WO2015058759A1

WO2015058759A1 - Rolling bearing ring

Info

Publication number: WO2015058759A1
Application number: PCT/DE2014/200523
Authority: WO
Inventors: Wolfgang Braun; Vasilios Bakolas; Peter Schuster
Original assignee: Schaeffler Technologies AG & Co. KG
Priority date: 2013-10-25
Filing date: 2014-09-30
Publication date: 2015-04-30
Also published as: DE102013221687A1

Abstract

A rolling bearing ring (1) has a main part (2) that is coated with a nickel-titanium alloy coating (3) on which a raceway (4) is formed. The rolling bearing ring (1) provided with said coating (3) is advantageous over an uncoated steel rolling bearing ring both with respect to the elastic compliance of the raceway (4) and with respect to corrosion protection.

Description

Name of the invention

Rolling bearing ring Description

Field of the invention

The invention relates to a rolling bearing ring, which has a coated raceway for rolling elements, that is to say a coating in the region of the rolling contact.

BACKGROUND OF THE INVENTION A roller bearing ring with a coated raceway is known, for example, from DE 10 201 1075 497 A1. In addition to the coating of the raceway, a further coating in a surface section of the bearing ring provided for receiving a seal is provided in this case, which improves the resistance to aggressive media as a special coating.

Further examples of coated bearing rings are disclosed in DE 10 2010 015 155 A1 and in DE 10 2007 042 372 A1. In these bearing rings different coatings are used for electrical insulation or to prevent fretting corrosion. The coatings are in both cases in surface areas of the bearing rings outside of the rolling contact.

From DE 10 201 1 080 132 A1 discloses a rolling bearing is known, which is particularly intended for use at higher temperatures. At least one of the two bearing rings of this rolling bearing has a phosphating, in particular a manganese phosphating on. In addition, the rolling elements can also have a coating, for example a chrome plating or an oxide-ceramic coating. In order to design a rolling bearing for special operating conditions, for example high temperatures or use in aggressive media, uncoated components made of suitable metallic or non-metallic materials can be used instead of coated components. For example, it is possible to combine in a roller bearing bearing rings made of plastic with rolling elements made of glass. Conventional hybrid bearings have ceramic rolling elements and steel bearing rings, for example corrosion-resistant steel. With the same dimensions as a conventional rolling bearing made of pure steel components, however, a hybrid bearing on an increased pressure, since the modulus of elasticity of commonly used ceramic materials such as silicon nitride is significantly higher than the modulus of elasticity of conventional rolling bearing steels. An advantage of the material combination ceramic-steel, however, lies in a lower adhesion tendency compared to the steel-steel material pairing. For this reason, hybrid bearings are particularly suitable for applications under unfavorable lubrication conditions.

OBJECT OF THE INVENTION The object of the invention is to further develop a roller bearing in relation to the cited prior art, in particular with regard to the possible applications under unfavorable environmental conditions.

Description of the invention

This object is achieved by a rolling bearing ring with the features of claim 1. This rolling bearing ring has a coating made of a nickel-titanium alloy in the region of its race intended for contacting rolling elements. The rolling bearing ring is particularly suitable for use in a lack-lubricated, in particular water-lubricated, for example seawater lubricated, rolling bearing. The rolling elements, in particular balls, of a bearing ring according to the invention having rolling bearing are made according to a possible embodiment of a ceramic material.

Compared to a ceramic material as a material of a bearing ring, the nickel-titanium alloy has the advantage of a much lower modulus of elasticity, that is, a higher elastic compliance. As a result, a larger surface portion for power transmission between the bearing ring and a rolling element, such as a ball, used, which is synonymous with a reduced contact pressure. At the same time nickel-titanium alloys are characterized by a high corrosion resistance. Depending on the application and base material of the bearing ring and the non-magnetic properties of nickel-titanium alloys may be beneficial. The coating has, according to an advantageous embodiment, a nickel content of more than 50%. Percentages of the coating are always to be understood as percent by weight. Nitinol 60 (60% Ni, 40% Ti) is preferably used as the nickel-titanium alloy. It is a material with shape memory properties. The surface hardness of this material is in a preferred embodiment of the rolling bearing ring at least 58 HRC. A surface hardness up to 62 HRC is achievable. The coated rolling bearing ring can be subjected to a heat treatment to increase its hardness. According to a first possible design of the rolling bearing ring, the nickel-titanium alloy is applied in the form of a metal strip on the base material of the bearing ring. This can be done in the form of a press-fitting of a thin ring of nickel-titanium alloy in a steel body. According to a second possible design, the nickel-titanium coating is a metal layer formed by powder metallurgy. The production of such a layer can be effected, for example, by sintering powder metallurgical nitinol (ΝΓΠ60) onto a steel base body. As an alternative gierungsverfahren is a metal powder injection molding into consideration, with which a near-net shape shaping on a steel base body is possible. According to another possible manufacturing method, pre-alloyed Ni-Ti powder is compacted by hot isostatic pressing on the steel base body.

