet rays, the wavelength, intensity, irradiation time, etc. of the ultraviolet rays are not particularly limited. According to these experiments, it is known that the graphite contained in the amorphous carbon film increases as the irradiation energy of the ultraviolet rays irradiated during film formation increases due to the intensity of the irradiated ultraviolet rays, the irradiation time, etc. By appropriately selecting these conditions, sliding characteristics, film thickness, film adhesion, and the like can be changed.

  However, in the manufacturing method of the sliding member according to the present invention, it is more preferable to perform the film formation while increasing the irradiation energy of the ultraviolet rays. In the amorphous carbon film thus formed, the graphite contained in the amorphous carbon film increases from the surface of the substrate toward the surface of the amorphous carbon film.

  As a method of increasing the irradiation energy of the ultraviolet ray, for example, a method of increasing the irradiation intensity (specifically, shortening the wavelength of the irradiated ultraviolet ray) while forming a film, or irradiating the ultraviolet ray under the same conditions, Examples include a method of increasing the irradiation amount to the layer to be formed by delaying the film formation rate (or interrupting the film formation once). As a result, there is a large amount of graphite in the vicinity of the sliding surface, so that the sliding characteristics are improved.Further, in the vicinity of the surface of the base material, there is less graphite compared to the vicinity of the sliding surface and it is harder. Therefore, the coating strength can be ensured.

In the manufacturing method of the sliding member according to the present invention, it is more preferable to irradiate the ultraviolet rays having a wavelength of 350 nm or less.
In the method for manufacturing a sliding member according to the present invention, the surface of the amorphous carbon coating is irradiated with ultraviolet light having a wavelength of 350 nm or less, more preferably 312 nm or less. By this, the graphitization can be expressed more favorably, and the initial friction coefficient of the sliding member is preferably lowered by the film formed with the wavelength of the irradiated ultraviolet ray being 350 nm or less, thereby reducing the initial wear. can do.

  In addition, according to the experiments described later by the inventors, it has been found that the amorphous carbon film is converted to graphitization by containing hydrogen in the amorphous carbon film, and the sliding member according to the present invention is manufactured. In the method, the amorphous carbon film is more preferably formed such that the hydrogen content contained in the amorphous carbon film is 3 to 35 atomic%.

  According to the present invention, an amorphous carbon film having a hydrogen content in such a range is formed on the surface of the substrate, the film strength is ensured, and graphitization of the amorphous carbon film is more favorably expressed. can do.

  According to the present invention, the sliding characteristics including the initial conformability of the amorphous carbon coating formed on the substrate surface can be easily improved.

The typical apparatus block diagram for manufacturing the sliding member of 1st and 2nd embodiment (forming a film). The typical apparatus for manufacturing the sliding member of 2nd embodiment (film-forming a film). (A) And (b) is a figure for demonstrating the manufacturing method of the sliding member which concerns on 1st embodiment type | system | group, (c) and (d) are sliding members which concern on 2nd embodiment type | system | group. The figure for demonstrating the manufacturing method of. It is a figure for demonstrating the elemental analysis of the surface of the amorphous carbon film by the Auger electron spectroscopy which concerns on Example 1 and 2, and Comparative example 1 and 2, (a) is a kinetic energy of the range of 150-500 eV. (B) is a diagram showing normalized strength in the range of kinetic energy 220 to 300 eV. The figure which showed the result of having measured the contact angle of the amorphous carbon film which concerns on Examples 1 and 2, and Comparative Examples 1 and 2. FIG. The figure which showed the result of having measured the surface free energy of the amorphous carbon film which concerns on Examples 1 and 2, and Comparative Examples 1 and 2. FIG. The figure for demonstrating a ball-on-on-disk friction tester. The figure which showed the relationship between the sliding cycle number (friction repetition number) which concerns on Example 1 and 2, and Comparative Examples 1 and 2 and a friction coefficient. The figure which showed the relationship between the sliding cycle number (friction repetition number) which concerns on Comparative Examples 3-6, and a friction coefficient. The figure which showed the relationship between the sliding cycle number (friction repetition number) which concerns on Example 3 and 4, and Comparative Examples 7 and 8, and a friction coefficient. Examples 5 and 6, by laser Raman spectroscopy according to the Comparative Examples 9 and 10, showing the measurement results of and I _{D /} I _G (peak position of G band) G position FIG. (A) is a schematic diagram of the amorphous carbon film formed by the film forming method of Comparative Example 12, and (b) is an amorphous carbon film formed by the film forming method of Example 8. (C) is a schematic diagram of an amorphous carbon film formed by the film forming method of Example 9, and (d) is a film formed by the film forming method of Example 10. FIG.

  The following two embodiments of the sliding member and the manufacturing method thereof according to the present invention will be described. FIG. 1 is a schematic configuration diagram of an apparatus for manufacturing the sliding members of the first and second embodiments (forming a film on a base material). Moreover, (a), (b) of FIG. 3 is a figure for demonstrating the manufacturing method of the sliding member which concerns on 1st embodiment. The manufacturing method of the sliding member according to the first embodiment includes a step of forming an amorphous carbon film on the surface of a substrate and a step of irradiating the surface of the formed amorphous carbon film with ultraviolet rays. These steps are included at least.

