JP2007127263A - Rolling member and rolling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolling member and a rolling device functioning under such conditions that a large contacting stress is applied or even without lubrication. <P>SOLUTION: A thrust ball bearing is equipped with an inner ring 1, an outer ring 2, and a plurality of balls 3. They 1, 2, 3 are formed from a steel material containing 0.5-1.2 mass% carbon, 0.5-1.5 mass% silicon, 0.1-2 mass% manganese, and 1-2.5 mass% chromium, the remainder being iron and inevitable impurities, and DLC layers D having lubricity are provided on the raceway surfaces 1a and 2a of the inner 1 and outer rings 2 and the rolling surfaces 3a of the balls 3. Each DLC layer D is composed of a metal layer M consisting of two or more elements selected among Cr, W, Ti, Si, Ni, and Fe, a composite layer F consisting of the named metals and carbon, and a carbon layer C consisting of carbon, in such an arrangement as C, F, and M from the obverse surface. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a rolling member excellent in lubricity and a rolling device constituted by the rolling member, and in particular, a rolling member that can be suitably used under conditions where a large contact stress acts and under no lubrication, and The present invention relates to a rolling device.

Diamond-like carbon (hereinafter sometimes referred to as DLC) has a hardness similar to that of diamond, and its sliding resistance is as low as 0.2 or less, like molybdenum disulfide and fluororesin. Therefore, it has been conventionally used as a lubricating material.
For example, in a magnetic disk device, by forming a DLC film of several tens of angstroms on the surface of the magnetic element or the magnetic disk, the lubricity between the magnetic element and the magnetic disk is improved to protect the surface of the magnetic disk. Yes.

On the other hand, DLC has attracted attention as a new lubrication material for rolling members because of its unique surface properties as described above, and has recently been used to impart lubricity to bearings.
For example, Patent Document 1 discloses a rolling bearing including a DLC film containing metal on the raceway surface of a raceway or the surface of a rolling element. In this rolling bearing, the contact stress is relieved by the DLC film.

In addition, rolling devices such as rolling bearings in which a DLC film is formed on the raceway surface of the raceway or the surface of the rolling element by a CVD method, a plasma CVD method, an ion beam forming method, an ionized vapor deposition method, or the like are known (for example, And Patent Documents 2 to 6).
International Publication No. WO99 / 14512 Japanese Patent Laid-Open No. 9-147464 JP 2000-136828 A JP 2000-205277 A JP 2000-205279 A JP 2000-205280 A

However, in a rolling device such as a rolling bearing, since a large contact stress acts on the raceway surface of the raceway and the surface of the rolling element, the DLC film may be damaged by repeated stress.
The following two points can be considered as causes of such damage.
First, the first point is a problem of embrittlement of the metal intermediate layer interposed in order to improve the adhesion between the steel and the DLC film. That is, since the metal constituting the metal intermediate layer and the carbon constituting the DLC film are combined to produce brittle metal carbide, the metal intermediate layer becomes brittle and the DLC film is easily damaged. And when a metal intermediate layer is comprised with 1 type of metal, since the brittleness of a metal carbide is large, it is easy to become a factor of a failure | damage.

The second problem is that the DLC film has a property of being hardly deformed even when stress is applied. Since DLC is hard and highly elastic, if it is covered with a metal material having a small equivalent elastic constant such as stainless steel or bearing steel, the DLC follows the deformation of the base material due to the difference in the equivalent elastic constant between the two. In some cases, the DLC film may be damaged.
Therefore, the present invention has an object to solve the above-mentioned problems of the prior art and to provide a rolling member that can be suitably used even under conditions where a large contact stress acts or under no lubrication. To do. It is another object of the present invention to provide a rolling device having such a rolling member and having excellent lubricity.

