JP2007291466A - Surface-treating method of metal, rolling-sliding member and rolling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface treating method of a metal with which the wear resistance can be improved by forming a high quality and toughness film on metal surfaces contacted with each other while receiving the surface pressures. <P>SOLUTION: On the metal surfaces contacted under state of mutually receiving the surface pressures in hypoid gears, a hardened layer having 0.1-200 μm thickness and ≥Hv600 hardness, is formed, respectively. In this hardened layer, a shot-peening treatment is performed by using a projection material having average grain diameter in the range of 3-150 μm and hardness of ≤0.8 times of the hardened layer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a metal surface treatment method, a rolling sliding member, and a rolling device, and is particularly suitable for application to a method of performing shot peening treatment on a metal surface on which a hardened layer is formed.

In general, in rolling support devices such as rolling bearings, gears, linear guides, and ball screws, high stress is repeatedly applied to the contact surfaces. Therefore, the constituent materials of these members are hard, resistant to loads, and fatigue. Properties such as long life and good wear resistance against sliding are required.
For example, in rolling bearings, the constituent materials of this member include Japanese Industrial Standard SUJ2 as bearing steel, Japanese Industrial Standard SUS440C or 13Cr martensitic stainless steel as stainless steel, and Japanese Industrial as case hardening steel. A steel obtained by quenching, carburizing or carbonitriding a standard SCR 420 equivalent steel is generally used. These materials are hardened or tempered to ensure necessary physical properties such as fatigue life, and have a hardness of HRC 58 to 64.

In addition, from the viewpoint of improving the fuel efficiency of the engine due to CO ₂ emission regulations, combined with lowering the viscosity of the lubricating oil to increase the rotational efficiency at high speed rotation, it improves the durability at high speed rotation or under lean lubrication. It is increasingly demanded. For this reason, in rolling support devices such as rolling bearings, gears, linear guides, and ball screws, further improvement in wear resistance is required.
In addition, many types of sliding bearing materials are used in various engines including automobiles. As the social demand for energy saving measures increases, the improvement of energy efficiency by further reducing friction of sliding bearings is required. Yes.

  In a slide bearing, generally, a shaft is supported by a surface, and the surface and the shaft make a relative sliding motion, so that only sliding friction occurs. For this reason, unlike rolling bearings and gears, soft metals such as Sn having lubricity, Sn—Zn alloys, and the like are used. Therefore, the sliding bearing is required to further improve the wear resistance.

  As a method for improving the wear resistance, for example, in the case of a rolling bearing, by controlling the surface roughness of the roller end face and the guide collar, a direct metal contact between the two is avoided as much as possible (Patent Document 1). ) When the lubricating film is broken and direct contact with the surface occurs, a method of adding molybdenum dialkyldithiocarbamate or the like to the lubricating oil as an extreme pressure additive for improving seizure resistance and wear resistance (Patent Document 2) ), Or by forming minute pits regularly arranged on the rolling contact surface or raceway surface by electrolytic discharge machining, it is possible to secure lubricating oil at the contact portion and improve the lubrication characteristics, thereby improving the wear resistance. A method of improving (Patent Document 3) is disclosed.

On the other hand, diamond-like carbon has a hardness similar to that of diamond, and its sliding resistance is as low as 0.2 or less, like molybdenum disulfide and fluororesin, so that it has been conventionally used as a lubricating material. in use.
For example, in a magnetic disk unit, a diamond-like carbon film of several tens of angstroms is formed on the surface of the magnetic head and the magnetic disk, thereby improving the lubricity between the magnetic head and the magnetic disk and protecting the surface of the magnetic disk. is doing.

  On the other hand, diamond-like carbon has attracted attention as a new lubrication material for rolling and sliding members due to the unique surface properties as described above, and has recently been used to impart lubricity to bearings. For example, Patent Document 4 discloses a method for reducing contact stress by forming a diamond-like carbon film containing metal on the raceway surface of a raceway or the surface of a rolling element in a rolling bearing.

In rolling devices such as rolling bearings, diamond-like carbon is applied to the raceway surface of the raceway and the surface of the rolling element by CVD, plasma CVD, ion beam forming, ionization deposition, non-equilibrium magnetron sputtering, etc. A method for forming a film is disclosed (Patent Documents 5 to 10).
Here, in the method disclosed in Patent Document 10, it is possible to make it difficult to cause breakage of the diamond-like carbon film due to repeated stress and peeling of the diamond-like carbon film from the base material, and in a rolling device such as a rolling bearing, It can also be used under conditions where a large contact stress acts and under no lubrication.

JP-A-10-196660 Japanese Patent Publication No. 5-79280 Japanese Patent Laid-Open No. 5-240254 International Publication No. WO99 / 14512 Japanese Patent Laid-Open No. 9-147464 JP 2000-136828 A JP 2000-205277 A JP 2000-205279 A JP 2000-205280 A JP 2003-56575 A

However, in the method disclosed in Patent Document 1, the center line average roughness σ ₁ of the sliding contact surface and the combined roughness (σ of the center line average roughness σ ₂ of the inner surface of the buttock where the sliding contact surface is in sliding contact (σ ₁ + σ ₂ ) ^1/2 is set to 0.09 μmRa or less. For this reason, there is a possibility that the wear resistance is excellent, but there is a problem that the life of the bearing is shortened by reducing the oil film parameter Λ by roughening the sliding contact surface.

