Component of a rolling bearing and method for its manufacture

Description

[0001] The invention relates to a component of a rolling bearing with at least one rolling element comprising a base substrate made of metal with at least one surface region configured as a bearing surface of a rolling bearing with at least one rolling element. Furthermore, the invention relates to a method for producing a component with at least one coated surface region, in which the coating of the surface region of the component serving to provide a bearing surface of a rolling bearing is applied by high-velocity flame spraying, and the coating is subjected to a machining surface treatment after the high-velocity flame spraying.

[0002] Rolling bearings are machine elements that consist of so-called rolling elements and usually have an inner and outer ring as bearing surfaces on which the rolling elements roll. The rolling elements can be spherical or cylindrical, for example. Other shapes, such as barrel or conical, are also conceivable. Rolling bearings, for example, also have roller tracks in rail guides instead of inner or outer rings, so that the rolling elements perform guided movements on the rail guides. This type of rolling bearing is used, for example, to move the wing flaps of aircraft. Cylindrical rollers are often used as rolling elements here. These are guided in rail guides as roller tracks and ensure, for example, the movement of the wing flaps under very high loads.Compared to spherical rolling elements, cylindrical rollers can absorb higher radial forces in a rolling bearing because they provide a contact line with a larger contact area. For the same radial force, the contact area of ​​a line contact generates lower pressure conditions in the rolling contact compared to the point contact of a ball in a rolling bearing. Depending on the pressure conditions, however, the load can cause a deformation of the rolling elements and bearing surfaces, known as "Hertzian deformation," which can lead to material stress, fatigue, and even wear of the bearing partners. Particularly under critical lubrication conditions, i.e., when there is little or no lubricant in the rolling contact and very high loads are absorbed, the wear properties of the contacting materials of the bearing surface and rolling elements are crucial.The bearing surfaces of rolling bearings are therefore made of particularly wear-resistant, for example, particularly hard materials. However, very hard materials are generally brittle, so a particularly hard and therefore wear-resistant surface area is preferably created by coating on ductile substrates. In addition to hard chrome plating, which can also be performed in an immersion bath, coating the bearing areas with thermal spraying of highly wear-resistant alloys has proven advantageous for easily accessible bearing areas.

[0003] In high-velocity flame spraying, the material to be applied is melted or partially melted, accelerated, and sprayed at high speed onto the cleaned and pretreated base substrate. After the hot coating particles impact the surface of the base substrate, they cool down and can thus bond to the surface of the base substrate. For this purpose, the base substrate is usually additionally roughened. High-velocity flame spraying is one of the newer thermal spraying processes and, compared to conventional flame spraying, is characterized by a supersonic gas jet. This results in much higher particle impact speeds on the substrate, resulting in improved coating properties. In addition to propane, propylene, acetylene, and hydrogen, natural gas or liquid fuels such as kerosene can be used as fuel gases.Detonation spraying is also considered high-velocity flame spraying in this application. In detonation spraying, the material is applied to the base substrate by detonations of the fuel ignited in quick succession.

[0004] Until now, it was assumed that the surface coating of bearing surfaces would be particularly wear-resistant if it had the highest possible hardness, for example, measured in HRc. However, high radial forces can then cause Hertzian pressure on one of the bearing components, the rolling element or the bearing surface, and thus deformation of the rolling element or the bearing surface. If movement occurs simultaneously in the bearing, this can result in severe wear on one of the bearing components. Currently used coatings, such as those made of tungsten carbide, therefore exhibit wear behavior that requires improvement.

[0005] Especially in means of transportation, such as aircraft, safety-critical components can benefit from improved wear behavior. This applies, for example, to the safety-critical roller bearings of aircraft wing flaps, which must ensure reliable operation even under critical lubrication conditions.

[0006] The German patent application DE 10 2009 023 818 A1 discloses rolling bearings with low-wear bearing surfaces that have a chemically deposited nickel-phosphorus layer.

[0007] International patent application WO 2016 / 011218 A1 relates to wear-optimized bearing surfaces composed of zones of varying hardness. The coating is applied by spraying the bearing surface with a liquid containing carbon particles, followed by laser treatment to diffuse the particles.

[0008] The US patent application US 2020 / 0408261 A1 discloses a three-layer coating of a bearing surface, which consists of a layer essentially containing chromium applied to the bearing component, a first mixed coating with decreasing tungsten oxide content and a further surface layer with diamond-like carbon particles (DLC) with different hardnesses.

