SLIDE BEARING ELEMENT

Description

[0001] The invention relates to a plain bearing element comprising a substrate on which a functional layer is arranged, wherein the functional layer has an aC:H:X DLC coating, wherein X stands for at least one element from the group Si, O, N, F.

[0002] Furthermore, the invention relates to a method for producing a plain bearing element comprising the steps of: providing a substrate and depositing a functional layer consisting of an aC:H:X DLC coating on the substrate, wherein X represents at least one element from the group Si, O, N, F.

[0003] It is known to use plain bearing elements in plain bearings that have a DLC layer (DLC = Diamond Like Carbon). For example, DE 60 305 225 T2 describes a sliding device comprising first and second sliding elements that can slide relative to one another on their sliding surfaces, wherein the first sliding element is made of a diamond-like carbon material, the second sliding element is made of an iron-based material; and a lubricant that is applied to the sliding surfaces of the first and second sliding elements.

[0004] DE 10 2005 043 217 A1 describes a bearing pair with a first and a second bearing body, wherein the first bearing body is designed as a bearing seat of a crankshaft or as a piston pin to be mounted in a small connecting rod eye of a connecting rod and the second bearing body is designed as a connecting rod eye or bearing block of an engine housing, which forms a plain bearing with the first bearing body, wherein one of the bearing bodies has a surface coating with dry lubrication properties, which comprises a base layer made of a metal, a metal carbide or a metal alloy and an outer cover layer having dry lubrication properties, and wherein the surface of the other bearing body facing the cover layer has pore-like depressions into which material of the cover layer released by abrasion can be stored.The surface coating is formed by a DLC layer comprising at least two layers, which has a base layer made of a tungsten carbide layer or a chromium nitride layer or a chromium-based alloy and a top layer made of carbon. Dalibon E L et al, "Tribological behavior of DLC films deposited on nitrided and post-oxidized stainless steel by PACVD", Journal of Physics: Conference Series, Institute of Physics Publishing, Bristol, GB, 2012-06-19, Vol. 370, Nr. 1, Pages 1-6 describes the tribological behavior and adhesion of DLC films deposited by PACVD on martensitic stainless steel. Before DLC deposition, the samples are nitrided and partially also post-oxidized.

[0005] The object of the present invention was to provide a sliding bearing element with improved load-bearing capacity.

[0006] The object of the invention is achieved in the sliding bearing element mentioned at the outset in that a connecting layer is arranged between the substrate and the DLC coating, which connecting layer has a first nitride of an element of the substrate.

[0007] Furthermore, the object of the invention is achieved by the method mentioned at the outset, in which it is provided that before the deposition of the functional layer, the substrate is subjected to a nitriding heat treatment in order to thereby produce a connecting layer which has a first nitride of an element of the substrate.

[0008] The advantage here is that the plain bearing element can also be used in a plain bearing or a plain bearing arrangement which comprises the plain bearing element and which is subject to very high loads, such as in a wind turbine as a rotor bearing. In addition to the advantage of lower Herz pressure in the surface of the plain bearing element when stationary, e.g. when the wind turbine is at a standstill, the invention also has the advantage that this structure increases the service life of the plain bearing element. The connecting layer counteracts delamination of the layers of the plain bearing element. It also acts as a support layer for the functional layer which is arranged directly on top of it. This counteracts the disadvantage of plain bearings that when the bearing starts up, static friction must be overcome in order to build up a hydrodynamic film between the bearing components.The layer structure can also minimize static friction, especially when a carbon and silicon-based coating is used, which sustainably extends the service life of the bearing components.

[0009] To further improve these effects, according to an embodiment of the invention, the first nitride may consist of at least 60 wt.% Fe 4 N (gamma nitride).

[0010] According to another embodiment of the invention, the bonding layer can have a thickness between 0.5 µm and 25 µm. Although an effect improving the properties of the plain bearing element can still be observed below 0.5 µm, this effect increases significantly above a layer thickness of 0.5 µm. Above a layer thickness of more than 25 µm, the cost-effectiveness of manufacturing the plain bearing element suffers.