Further, in the method disclosed in Patent Document 2, in an environment where lubrication is exhausted, even when an extreme pressure additive that improves seizure resistance and wear resistance is added to the lubricating oil, metal contact is not caused. Since it becomes easy to occur, there existed a problem that the effect of an extreme pressure additive was not exhibited.
In the method disclosed in Patent Document 3, the pit diameter depends on the nozzle diameter from which the electrolytic solution is jetted, and is limited to a diameter of about 100 μm. There was a problem that a great deal of time was required and a significant increase in cost was inevitable.

  Furthermore, in a method (Patent Documents 5 to 10) in which a diamond-like carbon film is formed on the raceway surface of a raceway of a rolling device such as a rolling bearing or the surface of a rolling element (Patent Documents 5 to 10), the conditions are such that a larger contact stress acts. Considering the use of, further improvements are desired. Here, the following two points can be considered as the causes of the damage of the diamond-like carbon film due to repeated stress and the peeling of the diamond-like carbon film from the base material.

  The first point is a problem of embrittlement of the metal intermediate layer interposed in order to improve the adhesion between the steel and the diamond-like carbon film. That is, since the metal constituting the metal intermediate layer and the carbon constituting the diamond-like carbon film are combined to produce brittle metal carbide, the metal intermediate layer becomes brittle and the diamond-like carbon film is easily damaged. In particular, when the metal intermediate layer is made of one kind of metal, the brittleness of the metal carbide is large, and therefore, the diamond-like carbon film is likely to be damaged.

  The second problem is that the diamond-like carbon film has a property of being hardly deformed even when stress is applied. Since the diamond-like carbon film is hard and highly elastic, if it is coated with a metal material with a small equivalent elastic constant such as stainless steel or bearing steel, the diamond-like carbon film becomes The diamond-like carbon film may not be able to follow the deformation and may be damaged.

Further, if the adhesion at the interface between the base material and the diamond-like carbon film is insufficient, the entire diamond-like carbon film may be peeled off from the base material.
Therefore, a first object of the present invention is to provide a metal surface treatment method capable of forming a high-quality and tough film on metal surfaces that are in contact with each other under surface pressure and improving wear resistance. Is to provide.
A second object of the present invention is to provide a rolling sliding member and a rolling device that can be suitably used under conditions where a large contact stress acts or under no lubrication.

  In order to solve the above-described problem, according to the metal surface treatment method of claim 1, the metal surfaces that are in contact with each other in a state of being subjected to surface pressure have a thickness of 0.1 μm or more and 200 μm or less, and are hard. A step of forming a hardened layer having a thickness of Hv600 or more, and a step of projecting a projection material having an average particle diameter of 3 to 150 μm and a hardness of 0.8 times or less that of the hardened layer onto the surface of the hardened layer It is characterized by providing.

Thereby, compressive residual stress can be provided to the hardened layer formed on the metal surface. For this reason, it is possible to form a high-quality, strong adhesive film on the metal surfaces that are in contact with each other under surface pressure, and to improve the wear resistance of rolling bearings, gears, linear guides, ball screws, etc. It becomes possible to improve.
Here, the average particle diameter of the projection material greatly affects the depth and magnitude of the compressive residual stress applied to the hardened layer. If the average particle diameter of the projection material is smaller than 3 μm, the extreme surface layer portion of the hardened layer. In addition to the fact that compressive residual stress is generated, the magnitude of the compressive residual stress is reduced, and the hardened layer cannot be strengthened.

On the other hand, if the average particle size of the projection material exceeds 150 μm, the compressive residual stress enters the depth direction too deep and occurs in the base material beyond the hardened layer, causing brittleness of the base material and fatigue life. Shorter.
If the hardness of the projection material exceeds 0.8 times that of the cured layer, the cured layer may be scraped off when the projection material is projected onto the cured layer. In addition, in order to ensure toughening of a hardened layer in a short time, it is preferable that the hardness of a projection material shall be 1/5 or more of the hardness of a hardened layer.

The metal surface treatment method according to claim 2 is characterized in that the projection speed of the projection material is 50 m / sec or more.
Thereby, while generating sufficient collision energy, the projection material can be projected onto the surface of the cured layer, and it is possible to apply compressive residual stress to the depth of the cured layer, and the cured layer and the base material. Can be promoted. For this reason, a strong coating can be formed on the metal surfaces that are in contact with each other under surface pressure, and a metal surface treatment method having excellent wear resistance can be provided.
In order to promote diffusion between the hardened layer and the base material, it is preferable to perform the shot peening process at a room temperature or higher and a temperature at which the hardened layer and the base material are not annealed. For example, in the case of a steel material, the tempering temperature is preferably set below.

According to the metal surface treatment method of the third aspect, the projection pressure of the projection material is 0.1 MPa or more.
Thereby, diffusion bonding can be caused at the interface between the hardened layer and the base material, and a metal surface treatment method having excellent adhesion and wear resistance can be provided.

According to the metal surface treatment method of claim 4, the projecting material is a soft material made of zinc, tin, copper, aluminum, nickel or titanium, a soft alloy made of zinc alloy, tin alloy or copper alloy, Resin material made of PTFE, nylon, polycarbonate or polyplus, walnut (walnut shell), apricot (apricot seed), peach (peach seed) resin material, glass beads, SiC, zirconia or hard material made of steel It is selected.
Thereby, the optimal projection material can be selected according to a projection speed and a projection pressure, and the metal surface treatment method excellent in adhesiveness and abrasion resistance can be provided.