[0009] The German patent application DE 10 2013 223 677 A1 relates to an easy-to-manufacture, electrically insulating rolling bearing which has an insulating layer made of artificial or natural resin.

[0010] The international patent application WO 2014 / 139941 A1 and GB 2514445 A1 disclose rolling bearing elements with multilayer coatings made of non-metallic materials.

[0011] The US patent US 5,439,297 discloses a rail guide with a single-layer coating of the bearing surface, while the European patent application EP 2 669 399 A1 and the German laid-open specification DE 11 2015 002 677 T5 disclose multi-layer coatings of bearing surfaces.

[0012] Against this background, the object of the present invention is to provide an alternative component which has a surface area for providing a bearing surface of a rolling bearing, which has a significantly improved wear behavior even when absorbing very high radial forces and low lubricant coverage and can be manufactured economically.

[0013] The above-mentioned object is achieved with a component according to patent claim 1 and with a method according to patent claim 12.

[0014] According to the invention, the at least one surface region of the component has a coating which has a first hardness in a first coating region adjacent to the base substrate of the first component and has a second hardness in a second coating region in contact with the at least one rolling body, and the first hardness is lower than the second hardness.

[0015] It has surprisingly been found that by using a softer first coating area adjacent to the base substrate in conjunction with a second coating area, which forms the rolling contact with the rolling element and has a higher hardness, the wear behavior of a rolling bearing for absorbing very high radial forces could be significantly improved.

[0016] The reason for this is seen in the fact that the softer first coating area allows slight deformation of the harder and more brittle coating area that is in contact with the rolling element, without damaging the coating of the second coating area or the entire coating. The first and second coating areas are formed on the base substrate in the direction of the rolling element, starting with the first and ending with the second coating area, for example as layers parallel to the base substrate, whereby further coating areas can optionally be provided between the first and second coating areas. Due to the deformation of the bearing surface, the contact area of ​​the rolling element, for example the cylindrical roller or the ball of the rolling bearing, with the bearing surface is increased, thus improving the pressure conditions in the rolling contact.The Hertzian pressure, which causes high wear on the rolling bearing, can be shifted towards higher radial forces due to the larger contact area in the rolling contact, so that wear on both bearing components, the bearing surface and the rolling element, is significantly reduced. Due to the higher hardness of the second coating area, which is in contact with the rolling element, this area is particularly wear-resistant, without having to accept the disadvantage that the higher hardness leads to Hertzian pressure with high wear when radial forces increase. The component according to the invention is particularly advantageous for rolling bearings, which on the one hand must absorb high radial forces and on the other hand have difficult lubrication conditions. As already mentioned, this is particularly the case with the safety-relevant rolling bearings of wing flaps in aircraft.

[0017] According to an advantageous embodiment of the component, the second hardness of the second coating region of the component is greater than the hardness of the surface region of the at least one rolling element. This minimizes wear on the bearing surface, depending on the material used for the rolling element.

[0018] Preferably, the second coating region in contact with the rolling element has the highest hardness compared to the hardness of the rolling element, the base substrate, the first coating region, and optionally provided additional coating regions between the first and second coating regions. Very good wear results were achieved with this variant of the component according to the invention.

[0019] If, according to a further embodiment, the coating of the first component has two or more layers with different compositions to provide the first coating area with the first hardness and the second coating area with the second hardness, the first coating area can be specifically adapted to the base substrate and the second coating area can be specifically adapted to the rolling element in contact with the second coating area. A two-layer structure is the simplest layer sequence with which the coating areas of different hardness can be provided. The thicknesses of the two different coating areas can, for example, be between 20% and 80% of the total thickness each. Here, the thickness of the individual coating areas can be further optimized for the respective rolling bearing to be provided and the forces to be absorbed.For example, the two coating areas can have identical thicknesses. By using multiple layers, the wear properties of the rolling bearing can be further optimized, albeit with greater effort.

[0020] It is also possible, according to a further embodiment of the component, for the coating to have a hardness gradient such that the hardness of the coating increases from the first coating region adjacent to the base substrate of the component to the second coating region in contact with the rolling element, optionally continuously or layer by layer. In high-velocity flame spraying, for example, it is possible to change the coating composition during the coating process, optionally continuously or layer by layer, for example by changing the composition continuously or step by step during high-velocity flame spraying. This enables optimal adaptation of the component to the respective load situation of the rolling bearing. The same applies, for example, to laser deposition of coatings.