[0011] To further improve the bond strength of the layer system, the invention provides that a diffusion layer is arranged between the bonding layer and the substrate, which diffusion layer has incorporated nitrogen and / or at least one further nitride which is different from the first nitride.

[0012] According to one embodiment, the additional nitride is a nitride from a group comprising aluminum nitrides, titanium nitrides, chromium nitrides, and vanadium nitrides. These metals are frequently used in plain bearing materials, so that the additional nitride can be used to form a nitride from the plain bearing material itself, for example, the substrate, which can improve the adhesion of the bonding layer to the substrate.

[0013] According to a further embodiment of the invention, the diffusion layer can have a thickness between 0.05 mm and 0.7 mm, which can positively influence the compressive stress level in the transition zone from the substrate to the functional layer. This, in turn, also counteracts delamination of the layers.

[0014] According to another embodiment of the invention, the functional layer itself can have a layer thickness of between 3 µm and 60 µm, which means that not only relatively thin DLC layers can be used, but also more resilient plain bearing elements with relatively thick DLC layers, with the improved adhesive strength being particularly evident with the larger layer thicknesses.

[0015] For the reasons mentioned above, according to another embodiment of the invention, it can be provided that the DLC layer is an aC:H:Si - DLC layer, whereby the static friction of the surface of the functional layer can be reduced and thus the service life of the plain bearing element can be extended.

[0016] To further improve the positive properties of this a-C:H:Si - DLC layer, according to one embodiment, it can be provided that the a-C:H:Si is a gradient layer, and preferably according to a further embodiment, it can be provided that in the gradient layer, the concentration of Si changes from a proportion between 45 wt.% and 55 wt.% to a proportion between 1 wt.% and 11 wt.%, the concentration of H changes from a proportion between 25 wt.% and 35 wt.% to a proportion between 0 wt.% and 5 wt.%, and the concentration of C changes from a proportion between 30 wt.% and 50 wt.% to a proportion between 85 wt.% and 100 wt.%. The components of Si, H, and C add up to a total of 100 wt.%.

[0017] It may be advantageous if the gradient of the gradient layer is formed only in a zone with a layer thickness that is between 5% and 70% of the layer thickness of the functional layer. This can provide an interface to the connecting layer that is improved with respect to the adhesion strength of the functional layer on the connecting layer, but it can also provide a layer portion for the actual function of the functional layer in which the properties are at least approximately constant. It is advantageous that this property mix can be represented in a single layer, which allows positive effects with respect to a simplification of the production of the sliding bearing element to be realized. With suitable process control, such a formed functional layer can be deposited in only one process step.

[0018] According to a further embodiment of the invention, the surface of the bonding layer can have an arithmetic mean roughness Ra according to DIN EN ISO 4287:1998 between 0.05 µm and 0.25 µm. This not only improves the adhesion of the functional layer to the bonding layer, but also allows microcavities to be formed in / on the functional layer in which oil can be stored during operation. This, in turn, can lead to a stabilization of the oil film, thereby preventing oil film tear-off.

[0019] According to the preferred embodiments of the invention, the functional layer is a sliding layer or a running-in layer.

[0020] According to one embodiment of the method, the functional layer and / or the bonding layer and / or the diffusion layer can be produced using a PACVD process, as this allows the entire layer structure of a system or system chamber to be implemented, thus significantly reducing the time-consuming handling of the blanks to be coated during production. Furthermore, in conjunction with at least individual features of the layer system, a coating with relatively low layer hardness (< 1700 HV) and high layer thicknesses can be deposited on the substrate.

[0021] It is advantageous if, according to further embodiments of the method, the functional layer is produced at a temperature between 350 °C and 550 °C and / or if the functional layer and / or the connecting layer and / or the diffusion layer is or are produced with a particle current density between the anode and cathode over the entire substrate surface to be coated, which is changed by 0% to a maximum of + / - 5% during the deposition of the functional layer and / or the connecting layer and / or the diffusion layer, since these measures lead to an improvement in the layer properties.