  Further, according to the rolling sliding member of claim 5, the rolling is made of a steel base material in which a diamond-like carbon layer is coated on a contact surface where relative rolling contact or sliding contact occurs with the counterpart member. In the sliding member, the diamond-like carbon layer includes a carbon layer made of carbon from the surface side, a composite layer made of tungsten or silicon and carbon, a single layer made of tungsten or silicon, a composite metal layer made of tungsten, silicon and chromium, It has a five-layer structure of a metal layer made of chromium, the equivalent elastic constant of the diamond-like carbon layer is 100 GPa or more and 240 GPa or less, and the contact surface coated with the diamond-like carbon layer is 0.05 MPa or more and 0.6 MPa Shot peening at the following projection pressures Is applied, the surface roughness Ra of the contact surface on which the diamond-like carbon layer is coated is characterized by at 0.2μm or less than 0.03 .mu.m.

  As a result, the intermediate metal layer interposed between the steel base material and the diamond-like carbon layer can be composed of a plurality of metals, and the carbon and metal constituting the diamond-like carbon film are combined to form a metal. Even when carbide is generated, it becomes possible to suppress the brittleness of the metal carbide, and after applying compressive residual stress to the surface layer portion of the diamond-like carbon layer, the equivalent elastic constant of the diamond-like carbon layer is set. It can be made smaller than the base material.

  For this reason, it is possible to form a high-quality and tough diamond-like carbon layer with excellent adhesion on the surface of a steel base material, and the diamond-like carbon layer can follow the deformation of the base material. Therefore, it is possible to prevent the diamond-like carbon layer from being damaged or peeled off even under conditions where large contact stress is applied or under non-lubricated conditions, so it can be used for rolling bearings, gears, linear guides, ball screws, etc. A diamond-like carbon layer can be suitably used.

Here, if the roughness of the contact surface is too rough, there will be a problem with the acoustic surface when relative rolling contact or sliding contact with the counterpart member occurs, so the surface roughness Ra is 0.2 μm or less. In addition, the surface roughness Ra was set to 0.03 μm or more in consideration of the film-forming ability of the diamond-like carbon layer.
In addition, by applying shot peening treatment on the contact surface covered with the diamond-like carbon layer, compressive residual stress can be applied to the surface portion of the diamond-like carbon layer, and peeling of the diamond-like carbon layer can be suppressed. Can do. Here, by setting the projection pressure of the shot peening treatment to 0.05 MPa or more and 0.6 MPa or less, it is effective for the surface layer portion of the diamond-like carbon layer while preventing the diamond-like carbon layer from peeling off during the shot peening treatment. Compressive residual stress can be applied.

  In addition, by setting the equivalent elastic constant of the diamond-like carbon layer to 100 GPa or more and 240 GPa or less, the equivalent elastic constant of the diamond-like carbon layer can be made smaller than that of the base material, and diamond-like carbon when repeated stress is applied. The layer can be deformed. For this reason, the diamond-like carbon layer can follow the deformation of the base material, and damage to the diamond-like carbon layer can be suppressed.

  Here, when the equivalent elastic constant of the diamond-like carbon layer exceeds 240 GPa, the equivalent elastic constant of the diamond-like carbon layer becomes larger than that of the base material. It becomes difficult to follow the deformation, and the diamond-like carbon layer is easily damaged. On the other hand, when the equivalent elastic constant of the diamond-like carbon layer is less than 100 Pa, the hardness of the diamond-like carbon layer is lowered, so that the wear resistance of the diamond-like carbon layer is deteriorated.

Moreover, according to the rolling sliding member of Claim 6, the hardness of the projection material used for the said shot peening process is Hv450 or less, It is characterized by the above-mentioned.
Thereby, compressive residual stress can be significantly given to the surface layer portion of the diamond-like carbon layer while allowing the diamond-like carbon layer to follow the deformation of the base material. Here, when the hardness of the projection material exceeds Hv450, the work hardening of the metal layer and the composite metal layer proceeds, and it becomes difficult for the diamond-like carbon layer to follow the deformation of the base material when repeated stress is applied. For this reason, the diamond-like carbon layer is easily damaged.

Moreover, according to the rolling sliding member of Claim 7, the ratio of the carbon in the said composite layer is increasing gradually toward the surface side.
Thereby, the ratio of carbon on the base material side can be reduced, and the adhesion between the diamond-like carbon layer and the steel base material can be improved.
In the rolling sliding member according to claim 8, the diamond-like carbon layer is formed by a nonequilibrium magnetron sputtering method.
Thereby, the amount of ions irradiated to the base material during film formation can be increased, and a high-quality and tough diamond-like carbon layer can be formed on the surface of the base material.

  According to the rolling device of claim 9, the first member having the first raceway surface, the second member having the second raceway surface disposed opposite to the first raceway surface, and the first raceway. A rolling element that is freely rollable between a surface and the second raceway surface, and at least one of the first member, the second member, and the rolling element is at least one of claims 5 to 8. It is formed with the rolling sliding member of any one of these.

  This makes it possible to cover a rolling sliding member that constitutes a rolling device with a high-quality and tough diamond-like carbon layer having excellent adhesion, and under conditions where no large contact stress acts or no lubrication. Even underneath, the diamond-like carbon layer can be prevented from being damaged or peeled off, so that the life of rolling bearings, gears, linear guides, ball screws, etc. can be extended.

