JPH07180028A - Corrosion resistance structure of rolling element - Google Patents

Abstract

PURPOSE:To improve the corrosion resistance of a rolling element. CONSTITUTION:A corrosion resistant film 2b is constituted of a chromium plating layer 2b1 covering the outer diameter face of an outer ring 2 and an ion plating layer 2b2 covering the surface of the plating layer 2b1. The plating layer 2b1 is obtd. by subjecting the outer diameter face of the outer ring 2 to coating treatment with chromium by about 5 to 10mum by electrolytic plating or the like. The ion plating layer 2b2 is obtd. by subjecting the surface of the plating layer 2b1 with chromium to about 0.2mum by ion plating. The ion plating layer 2b2 is infiltrated into the depths of the pinhole P of the plating layer 2b1, covers the surface of the base metal and protects the same.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to means for ensuring corrosion resistance in general rolling elements such as bearing components.

[0002]

2. Description of the Related Art For example, in a semiconductor etching process or a CVD (chemical vapor deposition) process, since a reactive gas such as a silane type, a fluorine type or a chlorine type is used, corrosion of parts or the like incorporated in the apparatus is prevented. Is a problem. In particular, in rolling elements such as bearing components, if corrosion occurs on the surface that causes rolling friction (raceway surface, rolling surface of rolling elements, etc.), it will lead to deterioration of function and durability, so corrosion prevention measures are extremely important. Becomes important. The level of corrosive atmosphere is different even in the same equipment, and it can be dealt with by using a high nickel alloy when it is placed in a place with a high corrosive atmosphere level, or with a place with a relatively low corrosive atmosphere level. In the case of being arranged at, it can be dealt with by using martensitic stainless steel or the like.

By the way, even in the same part, there is naturally a difference in how corrosion occurs between the part exposed in the atmosphere and the part not exposed in the atmosphere, and even if the corrosive atmosphere level is relatively low, Corrosion easily progresses in the part exposed in the atmosphere. For example, if the bearing is used as a wheel of a carriage (such as a cam follower),
Since the outer diameter surface of the outer ring runs while rolling on the guide rails and the like, there is a possibility that it will come into direct contact with corrosive substances in the atmosphere, and corrosion is most likely to occur.

For the above reasons, conventionally, when a rolling element is used in a place where the level of corrosive atmosphere is relatively low, it is formed of martensitic stainless steel, and the most corrosive surface out of rolling friction is used. In the above example, the exposed surface, which is apt to occur, is plated with chromium on the outer diameter surface of the outer ring to improve the corrosion resistance.

[0005]

The chromium coating layer has excellent corrosion resistance and wear resistance, and even when a relatively thick coating layer of about 5 to 10 μm is formed in order to secure sufficient corrosion resistance. The advantage is that the plating process can be performed in a short time. However, as shown enlarged in FIG.
There is a problem that the pinhole P is generated in b, and this has been a factor causing rusting A to occur on the surface of the base material 12 at an early stage. This is because the base material 12 is not covered with the pinhole P, so that the base material 12 is directly attacked by the corrosive substance that has entered through the pinhole P and the base material metal ( Galvanic corrosion (a phenomenon in which a local battery is formed due to the adhesion of water and an electric current flows to cause corrosion) between the iron-based) and the plated layer 12b (chromium), and the corrosion of the base material 12 is accelerated. Because. Such a chromium plating layer 12b
Since the pinhole P in the above is inevitable even when the film thickness is made relatively thick, after all, after all, the plated layer 12b
It cannot be said that the formation of the above is not sufficient as a means for ensuring corrosion resistance.

On the other hand, as a chromium coating method, a plating method as a wet method and an ion plating method as a dry method can be considered. According to this method, a coating layer excellent in denseness and adhesion is formed. Therefore, the problem caused by the pinhole is avoided. However, in order to secure sufficient corrosion resistance, it is necessary to make the film thickness relatively thick, and it is attempted to achieve this only by ion plating. It takes a lot of time, poor workability, and high cost. .