  First, the base material W of the sliding member is prepared. The material of the base material W is not particularly limited as long as the material has a surface hardness and a material that can ensure adhesion with the amorphous carbon coating during sliding, For example, base materials, such as steel, cast iron, aluminum, polymer resin, etc. can be mentioned.

  And the base material W is arrange | positioned in the film-forming apparatus (ion beam mixing apparatus) 100A. First, the surface of the substrate W is cleaned by the argon ion beam gun 52. Then, an amorphous carbon nitride film is formed on the surface of the substrate W using a film forming apparatus 100A as shown in FIG. 1 (film forming process). Specifically, as shown in FIG. 1, the base material in the chamber 50 is held so that the base material W faces the carbon target T, and argon ions are irradiated from the argon ion beam gun 51 to the carbon target T. The carbon target T is used as the carbon sputtered particle C, and the amorphous carbon film D is formed on the surface of the substrate W as shown in FIG. At this time, hydrogen can be contained in the amorphous carbon film D by introducing hydrogen gas into the chamber 50. At this time, film formation may be performed while irradiating an argon beam from the argon ion beam gun 52.

  Here, when forming the amorphous carbon film on the surface of the base material of the sliding member, the film is formed by physical vapor deposition (PVD) using vacuum deposition, sputtering, ion plating, ion beam mixing, or the like. Alternatively, a film may be formed by a chemical vapor deposition method (CVD) utilizing plasma treatment or the like using an apparatus 100B shown in FIG. The film forming method is not particularly limited as long as the amorphous carbon film can contain hydrogen atoms.

  In addition, an additive element such as Si, Ti, Cr, Fe, Mo, W, or B may be included in the amorphous carbon film during the film formation. By adding such an element, The surface hardness of the coating may be adjusted.

Further, it is more preferable to form the amorphous carbon film so that the hydrogen content contained in the amorphous carbon film is 3 to 35 atomic% during film formation. For example, when the film is formed by plasma CVD, the hydrogen content is a hydrocarbon-based reaction gas such as methane (CH ₄ ) or acetylene (C ₂ H ₂ ) as a reaction gas. The method is not particularly limited as long as the hydrogen content can be adjusted by a generally known method of adjusting the amount or the like.

  Next, by irradiating the surface of the amorphous carbon film D thus formed with ultraviolet rays UV from the ultraviolet irradiation device 60, as shown in FIG. The surface layer G of the coating D is graphitized. Thereby, the initial familiarity of the surface of the amorphous carbon film used as the sliding surface of a sliding member can be improved. That is, the initial friction coefficient of the sliding member can be lowered, and thereby the initial wear can be reduced. Moreover, since only the surface layer is graphitized, the strength of the amorphous carbon coating itself is ensured.

  Here, the ultraviolet irradiation device 60 generally has a wavelength of ultraviolet light in the range of 10 to 400 nm. Ultraviolet light having such a wavelength is low-pressure mercury lamp (wavelength: 185, 254 nm), high-pressure mercury lamp (wavelength: 302, 365, 436, 546, 577 nm) or an excimer laser (wavelength ArF: 193 nm, KrF: 249 nm, XeCl: 308 nm). In the present embodiment, it is more preferable to irradiate ultraviolet rays having a wavelength of 350 nm or less, more preferably 312 nm or less, in this range of wavelengths. In addition, as long as ultraviolet rays having a wavelength can be generated, the ultraviolet ray generator is not particularly limited.

  By irradiating the surface of the amorphous carbon film with ultraviolet light having such a wavelength, the surface layer of the film can be more suitably graphitized, and the initial friction coefficient of the sliding member can be reduced. Can do. In particular, by forming an amorphous carbon film having a hydrogen content in the above-mentioned range on the surface of the substrate, the film strength is ensured and the surface layer of the amorphous carbon film is more suitably expressed. be able to.

  The sliding member thus obtained is a sliding member in which an amorphous carbon film containing hydrogen is formed on the surface of a substrate, and this amorphous carbon film is formed by irradiation with ultraviolet rays. It will contain a graphitized surface layer.

  An intermediate layer made of silicon (Si) is provided on the surface of the substrate W in order to increase the adhesion between the substrate and the amorphous carbon coating before the amorphous carbon coating W is formed. Further, chromium (Cr), titanium (Ti), or tungsten (W) may be used instead of silicon.

  Next, the manufacturing method of the sliding member which concerns on 2nd embodiment is demonstrated. The second embodiment is different from the first embodiment in that the timing of irradiating ultraviolet rays is performed at the same time as the film formation, and the following detailed description is omitted for the other points.

  First, as necessary, as shown in FIG. 1, an amorphous carbon film D is formed on the surface of the substrate by sputtering. In addition, the base material which concerns on 2nd invention among this invention is a concept containing the base material in which this amorphous carbon film was formed.

