JP5620860B2 - Rolling bearing - Google Patents

Description

  The present invention relates to a rolling bearing in which a hard film containing diamond-like carbon is formed on an inner ring raceway surface, an outer ring raceway surface, and a rolling element surface.

  The hard carbon film is a hard film generally called diamond-like carbon (hereinafter referred to as DLC. A film / layer mainly composed of DLC is also referred to as a DLC film / layer). In addition, hard carbon has various names such as hard amorphous carbon, amorphous carbon, hard amorphous carbon, i-carbon, diamond-like carbon, and these terms are not clearly distinguished.

  The essence of DLC in which such terms are used is structurally an intermediate structure of both diamond and graphite mixed. It is as hard as diamond and has excellent wear resistance, solid lubricity, thermal conductivity, chemical stability, and corrosion resistance. For this reason, for example, it is being used as a protective film for molds / tools, wear-resistant mechanical parts, abrasives, sliding members, magnetic / optical parts, and the like. As a method for forming such a DLC film, physical vapor deposition (hereinafter referred to as PVD) such as sputtering or ion plating, chemical vapor deposition (hereinafter referred to as CVD), unbalanced magnetron sputtering ( Hereinafter, a method such as UBMS) is employed.

  Conventionally, an attempt has been made to form a DLC film on a raceway surface of a bearing ring of a rolling bearing or a rolling surface of a rolling element. DLC films generate extremely large internal stress during film formation, and have high hardness and Young's modulus, but their deformability is extremely small, so they have the disadvantages of poor adhesion to the substrate and easy peeling. ing. For this reason, when a DLC film is formed on the raceway surface of the bearing ring of the rolling bearing or the rolling surface of the rolling element, it is necessary to improve the adhesion.

  For example, assuming that the adhesion of the DLC film is improved by providing an intermediate layer, chromium (hereinafter referred to as Cr), tungsten (hereinafter referred to as W) is formed on the raceway groove formed of a steel material or the rolling surface of the rolling element. ), Titanium (hereinafter referred to as Ti), silicon (hereinafter referred to as Si), nickel, and an underlayer having a composition containing at least one element of iron, and the constituent elements and carbon of the underlayer And a diamond-like carbon layer comprising an intermediate layer that is larger than the base layer side on the opposite side of the base layer, and has a carbon content of 0.02% by mass to 5% by mass with argon and carbon. However, a rolling device formed in this order has been proposed (see Patent Document 1).

  Also, assuming that the adhesion of the DLC film is improved by the anchor effect, irregularities with a height of 10 to 100 nm and an average width of 300 nm or less are formed on the orbital surface by ion bombardment, and a DLC film is formed on the orbital surface. A rolling bearing has been proposed (see Patent Document 2).

Japanese Patent No. 4178826 Patent No. 3961739

  However, the raceway surfaces of the inner and outer rings that guide the rolling elements in the rolling bearing have a curved surface instead of a flat surface, and some have a shape in which the main curvature and the sub curvature are combined. The rolling surface of the rolling element is a circumferential surface in the case of cylindrical rollers and a spherical surface in the case of balls. When a DLC film is formed on such a surface, the residual stress in the film increases depending on the film structure and film formation conditions, and there is a possibility of peeling immediately after the film formation. Even if the film does not peel off immediately after film formation, it may peel off when subjected to a load such as rolling contact during use of the bearing.

  The techniques of Patent Document 1 and Patent Document 2 are intended to solve this problem, but in order to improve the practicality of the obtained rolling bearing, the film structure and film formation conditions when applying the DLC film are changed. There is room for further improvement.

  The present invention has been made to cope with such a problem, and improves the peel resistance of the DLC film formed on the inner and outer ring raceways of the rolling bearing and exhibits the original characteristics of the DLC film. Thus, an object of the present invention is to provide a rolling bearing having excellent seizure resistance, wear resistance, and corrosion resistance.

  The rolling bearing of the present invention includes an inner ring having an inner ring raceway surface on the outer periphery, an outer ring having an outer ring raceway surface on the inner periphery, and a plurality of rolling elements that roll between the inner ring raceway surface and the outer ring raceway surface. A rolling bearing in which the inner ring, the outer ring, and the plurality of rolling elements are made of a ferrous material, and the inner ring raceway surface and the outer ring raceway surface are curved surfaces that guide the rolling element, the inner ring raceway A hard film is formed on at least one surface selected from the surface, the outer raceway surface, and the rolling surface of the rolling element, and the hard film is mainly composed of Cr formed directly on the surface. A mixed layer mainly composed of tungsten carbide (hereinafter referred to as WC) and DLC formed on the underlying layer, and mainly DLC formed on the mixed layer. And the mixed layer is a top layer. A layer in which the content of WC in the mixed layer decreases and the content of DLC in the mixed layer increases in a continuous or stepwise manner from the base layer side to the surface layer side. To do.

  The rolling element is a ball, and the inner ring raceway surface and the outer ring raceway surface are circular curved surfaces that guide the rolling element.

  The surface layer has an inclined layer portion whose hardness increases continuously or stepwise from the mixed layer side on the side adjacent to the mixed layer.

