Patent Application
20240183397
This application claims priority to German patent application no. 10 2022 213 022.7 filed on Dec. 2, 2022, the contents of which are fully incorporated herein by reference.
The present disclosure is directed to a plain bearing ring having a cladded surface, a plain bearing including the plain bearing ring and a method of producing the plain bearing ring.
Plain bearings can be used in various technical spheres, with different requirements being imposed on these plain bearings, for example in terms of load rating or load-bearing capacity, depending on the sphere of application. The load rating defines the force or load that can be absorbed by a plain bearing before it is permanently damaged. Among other things, in the field of hydraulic steel construction, e.g. the mounting of gates in dams and sluices, the requirement imposed on the (quasi-)static load-bearing capacity, i.e. the maximum loading of a plain bearing, is very exacting in order to ensure safe use even after earthquakes, etc.
Until now, plain bearings formed of monolithic rings, i.e. rings made of a solid material, have often been used. The solid material of at least one of the rings is a sliding material in order to ensure the slidability of the rings with respect to one another. For example, bronze or other copper alloys can be used for this purpose. However, bronze, for example, is a material that often meets customer requirements for the load-bearing capacity of plain bearings only to a limited extent, especially in the field of hydraulic steel construction. The demand imposed on the load-bearing capacity of such plain bearings overloads the elastic limit of such a bronze material. The elastic limit defines the value of the mechanical stress, upon the exceeding of which plastic deformation occurs. The load-bearing capacity or load rating required in various spheres of application (e.g. hydraulic steel construction, steel industry, oil and gas industry, mining) where high load-bearing capacity, corrosion resistance or contamination resistance is required would, however, lead to plastic deformation of a bronze ring, as it has been used to date, at the corresponding maximum force. Such plastic deformation may, for example, lead to a reduced bearing operating time due to losses of performance or possibly failures of the bearings.
It is therefore an aspect of the present disclosure to provide a plain bearing, which provides low plastic deformation and good slidability with a simultaneously high load rating.
The disclosed plain bearing ring has a base material and a layer applied to the base material. In order to now provide a more highly loadable plain bearing ring compared to previous plain bearing rings, which gives the plain bearing a higher load rating or load-bearing capacity and at the same time provides good sliding properties, the base material used is a metallic material with a higher elastic limit than the material of the layer applied to the base material. Such a metallic material has a higher strength and yield strength than the material of the applied layer. For example, this can be a steel, especially steels whose strengths can be further increased by heat treatment. In this way, the plain bearing ring can have an increased load rating, e.g. compared to a monolithic ring made of a copper alloy.
In this context, a plain bearing ring is understood to mean a component which has a running surface that moves counter to a counter-running surface of another component. This may be a plain bearing ring having inner and outer rings. However, the plain bearing ring may also be a shaft, in particular hollow shaft, bushing, flange bushing or similar, which in each case has a running surface. Furthermore, the plain bearing ring can have a cylindrical running surface, but may also have spherical or other curved running surfaces. In particular, the plain bearing ring can be used in a spherical bearing, which can be in the form of a radial, inclined or axial spherical bearing. However, it should be noted that the plain bearing ring is not restricted to the specifically mentioned embodiments, but that each component can be provided with a running surface, as is defined above.
In order to ensure not only a sufficient load rating, but also good slidability of the plain bearing ring, the applied layer is a laser-clad layer. Such a laser-clad layer represents a reliable, inter-metallic connection between the applied layer and the base material. In laser deposition welding or laser cladding, a flat metal bond is produced between the two materials, i.e. the base material and the applied layer. The base material is heated by a laser and melted. At the same time, an inert gas mixed with fine powder or wire material, the material of the layer to be applied, is supplied (Directed Energy Deposition (DED) method). At the heated point, the powder or wire material melts and bonds with the base material. Laser cladding, in which the material of the layer is melted onto the base material, eliminates the need for additional coatings to improve adhesion, such as copper or nickel coatings, as is the case with galvanic coatings.
Since a metal which has a higher elastic limit than the material of the laser-clad layer is used as the base material, a high load rating or load-bearing capacity of the plain bearing ring overall can be provided. This enables the load rating of the entire plain bearing ring to be increased beyond the elastic limit of the laser-clad layer.
