JPH08158051A - Rigid carbon film - Google Patents

Abstract

PURPOSE: To obtain a rigid carbon film excellent in hardness, wear resistance, easy in grinding and low in coefficient of friction by consisting it of diamond and amorphous carbon and specifying the peak intensity of Raman spectroscopic spectrum and the crystal size. CONSTITUTION: In the rigid carbon film consisting at least of diamond and amorphous carbon, the intensity ratio H1 /H2 of the peak intensity H1 present in 1160±40cm<-1> by Raman spectroscopic analysis to the highest peak intensity H2 present in 1350±40cm<-1> is controlled to 0.02-1, preferably 0.15-0.5. Further, average crystal diameter is controlled to <=3μm, preferably <=2μm. The surface roughness of the film is preferably <=2μm in Rmax and, as a result, the grinding time is decreased. The rigid carbon film is formed, for example, by electronic cyclotron resonance plasma CVD method and, at this time, the above properties are attained by adequately controlling the temp., pressure, reaction gas concn., etc., of the base material at the time of film forming.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hard carbon film containing diamond.
The present invention relates to a hard carbon film which is coated on the surface of a wear resistant member, a sliding member, etc. and has excellent slidability and wear resistance.

[0002]

2. Description of the Related Art In recent years, diamond has been applied to various fields because it has excellent properties such as high hardness, high thermal conductivity and chemical resistance. Since diamond is a very expensive natural product, it has come to be synthesized by the high temperature and high pressure method for industrial use, but on the other hand, it is considered to be applied to a wide range of applications such as cutting tools and wear resistant members. However, chemical vapor deposition (CVD) has been studied as a method for easily and efficiently synthesizing diamond.

In this chemical vapor phase synthesis method, generally, a mixed gas of a carbon-containing gas of hydrocarbon and hydrogen is introduced into a reaction tank to generate plasma by high frequency, microwave, etc., or heat is generated. It is a method of producing diamond on a desired substrate surface by heating with a filament.

The diamond film thus obtained has hitherto been one of the problems in how to produce high-purity diamond so that amorphous carbon, graphite and the like are not contained as impurities in the film. Has been found.

[0005]

The high-purity diamond film has high crystallinity and has excellent characteristics similar to those of a diamond single crystal. However, structurally, the diamond crystal grains forming the film are large, and the crystal has a rough surface having an uneven shape in which the automorphic plane is exposed. Therefore, for example, when such a high-purity diamond film is used by coating it on the surface of a predetermined substrate for the purpose of improving slidability, the material to be slid is scraped off, or uneven surface is formed. There was a problem that the stress was concentrated due to the impact and the film was damaged.

For this reason, conventionally, a method has been adopted in which a diamond film is thickly coated and then the film is polished to smooth the surface. However, such diamond polishing is extremely difficult, and it has been difficult to manufacture a member having a large surface area and having no surface defects. Further, although the above-mentioned polishing process can be applied to the one having a flat coated surface, there is a problem that the polishing process is difficult when the coated surface is a spherical surface or the like and the polishing process is difficult with a complicated surface shape. As it is difficult to polish,
Labor and cost in the polishing process were problems.

A method of increasing amorphous carbon and graphite components in order to obtain a smooth surface has been considered, but this method causes a problem that the hardness of the film is lowered and the wear resistance is lowered. was there.

According to the present invention, while maintaining excellent hardness and wear resistance, it is easy to carry out polishing, and a low friction coefficient can be realized when the surface of the sliding member is coated with a carbon film. An object of the present invention is to provide a hard carbon film that can be used.

[0009]

Means for Solving the Problems The inventors of the present invention have made extensive studies on the above problems, and as a result, the hard carbon film is composed of at least diamond, amorphous diamond and amorphous carbon, and its Raman spectroscopy In the spectral analysis, the peak intensity present at 1160 ± 40 cm ⁻¹ and 135
The ratio of the peak intensity at 0 ± 40 cm ⁻¹ to the highest intensity, and the grain size of the crystals that make up the film have a great influence on the sliding characteristics of the film, and these are within a specific range. The inventors have found that the sliding characteristics and the wear resistance characteristics can be improved and the surface roughness can be reduced when controlled, and have reached the present invention.

