DE202018106176U1 - Metallic rolling or sliding bearing component - Google Patents

Abstract

Metallic rolling or sliding bearing component (2, 4) with at least one non-sandblasted surface and with at least one partial metal coating, characterized in that the metal coating is applied by means of a cold spray method directly on the non-sandblasted surface.

Description

The present invention relates to a metallic rolling or sliding bearing component with at least one partial metal coating according to the preamble of patent claim 1.

Rolling or sliding bearing components, in particular bearing components of large bearings, obtained on their outer surfaces often galvanizing as a metal coating, such as corrosion protection. So far, in addition to painting with a zinc-containing paint, a flame-spraying galvanizing system is often used here. In addition, such galvanizing offers the advantage that zinc provides high coefficients of friction, which are favorable for the surfaces which are used for screwing or flanging the bearing.

In order to apply a metal coating on a surface, this surface is roughened to allow adhesion of the metal coating, which can be applied by flame spray galvanizing or a cold spray process. To roughen the surface to be coated, this can be prepared for example by sandblasting. For this, all other surfaces that are not to be coated must first be covered. The flame spray layer adheres essentially by a mechanical clamping and therefore requires a rough surface, which is achieved by sandblasting. The same applies to many lacquers or coatings applied by cold spray methods.

The disadvantage here, however, that the very hard particles of the sandblast can damage the surfaces of the rolling or sliding bearing component in addition to the desired roughening beyond and, for example, finely crafted contours, or for example, the flatness or other shape and position tolerances can change. Furthermore, it is possible that the sand blasting particles remain despite cleaning on the surface and get into the finished warehouse, where they can damage the raceways and can lead to significant damage to a premature bearing failure.

If the surfaces to be coated have been finely worked before galvanizing, the sandblasting required for the galvanizing may affect the quality of these finely machined surfaces, in particular the shape and position tolerances, too much. However, these are still desirable especially on outer mounting surfaces of the bearing. Therefore, post-processing of the surfaces may be required after coating to restore dimensional and dimensional tolerances. Otherwise, an undefined investment geometry may occur.

Moreover, even if the surfaces were prepared by sand blasting, the adhesion of flame spraying is a critical point. In order to ensure the adhesion of the flame-spraying galvanizing, therefore, usually a wrapping of the layer is made, d. H. the layer completely encloses the workpiece. However, if only flat surfaces are coated without wraparound, there is a risk of flaking, since the flame spraying galvanizing is not a closed layer and is vulnerable at their edges.

In addition, the zinc or zinc alloy powder is melted in the flame spraying galvanizing and blown in the form of drops on the surface. In particular, so-called overspray, that is to say drops dripping past the target at the destination, can lead to a layer formation at undesired areas. This results in a highly porous, sponge-like layer with difficult to control thickness and uneven surface. The resulting porous zinc layer has poor corrosion resistance and poor chemical resistance. Therefore, usually flame-sprayed zinc layers are additionally sealed with paints.

Other metal coatings also commonly use the methods described above. However, as described above, the coatings applied thereto require a roughened surface to adhere to the surface to be coated and show the same disadvantages.

It is therefore an object of the present invention to provide a metallic rolling or sliding bearing member having an improved metal coating that can be applied directly to a non-sandblasted surface.

This object is achieved by the metallic rolling or sliding bearing component according to claim 1.

A metallic rolling or sliding bearing component with at least one non-sandblasted surface and at least one partial metal coating is proposed. In contrast to known metallic rolling or plain bearing components in which a metal coating is applied by flame spraying, for which a sandblasted surface is required, the metal coating of the metallic rolling or sliding bearing component proposed here by means of a cold spray method, in particular a high pressure cold Spray method, applied directly to the non-sandblasted surface.

As explained above, it has previously been assumed that for all metallic coatings a roughened surface is required to allow good adhesion of the coating. The inventors have now surprisingly recognized that when using a cold spray process, in particular a high-pressure cold spray process, with sufficiently high kinetic energy and other boundary conditions good adhesion of the coating is present even without a prior roughening of the surface.

In the cold-spray process, also called cold gas coating or cold gas spraying, a preheated gas jet is generated, in which a predominantly metallic powder is fed, which, however, is not melted. The powder may include, for example, iron, zinc, copper, tin, aluminum, steel or a combination thereof. If the powder hits the non-roughened, in particular non-sandblasted, surface, the powder, with suitable parameterization, combines with the surface to form a coating.

