JPS6069197A - Precision friction parts - Google Patents

Abstract

PURPOSE:To provide precision friction parts having excellent lubricating property and wear resistance, prepd. by applying a mixture of a specified Si compd., a metal alcoholate compd. and a metal in fine powder, to the surface of presision friction parts covered with a porous film having superfine pores. CONSTITUTION:A mixture is prepd. by mixing (C) 10-100pts.wt. at least one metal in fine powder having an average particle diameter of less than 1mum selected from among Au, Ag, Cu, In, Pb and Sn and (D) 20-200pts.wt. at least one lubricating substance in fine powder having an average particle diameter of less than 1mum selected from among sulfide, Se compd. Te compd., nitride and graphite, into 100pts.wt. mixture of (A) Si compd. of the formula (where R<1> is H, epoxy, methacryloxy, vinyl, mercapto, Cl-contg. organic group or 1-4C alkyl; R<2> is 1-8C aralkyl; a is 0-30) with (B) metal alcoholate compd. in a blend ratio of 100: 2-80 by weight. A porous film 2 having superfine pores is formed on the surface of a part 1 and then the above mixture is applied for formation of a composite film 3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to lubrication and wear-resistant precision sliding parts, and in particular, after the surface of the sliding part is coated in advance with an ultrafine porous film, the surface is coated with a silicon compound, a metal alcoholide compound, By coating and hardening a mixture containing at least a soft, malleable metal fine powder and a specific lubricating fine powder,
Concerning precision sliding parts with lubricity and wear resistance.

The purpose of the present invention is to form a film with a high level of lubricity and wear resistance on the entire surface or frictional sliding part of precision sliding parts using a simple and uniform method, so that the parts can be driven completely without lubrication. Our goal is to provide precision equipment, especially watches.

Conventionally, lubricating oil has been used to provide lubricity and wear resistance to the frictional sliding parts of precision equipment parts to maintain machine precision and functionality over a long period of time. However, when lubricating oil is used, the precision and functionality of precision equipment may be affected over a long period of time, such as the oil spreading to areas other than the sliding parts, the lubricating ability decreasing at low temperatures, or the lubricating ability decreasing due to chemical changes over time. There are many disadvantages to maintaining this. Also, rationalization of precision equipment assembly work.

The development of oil-less lubrication processing technology is desired in various fields, including the elimination of intermittent lubrication work in the market.

From this point of view, various solid lubrication treatments have been studied.

For example, MO'8. , We, , Graphite, BN, Fluorinated Graphite, FTIFI! A method of forming a film on the surface of friction sliding parts using fine powder such as i with an organic or inorganic binder, or a method of forming a film of soft metal or its alloy by vapor deposition, sputtering, ion blasting, etc. A method of forming a film by eutectoiding fine powder during hard or soft plating is being considered.

Furthermore, in order to improve wear resistance, surface hardening treatments such as nitriding the surface and a negative method of forming a film with an ultra-hard compound were also considered.

However, when applying either method to precision sliding parts,
The film thickness cannot be controlled with the required dimensional accuracy, and severe friction conditions, such as low speed and high load conditions (
In the case of the front wheel train of an analog crystal wristwatch, the lateral pressure is 10 to 50.
kg/-1 peripheral speed is 0. Q5~0.5 ff1m
/(6)) has the problem that the life of the lubricating film is extremely short. The main reason for the short life is considered to be the abrasion of the lubricant as well as the flaking and wear phenomenon caused by insufficient adhesion to the material of the sliding part.

Furthermore, among conventional lubrication processing techniques, methods using vacuum equipment are disadvantageous in terms of cost, such as expensive equipment and batch processing, which makes mass production difficult.

Due to the above drawbacks, it has been difficult to apply conventional processing techniques to precision sliding parts and put them into practical use.

