JP5993680B2 - Rolling bearing and manufacturing method thereof - 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, a rolling element surface, and a cage sliding contact 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, attempts have been made to form a DLC film on the raceway surface of a bearing ring of a rolling bearing, the rolling surface of a rolling element, a cage sliding contact surface, and the like. 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 forming a DLC film on each said surface in a rolling bearing, it is necessary to improve adhesiveness.

  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). Similarly, an intermediate layer is provided to improve adhesion, and a plurality of layers are formed on the surface of the cage of the rolling bearing, and a predetermined layer is formed between the layer of the outermost layer and the cage. A cage with an intermediate layer of hardness has been proposed (see Patent Document 2).

  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 3).

  In addition, a hardened layer having undergone a predetermined treatment was formed on the surface of the cage base material, a hard film having a higher hardness was coated on the surface of the hardened layer, and a soft film having a solid lubricating effect was coated on the hard film surface. A cage, a manufacturing method thereof, and the like have been proposed (see Patent Document 4 and Patent Document 5).

Japanese Patent No. 4178826 JP 2006-3000294 A Patent No. 3961739 Japanese Patent Laying-Open No. 2005-147306 JP 2005-147244 A

  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. The slidable contact surface of the cage is a surface that contacts the rolling element (a cage pocket surface) or a surface that contacts the raceway, and the shape thereof is a curved surface. When a DLC film is formed on the surface having the above-described shape, 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, impact force, or a thermal shock due to local sliding heat generation when the bearing is used.

  When the DLC film is peeled off, the original excellent characteristics of the DLC film cannot be exhibited. Further, metal contact occurs between the bearing members, and wear of the members causes wear powder to intervene on the rolling surface, leading to raceway surface damage and the like. In the case of grease lubrication, grease degradation may be promoted by the catalytic action of the new metal surface.

  The technology of each of the above-mentioned patent documents is intended to prevent peeling of the hard film, 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 There is room for further improvement. In particular, in order to improve the peel resistance over a long period on the raceway surface of a rolling bearing subject to high contact stress and the cage sliding surface subject to strong impact force, not only static adhesion and mechanical properties, Fatigue properties are also important, and it is desirable to improve the film structure based on this.

  The present invention has been made to cope with such problems, and improves the peel resistance of the DLC film formed on the inner / outer ring raceway surface and the cage sliding surface of the rolling bearing. It is an object of the present invention to provide a rolling bearing that exhibits excellent seizure resistance, wear resistance, and corrosion resistance, and that can prevent damage due to metal contact between bearing members.

  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, a plurality of rolling elements that roll between the inner ring raceway surface and the outer ring raceway surface, A rolling bearing comprising a cage for holding the rolling element, wherein at least one bearing member selected from the inner ring, the outer ring, the rolling element, and the cage is made of an iron-based material, and the iron A hard film on at least one surface selected from the inner ring raceway surface, the outer ring raceway surface, the rolling surface of the rolling element, and the sliding contact surface of the cage, which is a surface of the bearing member made of a base material The hard film is formed of a first mixed layer mainly composed of Cr and tungsten carbide (hereinafter referred to as WC) directly formed on the surface, and the first mixed layer. Second, mainly composed of WC and DLC deposited on the substrate A film having a structure composed of a composite layer and a surface layer mainly composed of DLC formed on the second mixed layer, wherein the first mixed layer is from the surface side to the second mixed layer side. Continuously or stepwise, the Cr content in the first mixed layer decreases, the WC content in the first mixed layer increases, and the second mixed layer is The content ratio of the WC in the second mixed layer decreases continuously or stepwise from the first mixed layer side to the surface layer side, and the DLC content in the second mixed layer The hydrogen content in the second mixed layer is 10 to 45 atomic%.

  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 element is a ball, and the sliding contact surface of the cage is a pocket surface that holds the ball that is a sliding contact surface with the rolling element.

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 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 second mixed layer under a condition in which a bias voltage applied to the bearing member is 70 to 150 V.

  Note that the bias potential with respect to the base material is applied so as to be negative with respect to the ground potential. For example, the bias voltage of 150 V means that the bias potential of the base material is −150 V with respect to the ground potential. Show.

  The surface layer has a relaxation layer portion adjacent to the second mixed layer, and the relaxation layer portion includes the ratio of the introduction amount of the hydrocarbon-based gas, the degree of vacuum in the device, and the bias voltage. It is a part formed by changing at least one of these continuously or stepwise.

  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 0.7 or less.