[0021] The thickness of the entire coating is preferably 0.2 mm to 1.5 mm, preferably 0.4 mm to 0.8 mm. Due to the relatively low thickness of the coating, the component according to the invention can be advantageously used in weight-sensitive applications.

[0022] If, according to a further embodiment of the component, the first hardness in the first coating region adjacent to the base substrate is a maximum of 60 HRc and the second hardness in the second coating region in contact with the rolling element is at least 57 HRc, the wear behavior can be well matched to the materials commonly used for base substrates and rolling elements, high-strength stainless steels but also high-strength titanium or aluminum alloys. This applies, for example, to rolling bearings with cylindrical rollers made of martensitic stainless steel, whereby the cylindrical rollers usually have a hardness of at least 40 HRc to 50 HRc. For the first coating region applied to the base substrate, a maximum hardness of 60 HRc ensures that the first coating region is not too brittle and thus enables deformation of the second coating region arranged on top of it.In addition, by limiting the hardness, the adhesive strength of the coating on the base substrate can be improved, since a certain ductility is advantageous here.

[0023] According to a further embodiment of the component, high radial forces can be absorbed in the rolling bearing by the first component being a rail guide for accommodating at least one cylindrical roller as the rolling element of a rolling bearing, and the coated surface area extending partially or entirely over the range of motion of the at least one cylindrical roller in the rail guide. Corresponding rolling bearings with rail guides as roller tracks for cylindrical rollers are used in aircraft, for example, for wing flaps, and must therefore be designed to be particularly wear-resistant.

[0024] It has also been shown that the tensile adhesive strength of the coating on the base substrate plays an important role in the wear properties, preventing the coating from detaching from the base substrate. According to a further embodiment, particularly low-wear coatings can be achieved by achieving a tensile adhesive strength (RH) of more than 70 MPa. The tensile adhesive strength (RH) is measured according to DIN EN ISO 14916:2017-8 for high-velocity flame-sprayed coatings. It has been shown that dividing the base substrate into at least two different, laterally arranged coating areas, with a lower hardness in the first coating area and a higher hardness in the second coating area, leads to higher tensile adhesive strengths (RH).

[0025] According to the invention, the coating of the surface area comprises at least one metallic alloy with the following alloying constituents in wt.%: 8 % ≤ Cr ≤ 18,5 % , 22,5 % ≤ Mo ≤ 33 % , 2,55 % ≤ Si ≤ 3,45 % , optional 14 % ≤ Ni ≤ 17 % , C < 0,1 % ,

[0026] Rest Co and unavoidable impurities or 12 % ≤ Cr ≤ 19 % , 28 % ≤ Mo ≤ 36 % , 3 % ≤ Si ≤ 4 % , 0,5 % ≤ Co ≤ 2 % , C < 0,1 % ,

[0027] Rest Ni and unavoidable impurities.

[0028] The cobalt- or nickel-based alloys of this component design all exhibit very high hardness due to the formation of so-called Laves phases. These are intermetallic compounds of the alloy components, which are extremely hard and brittle due to their crystal structure. They ensure high wear resistance. The described cobalt- and nickel-based alloys can be applied using high-velocity flame spraying, thus providing coated surface areas of the component according to the invention.

[0029] According to a next embodiment of the component according to the invention, the coating in the first coating region at least partially comprises a mixture of at least one metallic alloy and at least one unalloyed metal, wherein the total proportion of the unalloyed metal in the coating is a maximum of 60 wt.%, preferably 15 to 50 wt.% and the at least one unalloyed metal is cobalt, nickel, chromium, molybdenum, tantalum, copper, aluminum, indium, zinc or a mixture of at least two of the metals mentioned.

[0030] It has been shown that the use of unalloyed metal, such as nickel, in a metal alloy matrix in the first coating zone can reduce the hardness of the first coating zone while simultaneously increasing the tensile bond strength of the coating. This allows the first coating zone to be optimally adapted to the base substrate, resulting in the entire coating with a very high tensile bond strength (RH).

[0031] Using the aforementioned cobalt- or nickel-based alloy systems, which provide particularly brittle and wear-resistant intermetallic Laves phases, it was found that the unalloyed metal can allow a certain degree of deformability of the first coating area without damaging the highly brittle Laves phases of the metallic alloy. It is assumed that this can increase the contact area in the rolling contact, thus improving the wear resistance of the component. This results in particularly high wear resistance even under very high radial forces in the rolling bearing.

