SUBSTRATE WITH A MOLYBDENUM NITRIDE LAYER SYSTEM, AND COATING METHOD FOR PRODUCING A LAYER SYSTEM

Abstract

A substrate having a multilayer coating system in the form of a surface coating, which has an outer cover layer comprising amorphous carbon, and a coating process for producing a substrate. At least a first Mo.sub.aN.sub.x support layer is provided between the substrate and the cover layer, which support layer has a nitrogen content x, referred to an Mo content a, which is in the range of 25 at %≤x≤55 at %, with x+a=100 at %.

Claims

1. A substrate having a multilayer coating system in the form of a surface coating, which has an outer cover layer comprising amorphous carbon, characterized in that at least a first Mo.sub.aN.sub.x support layer is provided between the substrate and the cover layer, which support layer has a nitrogen content x, referred to an Mo content a, which is in the range of 25 at %≤x≤55 at %, with x+a=100 at %.

2. The substrate according to claim 1, wherein the nitrogen content x of the first Mo.sub.aN.sub.x support layer is in the range of 30 at %≤x≤53 at %, preferably at about 50 at %.

3. The substrate according to claim 1, wherein the coating system comprises at least a second Mo.sub.bN.sub.y support layer between the substrate and the first Mo.sub.aN.sub.x support layer and/or between the first Mo.sub.aN.sub.x support layer and the outer cover layer, wherein, referred to a Mo content b of the second Mo.sub.bN.sub.y support layer, a nitrogen content y is in the range from 35 at %≤y≤45 at %, with y+b=100 at %, preferably at 40 at %.

4. The substrate according to claim 1, wherein a plurality of respectively identical or different first Mo.sub.aN.sub.r support layers is provided between the substrate and the outer cover layer of amorphous carbon and/or wherein a plurality of respectively identical or different second Mo.sub.bN.sub.y support layers is provided between the substrate and the outer cover layer of amorphous carbon and/or wherein the first Mo.sub.aN.sub.x support layer and/or the second Mo.sub.bN.sub.y support layer contains a proportion of metallic Mo, wherein a phase mixture of Mo and Mo.sub.2N in the first MoN.sub.x support layer and a phase mixture of Mo and Mo.sub.2N in the second Mo.sub.bN.sub.y support layer, respectively, is adjusted by adjusting a nitrogen content x and y, respectively, between 5 at % and 20 at %, with x+a=100 at % and y+b=100 at % and/or wherein the first Mo.sub.aN.sub.x support layer and/or the second Mo.sub.bN.sub.y support layer are composed of pure Mo.sub.2N phases and their phase mixtures β-Mo.sub.2N and γ-Mo.sub.2N, and/or of Mo.sub.2N/MoN phase mixtures and/or of pure MoN phases, in particular cubic MoN phases and/or hexagonal δ-MoN phases or phase mixtures, the γ-Mo.sub.2N and the pure hexagonal phase of δ-MoN being particularly preferred.

5. The substrate according to claim 1, wherein the first Mo.sub.aN.sub.x support layer and/or the second Mo.sub.bN.sub.y support layer additionally comprises one or more elements from the group consisting of [Ag, Cr, Ti, Cu, Al, Si, B, O, C] and/or an element from the 4th, 5th or 6th group of the periodic table of the elements, and wherein the first Mo.sub.aN.sub.x support layer and/or the second Mo.sub.bN.sub.y support layer comprises at least a layer of the composition (Mo.sub.xM.sub.z).sub.c(N.sub.uC.sub.vO.sub.w).sub.d, acting as a support layer, wherein M comprises at least one of the elements of the 4th to 6th group of the periodic table, and/or one of the elements Si, B, Al, Cu, Ag, with x+z+u+v+w=100 at %, and c/d=3, wherein 25 at %≤x≤55 at % and 0≤z≤20 at %, 0≤v≤5 at % and 0≤w≤5 at %.

6. The substrate according to claim 1, wherein the coating system additionally comprises an adhesive layer provided on a surface of the substrate and/or on a surface of the first Mo.sub.aN.sub.x support layer and/or on a surface of the second Mo.sub.bN.sub.y support layer, which adhesive layer is alloyed in particular with one or more elements from the group consisting of [C, N, O] and/or wherein the adhesive layer comprises, except for impurities, one or more elements of the 4th, 5th or 6th group of the periodic table of the elements, in particular also comprising one of the elements Cr, Ti, Cu, Al, Mo.