Therefore, an object of the present invention is to solve the problems caused by the occurrence of pinholes in the chromium plating layer and to provide a rolling element having good corrosion resistance and durability in a corrosive atmosphere.

[0008]

The corrosion resistant structure of the present invention comprises a corrosion resistant coating formed of chromium or a metal material containing chromium as a main component on the surface of a rolling element which causes rolling friction. However, it has a plating layer covering the surface of the base material and an ion plating layer formed on the plating layer.

Further, among the surfaces of the rolling element which cause rolling friction, the above corrosion-resistant coating is formed on the surface exposed in the atmosphere, and the lubricating coating made of PTFE is formed on the surface not exposed in the atmosphere. .

Further, a lubricating coating made of PTFE is formed on the upper surface of the corrosion resistant coating.

[0011]

[Function] The ion plating layer has excellent denseness and adhesion, and covers the surface of the plating layer without unevenness. There are pinholes in the chrome plating layer, which causes early corrosion of the base metal.In this corrosion resistant coating, the ion plating layer penetrates deep into the pinholes in the plating layer. By covering and protecting the base metal surface, the problem of base metal corrosion in pinholes is eliminated. For the parts other than the pinholes, the plating layer covers the surface of the base material and effectively protects the surface of the base material from the corrosive atmosphere. At the same time, since the ion plating layer covers the surface of the plating layer and functions as a kind of barrier layer for the plating layer, a good corrosion resistance effect of the plating layer is maintained for a long time.

Of the surfaces that cause rolling friction of the rolling element, the above corrosion resistant coating is formed on the surface exposed to the atmosphere,
By forming a lubricating coating made of PTFE on the surface that is not exposed to the atmosphere, it becomes possible to use it in a vacuum. Generally, layered substances such as molybdenum disulfide, soft metals such as gold, silver and lead, solid lubricants such as polymer materials such as PTFE and polyimide are often used for lubricating rolling elements in vacuum. However, among these, the layered material and the soft metal are easily attacked by the reactive gas, and are not suitable for use in a corrosive atmosphere. On the other hand, PTFE is a chemically stable substance and is relatively unlikely to be attacked by reactive gas. Therefore, the lubricating coating made of PTFE has a good lubricating effect on the surface that causes rolling friction, and at the same time has an effect of protecting the base material surface from reactive gas and the like. Corrosion is relatively unlikely to occur in the portion that is not exposed to the atmosphere, so that a sufficient lubricating resistance effect can be expected with the PTFE lubricating coating.

When wear deterioration due to rolling friction of the corrosion resistant coating is expected, this can be prevented by forming a PTFE lubricating coating on the upper layer of the corrosion resistant coating.

[0014]

EXAMPLES Examples in which the present invention is applied to a cam follower will be described below.

The cam follower shown in FIG. 1 is suitable for use in vacuum equipment such as etching processing equipment and CVD processing equipment in semiconductor manufacturing equipment. This cam follower has a stud 1 with a raceway on the outer circumference of the head,
The main elements are an outer ring 2 having a raceway surface formed on the inner circumference, a plurality of rollers 3 interposed between the raceways of the stud 1 and the outer rings 1, 2 and a cage 4 for holding the rollers 3 at equal intervals around the circumference. Is configured as. A threaded portion 1a is formed at an end of the stud 1 so that the stud 1 can be attached by being fastened to a threaded hole of a mating member. The cage 4 includes a flange portion 1b formed at the end of the stud 1 and the stud 1
The ring-shaped side plates 5 are press-fitted into and are prevented from coming out from both sides in the axial direction.

In this embodiment, in the cam follower as described above, of the rolling elements, that is, the stud 1, the outer ring 2 and the roller 3 which generate rolling friction, the outer diameter surface of the outer ring 2 exposed to the atmosphere (the opposite surface, for example, (Rotating on the guide rail) is formed with a corrosion resistant coating 2b made of chromium, and the stud 1 raceway surface, the outer race 2 raceway surface, and the rolling surface of the rollers 3 which are not exposed to the atmosphere are crystalline. PT
The lubricating coatings 1a, 2a and 3a made of FE are formed. Further, in this embodiment, at least the outer ring of the rolling element is formed of martensitic stainless steel represented by SUS440C.