  In order to solve the above problems, the present invention has the following configuration. That is, the rolling member according to claim 1 according to the present invention has carbon of 0.5 mass% to 1.2 mass%, silicon of 0.5 mass% to 1.5 mass%, and manganese of 0.1 mass. % To 2% by mass, chromium containing 1% to 2.5% by mass, the balance being made of steel and steel that is an inevitable impurity, and relative rolling contact with the mating member or In a rolling member in which sliding contact occurs, a diamond-like carbon layer having lubricity is provided on a contact surface with the counterpart member, and the diamond-like carbon layer is made of chromium, tungsten, titanium, silicon, nickel, and iron. It is composed of three layers of a metal layer made of two or more metals, a composite layer made of the metal and carbon, and a carbon layer made of carbon, and the carbon layer, the composite layer, Characterized in that arranged in the order of the genus layer.

In such a rolling member, since the composite layer and the metal layer are interposed between steel as a base material and the carbon layer, the diamond-like carbon layer (hereinafter referred to as a DLC layer) having excellent lubricity. The adhesion between the base material and steel is excellent.
The composite layer is composed of two or more metals and carbon of chromium (Cr), tungsten (W), titanium (Ti), silicon (Si), nickel (Ni), and iron (Fe). Therefore, the brittleness of the metal carbide generated by the bond between the metal and carbon is small as compared with the case where it is composed of one kind of metal and carbon. Therefore, since the composite layer is small in brittleness, the DLC layer is not easily damaged even when repeated stress or shearing force is applied. In addition, it is preferable to combine the metals to be used have different stoichiometric ratios with carbon.

Moreover, the rolling member of Claim 2 which concerns on this invention is a rolling member of Claim 1, The ratio of the carbon in the said composite layer is increasing toward the said carbon layer side from the said metal layer side. It is characterized by that. With such a configuration, the adhesion between the DLC layer and the base steel is more excellent.
Furthermore, a rolling member according to a third aspect of the present invention is characterized in that, in the rolling member according to the first or second aspect, the equivalent elastic constant of the diamond-like carbon layer is 100 GPa or more and 240 GPa or less.

With such a configuration, since the DLC has a smaller equivalent elastic constant than the steel as the base material, the DLC layer can be deformed when a repeated stress is applied. As a result, since the DLC layer can follow the deformation of the base material, the DLC layer is hardly damaged.
If the equivalent elastic constant of the DLC layer exceeds 240 GPa, the DLC layer has a larger equivalent elastic constant than the steel, so the DLC layer follows the deformation of the base material when repeated stress is applied. This makes it difficult to damage the DLC layer. On the other hand, if it is less than 100 GPa, the hardness of the DLC layer becomes low and wear tends to occur.

For a thin film such as a DLC layer, the elastic constant cannot be measured by a normal method. Therefore, in the present invention, an equivalent elastic constant based on the elastic constant measured by the following method is used. That is, the indentation depth is at least within the thickness of the DLC layer, measurement is performed with a microhardness meter, and the equivalent elastic constant is obtained from the obtained load-unloading curve.
For example, when the thickness of the DLC layer is 1 μm or less, the indentation load is appropriately set between 0.4 to 20 mN and the measurement is performed. In the present invention, an equivalent elastic constant measured using a microhardness meter manufactured by Elionix Co., Ltd. and an indentation load of 20 mN is used.

As another method for measuring the equivalent elastic constant, there is a method using a micro hardness measuring device manufactured by Fischer. In this method, it is desirable not to use a (micro) Vickers hardness tester but to use a micro hardness tester or a nano indentator that can be controlled by capacitance. In addition, the indentation depth needs to be within the thickness of the DLC layer. And an equivalent elastic constant is calculated | required from the amount of elastic deformation of the load-unloading curve obtained by the said micro hardness meter or the nano indentator.
In addition, when the equivalent elastic constant of the surface of the high carbon chromium steel (SUJ2) of HRC60 is calculated | required by said method, it will be 250 GPa and will be a result larger than 210 GPa normally described in the catalog etc. This is because the above method is a measurement in a minute indentation region, and is therefore influenced by the work hardening layer on the surface of SUJ2.