  Next, as shown in FIG. 3 (c), while irradiating the surface of the base material on which the amorphous carbon coating D is formed with ultraviolet UV from the ultraviolet irradiation device 60, An amorphous carbon film (layer irradiated with ultraviolet rays) G containing hydrogen is formed by the carbon sputtered particles C. The amorphous carbon film G thus formed is a graphitized film having a higher graphite content than the amorphous carbon film D formed without being irradiated with ultraviolet UV. It is thicker than the graphitized surface layer of the first embodiment. As a result, not only the initial familiarity but also the sliding characteristics of the sliding member can be continuously maintained for a long time as compared with the conventional sliding member on which the amorphous carbon film is formed.

  In addition, as a modification of the present embodiment, for example, as illustrated in FIG. Specifically, in the film forming step, ultraviolet rays are periodically irradiated in a pulse shape. As a result, the amorphous carbon film formed by intermittently irradiating with ultraviolet rays has a graphitized layer (layer irradiated with ultraviolet rays) G that is intermittently irradiated in the film thickness direction. Will be laminated.

  Along with the film thickness direction of the amorphous carbon film, a layer (G layer irradiated with ultraviolet rays) G by irradiation with ultraviolet rays and a layer (layer not irradiated with ultraviolet rays) D with less graphite compared to this are obtained. And are stacked alternately. When the film is formed in this manner, the layer G that has been graphitized by irradiation with ultraviolet rays can relieve the compressive stress generated in the film, so that it is thicker than conventional methods. An amorphous carbon film can be formed.

  As another aspect, the film may be formed while increasing the irradiation energy of ultraviolet rays according to the film formation. For example, this can be achieved by shortening the wavelength of the ultraviolet rays irradiated during film formation stepwise. The amorphous carbon film thus formed can increase the graphite contained in the amorphous carbon film from the surface of the substrate toward the surface (sliding surface) of the amorphous carbon film. it can.

  In the second embodiment, the film is formed by the film forming apparatus 100A shown in FIG. 1, but the film may be formed by the film forming apparatus 100B shown in FIG. A film forming apparatus 100B shown in FIG. 2 is a direct-current plasma CVD apparatus. A hydrocarbon-based gas such as methane gas is introduced into a chamber 55, and an electrode 57 and a substrate W are connected to a direct-current power source 56. While the plasma is generated during this period, a film is formed on the surface of the substrate W by the plasma CVD method.

  At this time, film formation is performed while irradiating the surface of the substrate W with ultraviolet UV from the ultraviolet irradiation device 60 through the window 58 of the chamber 55. Thereby, a graphitized layer can be obtained by irradiation with ultraviolet rays. As described above, the irradiation with ultraviolet UV can form a desired film by appropriately setting the wavelength (ultraviolet intensity), the irradiation time (irradiation timing), and the like. The window 58 may be any material that can transmit ultraviolet rays UV such as quartz, zinc selenide, potassium bromide, and the like.

Hereinafter, the present invention will be described by way of examples.
Example 1
<Manufacture of disk test piece (sliding member)>
As a sliding member according to the present invention, the following disk test piece was manufactured. Specifically, as a substrate for forming an amorphous carbon film, a disk-shaped silicon wafer having a diameter of 50 mm, a thickness of 0.3 mm, and a circular surface (sliding surface) in a mirror state (100 plane orientation) S was prepared. Then, an amorphous carbon film (H-DLC film) containing hydrogen having a hydrogen content of 13 atomic% and a layer thickness of 1.8 μm was formed on the surface of the substrate by plasma CVD. This corresponds to the trade name HT-DLC (hydrogen-containing DLC, manufactured by Nippon IT Co., Ltd., hydrogen content 13 atomic%). In Example 1 and the examples shown below, the hydrogen content is measured and confirmed by RBS (Rutherford backscattering analysis).

  Next, a bilink (BLX-312, manufactured by Cosmo Bio Inc.) is used as a light source for generating ultraviolet rays, and a discharge tube (CST-8C) having a spectral peak at an ultraviolet wavelength of 254 nm is used. A disk test piece was manufactured by irradiating the amorphous carbon film formed on the surface of the substrate with ultraviolet rays having a wavelength of 254 nm for 30 minutes. The maximum UV irradiation energy is 0 to 99.99 Joules, and the irradiation range is 260 mm × 300 mm. The atmosphere in the lamp house is air, and the distance from the lamp to the coating surface is 160 mm.

[Evaluation test]
<Atom composition analysis by Auger electron spectroscopy (AES)>
In order to clarify the change of the atomic composition of the amorphous carbon film by ultraviolet irradiation, analysis was performed by Auger electron spectroscopy. This Auger electron spectroscopy is a technique for irradiating a solid sample held in an ultra-high vacuum with an electron beam, detecting the Auger electrons that are generated, and performing elemental analysis of the surface, in particular, the very minute surface. Since only Auger electrons generated at a depth of up to several nanometers near the solid surface can escape, analysis of the pole surface is possible. In this example, an elemental analysis of the surface of the amorphous carbon film was performed using an Auger electron spectroscopic analyzer manufactured by Perkin-Elmer under the conditions of an acceleration voltage of primary electrons of 5 kV and a current of 100 nm. The analysis results are shown in FIG.