The laser-clad layer creates a secure, permanent connection between the laser-clad layer and the base material. Furthermore, by using the base material with a higher elastic limit, irreversible deformation of the entire plain bearing ring is significantly reduced or takes place within the permissible load rating range only in the laser-clad layer. Although such a deformation of the laser-clad layer may reduce the tribological performance under marginal load conditions, the risk of a safety-related failure or malfunction due to strong irreversible ring deformation or bearing deformation is significantly reduced by the base material. At the same time, in addition to the increased load-bearing capacity because of the combination of base material and laser-clad layer, the laser-clad layer means that the friction can be reduced and/or the plain bearing ring can be protected from corrosion and/or wear, as is explained in more detail below. Owing to the higher load-bearing capacity, the plain bearing ring, or a plain bearing in which the plain bearing ring is installed, may be, for example, smaller than was possible in the case of previous plain bearing rings.
According to one embodiment, the laser-clad layer is a friction-reducing layer, a corrosion protection layer and/or a wear protection layer. If the laser-clad layer is applied only to the raceway of the plain bearing ring, it can be used in particular as a sliding layer. Preferably, in such a case, it is formed from a material that can fulfil the functionality of a sliding layer, such as a copper alloy. In this way, the sliding function of the plain bearing ring can be increased in comparison to a plain bearing ring made only of the base material. Instead or in addition to the function of a sliding layer, the laser-clad layer can also be used to protect against corrosion and/or wear, either only in the region of the raceway or in the region of the entire bearing ring, especially if the laser-clad layer is applied to the entire surface of the sliding bearing ring, as explained below.
According to a further embodiment, the laser-clad layer has friction-reducing and/or wear-reducing fillers. For example, additional friction- and wear-reducing fillers can be added to the material of the laser-clad layer in the course of the cladding process. These fillers can be embedded in the laser-clad layer or applied to the laser-clad layer flat or at least flat over a proportion of the area. The fillers may include organic fillers such as polytetrafluoroethylene (PTFE), polyether ether ketone (PEEK), polyamide imide (PAI), polyimide (PI) and/or Polybenzimidazole (PBI), inorganic fillers such as molybdenum disulfide (MoS2), graphite, carbon nanotubes, graphene, tungsten disulfide (WS2), hexagonal boron nitride, and/or friction-reducing metallic or semi-metallic alloy elements such as Sn, In, Bi, Pb, Ag. Sb, either alone or in combination or the like. In addition, lubricants, dry sliding materials or the like can be introduced in other known ways, for example by inserting dry sliding materials into bores (e.g. solid lubricant plugs) or other structures, e.g. grooves. In this way, the laser-clad layer can not only improve, for example, the slidability of the plain bearing ring, while at the same time a high load rating is ensured by the base material, but the laser-clad layer can also fulfil further additional functions, such as an additional friction reduction or wear reduction by such fillers.
Since the material from which the laser-clad layer is made can be mixed with friction- and/or wear-reducing fillers directly during the deposition welding, the effort and/or the costs for the introduction of such a lubricant, especially with dry sliding materials, is reduced. In particular, the dry sliding material can be introduced here directly into the metal powder or the wire material, which is welded onto the base material of the plain bearing ring during the deposition welding. An additional step is not necessary here.
The plain bearing ring can be subjected to further processes, such as a coating, both before the application of the laser-clad layer and after the application of the laser-clad layer, in order to achieve a desired component property, such as additional corrosion protection or the like. For example, it is possible to provide further layers under and/or on the laser-clad layer in addition to the laser-clad layer in order to provide the plain bearing ring with further functions or properties.
The metallic material of the base material can be, for example, steel, such as tempered steel 42CrMo4+QT or rolling bearing steel 100Cr6 or higher alloyed steel with a low carbon content. In particular, the base material may be boron-alloyed steel, in particular with a boron content of 0.0008% by mass to 0.0050% by mass. Such a base material may be, for example, 27MnCrB5-2 and 33MnCrB5-2 in accordance with EN ISO 683-2 (EN ISO 683-2:2016). A boron-alloyed steel affords the advantage that relatively high hardness and strength values are made possible with a low carbon content at the same time. In addition, boron-alloyed steels typically contain little to no nickel. By dispensing with nickel, which constitutes a high cost factor, cost-effective production of the plain bearing ring is thus possible.