7. The substrate according to claim 1, wherein the coating system additionally comprises an intermediate layer under the first Mo.sub.zN.sub.x support layer and/or under the second Mo.sub.bN.sub.y support layer, in particular single-phase metal nitrides, metal carbides as well as metal carbonitrides and/or phase mixtures of metal nitrides, metal carbides and metal carbonitrides, wherein the intermediate layer comprises in particular a single-phase Cr.sub.2N or CrN layer or a phase mixture of CrN and Cr.sub.2N and/or wherein the first Mo.sub.aN.sub.x support layer and/or the second Mo.sub.bN.sub.y support layer and/or the intermediate layer is a gradient layer referred to the chemical composition.

8. The substrate according to claim 1, wherein a thickness d of the first Mo.sub.aN.sub.x support layer and/or of the second Mo.sub.bN.sub.y support layer and/or of the intermediate layer is in the range of 0.05 μm≤d≤50 μm, preferably in the range of 0.03 μm≤d≤30 μm, especially in the range of 0.2 μm≤d≤μm, or in the range of 0.3 μm≤d≤10 μm.

9. The substrate according to claim 1, wherein the outer cover layer comprising the amorphous carbon is an amorphous carbon layer of the a-C type, an amorphous carbon layer of the a-C:X type doped with an element X, a tetrahedral amorphous carbon layer of the ta-C:X type doped with an element X, an amorphous carbon layer of the a-C:Me type doped with a metal, a tetrahedral amorphous carbon layer of the ta-C:Me type doped with a metal, or an amorphous carbon layer of the a-C:H:Me type doped with a metal and hydrogen or a tetrahedral amorphous carbon layer of the ta-C:H:Me type doped with a metal and hydrogen and/or wherein X is preferably an element from the group of elements consisting of [F, Cl, B, N, O, Si] and/or wherein Me comprises one or more elements of the 4th, 5th or 6th group of the periodic table of the elements and preferably comprises one of the elements Al, Mo, Cr, Ti, W, Al, Cu.

10. The substrate according to claim 9, wherein the cover layer is of two or more layers each comprising an amorphous carbon layer of the a-C type, or of the a-C:X type, or of the ta-C:X type, or of the a-C:Me type, or of the ta-C:Me type, or of the a-C:H:Me type, or of the ta-C:H:Me type and/or wherein the cover layer and/or a layer comprising a gradient layer is an amorphous carbon layer of the a-C type, or of the a-C:X type, or of the ta-C:X type, or of the a-C:ME type, or of the ta-C:Me type, or of the a-C:H:Me type, or of the ta-C:H:Me type and/or wherein two different layers of the cover layer have a different sp.sup.3/sp.sup.2 ratio and/or wherein in a gradient layer a sp.sup.3/sp.sup.2 ratio varies over a thickness of the gradient layer.

11. The substrate according to claim 10, wherein a thickness Dd of the cover layer and/or of a layer of the cover layer is in the range of 0.05 μm≤Dd≤50 μm, preferably in the range of 0.05 μm≤Dd≤30 μm, especially in the range of 0.1 μm≤Dd≤20 μm, or in the range of 0.5 μm≤Dd≤10 μm, preferably in the range of 1 μm≤Dd≤5 μm, particularly preferably at about 2 μm and/or wherein a hardness Hd of the cover layer is in a range of 8 GPa≤Hd≤80 GPa, especially in the range of 10 GPa≤Hd≤70 GPa, or in the range of 25 GPa≤Hd≤60 GPa, particularly preferably at about 50 GPa.

12. The substrate according to claim 1, wherein a total thickness Gd of the coating system is in the range of 0.05 μm≤Gd≤100 μm, preferably in the range of 0.5 μm≤Gd≤50 μm, especially in the range of 1 μm≤Gd≤10 μm, particularly preferably at about 4 μm and/or wherein a ratio of the thickness Dd of the cover layer to the total thickness of the Gd of the entire coating system is in the range of 1%≤(Dd/Gd)≤1000%, preferably in the range of 10%≤(Dd/Gd)≤500%, especially in the range of 20%≤(Dd/Gd)≤200% and particularly preferably in the range of 40%≤(Dd/Gd)≤120% and/or wherein a ratio of the hardness Hd of the cover layer (3) to the hardness Hs of the entire support layer is in a range between (Hd/Hs)=1:5 to (Hd/Hs)=4:1, preferably in the range between (Hd/Hs)=1:2 to (Hd/Hs)=3:1, in particular in the range of (Hd/Hs)=1:1.5 to (Hd/Hs)=2:1.

