JPH11125248A - Rolling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide highly reliable and long service life corrosion resistance in a strong acid environment by forming a coating film of a nickel-tungsten alloy in a specific thickness on at least a single contact surface to contact with a rolling body, and setting the tungsten atomic weight ratio of its alloy to a specific rate. SOLUTION: A ball 3 being a rolling body is arranged between an outer ring 1 and an inner ring 2 of a ball bearing part, and is held by a holder 4. A contact surface of the outer ring 1 with the ball 3 is a raceway surface 5 of the outer ring, and a contact surface of the inner ring 2 with the ball 3 is a raceway surface 6 of the inner ring. Respective members of both the outer ring 1, the inner ring 2 and the ball 3 are bearing steel, and an Ni-W alloy coating film is formed on these whole surfaces by an electrolytic plating method. The tungsten atomic weight ratio of its alloy coating film is set to at least 35 wt.%, and a thickness is set to 2 to 30 μm. A ball bearing protected by the Ni-W coating film shows excellent corrosion resistance even if it touches a strongly corrosive solution of a strong acid such as a hydrochloric acid and a strong base used in a chemical pump.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling device used in a semiconductor manufacturing apparatus, a chemical pump and the like, and more particularly to an improvement in corrosion resistance mainly in a strongly acidic environment such as hydrochloric acid or sulfuric acid.

[0002]

2. Description of the Related Art Conventionally, various rolling devices such as rolling bearings, linear motion guide devices (linear guides), ball screws, and the like have been used in semiconductor manufacturing apparatuses and chemical pumps. Generally, these rolling devices are basically made of steel materials such as bearing steel, carburized steel, and stainless steel.
In the case of an application for contact with a strongly acidic chemical such as sulfuric acid, the surface of a steel member constituting a rolling device is disclosed in JP-A-63-1872.
2. A rolling device is manufactured by applying a coating of a nickel-phosphorous coating or a chromium coating which is a corrosion-resistant coating disclosed in JP-A-63-140120, or by using a ceramic material instead of the above steel material. I have.

[0003]

However, conventional rolling devices coated with a nickel-phosphorous coating or a chromium coating have satisfactory corrosion resistance to weak acids, some strong acids and alkalis. However, there is a problem that these films are dissolved with respect to strong hydrochloric acid, and even the base metal such as stainless steel is corroded.

On the other hand, a rolling device using a ceramic material exhibits strong corrosion resistance to acids and alkalis, but has a problem of high cost. Therefore, an object of the present invention is to replace nickel-phosphorus coating and chromium coating,
By forming a nickel-tungsten alloy coating (hereinafter, also referred to as a Ni-W coating) or a rhodium coating which is not applied to a conventional rolling device, a strong acid is maintained while maintaining the performance of the original rolling device. An object of the present invention is to provide a corrosion-resistant rolling device that can withstand use even in a severe environment where (particularly, strong hydrochloric acid) is present.

[0005] In addition, if the entire surface of the outer ring, inner ring, and rolling elements of the rolling bearing is coated, there is a problem that the life is short when the load is high. Rolling bearings in which the outer ring, inner ring, and rolling elements are all made of ceramics
Although it shows strong corrosion resistance to acids and alkalis and has no problem in durability, it has a problem of high cost.

Therefore, another object of the present invention is to provide a nickel
Nickel-tungsten (Ni-tungsten), which has not been applied to conventional rolling bearings in place of
W) An object of the present invention is to provide a rolling bearing formed of a rolling element made of silicon nitride or silicon carbide and a cage containing a fluorine resin and having excellent corrosion resistance and durability while forming a film or a rhodium film.

[0007]

In order to achieve the above object, a rolling device of the present invention has a rolling element disposed between an outer member and an inner member, and the rolling element is a rolling element of the outer member. A first contact surface that is a contact surface with the second member that is a contact surface with the rolling element of the inner member.
In a rolling device that rolls with respect to the contact surface, at least one of the rolling element, the first contact surface, and the second contact surface is coated with a nickel-tungsten alloy coating film.
The nickel-tungsten alloy is formed in a thickness of 30 μm, and a tungsten atomic weight ratio is at least 35% by weight.

Further, in the rolling device of the present invention, a rolling element is disposed between the outer member and the inner member, and the rolling element is a first contact surface which is a contact surface of the outer member with the rolling element. In a rolling device that rolls with respect to a surface and a second contact surface that is a contact surface of the inner member with the rolling member, the rolling device includes a rolling member, the first contact surface, and the second contact surface. At least one should have a rhodium coating of 0.1
It is characterized by being formed with a thickness of 10 to 10 μm.

The present invention is also a rolling bearing, wherein the rolling device comprises an outer ring, an inner ring, a rolling element, and a cage, wherein a coating of a nickel-tungsten alloy having a thickness of 2 to 30 μm is formed on the surface of the outer ring and the inner ring. The nickel-tungsten alloy has a tungsten atomic weight ratio of at least 3
5 wt%, and may be formed of a rolling element made of silicon nitride, silicon carbide, or zirconia, and a cage made of a material containing a fluororesin.

Further, according to the present invention, the rolling device includes an outer ring,
A rolling bearing comprising an inner ring, a rolling element, and a cage, wherein a nickel-tungsten alloy film is formed on the surface of the outer ring and the inner ring to a thickness of 2 to 30 μm, and a tungsten atomic weight ratio of the nickel-tungsten alloy is determined. At least 3
It can be 5% by weight and sealed with corrosion resistant grease. Further, in the case of a rhodium film, the amount of rhodium is 0.1.
It is characterized by being formed in a thickness of 1 to 10 μm.