[0022] For a better understanding of the invention, it is explained in more detail with reference to the following figures.

[0023] They show in a highly simplified, schematic representation: Fig. 1A section of a plain bearing element; Fig. 2A device for coating a plain bearing element blank.

[0024] By way of introduction, it should be noted that in the variously described embodiments, identical parts are provided with identical reference symbols or component designations, whereby the disclosures contained in the entire description can be applied mutatis mutandis to identical parts with identical reference symbols or component designations. Furthermore, the positional information chosen in the description, such as top, bottom, side, etc., refers to the directly described and illustrated figure, and in the event of a change in position, these positional information must be applied mutatis mutandis to the new position.

[0025] Fig. 1 shows a section of a plain bearing element 1 for a plain bearing.

[0026] The plain bearing element 1 can, for example, be a thrust ring, a half-shell, a bushing, a segment of a half-shell or a bushing, etc. The plain bearing element 1 is preferably used in a plain bearing that is subjected to increased loads with alternating loads or standstills, such as in a wind turbine. In general, the plain bearing element 1 is preferably used in a plain bearing that is subjected to increased loads and that is operated even with insufficient lubrication or at the beginning of the movement of two friction partners with lubrication, i.e., under mixed friction conditions.

[0027] Unless the plain bearing element 1 is designed as a bushing, the plain bearing typically comprises several (at least two) plain bearing elements. Several or all of the plain bearing elements can be formed by a plain bearing element 1 according to the invention, but at least one of them is designed according to the invention.

[0028] In a non-claimed embodiment, the plain bearing element 1 comprises or consists of a substrate 2, a connecting layer 3, and a functional layer 4. The connecting layer 3 is arranged directly on the substrate 1 and connected thereto, and the functional layer 4 is arranged directly on the connecting layer 3 and connected thereto. The term "connecting layer" is therefore to be understood within the meaning of the invention as meaning that this layer connects the functional layer 4 to another layer or another component of the plain bearing element 1, for example, the substrate 2, which can be designed either in a layered form or as a different three-dimensional component.

[0029] At the Fig. 1In the illustrated embodiment of the sliding bearing element 1 according to the invention, this also has a diffusion layer 5. The diffusion layer 5 is arranged between the connecting layer 3 and the substrate 2, in particular directly on the substrate 2 and connected to the connecting layer 3. In the embodiment according to the invention, the sliding bearing element thus consists of the substrate 2, the diffusion layer 5 arranged directly thereon, the connecting layer 3 arranged directly thereon, and the functional layer 4 arranged directly thereon.

[0030] In the preferred embodiment, the functional layer 4 is a sliding layer or a running-in layer. A running-in layer is a layer that serves to adjust the sliding partner during initial commissioning of the plain bearing element 1. The sliding layer, however, serves to reduce friction between the plain bearing element 1 and the sliding partner during ongoing operation.

[0031] It is also possible for the plain bearing element 1 to have both a sliding layer and a running-in layer arranged (directly) on the sliding layer. In this case, both the sliding layer and the running-in layer can be formed as a functional layer 4, but with a different composition and / or deposited with different process parameters.

[0032] The plain bearing element 1 can also have further layers, such as an anti-fretting layer on the back of the plain bearing element 1 or a further friction-reducing layer on the functional layer 4.

[0033] The substrate 2 consists of a metal-based alloy, in which the metal of the metal base forms the main quantitative component of the alloy. Preferably, the substrate 2 consists of an iron-based alloy, i.e., an alloy with iron as the main component, such as cast iron, or in particular, steel. However, the substrate 2 can also consist of aluminum, nickel, brass, titanium, etc.

[0034] The diffusion layer 5 has interstitially embedded nitrogen and / or at least one further nitride that is different from the first nitride. The further nitride is in particular a nitride from a group comprising aluminum nitrides, titanium nitrides, chromium nitrides, and vanadium nitrides.