13. The substrate according to claim 1, wherein the substrate is in particular a component of a component subject to wear and/or friction, especially a component of a motor vehicle or of an internal combustion engine, in particular a piston, or a piston ring, a valve, a valve disk, or another component of an internal combustion engine or a tool, such as a cutting tool, a forming tool, a machining tool, or another tool subject to wear and/or friction.

14. A coating process for producing a coating system on a substrate according claim 1, wherein the coating process comprises a PVD process, a CVD process, a PA-CVD process, a sputtering process, preferably a HIPMS sputtering process, in particular a filtered or unfiltered are coating process, or a combination or hybrid process comprising at least one of the aforementioned coating processes, and/or wherein the coating of the entire coating system is deposited on the substrate by of the unfiltered or filtered arc evaporator.

15. The coating process according to claim 14, wherein the substrate is treated for cleaning of the substrate surface and/or a surface of the first Mo.sub.aN.sub.x support layer and/or a surface of the second Mo.sub.bN.sub.y support layer prior to coating by argon ions and/or hydrogen with an ion cleaning using an Arc Enhanced Glow Discharge AEGD technology, wherein preferably additionally an ion treatment is carried out for example with Cr ions or Mo ions.

Description

[0083] Further preferred embodiments of the invention are indicated in the drawing. There are shown:

[0084] FIG. 1a-1d: First embodiments of layer architectures according to the invention, which comprise only molybdenum or molybdenum support layers between the cover layer of amorphous carbon and the substrate.

[0085] FIG. 2a-2e: A second conception of a layer architecture according to the invention, wherein at least one adhesive layer of a material other than molybdenum is additionally provided between the cover layer of amorphous carbon and the substrate.

[0086] FIG. 3a-3c: Further developments according to the invention of coating systems with additional CrN intermediate layers.

[0087] FIG. 4a-4b: Coating systems according to the invention with multilayer coatings.

[0088] FIG. 5a-5b: Two further embodiments having at least a first and a second support layer.

[0089] FIG. 6: The course of hardness and Young's modulus for a special coating system of the invention as an example.

[0090] FIG. 1a to FIG. 1d exemplarily show some preferred embodiments of the present invention with simple layer structures, which comprise only molybdenum Mo or molybdenum support layers MoN between the cover layer of amorphous carbon and the substrate. Such layers are very simple, relatively fast and thus also inexpensive to produce and are therefore particularly suitable for coatings on low-cost mass-produced products. Above all because, apart from the production of the cover layer 3, in principle only one Mo evaporation source needs to be provided for the production of the other parts of the coating system 2 in addition to the process gas nitrogen, which means a minimal effort with regard to the equipment of the coating chamber and greatly simplifies the coating process itself.

[0091] All substrates 1 according to the invention of the embodiments according to FIG. 1a to 1d are provided with a multilayer coating system 2 in the form of a surface coating with an outer cover layer 3 comprising an amorphous carbon. Between the substrate 1 and the cover layer 3, at least exactly one first Mo.sub.aN.sub.x support layer 4 is provided in each case, which, referred to a Mo content a, has a nitrogen content x which is in the range of 25 at %≤x≤55 at %, with x+a=100 at %.

[0092] At this point, it should again be indicated that when, for the sake of simplicity, in the context of the present application, reference is made to a “MoN layer” or simply to “MoN”, this means a chemical composition or a layer comprising at least Mo and N of any composition relating to Mo and N. Thus, within the meaning of this application, MoN or a MoN layer may be, for example, in particular a first Mo.sub.aN.sub.x support layer 4 or a second Mo.sub.bN.sub.y support layer 5 or any other layer or composition of the MoN type. Thus, MoN is to be understood as a kind of generic term for the molybdenum-nitrogen layers or molybdenum-nitrogen compositions defined in this application.