The application of the nickel-titanium coating on the base material is also possible by friction welding. In the process, which is also generally referred to as friction coating, a coating is produced by means of transfer by plastic deformation under temperature and friction stress. The use of a titanium-containing alloy for friction coating is known in principle, for example, from DE 10 2006 055 994 A1. Another method for friction coating is disclosed in DE 10 2012 001 779 A1. In all designs, the thickness of the nickel-titanium alloy depending on the depth of the introduced during operation of the rolling bearing pressure can be interpreted. Typical layer thicknesses of the nickel-titanium alloy are in the range between 0.5 mm and 5 mm. Compared to the thickness of the rolling bearing ring, the nickel-titanium layer is relatively thin in any case. Preferably, the thickness of the nickel-titanium coating is not more than 5% of the underlying thickness of the base material.

Irrespective of the manner in which the nickel-titanium layer is produced, either rolling elements made of steel or rolling elements made of ceramic can roll on the roller bearing ring. Especially with the use of ceramic rolling elements, the advantages of the low modulus of elasticity of the nickel-titanium alloy compared to the modulus of elasticity of the rolling elements are particularly significant. A ceramic material from which the rolling elements can be produced is, for example, silicon nitride. In an advantageous embodiment, the modulus of elasticity of the ceramic rolling elements used in the rolling bearing is more than twice as large, in particular more than 2.5 times as large as the modulus of elasticity of the coating of the rolling bearing ring. However, the low tendency to adhesion due to the use of different materials for the raceway on the one hand and the rolling elements on the other hand is also given when using steel rolling elements. The rolling bearing ring is thus in any case suitable for use under unfavorable lubrication conditions.

The at least one designed according to the invention rolling bearing ring having rolling bearing can either have a cage for guiding the rolling elements or be designed as a full complement bearing. A roller bearing cage may optionally be made of metal, in particular of corrosion-resistant steel, or of plastic, in particular a suitable for use at higher temperatures plastic such as PEEK (polyetheretherketone).

In addition to bearings operated at high temperatures and / or rotational speeds, a preferred field of application of the rolling bearing ring is also so-called media-lubricated bearings. Media lubrication generally refers to contacting the rolling contact surfaces with a medium which is not primarily intended for lubrication. This may be, for example, a fluid which is conveyed in a pump equipped with the roller bearing or a compressor. The use of a roller bearing under water, especially in seawater, which is not or only partially sealed, is also considered to be the medium-lubricated operation of a roller bearing. Applications of the rolling bearing ring are given for example in the chemical and pharmaceutical industries, in the medical field, as well as in the food industry.

Two exemplary embodiments will be explained in greater detail below with reference to a drawing. SHORT DESCRIPTION OF THE DRAWING FIG

1 shows a cross section through a coated with a nickel-titanium alloy rolling bearing ring, Fig. 2 shows another embodiment of a nickel-titanium-coated rolling bearing ring in a representation analogous to Figure 1 Detailed Description of the drawing

Corresponding parts in principle are marked in both figures with the same reference numerals. The following statements relate, unless otherwise stated, to both embodiments.

A rolling bearing ring 1 of a rolling bearing not shown is made up of a base body 2 made of steel and a coating 3 applied thereon made of a nickel-titanium alloy, namely nitinol 60. The surface of the coating 3 forms a raceway 4 for rolling elements, not shown, namely cylindrical rollers in the embodiment of Figure 1 or balls in the embodiment of Figure 2.