  The iron-based materials forming the inner ring, the outer ring, and the rolling element are high carbon chromium bearing steel, carbon steel, tool steel, or martensitic stainless steel, respectively. In the inner ring, the outer ring, or the rolling element, the surface on which the hard film is formed has a Vickers hardness of Hv650 or more.

  The iron-based material forming the cage is a cold rolled steel plate, carbon steel, chromium steel, chromium molybdenum steel, nickel chromium molybdenum steel, or austenitic stainless steel.

  In the surface on which the hard film is formed, a nitride layer is formed by nitriding before the hard film is formed.

  In the inner ring, the outer ring, or the rolling element, a surface roughness Ra of a surface on which the hard film is formed is 0.05 μm or less. Further, in the above cage, the surface roughness Ra of the sliding contact surface on which the hard film is formed is 0.5 μm or less.

  The rolling bearing is characterized in that grease is enclosed.

  The rolling bearing of the present invention is formed by forming a hard film having a predetermined film structure including DLC on the surface of a bearing member made of an iron-based material. Since the first mixed layer directly formed on each surface contains Cr, the first mixed layer has good compatibility with the iron-based material, and has better adhesion than W or Si. In addition, since WC has intermediate hardness and elastic modulus between Cr and DLC, concentration of residual stress after film formation can be achieved by using a gradient composition including WC in both the first mixed layer and the second mixed layer. Is unlikely to occur. Further, since the first mixed layer and the second mixed layer have a gradient composition, they have a structure in which different materials are physically combined. Further, since the hydrogen content in the second mixed layer of the hard film is 10 to 45 atomic%, the raceway surface and rolling surface that receive high contact stress, and the cage sliding surface that receives strong impact force can be used for a long time. Separation can be prevented.

  With the above structure, the hard film has excellent peeling resistance and can exhibit the original characteristics of DLC while being formed on the curved inner and outer ring raceway surfaces, the rolling surface of the rolling element, and the non-planar cage sliding surface. 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 and the cage sliding surface even under severe lubrication.

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 sectional drawing which shows the other example of the rolling bearing of this invention. It is an enlarged view of the holder | retainer of FIG. 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. It is a figure which shows a fine abrasion tester. It is a figure which shows the testing machine used for the bearing life test. It is a figure which shows an example of a GDS analysis result. It is an enlarged view of the 2nd mixed layer (WC / DLC layer) part in FIG. It is a figure which shows the relationship (calibration curve) of the hydrogen amount output value in GDS analysis, and the hydrogen amount measured by ERDA analysis.

  In the rolling bearing of the present invention, at least one bearing member selected from an inner ring, an outer ring, a rolling element, and a cage is made of an iron-based material. The place where the hard film is formed is (1) the surface of the bearing member made of an iron-based material, among which (2) the inner ring raceway surface, the outer ring raceway surface, the rolling surface of the rolling element, and the cage It is at least one surface selected from the sliding surface. These surfaces are mainly non-planar curved surfaces. The hard film is preferably formed on a surface where members made of an iron-based material come into contact with each other.

  The rolling bearing of this invention is demonstrated based on FIGS. Fig. 1 is a cross-sectional view of a rolling bearing (deep groove ball bearing) with a hard film formed on the inner and outer ring raceway surfaces, and Fig. 2 is a rolling bearing (deep groove ball bearing) with a hard film formed on the rolling surface of the rolling element. 3 is a sectional view of a rolling bearing (deep groove ball bearing) having a hard film formed on the pocket surface of the cage, and FIG. 4 is an enlarged view of the cage of FIG.

  As shown in FIG. 1, 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 an inner ring raceway surface 2a and an outer ring raceway surface 3a. A plurality of rolling elements 4 that roll. 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.

  The inner ring 2, the outer ring 3, and the rolling elements 4, which are bearing members that are the targets for forming the hard film 8, are made of an iron-based material. As this 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 the inner ring 2, the outer ring 3, or the rolling element 4, 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.

  In the inner ring 2, the outer ring 3, or the rolling element 4, 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.

  In the rolling bearing of FIG. 3, a hard film 8 is formed on the sliding contact surface of the cage 5. Other bearing configurations are the same as the bearing shown in FIG. As shown in FIG. 4, the cage 5 is a corrugated iron plate cage, which is manufactured by combining two members 5 a and 5 a that are press-molded using an iron-based material described later. A holder pocket 5b for holding is formed. An inner peripheral surface (pocket surface) of the cage pocket 5b is a sliding contact surface with the rolling element 4, and a hard film 8 is formed on the pocket surface. The hard film 8 may be formed on at least one sliding contact surface selected from the sliding contact surface with the raceway ring (inner ring 2 or outer ring 3) and the sliding contact surface with the rolling element 4. In addition to the sliding contact surface of the cage 5, a hard film is also formed on the inner ring raceway surface 2a, the outer ring raceway surface 3a, the rolling surface of the rolling element 4 and the like shown in FIGS. May be.

