Molybdenum nitride based multilayer coatings for wear and friction reduction

Abstract

A method for producing a Mo-N based coating structure, comprising providing a substrate (1) to be coated and applying a hard material layer (6) onto the substrate (1), the hard material layer (6) comprising at least one layer (4) of Mo-N having a hexagonal crystal structure and at least one layer (5) of Mo-N having a cubic crystal structure or a mixed hexagonal / cubic crystal structure, the hard material layer (6) being applied by a low-temperature closed-field unbalanced reactive magnetron sputtering coating process.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a molybdenum nitride-based multi-layer coating, and to a device comprising a molybdenum nitride-based multi-layer coating, preferably produced by such a method. [Background technology]

[0002] Molybdenum nitride (Mo-N) coatings are of interest in anti-friction applications due to their wear-resistant and friction-reducing properties, particularly in automotive applications. Molybdenum nitride (δ-MoN), which has a hexagonal crystal structure, is particularly attractive due to its excellent properties in terms of wear and friction reduction, as well as oxidation resistance.

[0003] Current Technology Although molybdenum nitride with a cubic crystal structure is considered inferior, as reported by Zhu et al. in Surface and Coating Technology 223 (2013) 184-189, the majority of previous research and inventions have focused on molybdenum nitride with a cubic crystal structure. However, hexagonal molybdenum nitride-based coatings produced by cathodic arc evaporation, also known as arc PVD, have been described in detail elsewhere ( WO 2016188632 A1 , EP 3074550 B1 ). The most important teaching in these publications is that the use of arc PVD allows for high ionization and high average (kinetic) energy of metal ions from the target, which are necessary for the deposition of molybdenum nitride with a hexagonal crystal structure. This technique allows for the realization of cubic Mo-N at relatively low process temperatures, which are intended to accommodate substrates typically applied in the automotive and automotive parts fields. However, a well-known drawback of arc PVD is the inevitable formation of macroparticles, or "droplets," in the coating. Post-treatment of the coating to remove macroparticles is essential in this case to keep counterbody wear low.

[0004] On the other hand, reactive magnetron sputtering is a coating process with attractive deposition rates without the formation of undesirable macroparticles. Unfortunately, ionization is low, and the energy of the particles deposited on the substrate is relatively low. This typically results in a decrease in coating hardness, making the coating less attractive for the intended application. The implementation of closed-field unbalanced magnetron sputtering offers the possibility of transferring a large ion current to the substrate. One of the main features of unbalanced magnetron sputtering is the generation of a stronger magnetic field in one of the poles, thereby extending the magnetic field lines further away from the target. This allows the generation of additional ions, which facilitates the formation of hexagonal molybdenum nitride coatings on the substrate. In addition, the formation of a sufficiently dense coating structure at a relatively low homogeneous temperature can also be achieved in this way.

[0005] To date, there have been only a few publications on molybdenum nitride coatings with a hexagonal structure or at least a hexagonal phase in the mixed crystal structure of Mo—N, produced at temperatures below 220° C., and thus by reactive magnetron sputtering (Hones et al. Journal of Physics D: Applied Physics, 36(8) (2003) 1023-1029; Pappacena et al. Wear 62-70 (2013) 278-279). However, they are often limited by teaching only one type of Mo—N, and / or the Mo—N coating is combined with other types of coatings, such as WN or Cr—N.

[0006] A typical phenomenon during reactive magnetron sputtering, regardless of its type, is the so-called target poisoning, as described by Kubart et al. Thin Solid Films 515 (2006) 421-424. Its effect, among other things, depends on the amount of reactive gas introduced into the coating chamber. The evolution of the target voltage during the poisoning process provides valuable hints regarding suitable operating parameters for the production of the desired transition metal nitrides. The present invention utilizes the target poisoning phenomenon to identify suitable operating parameters that allow the deposition of molybdenum nitrides with a hexagonal (δ-MoN) and / or cubic (γ-MoN) structure.

