JP2002348668A - Amorphous hard carbon film and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve an initial conformability of an amorphous hard carbon film formed on the surface of a sliding member. SOLUTION: The amorphous hard carbon film includes silicon carbide and silicon oxide, and the silicon oxide content increases toward the film surface continuously or stepwise.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amorphous hard carbon film applied to sliding parts for the purpose of abrasion resistance and low friction and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, as a method for surface treatment of tools, dies, and the like, in addition to plating and nitriding,
Abrasion resistance and seizure resistance are improved by applying a coating such as a PVD method or a CVD method for forming a hard film of a metal carbide such as C or TiN or a metal nitride. A similar surface treatment is performed on the piston ring ("Tribologist", Vol. 44 / No. 3/1999, p. 160). However, the coating layer of these hard films is Hv2000-3.
000, but the coefficient of friction is 0.2-0.8
Due to the large degree, the sliding resistance increases due to friction with the mating material, and problems such as wear of the coating film and damage to the mating material occur.

An amorphous hard carbon film formed by a CVD method using a plasma or an ion beam has a HV of about 2,000.
Since it shows a high hardness of up to 6000, it is attracting attention as a hard coating material having good wear resistance. The amorphous hard carbon film is also called an amorphous carbon film, a diamond-like carbon film, an i-carbon film, a hydrogenated amorphous carbon film (aC: H), or the like. It is the main membrane. In the present invention, hard means that the hardness is higher than the counterpart material, especially Hv
It is a substance having a hardness of 1500 or more.

In Japanese Patent Application Laid-Open No. 3-240957, silicon is contained in an amorphous carbon thin film containing carbon and hydrogen as main components, so that it contains pseudo diamond and has a high hardness and a high hardness of 0.1 mm.
A hard amorphous carbon-hydrogen-silicon based thin film having a very low coefficient of friction of not more than 05 is disclosed. However,
Although hard silicon carbide is contained in the film, it has high hardness and excellent abrasion resistance, but has a problem of poor adaptability at the initial stage of sliding.

[0005] Japanese Patent Application Laid-Open No. 7-54150 discloses that an amorphous hard carbon film containing an appropriate amount of silicon and nitrogen has excellent adhesion to a substrate, excellent wear resistance and excellent sliding characteristics (friction coefficient). Is disclosed. The contents of silicon and nitrogen in the amorphous hard carbon film are determined from the viewpoint of obtaining good adhesion and wear resistance.

Japanese Patent Application Laid-Open No. Sho 62-157602 discloses an amorphous carbon film containing a metal element such as silicon. According to this publication, the internal stress can be reduced by adding an appropriate amount of a metal element such as silicon to provide a film having high adhesion and high hardness, but no mention is made of the coefficient of friction.

As described above, application of the amorphous hard carbon film to a sliding member has been studied, but no consideration has been given to the initial familiarity. That is, when the film thickness is large, many fine protrusions are generated on the surface after the formation of the amorphous hard carbon film. In particular, a large number of microprojections tend to be generated in an amorphous hard carbon film formed by a sputtering method or the like. The size of the projection may exceed 2 μm in height at the maximum.
When the amorphous hard carbon film having the surface with such minute projections is slid with respect to the mating material, the frictional force increases in the initial stage of sliding, and the mating material is attacked and worn, On the other hand, there is a problem that it is difficult to form a familiar surface.

[0008]