Here, the outer member of the rolling device refers to an outer ring in a rolling bearing, a slider in a linear guide, and a nut in a ball screw. Further, the inner member of the rolling device refers to an inner ring in a rolling bearing, a guide rail in a linear guide, and a screw shaft in a ball screw.

Therefore, regarding the first contact surface, which is the contact surface of the outer member with the rolling element, and the second contact surface, which is the contact surface of the inner member with the rolling element, in the case of a rolling bearing, the outer ring is used. Is the first contact surface, and the raceway surface of the inner ring is the second contact surface. In the case of a linear guide, the raceway groove of the slider is the first contact surface, and the raceway groove of the guide rail is the second contact surface. In the case of a ball screw, the thread groove of the nut is the first contact surface, and the thread groove of the screw shaft is the second contact surface.

In the rolling device of the present invention, at least one of the rolling element, the first contact surface, and the second contact surface, which is the most worn in the rolling device, is coated with a Ni—W coating or a rhodium coating. ing. Needless to say, the number of coating locations may be three, that is, the rolling element, the first contact surface, and the second contact surface, and may cover the entire outer member or the entire inner member. Alternatively, the entire rolling device may be entirely coated with a Ni-W coating or a rhodium coating.

The Ni—W coating is excellent in acid resistance and alkali resistance, and has high hardness and wear resistance.
An extremely reliable corrosion-resistant rolling device is obtained.
Incidentally, the hardness of the Ni—W coating is usually about Hv600, but it can be further increased to Hv1300 by performing a heat treatment, which is very effective in improving the wear resistance.

The thickness of the Ni—W coating is 2 to 30 μm.
m. If the thickness is less than 2 μm, the coating is too thin to eliminate the pinhole, and the metal of the base material is corroded by a liquid such as acid or alkali which has penetrated from the pinhole. On the other hand, if the thickness exceeds 30 μm, the corrosion resistance is satisfactory, but the dimensional accuracy of the member after the coating is formed is reduced.
Rework must be performed to ensure accuracy, which is troublesome and increases the manufacturing cost.

The atomic weight ratio of tungsten (W) in the Ni—W coating of the present invention is at least 35% by weight.
And If the ratio is less than 35% by weight, nickel (N
i) The coating is difficult to become amorphous due to a large amount of the components, and particularly the corrosion resistance to strong acids is insufficient. On the other hand, the upper limit of the tungsten atomic weight ratio in the coating is preferably as high as possible.
It is difficult to exceed 0% by weight.

For forming the Ni-W film on the rolling device of the present invention, an electrolytic plating method is preferable. The electrolytic solution used for the electrolytic plating contains a nickel salt and a tungstate, and an organic complexing agent that forms a stable complex ion with those metal ions. Specifically, for example, nickel sulfate (NiSO ₄ .6H ₂ O) as a nickel salt and sodium tungstate (Na ₂ WO) as a tungstate
₄ · 2H ₂ 0), approximately in a weight ratio of citric acid or tartaric organic complexing agent 7: 7: the additional inclusion in the 10 ratio of the aqueous solution prepared to pH neutral to weakly acidic with an electrolytic solution, temperature 60 Electroplating using a member of a rolling device, which is an object to be plated, as a cathode at a temperature of 80 ° C. and a current density of 8 to 12 A / dm ² , Ni having a thickness of 2 to 30 μm and a tungsten atomic weight ratio of at least 35 wt% The -W coating can be suitably formed.

When it is sufficient to form the Ni—W coating only on a part of the rolling device member, the portion where the coating is not formed is masked (the masking agent is paint, rubber, etc.).
Plating may be applied.

The location of the rhodium coating of the rolling device of the present invention is as follows:
At least one of the rolling element, the outer member, and the inner member is covered. Of course, the entire surface of the rolling device may be covered with rhodium. The thickness of the rhodium coating is preferably 0.1 to 10 μm. If the thickness is less than 0.1 μm, the coating is too thin to eliminate the pinhole, and the metal of the base material is corroded by the acid and alkali entering from the pinhole. On the other hand, when the thickness exceeds 10 μm, the corrosion resistance is satisfactory, but rework due to a decrease in accuracy after the formation of the film and an increase in rhodium metal increase the cost. The hardness of the rhodium film is 600 to 700 in Vickers hardness, and is excellent in abrasion resistance.

For forming a rhodium film on the rolling device of the present invention, an electrolytic plating method is preferable. The plating solution used for the electrolytic plating is generally a sulfuric acid bath or a phosphoric acid bath. Specifically, it contains, for example, rhodium sulfate (2 to 3 g / l) and sulfuric acid (40 to 60 g / l). Electroplating is performed at room temperature, and the current density is 1.5 to ^{2 A} / dm ² .

When it is sufficient to form only a part of the rhodium film, the part where the film is not formed may be masked and plated. Rolling members are coated with rhodium by electrolytic plating.
A strike plating film of copper, platinum, gold or the like may be interposed.

