JP2001172766A - Coated sliding member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that the surface of a diamond film deposited by vapor phase synthesis is extremely rough and becomes increasingly hostile to mating materials as well as in friction coefficient, although diamond is minimal in friction coefficient if it is smooth, and to attain sliding characteristics of decreased friction coefficient and decreased attacks on mating materials when a diamond coated surface is rough. SOLUTION: The member is a sliding member coated with film, in which an upper-layer film composed of a carbon film, a metal film, or a compound film of 20 to 2,000 Knoop hardness is laminated on a lower-layer film which is composed of a diamond film or a film containing >=30 vol.% diamond microcrystals and has >8,000 Vickers hardness or Knoop hardness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding member such as a machine part having a surface coating.

[0002]

2. Description of the Related Art Various materials such as steel and ceramic materials are used for sliding members currently used in industrial products. In many of them, various attempts have been made to reduce seizure and frictional resistance. For example, use of a lubricant, optimization of the shape and roughness of a sliding surface, hardening treatment, Coating treatment and the like.

[0003] With regard to the coating of the sliding surface, chromium plating, phosphate coating, and the like have been applied for a long time, but recently, molybdenum disulfide treatment, chromium nitride treatment, titanium nitride treatment, and the like have attracted attention. Is taking a bath. Examples thereof include JP-A-7-118832, JP-A-61-87950, and JP-A-6-57407. Also, as described in JP-A-6-227882, an attempt has been made to apply a hard carbon film or the like to a sliding component.
Some products have already been put to practical use, such as a magnetic water storage medium such as a hot water faucet or a hard disk described in Japanese Patent Publication No. 2 (JP-A) No.

[0004]

In recent years, there has been a remarkable movement in reducing power consumption due to miniaturization and portability of electric products, and reduction of frictional resistance of a driving unit has become a major issue. In the field of transportation equipment such as automobiles, there is a strong demand for lower fuel consumption, and there is a strong demand for a reduction in the coefficient of friction in sliding parts such as engines. On the other hand, there is still a high interest in abrasion resistance, such as sliding at a high surface pressure and extending the life of a driving unit.

[0005] Under such circumstances, as disclosed in Japanese Patent Application Laid-Open No. 6-294307, attempts have been made to apply diamond to the sliding portion. However, diamond is expensive and the polishing cost is high. It has prevented its spread.

Generally, in frictional wear, the surface roughness greatly affects the wear resistance and the friction coefficient. Even a diamond having an extremely low friction coefficient if it is smooth, for example, has a problem in that the surface of a diamond film obtained by vapor phase synthesis is extremely rough, and the friction coefficient and the aggressiveness of the partner are increased. FIG. 1 is a schematic cross-sectional view of a conventional sliding member coated with a diamond coating before (a) and after (b) sliding. An object of the present invention is to realize a sliding characteristic with a small friction coefficient and low aggressiveness when a diamond-coated surface is rough.

[0007]

The present invention proposes the following to reduce the coefficient of friction of a member coated with a coating containing diamond or diamond microcrystals.

In the slide member coated with the coating, a diamond coating having a Vickers hardness of more than 8000 or an undercoat containing 30% by volume or more of diamond crystallites is formed, and a Knoop hardness of 20 is formed on the undercoat.
A coated sliding member characterized in that an upper layer film made of a carbon film, a metal film, or a compound film having a thickness of 2000 or more is laminated.

A diamond film or a film containing 30% by volume or more of diamond microcrystals generally has excellent wear resistance and low friction coefficient. Coatings containing less than 30% by volume of diamond microcrystals are 8000
Since the hardness tends to be lower than the above, the wear resistance is inferior because the hardness is low, and the coefficient of friction is also high. Meanwhile, diamond coating,
Alternatively, even if the coating contains diamond microcrystals in an amount of 30% by volume or more, when the substrate is rough or the coating itself is rough, the friction coefficient and the aggressiveness to the opponent increase. To prevent this, the upper layer has a Knoop hardness of 20 or more and 200 or more.
Zero or less carbon films, metal films, or compound films are stacked.