  The surface layer is a layer formed using a UBMS apparatus using argon (hereinafter referred to as Ar) gas as a sputtering gas, and a graphite target and a hydrocarbon-based gas are used in combination as a carbon supply source. The ratio of the introduction amount of the hydrocarbon-based gas to the introduction amount 100 of Ar gas into the device is 1 to 5, the degree of vacuum in the device is 0.2 to 0.8 Pa, and becomes a substrate. The film is formed by depositing carbon atoms generated from the carbon supply source on the mixed layer under the condition that the bias voltage applied to the bearing member is 70 to 150V. Further, the hydrocarbon gas is methane gas.

  The bias potential for the bearing member serving as the base material is applied so as to be negative with respect to the ground potential. For example, the bias voltage of 150 V is that the bias potential of the base material is −150 V with respect to the ground potential. Indicates that

  The inclined layer portion of the surface layer is formed by increasing a bias voltage applied to a bearing member serving as a base material continuously or stepwise.

  The underlayer and the mixed layer are layers formed using a UBMS apparatus using Ar gas as a sputtering gas, and the mixed layer is formed on a graphite target serving as a carbon supply source continuously or stepwise. The film is formed while increasing the sputtering power applied and decreasing the power applied to the WC target.

The hard film is brought into contact with SUJ2 hardened steel having a surface roughness Ra of 0.01 μm or less and a Vickers hardness Hv of 780 by applying a load with a maximum contact surface pressure of 0.5 GPa of Hertz. The specific wear amount of the hard film is less than 200 × 10 ⁻¹⁰ mm ³ / (N · m) when the counterpart material is rotated for 30 minutes at a rotational speed of 05 m / s. The hard film is characterized in that the sum of the average value of the indentation hardness and the standard deviation value is 25 to 45 GPa. The hard film has a critical peel load in a scratch test of 50 N or more.

  The hard film has a thickness of 0.5 to 3 μm, and the ratio of the thickness of the surface layer to the thickness of the hard film is 0.8 or less.

  The iron-based material is selected from high carbon chromium bearing steel, carbon steel, tool steel, and martensitic stainless steel. Further, the surface on which the hard film is formed has a Vickers hardness of Hv650 or more.

  In the surface on which the hard film is formed, a nitride layer is formed by nitriding before the hard film is formed. In particular, the nitriding treatment is a plasma nitriding treatment. Further, the surface hardness after the nitriding treatment is characterized in that the Vickers hardness is Hv1000 or more.

  The surface roughness Ra of the surface on which the hard film is formed is 0.05 μm or less.

  The rolling bearing is characterized in that grease is enclosed.

  The rolling bearing of the present invention includes DLC on at least one surface selected from the inner ring raceway surface, the outer ring raceway surface, and the rolling surface of the rolling element in the inner ring, outer ring, and rolling element made of a ferrous material. A hard film having a predetermined film structure is formed. The underlayer made of Cr formed directly on each surface has good compatibility with the iron-based material, and has better adhesion than W or Si. In addition, WC used for the mixed layer has intermediate hardness and elastic modulus between Cr and DLC, and concentration of residual stress after film formation hardly occurs. Further, the mixed layer of WC and DLC has a gradient composition, so that WC and DLC are physically coupled.

  With the above structure, the hard film has excellent peeling resistance while being formed on the curved inner and outer ring raceway surfaces and the rolling surface of the rolling element, and can exhibit the original characteristics of DLC. As a result, the rolling bearing of the present invention has excellent seizure resistance, wear resistance, and corrosion resistance, and has a long life with little damage to the raceway surface even under severe lubrication conditions.

It is sectional drawing which shows an example of the rolling bearing of this invention. It is sectional drawing which shows the other example of the rolling bearing of this invention. It is a schematic cross section which shows the structure of a hard film. It is a schematic diagram which shows the film-forming principle of UBMS method. It is a schematic diagram of the UBMS apparatus provided with the AIP function. It is a figure which shows a friction tester. It is a figure which shows a thrust type | mold rolling fatigue testing machine. It is a figure which shows the testing machine used for the bearing life test. 2 is a photograph of a bearing inner ring on which a hard film of Example 1 is formed. 3 is a photograph of a bearing inner ring on which a hard film of Comparative Example 1 is formed. 6 is a photograph of a bearing inner ring on which a hard film of Comparative Example 4 is formed.

  A hard film such as a DLC film has a residual stress in the film, and the residual stress varies greatly depending on the film structure, film forming conditions, and substrate shape. As a result of repeated experiments, it was found that the influence of the substrate shape was unexpectedly large. For example, on a flat surface, a hard film that has no delamination immediately after film formation and has a large critical delamination load in a scratch test may peel off immediately after film formation on a curved surface such as an inner / outer ring raceway surface of a rolling bearing, or immediately after film formation. Even if it does not peel off, it may be easily peeled off during use. As a result of intensive studies, the present inventors have made hard films formed on the inner and outer raceways of the rolling bearings and the rolling surfaces of the rolling elements, which are curved surfaces, a base layer (Cr) and a mixed layer (WC / DLC gradient). ) And the surface layer (DLC), it has been found that the peel resistance can be greatly improved and the hard film can be prevented from peeling even under actual use conditions of the bearing. The present invention has been made based on such findings.