[0093] In the simple embodiments of FIG. 1a to FIG. 1d, the MoN layers shown are each first Mo.sub.aN.sub.x support layers 4.

[0094] The outer cover layer 3 comprising the amorphous carbon can be any type of an amorphous carbon layer. For example, a very simple amorphous carbon layer of the a-C type, or an amorphous carbon layer of the a-C:X type doped with an element X, or a tetrahedral amorphous carbon layer of the ta-C:X type doped with an element X, an amorphous carbon layer of the a-C:Me type doped with a metal, a tetrahedral amorphous carbon layer of the ta-C:Me type doped with a metal, or an amorphous carbon layer of the a-C:H:Me type doped with a metal and hydrogen, or, e.g. a tetrahedral amorphous carbon layer of the ta-C:H:Me type doped with a metal and hydrogen. The cover layer 3 could also be designed as a multilayer coating formed from one or more aforementioned amorphous carbon layer types, or be designed in the form of one or more gradient layers or be designed in some other way as an amorphous carbon layer, as indicated in the context of the description and claims of this application.

[0095] The thicknesses or thickness ratios and hardnesses or hardness ratios of the individual layers of the coating system 2, as represented schematically in the figures of the present application, may assume any suitable values as explained in the present description and the claims. Thus, in particular, the layer thicknesses or layer thickness ratios of the individual layers of the shown coating systems 2 or of the substrate 1 represented in all figures are, of course, to be understood as purely schematic and do not reflect actual thicknesses or actual layer thickness ratios.

[0096] The substrate can be in particular a component of a component subject to wear and/or friction, especially a component of a motor vehicle or of an internal combustion engine, in particular a piston, or a piston ring, a valve, a valve disk, or another component of an internal combustion engine or also a tool, such as a cutting tool, a forming tool, a machining tool, or another tool subject to wear and/or friction, or any other substrate which can advantageously be provided with a coating of the present invention.

[0097] Thus, the previously made comments on the outer cover layer 3 of amorphous carbon, on the substrate 1 and on the thicknesses and thickness ratios, as well as the hardnesses and hardness ratios of the layers of the coating system 2 also apply to all other special coating systems of the invention discussed below and therefore, need not to be explicitly repeated again in the discussion of the following figures FIG. 2a to FIG. 2e, FIG. 3a to FIG. 3 c, or FIG. 4a and FIG. 4b, as well as for the coating systems in FIG. 5a and FIG. 5b. Therefore, in the following, in the discussion of further coating systems of the invention, for the sake of simplicity, only a cover layer 3 or a substrate 4 will be referred to in each case, without having to specify them in any further detail.

[0098] Back to the specific embodiments according to FIG. 1a to FIG. 1d, the simplest layer type of a coating system 2 of the present invention is represented in an exemplary manner on the basis of FIG. 1a, which coating system is characterized by the fact that exactly one first Mo.sub.aN.sub.x support layer 4, and no further layer, is provided between the cover layer 3 and the substrate 1. This type of layer, which can be produced simply and inexpensively, is particularly well suited if there are no particularly high requirements for the adhesion of the first Mo.sub.aN.sub.x support layer 4 on the substrate or of the cover layer 3 on first Mo.sub.aN.sub.x support layer 4 in the application of the coated substrate 1.

[0099] In the coating system 2 of FIG. 1b, a Mo adhesive layer is additionally provided between the substrate 1 and the first Mo.sub.aN.sub.x support layer 4 in comparison with that of FIG. 1a. In doing so, in particular the adhesion of the first Mo.sub.aN.sub.x support layer 4 on the substrate is improved.

[0100] In the further variant according to FIG. 1c, the adhesive layer 6 of Mo is provided between the cover layer 3 and the first Mo.sub.aN.sub.x support layer 4, so that primarily the adhesion of the cover layer to the underlying coating system 2 with substrate 1 is improved.

[0101] Then, the coating system according to FIG. 1d combines the advantages of the embodiments according to FIG. 1b and FIG. 1c by providing an adhesive layer 6 of molybdenum both between the cover layer 3 and the first Mo.sub.aN.sub.x support layer 4, and between the first Mo.sub.aN.sub.x support layer 4 and the substrate 1, so that a very good adhesion of all layers involved to each other as well as a good adhesion of the first Mo.sub.aN.sub.x support layer 4 on the substrate 1 is achieved.