The present invention completely solves such conventional drawbacks, and after coating the surface of a sliding part with an ultra-fine porous film, the surface is coated with a silicon compound, a metal alcoholide compound, a soft, malleable metal fine powder, and a , sulfides, selenides,
By coating a mixture containing at least one lubricating fine powder selected from telluride, nitride, and graphite and heating it, a uniform composite film having high lubricity and wear resistance over a long period of time can be obtained. It was formed. This provides lubrication performance that could not be obtained with conventional lubrication treatments, making it possible to completely eliminate lubrication of frictional sliding parts.To further explain the present invention, this lubrication treatment has two layers It is composed of a film of As shown in FIG. 1, the first layer is a very fine porous film 2 formed on the surface of the sliding part 1. This first
The layer maintains sufficient adhesion between the soft, malleable fine metal powder 4 formed in the second layer and the composite film 3 in which the above-mentioned lubricating fine powder 5 is dispersed, and has the effect of improving wear resistance. have

The formation method, material, thickness, and pore size of the porous film depend on the material of the sliding part, the usage environment, the metal fine powder used, and the
You can choose from the size of the fine powder.

Formation methods include a method of making the component surface itself porous and a method of adhering and forming a porous film on the component surface.

Examples of the former include physical methods such as sandblasting, chemical etching, and anodic oxidation treatment of Mut, Ti, etc.

Examples of the latter include a method in which Mut, Ti, etc. are formed into a film on the surface of the part using a vacuum method, and then anodized, N1-oo, or
Electrolytic plating method such as N1-B.

There are electroless plating methods such as Ni-Oo and Ni-W.

In addition, the coating material needs to have high hardness from the viewpoint of wear resistance, and the Vickers hardness is preferably 200 or more.The above-mentioned anodic oxide coating, electrolytic or electroless plating coating are all effective porous coatings. The size of the pores is 0, considering the sizes of available metal fine powder and lubricating fine powder.
．． 01 to 100 μm is desirable.

The next second layer consists of a soft, malleable metal fine powder, a lubricating fine powder, and a support that holds the fine powder in a dispersed state. Both of the powders are substances that have a lubricating effect and reduce the coefficient of friction of the second layer, and must not cause an increase in the coefficient even after long-term wear. For this purpose, at least two kinds of lubricating fine powders of components (0) and (I) described below, which have different properties, are essential. That is, (O)mu * A g@ Ou , In , Pb
, 8n, and the other is at least one metal fine powder selected from CD) sulfides, tellurides, selenides, nitrides, and graphite with an average particle size of 1μ or less. It is a lubricating fine powder with a thickness of less than 1μ. 0 component has a CD in its ability to reduce the coefficient of friction of the second layer.
), but it has excellent adhesion to the support described below and exhibits extremely strong durability against impact force and abrasion force during abrasion. Even if component (0) is used alone as the second layer lubricant, it exhibits fairly good lubrication properties, but the friction coefficient is slightly higher than that when lubricating oil is used, which causes some problems with the output torque, which will be discussed later. I'm leaving it behind. In contrast to component (0), component (D) has a slightly inferior adhesion to the support, so it is weak against impact force and scratching force during abrasion.
It has the ability to sufficiently reduce the coefficient of friction of the second layer to the same level as the coefficient of friction when using lubricating oil. This (0)CD)
Good abrasion resistance was achieved by using the components together, compensating for the shortcomings of both, and taking advantage of their strengths.

The particle size of both of the above-mentioned fine powders is the film thickness Q of the composite film, 1 to 2μ.
For reasons of convenience, a smaller particle size is desirable, with the particle size being 1μ.
0.5 μm or less, more preferably 0.5 μm or less.

As mentioned above, the support is made of at least two compounds of components (A) and (B) described below, from the viewpoint of adhesion with component (0), adhesion with the ultrafine porous film, and abrasion resistance. is optimal and necessary.

(A), general formula (1) R1, -B 1-(on2)4
-a silicon compound represented by (R1 is an epoxy group,
Methacryloxy group, vinyl group, mercapto group, organic group containing chlorine, hydrogen or alkyl group having 1 to 4 carbon atoms R
2 represents an alkyl group having 1 to 8 carbon atoms, and α is 0 to 3. ) (B), a metal alcohola-F compound represented by the general formula (2) M(OR''), (R2 is as described above, M
represents an atom of group Ⅰ or V of the periodic table. ) Typical examples of component (A) are r-glycidoxypropyltrimethoxysilane, r-methacryloxypropyltrimethoxysilane, vinyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, and r-chloropropyltrimethoxysilane.

These include tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, and the like.

A typical example of component CB) is tetrabutoxytin.

Tetraoctyl lead, tetraoctoxy titanium.