  4A shows the normalized intensity in the range of kinetic energy 150 to 500 eV, and FIG. 4B shows the normalized intensity in the range of kinetic energy 220 to 300 eV. As a reference example, highly oriented graphite (HOPG) was prepared and analyzed by the same method in order to clarify the structural change accompanying ultraviolet irradiation. The analysis results are also shown in FIG.

<Measurement of hardness test and Young's modulus>
A micro indentation hardness test of the amorphous carbon coating of the disk specimen was performed using an ultra micro indentation hardness tester ENT-1100a manufactured by Elionix. Specifically, a triangular pyramid diamond indenter (Berkovich indenter) with a ridge degree of 115 ° is used as the indenter, and the silicon surface of the disk specimen is fixed with an adhesive, and is left until the adhesive is dry. The test was conducted. In the indentation test of the amorphous carbon film, the indentation load was set to 10 mgf so that the base material of the test piece was not affected, and the indentation load was set to 1/10 or less of the film thickness. Thereby, hardness and Young's modulus were measured. The results are shown in Table 1.

<Measurement of surface roughness>
Using an atomic force microscope (AFM), the surface roughness of the amorphous carbon coating of the disk specimen was measured. An atomic force microscope is capable of observing irregularities on the surface of a sample with a resolution at the nanometer level by utilizing the force acting between the sample and the probe. The apparatus includes a measuring head (NPX100 manufactured by Seiko Instruments Inc.) and a controller (Nanopocs1000 manufactured by Seiko Instruments Inc.). Measurement can be performed at a measurement range of 0.5 nm to 1000 μm and a scanning speed of 12 to 1792 seconds / frame. Table 2 shows the centerline average roughness Ra and the maximum height roughness Ry of the coating surface obtained by this measurement.

<Measurement of surface free energy>
The contact angle and surface free energy of the amorphous carbon coating on the disk specimen were measured. The surface free energy represents the degree of activity of the solid surface, and droplets of water (H ₂ O) and methylene iodide (CH ₂ I ₂ ) (two different types of liquids) are applied to the surface of the solid sample. It was calculated by dropping and measuring the angle formed by each liquid and the solid sample (coating of the disk test piece) and the contact angle. The contact angle α was measured by a droplet method. The droplet diameter d and the droplet height h were measured, and the contact angle was calculated from these values. As a result, the contact angle is shown in FIG. 5, and the surface free energy is shown in FIG.

<Friction test>
The friction test was conducted according to the following procedure. First, a silicon nitride sphere having a diameter of 8 mm and shown in Table 1 below was prepared.

  A ball-on-disk friction tester shown in FIG. 7 was used. As a preliminary preparation for the wear test, the ball specimen B was ultrasonically cleaned with acetone and ethanol for 10 minutes each. Thereafter, the ball test piece B is fixed to the ball holder 35 removed from the main body of the testing machine, and after confirming that there is no scratch on the surface using an optical microscope (not shown), these are desiccators (not shown). The ball test piece B was dried. On the other hand, foreign matter such as dust on the surface (sliding surface) of the amorphous carbon coating formed on the surface of the disk test piece P was removed by hand blow (not shown).

  Next, the disc test piece P was held by the disc holder 44, and the ball holder 35 to which the ball test piece B was fixed was attached to the main body of the testing machine so as to be integrated with the stage 31. Using a strain gauge 33 (manufactured by Kyowa Denki Co., Ltd., KF-1-120-C1-16) bonded to the parallel leaf spring 32, the ball specimen B is against the surface of the amorphous carbon coating of the disk specimen P. The stage 31 was adjusted so that a load having a load value of 0.1 N was applied, and these were brought into contact with each other. The contact position between the ball test piece B and the disk test piece P was determined by the triaxial stage 31, and the vertical load was adjusted by moving the z axis up and down.

The motor 41 is driven and the pulley 42 is rotated under dry conditions (dry friction conditions) in the atmosphere (conditions shown in the figure), and the disk test piece P of the disk holder 44 is subjected to the ball test via the belt 43. The piece B was rotated under constant speed rotation conditions where the relative speed (sliding speed) was 8.4 × 10 ⁻² m / s (rotation speed: 400 rpm).

  The frictional force at this time was measured with the strain gauge 34, and data was taken in and recorded in the computer via the sensor interface (PCD-300A, manufactured by Kyowa Denki Co., Ltd.). And the friction coefficient was converted. The result is shown in FIG.

(Example 2)
A disk test piece was produced in the same manner as in Example 1. The difference from Example 1 is that an amorphous carbon film is irradiated with ultraviolet light having a wavelength of 321 nm using a discharge tube (CST-8B) having a spectral peak at a wavelength of 321 nm. Then, a series of evaluation tests were performed on these as in Example 1. The results are shown in FIGS. 4 to 6 and 8 and Tables 1 and 2.