Furthermore, the rolling member according to claim 4 according to the present invention is the rolling member according to any one of claims 1 to 3, wherein the diamond-like carbon layer is formed by sputtering using a non-equilibrium magnetron. It is characterized by being.
Such a physical film forming method is easy to obtain a DLC layer having a suitable equivalent elastic constant and strength as compared with CVD method, plasma CVD method, ion beam forming method, ionized vapor deposition method, etc. It is suitable for a part constituting a device such as a device on which large contact stress acts.

  As described above, since the rolling member of the present invention includes a lubricating film (DLC layer) that is not easily damaged even when a large contact stress is applied, a device (for example, a rolling tool for a machine tool spindle) that is subjected to a large contact stress. The present invention can be suitably applied to members constituting a rolling device such as a bearing. In addition, since it has excellent lubricity, it can be suitably used even without lubrication. For example, the present invention can be suitably applied to members constituting non-lubricated bearings used under vacuum. In addition, there is little wear and heat generation, and it is strong against repeated stress and has a long life.

  Furthermore, the rolling device according to claim 5 of the present invention has an inner member having a raceway surface on the outer surface and a raceway surface facing the raceway surface of the inner member on the inner surface, and the outer side of the inner member. In the rolling device comprising an outer member disposed on the rolling surface and a rolling element disposed so as to be able to roll between the both raceway surfaces, at least one of the inner member, the outer member, and the rolling element. One is a rolling member according to any one of claims 1 to 4.

With such a configuration, the DLC layer of the rolling member constituting the rolling device is not easily damaged even when a large contact stress is applied, and is therefore used under conditions where a large contact stress is applied or under no lubrication. Even long life.
Examples of the rolling device of the present invention include a rolling bearing, a linear motion guide bearing (linear guide device), a ball screw, and a linear motion bearing.

  The inner member is an inner ring in the case where the rolling device is a rolling bearing, a guide rail in the case of a linear guide bearing, a screw shaft in the case of a ball screw, and a shaft in the case of a linear bearing. Each means. In addition, the outer member is an outer ring when the rolling device is a rolling bearing, a slider when the same is a linear guide bearing, a nut when it is a ball screw, and an outer cylinder when it is also a linear bearing. means.

Here, steel as a base material will be described.
[About silicon content]
Since rolling devices such as rolling bearings are required to withstand high surface pressure, rolling members such as bearing rings constituting the rolling device are made of steel such as SUJ2 and SCR420, and further carburized and carbonitrided. Etc. are subjected to curing treatment. However, when sputtering using such a non-equilibrium type magnetron is performed on such steel, the processing is high temperature, so that the retained austenite decomposes during the formation of the metal layer, and the steel and DLC layer that are the base materials There is an inconvenience that strong adhesion does not easily occur.

In order to secure the amount of retained austenite and eliminate the inconveniences as described above, the silicon content in the steel needs to be 0.5% by mass or more. In addition, silicon acts as a deoxidizer during steelmaking, and improves the hardenability and temper softening resistance, and has the effect of strengthening the base martensite and improving the life.
However, when there is too much content of silicon, the metal of a metal layer and silicon react at the time of formation of a metal layer, and an intermetallic compound produces | generates. Since this intermetallic compound is brittle, the adhesion between the base material steel and the DLC layer is lowered, and the strength of the DLC layer is lowered. Moreover, when there is too much content of silicon, there exists a possibility that the machinability, forgeability, and cold workability of steel may fall remarkably. In order to make these inconveniences difficult to occur, the silicon content in the steel needs to be 1.5% by mass or less.

  It is also possible to reduce the amount of retained austenite by subjecting steel such as SUJ2 and SCR420 to a high temperature, thereby preventing decomposition of the retained austenite in the subsequent high temperature treatment (treatment for forming a DLC layer). However, tempering at a high temperature is not preferable because it causes a decrease in the hardness of the steel. Moreover, although the method of reducing a retained austenite amount by subzero treatment is also considered, there exists a possibility that the fall of the hardness of steel may arise in subsequent high temperature processing. Furthermore, although a method using high alloy steel such as stainless steel and M50 as a base material is also conceivable, there is a problem that these high alloy steels are expensive. Therefore, it is preferable to use steel having a silicon content of 0.5 mass% or more and 1.5 mass% or less as a base material.