FIG. 2 is a schematic sectional view of a sliding member according to the present invention before (a) and after (b) sliding. The upper layer coating of the carbon film, the metal film or the compound film is worn from the convex portion at the beginning of sliding, and the convex portion becomes smooth in a short time.
As the protrusions are flattened, the lower layer film partially appears on the surface layer. The upper layer film is slightly concave than the lower layer film having a high hardness, and the portion of the lower layer film which remains slightly convex when it comes into solid contact with the counterpart material is mainly formed. As a whole, the surface becomes smooth, so that the opposing aggressiveness is small and the coefficient of friction is reduced due to the effect of diamond in solid contact.

If the Knoop hardness of the upper layer film of the carbon film, the metal film or the compound film is more than 2,000, it is too hard, and it takes a long time for smoothing by sliding. If the Knoop hardness is less than 20, it is too soft and easily removed.

The Knoop hardness and the Vickers hardness of the film are generally set in advance by using the hardness of the film obtained as a single layer. In order to measure the hardness of each film after lamination, the Knoop hardness of each layer can be measured by polishing the surface of the film obliquely or by using a ball thickness gauge. The ratio of the diamond microcrystals in the lower layer coating can be determined from an image obtained by a transmission electron microscope.

The material applied to the upper coating is carbon, aluminum, silicon, titanium, chromium, iron, nickel,
Sulfides such as zinc, molybdenum, silver, tungsten, gold and molybdenum disulfide, borides such as titanium boride, manganese phosphate phosphate, titanium carbide, titanium nitride, titanium carbonitride, titanium aluminum nitride, nitrided It is preferable to use one or more of carbides such as chromium, nitrides, and carbonitrides.

More preferably, the upper layer film is a hard carbon film having a Knoop hardness of 1000 or more and 2000 or less. This is because the hard carbon film itself has excellent slidability. Here, if the hardness of the hard carbon film is greater than 2000, the Knoop hardness is too hard as described above, and it takes time for smoothing by sliding, which is not preferable. Although the Knoop hardness is sufficiently effective even if it is smaller than 1000, a particularly preferable region in the wear resistance is the Knoop hardness of 1000 or more.

Regarding the film thickness, the carbon film, metal film or compound film of the upper layer film is generally from 0.1 μm to 2.0 μm.
The following is preferred. If the thickness is less than 0.1 μm, the function of smoothing the projections cannot be sufficiently performed because the thickness is too small. If the thickness is more than 2.0 μm, the cost of the coating process increases.

More preferably, the thickness of the carbon film, metal film or compound film of the upper layer coating is not less than the average surface roughness Ra of the upper layer coating and not more than the maximum surface roughness Rmax of the upper layer coating. Here, strictly speaking, the average surface roughness Ra and the maximum surface roughness Rmax may be defined by the surface roughness of the lower film before coating the upper film, but the upper film is formed of a carbon film, a metal film, or a compound. Even if it is defined by the roughness after coating the film, it does not change much. When the film thickness of the upper layer coating is smaller than the average surface roughness Ra of the upper layer coating, it is too thin to sufficiently perform the function of smoothing the convex portions, and the maximum surface roughness R of the upper layer coating is reduced.
If it is larger than max, the effect of the diamond of the lower layer coating having excellent sliding characteristics is hardly exhibited.

The thickness of the diamond film or the lower film containing 30% by volume or more of diamond microcrystals is as follows:
Although any thickness can be applied, it is preferable that the thickness be 0.5 μm or more and 3 μm or less. When the film thickness exceeds 3 μm, the surface roughness is increased, which is disadvantageous as a sliding member, and the manufacturing cost is increased. If the film thickness is smaller than 0.5 μm, the diamond crystals are likely to be separated from each other like islands, and it may be difficult to cover the entire base material as a film. However, even if the lower layer coating is thicker or thinner than this range, a sufficient effect is recognized.