  The rolling bearing of the present invention will be described with reference to FIGS. FIG. 1 is a sectional view of a rolling bearing (deep groove ball bearing) in which a hard film described later is formed on the inner and outer ring raceway surfaces, and FIG. 2 is a rolling bearing (deep groove ball bearing) in which a hard film is formed on the rolling surface of the rolling element. ) Are cross-sectional views respectively. The rolling bearing 1 includes an inner ring 2 having an inner ring raceway surface 2a on the outer periphery, an outer ring 3 having an outer ring raceway surface 3a on the inner periphery, and a plurality of rolling elements that roll between the inner ring raceway surface 2a and the outer ring raceway surface 3a. 4. The rolling elements 4 are held at regular intervals by a cage 5. The opening portions in the axial direction of the inner and outer rings are sealed by the seal member 6, and grease 7 is sealed in the bearing space. As the grease 7, a known grease for a rolling bearing can be used.

  In the rolling bearing of FIG. 1 (a), a hard film 8 is formed on the outer peripheral surface (including the inner ring raceway surface 2a) of the inner ring 2, and in the rolling bearing of FIG. 1 (b), the inner peripheral surface ( A hard film 8 is formed on the outer ring raceway surface 3a). When the hard film 8 is formed on the inner / outer rings, it may be formed at least on the raceway surface. Therefore, it may be formed on the entire outer peripheral surface of the inner ring, the entire outer peripheral surface of the outer ring as shown in each drawing, or may be formed on the entire inner / outer ring.

  In the rolling bearing shown in FIG. 2, a hard film 8 is formed on the rolling surface of the rolling element 4. Since the rolling bearing of FIG. 2 is a deep groove ball bearing, the rolling element 4 is a ball, and its rolling surface is the entire spherical surface. When a cylindrical roller bearing or a tapered roller bearing is used as a rolling bearing other than that shown in the figure, when the hard film 8 is formed on the rolling element, it is formed at least on the rolling surface (such as the outer circumference of the cylinder). I just need it.

  As shown in FIGS. 1 and 2, the inner ring raceway surface 2 a of the deep groove ball bearing is a circular curved surface having an arc-shaped cross section in the axial direction in order to guide the balls as the rolling elements 4. Similarly, the outer ring raceway surface 3a is also a circular curved surface having an arc-shaped cross section in the axial direction. The radius of curvature of the arc groove is generally about 0.51 to 0.54 dw when the steel ball diameter is dw. In the case of using a cylindrical roller bearing or a tapered roller bearing as a rolling bearing other than the mode shown in the figure, the inner ring raceway surface and the outer ring raceway surface are curved at least in the circumferential direction in order to guide the rollers of these bearings. It becomes. In addition, in the case of a self-aligning roller bearing or the like, since a cylindrical roller is used as a rolling element, the inner ring raceway surface and the outer ring raceway surface are curved in the axial direction in addition to the circumferential direction. In the rolling bearing of the present invention, the inner ring raceway surface and the outer ring raceway surface may have any of the above shapes.

  In the rolling bearing 1 of the present invention, the inner ring 2, the outer ring 3, and the rolling element 4, which are bearing members for which the hard film 8 is formed, are made of an iron-based material. As the iron-based material, any steel material generally used as a bearing member can be used, and examples thereof include high carbon chromium bearing steel, carbon steel, tool steel, martensitic stainless steel, and the like.

  In these bearing members, it is preferable that the surface on which the hard film is formed has a Vickers hardness of Hv650 or more. By setting it as Hv650 or more, a hardness difference with a hard film | membrane (underlayer) can be decreased and adhesiveness can be improved.

  On the surface on which the hard film is formed, it is preferable that a nitride layer is formed by nitriding before forming the hard film. As the nitriding treatment, it is preferable to perform a plasma nitriding treatment in which an oxide layer that hinders adhesion is hardly generated on the surface of the substrate. Further, the surface hardness after nitriding is preferably Vickers hardness of Hv1000 or more in order to further improve the adhesion to the hard film (underlayer).

  The surface roughness Ra of the surface on which the hard film is formed is preferably 0.05 μm or less. When the surface roughness Ra exceeds 0.05 μm, it is difficult to form a hard film at the tip of the projection having the roughness, and the film thickness is locally reduced.

  The structure of the hard film in the present invention will be described with reference to FIG. FIG. 3 is a schematic cross-sectional view showing the structure of the hard film 8 in the case of FIG. As shown in FIG. 3, the hard film 8 includes (1) an underlayer 8a mainly composed of Cr directly formed on the inner ring raceway surface 2a of the inner ring 2, and (2) an underlayer 8a. It has a three-layer structure including a mixed layer 8b mainly composed of WC and DLC and (3) a surface layer 8c mainly composed of DLC formed on the mixed layer 8b. Here, in the mixed layer 8b, the content of WC in the mixed layer decreases continuously or stepwise from the base layer 8a side to the surface layer 8c side, and the DLC content in the mixed layer This is a layer with a higher rate.

  Since the base layer 8a is a layer mainly composed of Cr, it has good compatibility with a bearing member made of an iron-based material as a base material, and adheres more closely to the base material than when W, Ti, Si, or the like is used. Excellent in properties. In particular, it has excellent adhesion to high carbon chromium bearing steel used as a bearing race material.