(Comparative Example 1)
A disk test piece was produced in the same manner as in Example 1. The difference from Example 1 is that the amorphous carbon film is not irradiated with ultraviolet rays. A series of evaluation tests were performed in the same manner as in Example 1. The results are shown in FIGS. 4 to 6 and 8 and Tables 1 and 2.

(Comparative Example 2)
A disk test piece was produced in the same manner as in Example 1. The difference from Example 1 is that the amorphous carbon film is irradiated with ultraviolet light having a wavelength of 365 nm using a discharge tube (CST-8A) having a spectral peak at a wavelength of 365 nm. A series of evaluation tests were performed in the same manner as in Example 1. The results are shown in FIGS. 4 to 6 and 8 and Tables 1 and 2.

(Comparative Examples 3-6)
A disk test was manufactured in the same manner as in Example 1. The difference from Example 1 is that a disk test piece (hydrogen-free DLC: hydrogen content 1 atom% (manufactured by Japan IT) was formed by sputtering to form an amorphous carbon film having a layer thickness of about 0.5 μm. In Comparative Examples 3 to 5, the wavelengths of ultraviolet rays to be irradiated were irradiated in order of 254 nm, 312 nm, and 365 nm for 30 minutes, and Comparative Example 6 was not irradiated with ultraviolet rays. A friction test was performed in the same manner as in Example 1. The result is shown in FIG.

[Result 1: Result by Auger electron spectroscopy]
As shown in FIGS. 4 (a) and 4 (b), the graphite shoulder peak (specifically, a portion raised slightly at about 237 eV) around the kinetic energy 235 to 245 eV of the reference example is compared with each example. Then, the waveform shape similar to the reference example was especially obtained about the amorphous carbon film irradiated with the ultraviolet-ray of wavelength 312nm of Example 2. FIG. Also, the waveform shape similar to that of the reference example was obtained for 245 nm of Example 1 although not as much as Example 1. From this, it is considered that the surface layer of the amorphous carbon film of Examples 1 and 2 was graphitized by ultraviolet irradiation. On the contrary, the amorphous carbon films of Comparative Examples 1 and 2 that were not irradiated with ultraviolet rays had a gentle shape, which was different from the shape of the shoulder peak seen in the reference example. The inventors performed the same analysis by irradiating the amorphous carbon film not containing hydrogen with ultraviolet rays (for all the wavelengths shown above). As a result.

[Result 2: Result of hardness test]
As shown in Table 1, the surface hardness (13.0 GPa) of Example 1 and the surface hardness (12.2 GPa) of Example 2 are compared to the surface hardness of Comparative Example 1 (13.6 GPa). It was falling.

[Result 3: Measurement result of surface roughness]
As shown in Table 2, in Examples 1 and 2 and Comparative Examples 1 and 2, there was no significant difference in any of the centerline average roughness Ra and the maximum height roughness Ry. Thereby, it can be said that the surface roughness does not change even if the surface of the amorphous carbon film is irradiated with ultraviolet rays.

[Result 4: Measurement result of surface free energy]
As shown in FIGS. 5 and 6, the water contact angle of the amorphous carbon coating irradiated with the ultraviolet light of 254 nm of Example 1 and 312 nm of Example 2 is not irradiated with the ultraviolet light of Comparative Example 1. The contact angle was smaller than that, and the surface free energy increased accordingly.

[Result 5: Result 1 of friction test]
As shown in FIG. 8, the ones irradiated with ultraviolet rays having a wavelength of 254 nm of Example 1 and 312 nm of Example 2 have a friction coefficient μ of about 0.02 to 0.05 in 200 to 4500 cycles (number of times). Low friction was developed and the coefficient of friction was stable. Thereafter, the friction coefficient gradually increases from about 5000 sliding cycles (friction repetition number), and finally the friction coefficient is about 0.1 to 0.15, which is about the same as Comparative Example 1. became.

  On the other hand, the sample of Comparative Example 1 which was not irradiated with ultraviolet rays maintained a friction coefficient of about 0.1 to 0.2 from the initial stage of friction. In addition, the sample of Comparative Example 2 irradiated with ultraviolet light having a wavelength of 365 nm has an initial coefficient of friction of about 0.1, and then with repeated friction, the coefficient of friction becomes about 0.15, and finally the coefficient of friction is It was not less than 0.1, but was about 0.15.

  In addition, as shown in FIG. 9, the film of amorphous carbon film containing almost no hydrogen of Comparative Examples 3 to 6 can confirm the reduction of friction coefficient (lower friction) against ultraviolet irradiation. could not.

  Based on the results 3 and 5, a soft low shear layer was formed as the surface layer of the amorphous carbon coating of Examples 1 and 2, and from the result 1, this soft low shear layer was more than the comparative example 1. It is thought that it is a layer containing many graphite structures. This is presumably because the surface layer of the amorphous carbon coating was altered (graphitized) into a layer containing more graphite structure by the irradiation of ultraviolet rays.