[0032] A further advantageous embodiment of the component can be provided by applying the coating by high-velocity flame spraying or laser deposition welding. When coating a material, the coating process used results in a coating structure specific to the application process. This applies, for example, to high-velocity flame spraying, in which the highly heated coating particles impact the base substrate at extremely high speed, for example, creating pancake-like structures there. Due to the very high speeds, these structures allow extremely small gaps between these particles. By cooling and clamping to the base substrate or cooled coating particles, the coating is firmly anchored to the base substrate. This results in a coating structure typical of high-velocity flame spraying.Due to the small number of defects in the coating produced by high-velocity flame spraying, it can be distinguished from coatings produced in other ways.

[0033] According to a further embodiment of the component, the coating has a surface roughness Ra of at least 0.1 µm to 2.5 µm, preferably 0.1 µm to 1.2 µm, for example, after machining the surface to provide a rolling bearing. This allows optimal friction conditions for the rolling element on the bearing surface to be provided.

[0034] If the coating has a porosity of less than 1.5% according to a further embodiment, the coating can absorb a lubricant in the pores and make this available to reduce friction in the rolling bearing. The porosity φ is determined by the following equation: ϕ = 1 − ρ / ρ 0 where ρ is the measured density and ρ 0 is the true density of the material.

[0035] The wear properties of the component according to the invention can be further improved by providing an applied lubricant which utilizes the porosity of the material to permanently provide the lubricant for a rolling bearing.

[0036] Finally, the component can be advantageously designed by forming part of a rolling bearing of a means of transport, preferably an aircraft. As already explained above, aircraft, in particular, have safety-relevant rolling bearings subjected to high radial forces. In particular, rolling bearings with cylindrical rollers guided in rail guides, which are used, for example, in the movement of wing flaps, must absorb high radial forces. With the component according to the invention, the bearing surfaces of these rolling bearings can be designed to be particularly wear-resistant.

[0037] The above-described problem is solved for a method for producing a component with at least one coated surface area by producing the first coating area adjacent to the base substrate and the second coating area of ​​the component in contact with the rolling element by high-velocity flame spraying of different coating compositions. High-velocity flame spraying allows the coating areas of the coated surface area of ​​the component to be produced precisely and simultaneously provides the required properties regarding the hardness and composition of the coating in a process-reliable and cost-effective manner.The coating must then be machined on the surface, usually by milling, grinding and polishing, in order to provide the surface roughness suitable for the rolling bearing, for example.

[0038] According to the invention, the at least one high-velocity flame-sprayed metallic alloy of the coating has the following alloy components in wt.%: 8 % ≤ Cr ≤ 18,5 % , 22,5 % ≤ Mo ≤ 33 % , 2,55 % ≤ Si ≤ 3,45 % , optional 14 % ≤ Ni ≤ 17 % , C < 0,1 %

[0039] Rest Co and unavoidable impurities or 12 % ≤ Cr ≤ 19 % , 28 % ≤ Mo ≤ 36 % , 3 % ≤ Si ≤ 4 % , 0,5 % ≤ Co ≤ 2 % , C < 0,1 %

[0040] Rest Ni and unavoidable impurities.

[0041] As already mentioned, the cobalt- or nickel-based alloy systems mentioned above provide alloys that form a high proportion of Laves phases, which are particularly hard and wear-resistant. By using different compositions during the high-velocity flame spraying of the coating on the first component, the hardness of the two coating areas can also be adjusted via the layer composition.

[0042] A further improvement in the properties of the coating can be achieved by producing the coating of the first coating region by high-velocity flame spraying a mixture of at least one metallic alloy and at least one unalloyed metal, wherein the total proportion of the unalloyed metal in the coating is a maximum of 60 wt.%, preferably 15 to 50 wt.%, in some regions and the at least one unalloyed metal is Co, Cr, Mo, Ta, Ni, Cu, Al, In, Zn or a mixture of at least two of the aforementioned metals. The addition of at least one unalloyed metal to a metallic alloy system during high-velocity flame spraying results in the unalloyed metal improving the ductility and reducing the hardness of the corresponding coating region. For example, with the addition of 15 to 50 wt.-% nickel to one of the above-mentioned alloy systems ensures that the unalloyed nickel, due to its lower hardness but higher ductility, protects the extremely brittle Laves phases formed by the alloy system from destruction during deformation of the first coating area. This increases the contact area, particularly when very high radial forces occur in the rolling bearing, and thus reduces the overall surface pressure. This allows higher radial forces to be absorbed in the rolling bearing without causing wear.