That is, the hard carbon film of the present invention is composed of at least diamond and amorphous carbon, and the peak intensity existing at 1160 ± 40 cm ⁻¹ in Raman spectroscopic analysis exists at H ₁ , 1350 ± 40 cm ⁻¹ . when the high peak intensity of the most intense of the peaks was with H ₂ to a strength ratio of 0.02 to 1 represented by H ₁ / H _2, at an average grain diameter of 3μm or less . The surface roughness is preferably 2 μm or less.

The present invention will be described in detail below. Diamond films, graphite, amorphous carbon and the like have been known as films made of carbon so far, but a substance composed of these carbons can be detected by Raman spectroscopic analysis. Diamond crystals are usually 133
It has a sharp peak near 3 ± 10 cm ⁻¹ , while amorphous carbon shows a broad peak at 1500 ± 100 cm ⁻¹ . In addition, for graphite, a peak is observed near 1580 ± 10 cm ⁻¹ .

The hard carbon film of the present invention has a different wave number from the above-mentioned structures of diamond crystals, amorphous carbon and graphite in Raman spectroscopic analysis.
It is characterized by having a peak at 160 ± 40 cm ⁻¹ . It is said that the peak at 1160 ± 40 cm ⁻¹ is not due to the above-mentioned diamond crystals, amorphous carbon, and graphite, but is due to amorphous diamond. The amorphous diamond is a diamond composed of diamond fine particles of 100 liters or less, and has a peak of 1160 ± 40 cm ^{−1 due to} the size effect.

According to the present invention, among the carbon films containing amorphous diamond, the peak intensity existing at 1160 ± 40 cm ⁻¹ is H ₁ at 1350 ± 40 cm ⁻¹ in terms of sliding characteristics and polishing efficiency. When the intensity of the highest intensity peak among the existing peaks is H ₂ , H ₁ / H ₂
It is important that the composition is such that the intensity ratio represented by is 0.02 to 1. This peak intensity ratio H ₁ / H
₂ means that as the value increases, the crystallinity decreases and the content of diamond crystals in the film decreases.
On the contrary, it means that the crystallinity is improved and the content of phases other than diamond is decreased as the peak intensity ratio becomes smaller. However, according to the present invention, the peak intensity ratio is more than 0.02. When it is small, the crystallinity is improved, the diamond crystal grains grow large, and the surface of the film is roughened, so that the sliding property of the film is significantly deteriorated. In addition, it is necessary to spend a long time in the polishing process for smoothing the roughness of the surface of the film. On the other hand, when the peak intensity ratio H ₁ / H ₂ is greater than 1, the amount of amorphous diamond produced increases, the crystallinity deteriorates, the hardness decreases, and the abrasion resistance during sliding deteriorates. The peak intensity ratio H ₁ / H ₂ is 0.15 to
It is preferably 0.5.

Further, in the present invention, from the viewpoint of sliding characteristics, it is desirable that the diameter of crystal grains forming the film is small, and specifically, it is important that the diameter is 3 μm or less. Especially 2μ
It is preferably m or less. By reducing the crystal grain size, the surface of the carbon film itself can be smoothed, and thus the sliding characteristics can be improved. In particular, the surface roughness of the carbon film depends on the surface roughness of the substrate to be coated, but Rmax is preferably 2 μm or less. By setting the surface roughness to 2 μm or less, the polishing time can be reduced. Based on this, it is desirable that the surface roughness of the substrate is 2 μm or less in Rmax.

When the base material coated with the hard carbon film of the present invention is subjected to X-ray diffraction measurement, a cubic diamond peak and a base material peak appear, and no other peaks are observed. Is.