[Carbon content]
In order to obtain steel cleanliness required as a rolling bearing, the carbon content needs to be 0.5 mass% or more. However, if it exceeds 1.2% by mass, the retained austenite may increase, and the dimensional stability of the rolling bearing may be reduced, or eutectic carbide may be generated and the life may be shortened. In order to improve the cleanliness of steel and prevent the generation of excessive retained austenite and eutectic carbide, the carbon content is preferably 0.75 mass% or more and 1.1 mass% or less.

[About manganese content]
Like manganese, manganese acts as a deoxidizer during steelmaking, so the manganese content must be 0.1% by mass or more. Manganese also enhances the hardenability of steel and contributes to the improvement of strength after heat treatment and rolling fatigue strength. However, if it exceeds 2% by mass, residual austenite that is harmful to dimensional stability may be generated or processability may be deteriorated.

[Chromium content]
Chromium is an element that enhances the hardenability of steel and contributes to the improvement of strength after heat treatment and rolling fatigue strength, so the chromium content needs to be 1% by mass or more. However, when it exceeds 2.5% by mass, there is a possibility that the processability may be deteriorated or a problem that eutectic carbide is generated may occur.

  A diamond-like carbon layer having a composite layer composed of two or more metals and carbon has excellent adhesion and small brittleness. Therefore, the rolling member and the rolling device of the present invention can be suitably used under conditions where a large contact stress acts or under no lubrication. In addition, since the equivalent elastic constant of the diamond-like carbon layer is 100 GPa or more and 240 GPa or less, the diamond-like carbon layer is not easily damaged even when repeated stress is applied.

DESCRIPTION OF EMBODIMENTS Embodiments of a rolling member and a rolling device according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a longitudinal sectional view showing a configuration of a thrust ball bearing which is an embodiment of a rolling device according to the present invention, and FIG. 2 is a partially enlarged sectional view showing an enlarged portion A of FIG. is there.
1 includes an inner ring 1 having a raceway surface 1a, an outer ring 2 having a raceway surface 2a opposite to the raceway surface 1a, and a plurality of rolls disposed between both raceway surfaces 1a and 2a. A ball 3 and a cage 4 that holds a plurality of balls 3 between the raceway surfaces 1a and 2a evenly over the circumferential direction of the bearing are provided.

Inner ring 1, outer ring 2, and ball 3 are carbon 0.5 mass% to 1.2 mass%, silicon 0.5 mass% to 1.5 mass%, manganese 0.1 mass% to 2 mass% It is made of steel containing 1% by mass or more and 2.5% by mass or less of chromium with the balance being iron and inevitable impurities.
Furthermore, a diamond-like carbon (DLC) layer having lubricity and an equivalent elastic constant of 100 GPa or more and 240 GPa or less is provided on the raceway surface 1a of the inner ring 1, the raceway surface 2a of the outer ring 2, and the rolling surface 3a of the ball 3. D is provided. As shown in FIG. 2, the DLC layer D includes a metal layer M made of two or more metals of Cr, W, Ti, Si, Ni, and Fe, and a composite layer made of the metal and carbon. F and a carbon layer C made of carbon are formed. The three layers are formed in the order of the carbon layer C, the composite layer F, and the metal layer M from the surface side.

Next, a method for forming the DLC layer D will be described using the outer ring 2 as an example.
The outer ring 2 from which the oil was degreased was placed in an unbalanced magnetron sputtering apparatus (hereinafter referred to as a UBMS apparatus), and bombarding was applied to the raceway surface 2a for 15 minutes using sputtering by argon plasma.
Then, using tungsten and chromium as targets, the two kinds of metals were sputtered onto the raceway surface 2a to form a metal layer M. Next, while continuing the sputtering of these two kinds of metals, the sputtering of carbon using carbon as a target was started. A composite layer F made of metal carbide in which the two kinds of metals and carbon were bonded was formed on the metal layer M by such sputtering.