[0102] Systemic further developments of the simple embodiments according to FIG. 1a to FIG. 1d are schematically represented on the basis of FIG. 2a to FIG. 2b. In these embodiments, the adhesive layers 6 according to FIG. 1a to FIG. 1b are partially or completely replaced by adhesive layers of another metal, in the present embodiments of FIG. 2a to FIG. 2b exemplarily by adhesive layers of Cr. This makes the production of the coating system 2 somewhat more complex, since the coating chamber must additionally be equipped with at least one metal evaporation source, in this case a Cr evaporation source, and makes the process control in the coating process somewhat more complex. However, the layer systems can be adapted even more flexibly to special requirements to which the substrate is subjected in the operating state by the substitutional, additional, or alternative use of adhesion layers of metal such as Cr instead of adhesion layers of Mo only.

[0103] In the embodiment according to FIG. 2a, in comparison to that of FIG. 1b, the adhesive layer 6 of Mo between the first Mo.sub.aN.sub.x support layer 4 and the substrate 1 is replaced by an adhesive layer 6 of Cr, while in the embodiment of FIG. 2b, the adhesive layer 6 between the cover layer 3 and the first Mo.sub.aN.sub.x support layer 4 is replaced by an adhesive layer 6 of Cr. In the embodiment according to FIG. 2c, in comparison to that of FIG. 1d, even both adhesive layers 6 are of Cr, both the one between the first Mo.sub.aN.sub.x support layer 4 and the substrate 1, and the one between the cover layer 3 and the first Mo.sub.aN.sub.x support layer 4 are replaced by an adhesive layer 6 of Cr.

[0104] In FIG. 2d and FIG. 2e, two types of adhesive layers 6 are provided in each case, namely an adhesive layer 6 of Mo and an adhesive layer 6 of Cr. In FIG. 2d, an adhesive layer 6 of Cr is provided between the cover layer 3 and the first Mo.sub.aN.sub.x support layer 4, and an adhesive layer 6 of Mo is provided between the first Mo.sub.aN.sub.x support layer 4 and the substrate 1, while in the embodiment of FIG. 2e, an adhesive layer 6 of Mo is provided between the cover layer 3 and the first Mo.sub.aN.sub.x support layer 4, and an adhesive layer 6 of Cr is provided between the first Mo.sub.aN.sub.x support layer 4 and the substrate 1. Thus, the two embodiments according to FIG. 2d and FIG. 2e are two further advantageous modifications of FIG. 1d, between which the person skilled in the art can select in practice depending on the requirements by the specific application of the coated substrate 1.

[0105] On the basis of FIG. 3a to FIG. 3c, further developments of the coating systems 2 according to the special embodiments previously described above are schematically sketched, which comprise an intermediate layer 7 between the cover layer 3 and the substrate 1 in addition to the at least one first Mo.sub.aN.sub.x support layer 4 and in addition to the at least one adhesive layer 6.

[0106] As already explained in more detail above, an intermediate layer 7, not only in the case of, but in particular in the case of the use of soft steels for the substrate 1, can additionally be provided advantageously in the coating system 2, wherein an additional intermediate layer 7 can be provided particularly preferably under a MoN support layer, i.e. e.g. under a first Mo.sub.aN.sub.x support layer 4 or a second Mo.sub.bN.sub.y support layer 5, very particularly preferably in the direction towards the substrate 1.

[0107] Due to the integration of one or more additional intermediate layers 7 between the cover layer 3 and the substrate 1, inter alia, layer properties such as the stability, hardness, above all also the temperature resistance, the adaptation to impact loads or also the ductility etc. can be individually adapted or further improved in a coating system 2 according to the invention depending on the application and substrate.