The surface roughness of the upper film is determined by the average surface roughness Ra.
Is from 0.005 μm to 0.3 μm. The surface roughness may be the roughness at the stage of coating the lower layer coating, but does not change much even if it is defined by the roughness after coating the upper layer carbon film, metal film or compound film. The average surface roughness Ra of the upper layer coating is the lower limit of 0.005μ.
When it is smaller than m, the surface of the lower layer film has a sufficiently small roughness, so that it is not particularly necessary to cover the upper layer with a carbon film, a metal film or a compound film for the purpose of smoothing. Even if the average surface roughness Ra of the upper layer coating is larger than 0.3 μm, the effect of reducing the wear and the coefficient of friction is sufficient when the lower layer coating and the upper layer coating according to the present invention are coated. However, it is more effective to reduce the average surface roughness Ra to 0.3 μm or less as much as possible by previously reducing the roughness of the substrate sufficiently. After forming the lower layer coating,
Alternatively, a polishing step may be added after forming the upper layer coating to reduce the surface roughness. The average surface roughness Ra is more preferably 0.1 μm or less, and still more preferably Ra0.0
Preferably it is 5 μm or less.

As the base material of these coated sliding members, various steel materials, WC-based cemented carbides, or various ceramics, aluminum alloys, magnesium alloys based on silicon nitride, silicon carbide, aluminum oxide, zirconium oxide, etc. Etc. are optimal.

In the structure of the film, between the lower layer coating and the base material, for the purpose of improving the adhesion and the hardness of the base material,
Further, an intermediate layer can be provided. Examples of the intermediate layer include silicon, silicon carbide, titanium carbide, tungsten carbide and the like.

When it is difficult to synthesize diamond directly on a substrate such as various steel materials, aluminum alloys, magnesium alloys, etc., the diamond film is taken out after synthesizing a vapor phase synthetic diamond on another substrate in advance. It may be attached on the base material by a technique such as brazing.

The working environment is effective under both lubricated and non-lubricated environments. However, the effect is remarkable under liquid lubrication in which a difference in friction coefficient is unlikely to appear. Even under liquid lubrication, when used under oil lubrication such as automobile engine oil and machine oil, it is extremely effective in reducing friction loss.

It is suitable for high-speed sliding and high-surface-pressure sliding components. In the spinning and textile fields, it is suitable for high-speed sliding parts such as pots for household and industrial sewing machines, yarn paths, and various bearings. Examples of the OA device include a high-speed bearing of an OA device such as a laser printer. For home appliances, it is suitable for high surface pressure parts such as refrigerators and air conditioner compressor parts. In transportation equipment such as automobiles, there are engine parts, such as main motion systems such as pistons and crankshafts, cam and rocker arms, shim and lifters, valve train parts such as valves and valve seats, and fuel injection such as plungers. Pump peripheral parts and the like. Further, even when the coating of the present structure is applied to a field other than sliding parts, for example, a tool or a mold, the coating exhibits a sufficient effect in terms of wear resistance and the like.

The lower layer film of the diamond film is preferably obtained by a gas phase synthesis method such as a microwave plasma CVD method, an ECR plasma CVD method, a filament CVD method, and a combustion flame method. In addition, the underlayer coating containing 30% by volume or more of diamond microcrystals was also obtained by microwave plasma CVD.
Method, ECR plasma CVD method, filament CVD method,
Those obtained by a gas phase synthesis method such as a combustion flame method are preferable,
In this case, the portion other than the diamond is formed of a phase such as amorphous carbon or graphite.

Further, the latter film containing 30% by volume or more of diamond microcrystals may be a composite material containing 30% by volume or more of diamond fine particles by a high-pressure synthesis method or the like. And metals, ceramics and the like can be applied. When it is difficult to synthesize diamond directly on the base material, a separately synthesized diamond may be attached to the target base material by brazing or the like.