Furthermore, the sputtering efficiency of carbon was gradually increased while gradually decreasing the sputtering efficiency of the two kinds of metals. Then, the sputtering of the two kinds of metals was finished, and the carbon layer C was formed on the composite layer F only for carbon sputtering (the thickness of the entire DLC layer D was 2.2 μm).
When film formation is performed by such sputtering, the composition of the layer gradually gradually increases from the layer composed of two kinds of metals (metal layer M) toward the layer composed of carbon (carbon layer C). A changing DLC layer D can be formed. The DLC layer D having such a structure is composed of a carbon layer C and a base material having excellent lubricity as well as excellent adhesion between each layer (metal layer M, composite layer F, and carbon layer C). Adhesion with certain steel is very good.

  The UBMS apparatus can be equipped with a plurality of targets used for sputtering, and can control the sputtering efficiency of each component arbitrarily by independently controlling the sputtering power source of each target. is there. For example, in the process of forming the composite layer F and the carbon layer C in the above case, the power of the sputtering power source (DC power source) of the carbon target is simultaneously reduced while the power of the sputtering power source (DC power source) of the metal target is reduced. (At this time, a negative bias voltage is applied to the outer ring 2).

The equivalent elastic constant of the DLC layer can be changed by controlling the bias voltage applied to the outer ring or by controlling the partial pressure of the introduced gas. By controlling the type and partial pressure ratio of the introduced gas (hydrocarbon gas such as argon, hydrogen, methane, etc.), it is possible to freely control the sliding resistance of the surface as well as the equivalent elastic constant of the DLC layer. A desired DLC layer suitable for the purpose can be formed by introducing the gas alone or in combination. Furthermore, the thickness of the DLC layer can be accurately controlled by the sputtering time.
Here, the result of analyzing the elements forming the DLC layer D using a glow discharge emission spectrometer is shown in the measurement chart of FIG. The horizontal axis of the chart indicates the depth from the surface, and 0 μm means the surface of the DLC layer. Moreover, the vertical axis | shaft has shown content of each element in the depth position.

  In addition, since the information of the depth direction is obtained by the discharge using argon gas, the curve which shows content of each element is broad in the interface of steel and DLC layer D which are base materials. In addition, since the interface between the steel and the DLC layer D is located near 8000 nm, it can be seen from this chart that the thickness of the DLC layer D is about 8 μm. Therefore, the thickness of the actual DLC layer D is 2.2 μm.

In addition, this embodiment shows an example of this invention and this invention is not limited to this embodiment.
For example, in the present embodiment, the DLC layer is formed by sputtering using a non-equilibrium magnetron, but a pulsed laser arc deposition method, a plasma CVD method, or the like can also be used. However, sputtering using a non-equilibrium magnetron that can easily control the equivalent elastic constant, plastic deformation hardness, and the like is most preferable.

In the present embodiment, the thrust ball bearing has been described as an example, but the rolling device of the present invention can be applied to various rolling bearings. For example, radial type rolling bearings such as deep groove ball bearings, angular contact ball bearings, cylindrical roller bearings, tapered roller bearings, needle roller bearings, and self-aligning roller bearings, and thrust type rolling bearings such as thrust roller bearings .
Further, in the present embodiment, the rolling bearing is exemplified as the rolling device, but the rolling device of the present invention can be applied to various other types of rolling devices. For example, the present invention can be suitably applied to other rolling devices such as a linear motion guide bearing, a ball screw, and a linear motion bearing.

〔Example〕
Hereinafter, the present invention will be described more specifically with reference to examples. In the bearing having the same configuration as the thrust ball bearing of FIG. 1 described above, a test bearing with various changes in the composition of steel as a base material is prepared (see Table 1), and a durability test for evaluating the life of the bearing is performed. went.