  The WC used for the mixed layer 8b has intermediate hardness and elastic modulus between Cr and DLC, and concentration of residual stress after film formation hardly occurs. As shown in Comparative Example 5 to be described later, when the mixed layer is a layer mainly composed of Cr and DLC in accordance with the underlayer, sufficient adhesion cannot be obtained when the bearing is used. Thus, in the case where a hard film containing DLC having excellent peeling resistance is to be formed on the inner and outer ring raceway surfaces of the rolling bearing that is a curved surface and the rolling surface of the rolling element, the intermediate layer (mixed layer 8b) Material selection is also an important factor.

  In addition, since the mixed layer 8b has a gradient composition in which the content of WC is small toward the surface layer 8c side and the content of DLC is high, adhesion between both the base layer 8a and the surface layer 8c is improved. Excellent. In particular, in the mixed layer, WC and DLC are physically bonded, and the DLC content is increased on the surface layer 8c side, so that the adhesion between the surface layer 8c and the mixed layer 8b is excellent.

The surface layer 8c is a film mainly composed of DLC. The surface layer 8c preferably has an inclined layer portion 8d whose hardness increases continuously or stepwise from the mixed layer 8b side on the side adjacent to the mixed layer 8b. This is a portion obtained by changing (raising) the bias voltage continuously or stepwise in order to avoid a sudden change in the bias voltage when the bias voltage is different between the mixed layer 8b and the surface layer 8c. The inclined layer portion 8d changes the bias voltage as described above, and as a result, the hardness is inclined as described above. The reason why the hardness increases continuously or stepwise is that the composition ratio between the graphite structure (sp ² ) and the diamond structure (sp ³ ) in the DLC structure is biased toward the latter as the bias voltage increases. Thereby, there is no sudden hardness difference between the mixed layer and the surface layer, and the adhesion between the mixed layer 8b and the surface layer 8c is further improved.

  The thickness of the hard film 8 (total of the three layers) is preferably 0.5 to 3.0 μm. If the film thickness is less than 0.5 μm, the abrasion resistance and mechanical strength may be inferior, and if it exceeds 3.0 μm, the film is easily peeled off. Furthermore, the ratio of the thickness of the surface layer 8c to the thickness of the hard film 8 is preferably 0.8 or less. If this ratio exceeds 0.8, the gradient structure for physical bonding of WC and DLC in the mixed layer 8b becomes a discontinuous structure, so that the adhesiveness is likely to deteriorate.

  By making the hard film 8 into a three-layer structure of the base layer 8a, the mixed layer 8b, and the surface layer 8c having the above composition, the peel resistance is excellent.

The physical properties of the hard film 8 are SUJ2 hardened steel having a surface roughness Ra of 0.01 μm or less and a Vickers hardness Hv of 780, and a contact with a load of 0.5 GPa maximum contact surface pressure of Hertz. The specific wear amount of the hard film is preferably less than 200 × 10 ⁻¹⁰ mm ³ / (N · m) when the counterpart material is rotated for 30 minutes at a rotational speed of 0.05 m / s. The form of this friction and wear test is an adhesive wear form close to the wear form in the bearing because the surface roughness of the counterpart material is small, and the specific wear amount is 200 × 10 ⁻¹⁰ mm ³ / (N · m) in the test. If it is less than (), it is effective in reducing wear even for local slip occurring on the raceway surface.

  Moreover, it is preferable that the sum total of the average value of indentation hardness and a standard deviation value is 25-45 GPa. Within this range, a high effect is exhibited even in the abrasive wear that occurs when a hard foreign object intervenes in the raceway surface.

  Moreover, it is preferable that the critical peeling load in a scratch test is 50 N or more. The method for measuring the critical peel load in the scratch test is as shown in the examples described later. When the critical peel load is less than 50 N, the hard film is likely to peel when the bearing is used under high load conditions. Even if the critical peeling load is 50 N or more, the film may be easily peeled off depending on the case unless it is a film structure as in the present invention.

  In the rolling bearing of the present invention, by forming a hard film having the structure and physical properties as described above, even when subjected to a load such as rolling contact during use of the bearing, the film can be prevented from being worn or peeled off and severely lubricated. Even in the state, damage to the raceway surface is small and the service life is long. In addition, in rolling bearings filled with grease, if the new metal surface is exposed due to damage to the race or the like, grease degradation is promoted by catalytic action. However, in the rolling bearing of the present invention, the raceway surface and rolling due to metal contact are caused by a hard film. Since surface damage can be prevented, this grease deterioration can also be prevented.

  Hereinafter, a method for forming the hard film will be described. The hard film is obtained by forming the base layer 8a, the mixed layer 8b, and the surface layer 8c in this order on the film formation surface of the bearing member.

  The underlayer 8a and the mixed layer 8b are preferably formed using a UBMS apparatus using Ar gas as a sputtering gas. The film forming principle of the UBMS method using the UBMS apparatus will be described with reference to the schematic diagram shown in FIG. In the drawing, the substrate 12 is an inner ring, an outer ring, or a rolling element that is a bearing member to be deposited, but is schematically shown as a flat plate. As shown in FIG. 4, an inner magnet 14 a and an outer magnet 14 b having different magnetic properties are arranged in the central portion and the peripheral portion of the round target 15, and the magnet 14 a is formed while forming a high-density plasma 19 near the target 15. , 14 b, a part 16 a of the magnetic force lines 16 reaches the vicinity of the base material 12 connected to the bias power source 11. The Ar plasma generated during the sputtering along the magnetic force lines 16a can be diffused to the vicinity of the base material 12. In such a UBMS method, an ion assist effect that causes Ar ions 17 and electrons to reach the base material 12 in a larger amount than the ordinary sputtering along the magnetic field lines 16a reaching the vicinity of the base material 12 due to the ion assist effect. A dense film (layer) 13 can be formed.