Hereinafter, a metal surface treatment method according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view showing a schematic configuration of a hypoid gear according to an embodiment of the present invention.
In FIG. 1, the hypoid gear is provided with a hypoid pinion gear 11 and a hypoid ring gear 12. The hypoid pinion gear 11 is provided with a drive side rotary shaft 10, and the hypoid ring gear 12 is provided with a driven side rotary shaft (not shown). The hypoid pinion gear 11 and the hypoid ring gear 12 mesh with each other. Pairs are configured.

Here, the rotation center axis O1 of the hypoid pinion gear 11 and the hypoid ring gear 12 rotation center axis O2 are shifted by an eccentric amount E and are perpendicular to each other, so that the rotation center axes O1 and O2s do not intersect each other. In addition, the amount of slippage of the tooth surface during power transmission is larger than that of the spur gear or the bevel gear.
For example, when a hypoid gear is used in a vehicle power transmission device, the drive-side rotary shaft 10 is connected to a transmission output shaft, and the hypoid ring gear 12 is attached to a differential case.

Here, a hardened layer having a thickness of 0.1 μm or more and 200 μm or less and a hardness of Hv600 or more can be formed on the metal surfaces that are in contact with each other in the state where the hypoid gears are subjected to surface pressure. The hardened layer can be subjected to shot peening using a projection material having an average particle diameter of 3 to 150 μm and a hardness of 0.8 times or less that of the hardened layer.
As a result, compressive residual stress can be applied to the hardened layer formed on the metal surface, and the depth and size of the compressive residual stress applied to the hardened layer can be optimized. Therefore, it is possible to form a high-quality and tough coating with excellent adhesion on the metal surfaces that are in contact with each other by receiving the surface pressure, and it is possible to improve the wear resistance of the hypoid gear.

FIG. 2 is a cross-sectional view showing a metal surface treatment process according to an embodiment of the present invention.
In FIG. 2A, a metal substrate 21 is prepared. Here, when performing a surface treatment process to a gear, you may form a gear in steel used as the metal base 21 in a gear cutting process. In the gear cutting step, cutting can be performed by hobbing using a hobbing machine or gear cutting using a pinion cutter and a rack cutter. Hobbing is a wound cutting method in which gears are cut out by relative movement between the hob and the gear material. The hob is a tool in which a cutting blade with a rack tooth shape is formed in a screw shape on the cylindrical surface, and by rotating the gear material at a constant ratio with the rotation of the hob, by sending the hob in the gear axis direction, It is possible to perform gear generation.
Of the gears, hypoid gears with curved tooth traces can be created by cutting teeth using a circular cutter or by cutting teeth using a conical hob. it can.

Next, as shown in FIG. 2B, a hardened layer 22 is formed on the surface of the metal substrate 21. As a method of forming the hardened layer 22 on the surface of the metal substrate 21, a heat treatment such as a carburizing process can be performed. When the gear material is carburized, the carbon content of the steel of the gear material increases. A hardened layer can be formed on the surface of the gear.
As the hardening treatment other than the carburizing treatment, for example, heat treatment such as carbonitriding and nitriding, surface treatment with hard Cr plating, CrN, TiN, TiCN, etc., thermal treatment, surface treatment with diamond-like carbon, etc. However, diamond-like carbon is most preferable as the hardened layer 22 because excellent low friction and low wear can be obtained. Further, if necessary, the tooth surface may be finished flat by performing a surface finish such as lapping or honing that is a polishing process or a sheaving that is a cutting process. In addition, when the polishing process is performed after the hardened layer 22 is formed, the polishing process before the formation of the hardened layer 22 may be omitted as necessary.

  Here, when the hardened layer 22 is formed on the surface of the metal substrate 21, the hardness of the hardened layer 22 is preferably Hv600 or more. Further, the thickness W of the cured layer 22 is preferably 0.1 μm or more and 200 μm or less. In particular, in the cured layer 22 having a gradient so that the hardness decreases uniformly in the depth direction from the surface layer, the Hv is 600 or less. It must not exceed 200 μm in the depth direction.

  Next, as shown in FIG. 2C, the shot peening process of the hardened layer 22 is performed by projecting the projection material 23 onto the surface of the hardened layer 22. Here, the average particle diameter R of the projection material 23 is preferably within a range of 3 to 150 μm, and the hardness of the projection material 23 is preferably 0.8 times or less that of the hardened layer 22. Moreover, it is preferable that the projection speed of the projection material 23 is 50 m / sec or more, and the projection pressure of the projection material 23 is 0.1 MPa or more.

As a result, compressive residual stress can be applied to the hardened layer 22 formed on the surface of the metal substrate 21, and a high-quality and strong adhesive film can be applied to the metal surfaces that are in contact with each other under surface pressure. Since it becomes possible to form, it becomes possible to improve abrasion resistance, such as a rolling bearing, a gearwheel, a linear guide, a ball screw.
As an example, carbonitriding (adjusted to be HRC60 or higher by performing quenching and tempering after performing treatment at 930 ° C. for 5 hours) was performed on the surface of the gear made of SCM435, and polishing was performed. Later, diamond-like carbon was formed.

  Here, the diamond-like carbon is a carbon layer made of carbon from the surface side, a composite layer made of tungsten or silicon and carbon, an intermediate layer made of tungsten, silicon, titanium, or molybdenum, tungsten, silicon, titanium or It is preferable to have a five-layer structure of a composite metal layer made of chromium and one of molybdenum and a metal layer made of chromium.