  The cage 5 that is the target for forming the hard film 8 is made of an iron-based material. As this iron-based material, any material generally used as a cage material can be used, for example, cold rolled steel plate, carbon steel, chromium steel, chromium molybdenum steel, nickel chromium molybdenum steel, austenitic stainless steel, etc. Can be mentioned.

  In the cage 5, the hardness of the slidable contact surface on which the hard film 8 is formed is preferably Vvs hardness of Hv 190 or more, and more preferably Hv 450 or more. By setting it as Hv450 or more, the hardness difference with a hard film | membrane (underlayer) can be reduced as much as possible, and adhesiveness can be improved.

  In the cage 5, the surface roughness Ra of the slidable contact surface on which the hard film 8 is formed is preferably 0.5 μm or less. When the surface roughness Ra exceeds 0.5 μm, the hard film formed on the tip of the projection having the roughness is easily peeled off due to local stress concentration during sliding. Further, since the dirt is not easily removed, the hard film formed on the dirt may be easily peeled off.

  It is preferable that a nitride layer is formed by nitriding treatment on the surface of each member (inner ring, outer ring, rolling element, cage) on which the hard film is formed before the hard film is formed. 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 base material. 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 structure of the hard film in the present invention will be described with reference to FIG. FIG. 5 is a schematic cross-sectional view showing the structure of the hard film 8 in the case of FIG. As shown in FIG. 5, the hard film 8 includes: (1) a first mixed layer 8a mainly composed of Cr and WC formed directly on the inner ring raceway surface 2a of the inner ring 2; From the second mixed layer 8b mainly composed of WC and DLC formed on the mixed layer 8a, and (3) the surface layer 8c mainly composed of DLC formed on the second mixed layer 8b. Having a three-layer structure. In the present invention, the film structure of the hard film is a three-layer structure as described above, so that sudden changes in physical properties (hardness, elastic modulus, etc.) are avoided.

  The first mixed layer 8a is an underlayer formed directly on the raceway surface, the rolling surface, and the sliding contact surface of the cage. Since the first mixed layer 8a contains Cr, the first mixed layer 8a has good compatibility with a bearing member made of an iron-based material serving as a base material, and is excellent in adhesion to the base material as compared with the case where W, Ti, Si or the like is used. In particular, it has excellent adhesion to high carbon chromium bearing steel used as a bearing race material. Further, WC used for the first mixed layer 8a has intermediate hardness and elastic modulus between Cr and DLC, and residual stress concentration after film formation hardly occurs.

  Further, since the first mixed layer 8a has a gradient composition in which the Cr content is small and the WC content is high from the inner ring 2 side toward the second mixed layer 8b side, the inner ring 2 and the second mixture are mixed. Excellent adhesion on both sides with the layer 8b. In addition, Cr and WC are physically bonded in the mixed layer, and damage in the mixed layer can be prevented. Furthermore, since the WC content is increased on the second mixed layer 8b side, the adhesion between the first mixed layer 8a and the second mixed layer 8b is excellent.

  The second mixed layer 8b becomes an intermediate layer interposed between the base layer and the surface layer. As described above, the WC used for the second mixed layer 8b has an intermediate hardness and elastic modulus between Cr and DLC, and residual stress concentration after film formation hardly occurs. Since the second mixed layer 8b has a gradient composition in which the WC content decreases from the first mixed layer 8a side to the surface layer 8c side and the DLC content increases, the first mixed layer 8a and the surface Excellent adhesion on both sides with the layer 8c. In addition, WC and DLC are physically coupled in the mixed layer, and damage in the mixed layer can be prevented. Furthermore, since the DLC content is increased on the surface layer 8c side, the adhesion between the surface layer 8c and the second mixed layer 8b is excellent.