Generally, in a sliding part, abrasion resistance, seizure resistance and a coefficient of friction are important in a use environment. A sliding component coated with an amorphous hard carbon film has a small coefficient of friction and exhibits excellent properties such as abrasion resistance and seizure resistance. In the piston ring, the frictional force with the cylinder inner surface can be reduced by coating the outer peripheral sliding surface with an amorphous hard carbon film. On the other hand, in the piston ring, that is, in order to ensure airtightness between the inner surface of the cylinder and the piston ring, it is important that the piston ring and the cylinder wear each other at an initial stage of sliding and adapt to each other. However, when the minute projections as described above are present on the surface of the amorphous hard carbon film, there is a problem that the initial familiarity is significantly impaired. The present invention has been made in view of such a problem, and an object of the present invention is to provide an amorphous hard carbon film having excellent initial familiarity and a method for producing the same.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an amorphous hard carbon film containing carbon and hydrogen as main components. The maximum position of the silicon oxide content which contains silicon and changes from the inside of the film toward the film surface is located on the film surface, and the minimum position (including 0%) is located inside the film. An amorphous hard carbon film characterized in that the amount increases continuously or stepwise. The first method according to the present invention includes the steps of: generating plasma between a substrate and an electrode disposed in a chamber containing a hydrocarbon gas, an organosilicon compound gas, and oxygen; and containing silicon carbide and silicon oxide on the substrate. C to form an amorphous hard carbon film
In the VD method, an amorphous hard carbon film is manufactured by changing the ratio of the oxygen to the hydrocarbon gas and the organic silicon compound gas during the film formation. According to a second method of the present invention, a plasma is generated between a substrate and an electrode disposed in a chamber containing a hydrocarbon gas and an organic silicon oxygen compound gas, and a plasma containing silicon carbide and silicon oxide is formed on the substrate. In the plasma CVD method for forming the amorphous hard carbon film, the amorphous hard carbon film is manufactured by changing the ratio of the organic silicon oxygen compound gas to the hydrocarbon gas during the film formation.

[0010]

The present invention has been accomplished by focusing on the above-mentioned problems of the prior art as follows. That is, the hardness, wear resistance, and low friction coefficient properties of the carbon-based material film are as follows. Diamond has a low coefficient of friction, is high in hardness, and has excellent wear resistance, but is difficult to finish and has a high aggressiveness of a mating material. On the other hand, graphite has lubricity, but has a problem in abrasion resistance. It is known that the recently developed amorphous carbon film has relatively high hardness and low friction coefficient. It is not sufficient, and it is difficult to increase the film thickness because the internal stress is large. In automotive sliding parts used under severe conditions such as piston rings, a film thickness of at least several microns is required to ensure sufficient durability, so carbon and hydrogen are the main components. An amorphous carbon film, which is difficult to make thick, cannot be put to practical use. Under such a background, attention has been paid to the fact that by adding silicon during the formation of the amorphous hard carbon film, the film stress is relieved and the film can be made thicker.

Further, by adding oxygen during the formation of the amorphous hard carbon film containing a trace amount of silicon, SiO 2
It was noted that No. ₂ was formed, and the friction coefficient and hardness could be changed. That is, since the friction coefficient is large amount of SiO ₂ in the film decreases, when most of the SiO ₂ content of the membrane surface, hardness is decreased, fine irregularities are formed on the film surface for a soft film Even so, the minute irregularities are quickly worn away, so that they easily become compatible with the mating material. On the other hand, after the familiar surface is formed, abrasion resistance and seizure resistance are important. Therefore, inside the film, the amount of SiO ₂ is reduced so that these properties become good and high hardness is obtained. Or not containing SiO ₂ .

As a first method of forming such an amorphous hard carbon film containing silicon oxide, there is a method using a hydrocarbon, an organic silicon compound and oxygen, and methane, acetylene, benzene is used as a hydrocarbon material. And at least one selected from the group consisting of toluene. In addition, one or more compounds selected from the group consisting of tetramethylsilane and tetraethylsilane are used as the organic silicon compound. As a second method for forming an amorphous hard carbon film containing silicon oxide, there is a method using a hydrocarbon and an organic silicon oxygen compound. In this case, at least one selected from the group consisting of methane, acetylene, benzene, and toluene is used as the hydrocarbon material, and pentaphenyl-trimethyl-siloxane, tetraphenyl-tetramethyl-trisiloxane is used as the organic silicon oxygen compound. 1 selected from the group consisting of
Use more than species.

The amorphous hard carbon film of the present invention has excellent initial conformability in addition to excellent adhesion and abrasion resistance. When the amount of added oxygen is changed in the amorphous hard carbon film containing an appropriate amount of silicon, the film hardness and the coefficient of friction change as shown in the following table.

[0014]

[Table 1]

The amorphous hard carbon film shown in Table 1 has a hydrogen content of 30 to 50 at% and a carbon content of 90% in the remaining composition excluding hydrogen.
At% or more, less than 5 at% of silicon, and oxygen have the compositions shown in the table. This amorphous hard carbon film contains silicon carbide and silicon oxide. By setting the oxygen addition amount to 2 to 5 at%, the film hardness can be set at about Hv 1500 to 1000 and the coefficient of friction is small, so that excellent initial adaptability can be imparted.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments shown in the drawings will be described below in more detail.