When the rolling device is a rolling bearing, the rolling element can be made of silicon nitride, silicon carbide or zirconia ceramics. Silicon nitride, silicon carbide, or zirconia has better corrosion resistance and better wear resistance than the Ni-W alloy. Also, the outer ring, the inner ring, and the rolling elements made of different materials are more excellent in wear resistance than all the parts of the outer ring, the inner ring, and the rolling elements are made of the same material. When ceramics are used for the rolling elements, an increase in cost is hardly a problem. However, if the outer ring and the inner ring are made of ceramic, the cost becomes very high. Further, the retainer contains a fluororesin. Lubrication of the rolling bearing can be performed by a fluororesin transfer film from a cage containing the fluororesin. The fluororesin transfer film is excellent in corrosion resistance (chemical resistance), wear resistance (low dust generation), and lubricity (durability). The retainer is not particularly limited as long as it is not affected in a corrosive environment.
For example, stainless steel coated with a Ni-W coating or a rhodium coating may be used. Corrosion-resistant grease is used for the lubricant. Corrosion resistant greases include fluorine-based grease (fluororesin-fluorine oil). With ordinary lithium soap grease, sodium soap grease, etc.,
The thickener and base oil gradually degrade and become unusable. On the other hand, fluorine-based grease is not affected even in a corrosive environment.

When the rolling device is a rolling bearing, the formation of the Ni—W film or the rhodium film on the outer ring and the inner ring is performed in the same manner as the method of forming the Ni—W film or the rhodium film on the rolling device described above. good. The same applies to the masking method for the portion where the film is not formed.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. First, as a first embodiment, a case where the present invention is applied to a rolling bearing will be described.

For example, in a chemical pump for delivering a strong acid such as sulfuric acid or hydrochloric acid, the rolling bearing supporting the pump rotating shaft also needs to have a high acid resistance capable of withstanding a long continuous operation. In such a case, if a ceramic bearing is used, there is no problem in corrosion resistance, but it is very expensive.

In the rolling bearing according to the present invention, the surfaces of the inner and outer rings and the balls constituting the bearing are coated with a Ni-W coating or a rhodium coating. FIG. 1 is a partial sectional view of a single row deep groove ball bearing which is a first embodiment of the rolling device of the present invention,
A ball 3 as a rolling element is disposed between an outer ring 1 as an outer member and an inner ring 2 as an inner member, and is held by a retainer 4. The first contact surface that is the contact surface of the outer ring 1 with the ball 3 is the raceway surface 5 of the outer ring, and the second contact surface that is the contact surface of the inner ring 2 with the ball 3.
Is the raceway surface 6 of the inner ring. Each member of the outer ring 1, the inner ring 2, and the ball 3 is a bearing steel in the case of a Ni-W coating, and is a stainless steel or a bearing steel such as SUS440C in the case of a rhodium coating, and has a Ni-
The W film or the rhodium film is formed by using an electrolytic plating method. The Ni—W film has a tungsten atomic weight ratio of at least 35% by weight, and the outer ring 1, the inner ring 2 and the ball 3 are all formed with a thickness of 2 to 30 μm on the entire surface. In the case of a rhodium coating, the coating is similarly formed at 0.1 to 10 μm. The cage 4 is also covered with a Ni—W film or a rhodium film. In the case of a Ni-W coating, the Ni-W coating was formed with a thickness of 2 to 30 m, and the atomic weight ratio of tungsten in the Ni-W alloy was at least 35 wt%. In the case of a rhodium coating, the coating is formed at a thickness of 0.1 to 10 μm. Here, the tungsten atomic weight ratio in the Ni—W coating in the present invention is expressed as {W atomic weight / (Ni atomic weight + W atomic weight)}.
× 100% by weight.

When the corrosion-resistant ball bearing protected by the Ni—W coating or the rhodium coating is used for a chemical pump, it is excellent in contact with a strongly corrosive solution such as a strong acid such as sulfuric acid, nitric acid, especially hydrochloric acid, or a strong alkali. It shows excellent corrosion resistance. At the same time, the raceway surface 5 of the outer ring 1, which is the first contact surface,
The particularly wear-prone parts, such as the raceway surface 6 of the inner ring 2 and the surface of the ball 3, which are the contact surfaces of the inner ring 2, are protected by a high-hardness wear-resistant coating having excellent mechanical properties and frictional properties. Can be operated continuously. In addition, it is more cost effective than a ceramic bearing.

However, Ni is applied to the entire surface of each component of the bearing.
It does not always form a -W film or a rhodium film. For example, the coating on the entire surface of the Ni—W alloy or the rhodium coating may be limited to a member selected from the outer ring 1, the inner ring 2 and the ball 3, and the Ni—W coating or the rhodium coating is a specific part of the member, for example, the outer ring. The first raceway surface 5 and the inner raceway 2 may be limited to the raceway surface 6 and the like. Furthermore, only the ball 3 may be made of ceramics, and the outer ring 1 and the inner ring 2 provided with the Ni-W coating or the rhodium coating may be used in combination with another corrosion resistant material. Regarding the thickness of the Ni-W coating,
Within a range of 30 μm, and in the case of a rhodium film, it is 0.1 μm.
Within the range of 1 to 10 μm, it can be arbitrarily adjusted according to the use environment and required specifications of the bearing.

In the above-described embodiment, an open single-row deep groove ball bearing is exemplified as the bearing. However, the present invention can be similarly applied to a shield type, a rubber seal type, and the like, and can be applied to other types of ball bearings. The present invention can be applied not only to ball bearings but also to roller bearings.

Next, as a second embodiment, a case where the present invention is applied to a linear guide of a linear motion rolling bearing will be described. For example, in a linear guide for positioning and transferring a wafer mounted on a semiconductor manufacturing apparatus, H is used in a step of cleaning a wafer with hydrochloric acid or in a step of forming an Si oxide film by HCl oxidation.
A high degree of corrosion resistance that can withstand long-time continuous operation even in a corrosive atmosphere such as Cl and Cl ₂ is required. In these cases,
If ceramic is used for the material of the linear guide, there is no problem in corrosion resistance, but it is very expensive.