Example 3
A disk test piece was produced in the same manner as in Example 1. The difference from Example 1 is that the irradiation time of ultraviolet rays (wavelength 254 nm) is set to 60 minutes. A friction test was performed in the same manner as in Example 1. The result is shown in FIG.

Example 4
A disk test piece was produced in the same manner as in Example 2. The difference from Example 1 is that the irradiation time of ultraviolet rays (wavelength 312 nm) is set to 60 minutes. A friction test was performed in the same manner as in Example 1. The result is shown in FIG.

(Comparative Example 7)
The same disk test piece as in Comparative Example 1 was produced. A friction test was performed in the same manner as in Example 1. The result is shown in FIG.

(Comparative Example 8)
A disc test piece was manufactured in the same manner as in Comparative Example 2. The difference from Example 1 is that the irradiation time of ultraviolet rays (wavelength 365 nm) is set to 60 minutes. A friction test was performed in the same manner as in Example 1. The result is shown in FIG.

[Result 6: Result 2 of friction test]
As shown in FIG. 10, ultraviolet rays having a wavelength of 254 nm of Example 3 and 312 nm of Example 4 were irradiated with 200 to 4500 cycles (number of times), and the friction coefficient μ was about 0.02 to 0.05. A low friction was developed, and the same tendency as that obtained by irradiating the ultraviolet rays of Examples 1 and 2 for 30 minutes was obtained. Thereafter, the friction coefficient gradually increased from about 4500 cycles of sliding cycles (the number of friction repetitions). Finally, the friction coefficient was about 0.1 to 0.15, which was about the same as Comparative Example 7. became. On the other hand, the friction coefficient of Comparative Example 7 that was not irradiated with ultraviolet light and Comparative Example 8 that was irradiated with ultraviolet light having a wavelength of 365 nm was substantially constant from the beginning, and was about 0.1 to 0.18.

  From the results of the friction tests (Results 5 and 6) in Examples 1 and 3 (irradiation with ultraviolet light with a wavelength of 254 nm) and Examples 2 and 4 (irradiation with ultraviolet light with a wavelength of 312 nm), the results were about 4500 cycles regardless of the irradiation time. The coefficient of friction was increasing. This is presumably because the surface layer modified to graphite was worn by the ultraviolet irradiation, and the unmodified amorphous carbon film containing hydrogen was exposed. Therefore, the following ultraviolet penetration depth measurement test was performed.

<Measurement of UV penetration depth>
A disk test piece was produced in the same manner as in Example 1 (wavelength 254 nm). Then, the friction test was performed in the same manner as in Example 1, and when the friction coefficient increased while monitoring the change in the friction coefficient, the friction test was stopped and an amorphous force microscope (AFM) was used. The cross-sectional area and the depth of the wear scar formed on the sliding surface of the carbonaceous film were determined, and the specific wear amount of this film was calculated.

[Result 7: Measurement result of UV penetration depth]
In about 4500 cycles during the friction test, the friction coefficient increased in the same manner as in Example 1. Therefore, the friction test was stopped, and the wear depth was about 10 nm from the AFM observation image of the wear trace at that time. there were. This revealed that the UV penetration depth was about 10 nm. Moreover, it became clear that the specific wear amount is about 2.7 × 10 ⁻⁷ mm ³ / Nm.

(Example 5)
A disk test piece was manufactured in the same manner as in Example 1. The difference from Example 1 is that three types of disc test pieces were manufactured with ultraviolet (wavelength 254 nm) irradiation times of 20, 40, and 60 minutes. Then, the G position (G band peak position) and _ID / _IG were measured for these disk test pieces by laser Raman spectroscopy described in detail below. The result is shown in FIG.

<Laser Raman spectroscopy>
The bonding state of the amorphous carbon film having an irregular amorphous structure was evaluated by laser Raman spectroscopy. Here, the principle of laser Raman spectroscopy will be briefly described. The atoms in the molecule have a certain structure, but do not stand still at that position, but move in the vicinity of the equilibrium structure. This minute movement is called Brownian movement. Its frequency is determined by the mass of the atom and the magnitude of the force acting between the atoms, so it has a specific value for the molecule. Therefore, by measuring the vibration of this molecule, the type and state of the molecule in the sample can be known.

  The principle of measurement is to irradiate molecules in a sample with visible light or infrared light, and to spectroscopically measure the scattered light. Most of the scattered light is Rayleigh scattering having the same wave number as the incident light, but a very small amount of the scattered light includes Raman scattering having a frequency different from that of the incident light. Raman spectroscopy utilizes the fact that the difference between the Raman scattering and the wave number of incident light (Raman shift) corresponds to the energy of molecular vibration and rotational motion.

Here, when the structural analysis of the amorphous carbon film is analyzed by a Raman spectroscopic spectrum, the amorphous carbon film does not have a fixed crystal structure, and the Raman shift is around 1350 cm ⁻¹ and 1550 cm ^−1. In general, a peak of a spectral spectrum appears. The “G band” is a peak around 1550 cm ^{−1 of} this Raman shift, and the “D band” is a peak around 1350 cm ⁻¹ . The I _D / _IG ratio between the D band area intensity and the G band area intensity indicates the ratio of the amorphous structure contained in the amorphous carbon coating.