The base body 2 is produced by machining, for example, from a common bearing steel such as 100Cr6 or from a stainless steel such as that available under the name Cronidur 30 (X 30 CrMoN 15 1) available steel with the material number 1 .4108. Notwithstanding the examples outlined in FIGS. 1 and 2, the main body 2 can also be produced by non-cutting shaping, in particular from sheet metal. Likewise, the rolling bearing ring 1 can not only, as in the two embodiments, be a bearing ring of a radial bearing, but also a component of another rolling bearing type, for example an angular contact ball bearing, a tapered roller bearing, or a thrust bearing. Equipped with the rolling bearing ring 1 bearing can be designed as a single or multi-row bearing.

In the exemplary embodiment according to FIG. 1, the nickel-titanium alloy used for producing the coating 3, namely nitinol 60, initially exists as a metal strip. Between this metal ring in the form of a thin ring band and the base body 2 made of steel, a press fit is produced. This can be done, for example, by - in the case of the formation of the rolling bearing ring 1 as an inner ring - of the coating 3 forming nickel-titanium ring is pressed or - if the roller bearing ring 1 is an outer ring - the nickel-titanium ring is pressed. Post-processing of the raceway 4 after assembly of the rolling bearing ring 1 is not required.

According to an alternative production method, the coating 3 of the roller bearing ring 1 according to FIG. 1 is designed as a friction coating. The application of the coating 3 to the base body 2 takes place, for example, by means of a rotating, vibrating and / or vibrating, typically pin-shaped applicator element, which contacts the base body 2 with a defined contact pressure. In the embodiment of Figure 2, in which the rolling bearing ring 1 is designed as a bearing ring of a deep groove ball bearing, the coating 3, which is also formed here from nitinol 60, produced by metal powder injection molding. After the application of the coating 3 on the base body 2, a finish machining is required at best, which has only a minimal influence on the contours of the rolling bearing ring 1.

Instead of an inner ring as a rolling bearing ring 1, it is also possible, for example, to provide a shaft in the form of a solid shaft or a hollow shaft, on which the coating 3 is located directly For example, instead of a rolling bearing ring 1 designed as an outer ring, a housing may be provided in which there is a bore, the wall of which is coated directly with the coating 4 of the nickel-titanium alloy Nitinol 60 forming the raceway 4.

In the first embodiment outlined in FIG. 1, the rolling elements rolling on the roller bearing ring 1, namely cylindrical rollers, are made of steel, for example. In the exemplary embodiment according to FIG. 2, rolling on the roller bearing ring 1, for example, ceramic balls. The ceramic balls of the roller bearing having the rolling bearing ring 1 are made of silicon nitride, for example, and have a modulus of elasticity of at least 300 GPa, for example, 310 GPa. In both cases, the steel used in comparison to conventionally used roller bearing rings provides a low modulus of elasticity of the nickel-titanium alloy forming the coating 3 (approximately 14 GPa) for low pressures in the rolling contact, even with approximately punctiform contact between the rolling element and the rolling bearing ring 1 , And thus for a reliable operation and low wear even with unfavorable lubrication conditions and / or extreme speeds of the rolling bearing ring 1 having rolling bearing.

LIST OF REFERENCE NUMBERS

roller bearing ring

body

coating

career

Claims

claims

1 . Rolling bearing ring (1), with a base body (2) on which there is a coating (3) forming a raceway (4), characterized in that a nickel-titanium alloy is provided as the coating (3).

2. rolling bearing ring according to claim 1, characterized in that the coating (3) is designed as a metal strip.

3. rolling bearing ring according to claim 1, characterized in that the coating (3) is formed by a powder metallurgical metal layer.

4. rolling bearing ring according to claim 1, characterized in that the loading layer (3) is designed as a friction coating.

5. rolling bearing ring according to one of claims 1 to 4, characterized in that the coating (3) has a nickel content of more than 50 wt .-%.

6. rolling bearing ring according to claim 5, characterized in that the coating (3) 60 wt .-%. Nickel and 40 wt .-% titanium.

7. rolling bearing ring according to one of claims 1 to 6, characterized in that the coating (3) has a thickness of at least 0.5 mm and at most 5 mm.

8. Use of a rolling bearing ring (1) according to claim 1 in a medium-lubricated, in particular water-lubricated, rolling bearing.

9. Rolling bearing, comprising a rolling bearing ring (1) according to claim 1 and a number of rolling elements made of ceramic. Rolling bearing according to claim 9, characterized in that the modulus of elasticity of the rolling elements more than twice as large as the modulus of elasticity of the coating (3) of the rolling bearing ring (1).