[0043] According to a further embodiment of the method, it has been found advantageous to spray the unalloyed metal separately during high-velocity flame spraying or to agglomerate or mix it with the at least one alloy prior to processing. Separate spraying and agglomeration of the unalloyed metal with the metallic alloy used achieve a particularly good distribution of the unalloyed metal within the metallic alloy structure, so that, due to the uniform distribution of the unalloyed metal in the matrix of the metallic alloy, both a significant improvement in the tensile adhesive strength RH and the provision of a bearing surface with the lowest possible wear are achieved.

[0044] The invention will be explained in more detail below using exemplary embodiments in conjunction with the drawing. The drawing shows Fig. 1 in a schematic sectional view of an embodiment of a component with a surface area for providing a bearing surface of a rolling bearing, Fig. 2 a microscopic image of a section through the coated surface area of ​​the embodiment of Fig. 1 , Fig. 3 in a schematic sectional view of a curved guide rail with cylindrical rollers as rolling elements and Fig. 4 a sectional view of the roller bearing from the Fig. 3 .

[0045] In Fig. 1First, a schematic sectional view shows an embodiment of a component 1 according to the invention with a surface region designed to provide a bearing surface 2 of a rolling bearing with at least one rolling element 3. The rolling element 3 shown in the sectional view is designed as a cylindrical roller in this embodiment. The component 1 has, in the surface region of the bearing surface 2, a base substrate 4, a first coating region 5, and at least one second coating region 6, wherein the first coating region 5 adjoins the base substrate 4 and the at least second coating region 6 is in contact with the rolling element 3. According to the invention, the first hardness of the first coating region 5 is less than the hardness of the second coating region 6.This design allows the softer coating area 5 to provide slight deformation of the bearing surface 2 under high loads without damaging the harder coating area 6. This results in an increase in the surface contact of the rolling element 3 in the rolling contact 3A. The increase in the contact area is accompanied by a reduction in the surface pressure in the rolling contact, thus preventing critical Hertzian pressures. As a result, wear can be reduced under high radial forces in the rolling bearing, thus minimizing overall wear.

[0046] Preferably, the hardness of the second coating area 6 is greater than the hardness of the rolling element, in this case the cylindrical roller 3. This results in good wear conditions with respect to the bearing surface 2 and the rolling element 3 with the simplest possible layer structure. As in Fig. 1As can be seen, the coating has exactly two coating areas 5 and 6, which provide different hardnesses due to their different compositions. In general, however, several coating areas with different compositions and hardnesses can also be used, whereby the coating area 6 in contact with the rolling element 3 should have a greater hardness than the coating area 5 adjacent to the base substrate in order to provide the advantageous wear properties.

[0047] A preferred material for the manufacture of rolling elements 3 is, for example, martensitic stainless steel. This achieves hardnesses between 40 and 58 HRc. The second coating area 6 preferably has a hardness of at least 57 HRc to provide sufficiently high hardness compared to rolling elements 3 made of martensitic stainless steel. The first coating area 5, which borders the base substrate, should, in contrast, have a maximum hardness of 60 HRc to, on the one hand, enable an increase in surface contact in the rolling contact 3A under high radial forces and, on the other hand, to provide good adhesion to the base substrate 4.

[0048] The adhesive tensile strength RH of the coating is preferably more than 70 MPa, so that detachment of the coating from the base substrate 4 during use of the rolling bearing can be largely prevented.

[0049] The two coating areas 5 and 6 preferably have the following alloy composition in wt.%: 8 % ≤ Cr ≤ 18,5 % , 22,5 % ≤ Mo ≤ 33 % , 2,55 % ≤ Si ≤ 3,45 % , optional 14 % ≤ Ni ≤ 17 % , C < 0,1 %

[0050] Rest Co and unavoidable impurities or 12 % ≤ Cr ≤ 19 % , 28 % ≤ Mo ≤ 36 % , 3 % ≤ Si ≤ 4 % , 0,5 % ≤ Co ≤ 2 % , C < 0,1 %

[0051] Rest Ni and unavoidable impurities.

[0052] The cobalt or nickel-based alloys can have very high hardnesses, which are provided by the formation of Laves phases. A further improvement in the wear properties is preferably achieved in that the coating in the first coating region 5 at least partially comprises a mixture of at least one metallic alloy and at least one unalloyed metal. The total proportion of the unalloyed metal can be a maximum of 60 wt.%, preferably 15 to 50 wt. Suitable unalloyed metals are Co, Cr, Mo, Ta, Ni, Cu, Al, In, Zn or a mixture of at least two of the aforementioned metals. A preferred mixture consists of the above-mentioned cobalt-based alloy with a proportion of up to a maximum of 60 wt.% nickel, preferably 15 to 50 wt.% nickel.