These include tetrabutoxyhafnium, tetrabutoxyzirconium, pentaethoxyantimony, pentaethoxytantalum, pentaisoproboxiniope, and the like.

The above alkoxy compound forms a dense three-dimensional film through a thermal decomposition reaction or a combined reaction of a hydrolysis reaction and a thermal decomposition reaction, and at the same time, the hydroxyl groups present on the surface of the ultrafine porous film and the fine metal powder are formed. , chemically combines with adsorbed water,
Provides strong adhesion. By appropriately selecting the type, combination, concentration, and heating conditions of the alkoxy compounds, films with different degrees of hardness and flexibility can be obtained.

To prepare a treatment solution for a composite film, 2 to 80 parts by weight of component CB) is added to 100 parts by weight of component (A).

If it is less than 2 parts by weight, the density, hardness, and abrasion resistance of the composite film will be poor, and if it is more than 80 parts by weight, cracks will easily occur in the composite film. It is then diluted with various solvents for ease of use. Solvents include alcohols such as methanol, ethanol, isopropyl alcohol, acetone, ketone a such as methyl ethyl ketone, esters such as vinegar m methyl ester A/, acetic acid ethyl ester, benzene, toluene,
Aromatics such as xylene, methylene chloride, 1,1.1-trichloroethane 51s1*2) Lichloro, 1.2.2
-) Halogenated hydrocarbons such as refluoroethane, which are used alone or in combination, and the total concentration of (A) CB) components varies depending on the thickness of the composite film and the type of solvent. is about o, 1-10%. Then (
○) Add 10 to 100 parts by weight of component (A) e (B) to a total of 100 parts by weight, and then add component CD) to (A).
) * (B) 20 to 20 parts by weight per 100 parts by weight of the total component
Add 0 parts by weight and disperse thoroughly. If the component (0) is less than 2 parts by weight of 10, the lubricating performance and durability will be insufficient;
If the amount is 0 parts by weight or more, lubricity and durability equivalent to or higher than those obtained when 10 to 100 parts by weight are added cannot be obtained. Also, component (D) is 20
If it is less than 2 parts by weight, the coefficient of friction of the second layer will not be sufficiently reduced, and the
If the amount is more than 0.00 parts by weight, the coefficient will be further reduced, but the adhesion between the second layer and the first layer will be reduced, and long-term wear characteristics will not be sufficiently ensured.

The above-mentioned treatment liquid is coated on a part having an ultrafine porous film (film thickness 0.1 to 4 μm) using a known method such as a dipping method, a pyrosol CVD method, or a spinner method.
By baking at ℃ for 5 to 120 minutes, the coefficient of dynamic friction μ=mouth, 05 to G, ! lO.

A composite film with a pencil hardness of 4H to 9H and a film thickness of 0 and 1 to 2μ is formed with good adhesion, and a sufficient practical lubrication life is ensured.

Note that a small amount of acids such as acetic acid, formic acid, phosphoric acid, hydrochloric acid, and sulfuric acid may be added to the treatment liquid for the purpose of promoting the film-forming reaction.

Examples will be described below, but the present invention is not limited by the examples, and parts and % represent parts by weight and i% by weight.

Example 1 Carbon steel (carbon =
1%) rotor pinion is heat treated to Vickers hardness of 700, and electroless nickel plating is applied to prevent corrosion.
．． A layer with a thickness of 5 μm was formed on the surface. Further, Ni-00 alloy plating was performed using the following composition and electrolytic conditions.

(Bath composition) Nickel sulfate 180 fit Cobalt sulfate 40 f/1 Cobalt chloride 15 f/4 Antimony chloride 25 f/Boric acid 10 f/l (Electrolytic conditions) Bath temperature 50°C Current density 2 μ/1 hour 15- Plating thickness is , 2μ, and when its surface was observed with an electron microscope, it was confirmed that it was an extremely fine porous surface. Next, it was immersed in a treatment solution (A) having the following composition for 2 minutes at room temperature,
Thereafter, it was fired at 60°C for 10 minutes and at 200°C for 60 minutes.