Next, the method for obtaining the hard carbon film of the present invention will be described. As a carbon film generating means, plasma is generated by microwave or high frequency to form a carbon film on a predetermined substrate surface, that is, a so-called plasma CVD method. Alternatively, the hot filament CVD method is the mainstream. However, in the plasma CVD method, the area where the film can be formed is small because the plasma generation region is small, and the area where the film can be formed is generally 2
It is about 0 mm, its application as a sliding member is limited, and when the substrate has a fine structure or a curved structure because the pressure is too high or the plasma density is too low, it follows the structure. Uniform plasma cannot be obtained,
The membrane pressure distribution tends to be non-uniform. On the other hand, the hot filament CVD method has drawbacks that the filament is easily broken and that the filament needs to be installed according to the shape of the substrate in order to suppress variation in film thickness, and the apparatus lacks versatility. There is.

On the other hand, according to the so-called electron cyclotron resonance plasma CVD method in which a magnetic field is applied to the plasma generation region in the plasma CVD method, under a low pressure (1
Since a high-density plasma can be obtained at (torr or less), plasma can be uniformly generated in a wide area, and a film can be uniformly formed in an area about 10 times larger than that of a normal plasma CVD method. It can be performed. Therefore,
It is particularly effective when forming a film on a sliding member or the like.

Therefore, the electron cyclotron resonance plasma CVD method (ECR plasma CVD method) will be described here as an example. In this method, a reaction gas is introduced into a reaction furnace in which a predetermined substrate is installed and at the same time 2.4
A microwave of 5 GHz is introduced. At the same time, a magnetic field having a level of 875 Gauss or more is applied to this region. This causes the electrons to have a cyclotron frequency f = eB /
2πm (m: electron mass, e: electron charge, B:
Based on the magnetic flux density, it causes cyclotron motion. When this frequency agrees with the microwave frequency (2.45 GHz), it resonates, and the electrons remarkably absorb the microwave energy and are accelerated, causing collisions with neutral molecules and ionization to generate high-density plasma. Like At this time, the substrate temperature is 150 to 1000 ° C., and the furnace pressure is 1 × 1.
It is set to 0 ^{-2 to 1} torr.

According to this method, the substrate temperature during film formation,
By changing the pressure in the furnace and the concentration of the reaction gas, the components of the film to be formed change. Specifically, as the furnace pressure increases, the plasma region decreases and the film growth rate decreases, but the crystallinity tends to improve. Further, when the reaction gas concentration is high, the size of the particles forming the film is small, and the crystallinity tends to be poor. A hard carbon film having the above-mentioned predetermined characteristics can be produced by appropriately controlling these conditions as shown in Examples described later.

[0020]

According to the present invention, the crystallinity of the carbon film is controlled by controlling the conditions for forming the carbon film, such as the pressure in the furnace and the reaction gas ratio, and it is possible to control the crystallinity of the carbon film at 1160
By generating amorphous diamond reflected in the peak of ± 40 cm ^-1 in the carbon film at a specific ratio, the mechanical properties of the film itself, particularly excellent hardness, are maintained and the growth of crystal grains is suppressed. In addition, the film can be made dense. This makes it possible to obtain a smooth surface while maintaining the excellent hardness of the carbon film. When such a hard carbon film is coated on the surface of a sliding member, etc., it has the same sliding characteristics as a diamond film with excellent crystallinity, and the surface can be polished in a short time. A member that is easy to obtain can be obtained.

[0021]

Example: Surface roughness of 40 mm in diameter was Rmax in the furnace.
Install a ceramic disk of 0.1 μm and ECR
By the plasma CVD method, a magnetic field with a maximum intensity of 2 KG was applied, and the substrate temperature, the reaction gas concentration, and the furnace pressure were set to the conditions shown in Table 1 under the conditions of the microwave output of 3.0 kW, and the carbon film had a thickness of about 5 μm. It was manufactured to have a film thickness of.
The reaction gas used was a mixture of methane gas, carbon dioxide gas and hydrogen at the ratio shown in Table 1.