[0035] The proportion of incorporated nitrogen in the diffusion layer 5 can be between 0.01 wt. and 0.15 wt. %, in particular between 0.01 wt. and 0.115 wt. %. The (total) proportion of any additional nitride or nitrides present in the diffusion layer 5 can be between 0.1 wt. and 5 wt. %. The remainder to 100 wt. % can be formed by the alloy of the substrate 2.

[0036] The bonding layer 3 contains a nitride of an element of the substrate 2. In the preferred embodiment, this is the gamma nitride of iron Fe 4 N. Alternatively or additionally, titanium nitride (TiN) can also be included as the first nitride. The proportion of the first nitride in the bonding layer 3 can be between 1 wt.% and 55 wt.%. The remainder to 100 wt.% is made up of the element of the substrate 2 from which the first nitride is formed or other elements from the alloy of the substrate 2.

[0037] According to a further embodiment of the plain bearing element, the first nitride can consist of at least 60 wt.% Fe 4 N, in particular of 60 wt.% to 100 wt.%, preferably of 75 wt.% to 100 wt.%, Fe 4 N.

[0038] Functional layer 4 has or consists of an aC:H:X DLC coating. X represents at least one element from the group Si, O, N, and F.

[0039] In the preferred embodiment, the DLC layer is an aC:H:Si - DLC layer, i.e. a silicon-doped, hydrogen-containing, amorphous carbon layer.

[0040] The (total) proportion of at least element X in the functional layer 4 can be between 2 wt.% and 60 wt.%, in particular between 4 wt.% and 50 wt.%. The proportion of hydrogen in the functional layer 4 can be between 0 wt.% and 30 wt.%, in particular between 1 wt.% and 25 wt.%. The remainder to 100 wt.% is formed by C.

[0041] The diffusion layer 5 and / or the connecting layer 3 can be deposited as separate layers on the substrate. In the preferred embodiment of the plain bearing element 1, the diffusion layer 5 and / or the connecting layer 3 are formed from the material of the substrate 2, ie in particular from at least one (metallic) component of the substrate 2, such as in particular iron or at least one element from the group aluminum, titanium, chromium, vanadium, with a further, in particular gaseous, reactant, such as a nitrogen-containing reactant, for example an N 2 / H 2 mixture.

[0042] The functional layer 4 can have a layer thickness 6 between 3 µm and 60 µm. In the embodiment of the functional layer 4 as a running-in layer, the layer thickness 6 can be between 3 µm and 10 µm.

[0043] The connecting layer 3 can have a layer thickness 7 between 0.5 µm and 25 µm, in particular between 1 µm and 15 µm, preferably between 1 µm and 5 µm.

[0044] The diffusion layer 5 can have a layer thickness 8 between 0.05 mm and 0.7 mm, in particular between 0.1 mm and 0.5 mm, preferably between 0.15 mm and 0.3 mm.

[0045] A layer thickness 9 of the substrate 2 depends on the respective area of ​​application of the plain bearing element 1, in particular on its shape.

[0046] According to another embodiment, the functional layer 4, in particular the aC:H:Si layer, can be a gradient layer. At least one of the elements of the functional layer 4 can be contained in the functional layer 4 with an increasing or decreasing concentration gradient toward a surface 10 or toward the underlying connecting layer 3.

[0047] According to one embodiment of the plain bearing element 1, it can be provided that in the gradient layer the concentration of Si changes from a proportion between 45 wt.% and 55 wt.%, in particular from a proportion of 50 wt.%, to a proportion between 1 wt.% and 11 wt.%, in particular to a proportion of 5 wt.%, the concentration of H changes from a proportion between 25 wt.% and 35 wt.%, in particular from a proportion of 30 wt.%, to a proportion between 0 wt.% and 5 wt.%, in particular to a proportion of 0 wt.%, and the concentration of C changes from a proportion between 30 wt.% and 50 wt.%, in particular from a proportion of 40 wt.%, to a proportion between 85 wt.% and 100 wt.%, in particular to a proportion of 95 wt.%. The components of Si, H and C add up to 100 wt.% total.