(Processing Ronin) Tetramethoxysilane...2v Tetrabutoxytitanium...0.51A2 fine powder (average particle size 0.07μ)...0.21M08. Fine powder (average particle size 0.03μrn) -2t Daiflon s3
(Daikin Industries product) ...The composite film thickness of the rotor pinion treated with 100°C was about 0.3μ. Also, in order to observe the adhesion of the film, the rotor pinion was heated to 200°C. After heating, it was rapidly cooled in cold water at a temperature of 1° C., and when its appearance was observed, it was confirmed that no cracks had occurred at all and that it had strong adhesion. Furthermore, in order to confirm the lubrication life of the film, the rotor pinion was installed in a wristwatch, and a wheel train durability test for the equivalent of 10 years was conducted at an acceleration rate of 32 times that of normal operation. Several times during the durability process, the applied voltage 1.
The drive torque of the second wheel (hereinafter abbreviated as output torque) at 58V is measured. The measured value is expressed as the durability period on the horizontal axis,
Plot on a graph with output torque on the vertical axis and connect with a straight line. The results are shown by the polygonal line A in FIG. In FIG. 2, the polygonal line B shows the results of a wristwatch that incorporated a rotor pinion that was treated with the treatment solution (A) directly on the electroless N1 plating for corrosion prevention of Example 1 of the present invention, in addition to A. Line C shows the results of a wristwatch equipped with a rotor pinion coated with electroless N1 plating for corrosion prevention as in Example 1, and with lubricating oil (5YNT-A-LUBE (manufactured by Mavis, Switzerland)) applied to the upper and lower handles. So, N i of Example 1 of the present invention
-00 alloy plating, the results of a wristwatch with a rotor pinion treated using a treatment solution (D,) prepared by excluding the At fine powder from the treatment solution (A), are plotted as a polygonal line. A polygonal line E shows the results of a wristwatch incorporating a rotor pinion that was treated using a treatment liquid (E) prepared by excluding M2S and fine powder from the treatment liquid (A).

As is clear from Figure 2, B falls below the standard after the third year. The reason for this is that the first layer of the treatment was electroless N1 plating with a surface condition that does not have ultra-fine pores.
This is thought to be due to the lack of abrasion resistance due to insufficient adhesion with the layer. In addition, C is at a high level from the beginning until the 7th year, but after that the level drops rapidly and exceeds the standard after the 9th year. The main reason for this is thought to be deterioration of the lubricating ability due to oil leakage and deterioration over time. Alternatively, although it satisfies the standards from the initial stage to the seventh year, the level rapidly declines after that and eventually falls below the standards.

The main reason for this is that the M
Because the OS and fine powder do not chemically bond with the support of the second layer, adhesion is somewhat difficult, and the film may fall off due to impact force or scratching force during wear, making it impossible to ensure sufficient durability. Conceivable.

Furthermore, although E meets the standards from the initial stage to the 10th year, it is at the very edge of the standards and lacks safety. The main reason for this is that the metal fine powder used as the second layer's lubricating fine powder chemically bonds with the second layer's support and has sufficient adhesion and has excellent durability, but the lubricating performance is In particular, the coefficient of friction is considered to be lower than that of lubricating oil or MOS, and as a result, the output torque force, which is significantly affected by the coefficient of friction, becomes low. In contrast to these, A of the present invention is
As a lubricating fine powder, we use a combination of metal fine powder with excellent durability and M2S fine powder with a low coefficient of friction, and by compensating for the shortcomings of both and making use of their strengths, we can provide sufficient safety from the initial stage to the 10th year. It was confirmed that the lubrication treatment satisfies the standards and has high lubricity and durability.

Next, in order to measure the coefficient of kinetic friction of the treated film, a test piece for a pendulum type oil-based friction tester was treated with treatment liquid (A) I (D) I (Fri) in the same manner as the rotor kana.
The coefficient of dynamic friction was measured. The results are μ=115. α5
, 0.15, it was confirmed that this lubricant-treated film had sufficient lubricating performance.

Example 2 Carbon steel (carbon: 15
%) Mandarin duck and Kannuki pressed work with Vickers hardness of 600
A porous chromium plating film was formed on the surface using the following bath components and electrodeposition conditions.

Chromium plating bath components> 0rOB 30% TiN0. 5% Ba 2000P1'm ]]' 500PPm OH0OOH Trace electrodeposition conditions> Bath temperature -10°C Current density 1A/hour 3 〇- The plating thickness was 1.5 μm, and the surface was observed using an electron microscope. It was confirmed that there were many micropores.