Since no roughening of the surface of the metallic rolling or sliding bearing component is required, but instead the metal coating can be applied directly to the non-sandblasted surface, the metallic rolling or sliding bearing component may already be in its final shape, i.e. in its final shape. be coated with existing shape and position tolerances. In particular, by means of the cold spray method, the metal coating can be applied directly to ground surfaces. Since sandblasting of the surface to be coated is not required, sandblasting particles can still be prevented from adhering to the rolling or sliding bearing component after the coating, which could lead to damage to a bearing in which the rolling or sliding bearing component is installed. However, it is advantageous to degrease and clean the surfaces to be coated prior to coating to allow for better adhesion of the metal coating.

In addition to the possibility of coating entire surfaces, it is also possible to coat only small portions of a surface, and thereby either to produce local non-interconnected coating surfaces, or even produce a complete on Gleit- or rolling bearing component track, as for example may be favorable for a seal running surface.

In contrast to a coating that is applied by flame spraying, the cold gas-sprayed metal layer is non-porous and therefore does not have to be painted or sealed. Furthermore, the metal coating has a higher density than a flame sprayed zinc-coated layer. With suitable parameterization, layer densities of about 99% can be achieved, which thus hardly deviate from solid non-porous metal. Accordingly, the metal coating can be made very thin, for example in the range of 50 microns to 150 microns.

Furthermore, thermal spraying creates a thermal load on the workpiece during flame spraying. This becomes hot, which can be detrimental not only to the properties of the workpiece and the residual stresses of the layer, but also delays further processing and assembly of the workpiece after coating. With the cold spray, however, the thermal effect on the workpiece is much lower, which significantly less affects the sliding or rolling bearing component.
The metallic rolling or sliding bearing component can be, for example, the ring of a bearing, in particular of a large bearing. Other components of a bearing can also be provided with a metal coating which is applied by means of a cold spray process as described herein.

The metal coating is preferably applied by means of a high-pressure cold spray method, preferably with more than 50 bar. In particular, the pressure of the gas jet may be in the range of 50 to 100 bar.

By this high pressure, the mixture of gas jet and powder is accelerated via a nozzle to multiple supersonic speed, whereby it cools down again during the relaxation. The particles of the powder in the gas jet hit with high kinetic energy, in particular at a speed of up to 1000 m / s on the surface of the metallic rolling or sliding bearing component. However, the powder particles are no longer hot or molten. Rather, the particles adhere to the surface of the metallic rolling or sliding bearing component by local conversion of the kinetic energy, which leads to a kind of welding of the powder on the surface. Welding is understood to mean adhesion which is far above the values of mechanical clamping. For example, it may be an adhesion peel value of about 50 MPa. This is up to 10 times more than is expected from many paint systems as adhesion. The adhesion mechanism in the cold-spray process, in particular high-pressure cold-spray process, is therefore not based on a clamping of the particles on the surface, as is the case with a flame-spraying galvanizing, but on a connection of the powder with the surface. This compound can be produced particularly well by high pressure.

After application of the coating by means of the cold spray method, in particular a High pressure cold spray process, the powder supply can be turned off and the gas stream, such as nitrogen, are further enforced. This makes it possible to use the typically robot-guided cold spray gun similar to a high-pressure compressed air gun. By repeating the programmed coating geometry, it is possible to blow off any loose loose material particles that may have been placed on the workpiece surface in the spray booth. Such particles do not achieve the hardness of sand blasting grains and are far less dangerous for the bearing, however, the coating system can be used without additional technical effort as a final cleaning system directly after the coating process

The combination of the metallic rolling or sliding bearing component, or the non-sandblasted surface of the metallic rolling or sliding bearing component, and the at least one partial metal coating, which with kinetic bombardment by the cold spray method, in particular high-pressure cold spray method, has been manufactured, has residual compressive stresses. These residual compressive stresses of the material increase the resistance of the metal rolling or sliding bearing component, in particular the resistance to surface cracking, and the resistance to chemical or corrosive attack. The base material of the metallic rolling or sliding bearing component is compacted by the cold spray method and receives residual compressive stresses, similar to a non-abrasive shot peening and the metal coating itself also receives compressive stresses. This increases the stability and tightness of the entire metallic rolling or sliding bearing component.

In particular, the metal coating may be a corrosion protection layer. For the anticorrosion layer, for example, zinc or aluminum, or a combination thereof, may be supplied as powder to the gas jet of the cold spray process.