When the upper film is a metal film or a compound film, known methods such as sputtering, various plasma CVD, ion plating, cathode arc ion plating, vacuum deposition, laser ablation, ion beam sputtering, etc. The film can be formed by the method described above.

When the upper film is a carbon film, microwave plasma CVD, ECR plasma CVD, filament C
In addition to VD method, combustion flame method, etc., plasma CVD using various plasma sources such as high frequency, DC voltage, pulse DC voltage, arc using a hollow cathode and hot cathode
For example, an ion beam evaporation method using carbon or hydrocarbon ions, a method of vaporizing carbon by sputtering, arc discharge, or laser irradiation from a solid carbon source and forming a film on a substrate can be applied. From the viewpoint of adhesion, it is desirable to continuously treat the carbon film, the metal film, or the compound film of the lower film and the upper film.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described with reference to examples, but the present invention is not limited to these examples.

[0029]

EXAMPLES (Example 1) By a filament CVD method,
A 2 μm-thick vapor-phase synthetic diamond was deposited on a cemented carbide substrate. The Knoop hardness of this vapor phase synthetic diamond was greater than 8000. Various films were formed on the surface by various film forming methods shown in Table 1. For comparison, a single-layer diamond film without an upper layer film was also prepared.

The obtained laminated coating was subjected to a friction and wear test by a pin-on-disk method. The atmosphere was lubrication in light oil and by dropping of machine oil. The laminated film was a disk, the mating material was a SUJ2 pin with a tip curvature radius of R3 mm, a load of 10 N, a rotation speed of 500 rpm (sliding speed of 10 rpm).
0 mm / sec) and the number of rotations was 10,000 times. At the end of 10,000 sliding tests, the coefficient of friction was measured. After the sliding test, the diameter of the wear mark of the mating pin was measured. The results are summarized in Table 2.

A single-layer diamond having a rough surface has a low coefficient of friction and a very high aggressiveness to a partner. However, by applying various coatings to the upper layer, the friction coefficient is reduced, and the opponent aggression is reduced. However, those coated with titanium aluminum nitride having a hardness of 3200 exhibited a large coefficient of friction and aggressiveness to the partner.

[0032]

[Table 1]

[0033]

[Table 2]

Example 2 A 2 μm-thick diamond microcrystal-containing film was deposited on a silicon nitride substrate by microwave plasma CVD. The Knoop hardness of this diamond microcrystal-containing film was greater than 8000. As a result of measuring the ratio of diamond microcrystals in this film by a transmission electron microscope, 40% by volume was diamond microcrystals. Hard carbon films having various hardnesses shown in Table 3 were formed on the surface of the lower layer coating.

The obtained laminated coating was subjected to a friction and wear test by a pin-on-disk method. The sliding test was performed in the same manner as in Example 1 by lubricating the atmosphere in a dry atmosphere and by dripping engine oil 10W-40SH. For comparison, a test was also performed on an uncoated silicon nitride substrate and a test piece treated only with a diamond coating. Table 4 shows the results. It can be seen that the lamination of the hard carbon film on the upper coating reduces the coefficient of friction and the amount of wear on the other side. In particular, the Knoop hardness of the upper hard carbon film is 100
At 0 or more and 2000 or less, the tendency is remarkable.

[0036]

[Table 3]

[0037]

[Table 4]

Example 3 A 2 μm-thick vapor-phase synthetic diamond was deposited on a cemented carbide substrate by ECR plasma CVD. The Knoop hardness of this vapor phase synthetic diamond was greater than 8000. Hard carbon films of various thicknesses shown in Table 5 were formed on this surface.

The obtained multilayer coating was subjected to a friction and wear test by a pin-on-disk method. The sliding test was performed in the same manner as in Example 1 by lubricating the atmosphere in a dry atmosphere and by dripping engine oil 10W-40SH. Table 6 shows the results. It can be seen that when the thickness of the upper hard carbon film is 0.1 μm or more and 2 μm or less, the friction coefficient and the opponent aggressiveness are small. In particular, when the thickness of the hard carbon film is not less than the surface roughness Ra and not more than Rmax, the tendency becomes remarkable.