Next, it was immersed in treatment liquid CB) having the following composition at room temperature for 4 minutes, then baked at 60°C for 10 minutes and further at 150°C for 100 minutes.

<Composition of treatment liquid CB)> Tetraethoxysilane...3f Tetraethoxytantalum...0.5f At fine powder (
Average particle size: 0.07 μm) ...0.2 fine powder (
Average particle size: 0.03μtlL)...[L1fBN fine powder (average particle size: 0.04μB)''・1.5 f Diflon 83...100mt The film thickness of the treated switching parts was usually 0.5μ The adhesion of the film was confirmed in the same manner as in Example 1, and it was found to be strong.Furthermore, in order to confirm the lubrication life of the film, the switching part was installed in a wristwatch, and the winding stem was pulled out. A durability test of repeated pushing operations was conducted.

The test conditions were as follows: 10 years' worth of operations were performed on the assumption that wristwatches were switched on the market an average of 100 times a year.

The force required to pull out and push in the winding stem (hereinafter abbreviated as switching force) was measured several times over the course of 10 years of operation, and the measured values were plotted with the horizontal axis representing the service life and the vertical axis representing the switching force. The results are plotted on a graph with a straight line connecting each point, and the result is represented by the line F in Figure 3.

Normally, when switching operations are performed for 10 years, the switching force during that period is required to be within a certain set standard.

As is clear from FIG. 3, Invention F satisfied the standards from the initial stage to the 10th year, and was confirmed to be an extremely durable lubrication process.

Next, when the coefficient of dynamic friction was measured in the same manner as in Example 1, it was found that μ==[Ll 7, which confirmed that the material had sufficient lubrication performance.

Examples & A date dial made of At, which is a component of a calendar display wristwatch, was subjected to alumite treatment for the purpose of improving strength and making the surface porous. In addition, electroless N1 plating with a regular thickness of 0.5 μm is applied to the phosphor bronze lever that frictionally slides on the spout.
Thereafter, under the same conditions as in Example 1, Ni-00 alloy plating was applied to a thickness of 2 μm. These parts were immersed in a treatment solution (0) with the following composition for 2 minutes at room temperature, and then immersed at 150°C for 1 minute.
It was baked for 0 minutes, and then for 60 minutes at 200°C.

Composition of treatment liquid (0)> Tetramethoxysilane...1t rglycidoxypropyltrimethoxysilane...1v Tetrabutoxyzirconium...0.51pb Fine powder (average particle size (approximately 103μ)...・0.1v8n fine powder (average particle size Q, 03μ) ... [L1F graphite fine powder (average particle size 0.03μ) ...2v Daiflon 8
3...The film thickness of the parts treated with 100 mm was 0.3 μ mm.

The adhesion of the film was confirmed in the same manner as in Example 1, and it was found to be sufficiently strong. Furthermore, in order to confirm the lubrication life of the film, the parts were assembled into a wristwatch and a mechanical durability test was conducted. The conditions for the test were to rotate the date wheel once a month for 10 years, that is, 120 times. The rotational torque (hereinafter referred to as jD) required to rotate the date wheel on the second wheel at several places during the 10-year rotation ρ process is abbreviated as r. ), and plot the measured values on a graph with the horizontal axis as durability years and the vertical axis as mechanical torque, and connect each point with a straight line.

The result is represented by the polygonal line G in FIG.

Normally, when the daily rotation of the wheel is repeated for 10 years, it is required that the index shift torque during that time be within a certain set standard.

As is clear from FIG. 4, Invention G satisfied the standards from the initial stage to the 10th year, and it was confirmed that the lubrication process was extremely durable.

Next, when the coefficient of dynamic friction was measured in the same manner as in Example 1, it was found that μ=1116, which confirmed that it had sufficient lubrication performance.