[0053] A microscopic image of a section through the bearing surface of a component according to the invention shows Fig. 2. Here, the base substrate 4 can be seen, which can be made of a titanium alloy or, for example, as shown, of steel. Two coating regions 5 and 6, which have different compositions, can be seen on the base substrate 4. The coatings 5 ​​and 6 were applied to the substrate by high-velocity flame spraying. The composition of the layers corresponds to that of exemplary embodiment E with the compositions E.1 and E.2 in Table 3. The total thickness of 844 µm and the thickness of the first coating region 5 of 321 µm were greater than in exemplary embodiment E.

[0054] It can be seen that the number of defects is lower in coating area 5 than in coating area 6. These are identified by the "black" dots. The two layers differ only in that coating area 5 contains a proportion of unalloyed nickel of 15 to 50 wt.%. It is therefore assumed that the unalloyed nickel can occupy or "smear out" corresponding defects in the layer to achieve improved adhesion to the base substrate. The tensile adhesive strength was particularly high for the layers with a corresponding proportion of unalloyed nickel, as can be seen in Table 4.

[0055] Preferably, the unalloyed metal is sprayed separately during high-velocity flame spraying to achieve the most homogeneous distribution of the unalloyed metal in the metallic alloy. Since powdered materials can be sprayed during high-velocity flame spraying, a very good distribution of the unalloyed metal in the coating can also be achieved by agglomerating the unalloyed metal with the powder particles of the metallic alloy prior to high-velocity flame spraying. Agglomeration refers to the powder particles of the unalloyed metal and the metallic alloy being "glued" together, preventing separation and demixing of the different materials during high-velocity flame spraying.

[0056] After machining, for example, by milling, grinding, and polishing, small roughnesses Ra of 0.1 µm to 2.5 µm, preferably 0.1 µm to 1.2 µm, can be achieved. The porosity of the coated surface is preferably less than 1.5%. The coating area 6 can therefore preferably contain a lubricant to provide improved friction properties in the rolling bearing. See above for values.

[0057] Different coatings were then applied to a steel base substrate 4. High-velocity flame spraying with liquid fuels was used for all coatings. Two metallic cobalt-based alloys, 1 and 2, were used, which can provide different hardnesses. The composition can be found in Table 1. Table 1 Alloy composition [wt.%] Alloy No. Co Cr Mon Si Ni Fe C 1 rest 16,5 - 18,5 27,5 - 29,5 2,4 - 4,4 ≤1,5 ≤ 1,5 < 0,1 2 rest 7,5 - 9,5 27,5 - 29,5 1,6 - 3,6 ≤1,5 ≤ 1,5 < 0,1

[0058] Starting with the two alloy systems, five different coatings were produced and subsequently tested for tensile adhesive strength (RH) and their top layer hardness. The coatings tested are shown in Table 2. The coatings according to Tests A, B, and C represent comparative examples, while Tests D and E are inventive embodiments of the present invention.

[0059] As already mentioned, all coatings were applied by high-velocity flame spraying using liquid fuels. In the as-applied, non-machined state, they were subjected to a tensile bond strength (RH) measurement according to DIN EN ISO 14916:2017-8 and a hardness measurement in HRc of the top layer. The actual hardness measurement was performed in Vickers hardness and converted to HRc using the conversion table in ISO 18265:2013. The term "top layer" refers to the bearing surface, i.e., the contact surface of the second coating area 6 with the rolling element 3. Samples with a diameter of 25 mm were used to measure the tensile bond strength (RH). Table 2 Attempt Number of shifts layer Shift type Thickness [mm] comment A 1 Leg. 1 0,8 Alloy only B 1 50% Leg.1 + 50% Leg.2 0,8 Both alloys processed as a powder mixture C 1 Leg. 2 0,8 Alloy only D 2 D.1 Alloy 2 + 15-50% Ni 0,26 Alloy and unalloyed metal processed as a powder mixture D.2 Leg.2 0,27 Alloy only E 2 E.1 Alloy 2 + 15-50% Ni 0,26 Alloy and unalloyed metal during processing (sprayed separately) E.2 Leg.2 0,27 Alloy only

[0060] In tests A, B, and C, coatings made of alloys 1 (A) or 2 (C), or a mixture of both alloys (B), were tested. It was found that the harder alloy 1 achieved the lowest tensile adhesive strength (RH) of 45 MPa with a very high hardness of 63 HRc. Despite the increase in tensile adhesive strength (RH) to 70 MPa for the slightly softer alloy 2 with a slightly lower hardness of 60 HRc, the tensile adhesive strength (RH) in particular required improvement.