The portion coated with diamond-like carbon preferably has a friction coefficient of 0.3 or less, and the equivalent elastic constant of the diamond-like carbon layer is preferably 100 GPa or more and 240 GPa or less.
For thin films such as diamond-like carbon layers, the elastic constants cannot be measured by ordinary methods, and therefore equivalent elastic constants based on the elastic constants were obtained. That is, the indentation depth was measured with a microhardness meter at least within the thickness of the diamond-like carbon layer, and the equivalent elastic constant was determined from the resulting load-unloading curve.

For example, when the thickness of the diamond-like carbon layer was 2 μm, the indentation load was appropriately set between 0.4 and 50 mN, and the measurement was performed. In this example, an equivalent elastic constant measured using a micro hardness tester manufactured by Eolinix Co., Ltd. and an indentation load of 50 mN was used.
As another method for measuring the equivalent elastic constant, there is a method using a micro hardness measuring device manufactured by Fischer. In this method, it is preferable not to use a micro Vickers hardness meter but to use a micro hardness meter or a nano indentator that can be controlled by electrostatic capacity. And an equivalent elastic constant can be calculated | required from the amount of elastic deformation of the load-unloading curve obtained from the micro hardness tester or the nano indentator by making the indentation depth within the thickness of the diamond-like carbon layer.

In addition, when the equivalent elastic constant of the surface of HRC60 steel carbon chromium steel (SUJ2) is calculated | required by said method, it will be 250 GPa, and will become larger than the value of 210 GPa described in the normal catalog etc. This is because in the above method, since measurement is performed on a small indentation region, it is influenced by the work hardened layer on the surface of SUJ2.
The diamond-like carbon layer is preferably formed by a nonequilibrium magnetron sputtering method.
Such a physical film formation method is easy to obtain a diamond-like carbon layer having a suitable equivalent elastic constant and strength as compared with CVD method, plasma CVD method, ion beam formation method, ion chemical vapor deposition method, etc. It is suitable for parts that make up a rolling device with large contact stress.

  In the embodiment described above, a rolling device such as a rolling bearing that can be formed on a rolling sliding member using a diamond-like carbon layer that is not easily damaged even when a large contact stress is applied as a lubricating film, and that is subjected to a large contact stress. It can use suitably for the component of these. In addition, since it has excellent lubricity, it is possible to use the rolling sliding member suitably even under non-lubricated conditions, and there is little wear and heat generation, and it is strong against repeated stress and has a long service life. Can be achieved.

  A diamond-like carbon layer having a composite layer composed of a metal and carbon is excellent in adhesion and small in brittleness, so that the diamond-like carbon layer is used even under conditions where a large contact stress acts or under no lubrication. Therefore, it can be suitably used for rolling sliding members and rolling devices. And, by setting the coefficient of friction of the part of the contact surface with the mating member that is covered with the diamond-like carbon layer to 0.3 or less, the diamond-like carbon layer is easy even when the lubrication condition is severe, for example. It is possible to prevent the film from peeling off or causing seizure.

Furthermore, by setting the equivalent elastic constant of the diamond-like carbon layer to 100 GPa or more and 240 GPa or less, it is possible to prevent the diamond-like carbon layer from being damaged even when repeated stress is applied.
In order to evaluate the metal surface treatment method described above, a durability test was performed under the conditions shown below using the hypoid gear of FIG. In addition, regarding the measurement of the amount of wear, the difference in weight before and after the test was obtained and represented by the ratio of the amount of wear based on Comparative Example 1. Regarding the number of tests, 10 tests were performed for each condition, and the test time was 100 hours.
Surface pressure: 0.8 GPa
Number of revolutions: 3000 revolutions Sliding speed: None Temperature: 80 ° C
Lubrication: Oil (equivalent to VG68)

Further, using a ball-on-disk test apparatus as shown in FIG. 3, the test was performed under the conditions shown below, and the amount of wear was measured. In addition, regarding the measurement of the amount of wear, the difference in weight before and after the test was obtained and represented by the ratio of the amount of wear based on Comparative Example 1.
Surface pressure: 1.5 GPa
Sliding speed: 0.96m / sec
Temperature: 25 ° C
Lubrication: No lubrication Here, the ball-on-disk test apparatus is provided with a rotating plate 31. Then, the ball 33 is mounted on the holder 32, and the ball 33 can be worn by pressing the ball 33 against the rotating plate 31 while applying a load.

FIG. 4 is a view showing a durability test result of a surface-treated gear according to an embodiment of the present invention together with a comparative example.
In FIG. 4, when the thickness of the cured layer is less than 0.1 μm or exceeds 200 μm, or when the average particle size of the projection material is not within the range of 3 to 150 μm, or the hardness of the projection material is It can be seen that when it exceeds 0.8 times that of the hardened layer, the effect of improving the wear resistance is not so expected.
On the other hand, when the thickness of the cured layer is 0.1 μm or more and 200 μm or less, the average particle diameter of the projection material is 3 to 150 μm, and the hardness is 0.8 times or less of the cured layer, The effect of improving wear resistance could be obtained.