[0048] The concentration gradient(s) can be formed over the entire layer thickness 6 of the functional layer 4. Preferably, however, the concentration gradient(s) extend only over a portion of the layer thickness 6 of the functional layer 4, in particular over a layer thickness that is between 5% and 70% of the layer thickness 6 of the functional layer 4. Preferably, the concentration gradient(s) begin(s) at the surface 10 and / or a surface 11 of the functional layer 4 that borders the connecting layer 3.

[0049] According to a further embodiment of the plain bearing element 1, a surface 12 of the connecting layer 3, which lies directly against the functional layer 4, can have an arithmetic mean roughness Ra according to DIN EN ISO 4287:1998 between 0.05 µm and 0.25 µm and / or an average roughness depth Rz according to DIN EN ISO 4287:1984 between 0.5 µm and 2 µm. This roughness is transferred at least approximately to the surface 10 of the functional layer 4 (i.e., the surface 10 of the functional layer 4 subject to sliding load), whereby "micro oil pockets" can be formed in the functional layer 4. Oil can be stored in these during operation, thereby stabilizing the oil film and thus better preventing oil film tear. The roughening of the surface 12 of initially approximately Ra 0.1 µm can be achieved by the formation of iron nitrides.

[0050] To manufacture the plain bearing element 1, a substrate 2 is provided, and the individual layers are then deposited on it or generated from it. A PVD (Physical Vapor Deposition) process, a CVD (Chemical Vapor Deposition) process, an APS (Atmospheric Plasma Spray) process, or modifications of these processes can be used for this purpose.

[0051] In the preferred embodiment, the functional layer 4 and / or the connecting layer 3 and / or the diffusion layer 5 is / are produced by means of a PACVD process (Plasma-Assisted Chemical Vapour Deposition).

[0052] For the properties of the functional layer 4, it is further advantageous if it is produced / deposited at a temperature between 350 °C and 550 °C.

[0053] It is also advantageous for the properties of the functional layer 4 if the functional layer 4 and / or the connecting layer 3 and / or the diffusion layer 5 is or are produced with a particle current density between an anode and a cathode of the coating chamber over an entire substrate surface 13 to be coated, which is changed by 0% to a maximum of + / - 5%, in particular up to a maximum of + / - 4%, during the deposition of the functional layer 4 and / or the connecting layer 3 and / or the diffusion layer 5.

[0054] In the preferred embodiment of the method, the nitriding (= production of the connecting layer 3 and optionally the diffusion layer 5) and the coating (= production of the functional layer 4) are carried out in one process in a vacuum chamber 14 of a coating system 15, which consists of Fig. 2 can be seen.

[0055] The gases required for nitriding and producing the functional layer 4, such as nitrogen, hydrogen, argon, acetylene, oxygen, hexamethyldisiloxane, methane, tetrafluoromethane, etc., are introduced into the coating system 15 via corresponding control valves 16. The volume flow depends on the respective process step. One or more substrates 2 is / are placed on a holding element, such as a charging plate 17. The holding element is electrically separated from the vacuum chamber 14. The desired negative pressure for the reactions in the vacuum chamber 14 can be set via a vacuum pump 18. The control valve 16 and the vacuum pump 18 can also be used to clean the vacuum chamber 14 by flushing it once or several times after it has been loaded with the substrates 2. A pulsed charge is introduced into the system via a power supply 19, and the necessary plasma is ignited.

[0056] Since the basic design and operation of such PACVD coating systems are well known, further explanations are unnecessary. Reference is therefore made to the relevant state of the art.