This time, a laser Raman spectrophotometer NRS-1000 manufactured by JASCO Corporation was used. An Ar ion excitation laser wavelength of 532.0 nm, an output of 10 mW, 0.01 times with a dimmer, a measurement time of 60 seconds / cycle, and an analysis range of 800 to 2000 cm ⁻¹ was measured twice and integrated. . The double integration is for removing the effects of cosmic rays.

(Example 6)
A disk test piece was manufactured in the same manner as in Example 1. The difference from Example 1 is that the ultraviolet light wavelength was set to 312 nm, and three types of disk test pieces were manufactured with ultraviolet light irradiation times of 20, 40, and 60 minutes. In the same manner as in Example 5, the G position (G band peak position) and I _D / _IG were measured by laser Raman spectroscopy. The result is shown in FIG.

(Comparative Example 9)
A disk test piece was manufactured in the same manner as in Example 1. The difference from Example 2 is that ultraviolet rays are not irradiated. In the same manner as in Example 5, the G position (G band peak position) and I _D / _IG ratio were measured by laser Raman spectroscopy. The result is shown in FIG.

(Comparative Example 10)
A disk test piece was manufactured in the same manner as in Example 1. The difference from Example 2 is that the wavelength of the ultraviolet light was 365 nm, and three types of disc test pieces were produced with the ultraviolet irradiation time of 20, 40, and 60 minutes. In the same manner as in Example 5, the G position (G band peak position) and I _D / _IG ratio were measured by laser Raman spectroscopy. The result is shown in FIG.

[Result 8: Result of laser Raman spectroscopy]
As shown in FIG. 11, from Examples 5 and 6 and Comparative Examples 9 and 10, no change in G position was observed depending on the wavelength and irradiation time. In addition, although the I _D / _IG ratio slightly changed, no tendency due to wavelength or irradiation time was observed.

  By the way, from the results of Examples 1 to 3 and Comparative Examples 3 to 6 (Results 5 and 6), it is considered that there is a correlation between the hydrogen content and graphitization of the amorphous carbon material by irradiation with ultraviolet rays. In order to clarify the relationship between the hydrogen content and graphitization, atomic composition analysis and hardness test by Auger electron spectroscopy were performed as shown below.

(Example 7)
A disk test piece was produced in the same manner as in Example 1. The difference from Example 1 is that the gas content of the plasma CVD method is changed to make the content of hydrogen contained in the amorphous carbon film 3, 16, 35 atomic%. Then, in the same manner as in Example 1, atomic composition analysis and hardness test by Auger electron spectroscopy were performed. The results of the hardness test are shown in Table 4 below.

(Comparative Example 11)
A disk test piece was produced in the same manner as in Example 1. The difference from Example 1 is that the gas content of the plasma CVD method is changed to make the content of hydrogen contained in the amorphous carbon film 37 atomic%. A hardness test was performed in the same manner as in Example 1. Table 4 shows the results of the hardness test.

[Result 9]
From the analysis result of Example 7, it is considered that the hydrogen content of the amorphous carbon coating was 3, 16, and 35 atomic%, and the waveform shape shown in the result 1 was obtained, and graphitization was performed. Conceivable. Moreover, from the result of the hardness test, as shown in Comparative Example 11, when the hydrogen content exceeded 35 atomic%, the hardness of the amorphous carbon coating decreased.

  From this result, it is considered that when the hydrogen content exceeds 35%, the wear resistance of the amorphous carbon coating is lowered. Further, from the results 1 and 9, it is considered that when the hydrogen content of the amorphous carbon film is 3 atomic% or less, graphitization is hardly exhibited even when irradiated with ultraviolet rays. From the above, it is considered that the hydrogen content contained in the amorphous carbon coating is preferably 3 to 35 atomic%.

  From the results 1 to 9, when the amorphous carbon film containing hydrogen is irradiated with ultraviolet rays of 254 nm and 312 nm, the C—C bond in the film is broken, and this is recombined with C═C. Thus, it is considered that the surface is graphitized to form a low shear layer, and the amorphous carbon coating has low friction in 200 to 4500 cycles.

(Example 8)
The same base material as Example 1 was prepared. Then, using the apparatus shown in FIG. 2, an amorphous carbon film (H−) containing hydrogen up to 16 atomic% and a layer thickness of 1.3 μm on the surface of the substrate by plasma CVD. DLC film) D was formed. Thereafter, an amorphous carbon film G irradiated with ultraviolet rays was formed to a thickness of 0.5 μm while being irradiated with ultraviolet rays (see FIG. 12B). The irradiation time was 100 minutes, the wavelength of ultraviolet rays was 312 nm, the irradiation energy was 100 joules, and the distance between the ultraviolet irradiation device and the substrate (test piece) was 150 mm. The thickness of the amorphous carbon coating G can be specified from a relationship between a friction coefficient and a film thickness by conducting a friction test in advance.