FIG. 5 is a diagram showing the relationship between the thickness of the cured effect of the surface-treated gear according to an embodiment of the present invention and the friction amount ratio together with a comparative example, and FIG. 6 is the surface treated according to the embodiment of the present invention. It is a figure which shows the relationship between the hardening effect thickness of a ball-on-disk, and friction amount ratio with a comparative example.
5 and 6, it can be seen that the thickness of the cured layer is preferably 0.1 μm or more and 50 μm or less in order to obtain excellent wear resistance. In this case, the projection speed of the projection material is preferably 50 m / sec or more, and the projection pressure of the projection material is preferably 0.1 MPa or more.

FIG. 7 is a longitudinal sectional view showing a schematic configuration of a thrust ball bearing according to one embodiment of the present invention, and FIG. 8 is an enlarged sectional view showing a portion A in FIG.
In FIG. 7, an inner ring 41 and an outer ring 42 are provided in the thrust ball bearing. A raceway surface 41a is provided on the outer surface of the inner ring 41, and a raceway surface 42a is provided on the inner surface of the outer ring 42. The raceway surfaces 41a and 42a are arranged to face each other. Between the raceway surfaces 41a and 42a, a plurality of balls 43 are arranged so as to be freely rollable, and the balls 43 are held by the cage 44 at equal intervals along the circumferential direction of the bearing. .

The inner ring 41, the outer ring 42, and the ball 43 can be made of steel such as SUJ2. The dimensions of the inner ring 41 and the outer ring 42 can be, for example, an inner diameter of 25 mm, an outer diameter of 52 mm, and a thickness of 18 mm. The cross-sectional shape of the raceway surfaces 41 a and 42 a is a curvature radius of 54% of the diameter of the ball 43. It can be made into the circular arc shape which has.
The inner ring 41, the outer ring 42, and the ball 43 can be brought into rolling contact or sliding contact with each other, and the raceway surface 41a of the inner ring 41, the raceway surface 42a of the outer ring 42, and the rolling surface 43a of the ball 43 are the contact surfaces. Equivalent to. On these contact surfaces, a diamond-like carbon layer D having lubricity and having an equivalent elastic constant of 100 GPa or more and 240 GPa or less is covered with the steel base material of the inner ring 41, the outer ring 42 and the ball 43. . Of the steel base materials of the inner ring 41, the outer ring 42, and the balls 43, the surface roughness Ra of the portion covered with the diamond-like carbon layer D can be set to 0.03 μm or more and 0.2 μm or less.

Further, as shown in FIG. 8, the diamond-like carbon layer D is composed of a carbon single layer D5 made of carbon from the surface side, a composite layer D4 made of tungsten or silicon and carbon, a single layer D3 made of tungsten or silicon, tungsten or silicon. And a five-layer structure of a composite metal layer D2 made of chromium and a metal layer D1 made of chromium.
Further, the contact surface coated with the diamond-like carbon layer D can be subjected to shot peening treatment at a projection pressure of 0.05 MPa or more and 0.6 MPa or less.

  Thereby, the intermediate metal layer interposed between the steel base material and the diamond-like carbon layer can be composed of a plurality of metals, and the carbon and metal constituting the diamond-like carbon layer D are bonded together. Even when metal carbide is generated, it becomes possible to suppress the brittleness of the metal carbide, and after applying compressive residual stress to the surface portion of the diamond-like carbon layer D, the equivalent of the diamond-like carbon layer D The elastic constant can be made smaller than that of the base material.

  For this reason, it becomes possible to form a high-quality and tough diamond-like carbon layer D with excellent adhesion on the surface of the steel base material, and the diamond-like carbon layer D follows the deformation of the base material. Is possible. For this reason, it is possible to prevent the diamond-like carbon layer D from being damaged or peeled off even under conditions in which a large contact stress acts or under non-lubrication, so a diamond-like carbon layer is suitable for a thrust ball bearing. Can be used.

Hereinafter, a method for forming the diamond-like carbon layer D will be described by taking the outer ring 42 as an example.
The outer ring 42 from which the oil has been degreased is installed in an advanced magnetron sputtering device manufactured by Kobe Steel, Ltd., and sputtering is performed with argon plasma, so that the track surface 42a of the surface of the base material is bombarded only for 15 minutes. gave.

  Then, by performing sputtering using chromium as a target, after forming a metal layer D1 made of chromium on the portion of the surface of the base material that becomes the raceway surface 42a, sputtering is performed using tungsten or silicon and chromium as a target. These two kinds of materials were deposited on the portion of the surface of the base material that would become the raceway surface 42a, and a composite metal layer D2 made of tungsten, silicon, and chromium was formed on the metal layer D1.

  Further, by sputtering using tungsten or silicon as a target, a single layer D3 made of tungsten or silicon is formed on the composite metal layer D2, and sputtering of carbon using carbon as a target while continuing sputtering of tungsten or silicon. As a result, a composite layer D4 made of tungsten or silicon and carbon was formed on the single layer D3. Here, when the composite layer D4 made of tungsten or silicon and carbon is formed, the sputtering efficiency of carbon may be gradually increased while the sputtering efficiency of tungsten or silicon is gradually decreased. Then, while continuing the sputtering of carbon, the sputtering of tungsten or silicon was terminated, and a carbon layer D5 made of carbon was formed on the composite layer D4. The film thickness of the entire diamond-like carbon layer D was 2.2 μm.

  By performing film formation by such sputtering, a diamond-like carbon layer D in which the composition of the layer gradually changes from a layer composed of two kinds of metals toward a layer composed of carbon (carbon layer D5). Can be formed. The diamond-like carbon layer D having such a structure can improve the adhesion between each layer (metal layer D1, composite metal layer D2, single layer D3, composite layer D4 and carbon layer D5) and lubricity. It is possible to improve the adhesion with the steel which is the base material which is the carbon layer D5 which is excellent.