  As the target 15, a Cr target is used when forming the base layer 8a, and a WC target and a graphite target are used together when forming the mixed layer 8b. The target used for each layer is sequentially replaced every time the layers are formed.

  The mixed layer 8b is formed in a continuous or stepwise manner while increasing the sputtering power applied to the graphite target serving as the carbon supply source and decreasing the power applied to the WC target. Thereby, it can be set as the layer of the gradient composition which the content rate of WC becomes small toward the surface layer 8c side, and the content rate of DLC becomes high.

  The formation of the surface layer 8c is also preferably performed using a UBMS apparatus using Ar gas as the sputtering gas. More specifically, the surface layer 8c uses this apparatus, uses a graphite target and a hydrocarbon gas in combination as a carbon supply source, and the hydrocarbon system with respect to the introduction amount 100 of the Ar gas into the apparatus. Under the conditions where the ratio of the amount of gas introduced is 1 to 5, the degree of vacuum in the apparatus is 0.2 to 0.8 Pa, and the bias voltage applied to the bearing member as the base material is 70 to 150 V, The carbon atoms generated from the carbon supply source are preferably deposited on the mixed layer 8b. This preferable condition will be described below.

  Adhesiveness with the mixed layer 8b can be improved by using a graphite target and a hydrocarbon-based gas in combination as a carbon supply source. As the hydrocarbon-based gas, methane gas, acetylene gas, benzene and the like can be used, and are not particularly limited. However, methane gas is preferable from the viewpoint of cost and handleability.

  By setting the ratio of the introduction amount of the hydrocarbon-based gas to 1 to 5 (volume part) with respect to 100 introduction (volume part) of Ar gas into the UBMS apparatus (in the film formation chamber), the surface layer The adhesion with the mixed layer 8b can be improved without deteriorating the wear resistance of 8c.

  The degree of vacuum in the UBMS apparatus (inside the film forming chamber) is preferably 0.2 to 0.8 Pa as described above. More preferably, it is 0.25 to 0.8 Pa. If the degree of vacuum is less than 0.2 Pa, the amount of Ar gas in the chamber is small, so that Ar plasma is not generated and film formation may not be possible. On the other hand, if the degree of vacuum is higher than 0.8 Pa, the reverse sputtering phenomenon tends to occur and the wear resistance may be deteriorated.

  The bias voltage applied to the bearing member as the base material is preferably 70 to 150 V as described above. More preferably, it is 100-150V. When the bias voltage is less than 70V, densification does not proceed and the wear resistance is extremely deteriorated, which is not preferable. On the other hand, when the bias voltage exceeds 150 V, reverse sputtering tends to occur, and the wear resistance may be deteriorated. On the other hand, if the bias voltage is too high, the surface layer becomes too hard and may be easily peeled off when the bearing is used.

  Moreover, it is preferable that the introduction amount of Ar gas which is sputtering gas is 40-150 ml / min. More preferably, it is 50-150 ml / min. When the Ar gas flow rate is less than 40 ml / min, Ar plasma is not generated and film formation may not be possible. On the other hand, if the Ar gas flow rate is higher than 150 ml / min, the reverse sputtering phenomenon tends to occur, so that the wear resistance may be deteriorated. When the amount of Ar gas introduced is large, the collision probability between Ar atoms and carbon atoms increases in the film forming chamber. As a result, the number of Ar atoms reaching the film surface is reduced, the effect of compacting the film by Ar atoms is reduced, and the wear resistance of the film is deteriorated.

  As described above, the inclined layer portion 8d of the surface layer 8c is obtained by forming the film while continuously or stepwise increasing the bias voltage applied to the bearing member that is the base material.

  As a hard film formed on the rolling bearing of the present invention, a hard film was formed on a predetermined base material, and the physical properties of the hard film were evaluated. A similar hard film was actually formed on the inner ring raceway surface and the outer ring raceway surface of the rolling bearing, and the bearing was evaluated. These will be described below as examples, comparative examples, and reference examples.

The formation conditions of the base material, UBMS apparatus, sputtering gas, underlayer and mixed layer used for evaluation of the hard film are as follows.
(1) Base material: Base material shown in each table (2) Base material dimension: Mirror surface (about Ra 0.005 μm) disc (φ48 mm × φ8 mm × 7 mm)
(3) UBMS device: manufactured by Kobe Steel; UBMS202 / AIP composite device (4) Sputtering gas: Ar gas (5) Formation conditions of underlayer and mixed layer Underlayer: about 5 × 10 ⁻³ Pa in the film formation chamber The substrate was baked with a heater, the substrate was baked with a heater, the substrate surface was etched with Ar plasma, and a Cr layer was formed using a Cr target by the UBMS method. In addition, when using it as base layers other than Cr, it formed on the same conditions except using a corresponding target.
Mixed layer: The inside of the film forming chamber is evacuated to about 5 × 10 ⁻³ Pa, the substrate is baked with a heater, the substrate surface (or the Cr layer surface) is etched with Ar plasma, and then the WC target and The sputtering power applied to the graphite target was adjusted to incline the composition ratio of WC and DLC. In addition, when it was set as the mixed layer other than WC, it formed on the same conditions except using a corresponding target.
(6) The conditions for forming the surface layer are shown in each table.