In the linear guide according to the present invention, the surfaces of the guide rail, the slider body, and the rolling elements, which are the constituent members, are coated with a Ni-W film or a rhodium film. FIG.
FIG. 5 is a front view of a small linear guide as a second embodiment of the rolling device according to the present invention, with a part cut away. A slider 12 having a U-shaped cross section as an outer member is straddled on a guide rail 11 which is an inner member having a substantially square cross section, and a number of balls 13 as rolling elements are provided between the two members. Are arranged. More specifically, a raceway groove 15 which is long in the axial direction is formed on both side surfaces of the guide rail 11, while the raceway groove 15 is formed on the inner side surface of the slider body 12 </ b> A which is a component of the slider.
Are formed, and a rolling element return path 17 composed of a through hole parallel to the raceway groove 16 is formed in the sleeve. At both ends of the slider body 12A, end caps 12B of the components of the slider are attached by screws 18, respectively. A semi-donut shape (not shown) for connecting the raceway groove 16 and the rolling element return path 17 to these end caps 12B. Is formed, and the raceway groove 1 is formed.
6, a circulation path of the rolling element 13 including the rolling element return path 17 and the curved path is configured. A large number of rolling elements 13 are loaded in the circulation path and held so as not to fall off.

In this case, the first contact surface, which is the contact surface of the outer member 12 with the rolling element 13, is the raceway groove 16 on the inner surface of the slider 12, and the inner member 11 contacts the rolling element 13. The second contact surface, which is a surface, is the raceway groove 15 on the outer surface of the guide rail 11.

The guide rail 11, the slider body 12A, and the rolling element 13, which are the components of the linear guide, are N
When an i-W coating is applied, it is made of a bearing steel, and in the case of a rhodium coating, it is made of a stainless steel such as SUS440C or a bearing steel, and a Ni-W coating or a rhodium coating is formed on their surfaces by electrolytic plating. Is formed. The Ni-W coating has a tungsten atomic weight ratio of at least 35% by weight, and the slider body 12A, the guide rail 11 and the ball 13 of the linear guide are each provided with a Ni-W coating having a thickness of 2 to 30 m on the entire surface. Is formed. As for the rhodium film, the slider body 12A of the linear guide, the guide rail 11, and the ball 13 are all coated with a rhodium film having a thickness of 0.1 to 10 μm. The end cap 12B is made of a synthetic resin having excellent acid resistance.

Thus, when the linear guide protected by the Ni—W coating or the rhodium coating of the present invention is used in a semiconductor manufacturing apparatus, it exhibits excellent corrosion resistance even in a highly corrosive atmosphere such as hydrochloric acid or chlorine gas. At the same time, particularly easily worn parts such as the raceway groove 16 of the slider 12 as the first contact surface, the raceway groove 15 of the guide rail 12 as the second contact surface, and the surface of the rolling element 13 have mechanical characteristics. And a high-hardness abrasion-resistant coating with excellent frictional properties enables long-term continuous operation. Moreover, since a normal steel material which is less expensive than ceramics can be used as a material for a linear guide used in a highly corrosive atmosphere, it is very advantageous in terms of cost.

In the above embodiment, the slider body 12A of the linear guide, the guide rail 11, and the ball 13
Although the i-W coating or the rhodium coating is formed, the coating is not limited to this. For example, the coating on the entire surface of the Ni-W alloy may include the guide rail 11, the slider body 12A, and the rolling element 1.
Alternatively, the Ni—W coating or the rhodium coating may be limited to a specific portion of the member, such as the raceway groove 15 of the guide rail 11 and the raceway groove 16 of the slider 12. Further, only the rolling elements 13 may be used in combination with other corrosion-resistant materials, such as made of ceramics. The thickness of the Ni-W coating is also 2-3.
0 μm, and for rhodium coatings, 0.1
Within the range of 10 μm to 10 μm, it can be arbitrarily adjusted according to the usage environment and required specifications of the linear guide.

The linear guide is not limited to the one described in the above embodiment, and the first linear guide may be provided on one side of the linear guide.
The contact surface 16 and the second contact surface 15 are both two or more, the roller is a roller, or the guide rail is a U-shaped cross section and the slider is inserted into the recess on the inner surface through the roller. The present invention can be similarly applied to a type that is movably disposed.

Next, as a third embodiment, a case where the present invention is applied to a ball screw will be described. For example, the ball screw used together with the linear guide for wafer transfer positioning in the semiconductor manufacturing apparatus described above has a high degree of corrosion resistance that can withstand continuous operation for a long time even in a corrosive atmosphere such as HCl and Cl _2. Will be required.

In the ball screw of the present invention, the surfaces of the screw shaft, nut and rolling elements made of a general steel material are made of Ni-W.
Coat with an alloy coating or rhodium coating. FIG. 2 is a cross-sectional view of a main part of a ball screw as a third embodiment of the rolling device of the present invention, in which a screw shaft 22 as an inner member having a helical screw groove 21 on an outer peripheral surface is connected to an outer member. Nut 2
3 is screwed through a rolling element 24 composed of a large number of balls. The nut 23 has a screw groove 25 on the inner peripheral surface corresponding to the screw groove 21 of the screw shaft 22. The rolling element 24 forms a spiral space formed by the two screw grooves 21 and 25 with the screw shaft 22.
While being rolled in the rotation direction, the nut 23 is guided to a ball circulation path (not shown) such as a circulating piece provided on the body of the nut 23 and circulates between both ends of the nut 23 in the axial direction.
When the screw shaft 22 rotates, the nut 23 is fed in a linear direction along the screw shaft 22 through the rolling of the rolling element 24.