  In addition, the advanced magnetron sputtering apparatus can be equipped with a plurality of targets used for sputtering, and the sputtering efficiency of each component can be arbitrarily controlled by independently controlling the sputtering power source of each target. The composition of the carbon layer D can be gradually changed. For example, in the step of forming the composite layer D4 and the carbon layer D5, while applying a negative bias voltage to the outer ring 42, the power of the sputtering power source (DC power source) of the metal target is reduced, and at the same time, the sputtering power source of the carbon target. What is necessary is just to increase the electric power of (DC power supply).

  FIG. 9 is a measurement chart showing the analysis results of the constituent elements forming the diamond-like carbon layer according to one embodiment of the present invention. In addition, in the example of FIG. 9, in order to analyze the structural element which forms the diamond-like carbon layer D, the glow discharge emission spectrometer (GDLS-9950 made by Shimadzu Corporation) was used. The horizontal axis represents the depth from the surface, and 0 nm represents the surface of the diamond-like carbon layer D. On the other hand, the vertical axis indicates the content of each element at the depth position.

  In FIG. 9, since information in the depth direction is obtained by discharge using argon gas, the curves indicating the content of each element are broad at the interface between the base material steel and the diamond-like carbon layer D. ing. Further, since the interface between the base material steel and the diamond-like carbon layer D is located near 8000 nm, it can be read from the measurement chart of FIG. 9 that the thickness of the diamond-like carbon layer D is about 8 μm. However, in this analysis method, the analysis is performed by discharge light emission for a circular portion having a diameter of 2 mm, so that the diamond-like carbon layer D appears to have a thickness of about 8 μm with accuracy in the depth direction. The actual thickness of the like carbon layer D is 2.2 μm.

  For the shot peening treatment of the diamond-like carbon layer D, an FD-4LD-501 type apparatus manufactured by Fuji Seisakusho Co., Ltd. was used. Here, the projection material was iron having a particle size of 30 to 60 μm, and the hardness of the projection material was adjusted to be Hv450 or less by heat treatment. The shot conditions are a projection distance of 150 mm and a processing time of 5 minutes. Moreover, the compressive residual stress given to the surface of the diamond-like carbon layer D was adjusted by appropriately setting the projection pressure within the range of 0.05 MPa to 0.6 MPa. In this embodiment, iron is used as the projection material. However, it is not limited to iron as long as it has a hardness of Hv450 or less.

  In the above-described method for forming the diamond-like carbon layer D, the method for forming the diamond-like carbon layer D by the nonequilibrium magnetron sputtering method has been described. However, a pulse laser arc deposition method, a plasma CVD method, or the like is used. It may be. However, it is best to use a non-equilibrium magnetron sputtering method that can easily control the equivalent elastic constant, plastic deformation hardness, and the like independently.

FIG. 10 is a diagram showing a relationship between the average roughness of the raceway center line and the peel life ratio of the thrust ball bearing according to one embodiment of the present invention, together with a comparative example.
In FIG. 10, when the surface roughness Ra of the contact surface coated with the diamond-like carbon layer D exceeds 0.2 μm, it can be seen that the peeling life is reduced. For this reason, the surface roughness Ra of the contact surface coated with the diamond-like carbon layer is preferably in the range of 0.03 μm to 0.2 μm. In addition, the surface roughness Ra of the contact surface coated with the diamond-like carbon layer is preferably as smooth as possible, and the surface roughness Ra is more preferably 0.08 μm or less.

FIG. 11 is a diagram showing a relationship between a projection pressure and a peeling life ratio at the time of shot peening processing according to an embodiment of the present invention, together with a comparative example.
In FIG. 11, it can be seen that when the projection pressure during the shot peening process is less than 0.05 MPa or exceeds 0.6 MPa, the peeling life is reduced. For this reason, it is preferable that the projection pressure at the time of shot peening is in the range of 0.05 MPa to 0.6 MPa.

FIG. 12 is a diagram showing the relationship between the hardness of the projection material and the peel life ratio in the shot peening process according to one embodiment of the present invention, together with a comparative example.
In FIG. 12, when the hardness of a projection material exceeds Hv450, it turns out that the peeling lifetime falls. For this reason, it is preferable that the hardness of a projection material shall be Hv450 or less.
In order to evaluate the diamond-like carbon layer D described above, a life test was performed under the conditions shown below using the thrust ball bearing of FIG.
Bearing dimensions: φ25 × φ52
Rotational speed: 1500min ^-1
Load: 900kg
Lubricating oil: VG68 turbine oil

FIG. 13 is a view showing a life test result of a thrust ball bearing formed with a diamond-like carbon layer according to an embodiment of the present invention together with a comparative example.
In FIG. 13, when the surface roughness Ra of the contact surface coated with the diamond-like carbon layer D exceeds 0.2 μm, or when the projection pressure is less than 0.05 MPa, or exceeds 0.6 MPa, or When the hardness of the projection material exceeds Hv450, it can be seen that the effect of improving the peeling life is not expected.
In contrast, the surface roughness Ra of the contact surface coated with the diamond-like carbon layer D is 0.03 μm or more and 0.2 μm or less, the projection pressure is 0.05 MPa or more and 0.6 MPa or less, and the hardness of the projection material is Hv450. By making the following, a large peeling life improvement effect could be obtained.