[0061] The exemplary embodiments D and E according to the invention have two coating regions, namely D.1 and D.2, and E.1 and E.2. In the exemplary embodiments, layers D.1 and E.1 form the first coating region 5, and layers D.2 and E.2 form the second coating region 6 of the component 1 according to the invention.

[0062] In Test D, in contrast to Test E, the unalloyed metal powder was processed directly with the metallic alloy powder using high-velocity oxygen-oxygen (HVO) spraying. It is suspected that the lower values ​​for the tensile bond strength (RH) can be attributed to demixing processes during processing of the powder mixture. By separately spraying unalloyed nickel in a proportion of 15 to 50 wt.% in the first coating area of ​​Test E, the highest tensile bond strengths (RH) of more than 90 MPa were measured. The top layer hardness remained moderate at 60 HRC and 58.3 HRc.

[0063] Since the hardness of the first coating area D.1 and E.1 cannot be measured without destroying the coated surfaces, a hardness measurement was carried out on a single-layer coating with a thickness of 0.8 mm consisting of a mixture of alloy No. 2 and 15 wt.% unalloyed nickel.

[0064] This resulted in a hardness of 56 HRc, so that the hardness of the coating of the first coating areas D.1 and E.1 is lower than the hardness of areas D.2 and E.2 with hardnesses of 60 HRc and 58.3 HRc.

[0065] It is expected that due to the optimized tensile adhesive strengths RH in conjunction with the coordinated hardness of the cover layers, tests D and E will provide particularly low-wear bearing surfaces for rolling bearings. Table 4 layer Layer thickness [mm] Base substrate Tensile bond strength RH [MPa] Hardness of the top layer [HRc] A 0,8 Steel 33 63 B 0,8 Steel 45 61 C 0,8 Steel 70 60 D 0,52 Steel 72 60 E 0,52 Steel 91 58,3

[0066] Finally, Fig. 3A schematic sectional view of an embodiment of a component according to the invention in the form of a rail guide 7, which provides bearing surfaces for two cylindrical rollers 8. The bearing surfaces are provided in the rail guide 7 of the cylindrical rollers 8. The rail guide 7 serves as a roller track for the cylindrical rollers 8, which are guided thereby. Such rail guides 7 are used, for example, for aircraft wing flaps. The rolling bearings, consisting of the rail guide 7 for providing the bearing surfaces and the cylindrical rollers 8 as rolling elements, must absorb very high radial forces during flight. The radial forces FR run perpendicular to the axis of rotation of the cylindrical rollers 8.

[0067] Section A from Fig. 3 is in Fig. 4and shows how the radial forces FR occur in the rolling bearing. The rail guides 7 guide the cylindrical rollers 8, which are connected, for example, to a wing flap of an aircraft via a schematically illustrated holder 9. During operation, radial forces can then be transferred via the holder 9 to the cylindrical rollers 8 and thus to the rail guides 7 and their coated bearing surfaces. The radial forces increase the surface pressures in the linear rolling contact of the cylindrical rollers 8 on the bearing surfaces of the rail guide 7. Due to their suitability for very high surface pressures of the bearing surfaces, the rail guides 7 according to the invention can provide particularly good wear and rolling conditions despite high loads in this application.

Claims

1. Component (1) of a rolling bearing with at least one rolling element (3) comprising a base substrate (4) made of metal with at least one surface area which is designed as bearing surface (2) of the rolling bearing with at least one rolling element (3), whereby the at least one surface region of the component (1) comprising a coating which has a first coating region (5) adjacent to the base substrate (4) of the component having a first hardness and a second coating region (6) in contact with at least one rolling element (3) with a second hardness and the first hardness is lower than the second hardness, wherein the first and second coating regions are formed on the base substrate in the direction of the rolling element starting with the first and ending with the second coating region as layers parallel to the base substrate, characterized in that the coating is a metal alloy comprising the following alloying constituents in wt.-%: 8 % ≤ Cr ≤ 18 .5 % , 22,5 % ≤ Mo ≤ 33 % , 2 ,55 % ≤ Si ≤ 3.45 % , optionally 14 % ≤ Ni ≤ 17 % , C < 0,1 % residual Co and unavoidable impurities or 12 % ≤ Cr ≤ 19 % , 28 % ≤ Mo ≤ 36 % , 3 % ≤ Si ≤ 4 % , 0.5 % ≤ Co ≤ 2 % , C < 0,1 % Residual Ni and unavoidable impurities.