[0040]

[Table 5]

[0041]

[Table 6]

Example 4 A 1.5 μm-thick vapor-phase synthetic diamond was deposited on a silicon nitride substrate by microwave plasma CVD. The Knoop hardness of this vapor phase synthetic diamond was greater than 8000. Table 7 on this surface
The molybdenum disulfide coatings of various film thicknesses shown in FIG.

The obtained laminated coating was subjected to a friction and wear test by a pin-on-disk method. The atmosphere was lubricated in light oil and by dripping of engine oil 10W-40SH, and a sliding test was performed in the same manner as in Example 1. Table 8 shows the results. It can be seen that when the film thickness of the upper molybdenum disulfide film is 0.1 μm or more and 2 μm or less, the friction coefficient and the opponent aggressiveness are small. In particular, the tendency becomes remarkable when the film thickness of the molybdenum disulfide coating is from surface roughness Ra to Rmax.

[0044]

[Table 7]

[0045]

[Table 8]

(Example 5) Vapor-phase synthetic diamond having various film thicknesses shown in Table 9 was deposited on a silicon carbide substrate by a filament CVD method. The Knoop hardness of this vapor phase synthetic diamond was greater than 8000. On this surface, a hard carbon film having a Knoop hardness of 1500 was laminated with a thickness of 0.8 μm. In addition, one of the laminates of a 4 μm-thick diamond film as a lower layer and an upper hard carbon film was polished from the surface of the hard carbon film to reduce the surface roughness and subjected to a test.

The resulting laminated coating was subjected to a friction and wear test by the pin-on-disk method. The atmosphere was lubricated in dry atmosphere and by dripping of machine oil.
A sliding test was performed in the same manner as described above. Table 10 shows the results. The thickness of the lower diamond coating is 0.5μ or more and 3μ
It can be seen that the coefficient of friction and the opponent's aggressiveness are small at m or less.
In addition, even when the thickness of the lower diamond film was large, a reduction in the coefficient of friction and aggressiveness to the opponent were observed by polishing after laminating the hard carbon film. This polishing was easier than polishing the diamond coating itself.

[0048]

[Table 9]

[0049]

[Table 10]

Example 6 The outer periphery of a silicon nitride plunger was subjected to the treatment of Example 2-11. Example 2-11
The plunger subjected to the above treatment was operated stably for 80 times as long as the plunger without the coating treatment.

(Embodiment 7) On the outer periphery of a shaft made of silicon nitride,
The coating of Example 4-20 was applied. When this was used in combination with a bearing made of silicon nitride, the bearing slid on the shaft of Example 4-20 was one of the bearings slid on the uncoated shaft.
/ 20.

Example 8 A coating rail of Example 1-7 and Comparative Example 1-2 was applied to a cemented carbide transfer rail on which a stainless steel workpiece was transferred. When these were actually used, there was a problem in that uncoated rails slipped poorly and the product flow was interrupted. In the rail of Comparative Example 1-2, the product flow was smooth, but the defect rate due to scratches on the slip surface of the product exceeded 20%. On the other hand, in the rail of Example 1-7, the flow of the product was smooth, the generation of scratches was extremely small, and the defect rate due to the scratches was 1% or less.

(Embodiment 9) Next, the sliding surface of the valve operating system of the engine with the cam of the silicon nitride shim was used.
And Comparative Example 2-6. It was confirmed that the frictional resistance of the lifter of Example 2-12 was reduced by 50% with respect to the uncoated lifter and that of the lifter of Comparative Example 2-6 with 40%. Also, the abrasion of the cam was about half of that of the uncoated film, and was one fifth of that of Comparative Example 2-6.