In the above-described method for forming the diamond-like carbon layer D, a thrust ball bearing has been described as an example. For example, deep groove ball bearings, angular ball bearings, cylindrical roller bearings, tapered roller bearings, needle roller bearings, automatic You may make it apply to radial type rolling bearings, such as a spherical roller bearing, and thrust type rolling bearings, such as a thrust roller bearing.
Moreover, in the film-forming method of the diamond-like carbon layer D described above, a rolling bearing has been described as an example of the rolling device. However, for example, various other rolling devices such as a linear motion guide bearing, a ball screw, and a linear motion bearing. You may make it apply to.

It is a perspective view showing a schematic structure of a hypoid gear according to an embodiment of the present invention. It is sectional drawing which shows the surface treatment process of the metal which concerns on one Embodiment of this invention. It is a perspective view which shows schematic structure of the ball-on-disk test apparatus used for evaluation of the surface treatment of the metal which concerns on one Embodiment of this invention. It is a figure which shows the endurance test result of the surface-treated gear which concerns on one Example of this invention with a comparative example. It is a figure which shows the relationship between the hardening effect thickness and friction amount ratio of the surface-treated gear which concerns on one Example of this invention with a comparative example. It is a figure which shows the relationship between the hardening effect thickness of the surface-treated ball-on-disk which concerns on one Example of this invention, and friction amount ratio with a comparative example. It is a longitudinal section showing a schematic structure of a thrust ball bearing concerning one embodiment of the present invention. It is sectional drawing which expands and shows the part of A of FIG. It is a measurement chart which shows the analysis result of the constituent element which forms the diamond-like carbon layer concerning one embodiment of the present invention. It is a figure which shows the relationship between the hardness of the projection material at the time of the shot peening process which concerns on one Example of this invention, and the peeling life ratio with a comparative example. It is a figure which shows the lifetime test result of the thrust ball bearing in which the diamond-like carbon layer based on one Example of this invention was formed with a comparative example. It is a figure which shows the relationship between the raceway centerline average roughness of the thrust ball bearing which concerns on one Example of this invention, and a peeling life ratio with a comparative example. It is a figure which shows the relationship between the projection pressure at the time of the shot peening process which concerns on one Example of this invention, and a peeling life ratio with a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Drive side rotating shaft 11 Hypoid pinion gear 12 Hypoid ring gear 21 Metal substrate 22 Hardened layer 23 Projection material 31 Rotating plate 32 Holder 33 Ball 41 Inner ring 41a, 42a Track surface 42 Outer ring 43 Ball 43a Rolling surface 44 Cage D Diamond like Carbon layer D1 Cr single layer D2 Cr / W or Si composite layer D3 W or Si single layer D4 W or Si / carbon composite layer D5 Carbon single layer

Claims (9)

Forming a hardened layer having a thickness of 0.1 μm or more and 200 μm or less and a hardness of Hv600 or more on metal surfaces that are in contact with each other in a state of receiving a surface pressure;
And a step of projecting a projection material having a mean particle size of 3 to 150 μm and a hardness of 0.8 times or less of the hardened layer onto the surface of the hardened layer. .   The metal surface treatment method according to claim 1, wherein a projection speed of the projection material is 50 m / sec or more.   The metal surface treatment method according to claim 1, wherein a projection pressure of the projection material is 0.1 MPa or more.   The projection material is made of a soft material made of zinc, tin, copper, aluminum, nickel or titanium, a soft alloy made of zinc alloy, tin alloy or copper alloy, a resin material made of PTFE, nylon, polycarbonate or polyplus, walnut ( 4. A walnut shell), apricot (apricot seed), peach (peach seed) resin-based material, glass beads, SiC, zirconia, or a hard material made of steel. The metal surface treatment method according to claim 1. In a rolling sliding member composed of a steel base material in which a diamond-like carbon layer is coated on a contact surface where relative rolling contact or sliding contact occurs with a mating member,
The diamond-like carbon layer is a carbon layer made of carbon from the surface side, a composite layer made of tungsten or silicon and carbon, a single layer made of tungsten or silicon, a composite metal layer made of tungsten, silicon and chromium, or a metal layer made of chromium. The five-layer structure
The equivalent elastic constant of the diamond-like carbon layer is 100 GPa or more and 240 GPa or less,
The contact surface coated with the diamond-like carbon layer is subjected to shot peening treatment at a projection pressure of 0.05 MPa or more and 0.6 MPa or less,
A rolling sliding member characterized in that the surface roughness Ra of the contact surface coated with the diamond-like carbon layer is 0.03 μm or more and 0.2 μm or less.   The rolling sliding member according to claim 5, wherein the shot material used in the shot peening treatment has a hardness of Hv450 or less.   The rolling sliding member according to claim 5 or 6, wherein a ratio of carbon in the composite layer gradually increases toward the surface side.   The rolling sliding member according to any one of claims 5 to 7, wherein the diamond-like carbon layer is formed by a non-equilibrium magnetron sputtering method. A first member having a first raceway surface;
A second member having a second raceway surface disposed opposite the first raceway surface;
A rolling element disposed so as to roll freely between the first raceway surface and the second raceway surface;
9. The rolling device according to claim 5, wherein at least one of the first member, the second member, and the rolling element is formed by the rolling sliding member according to claim 5. apparatus.

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