Example 1 (addition of oxygen, step shape) FIG. 1 schematically shows the layer structure of an amorphous hard carbon film according to this example. In this layer structure, the substrate 1
Using SKH51 material, a chromium intermediate layer 2 is formed by RF magnetron sputtering, and then a high hardness, wear-resistant amorphous carbon film upper layer 3 is formed by plasma CVD,
By continuously adding oxygen gas, the amorphous carbon film upper layer 4 having low hardness and extremely low friction coefficient is formed.

FIG. 2 schematically shows an apparatus for producing an amorphous hard carbon film according to the present invention. A sample 13 (SKH51 base material) is placed on a substrate holder 12 having a rotation mechanism (not shown) provided in the center of the vacuum chamber 11, and a vacuum pump (not shown) connected to the exhaust port 14 in the vacuum chamber 11. ), The ultimate vacuum degree is 9.3E-5Pa (7.
Exhaust to 0E-7 torr).

Next, a predetermined flow rate of argon gas is introduced through the gas inlet 15 to reduce the pressure in the vacuum chamber (11) to 0.1.
Adjust to 665Pa (5mtorr). And the substrate holder 12
A high frequency power (RF power) of 13.56 MHz is applied to the sample 13 from the bias power supply 19 connected to the sample to excite the plasma discharge. The sample 13 is cleaned by the ion bombardment of the argon ions excited in this manner.

Next, after increasing the flow rate of the argon gas to adjust the pressure in the vacuum chamber (11) to 1.33 Pa, RF power is applied to the chromium target 17 from the target bias power supply 16 with the shutter 18 closed. Presputtering is performed for a predetermined time, and then the shutter 18 is opened to form a chromium intermediate layer 2 having a thickness of about 1 μm on the surface of the sample 13. After the formation of the chromium intermediate layer 2, the shutter 18 is closed again to stop the argon gas.

Next, acetylene (C ₂ H ₂ ) gas and tetramethylsilane (TMS) gas are introduced into the vacuum chamber 11 at predetermined flow rates, and the pressure is adjusted to 1.33 Pa (10 mtorr). In this state, RF power is applied from the bias power supply 19 to the sample 13 via the substrate holder 12 to generate plasma, and the generated ions form an amorphous carbon film.
At this time, by adjusting the flow rate ratio of acetylene and tetramethylsilane so that the Si / (Si + C) ratio is 5 or less, the amorphous carbon film having a high hardness and excellent wear resistance and a thickness of 8 μm is formed. The upper layer 3 can be formed. If the Si / (Si + C) ratio is set to 4, the hardness of the film can be set to about Hv 2500, and the piston ring surface treatment is excellent in wear resistance to cast iron materials such as FC250. Hardness can be used.

Next, a state where RF power is continuously applied to the sample 13 from the bias power source 19, that is, the vacuum chamber 1
In a state where plasma is continuously formed in the amorphous carbon film 1, a small amount of oxygen gas is added in addition to acetylene and tetramethylsilane to form an amorphous carbon film surface layer 4 having a property different from that of the amorphous carbon film upper layer 3 by 2 μm. Form. At this time, the Si / (Si + C) ratio = 5 by the flow ratio of acetylene and tetramethylsilane.
By setting the oxygen addition amount to 2 to 5%, the hardness Hv
The amorphous carbon film surface layer 4 having a coefficient of friction of about 0.05 at 1000 to 1500 can be formed. The silicon oxide content in the amorphous hard carbon film formed by such a procedure changed stepwise as shown in FIG. In addition,
Micro-projections of about 1 μm were formed on the film surface.

Example 2 (addition of oxygen, gradient) In Example 1, the upper layer 3 was formed without adding oxygen, and then the oxygen-added surface layer 4 was formed. As shown in FIG. 4, the silicon oxide content in the film may be inclined by increasing the film thickness. In addition, micro projections of about 1 μm were generated on the film surface.