In this case, the first contact surface where the outer member 23 contacts the rolling element 24 is the thread groove 25 of the nut 23, and the second contact surface where the inner member 22 contacts the rolling element 24. Is a thread groove 21 on the outer surface of the screw shaft.

The screw shaft 2 which is a component of the ball screw
Each member of the nut 1, the nut 23 and the rolling element 24 is made of bearing steel when a Ni-W coating is applied, and the Ni-W coating is formed on the surface thereof by electrolytic plating. The Ni-W coating has a tungsten atomic weight ratio of at least 35% by weight.
And a thickness of 2 to 3 on the surface of each component of the ball screw.
Each is formed at 0 μm. In the case of a rhodium film, it is made of bearing steel or stainless steel such as SUS440C, and has a thickness of 0.1 mm on the surface of each component of the ball screw.
Each is formed in a thickness of 1 to 10 μm.

Thus, when the ball screw protected by the Ni—W film or the rhodium film of the present invention is used in a semiconductor manufacturing apparatus, it exhibits excellent corrosion resistance even in a highly corrosive atmosphere such as hydrochloric acid or chlorine gas. At the same time, particularly easily worn parts such as the screw groove 21 of the screw shaft 22 as the first contact surface, the screw groove 25 of the nut 23 also as the second contact surface, and the surface of the rolling element 24 have mechanical characteristics. And a high-hardness abrasion-resistant coating with excellent frictional properties enables long-term continuous operation. In addition, since ordinary steel materials, which are less expensive than ceramics, can be used as the material for the ball screw used in a highly corrosive atmosphere, it is very advantageous in terms of cost.

In the above embodiment, the Ni-W film or the rhodium film is formed on the entire surface of each component of the ball screw. However, the present invention is not limited to this. For example, the Ni-W film or the rhodium film may be formed on the entire surface. May be limited to a member selected from the screw shaft 22, the nut 23, and the rolling element 24, and the Ni-W film or the rhodium film may be a specific portion of the member, such as the screw groove 21 of the screw shaft or the screw of the nut 23. It may be limited to the groove 25 or the like. Furthermore, only the rolling elements 24 may be used in combination with other corrosion-resistant materials, such as made of ceramics. The thickness of the Ni—W coating or the rhodium coating was 2 to 30 μm, respectively.
It can be arbitrarily adjusted within the range of 0.1 to 10 μm according to the use environment and required specifications of the bearing.

The ball screw is not limited to the ball screw of the above embodiment, but may be a tube circulating type using a circulating tube of a rolling element, an end cap circulating type having an end cap with a circulating path, or a screw lead. The present invention can be similarly applied to other types such as a large lead having a large lead.

(Embodiment) A rotation endurance test performed to confirm the effect of the rolling device of the present invention will be described below.

As the rolling device under test of the present invention, the deep groove ball bearing shown in FIG. 1, the linear guide shown in FIG.
In the ball screw shown in (1), only the slider body 12A is used for the slider 12, but the outer member, the inner member, and the entire surface of the rolling element are each coated with a Ni-W film having a thickness of 2 to 30.
One having a thickness of 35 μm and a tungsten atomic weight ratio of 35 to 50% was used.

On the other hand, as a rolling device under test of a comparative example,
A nickel-tungsten (Ni-W) alloy coating was used, but the thickness and the atomic weight ratio of tungsten were out of the range of the present invention, the coating was nickel-phosphorus, and the coating was chromium. Prepared. Also, Ni-W
A rhodium film instead of the alloy film was selected to have a coating thickness of 0.05 μm to 10 μm, and the following details were performed.

As the corrosive environment, a hydrochloric acid solution and a sodium hydroxide solution were set. The details of the durability test are as follows. Rotation endurance test (A) Corrosion environment: In hydrochloric acid (12 standard) solution Rolling device: Deep groove ball bearing (call number 608) Rotation speed: 60 rpm Temperature: 30 ° C Test time: 24 hours Rotation endurance test (B) Corrosion environment : In sodium hydroxide (10 normal) solution Rolling device: deep groove ball bearing (call number 608) Rotation speed: 60 rpm Temperature: 30 ° C Test time: 24 hours Rotation endurance test (C) Corrosion environment: hydrochloric acid (12 standard) Rolling device in solution: Linear guide (LH250535) Speed: 10 mm / s Temperature: 30 ° C Test time: 24 hours Rotation endurance test (D) Corrosion environment: Sodium hydroxide (10 normal) solution Rolling device: linear Guide (LH250535) Speed: 10 mm / s Temperature: 30 ° C Test time: 24 hours Rotation endurance test (E) Corrosion environment: In hydrochloric acid (12N) solution Rolling device: Bo Screw (W1503FA) Rotation speed: 60 rpm Temperature: 30 ° C Test time: 24 hours Rotation endurance test (F) Corrosion environment: In sodium hydroxide (10N) solution Rolling device: Ball screw (W1503FA) Rotation speed: 60 rpm Temperature Degree: 30 ° C. Test time: 24 hours The judgment after the test was as follows.

No change on the surface of the rolling device under test and smooth rotation: ○ No change on the surface of the rolling device under test, except that the rotation is so-called rubbing: △ Discoloration on the surface of the rolling device under test, and Rotation is a so-called gurgling: XX is judged to be acceptable.

Table 1 shows the test results of the rolling device of the present invention.