According to one embodiment, the metal coating additionally or alternatively has friction-changing particles. For example, the powder for the cold spray process may have friction-changing particles as hard material particles. Alternatively, friction modifying particles may be added to the powder comprising metals for a corrosion protection layer. In particular, these hard material particles may increase the friction by titanium diboride. The friction modifying particles can be used either to increase or to decrease the friction of the coated surface.

According to a further embodiment, the metal coating is formed as a first and at least one second layer, which are applied one above the other by means of the cold spray method, in particular the high pressure cold spray method. For example, the first layer may be a corrosion protection layer, and the second layer may be a friction-changing layer. Other layers or combinations of layers are also possible.

It is possible to connect the cold spray gun used for coating to multiple powder feed systems which feed parallel or optionally powders. As a result, a multi-layer system made of different materials can be applied with the same gun without retrofitting. For example, rolling bearing rings can be through hardened, or even case hardened only in the raceway area, so that the outer geometry to be coated can have very different hardness depending on the design. The weldability of the feedable metal powder is then not given in all cases. Therefore, it may be necessary to spray a first layer on the ring, which has the property of a bonding agent and is selected so that it is welded to the substrate. In turn, the actually desired layer, which is welded to the adhesion promoter layer, can then be sprayed onto this adhesion promoter layer. Depending on the ring material and hardness, for example, a layer of pure iron or of stainless steel can be placed under a zinc layer, as a result of which the adhesion of the entire system to a pure zinc layer is greatly increased.

Instead of providing a protective layer by the metal coating, or in addition to such a protective layer, it is also possible to use the metal coating to change the shape of the metallic rolling or sliding bearing component. For this example, iron or steel powder come into question. If the metal coating is not applied as a thin protective layer, but locally as a thicker layer, for example, the deposited metal may change the shape of the surface to form a shoulder or a plateau. In this way it is possible to adapt the shape of the metallic rolling or sliding bearing component, without performing a mechanical machining by milling or the like.

The metal coating may also include stainless steel or stainless steel particles that are supplied to the gas jet of the cold spray process. In particular, such a metal coating can serve as a primer for further layers.

Furthermore, a method for producing a metallic Wälz- or Sliding bearing component proposed with at least one non-sandblasted surface and at least one partial metal coating. Here, the metal coating by means of a cold spray method, in particular a high-pressure cold spray method, applied directly to the non-sandblasted surface. As explained above, this has the advantage that the surface to be coated can already be coated in its final form.

In particular, the metal coating is applied under high pressure, preferably at more than 50 bar. The high pressure causes a kind of welding of the particles, which are applied to the non-sandblasted surface by the cold spray process. These "welded" particles have the advantage that they can adhere better without pretreatment of the surface to be coated in comparison to previously used coatings that are applied by flame spraying. The applied by the cold spray process metal coating is not porous and therefore does not have to be painted or sealed.

According to a further embodiment, after the application of the metal coating, at least one second layer can be applied by means of the cold spray method, in particular the high pressure cold spray method. As explained above, other layers can also be applied by means of the cold spray method.

Furthermore, by applying the metal coating, the shape of the metallic rolling or sliding bearing component can be changed. For example, the metal coating may be applied in the form of a shoulder or plateau to alter the shape of the metallic rolling or sliding bearing component without milling or other machining. For this purpose, only the metal coating must be applied at the designated places thicker or more times. In this way, a simple adaptation of the shape of a metallic rolling or sliding bearing component is possible.

The cold-spray method, in particular high-pressure cold-spray method, has the further advantage that the particles contained in the gas jet adhere to the surface of the metallic rolling or sliding bearing component only if the particles in a straight, unbraked trajectory and sufficiently steep angle, ideally vertical angles, impinge on the surface. If the particles hit the surface at too low an angle, no liability arises. Therefore, it is possible that the metal coating is formed as a partial coating. For example, it can be sprayed into a bore in the axial direction, with no adhesion to the walls, unlike application of a coating by flame spraying. Only the area in which the gas jet impinges at a vertical or substantially vertical angle is coated. Therefore, the masking and masking requirement is lower in the cold spray process than in flame spray galvanizing.

Due to the much more precise material application with less and constant overspray, more uniform volume throughput, and a dense nonporous layer, the layer thickness tolerances when using the cold spray process, in particular high pressure cold spray process, substantially lower than in a flame spraying. As a result, the shape and position tolerances of the surface to be coated are shifted in a predictable manner and are not critically degraded. Experiments showed under certain boundary conditions in the method according to the invention a reduction of the layer thickness dispersion to only 1/10 of the scattering of flame spraying.