[0108] In the embodiments according to FIG. 3a to FIG. 3c, only one and in addition a relatively simply constructed intermediate layer 7 of the composition CrN is provided in each case. The Young's modulus and the hardness of the partial layers or partial areas of the coating system preferably increase in the direction towards the cover layer. In particular, the Young's modulus and the hardness of the intermediate layer 7 are particularly preferably smaller than the Young's modulus and the hardness of the first Mo.sub.aN.sub.x support layer 4 and/or the second Mo.sub.bN.sub.y support layer 5 and/or the cover layer 3. This relationship will be illuminated in more detail below on the basis of FIG. 6. In practice, the person skilled in the art can select from a large number of different types of intermediate layers 7 for the production of a coating system 2 according to the invention, such as from intermediate layers comprising single-phase metal nitrides and/or metal carbides as well as metal carbonitrides and/or phase mixtures of metal nitrides, metal carbides and metal carbonitrides, wherein the intermediate layer 7 can in particular be a single-phase Cr.sub.2N or a single-phase CrN layer, as in the embodiments of FIG. 3a to FIG. 3c, or can comprise a phase mixture of CrN and Cr.sub.2N and can otherwise have special properties and embodiments as already described in detail elsewhere in the context of this application.

[0109] In FIG. 3a, an additional intermediate layer 7 of CrN is deposited between the adhesive layer 6 of Cr provided on the substrate 1 and the first Mo.sub.aN.sub.x support layer 4 provided under the cover layer 3. Thus, the embodiment of FIG. 3a can be understood as a development and further improvement of the embodiment according to FIG. 2a.

[0110] In FIG. 3b, an additional intermediate layer 7 of CrN is also deposited between the adhesive layer 6 of Cr provided on the substrate 1 and under the first Mo.sub.aN.sub.x support layer 4, wherein in this embodiment, in comparison to FIG. 3a, an adhesive layer 6 is additionally provided between the cover layer 3 and the first Mo.sub.aN.sub.x support layer 4. Thus, the embodiment of FIG. 3b can be understood as a development and further improvement of the embodiment according to FIG. 3a or also as a further improvement of the embodiment according to FIG. 2c.

[0111] The embodiment according to FIG. 3c, on the other hand, can be understood as a development of the embodiment of FIG. 2e. In the embodiment of FIG. 3c, in comparison to FIG. 2e, an intermediate layer of CrN is additionally deposited between the adhesive layer 6 of Cr provided on the substrate 1 and the first Mo.sub.aN.sub.x support layer 4.

[0112] Although it would be possible to present a large number of further embodiments of coating systems 2 according to the invention on the basis of specific embodiments, for the sake of clarity and the required brevity of the presentation, only one important further type of coating systems 2 according to the invention will be briefly presented in detail on the basis of FIG. 4a and FIG. 4b.

[0113] In the case of the coating systems 2 according to the present invention represented schematically on the basis of FIG. 4a and FIG. 4b, these are coating systems which additionally comprise multilayer coatings 71.

[0114] In the context of this application, a multilayer coating 71 is to be understood as such a sublayer of the coating system 2 which comprises a plurality of individual different partial layers 4, 5, 6, 7, the individual thicknesses of which are each relatively or rather small in comparison to the thickness of the entire coating system 2 or in comparison to the thickness of most other partial layers of the coating system 2 or in comparison to the thickness of the entire multilayer coating 71.

[0115] In the embodiment of FIG. 4a, as a development of the simple embodiment according to FIG. 2c, instead of a simple first Mo.sub.aN.sub.x support layer 4, a multilayer coating 71 is provided between the two adhesive layers 6 of Cr, which comprises in alternating sequence a plurality of individual thin layers of CrN intermediate layers and the first Mo.sub.aN.sub.x support layers 4.

[0116] In the embodiment according to FIG. 4b, in comparison to FIG. 4a, a further second multilayer coating 71 is additionally provided on the adhesive layer 6 of Cr deposited on the substrate 1, which comprises in alternating sequence a plurality of individual thin layer of a first CrN1 having a first composition of Cr and nitrogen and further comprises a plurality of individual thin layer layers of a second CrN2 having a second composition of Cr and nitrogen different from the first composition according to CrN1.

[0117] It is understood that the multilayer coating 71 according to the present invention can also comprise more than two different types of partial layers, or a coating system 2 according to the invention can also comprise more than two identical or different multilayer coatings 71, which can be provided at different positions in the coating system 2.

[0118] In addition, it is also possible that a multilayer coating 71 is partially or completely designed as a gradient layer in which the chemical composition changes more or less continuously in a characteristic manner with respect to a coating direction.