As shown enlarged in FIG. 3, the corrosion-resistant coating 2b
Is a chrome plating layer 2b1 covering the outer diameter surface of the outer ring 2,
Ion plating layer 2 covering the surface of the plated layer 2b1
and b2. The plating layer 2b1 is formed by coating the outer diameter surface of the outer ring 2 with chrome by electrolytic plating or the like for about 5 to 10 μm. According to the plating method, the coating process can be performed in a short time even with a relatively thick coating layer of this degree. Ion plating layer 2
In b2, the surface of the plated layer 2b1 is coated with chromium by ion plating to a thickness of about 0.2 μm. Such an ion plating layer 2b2 is excellent in denseness and adhesion, and covers the surface of the plating layer 2b1 evenly. Ion plating layer 2b2 is 0.2 μm
It is a thin film and can be processed in a relatively short time.
Further, since the plating layer 2b1 as the base is made of the same kind of metal, the affinity at the layer boundary is high and the adhesion is particularly good.

As described above, the chromium plating layer 2b1
Has a pinhole P, which causes early corrosion of the base material. In the corrosion-resistant coating 2b, the ion plating layer 2b2 penetrates deep into the pinhole P of the plated layer 2b1. Since the surface of the base material is covered with and protected by the above, the problem of base material corrosion in the pinhole P is solved. For the parts other than the pinhole P, the plating layer 2
b1 thickly covers the surface of the base material and effectively protects the surface of the base material from a corrosive atmosphere. At the same time, the ion plating layer 2b2 covers the surface of the plating layer 2b1, and the plating layer 2b1
Since it functions as a kind of barrier layer against the above, the good corrosion resistance effect of the plated layer 2b1 is maintained for a long time.

In the above description, the "lubricating film made of crystalline PTFE" refers to a so-called sputtered film in which the crystal structure (molecular structure) of PTFE is not subdivided. For example, a processing solution of PTFE is used. It can be formed by spraying the object to be treated or by immersing the object to be treated in the treatment liquid. Such lubricating coatings 1a, 2a, 3a exhibit the original excellent lubricating performance of PTFE and enhance the durability of the rolling element. At the same time, since PTFE itself is a substance having excellent corrosion resistance, it protects the surface of the rolling element from corrosive substances. As described above, in a semiconductor etching process, etc., a reactive gas such as chlorine is used, but the reactive gas does not attack the base material by itself, and bonds with moisture in the atmosphere to form an acid. Only by forming, the surface of the base material is corroded. Therefore, in a portion where the corrosive atmosphere level is relatively low, corrosion is relatively unlikely to occur in the portion not exposed in the atmosphere, and therefore the PTFE lubricating coatings 1a, 2a, 3
With a, a sufficient corrosion resistance effect can be expected.
Incidentally, in this embodiment, as shown in FIG.
a, 2a, and 3a have a continuous island-like distribution. The lubricating film having a continuous island distribution is, for example, a product obtained by spraying a treatment liquid of PTFE onto an object to be treated and attaching it in an island shape, and then eluting it with an organic solvent to make the islands continuous, in particular, There is an advantage that the amount of dust generation can be reduced (For details, see Japanese Patent Application No. 4-2035 filed by the present applicant.
67). In addition, when abrasion deterioration due to rolling friction of the corrosion resistant coating 2b is expected, a lubricating coating made of crystalline PTFE may be further formed on the corrosion resistant coating 2b.