Further advantages and advantageous embodiments are given in the description, the drawings and the claims. In particular, the combinations of features given in the description and in the drawings are purely exemplary, so that the features can also be present individually or otherwise combined.

In the following, the invention will be described in more detail with reference to embodiments illustrated in the drawings. Here, the embodiments and the combinations shown in the embodiments are purely exemplary and are not intended to define the scope of the invention. This is defined solely by the appended claims.

• 1: eine schematische Schnittansicht eines Wälzlagers.

It shows:

• 1 : A schematic sectional view of a rolling bearing.

In the following, the same or functionally equivalent elements are identified with the same reference numerals.

In 1 is a rolling bearing 1 presented in a simplified sketch. The rolling bearing 1 has an inner ring 2 and an outer ring 4 on. Between the two rings 2 . 4 are rolling elements 6 rotatably arranged. The rolling elements 6 can be kept spaced apart by a cage, not shown. Alternatively, it may take place instead of the rolling bearing 1 also act around a sliding bearing.

The different components of the rolling bearing 1 For example, the inner ring 2 , the outer ring 4 or the rolling elements 6 , Can be provided as metallic rolling or sliding bearing components having a non-sandblasted surface. In this case, at least one non-sandblasted surface can be provided with at least one partial metal coating. The metal coating is applied directly to the non-sandblasted surface by means of a cold spray process, in particular a high pressure cold spray process.

For example, the metal coating may be a corrosion protection layer. Such a layer can be used around the inner ring 2 or the outer ring 4 provided with a protective layer to protect the components against corrosion or rust.

Heretofore, it has been considered that for such a metal coating, roughening, e.g. by sand blasting, which is required to be coated surface, so that the metal coating, which is applied by means of a flame spraying process, as a paint or by means of a cold spray process, adheres to the surface.

However, it has surprisingly been found that in the case of the cold spray method used here, in particular as a high pressure cold spray method, it is not necessary to use the surfaces of the components 2 . 4 previously roughen by sandblasting. This means that the metal coating on a surface of the components 2 . 4 can be applied, which is already present in its final form. In particular, the application of the metal coating preferably does not affect any shape or position tolerances.

The metal coating is in particular by means of a high pressure cold spray method with more than 50 bar on the surface of the metallic rolling or sliding bearing component 2 . 4 . 6 applied. By applying the metal coating under high pressure, a kind of welding of the metal particles, which are present in the gas jet of the cold spray process, with the surface of the rolling or sliding bearing component 2 . 4 . 6 , This welding creates a particularly stable metal coating, which, in contrast to a flame-spray galvanized coating shows a low risk of spalling. Furthermore, the metal coating applied by such a cold spray process is non-porous, and therefore additional painting or sealing may be eliminated.

Alternatively or additionally, the metal coating can also be applied to the inner ring 2 or the outer ring 4 be applied that the shape of the components 2 . 4 is changed. For example, the metal coating may be in the form of a shoulder or a plateau on one of the rings 2 . 4 be applied. For this purpose, it is only necessary to apply a thicker metal coating by means of the cold-spray method, in particular high-pressure cold spray method, or to apply the metal coating in several layers at one point.

The proposed metal rolling or sliding bearing component makes it possible to provide a rolling or sliding bearing component which has an improved metal coating, which is more stable compared to known coatings, which are applied, for example by flame spraying, and on an untreated or non-sandblasted Surface can be applied.

LIST OF REFERENCE NUMBERS

1

roller bearing

2

inner ring

4

outer ring

6

rolling elements

Claims (6)

Metallic rolling or sliding bearing component (2, 4) with at least one non-sandblasted surface and with at least one partial metal coating, characterized in that the metal coating is applied by means of a cold spray method directly on the non-sandblasted surface. Metallic rolling or sliding bearing component according to Claim 1 , wherein the metal coating by means of a high pressure cold spray method, preferably more than 50 bar, is applied. Metallic rolling or sliding bearing component according to one of the preceding claims, wherein the metal coating is a corrosion protection layer. Metallic rolling or sliding bearing component according to one of the preceding claims, wherein the metal coating is formed as a first and at least one second layer, which are applied one above the other by means of the cold spray method. Metallic rolling or sliding bearing component according to one of the preceding claims, wherein the metal coating is adapted to change the shape of the metallic rolling or sliding bearing component (2, 4). Metallic rolling or sliding bearing component according to one of the preceding claims, wherein the metallic rolling or sliding bearing component has compressive stresses.

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