In addition, after shaping | molding steel in the shape of each member, quenching (heating is performed in RX gas and cooling is oil cooling) and tempering at 160-320 degreeC are performed. It is not limited to such quenching, and carburizing or carbonitriding may be performed.
Further, the DLC layer was formed only on the raceway surfaces of the inner ring and the outer ring, and was not formed on the rolling surface of the balls. Furthermore, the thickness of the DLC layer is 2.2 μm. Furthermore, the inner and outer rings of the thrust ball bearing have an inner diameter of 25 mm, an outer diameter of 52 mm, and a thickness of 18 mm. is there. Furthermore, the number of balls arranged between the raceway surfaces of the inner and outer rings is six, and the cage is made of brass.
The conditions of the durability test are as follows.
Rotational speed: 3000min ^-1
Load: 45% of dynamic load rating (P / C = 0.45)
Ambient temperature: Room temperature (about 28 ° C)
Bearing temperature: 100 to 110 ° C. at the outer diameter of the outer ring (lower race)
Lubricating oil: Kinematic viscosity at 40 ° C. of 32 mm ² / s

  The test bearing was rotated under the above conditions, and the time until the DLC layer was damaged or seizure occurred was measured. The damage of the DLC layer was determined as follows. When the frequency reached twice the initial value, the rotation was interrupted, and it was confirmed with a stereomicroscope whether a metallic luster was observed on the running trace of the DLC layer. When the metallic luster was observed and the component (iron) of the base material was detected by analysis using an electron beam microanalyzer (EPMA), it was determined that the DLC layer was damaged. Further, it was determined that seizure occurred when the bearing temperature reached 150 ° C.

Ten durability tests were performed for each type of test bearing, and the average value was defined as the life. The results are shown in Table 1 and the graph of FIG. In addition, the numerical value of the lifetime described in the graph of Table 1 and FIG. 4 is shown by the relative value when the lifetime of the test bearing of the comparative example 1 is set to 1. As can be seen from the graph, in the bearings of the examples, the steel as the base material contains silicon in an amount of 0.5% by mass or more and 1.5% by mass or less, and therefore the silicon content in the steel falls within the above range. The service life was superior to the bearing of the comparative example, which was off.
Next, another embodiment will be described. Test bearings with various changes in the composition of the base steel are prepared (see Table 2) for the bearings having the same structure as the thrust ball bearing shown in FIG. An endurance test was conducted to evaluate

  The DLC layer was formed only on the rolling surface of the ball, and not on the raceway surfaces of the inner ring and the outer ring. The thickness of the DLC layer is 2.2 μm. Furthermore, the inner and outer rings of the thrust ball bearing have an inner diameter of 25 mm, an outer diameter of 52 mm, and a thickness of 18 mm, and the raceways of the inner and outer rings have an arc shape having a curvature radius of 54% of the ball diameter. is there. Further, the number of balls arranged between the raceway surfaces of the inner and outer rings is three, and the cage is made of brass.

  Here, the manufacturing method of the ball | bowl which has a DLC layer is demonstrated. First, an element ball was manufactured from a steel wire by header processing, flushing processing, and rough turning processing, and the following heat treatment was performed. That is, after carbonitriding and quenching at 830 ° C. for 3 hours in a mixed gas atmosphere of RX gas, enriched gas, and ammonia gas, tempering was performed at 160 to 270 ° C. Since such carbonitriding and quenching is performed, 5% by volume or more and 20% by volume or less of retained austenite exists in the surface layer portion of the ball.

  In addition, it is not limited to such carbonitriding and quenching, and carburizing and quenching may be performed. As an example of carburizing and quenching, there is a process in which carburizing and quenching is performed at 840 ° C. for 3 hours in a mixed gas atmosphere of RX gas and enriched gas, and then tempering is performed at 160 to 320 ° C. Further, as an example of the so-called quenching, there is a process of quenching at 840 ° C. for 0.5 hours in an RX gas atmosphere and then tempering at 160 to 320 ° C.