FIG. 2 shows the result of a comparative corrosion resistance test conducted on a rolling element having the corrosion resistant coating 2b having the above-mentioned structure formed on the surface thereof. The comparison test was conducted by a salt spray test (sodium chloride concentration 5%, spray amount 1-2 ml / h, test temperature 35 ° C). The upper column of the same figure shows the one in which the corrosion resistant coating 2b (Cr plating + Cr ion plating) as shown in FIG. 3 is formed, the middle column shows that only the Cr plated layer 12b as shown in FIG. 4 is formed, and the lower column shows the figure. 5 is a result of forming the Cr plating layer 12b1 on the Cr ion plating layer 12b2 as shown in FIG.
Rust formation was observed after 290 hours when only the Cr plating layer was formed (Fig. 4), whereas rust formation was observed after 900 hours when the corrosion resistant coating 2b was formed (Fig. 3). There wasn't. Incidentally, in the case where the Cr plating layer was formed on the Cr ion plating layer (FIG. 5), rust was observed in 170 hours, and the corrosion resistance was inferior to the case where only the Cr plating layer was formed (FIG. 4). . It is considered that this is because the Cr ion plating layer 12b2 is easily damaged during the treatment of the Cr plating layer 12b1.

The material for forming the corrosion resistant layer 2b is not limited to chromium, but chromium alloys, chromium and carbon, nitrogen, phosphorus, sulfur,
It can be selected from compounds or co-folds with oxygen, fluorine and the like.

The present invention is not limited to the above-mentioned cam followers, but can be applied to, for example, wafer chucking jigs in semiconductor manufacturing equipment, corrosive gas jetting parts, and rolling elements in gate valves in general.

[0023]

The present invention has the following effects.

(1) Since the ion plating layer of the corrosion-resistant coating penetrates deep inside the pinhole of the plating layer to cover the surface of the base material and protect it, the problem of base material corrosion in the pinhole is solved. Further, with respect to the portions other than the pinholes, the plating layer covers the surface of the base material and effectively protects the surface of the base material from a corrosive atmosphere. At the same time, since the ion plating layer covers the surface of the plating layer and functions as a kind of barrier layer for the plating layer, a good corrosion resistance effect of the plating layer is maintained for a long time.

(2) Even if the ion plating layer is a relatively thin film, a sufficient corrosion resistance effect can be obtained, so that the treatment time is extremely short compared with the case where a thick coating layer is formed only by ion plating. Is enough.

(3) By forming the above corrosion-resistant coating on the surface exposed to the atmosphere in the rolling friction of the rolling element and forming the lubricating coating made of PTFE on the surface not exposed to the atmosphere. It can be used in vacuum.

(4) The lubricating coating made of PTFE has a good lubricating effect on the surface that causes rolling friction, and at the same time protects the base material surface from reactive gas. Corrosion is relatively unlikely to occur in the portion that is not exposed to the atmosphere, so that a sufficient lubricating resistance effect can be expected with the PTFE lubricating coating.

(5) When wear deterioration due to rolling friction of the corrosion resistant coating is expected, this can be prevented by forming a PTFE lubricating coating on the corrosion resistant coating.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a diagram showing the results of a corrosion resistance comparison test.

FIG. 3 is an enlarged sectional view schematically showing a corrosion resistant coating.

FIG. 4 is an enlarged cross-sectional view schematically showing a chromium plating layer.

FIG. 5 is an enlarged cross-sectional view schematically showing a case where a chromium plating layer is formed on the chromium ion plating layer.

FIG. 6 is an enlarged sectional view schematically showing a lubricating film of PTFE.

[Explanation of symbols]

 2b Corrosion resistant coating 2b1 Plating layer 2b2 Ion plating layer 1a Lubricating coating 2a Lubricating coating 3a Lubricating coating

Claims (3)

[Claims] 1. A corrosion resistant coating made of chromium or a metal material containing chromium as a main component is formed on a surface of a rolling element that causes rolling friction, and the corrosion resistant coating covers a surface of a base material. A corrosion-resistant structure for a rolling element, comprising an ion plating layer formed on the plating layer. 2. The corrosion resistant coating of claim 1 is formed on the surface exposed to the atmosphere in the rolling friction of the rolling element, and the lubricating coating made of PTFE is formed on the surface not exposed to the atmosphere. Corrosion resistant structure of rolling elements characterized by 3. The corrosion resistant structure for a rolling element according to claim 2, wherein a lubricating film made of PTFE is formed on an upper layer of the corrosion resistant film.