[0119] Finally, on the basis of FIGS. 5a and 5b, two further embodiments of coating systems 2 according to the invention are discussed schematically, which are provided with at least a first and a second support layer under the cover layer 3. Here, the nitrogen content x of the first Mo.sub.aN.sub.x support layer 4 is in the range of 30 at %≤x≤53 at % and is particularly advantageous at about 50 at %. If in a very specific embodiment, in which the first Mo.sub.aN.sub.x support layer 4 is e.g., a gradient layer, the hardness of the first Mo.sub.aN.sub.x support layer 4 may preferably increase by an increasing nitrogen content in the direction towards the cover layer 3. In addition, in the coating system 2 of FIG. 5a and FIG. 5b, at least a second Mo.sub.bN.sub.y support layer 5 is provided between the first Mo.sub.aN.sub.x support layer 4 and the substrate 1, wherein, referred to a Mo content b of the second Mo.sub.bN.sub.y support layer, a nitrogen content y is in the range of 35 at %≤y≤45 at %, with y+b=100 at %, and preferably at 40 at %. This means that the hardness H of the second Mo.sub.bN.sub.y support layer 5 is in particular smaller than that of the first Mo.sub.aN.sub.x support layer 4, so that the hardness H of the coating system preferably increases in the direction towards the cover layer 3. The same applies here in an analogous manner: if, in a very specific embodiment, the second Mo.sub.bN.sub.y support layer 5 is, for example, a gradient layer, the hardness H of the second Mo.sub.bN.sub.y support layer 5 can preferably increase in the direction towards the cover layer 3 due to an increasing nitrogen content, i.e., decrease in the direction towards the substrate 1.

[0120] In the specific embodiment example of FIG. 5b, an adhesive layer 6 of Cr is additionally provided to improve the adhesion between the substrate 1 and the second Mo.sub.bN.sub.y support layer 5. And in addition, a further adhesive layer 6 of Mo+Mo.sub.2N is provided in each case between the first Mo.sub.aN.sub.x support layer 4 and the second Mo.sub.bN.sub.y support layer 5, and between the first Mo.sub.aN.sub.x support layer 4 and the cover layer 3, wherein they are preferably designed as Mo layer with a Mo.sub.2N minor phase in each case.

[0121] Finally, on the basis of FIG. 6, a preferred course of the hardness H and the Young's modulus E for a special coating system of the invention with a coating system according to the invention deposited on a substrate 1 of steel will be discussed by way of example. The special coating system 2 of FIG. 6 comprises an adhesive layer 6 arranged on the substrate 1, a subsequent intermediate layer 7 and a MoN support layer system 4, 5 arranged on a further adhesive layer 6, which lies immediately below the cover layer 3. The hardness in GPa is plotted on the left at the ordinate of the diagram in FIG. 6, the Young's modulus in GPa on the right and the thickness D of the coating system in nm on the abscissa.

[0122] It can be clearly recognized that here the hardness of the substrate 1 of the coating system 2 with the substrate 1 becomes increasingly larger in the direction towards the cover layer 3. The same applies to the Young's modulus, which also becomes increasingly larger away from the substrate 1 in the direction towards the cover layer 3. In particular, it can be clearly recognized that the intermediate layer 7 has a smaller hardness H and a smaller Young's modulus E than the MoN support system 4, 5 comprising the first Mo.sub.aN.sub.x support layer 4 and/or the second Mo.sub.bN.sub.y support layer 5, and also the hardness of the MoN support system 4, 5 comprising the first Mo.sub.aN.sub.x support layer 4 and/or the second Mo.sub.bN.sub.y support layer increases towards the cover layer.

[0123] It is understood that for all the embodiments previously described in the general description and in the figures, further embodiments are also conceivable in practice, which may comprise further additional layer types according to the invention between the cover layer 3 and the substrate 1. Thus, depending on the application and requirements of the coated substrate 1, additional layers, such as one or more additional first Mo.sub.aN.sub.x support layers 4, additional second Mo.sub.bN.sub.ysupport layers 5, additional intermediate layers 7, or even additional adhesive layers 6 can be provided at a suitable location in the coating system 2, which, for reasons of clarity, are not necessarily represented explicitly in the figures of the present application.

[0124] Which exact layer composition and architecture of the coating system 2 is to be selected in the specific application is left to the person skilled in the art who knows how to select the most suitable coating system 2 based on his experience or by using relevant criteria and tests known per se.