  The second mixed layer 8b is a layer in which non-adhesive DLC is bonded to the first mixed layer 8a side by WC by the anchor effect and is subjected to a strong impact force and causes fatigue, or high surface pressure causes fatigue. In order to develop high adhesion even under such severe conditions, it is considered that the mechanical characteristics and fatigue characteristics of both DLC and WC in this layer are important. Therefore, the present inventors conducted experiments to optimize the film formation conditions of the second mixed layer (WC / DLC), and as a result, the hydrogen content in the second mixed layer was reduced under the general sputtering conditions. It has been found that the peeling life can be remarkably improved in an environment with fatigue due to a strong impact force or in an environment with fatigue due to a high contact stress due to rolling contact, by increasing the number extremely compared to the case where it is performed.

  The hydrogen content in the second mixed layer is 10 to 45 atomic%. It is more preferable to set it as 15-45 atomic%. When the hydrogen content in the second mixed layer is less than 10 atomic%, the mechanical properties are sufficient and the static adhesion is high, but the fatigue properties are inferior, so that they are easily peeled off under rolling contact. On the other hand, when the hydrogen content exceeds 45 atomic%, the mechanical properties become insufficient, and the hard film is greatly deformed without being able to withstand the impact force or the high contact pressure of the rolling contact, and stress is applied to the adjacent layer. Long life is difficult to develop because of the concentration.

  Here, the “hydrogen content in the second mixed layer” in the present invention is the hydrogen content (atomic%) obtained by GDS analysis (glow discharge emission spectroscopic analysis). The GDS analysis is an analysis capable of examining the relationship between the depth direction and the element amount, and can be quantified by preparing a calibration curve for each element. The hydrogen calibration curve was created using ERDA analysis (elastic recoil particle detection method) capable of measuring the absolute amount of hydrogen. Further, calibration curves for constituent elements other than hydrogen were prepared using EDX analysis. Details are shown below.

  FIG. 13 shows an example of the GDS analysis result, and FIG. 14 shows an enlarged view of the second mixed layer (WC / DLC layer) portion in FIG. The sputter time on the horizontal axis represents the depth from the surface. The WC / DLC layer is a range in which the C peak and the W peak coexist, and the maximum value (atomic%) of the hydrogen peak within this coexistence range is defined as “hydrogen content in the second mixed layer” in the present invention. Yes. “Atom%” on the vertical axis is calculated from the hydrogen output value (V) in the GDS analysis by the following method.

  Since the hydrogen output value (V) in GDS analysis differs depending on the test piece material, it is necessary to create a hydrogen calibration curve for each of DLC and WC constituting the second mixed layer (WC / DLC layer). is there. Therefore, for DLC single-layer film test pieces and WC single-layer film test pieces, test pieces having different hydrogen contents were prepared by adjusting the amount of methane gas introduced under conditions matching the film formation conditions of the WC / DLC layer. Analysis and GDS analysis were performed. An example of the relationship (calibration curve) between the hydrogen amount output value (V) in the GDS analysis and the hydrogen amount (atomic%) measured in the ERDA analysis is shown in FIG. It can be seen that the hydrogen output value in the GDS analysis has a linear relationship with the hydrogen content. Since the hydrogen content obtained with the DLC hydrogen calibration curve is different from the hydrogen content obtained with the WC hydrogen calibration curve, it can be arbitrarily determined by taking the average of the hydrogen content obtained with both calibration curves. The hydrogen content (atomic%) corresponding to the hydrogen output value (V) can be calculated.

The surface layer 8c is a film mainly composed of DLC. The surface layer 8c preferably has a relaxing layer portion 8d on the side adjacent to the second mixed layer 8b. This is because when the film formation condition parameters (hydrocarbon gas introduction amount, vacuum degree, bias voltage) are different between the second mixed layer 8b and the surface layer 8c, in order to avoid abrupt changes in these parameters, It is a relaxation layer portion obtained by changing at least one continuously or stepwise. More specifically, the film formation condition parameters at the time of forming the outermost layer of the second mixed layer 8b are set as the start point, and the final film formation condition parameters of the surface layer 8c are set as the end points. Change. As a result, there is no abrupt difference in physical properties (hardness, elastic modulus, etc.) between the second mixed layer 8b and the surface layer 8c, and the adhesion between the second mixed layer 8b and the surface layer 8c is further improved. By increasing the bias voltage continuously or stepwise, the composition ratio of the graphite structure (sp ² ) and the diamond structure (sp ³ ) in the DLC structure is biased toward the latter, and the hardness is inclined (increased). .

  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 0.7 or less. When this ratio exceeds 0.7, the gradient structure for physically bonding WC and DLC in the second mixed layer 8b tends to be a discontinuous structure, and the adhesion is likely to deteriorate.