  An outline of the UBMS 202 / AIP combined apparatus is shown in FIG. FIG. 5 is a schematic diagram of a UBMS apparatus having an arc ion plating (hereinafter referred to as AIP) function. As shown in FIG. 5, the UBMS 202 / AIP composite apparatus instantaneously vaporizes and ionizes the AIP evaporation source material 21 to the base material 23 arranged on the disk 22 using vacuum arc discharge, This is deposited on the base material 23 to increase the plasma density in the vicinity of the base material 23 and increase the ion assist effect by the non-equilibrium magnetic field of the sputtering evaporation source material (target) 24. (See FIG. 4), the apparatus has a UBMS function capable of controlling the characteristics of the film deposited on the substrate. By this apparatus, a composite film in which an AIP film and a plurality of UBMS films (including a composition gradient) are arbitrarily combined can be formed on a substrate. In this embodiment, a base layer, a mixed layer, and a surface layer are formed as a UBMS film on a bearing member (inner ring, outer ring) as a base material. Although the outer ring raceway surface is located on the inner circumference of the outer ring, the film is formed by the ionized target turning around.

Example 1 to Example 8, Example 10, Comparative Example 1 to Comparative Example 5, Reference Example 1 to Reference Example 8
The substrates shown in Tables 1 to 3 were ultrasonically cleaned with acetone and then dried. After drying, the substrate was attached to a UBMS / AIP composite apparatus, and an underlayer and a mixed layer of the materials shown in each table were formed under the above-described formation conditions. On top of that, a DLC film as a surface layer was formed under the film forming conditions shown in each table to obtain a test piece having a hard film. Note that “degree of vacuum” in each table is the degree of vacuum in the film forming chamber in the above apparatus. The obtained test piece was subjected to the following wear test, hardness test, film thickness test, scratch test, and thrust type rolling fatigue test. The results are shown in each table.

Example 9
Manufactured by JEOL Ltd .: A substrate (Vickers hardness Hv1000) subjected to plasma nitrogen treatment using a radical nitriding apparatus was ultrasonically cleaned with acetone and then dried. After drying, the base material was attached to a UBMS / AIP composite apparatus, and an underlayer (Cr) and a mixed layer (WC / DLC) having the materials shown in Table 1 were formed under the above-described formation conditions. A DLC film, which is a surface layer, was formed on the film formation conditions shown in Table 1 to obtain a test piece having a hard film. About the obtained test piece, it uses for the test similar to Example 1, and the result is written together in Table 1. FIG.

<Friction test>
The obtained test piece was subjected to a friction test using a friction tester shown in FIG. 6A shows a front view, and FIG. 6B shows a side view. SUJ2 hardened steel having a surface roughness Ra of 0.01 μm or less and a Vickers hardness Hv of 780 is attached to the rotating shaft as a mating member 32, the test piece 31 is fixed to the arm portion 33, and a predetermined load 34 is applied to the upper side of the drawing And a lubricant is interposed between the test piece 31 and the mating member 32 for 30 minutes at a rotation speed of 0.05 m / s under a maximum contact surface pressure of 0.5 GPa at room temperature (25 ° C.). Instead, the load cell 35 detected the frictional force generated between the counterpart material 32 and the test piece 31 when the counterpart material 32 was rotated. From this, the specific wear amount was calculated.

<Hardness test>
The indentation hardness of the obtained test piece was measured using a nanoindenter (G200) manufactured by Agilent Technologies. In addition, the measured value has shown the average value of the depth (location where hardness is stabilized) which is not influenced by surface roughness, and is measuring 10 each test piece.

<Film thickness test>
The film thickness of the hard film of the obtained test piece was measured using a surface shape / surface roughness measuring instrument (Taylor Hobson Co., Ltd .: Foam Talisurf PGI830). The film thickness was obtained by masking a part of the film forming portion and determining the level difference between the non-film forming portion and the film forming portion.

<Scratch test>
About the obtained test piece, the scratch test was done using the nanotech company make: level test RST, and the critical peeling load was measured. Specifically, the obtained test piece was tested with a diamond indenter with a tip radius of 200 μm at a scratch speed of 10 mm / min and a load load speed of 10 N / mm (continuously increasing the load), and judged on the testing machine screen. Then, the load at which the area of the exposed base material reached 50% with respect to the frictional trace on the screen (length in the friction direction 375 μm, width about 100 μm) was measured as the critical peel load.

<Thrust type rolling fatigue test>
About the obtained test piece, using the testing machine shown in FIG. 7, as a thrust type rolling fatigue test, a case where the lubrication state of the bearing is assumed to be “low lambda condition” and a case where the lubrication state is good Two conditions, the assumed “high lambda condition”, were tested to evaluate the rolling fatigue characteristics of the hard film. Since “low lambda condition” is boundary lubrication, damage due to contact is affected in addition to pure repeated rolling fatigue. Therefore, the wear resistance and adhesion of the hard film are required. Each condition is shown below.