  The surface roughness, hardness, and friction test were performed on the sliding member thus manufactured in the same manner as in Example 1. In addition, the friction test measured the time which the value of the friction coefficient at the time of a friction test lasted at 0.05. The results are shown in Table 5.

Example 9
The same base material as in Example 8 was prepared. Then, using the apparatus shown in FIG. 2, an amorphous carbon film (H−) containing hydrogen up to 16 atomic% and a layer thickness of 1.3 μm on the surface of the substrate by plasma CVD. DLC film) D was formed. Next, after forming an amorphous carbon film (amorphous carbon layer) D1 to a thickness of 25 nm (film formation time 5 minutes), after film formation, ultraviolet irradiation is performed for 5 minutes under the same conditions as in Example 8. Then, a series of steps for forming a graphitized layer (layer irradiated with ultraviolet rays) G having a thickness of 5 nm was repeated 20 times to form a 0.5 μm film (see FIG. 12C). ).

  The surface roughness, hardness, and friction test were performed on the sliding member in the same manner as in Example 1. It was also confirmed that a similar layer was formed by forming an amorphous carbon film containing hydrogen on the surface of the base material while intermittently irradiating the base material with ultraviolet rays.

(Example 10)
An amorphous carbon film was formed in the same manner as in Example 8. The difference is that the distance between the ultraviolet irradiation device and the substrate (test piece) is 160 mm. Furthermore, the surface of the amorphous carbon coating is made amorphous by using a bilink (Cosmo Bio Inc., BLX-312) and a discharge tube (CST-8B) having a spectrum peak at an ultraviolet wavelength of 312 nm. The surface of the carbonaceous film was further irradiated with ultraviolet rays. The irradiation time was 30 minutes, the ultraviolet wavelength was 312 nm, the irradiation energy was 10 joules, and the distance between the ultraviolet irradiation device and the base material (test piece) was 150 mm (see FIG. 12D). The surface roughness, hardness, and friction test were performed on the sliding member in the same manner as in Example 1.

(Comparative Example 12)
An amorphous carbon film was formed in the same manner as in Example 8. After the amorphous carbon film D was formed without irradiating ultraviolet rays so that the hydrogen content was 16 atomic% and the layer thickness was 1.8 μm, a thickness of 10 nm was formed on the surface under the conditions of Example 8. The amorphous carbon film G irradiated with the ultraviolet rays was formed (see FIG. 12A). In addition, although the comparative example 12 is a comparative example of Examples 8-10, it is an example contained in Claim 1 of this invention corresponding to Example 4. FIG.

[Result 9]
As is clear from Table 5, Examples 8 to 10 maintain a lower coefficient of friction as compared with Comparative Example 12 due to the increased thickness of the amorphous carbon film irradiated with ultraviolet rays. It is thought that was made.

  As mentioned above, although it explained in full detail using embodiment of this invention, a concrete structure is not limited to this embodiment and an Example, There exists a design change in the range which does not deviate from the summary of this invention. They are also included in the present invention.

  DESCRIPTION OF SYMBOLS 31 ... Stage, 32 ... Parallel leaf | plate spring, 33 ... Strain gauge, 35 ... Ball holder, 41 ... Motor, 42 ... Pulley, 43 ... Belt, 44 ... Disc holder, B ... Ball test piece, P ... Disc test piece

Claims (11)

Forming a hydrogen-containing amorphous carbon film on the surface of the substrate;
And a step of irradiating the surface of the amorphous carbon film with ultraviolet rays.   A method for producing a sliding member, comprising forming an amorphous carbon film containing hydrogen on a surface of the base material while irradiating the base material with ultraviolet rays.   The method for manufacturing a sliding member according to claim 2, wherein the irradiation with ultraviolet rays is performed intermittently.   The method for manufacturing a sliding member according to claim 2, wherein the film formation is performed while increasing the irradiation energy of the ultraviolet rays.   The method of manufacturing a sliding member according to any one of claims 1 to 4, wherein a wavelength of the ultraviolet ray to be irradiated is a wavelength of 350 nm or less.   6. The amorphous carbon film is formed so that a hydrogen content contained in the amorphous carbon film is 3 to 35 atomic%. Manufacturing method of sliding member. A sliding member in which an amorphous carbon film containing hydrogen is formed on the surface of a substrate,
The sliding member, wherein the amorphous carbon film includes at least a layer irradiated with ultraviolet rays on a surface layer.   8. The sliding member according to claim 7, wherein the amorphous carbon film is formed by intermittently laminating layers irradiated with ultraviolet rays in a film thickness direction. 9.   9. The graphite contained in the amorphous carbon coating increases from the surface of the base material to the surface of the amorphous carbon coating in the amorphous carbon coating. The sliding member according to 1.   The sliding member according to any one of claims 7 to 9, wherein the irradiated ultraviolet light has a wavelength of 350 nm or less.   The sliding member according to any one of claims 7 to 10, wherein a hydrogen content contained in the amorphous carbon coating is 3 to 35 atomic%.

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