[0050]

[Table 1]

Table 2 shows the test results of the rolling device of the comparative example.
Shown in

[0052]

[Table 2]

In the case of the rolling device of the present invention, all passed hydrochloric acid and sodium hydroxide, and all exhibited excellent corrosion resistance. In all of the samples except for the sample No. 2, discoloration and rumbling were observed on the surface in terms of corrosion resistance to hydrochloric acid. Also, in Comparative Example 2, no discoloration of the surface was recognized, but rolling rumbling occurred.

That is, in Comparative Example 1, Ni-
Since the thickness of the W film was smaller than the lower limit of the present invention and was out of the range of the present invention, and the film thickness was too small, all the specimens passed the corrosion resistance to sodium hydroxide, but did not pass the 12N hydrochloric acid. Rejection occurred due to surface discoloration and rumbling.

In Comparative Example 2, the thickness of the Ni—W coating was larger than the upper limit of the present invention and was out of the range of the present invention, and no corrosion was observed for sodium hydroxide and hydrochloric acid. In addition, the rolling device, in which the rolling element rolls while contacting the first contact surface and the second contact surface due to the excessive film thickness, was rejected due to generation of a rolling rub.

In Comparative Example 3, the tungsten atomic weight ratio of the Ni—W coating was lower than the lower limit of the present invention, and the nickel was excessive, and in particular, the corrosion resistance to hydrochloric acid was insufficient, and the test was rejected. In Comparative Example 4, the coating was a conventional nickel-phosphorus, and the coating was dissolved in hydrochloric acid, and discoloration of the surface and rolling rubbing occurred, resulting in a failure.

In Comparative Example 5, the coating was conventional chromium, and as in Comparative Example 4, the coating was dissolved in hydrochloric acid, causing surface discoloration and rolling rubbing, and was rejected. Next, a description will be given of a corrosion resistance test, an endurance test and a bearing manufacturing cost in which the present invention is applied to various rolling bearings as rolling devices to be tested, in comparison with comparative examples. (1) Corrosion Resistance Test and Judgment of Bearing Manufacturing Cost For the test bearing, 608 was used as a deep groove ball bearing, FJ-810 was used as a needle bearing, and NU204 was used as a cylindrical roller bearing. These bearings to be tested were immersed in a corrosive solution at room temperature for 24 hours, and then the state of corrosion of the surface of the bearing to be tested was observed. In the judgment, the following four ranks were evaluated for corrosivity, and three ranks were evaluated for cost. Any of hydrochloric acid, hydrofluoric acid, sulfuric acid and sodium hydroxide was used as the corrosive solution.

(A) Judgment Criteria for Corrosion Test Results No Corrosion: 0 Slightly Corrosion: 1 Moderate Corrosion: 3 Large Corrosion: 5 (b) Judgment Criteria for Bearing Manufacturing Cost Small Cost: Good Cost: △ High cost: × Deep groove ball bearings (outer ring and inner ring are made of 440C stainless steel, rolling elements are made of silicon nitride or silicon carbide or zirconia.
Table 3 shows the conditions and results of a test performed using a retainer made of fluororesin.

[0059]

[Table 3]

The deep groove ball bearings of the present invention (Examples 1 to 4) in which the outer and inner races were each provided with a Ni-W coating were left stainless steel without applying the Ni-W coating on the outer and inner races. The corrosion resistance is superior to those of Comparative Example 1, Comparative Example 2 in which a Ni-P coating is applied to the surface of the outer and inner rings, and Comparative Example 3 in which a chromium coating is applied. (2) Bearing durability test As the bearing to be tested, a deep groove ball bearing (608) having an inner diameter of 8 mm and a needle bearing (FJ-81) were used as in the corrosion resistance test.
0) and a cylindrical roller bearing (NU204).
The outer and inner races of each bearing are made of 440C stainless steel and have a surface coated with a Ni-W coating within the scope of the present invention. The rolling elements are made of ceramics or have a surface coated with a Ni-W coating. Or it is made of nylon resin. These bearings to be tested are subjected to a constant radial load in a 6N hydrochloric acid vapor atmosphere, and in a non-lubricated state (only using the lubricating property of the cage), a rotational speed of 600 rpm until the bearing torque increases. To perform a durability test.

Table 4 shows the test conditions and results.

[0062]

[Table 4]

Table 4 shows that the rolling bearings of the present invention were used in Examples 5, 6, 7, 8, and 9 (the rolling elements were made of ceramics or Ni-W coated on the surface and the cage was made of fluororesin). In the case of (), the life is long because of the transfer film formed by transferring the fluororesin of the cage to the race surfaces of the outer ring and the inner ring and the surface of the rolling element. On the other hand, in Comparative Examples 4 and 5 in which the cage was not made of a fluororesin (made of a nylon resin), the durability life was remarkably shortened. That is, the Ni-W of the present invention
By combining a fluororesin cage with the outer and inner races having the coating, the rolling life can be extended even in a corrosive environment. (3) Effect of fluorine grease on bearing durability For the various types of rolling bearings of the same type as the bearing durability test,
A Ni-W coating is applied to the surfaces of the outer and inner races and the rolling elements, and the cage is made of a fluororesin (Examples 10, 11, and 12) or a steel cage is coated with a Ni-W coating of the same conditions as the outer and inner races. The difference in bearing durability, corrosion resistance, and cost between the case where the grease was applied (Example 13) and the case where the grease was filled with fluorine grease and the case where the grease was filled were compared and verified. The conditions of the durability test are the same as those of the bearing durability test.