  By making the hard film 8 have a three-layer structure including the first mixed layer 8a, the second 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 and the cage sliding 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 abrasive wear that occurs when a hard foreign object intervenes in the raceway surface or the cage sliding 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 with the structure and physical properties as described above, when a load (high contact stress) such as rolling contact is applied when the bearing is used, impact force or local sliding Even when subjected to a thermal shock due to heat generation, the film can be prevented from being worn or peeled off, and even in a severely lubricated state, there is little damage to the raceway surface, the cage sliding surface, etc., resulting in a long life. In addition, when a new metal surface is exposed in a rolling bearing encapsulated with grease, grease degradation is promoted by catalytic action. However, in the rolling bearing of the present invention, the raceway surface, rolling surface, and cage sliding contact due to metal contact are caused by a hard film. Since the surface can be prevented from being damaged, 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 surface layer 8c is 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 figure, the substrate 12 is an inner ring, an outer ring, a rolling element, or a cage, which are bearing members to be deposited, but is schematically shown as a flat plate. As shown in FIG. 6, an inner magnet 14 a and an outer magnet 14 b having different magnetic characteristics 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.

  The surface layer 8c uses this apparatus and uses a graphite target and a hydrocarbon-based gas in combination as a carbon supply source, and the amount of introduction of the hydrocarbon-based gas with respect to the amount 100 of introduction of the Ar gas into the apparatus. It is generated from the carbon source under the conditions that the ratio 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. It is preferable that carbon atoms are deposited on the second mixed layer 8b. This preferable condition will be described below.

  By using a graphite target and a hydrocarbon-based gas in combination as a carbon supply source, adhesion with the second mixed layer 8b can be improved. 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 second 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 serving as the substrate 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.

  The formation of the first mixed layer 8a and the second mixed layer 8b is also preferably performed using a UBMS apparatus using Ar gas as the sputtering gas. When forming the first mixed layer 8 a, a Cr target and a WC target are used in combination as the target 15. In forming the second mixed layer 8b, (1) a WC target, and (2) a graphite target and a hydrocarbon-based gas are used. The target used for each layer is sequentially replaced every time the layers are formed.

  The first mixed layer 8a is formed continuously or stepwise while increasing the sputtering power applied to the WC target and decreasing the power applied to the Cr target. Thereby, it can be set as the layer of the gradient composition which the content rate of Cr is small toward the 2nd mixed layer 8b side, and the content rate of WC becomes high.

  The second mixed layer 8b is formed continuously or stepwise 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.

  In order to set the hydrogen content in the second mixed layer 8b in the above range (10 to 45 atomic%), 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. Is increased in comparison with normal sputtering conditions. For example, the ratio of the introduction amount of the hydrocarbon-based gas is 5 to 40, more preferably 10 to 40 (volume part) with respect to the introduction amount 100 (volume part) of Ar gas into the UBMS apparatus (deposition chamber). ). Other conditions such as the degree of vacuum in the apparatus and the bias voltage during the formation of the second mixed layer are the same as the preferred film formation conditions for the surface layer described above.

  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 has been found that the influence of the substrate shape is large. For example, on a flat surface, a hard film that does not peel immediately after film formation and has a large critical peel load in the scratch test is formed immediately after film formation on curved surfaces such as inner and outer ring raceways of rolling bearings and cage pocket surfaces of rolling bearings. In some cases, it may be peeled off or may be easily peeled off during use, even if it is not peeled off immediately after film formation. As a result of intensive studies, the present inventors have determined that the hard film formed on the inner and outer ring raceway surfaces of the rolling bearing, which is a curved surface, the rolling surface of the rolling element, and the cage sliding surface (such as the pocket surface) as described above. And (1) Cr / WC first mixed layer (composition gradient), (2) WC / DLC second mixed layer (composition gradient), and (3) DLC surface layer. In addition, it has been found that by setting the hydrogen content of the second mixed layer within a predetermined range, it is possible to significantly improve the peel resistance even when receiving a high contact stress, and to prevent the hard film from peeling.

[Film formation on flat plate and inner / outer ring]
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.