2. Component according to claim 1, characterized by the fact that the second hardness of the second coating area (6) of the component (1) is greater than is greater than the hardness of the surface area of the at least one rolling element (3).

3. Component according to claim 1 or 2, characterized in that the coating of the component (1) has a hardness gradient such that the hardness of the coating from the first coating area (5) adjacent to the base substrate of the component (1) to the second coating area (6), which is in contact with the rolling element, rises, optionally continuously or in layers.

4. Component according to any one of claims 1 to 3, characterized in that the first hardness in the first coating area (5) adjacent to the base substrate (4) is at most 60 HRc and the second hardness in the second coating area (6) in contact with the rolling element (3) is at least 57 HRc.

5. Component according to any one of claims 1 to 4, characterized in that the component (1) is a rail guide (7) for receiving at least one cylindrical roller (8) as a rolling element (3) of a rolling bearing and the coated surface region extends partially or at least over the entire surface region over which the cylindrical roller (8) is moved in the rail guide (7).

6. Component according to any one of claims 1 to 6 characterized in that the adhesive tensile strength RH of the coating is more than 70 MPa.

7. Component according to any one of claims 1 to 6, characterized in that the coating in the first coating region (5) has a mixture of at least one metallic alloy and at least one unalloyed metal, the total proportion of unalloyed metal in the coating region (5) being at most 60% by weight, preferably 15 to 50% by weight, and the at least one unalloyed metal being Co, Ni, Cr, Mo, Ta, Cu, Al, In, Zn or a mixture of at least two of the metals mentioned.

8. Component according to any one of claims 1 to 7, characterized in that the coating by high velocity flame spraying or laser powder welding.

9. Component according to any one of claims 1 to 8, characterized in that the coating has a surface roughness Ra of at least 0.1 µm to 2.5 µm, preferably 0.1 µm to 1.2 µm.

10. Component according to any one of claims 1 to 9, characterized in that the coating has a porosity of less than 1.5 %.

11. Component according to one of claims 1 to 11, characterized in that the component (1) is a part of a rolling bearing of a means of transportation, preferably of an airplane.

12. Method of manufacturing a component (1) of a rolling bearing with at least a rolling element with at least one coated surface area according to any one of claims 1 to 11, wherein the coating of the surface portion of the component which is used to provide a bearing surface of a rolling bearing by means of a high-speed flame spraying process. and the coating is applied after the high-speed flame spraying is subjected to at least one machining surface treatment, whereby the first coating area (5) adjacent to the base substrate and the second coating area (6) in contact with the rolling element (3) of the component is produced by high-speed flame spraying of different coating compositions, characterized in that the coating has a metallic alloy with the following alloy components in wt.-%: 8 % ≤ Cr ≤ 18.5 % , 22.5 % ≤ Mo ≤ 33 % , 2 ,55 % ≤ Si ≤ 3.45 % , optionally 14 % ≤ Ni ≤ 17 % , C < 0,1 % , residual Co and unavoidable impurities or 12 % ≤ Cr ≤ 19 % , 28 % ≤ Mo ≤ 36 % , 3 % ≤ Si ≤ 4 % , 0.5 % ≤ Co ≤ 2 % , C < 0,1 % residual Ni and unavoidable impurities.

13. Method according to claim 12, characterized in that the first coating region (5) of the coating adjacent to the base substrate is produced by high velocity flame spraying a mixture of at least one metallic alloy and at least one unalloyed metal, the total part of the unalloyed metal in the coating in some areas is at maximum of 60 wt.-%, preferably 15 wt.-% to 50 wt.-% and the at least one unalloyed metal is Co, Cr, Mo, Ta, Ni, Cu, Al, In, Zn or a mixture of at least two of the metals mentioned.

14. The method according to any one of claims 12 or 13, characterized in that during high-speed flame spraying, the unalloyed metal is sprayed separately to the metallic alloy or is mixed or agglomerated with the at least one metallic alloy prior to spraying before processing in high-speed flame spraying.