Table 5 shows the conditions and results of the test.

[0065]

[Table 5]

In Table 5, Examples 10, 11, and 1 in which the rolling bearing of the present invention is filled with fluorine grease are shown.
2 and 13 (the thickness of the Ni—W coating and the value of the tungsten atomic weight ratio are different within the scope of the present invention), all show life values equal to or more than the endurance load shown in Table 4 above. On the other hand, Comparative Examples 6 to 9 in which the value of the thickness of the Ni—W coating or the atomic weight ratio of tungsten is not within the range of the present invention or the grease is not a fluorine grease,
Either the durability life and the corrosion resistance are poor or the cost is high. That is, the rolling bearing in which the Ni-W coating of the present invention is applied, the retainer is made of a fluororesin, and fluorine grease is sealed as a lubricant is excellent in all of the durability life, corrosion resistance and cost.

Next, the effect of the Ni—W coating on the degree of corrosion will be discussed. FIG. 4 shows the criteria (0 to 5) for the results of the corrosion test described in the above “(1) Corrosion resistance test”.
The relationship between the thickness of the Ni—W coating and the degree of corrosion resistance of the bearing is obtained and shown in FIG. As the bearing to be tested, a deep groove ball bearing 608 was used, and Ni-W coatings of various thicknesses were applied to the inner ring and the outer ring, and the tungsten atomic weight ratio in the coating was 40% by weight. The rolling elements are silicon nitride, and the retainer is a fluororesin. The corrosion conditions were immersed in a 6N hydrochloric acid solution for 24 hours, and the degree of corrosion was determined by observing the corrosion state of the surface of the bearing to be tested thereafter.

As is apparent from FIG. 4, when the Ni—W coating thickness is less than 2 μm, the inner ring and the outer ring are corroded by the influence of the pinhole. With a Ni-W coating having a thickness of 2 m or more, the bearing is not corroded due to the corrosion resistance of the Ni-W coating.

FIG. 5 shows the relationship between the atomic weight ratio of tungsten in the Ni—W coating and the degree of corrosion resistance of the bearing. The conditions and the corrosion conditions of the bearing under test were the same as when the relationship of FIG. 4 was obtained. At this time, the thickness of the Ni-W coating applied to the outer and inner rings was fixed at 5 μm.

As is apparent from FIG. 5, when the atomic weight ratio of tungsten in the Ni—W coating applied to the outer and inner rings is less than 35% by weight, the coating is less likely to become completely amorphous, so that the corrosion resistance is not improved. The bearing under test is corroded. But,
When the tungsten atomic weight ratio of the coating was 35% by weight or more, the Ni—W coating became amorphous and the bearing was not corroded. The test was stopped up to the limit value of 50% by weight of the state of the art, but it can be clearly inferred that even if it exceeds 50% by weight, good corrosion resistance is obtained.

Based on the results of FIGS. 4 and 5, the relationship between the corrosion resistance, the Ni—W coating thickness (μm), and the tungsten atomic weight ratio in the coating is summarized in FIG.
That is, it was confirmed that, in the range of the Ni—W coating thickness of 2 to 30 μm, the range of the present invention having a tungsten atomic weight ratio of 35% by weight or more in the coating film has good corrosion resistance.

Hereinafter, examples of the rhodium film will be described. (1) Corrosion resistance test A rolling bearing 6000 (both outer and inner rings made of SUS440C) as a rolling device was used as a test object. Examples 1 to 4 were obtained by coating the outer ring and the inner ring of the test object with a rhodium film having a thickness of 1.0 μm. On the other hand, the outer ring and the inner ring were made of stainless steel and the coating was not applied in Comparative Example 1, the surface was coated with a 10 μm-thick Ni—P coating in Comparative Example 2, and the chrome coating was compared. Example 3 was used. These test pieces were immersed in various corrosion solutions (see Table 6) at room temperature for 24 hours, and then the corrosion state of the test piece surface was observed and judged according to the following criteria.

Corrosion judgment criteria: No corrosion: 0 Slight corrosion: 1 Medium corrosion: 3 Large corrosion: 5 The results of the corrosion test are shown in Table 6.

[0074]

[Table 6]

Examples 1 to 4 had corrosion resistance to various corrosion solutions. On the other hand, the corrosion-free coatings of Comparative Examples 1 to 3 or the conventional corrosion-resistant coatings were corroded by 6N hydrochloric acid. FIG.
It is the figure which plotted the influence of the thickness of the rhodium film on the degree of corrosion. As in the corrosion resistance test, the rolling bearing 6000 was used as a test object, and its outer ring and inner ring (SU
S440C) with rhodium coatings of various thicknesses were applied to various corrosion solutions (12N hydrochloric acid, 1N hydrofluoric acid, 6N
After immersion in sulfuric acid, 10N sodium hydroxide) for 24 hours, the corrosion state of the outer ring and the inner ring was determined according to the above-mentioned criteria. Corrosion does not occur in any case where the rhodium coating has a thickness in the range of 0.1 to 10 μm. On the other hand, if the thickness is less than 0.1 μm or if there is no coating, large corrosion occurs.

Although the above-described evaluation of the corrosion resistance was performed on a rolling bearing, it goes without saying that the same result can be obtained with other rolling devices such as a linear guide and a ball screw. (2) Rotation endurance test and cost evaluation Next, a rotation endurance test and a cost evaluation under a corrosive environment performed on various rolling devices provided with a rhodium film will be described.