The base material, UBMS apparatus, and sputtering gas used for evaluation of the hard film are as follows.
(1) Base material: Base material shown in each table (2) Base material dimensions, etc .: Surface roughness disks shown in each table (φ48 mm × φ8 mm × 7 mm, film formation on a plane)
(3) UBMS equipment: manufactured by Kobe Steel; UBMS202 / AIP composite equipment (4) Sputtering gas: Ar gas

The conditions for forming the first mixed layer (underlayer) will be described below. The inside of the deposition chamber is evacuated to about 5 × 10 ⁻³ Pa, the substrate is baked with a heater, the surface of the substrate is etched with Ar plasma, and the sputtering power applied to the Cr target and the WC target is adjusted. , A layer in which the composition ratio of Cr and WC was inclined was formed. The bias voltage applied to the substrate is 150V. This layer is a layer having a small Cr content and a high WC content from the base material side toward the second mixed layer side. In addition, when using it as mixed layers other than Cr / WC, it formed on the same conditions except using a corresponding target.

The conditions for forming the second mixed layer (intermediate layer) will be described below. The inside of the film forming chamber is evacuated to about 5 × 10 ⁻³ Pa, and after etching the substrate surface (or the surface of the underlayer) with Ar plasma, while supplying methane gas, which is a hydrocarbon-based gas, The sputtering power applied to the graphite target was adjusted to form a layer in which the composition ratio of WC and DLC was inclined. The bias voltage applied to the substrate is 150V. This layer is a layer in which the content ratio of WC decreases and the content ratio of DLC increases from the first mixed layer side toward the surface layer side. The hydrogen content (atomic%) in the second mixed layer was determined by the above-described method by GDS analysis (glow discharge emission spectroscopic analysis). The methane gas introduction ratio is as shown in each table.

  The conditions for forming the surface layer are as shown in each table.

  An outline of the UBMS 202 / AIP combined apparatus is shown in FIG. FIG. 7 is a schematic diagram of a UBMS apparatus having an arc ion plating (hereinafter referred to as AIP) function. As shown in FIG. 7, the UBMS 202 / AIP combined device instantaneously vaporizes and ionizes the AIP evaporation source material 21 using the vacuum arc discharge to the base material 23 arranged on the disk 22, 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. 6), this is an apparatus having a UBMS function capable of controlling the characteristics of a film deposited on a 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 first mixed layer, a second mixed layer, and a surface layer are formed as a UBMS film on a bearing member (inner ring, outer ring) serving 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.

Examples A1-A10, A12, Comparative Examples A1-A7, Reference Examples A1-A9
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 the first mixed layer and the second mixed layer having 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 pieces were subjected to the following wear test, hardness test, film thickness test, scratch test, and thrust type rolling fatigue test (other than the reference example). The results are shown in each table. In addition, Table 1 below 1) -7) is the same also in Table 2-7.

Example A11
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 substrate was attached to a UBMS / AIP composite apparatus, and the first mixed layer (Cr / WC) and the second 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 A1, The result is written together in Table 1.

<Friction and wear test>
The obtained test piece was subjected to a friction test using a friction tester shown in FIG. FIG. 8A shows a front view, and FIG. 8B 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 part 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>
The obtained test piece was subjected to a scratch test using Nanotech: Level Test RST, and the critical peel 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 (φ48 mm × φ8 mm × 7 mm), using a test machine shown in FIG. 9, as a thrust type rolling fatigue test, “low lambda condition” assuming that the lubrication state of the bearing is severe, Two conditions, “high lambda conditions”, assuming a good lubrication state, 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: 9.2
Maximum contact surface pressure: 3.5 GPa
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. 9, the testing machine has a configuration in which the rolling element 42 rolls between a disk-shaped test piece 41 and a raceway (51201) 45, and the test piece 41 has an alignment ball 43. Is supported through. 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 confirmation for 20 hours, the test piece is attached again and the test is continued. The lifetime is shown in Table 1 and Table 2 together. In addition, as a life determination, under low lambda conditions, those having a life of 1500 h or more are recorded as “◯”, and those having a life less than 1500 h are 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>
Films were actually deposited on the following inner ring raceway surface and outer ring raceway surface of 6206 rolling bearings (deep groove ball bearings) under the conditions of Examples and Comparative Examples, and peeling of the hard film from each member immediately after deposition was confirmed. did. 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.
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 on which the hard film was formed in the film formation test, and a life test was performed from the test machine of FIG. 10 using this test bearing. . As shown in FIG. 10, the testing machine rotatably supports a shaft 55 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. In addition, as a life judgment, those having a life of 200 h or more are recorded as “◯”, those having a life less than 200 h are recorded as “x”, and the results are also shown in each table.

  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. On the other hand, Comparative Examples A1 to A5 having different film structures resulted in poor peel resistance. Moreover, although the film structure (three-layer structure) was the same, Comparative Examples A6 and A7 in which the hydrogen content in the second mixed layer was not within the scope of the present invention resulted in poor peel resistance under high lambda conditions. .