[Low lambda condition]
Lubricating oil: VG2
Lambda: 0.6
Maximum contact surface pressure: 2 GPa
Rotational speed: 1000r / min
Orbit diameter: φ20mm
Rolling element: size 7/32 ", number 3, material SUJ2, hardness Hv750, surface roughness 0.005μmRa
Oil temperature: 70 ° C
Censoring time: None (1111h at 8th load)

[High lambda condition]
Lubricating oil: VG32
Lambda: 9.5
Maximum contact surface pressure: 3GPa
Rotation speed: 4500r / min
Orbit diameter: φ20mm
Rolling element: size 7/32 ", number 3, material SUJ2, hardness Hv750, surface roughness 0.005μmRa
Oil temperature: 70 ° C
Abort time: 300h
(The load count is 8th power at 247h)

  As shown in FIG. 7, the testing machine has a configuration in which the rolling element 42 rolls between a disk-shaped test piece 41 and a bearing disc 45, and the test piece 41 is supported via an alignment ball 43. Has been. In the figure, 44 is a rotary ball spline for preloading, 46 is a heater, and 47 is a thermocouple. This testing machine has a structure in which the rolling trace does not shift even when the test piece 41 is reattached. In the evaluation method, the test piece is removed every 20 h of test time, and the presence or absence of peeling of the hard film from the test piece is confirmed by observation with an optical microscope. For example, if it peels at the time of 20h confirmation, a lifetime will be 20h. If it is not peeled off at the time of 20h confirmation, the test piece is attached again and the test is continued. The lifetime is shown in Table 1 and Table 2 together. Also, as a life judgment, under low lambda conditions, a life of 1500 h or more is recorded as “◯”, a life of 1000 h or more and less than 1500 h is recorded as “Δ”, and a life of less than 1000 h is recorded as “x”. Under the high lambda condition, “O” is recorded when the lifetime is 300 h or more, and “X” is recorded when the lifetime is less than 300 h.

<Film formation test on bearing inner and outer rings>
Under the conditions of Example, Comparative Example, and Reference Example, film formation was actually performed on the following inner ring raceway surface and outer ring raceway surface of 6206 rolling bearings (deep groove ball bearings). Peeling was confirmed. Those that were not peeled when removed from the film forming chamber were recorded as “◯”, and those that were peeled off were recorded as “X”, and the results are shown in each table. Moreover, the photograph after the test of Example 1 is shown in FIG. 9, the photograph after the test of Comparative Example 1 is shown in FIG. 10, and the photograph after the test of Comparative Example 4 is shown in FIG.
Inner ring: Hard film is formed on the raceway surface, material SUJ2, hardness Hv750, surface roughness 0.03μmRa
Outer ring: Hard film is formed on the raceway surface, material SUJ2, hardness Hv750, surface roughness 0.03μmRa

<Bearing life test>
A test 6206 rolling bearing (deep groove ball bearing) was assembled using the inner and outer rings of Examples 1 to 10 and Comparative Example 5 in which a hard film was formed in the above film formation test, and this test bearing was used for illustration. A life test was conducted from 8 testing machines. As shown in FIG. 8, the testing machine rotatably supports a shaft 55 that is rotated by a drive pulley 54 with a pair of test bearings 51 while being loaded with a load from a load coil spring 53 via a load ball bearing 52. Is. The lubrication state is assumed to be good. Test conditions are shown below.

Inner ring / outer ring: Inner ring and outer ring on which a hard film was formed in the above film formation test Rolling elements: Size 3/8 ", number 9, material SUJ2, hardness Hv750, surface roughness 0.005 μmRa
Lubricating oil: VG56
Lambda: 3 or more Maximum contact surface pressure: 3.3 GPa
Rotation speed: 3000r / min (inner ring rotation)
Calculated life: L ₁₀ life 127h
Abort time: 200h

  Tests were conducted for a test time of 20 h and a test time of 200 h, and the presence or absence of peeling of the hard film from the member was confirmed on the raceway surface after the test using an optical microscope. For example, if it peels after the 20h test, the life becomes 20h, and if it peels after the 200h test, the life becomes 200h. Therefore, the life level is three levels of 20h, 200h, 200h or more. The lifetime is shown in Table 1 and Table 2 together. Further, as the life judgment, those having a life of 200 h or more are recorded as “◯”, those having less than 200 h are recorded as “x”, and the results are shown in Tables 1 and 2.

  As shown in Table 1, the hard film of each example was excellent in wear resistance and adhesion, and was able to prevent peeling of the hard film even when a bearing was used.

  In each example having a predetermined film structure, the film formation state on the inner and outer ring raceway surfaces is good, whereas in Comparative Examples 1 to 4 in which the underlayer and the intermediate layer are different from the present invention, film formation is difficult. there were. For example, in Example 1 (FIG. 9), the hard film was well formed, but in Comparative Example 1 (FIG. 10) in which the underlayer was not provided, the film was largely peeled off and the underlayer was provided, but not Cr Peeling was also observed in Comparative Example 4 (FIG. 11) using Ti. In Comparative Example 5, the film itself was formed, but it was easy to peel off when using the bearing.

  The rolling bearing of the present invention has excellent peeling resistance of hard films containing DLC formed on the inner and outer ring raceway surfaces and the rolling surfaces of the rolling elements, and can exhibit the characteristics of the DLC main body. Excellent in corrosion resistance and corrosion resistance. For this reason, the rolling bearing of this invention is applicable to various uses including the use in a severe lubrication state.