[0057] The nitration of the substrate 2 can be carried out, for example, using the following parameters: Pressure p: 1 mbar to 5 mbar Gas mixture H2 / N2 = 4 / 1 to 1 / 4 Power P = 0.1 kW / m 2 < surface to 2 kW / m 2 < surface Voltage U = 400 V to 700 V

[0058] The coating of the nitrided substrate 2 to produce the DLC layer can be carried out, for example, using the following parameters: Pressure p: 1 mbar to 5 mbar Gases: H2 0 l / h to 600 l / h C2H2 5 l / h to 200 l / h Ar 10 l / h to 300 l / h HMDSO 5 g / h to 300 g / h Power P = 50 W / m2< to 1000 W / m2< Voltage U = 300 V to 600 V Coating time of the gradient layer between 0.1 hours and 2.5 hours

[0059] In the preferred embodiment of the method, the invention therefore relates to a combination of a nitriding heat treatment (= nitriding by means of heat treatment), in particular plasma nitriding, and a PACVD coating, in particular an aC:H:Si - DLC coating, for plain bearing elements 1 subject to high loads. This can reduce the static friction between the plain bearing element 1 and a component mounted thereon, thereby sustainably extending the service life of the bearing components. This can be used to produce, among other things, plain bearing elements 1 for wind turbines. In addition to the effects described above, the DLC coating can impart greater wear resistance and / or corrosion resistance to the plain bearing element 1, in particular when applied to a steel substrate. Furthermore, the DLC coating is water-repellent, chemically inert, and electrically non-conductive.Due to the water and oil-repellent properties, sliding friction can cause the oil film to break down, which can lead to surface damage. This in itself speaks against the use of such a plain bearing element 1 in highly loaded plain bearings. It is therefore all the more surprising that the plain bearing element 1 according to the invention nevertheless exhibits better overall properties.

[0060] Known DLC coatings with higher hardness generally exhibit higher lateral compressive stresses in the interface. This can lead to delamination of the layer under higher external loads. This disadvantage is eliminated with the invention by combining the bonding layer 3 and the functional layer 4, in particular by combining the processes of nitriding and coating, particularly of steel surfaces, with the focus on keeping the lateral stresses as low as possible while simultaneously achieving higher wear protection properties and low friction coefficients. The protective effect of the coating can be achieved specifically for the area of ​​mixed friction when starting or stopping the plain bearing element 1.

[0061] By nitriding with the above-mentioned method, a complete, compact and dense connecting layer 3 with a porosity of less than 25%, in particular less than 15%, can be achieved.

[0062] Nitriding the substrate prior to coating creates residual compressive stresses in the substrate surface 13. This provides better support for the subsequent coating. Furthermore, the residual compressive stress increases the fatigue strength of the plain bearing element 1. By producing the aC:H:Si functional layer 4 using PACVD technology, the DLC layer has a relatively low layer hardness (< 1700 HV). Furthermore, the functional layer 4 can be deposited on the substrate 2 with a relatively high layer thickness 6. This can be achieved, in particular, by doping with silicon and / or a low temperature during the deposition of the functional layer 4.

[0063] The functional layer 4 preferably has a thin (1 µm to 5 µm) intermediate layer with (high) proportions of silicon (between 10 wt.% and 500 wt.%), hydrogen (between 0 wt.% and 30 wt.%) and carbon (between 30 wt.% and 85 wt.%) (the components of the intermediate layer add up to 100 wt.%). As described above, the intermediate layer can be a chemically graded layer that is initially produced with higher silicon contents and lower carbon contents. Over the coating time, the silicon content is reduced and the carbon content is increased until the composition of the overlying coating, i.e. the actual coating, is reached.

[0064] The main part of the coating can consist of carbon, hydrogen, oxygen and silicon and can have a layer thickness of 3-50 µm, for example.

[0065] Preferably, the layer thickness of the intermediate layer and the layer thickness of the main part of the coating together result in the layer thickness 6 of the functional layer 4.

[0066] As previously stated, it is beneficial for the coating result if a constant particle flux density is maintained across the entire component surface from anode to cathode at the aforementioned coating components. This is achieved through appropriate process control of the plasma power and gas supply, appropriate charging, etc.

[0067] The substrates 2 are connected as cathode.

[0068] The maximum compressive stress level due to nitriding can be between 250 MPa and 450 MPa, for example, between 300 MPa and 350 MPa for material 1.7225; between 250 MPa and 700 MPa, for example, between 300 MPa and 600 MPa for material 1.8519; and between 500 MPa and 850 MPa, for example, between 550 MPa and 750 MPa for material 1.8550. Residual stresses are measured using X-ray diffraction according to DIN EN 15305:2009.