Examples A13 to A18, Comparative Examples A8 to A10
The hard film of the present invention was subjected to the following fine wear test to evaluate its resistance to fretting wear. Test pieces (φ48 mm × φ8 mm × 7 mm, film-formed on a plane) were produced under the conditions shown in Table 4. Each layer was formed under the same conditions as in Example A1 except for the conditions shown in Table 4.

<Fine wear test>
FIG. 11 shows a fine wear tester. As shown in FIG. 11, a fine wear tester 61 is used to place a steel ball 63 loaded with a radial load 64 on a test piece 62 coated with grease 65 and reciprocate in the horizontal direction AB under the following conditions. The wear depth and specific wear amount of the test piece 62 and the wear amount of the steel ball 63 were measured.

[Measurement condition]
Grease: Calcium / lithium soap / mineral oil grease Radial load: 10kgf
Maximum contact surface pressure: 2.5 GPa
Frequency: 30Hz
Reciprocating amplitude: 0.47mm
Test time: 4 hours

  As shown in Table 4, it can be seen that the hard film of each example is excellent in fretting resistance. Moreover, the wear of the steel ball as the counterpart material could be suppressed. On the other hand, Comparative Example A8 in which the hydrogen content in the second mixed layer is not within the scope of the present invention and Comparative Examples A9 and A10 having different film structures are inferior in fretting resistance and the wear amount of the steel ball as the counterpart material is large. As a result.

[Film formation on flat plate and cage]
As a hard film to be formed on the cage of the rolling bearing of the present invention, a hard film is formed on a predetermined base material, and the physical properties of the hard film are evaluated, and the same hard film is held on the rolling bearing. The film was actually formed on the instrument sliding contact surface, and the bearing was evaluated.

  The base material used for evaluation of the hard film is the base material in each table. The substrate dimensions, the UBMS apparatus, the sputtering gas, the underlayer and the intermediate layer are formed under the same conditions as in the above [Film formation on flat plate and inner / outer ring].

Examples B1-B11, B13, Comparative Examples B1-B9, Reference Examples B1-B8
The base materials shown in Tables 5 to 7 were ultrasonically cleaned with acetone and then dried. After drying, the substrate was attached to a UBMS / AIP composite apparatus, and the first mixed layer and the second mixed layer having 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 same friction and wear test, hardness test, and film thickness test as those in the above [Film formation on flat plate and inner / outer ring]. The results are shown in each table.

Example B12
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 substrate was attached to a UBMS / AIP composite apparatus, and the first mixed layer (Cr / WC) and the second mixed layer (WC / DLC) having the materials shown in Table 5 were formed under the above-described formation conditions. A DLC film as a surface layer was formed on the film formation conditions shown in Table 5 to obtain a test piece having a hard film. About the obtained test piece, it uses for the test similar to Example B1, The result is written together in Table 5.

<Deposition test on bearing cage>
The film formation was actually performed on the following cage sliding surface (pocket surface) for 6204 rolling bearing (deep groove ball bearing) under the conditions of Examples and Comparative Examples, and the hard film from the cage immediately after film formation was formed. 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.
Cage: Steel plate cage with two cracks (Hard film is formed on the sliding contact surface with the rolling element. Cage base material (material, hardness, surface roughness) is as shown in each table)

<Bearing life test>
A test 6204 rolling bearing (deep groove ball bearing) was assembled using the cage in which the hard film was formed in the film formation test, and the life test was performed from the test machine of FIG. 12 using this test bearing. . As shown in FIG. 12, the testing machine rotates and supports the shaft rotated by the pulley 72 with the test bearing 71 while being loaded with a load from the load coil spring 73. 74 is a cartridge heater, and 75 is a thermocouple. Test conditions are shown below.

Cage: Steel plate cage with two cracks (Hard film is formed on the sliding contact surface with the rolling element. Cage base material (material, hardness, surface roughness) is as shown in each table)
Test bearing: 6204 (rubber seal)
Lubrication: Lithium ester grease (base oil viscosity at 40 ° C 26mm ² / s, miscibility of 260)
Enclosed amount: 15% (total space volume ratio)
Load: radial load 67N, axial load 67N
Rotation speed: 10000r / min (inner ring rotation)
Temperature: 150 ° C

  The life form is burn-in, and the torque increases rapidly as the life is reached. In this test, the time (h) until the testing machine stopped due to overload of the motor was defined as the life. The results are shown in each table. In addition, as a life judgment, “O” is recorded for those whose lifetime is 350 h or more, “Δ” is recorded for 200 h or more and less than 350 h, and “X” is recorded for less than 200 h, and the results are also shown in each table.