1 Rolling bearing (deep groove ball bearing)
2 Inner ring 3 Outer ring 4 Rolling element 5 Cage 6 Seal member 7 Grease 8 Hard film 11 Bias power supply 12 Base material 13 Film (layer)
DESCRIPTION OF SYMBOLS 15 Target 16 Magnetic field line 17 Ar ion 18 Ionized target 19 High density plasma 21 AIP evaporation source material 22 Disc 23 Base material 24 Sputter evaporation source material (target)
31 Test piece 32 Counter member 33 Arm part 34 Load 35 Load cell 41 Test piece 42 Rolling body 43 Alignment ball 44 Rotary ball spline 45 Bearing disc 46 Heater 47 Thermocouple 51 Test bearing 52 Load ball bearing 53 Load coil spring 54 Drive pulley 55 axes

Claims (18)

An inner ring having an inner ring raceway surface on the outer periphery; an outer ring having an outer ring raceway surface on the inner periphery; and a plurality of rolling elements that roll between the inner ring raceway surface and the outer ring raceway surface. And the rolling elements are rolling bearings made of an iron-based material,
The inner ring raceway surface and the outer ring raceway surface are curved surfaces that guide the rolling elements, and a hard film is formed on at least one surface selected from the inner ring raceway surface, the outer ring raceway surface, and the rolling surface of the rolling element. It was filmed,
The hard film is a base layer mainly composed of chromium directly formed on the surface, a mixed layer mainly composed of tungsten carbide and diamond-like carbon formed on the base layer, A film having a structure comprising a surface layer mainly composed of diamond-like carbon formed on the mixed layer;
In the mixed layer, the content of the tungsten carbide in the mixed layer decreases continuously or stepwise from the base layer side to the surface layer side, and the diamond-like carbon in the mixed layer decreases. A rolling bearing characterized by being a layer having a high content rate.   The rolling bearing according to claim 1, wherein the rolling element is a ball, and the inner ring raceway surface and the outer ring raceway surface are circular curved surfaces that guide the rolling element.   The rolling bearing according to claim 1, wherein the surface layer has an inclined layer portion whose hardness increases continuously or stepwise from the mixed layer side on a side adjacent to the mixed layer. . The surface layer is a layer formed using an unbalanced magnetron sputtering apparatus using argon gas as a sputtering gas,
A graphite target and a hydrocarbon gas are used in combination as a carbon supply source, and the ratio of the introduction amount of the hydrocarbon gas to the introduction amount 100 of the argon gas into the device is 1 to 5, Under the condition that the degree of vacuum is 0.2 to 0.8 Pa and the bias voltage applied to the bearing member as the base material is 70 to 150 V, carbon atoms generated from the carbon supply source are deposited on the mixed layer. 4. The rolling bearing according to claim 1, wherein the rolling bearing is formed by forming a film.   The rolling bearing according to claim 4, wherein the hydrocarbon-based gas is methane gas.   The inclined layer portion of the surface layer is formed by increasing a bias voltage applied to a bearing member serving as a base material continuously or stepwise. Item 6. A rolling bearing according to Item 5. The underlayer and the mixed layer are layers formed using an unbalanced magnetron sputtering apparatus using argon gas as a sputtering gas,
The mixed layer is formed in a continuous or stepwise manner while increasing the sputtering power applied to the graphite target serving as the carbon supply source and decreasing the power applied to the tungsten carbide target. The rolling bearing according to any one of claims 1 to 6, wherein the rolling bearing is characterized. The hard film is brought into contact with SUJ2 hardened steel having a surface roughness Ra of 0.01 μm or less and a Vickers hardness Hv of 780 by applying a load with a maximum contact surface pressure of 0.5 GPa of Hertz. The specific wear amount of the hard film when the counterpart material is rotated for 30 minutes at a rotational speed of 05 m / s is less than 200 × 10 ⁻¹⁰ mm ³ / (N · m). The rolling bearing according to any one of claims 1 to 7.   The rolling bearing according to claim 8, wherein the hard film has a total indentation hardness average value and standard deviation value of 25 to 45 GPa.   The rolling bearing according to claim 8 or 9, wherein the hard film has a critical peel load in a scratch test of 50 N or more.   The film thickness of the hard film is 0.5 to 3 µm, and the ratio of the thickness of the surface layer to the film thickness of the hard film is 0.8 or less. The rolling bearing according to claim 10.   The rolling bearing according to any one of claims 1 to 11, wherein the ferrous material is selected from high carbon chromium bearing steel, carbon steel, tool steel, and martensitic stainless steel.   The rolling bearing according to claim 12, wherein the surface on which the hard film is formed has a Vickers hardness of Hv650 or higher.   The rolling bearing according to any one of claims 1 to 13, wherein a nitride layer is formed by nitriding treatment on the surface on which the hard film is formed before the hard film is formed.   The rolling bearing according to claim 14, wherein the nitriding treatment is a plasma nitriding treatment.   The rolling bearing according to claim 14 or 15, wherein a hardness of the surface after the nitriding treatment is Hv1000 or more in terms of Vickers hardness.   The rolling bearing according to any one of claims 1 to 16, wherein a surface roughness Ra of the surface on which the hard film is formed is 0.05 µm or less.   The rolling bearing according to claim 1, wherein the rolling bearing is filled with grease.