After the heat treatment as described above, tumbler treatment (barrel treatment) was performed, and tempering was further performed at 150 to 170 ° C. Then, lapping was performed until the surface roughness Ra became 0.01 μm or less, and the same treatment as described above was further performed to form a DLC layer on the surface to obtain a completed sphere.
The conditions of the durability test are as follows.
Rotational speed: 1000min ^-1
Load: 45% of dynamic load rating (P / C = 0.45)
Ambient temperature: Room temperature Lubricating oil: Turbine oil whose ISO viscosity grade is ISO VG68 However, the lubricating oil contains 300 ppm of Fe ₃ C-based powder as foreign matter. The hardness of the Fe ₃ C-based powder is HRC52, and the particle size is 74 to 147 μm.

The test bearing was rotated under the above conditions, and the time until the DLC layer was damaged or seizure occurred was measured. In addition, when the frequency became 5 times the initial value, it was determined that the DLC layer was damaged. When the bearing temperature reached 150 ° C., it was determined that seizure occurred.
Ten durability tests were performed for each type of test bearing, and the average value was defined as the life. The results are shown in Table 2 and the graph of FIG. In addition, the numerical value of the lifetime described in the graph of Table 2 and FIG. 5 is shown by the relative value when the lifetime of the test bearing of the comparative example 11 is set to 1.

As can be seen from the graph, in the bearings of Examples 11 to 22, the steel as the base material contains 0.5 mass% or more and 1.5 mass% or less of silicon, so that the silicon content in the steel is high. The service life was superior to the bearings of Comparative Examples 13 to 15 outside the above range.
Further, as can be seen from Examples 14 to 19 in Table 2, bearings having a retained austenite amount on the rolling surface of the ball of 5% by volume or more and 20% by volume or less have excellent durability even under lubrication mixed with foreign matter. The amount of retained austenite was longer than that of the above range.

It is a longitudinal section showing the composition of the thrust ball bearing which is one embodiment of the rolling device concerning the present invention. It is the elements on larger scale which expanded and showed the A section of FIG. It is the measurement chart which analyzed the element which forms a DLC layer. It is a graph which shows the correlation with content of the silicon in steel, and the lifetime of a bearing. It is a graph which shows the correlation with content of the silicon in steel, and the lifetime of the bearing under foreign material mixing lubrication.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inner ring 1a Raceway surface 2 Outer ring 2a Raceway surface 3 Ball 3a Rolling surface D Diamond-like carbon layer M Metal layer F Composite layer C Carbon layer

Claims (5)

0.5% to 1.5% by mass of carbon, 0.5% to 1.5% by mass of silicon, 0.1% to 2% by mass of manganese, 1% to 2% of chromium In a rolling member containing 5% by mass or less, the balance being made of iron and steel, which is an inevitable impurity, and causing relative rolling contact or sliding contact with the counterpart member,
Provide a diamond-like carbon layer having lubricity on the contact surface with the counterpart member,
The diamond-like carbon layer includes a metal layer composed of two or more metals of chromium, tungsten, titanium, silicon, nickel, and iron, a composite layer composed of the metal and carbon, a carbon layer composed of carbon, It consists of three layers
A rolling member, wherein the carbon layer, the composite layer, and the metal layer are arranged in this order from the surface side.   The rolling member according to claim 1, wherein a ratio of carbon in the composite layer increases from the metal layer side toward the carbon layer side.   The rolling member according to claim 1 or 2, wherein an equivalent elastic constant of the diamond-like carbon layer is 100 GPa or more and 240 GPa or less.   The rolling member according to any one of claims 1 to 3, wherein the diamond-like carbon layer is formed by sputtering using a non-equilibrium magnetron.   An inner member having a raceway surface on the outer surface, an outer member having a raceway surface facing the raceway surface of the inner member on the inner surface and disposed outside the inner member, and the two raceway surfaces In a rolling device provided with rolling elements arranged so that rolling is possible, at least one of the inner member, the outer member, and the rolling elements is given in any 1 paragraph of Claims 1-4. A rolling device characterized by being a rolling member as described.

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