  As shown in Table 5, the hard film of each example was excellent in wear resistance and adhesion, and could prevent the hard film from peeling from the cage even when the bearing was used.

  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, the rolling surface of the rolling element, the cage sliding contact surface, etc., and can exhibit the characteristics of the DLC body. Excellent in seizure resistance, wear 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 8a First mixed layer 8b Second mixed layer 8c Surface layer 8d Relaxation layer portion 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 Shaft 61 Fine wear tester 62 Test piece 63 Steel ball 64 Radial load 65 Grease 71 Test bearing 72 Pulley 73 Load coil spring 74 Cartridge heater 75 Thermocouple

Claims (13)

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, a plurality of rolling elements rolling between the inner ring raceway surface and the outer ring raceway surface, and a holding for holding the rolling element A rolling bearing comprising a vessel,
At least one bearing member selected from the inner ring, the outer ring, the rolling element, and the cage is made of a ferrous material,
It is a surface of the bearing member made of the iron-based material, and at least one surface selected from the inner ring raceway surface, the outer ring raceway surface, the rolling surface of the rolling element, and the sliding contact surface of the cage. A hard film is formed,
The hard film includes a first mixed layer mainly composed of chromium and tungsten carbide formed directly on the at least one surface, and a tungsten carbide formed on the first mixed layer. A film composed of a second mixed layer mainly composed of diamond-like carbon and a surface layer mainly composed of diamond-like carbon formed on the second mixed layer;
In the first mixed layer, the content of the chromium in the first mixed layer decreases continuously or stepwise from the at least one surface side to the second mixed layer side, and the first mixed layer A layer in which the content of the tungsten carbide in the layer is increased,
In the second mixed layer, the content of the tungsten carbide in the second mixed layer decreases continuously or stepwise from the first mixed layer side to the surface layer side, and the second mixed layer A layer in which the content of the diamond-like carbon in the layer is high,
A rolling bearing, wherein the hydrogen content in the second mixed layer is 10 to 45 atomic%.   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 rolling element is a ball, and the sliding contact surface of the cage is a pocket surface that holds the ball that is a sliding contact surface with the rolling element. 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 claim 1, claim 2 or claim 3. 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 0.7 or less. The rolling bearing according to any one of 4 . The iron-based materials forming the inner ring, the outer ring, and the rolling elements are high carbon chromium bearing steel, carbon steel, tool steel, or martensitic stainless steel, respectively. Item 6. The rolling bearing according to any one of Items 5 . The rolling bearing according to claim 6 , wherein a hardness of a surface on which the hard film is formed in the inner ring, the outer ring, or the rolling element is Hv 650 or more in terms of Vickers hardness. The iron-based material forming the cage is a cold-rolled steel plate, carbon steel, chromium steel, chromium molybdenum steel, nickel chromium molybdenum steel, or austenitic stainless steel. The rolling bearing according to any one of 7 . 9. The surface roughness Ra of the surface on which the hard film is formed in the inner ring, the outer ring, or the rolling element is 0.05 μm or less, or any one of claims 1 to 8. The rolling bearing described. In the cage, the surface roughness Ra of the sliding surface of the hard film is formed, the rolling bearing according to any one of claims 1 to 9, characterized in that at 0.5μm or less. The rolling bearing, the rolling bearing according to any one of claims 1 to 10, characterized in that the grease is sealed. A method for manufacturing a rolling bearing according to any one of claims 1 to 4,
Said surface layer, using the unbalanced magnetron sputtering apparatus using argon gas as a sputtering gas, a combination of a graphite target as a carbon source and hydrocarbon gas, into the apparatus of the argon gas The ratio of the introduction amount of the hydrocarbon-based gas to the introduction amount 100 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 serving as the base material is A method for manufacturing a rolling bearing, comprising forming a film by depositing carbon atoms generated from the carbon supply source on the second mixed layer under a condition of 70 to 150 V. The surface layer has a relaxation layer portion adjacent to the second mixed layer, and the relaxation layer portion includes a ratio of the introduction amount of the hydrocarbon-based gas, a degree of vacuum in the device, and the bias voltage. The method of manufacturing a rolling bearing according to claim 12 , wherein at least one of the first and second portions is a portion formed by changing continuously or stepwise.