Example 3 (using a silicon-oxygen-containing compound) When a silicon-oxygen-containing compound is used, an amorphous hard carbon film is deposited on a substrate by an ion beam assisted deposition method. After cleaning with argon ions and forming an intermediate layer by chromium sputtering in the same manner as in Example 1, the hydrocarbon and silicon-oxygen-containing compound vapor is irradiated with argon ions by ion beam deposition to obtain silicon carbide and silicon oxide. To form an amorphous hard carbon film. At this time, the oxygen content can be changed by changing the flow rate of the hydrocarbon gas. As the silicon-oxygen-containing compound, pentaphenyl-trimethyl-siloxane (Si ₃ O ₂ C ₃₃ H ₃₂ ) _n and tetraphenyl-tetramethyl-trisiloxane (trade name: Dow Corning) used as silicon oil for diffusion pumps 704) can be used. In addition, 1
μm microprojections were generated.

Comparative Example 1 (Without Silicon Oxide) FIG. 5 shows a film structure of a comparative example manufactured to confirm the effect of the present invention. Chromium intermediate layer 2 formed on substrate 1 by sputtering in the same manner as in Example 1.
Is formed, and an amorphous hard carbon film upper layer 3 is formed thereon. In addition, micro projections of 1 μm were generated on the film surface.

FIG. 6 shows Embodiments 1 and 2 according to the present invention.
9 shows the results of a pin-on-disk scuff test of Comparative Example 11 and Comparative Example 11. The test condition was a peripheral speed of 8m /
Load from 1 to 30MPa in sec. 30 sec in 2MPa step
c and gradually increased. The oil used was motor oil P # 20 heated to 80 ° C.

[0027]

As is apparent from FIG. 6, in the comparative example having no upper layer, the peak of the coefficient of friction in the initial stage of sliding is large,
Although the initial familiarity is poor, in Examples 1 and 2 according to the present invention, the peak of the friction coefficient at the initial stage of the sliding is small, and it can be seen that the initial familiarity is improved. That is, by setting the silicon content in the upper layer to less than 5% and the oxygen addition amount to 2 to 5%, an amorphous hard carbon film having excellent initial compatibility can be obtained. Since such a film can be easily formed into a composite by changing the film hardness in the same process, it has excellent adhesiveness, and does not require a separate surface treatment, and is suitable as a surface treatment for sliding parts such as a piston ring. is there.

[Brief description of the drawings]

FIG. 1 is a view showing a film structure of an amorphous hard carbon film according to an embodiment of the present invention.

FIG. 2 is a view showing an apparatus for forming an amorphous hard carbon film of the present invention.

FIG. 3 is a diagram showing a silicon oxide content in an amorphous hard carbon film according to the present invention.

FIG. 4 is a diagram showing a silicon oxide content in an amorphous hard carbon film according to the present invention.

FIG. 5 is a view showing a film structure of an amorphous hard carbon film according to a conventional example.

FIG. 6 is a graph showing changes in friction coefficients of Examples 1, 2 and Comparative Example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Base material 2 ... Middle layer 3 ... Upper layer 4 ... Surface layer

Claims (4)

[Claims] 1. An amorphous hard carbon film containing carbon and hydrogen as main components, wherein the film contains silicon carbide and silicon oxide, and the silicon oxide content changes from the inside of the film toward the film surface. The maximum silicon oxide content position is on the film surface,
An amorphous hard carbon film having a minimum silicon oxide content (including 0%) inside the film. 2. The amorphous hard carbon film according to claim 1, wherein the change in the silicon oxide content is a continuous or stepwise increase. 3. A plasma is generated between an electrode and a substrate disposed in a chamber containing a hydrocarbon gas, an organic silicon compound gas and oxygen, and an amorphous hard material containing silicon carbide and silicon oxide is formed on the substrate. Plasma CV forming carbon film
The method for producing an amorphous hard carbon film according to claim 1 or 2, wherein in the method D, the ratio of the oxygen to the hydrocarbon gas and the organic silicon compound gas is changed during film formation. 4. An amorphous hard carbon film containing silicon carbide and silicon oxide on a substrate by generating plasma between an electrode and a substrate disposed in a chamber containing a hydrocarbon gas and an organic silicon oxygen compound. 2. The method according to claim 1, wherein the ratio of the organic silicic acid compound to the hydrocarbon gas is changed during the film formation in the plasma CVD method for forming the gas.
Or a method for producing an amorphous hard carbon film according to 2.