As described in the above examples, the lubrication properties of the sliding parts treated with the lubrication treatment according to the present invention are extremely stable over a long period of time, which cannot be obtained with conventional lubrication treatment techniques. It is something. In the examples, we specifically described the application to just a small part of the friction sliding part of an analog quartz wristwatch, but it can also be applied to the entire friction sliding part, such as a needle turning structure, a slow/sudden adjustment structure, or stabilizing the needle pushing force. be able to. Furthermore, lubricating oil is used or
It can be applied to frictional sliding parts of all precision instruments that are treated with solid lubrication other than the present invention, and by adopting the present invention, the need for intermittent lubrication, which is a drawback of conventional lubrication treatment, can be reduced. Problems such as variation and deterioration of initial quality in durability can be completely solved. As an example of precision equipment,
In addition to wristwatches, examples include optical equipment such as cameras, electronic equipment such as tape recorders and video-related equipment, medical equipment, office equipment, and combiator terminal equipment.

Further, the present invention is not limited to the base material being metal, but can also be applied to any materials such as ceramics and polymer materials.

As described above, by applying the lubrication treatment of the present invention to precision sliding parts, the reliability of various precision instruments can be ensured over a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of the product of the present invention. 1... Cross section of sliding part 2... Cross section of porous film 3
...Cross section of composite film 4...Metal fine powder 5...M
O8, fine powder Figure 2 is a graph showing changes in output torque in a train wheel durability test of an analog crystal wristwatch. In the figure, A shows a rotor pinion that has been treated according to Example 1 of the present invention, and B shows a rotor that has been treated with the treatment solution (A) directly on the electroless N1 plating for corrosion prevention of Example 1 of the present invention. 0 is the rotor pinion in which lubricating oil was applied on the electroless N1 plating for corrosion prevention of Example 1 of the present invention, and D is the N1-C of Example 1 of the present invention.
. A rotor pinion was treated on top of the alloy plating using a treatment solution prepared by excluding the hf fine powder from the composition of the treatment solution (A). Among the compositions of the treatment liquid (A), M08! The figure shows changes in the output torque of wristwatches each incorporating a rotor pinion treated with a treatment solution prepared by removing fine powder. FIG. 3 is a graph showing changes in switching force in a switching durability test of an analog crystal □ wristwatch. In the figure, F shows the change in switching force of a wristwatch incorporating a switching component processed according to Example 2 of the present invention. FIG. 4 is a graph showing changes in the clock shift torque during a shift durability test of an analog quartz wristwatch. In the figure, G indicates a change in the indexing torque of a wristwatch incorporating a date dial and a date lever which were subjected to the treatment of Example 3 of the present invention. Applicant Suwa Seikosha Co., Ltd. Agent Patent Attorney Mogami Muri 2 Zu Shoj Hokuhi (Meishi 3ffi Jukai 7M Gumcu Procedural Amendment Import) 1. Description of the case 1982 Patent Application No. 177501 2 Name of the invention Precision sliding parts 3 Person making the amendment (236) Suwa Seikosha Co., Ltd. 2-6-21-5 Kyobashi, Chuo-ku, Tokyo 104 Japan , number of inventions increased by amendment 6, specification subject to amendment, drawing procedure amendment (voluntary), page 10 of the specification, line 10, changed the phrase “different degrees of burnability v4” to “different degrees of burnability v4”. to correct. 2. On page 12, line 12 of the specification, the phrase ``Matabe and Yuwa'' is amended to read ``Matabe and Yuwa''. 3. On page 20 of the specification, line 5, "Sunday side" should be amended to "Sunday side." Akinu 1st Co., page 23, line 11 [uos2J is corrected to "lubrication side". Figure 4 is corrected as shown in the attached sheet. that's all

Claims (1)

[Claims] The following components (A) * (B) are applied to the surface of a precision sliding component whose surface is coated with an ultrafine porous film. A precision sliding component characterized by being coated and cured with a mixture containing at least (C) and (D). (A) General formula (1>R% -8l-fORl), -
(Hl is an epoxy group, a methacryloxy group, a vinyl group, a mercapto group, an organic group containing chlorine, hydrogen, or an alkyl group having 1 to 4 carbon atoms, and R2 is a silicon compound having 1 to 8 carbon atoms. represents an alkyl group, and α is 0 to 3.) CB) A metal alcoholade compound represented by the general formula (2) M(OR'')4 (R2 is as described above, M is a compound of the periodic table ■, Or it represents an atom of group V.) (0) Au@Ag, Ou, I
At least one metal fine powder selected from Eln, Pb, and Eln having an average particle size of 1 μm or less. CD) At least one lubricating fine powder selected from sulfides, selenides, tellurides, nitrides and graphite having an average particle size of 1 μm or less.