As a rolling device for the test object, a deep groove ball bearing,
Using a linear guide and a ball screw, rhodium films having various thicknesses were formed on the entire surface of the outer member, the inner member, and the rolling elements, respectively. On the other hand, as a rolling device under test of a comparative example, a rhodium coating having a thickness outside the range of the present invention, a nickel-phosphorus coating, and a chromium coating were prepared. 12N as corrosive environment
A hydrochloric acid solution and a 10N sodium hydroxide solution were set.

The details of the durability test and the judgment criteria after the test are based on the above-mentioned rotational durability test (A) of the Ni—W coating.
This is the same as the case of (F). In addition, the cost was evaluated in the same manner as the evaluation of the Ni—W coating.

Table 7 shows the test results of the rolling device of the present invention, and Table 8 shows the test results of the rolling device of the comparative example.

[0080]

[Table 7]

[0081]

[Table 8]

In the case of the rolling device of the present invention, all passed hydrochloric acid and sodium hydroxide, indicating excellent corrosion resistance. In all of the samples except for the sample No. 5, discoloration and rumbling were observed on the surface in terms of corrosion resistance to hydrochloric acid.

That is, in Comparative Example 4, the thickness of the rhodium film, which is a corrosion-resistant film, was smaller than the lower limit of the present invention and was out of the range of the present invention. Although the corrosion resistance was acceptable, it was rejected for 12N hydrochloric acid due to surface discoloration and rolling rubbing.

In Comparative Example 5, the thickness of the rhodium film was larger than the upper limit of the present invention and was out of the range of the present invention, and no corrosion was observed for both sodium hydroxide and hydrochloric acid. In addition, the cost for polishing the inner ring groove was increased. In addition, when the grooves were not reworked, wear was caused early due to poor accuracy.

In Comparative Example 6, the coating was a conventional nickel-phosphorus, and the coating was dissolved in hydrochloric acid, and discoloration of the surface and rolling ruggedness occurred. In Comparative Example 7, the coating was a conventional chromium, and as in Comparative Example 6, the coating was dissolved in hydrochloric acid, causing surface discoloration and rolling rubbing, and was rejected.

[0086]

As described above, according to the present invention,
By forming a nickel-tungsten alloy coating or rhodium coating having excellent resistance to acid and alkali and high hardness and abrasion resistance, it can be used even in a severe environment where a strong acid is present, especially in a hydrochloric acid environment. It is possible to obtain a highly reliable corrosion-resistant and long-life rolling device and rolling bearing.

By limiting the thickness of the nickel-tungsten alloy coating or rhodium coating to a range of 2 to 30 μm or 0.1 to 10 μm, pinholes due to an insufficient film thickness can be eliminated, and Corrosion of metal can be completely prevented, and dimensional accuracy does not decrease due to excessive film thickness. Therefore, it is not necessary to rework for ensuring accuracy, and manufacturing cost can be reduced.

Since the atomic weight ratio of tungsten in the nickel-tungsten alloy coating is set to at least 35% by weight, it can be formed into an amorphous coating to improve the corrosion resistance and also prevent the reduction of the strong acid corrosion resistance due to the excessive nickel component. In particular, it is possible to provide a long-life corrosion-resistant rolling device exhibiting a stable function in a hydrochloric acid environment.

In the rolling bearing, since the rolling element is made of silicon nitride, silicon carbide, or zirconia, the inner ring or the outer ring is made of a different metal, so that it is less likely to be worn and the life can be improved. Also, by using the fluororesin cage, the fluororesin contributes as a solid lubricant even in a corrosive environment, and the life can be improved. Furthermore, by enclosing the corrosion resistant grease, the durability of the bearing can be improved, and the reliability of the bearing life can be increased. Thus, the present invention can provide a long-life, corrosion-resistant rolling bearing that exhibits a stable function in a corrosive environment, particularly in a hydrochloric acid environment.

[Brief description of the drawings]

FIG. 1 is a partial sectional view of a rolling device according to a first embodiment of the present invention.

FIG. 2 is a front view of a rolling device according to a second embodiment of the present invention, with a portion cut away.

FIG. 3 is a sectional view of a main part of a third embodiment of the rolling device of the present invention.

FIG. 4 is a diagram showing the relationship between the degree of corrosion and the thickness of a Ni—W coating.

FIG. 5 is a diagram showing the relationship between the degree of corrosion and the atomic weight ratio of tungsten in a Ni—W coating.

FIG. 6 is a diagram showing the thickness of the Ni—W coating and the range of the tungsten atomic weight ratio of the coating in the present invention.

FIG. 7 is a diagram showing the relationship between the rhodium coating thickness and the degree of corrosion in the present invention.

[Explanation of symbols]

 Reference Signs List 1 outer member (outer ring) 2 inner member (inner ring) 3 rolling element (ball) 5 first contact surface 6 second contact surface 11 inner member (guide rail) 12 outer member (slider) 13 rolling element 15 second contact surface 16 first contact surface 21 second contact surface 22 inner member (screw shaft) 23 outer member (nut) 24 rolling element 25 first contact surface

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F16C 33/62 F16C 33/62

Claims (1)

[Claims] 1. A rolling element is provided between an outer member and an inner member, wherein the rolling element is a first surface which is a contact surface of the outer member with the rolling element.
And a second contact surface that is a contact surface of the inner member with the rolling element, wherein the rolling member and the first contact surface and the second contact surface At least one of them is coated with a nickel-tungsten alloy
A rolling device formed with a thickness of [mu] m and having a tungsten atomic weight ratio of the nickel-tungsten alloy of at least 35% by weight.