The metallic material of the base material can furthermore provide the advantage that it can be selected so that it is magnetizable in comparison to plain bearing rings, which have a copper alloy as the solid material. This magnetizability enables easier machining, as the plain bearing ring can be magnetically clamped, for example.
According to one embodiment, the base material has a carbon content of less than 0.37 m-%. The less carbon is contained in the base material, the easier it is to apply the sliding layer by deposition welding. A low carbon content (i.e. a carbon portion of less than 0.37%) avoids or reduces martensitic microstructure transformations, thereby reducing undesirable hardness peaks and the risk of cracking and chipping of the laser-clad layer.
According to a further embodiment, the laser-clad layer comprises a copper alloy, in particular bronze. Such a copper alloy, e.g. bronze, brass, aluminium-bronze or copper-nickel-tin (CuNiSn), constitutes a material that is particularly well suited as a sliding layer, since it has good sliding properties because of a low tendency to seize or to exhibit adhesive wear.
The layer thickness of the laser-clad layer is preferably up to a maximum of 10 mm. This layer thickness is preferably not exceeded in the applied state, i.e. without final processing, nor in the overturned or ground state. Compared to the thickness of the base material, the laser-clad layer is therefore relatively thin. This has the advantage that the high load rating, which is given to the plain bearing ring by the base material, is not affected by the laser-clad layer.
According to a further embodiment, the laser-clad layer is provided on the entire surface of the plain bearing ring. If the laser-clad layer is applied not only to the sliding surface or raceway, but also to the entire plain bearing ring, this has the advantage, for example, that corrosion protection can be provided in addition to the function of the slidability, depending on the choice of the material welded on. Since the laser-clad layer surrounds or encloses the entire base material of the plain bearing ring, the base material is completely shielded from the outside, and the laser-clad layer can protect the plain bearing ring from corrosion.
Furthermore, the laser-clad layer can be applied as a multi-layered system. In this case, the laser-clad layer may be formed by a plurality of layers, which may be formed of the same or optionally different materials. As already explained above, in addition to the laser-clad layer, additional layers which may provide further additional properties may be present below or above the laser-clad layer.
According to another aspect, a plain bearing having a plain bearing inner ring and a plain bearing outer ring is proposed. The two rings are rotatable relative to each other. At least one of the rings is formed by a plain bearing ring as described above. This has the advantage that the two rings are made of a relatively inexpensive base material, such as boron-alloyed steel or tempered steel, and a laser-clad layer of more expensive material, such as bronze, is applied to at least one of the rings. The laser-clad layer creates a stable, flat metal bond between the base material and the laser-clad layer. The sliding surface on one of the rings provides a good sliding property between the two rings, and the other ring can also be made from an inexpensive base material, such as a standard ring material 42CrMo4+QT. The base material of the sliding rings, which is in particular a metallic material with a higher elastic limit than the material of the laser-clad layer, furthermore has the advantage that, in the case of radially or axially split rings, screwing of the ring halves is reliably possible because of the more stable material.
According to a further aspect, a method for producing a plain bearing ring is proposed, wherein the plain bearing ring has a base material and a layer applied to the base material. The method furthermore comprises the step of applying the layer on the base material by laser cladding (Directed Energy Deposition (DED) method) either using wire material or with an application material in powder form), the base material being a metallic material which has a higher elastic limit than the material of the laser-clad layer.
The features and benefits described above with respect to the plain bearing ring and the plain bearing apply to the method in an analogous manner.
Further advantages and advantageous embodiments are specified in the description, the drawings and the claims. In particular, the combinations of the features specified in the description and in the drawings are purely exemplary, and therefore the features can also be present individually or in other combinations.
In the following, the invention will be described in more detail using exemplary embodiments illustrated in the drawings. The exemplary embodiments and the combinations shown in the exemplary embodiments are purely exemplary and are not intended to define the scope of protection of the invention. This is defined solely by the attached claims.
In the following, identical or functionally equivalent elements are identified by the same reference signs.