[0069] To evaluate the invention, the following embodiments were carried out, among others. Example 1 (not according to the invention))

[0070] Coating of sleeves for use in mechanical engineering made of material 1.7225 Parameters o Nitriding □ Pressure p = 2 mbar □ Gas mixture: H 2 / N 2 = 150 l / h / 100 l / h □ Power: P = 300 W / m 2< □ Voltage: U = 480 V o DLC coating □ Pressure: 2 mbar □ Gases H 2 = 320 l / h C 2 H 2 = 70 l / h Ar = 120 l / h HMDSO = 50 g / h N 2 = 25 l / h □ Power P = 220 W / m 2< □ Voltage: 390 V Results o Layer thickness □ Intermediate layer: 2.2 µm □ Functional layer: 3.8 µm o Layer hardness: 1486 HV o Layer adhesion: HF1 o Nitriding depth: NHD = 0.25 mm o Compound layer thickness: 1 µm o Core hardness: 335 HV o Friction coefficient on the tribometer: µ avg = 0.08 (pin disc tribometer; dry; friction partner 100Cr6 - uncoated µ = 0.65)

[0071] The DLC coating had the following composition (values ​​in wt% and measured by glow discharge spectroscopy GDOES) Intermediate layer: 7% H / / 2.5% O / / 35% Si / / balance C Functional layer: 5% H / / 2.5% O / / 18% Si / / balance C Example 2- Coating of discs for use in mechanical engineering made of material 1.7225

[0072] Parameters o Nitriding □ Pressure p = 3 mbar □ Gas mixture: H 2 / N 2 = 90 / 90 l / h □ Power: P = 500 W / m 2< □ Voltage: U = 510 V o DLC coating □ Pressure p = 2.7 mbar □ Gases H 2 = 100 l / h C 2 H 2 = 45 l / h Ar = 45 l / h HMDSO = 20 g / h □ Power P = 180 W / m 2< □ Voltage: 400 V Results o Layer thickness □ Diffusion layer: 1.5 µm □ Functional layer: 6.5 µm o Layer hardness: 1250 HV o Layer adhesion: HF1 o Nitriding hardness depth: NHD = 0.17 mm o Compound layer thickness: 4 µm o Core hardness: 330 HV o Friction coefficient on the tribometer: µ avg = 0.05 (pin disc tribometer; dry; friction partner 100Cr6 - uncoated µ = 0.65) The DLC coating had the following composition (values ​​in wt% and measured by glow discharge spectroscopy GDOES): Diffusion layer: 4% H / / 1% N / / 2% O / / 40% Si / / balance C Functional layer: 3% H / / 6% N / / 2% O / / 22% Si / / balance C

[0073] The embodiments show or describe possible design variants of the plain bearing element 1, whereby combinations of the individual design variants are also possible.

[0074] For the sake of clarity, it should finally be noted that, for a better understanding of the structure of the plain bearing element 1, it is not necessarily shown to scale. For the purposes of this description, a layer is also understood to mean a layer thickness range of the original substrate 2 that has been nitrided or generally treated and thus has a different composition compared to the original substrate 2. The layer thickness 9 of the original substrate 2 before nitriding or treatment is therefore reduced by the layer thickness of this layer. Instead of a layer, one can therefore also speak of a zone. Reference symbol list

[0075] 1Sliding bearing element 2Substrate 3Connecting layer 4Functional layer 5Diffusion layer 6Layer thickness 7Layer thickness 8Layer thickness 9Layer thickness 10Surface 11Surface 12Surface 13Substrate surface 14Vacuum chamber 15Coating system 16Control valve 17Charging plate 18Vacuum pump 19Power supply

Claims

1. A sliding bearing element (1) comprising a substrate (2), a diffusion layer (5) arranged directly thereon and a functional layer (4), wherein the functional layer (4) has an a-C:H:X DLC coating, wherein X stands for at least one element from the group of Si, O, N, F, and the diffusion layer (5) has embedded nitrogen and / or at least one nitride which is different from a first nitride, wherein the first nitride is a nitride of an element of the substrate (2), characterized in that a compound layer (3) comprising the first nitride of the element of the substrate (2) is arranged between the diffusion layer (5) and the DLC coating, wherein the compound layer (3) is arranged directly on the diffusion layer (5) and the functional layer (4) is arranged directly on the compound layer.