[0054]

According to the present invention, 30% by volume of a diamond coating or diamond microcrystals is contained in a sliding member.
When the surface covered with the film containing the above is rough, it is useful because it can realize sliding characteristics with a small coefficient of friction and low aggressiveness to a partner.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a sliding member coated only with a diamond film before and after sliding.

FIG. 2 is a schematic sectional view of a sliding member according to the present invention before and after sliding.

[Explanation of symbols]

 Reference Signs List 1 base material 2 diamond coating 3 partner material 4 lower coating 5 upper coating

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F16C 33/24 F16C 33/24 Z (72) Inventor Hisanori Ohara 1-1-1 Kunyokita, Itami City, Hyogo No. Sumitomo Electric Industries, Ltd. Itami Works F term (reference) 3J011 DA02 QA04 SB02 SB04 SB05 SB12 SB13 SB15 SB20 SD01 SE02 SE10 4K029 AA02 AA04 BA01 BA03 BA04 BA05 BA07 BA09 BA11 BA12 BA17 BA18 BA34 BA35 BA41 BA51 BA53 BA54 BA55 BA58 BB00 BB07 BC02 BD04 CA03 CA05 EA01 4K030 BA01 BA02 BA06 BA07 BA12 BA14 BA18 BA20 BA21 BA28 BA29 BA35 BA36 BA38 BA41 BA49 BA50 BB13 CA02 CA03 CA05 FA01 FA02 FA10 LA23

Claims (12)

[Claims] 1. A sliding member coated with a coating, wherein Vickers hardness or Knoop hardness is greater than 8000.
An upper film made of a carbon film, a metal film or a compound film having a Knoop hardness of 20 or more and 2,000 or less is laminated on a lower film made of a diamond film or a film containing 30% by volume or more of diamond microcrystals. Coated sliding member. 2. The method according to claim 1, wherein the upper film is made of carbon, aluminum,
It consists of at least one of silicon, titanium, chromium, iron, nickel, zinc, molybdenum, silver, tungsten, gold, sulfide, boride, phosphate, carbide, nitride, and carbonitride. The coated sliding member according to claim 1. 3. The method according to claim 1, wherein the upper layer coating has a thickness of 1,000 to 2,000.
The coated sliding member according to claim 1, wherein the coated sliding member is a hard carbon film having the following Knoop hardness. 4. The coated sliding member according to claim 1, wherein the thickness of the upper layer coating is 0.1 μm or more and 2.0 μm or less. 5. The method according to claim 1, wherein a thickness of the upper layer coating is not less than an average surface roughness Ra of the upper layer coating, and a maximum surface roughness Rma of the upper layer coating.
The coated sliding member according to any one of claims 1 to 4, wherein x is equal to or less than x. 6. The method according to claim 1, wherein the thickness of the lower film is 0.5 μm or more.
The coated sliding member according to any one of claims 1 to 5, wherein the thickness is not more than μm. 7. An upper layer film having an average surface roughness Ra of 0.
The coated sliding member according to any one of claims 1 to 6, wherein the thickness is not less than 005 µm and not more than 0.3 µm. 8. The base material to be coated is any one of an iron-based alloy, a cemented carbide, a ceramic, an aluminum alloy, and a magnesium alloy.
A coated sliding member according to claim 7. 9. The coated sliding member according to claim 1, wherein the coated sliding member is used under lubrication. 10. The coated sliding member according to claim 1, wherein the coated sliding member is used under engine oil lubrication. 11. The method according to claim 1, wherein the undercoating film is a microwave plasma CVD method, an ECR plasma CVD method, or a filament CV.
2. The composition according to claim 1, wherein the compound is synthesized by a D method or a combustion flame method.
The coated sliding member according to claim 10. 12. The method according to claim 1, wherein the upper layer film is formed by microwave plasma CVD, ECR plasma CVD, filament CV.
D method, combustion flame method, sputtering method, plasma CVD
The coated sliding member according to any one of claims 1 to 11, wherein the coated sliding member is synthesized by any one of a method, an ion plating method, and a cathode arc ion plating method.