[0022]

[Table 1]

The obtained carbon film was subjected to Raman spectroscopic analysis of the film surface, and the peak intensity existing at 1160 ± 40 cm ⁻¹ in Raman spectroscopic spectral analysis was found to be the peak intensity present at H ₁ , 1350 ± 40 cm ^−1. The intensity of the highest intensity peak was defined as H _2, and the intensity ratio represented by H ₁ / H ₂ was calculated. Specifically, in the curve obtained by Raman spectroscopy as shown in FIG.
Draw a diagonal line between the positions of 000 cm ^-1 and 1700 cm ^-1 ,
Using this as a baseline, curve fitting processing was performed using each peak as a Lorentzian curve, and the height of each peak was determined. In Table 1, sample No. 2
And the chart of Sample No. 8 are shown. In this case, an Ar laser (oscillation line 488.0 nm) was used as a laser as an oscillation source in Raman spectroscopic analysis.

The average crystal grain size of the crystal grains of the carbon film was determined by SEM analysis, and the surface roughness (Rmax) of the carbon film was measured by a stylus type surface roughness meter.

Further, in order to evaluate the polishing efficiency, a portion having a width of 5 mm from the outer peripheral surface of the disk coated with the carbon film was surface-polished by a buff using fine diamond powder, and Rmax = 0.1 μm or less. The time until polishing was measured.

In order to evaluate the slidability, the portion polished as described above was used, and the radius of curvature of the tip portion was R = 4.763 m.
Using a metal pin of m, a load of 4.9 N is applied, a sliding speed is set to 0.30 m / S, a sliding test is performed by a ball-on-disk method, and a friction coefficient is measured for 200 hours. The average value was calculated. During the sliding test, the pin was replaced every 3 hours.

For samples No. 5 and 12, 1 after sliding test
In 60 hours, the film of No. 6 was worn out 110 hours after the sliding test, and the ceramic as the base material partially appeared. Therefore, the table shows the friction coefficient until the films of Sample Nos. 5, 6, 12 were worn out.

As is clear from Table 1, in the case where the crystallinity of the carbon film is good and H ₁ / H ₂ is less than 0.02, or the average crystal grain size is 3 μm or more, surface polishing requires a long time, It turns out that it is not practical. Further, in the case of a carbon film having H ₁ / H _{2 of} more than 1, the polishing time was short, but the film itself was severely worn and could not be used. For these comparative examples, those coated with the hard carbon film of the present invention,
It can be seen that all of them have excellent low friction coefficient and wear resistance, and can be polished to a state of Rmax = 0.1 μm or less in a short time.

[0029]

As described in detail above, according to the present invention,
Since the smooth surface can be obtained after film formation while maintaining the excellent hardness of the hard carbon film, the polishing process is easy, such as the short polishing time to a predetermined surface roughness, and the carbon film is used as a sliding member. A low coefficient of friction can be realized when the surface or the like is covered. Therefore, it is very effective as a carbon film formed on the surface of various sliding members and the like.

[Brief description of drawings]

FIG. 1 is a Raman spectroscopic analysis chart of a hard carbon film (Sample No. 2 in Table 1) of the present invention.

FIG. 2 is a Raman spectroscopic analysis chart of a comparative example (Sample No. 8 in Table 1).

Claims (2)

[Claims] 1. Consisting of at least diamond and amorphous carbon, 1160 in Raman spectroscopic analysis.
The peak intensity existing at ± 40 cm ⁻¹ is H ₁ , 1350 ±
When the intensity of the highest intensity peak of the peak was with H ₂ present in 40 cm ^-1, the intensity ratio is 0.02 to 1 which is represented by H ₁ / H _2, the average grain size of 3μm or less Is a hard carbon film. 2. The hard carbon film according to claim 1, which has a surface roughness of 2 μm or less.