2. The sliding bearing element (1) according to claim 1, characterized in that at least 60 wt.% of the first nitride consists of Fe4N (gamma nitride).

3. The sliding bearing element (1) according to claim 1 or 2, characterized in that the compound layer (3) has a layer thickness (7) of between 0.5 µm and 25 µm.

4. The sliding bearing element (1) according to one of claims 1 to 3, characterized in that the further nitride is a nitride from a group comprising nitrides of aluminum, nitrides of titanium, nitrides of chromium, nitrides of vanadium.

5. The sliding bearing element (1) according to one of claims 1 to 4, characterized in that the diffusion layer (5) has a layer thickness (8) of between 0.05 mm and 0.7 mm.

6. The sliding bearing element (1) according to one of claims 1 to 5, characterized in that the functional layer (4) has a layer thickness (6) of between 3 µm and 60 µm.

7. The sliding bearing element (1) according to one of claims 1 to 6, characterized in that the DLC layer is an a-C:H:Si DLC layer.

8. The sliding bearing element (1) according to claim 7, characterized in that the a-C:H:Si DLC layer is a gradient layer.

9. The sliding bearing element (1) according to claim 8, characterized in that the concentration of Si in the gradient layer changes from a proportion of between 45 wt.% and 55 wt.% to a proportion of between 1 wt.% and 11 wt.%, the concentration of H changes from a proportion of between 25 wt.% and 35 wt.% to a proportion of between 0 wt.% and 5 wt.%, and the concentration of C changes from a proportion of between 30 wt.% and 50 wt.% to a proportion of between 85 wt.% and 100 wt.%.

10. The sliding bearing element (1) according to claim 8 or 9, characterized in that the gradient of the gradient layer is formed in a zone with a layer thickness which is between 5% and 70% of the layer thickness (6) of the functional layer (4).

11. The sliding bearing element (1) according to one of claims 1 to 10, characterized in that the surface (12) of the compound layer (3) has an arithmetic mean roughness value Ra according to DIN EN ISO 4287:1998 of between 0.05 µm and 0.25 µm.

12. The sliding bearing element (1) according to one of claims 1 to 11, characterized in that the functional layer (4) is a sliding layer or a running-in layer.

13. A method for producing a sliding bearing element (1) according to one of claims 1 to 12, comprising the steps of: providing a substrate (2), forming a diffusion layer (5) on the substrate (2) by a nitriding heat treatment in which nitrogen is embedded and / or at least one further nitride is formed which is different from a first nitride which is a nitride of an element of the substrate (2), and depositing a functional layer (4) of an a-C:H:X DLC coating, wherein X stands for at least one element from the group of Si, O, N, F, characterized in that during the nitriding heat treatment, after the formation of the diffusion layer (5) and before the deposition of the functional layer (4), a compound layer (3) is produced by the nitriding heat treatment which compound layer (3) comprises the first nitride of the element of the substrate (2).

14. The method according to claim 13, characterized in that the functional layer (4) and / or the compound layer (3) and / or the diffusion layer (5) is or are produced by means of a PACVD process.

15. The method according to claim 13 or 14, characterized in that the functional layer (4) is produced at a temperature of between 350 °C and 550 °C.

16. The method according to claim 14 or 15, characterized in that the functional layer (4) and / or the compound layer (3) and / or the diffusion layer (5) is or are produced with a particle current density between anode and cathode over the entire substrate surface (13) to be coated, which is changed by 0 % to a maximum of + / - 5 % during the deposition of the functional layer (4) and / or the compound layer (4) and / or the diffusion layer (5).