In order to provide a cost-effective, but at the same time efficient plain bearing 1, at least one of the plain bearing rings 2, 4 has a laser-clad sliding layer 6 (not drawn to scale) that forms a sliding surface of the at least one of the plain bearing rings 2, 4. The laser-clad layer 6 is preferably formed from a sliding material, such as, for example, a copper alloy, such as bronze or aluminium-bronze. As shown in
In order, in addition to the required sliding property, also to provide a high load rating or load-bearing capacity of the plain bearing 1, the plain bearing outer ring 4 includes a base material 8 on which the sliding layer 6 is applied by means of laser cladding. The base material 8 is a metallic material, such as boron steel or rolling bearing steel, which permits a high load rating. In particular, the base material 8 has a higher elastic limit than the material of the laser-clad layer 6. Optional lubrication bores 9, 11 can be introduced into the base material 8, 10 of the plain bearing outer ring 4 and the plain bearing inner ring 2.
The sliding layer 6 is applied to this base material 8 as a thin laser-clad layer and provides the slidability of the plain bearing outer ring 4 required for the plain bearing 1. The combination of base material 8 with a high or higher elastic limit and sliding layer 6 made of sliding material makes it possible to maintain a high load rating with good sliding properties at the same time.
In contrast to previous plain bearings, in which the rings were formed exclusively of a sliding material, the combination of base material 8 with a high elastic limit (an elastic limit higher than the elastic limit of the base material) and a sliding layer 6 provides both a high load rating and the slidability required for sliding bearings. Furthermore, a good connection between the base material 8 and the sliding layer 6 is made possible by the deposition-welded sliding layer 6. Laser cladding permits a flat, stable and durable metal connection between the two materials and thus a long-lasting plain bearing 1.
In a further embodiment, which is shown in
Instead of a radially divided outer ring 4, 4′, an axially divided outer ring 4 may also be provided with such a laser-clad layer 6, as is shown in
In the embodiment shown here, the laser-clad layer 6 in turn is applied only to the sliding surface of the plain bearing outer ring 4. Since the base material 8 of the plain bearing outer ring 4, 4′ is a material with a high elastic limit (an elastic limit higher than that of the material of the laser-clad layer 6), the plain bearing outer ring 4, 4′ can be connected with screw connections 12, 12′. Such screw connections 12, 12′ would not be possible if the plain bearing outer ring 4, 4′ is completely made of a sliding material, since the sliding material does not have sufficient strength to be able to securely attach such a screw connection.
As is shown in
Instead of applying the laser-clad layer 6 to the plain bearing outer ring 4, 4′, it is also possible to provide the laser-clad layer 6 on the plain bearing inner ring 2, as is shown in
The laser-clad layers or sliding layers 6 described above can be equipped with additional functionalities by introducing further fillers into the material of the laser-clad layer 6, which serve to reduce friction and/or wear. Furthermore, it should be noted that the embodiments shown above apply to both the plain bearing inner ring 2 and the plain bearing outer ring 4, 4′ and are used in each case on at least one of the plain bearing rings 2, 2′, 4, 4′. Alternatively, it is also possible to provide the laser-clad layer 6 both on the plain bearing inner ring 2 and on the plain bearing outer ring 4, 4′, wherein the sliding layer 6 can be applied in each case only partially, in particular on the sliding surface, or completely around the respective ring.
By means of the above-described plain bearing or the described plain bearing rings, it is possible to provide a plain bearing ring, which can ensure a high load rating and at the same time shows no losses in terms of slidability.
Representative, non-limiting examples of the present invention were described above in detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Furthermore, each of the additional features and teachings disclosed above may be utilized separately or in conjunction with other features and teachings to provide improved plain bearings.
Moreover, combinations of features and steps disclosed in the above detailed description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe representative examples of the invention. Furthermore, various features of the above-described representative examples, as well as the various independent and dependent claims below, may be combined in ways that are not specifically and explicitly enumerated in order to provide additional useful embodiments of the present teachings.
All features disclosed in the description and/or the claims are intended to be disclosed separately and independently from each other for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter, independent of the compositions of the features in the embodiments and/or the claims. In addition, all value ranges or indications of groups of entities are intended to disclose every possible intermediate value or intermediate entity for the purpose of original written disclosure, as well as for the purpose of restricting the claimed subject matter.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102022213022.7 | Dec 2022 | DE | national |