[0007] Furthermore, one of the common methods in modern materials design today is the creation of nanocomposite coatings, for example, containing small nanoparticles of one phase embedded in a nanostructured phase of a different composition or crystal structure. Such designs can significantly improve the properties of the deposited coatings, such as their protective effect. The benefits of such designs have proven effective for cubic (γ-MoN) molybdenum nitride combined with chromium nitride via an arc PVD process, as demonstrated by Pogrebnjak et al. Materials & Design 153 (2018) 47-59. However, the present invention combines materials with different crystal structures not simply by embedding them into a nanocomposite, but by creating a multilayer structure using a low-temperature, closed-field, unbalanced reactive magnetron sputtering coating process, where the thickness of the individual layers is controlled and the layers are combined through different deposition parameters. This has proven to be an effective tool for achieving a synergistic protective effect in the resulting coating. Summary of the Invention [Problem to be solved by the invention]

[0008] Object of the invention It is an object of the present invention to alleviate or overcome one or more of the difficulties associated with the prior art. In particular, it is an object of the present invention to provide coating structures and methods for producing coating structures that exhibit improved reduced wear and friction characteristics. [Means for solving the problem]

[0009] Detailed Description of the Invention To overcome these problems, a method for producing a Mo-N based coating structure and a coating structure, preferably a coating structure produced by such a method, have been invented.

[0010] Thus, in a first aspect of the present invention, a method for producing a Mo—N based coating structure is disclosed, comprising providing a substrate to be coated and applying a hard material layer on the substrate, the hard material layer comprising at least one layer of Mo—N having a hexagonal crystal structure and at least one layer of Mo—N having a cubic crystal structure or a mixed hexagonal / cubic crystal structure, wherein the hard material layer is applied by a low temperature closed field unbalanced reactive magnetron sputtering coating process.

[0011] In the context of the present invention, a layer having a hexagonal crystal structure particularly refers to a layer having a hexagonal crystal structure proportion of more than 90%, preferably more than 95%, and most preferably 98%. Accordingly, in the context of the present invention, a layer having a cubic crystal structure particularly refers to a layer having a cubic crystal structure proportion of more than 90%, preferably more than 95%, and most preferably 98%. In the context of the present invention, a layer having a mixed cubic and hexagonal crystal structure particularly refers to a layer having a cubic crystal structure proportion of at least 30%, preferably at least 50%. In the context of the present invention, a low-temperature closed-field unbalanced reactive magnetron sputtering coating process particularly refers to a process at a temperature below 250°C, preferably below 200°C.

[0012] In another example of the first aspect, at least one layer of Mo—N having a hexagonal crystal structure may be applied before applying at least one layer of Mo—N having a cubic crystal structure or at least one layer of Mo—N having a mixed hexagonal / cubic crystal structure onto the layer of Mo—N having a hexagonal crystal structure.

[0013] For better adhesion of the hard layer to the substrate, an adhesive layer may be applied on the substrate, preferably between the substrate and the hard material layer, and in particular directly on the substrate.

[0014] Similarly, for better adhesion of the hard layer to the substrate, a support layer may be applied on the substrate, preferably between the substrate and the hard material layer, and in particular directly on the adhesive layer.

[0015] For easy determination of suitable coating parameters, target poisoning may be performed to obtain suitable operating parameters.

[0016] With regard to suitable coating temperatures, process temperatures below 250° C., preferably below 220° C., especially below 180° C. may be used during production. Such temperatures have the advantage that they also allow for the effective coating of temperature-sensitive substrates.

[0017] In another example of the first aspect, the hard material layer may be applied as a bilayer including one layer of Mo—N having a hexagonal crystal structure and one layer of Mo—N having a cubic crystal structure or a mixed hexagonal / cubic crystal structure.

[0018] In another example of the first aspect, at least two sputter cathodes may be used, and preferably at least four cathodes may be used to apply the coating structure.

[0019] To allow complete coating of differently shaped substrates in a simple and flexible manner, the substrates may be mounted on a three-time rotation tooling system during the coating process.

[0020] For the production of a pure and clean coated product, the substrate may be heated to a temperature of 100-150°C, preferably 110-140°C, especially 130°C, prior to the coating process.

[0021] Similarly, for the production of a pure and clean coated product, the substrate may be cleaned prior to the coating process, which cleaning may preferably involve etching, particularly etching with argon plasma.

[0022] In another example of the first aspect, the coating may be carried out in a protective gas atmosphere, preferably argon may be used as the protective gas, and argon may be present at a concentration of about 1 to 3 10 -3 Pressures of mbar may be used.

[0023] In another example of the first aspect, a bias voltage of −120V (mf) to −180V (mf), preferably −150V (mf), may be used.

[0024] In another example of the first aspect, at least one layer of Mo—N having a hexagonal crystal structure and at least one layer of Mo—N having a cubic crystal structure or a mixed hexagonal / cubic crystal structure may be applied under different coating conditions, in particular different nitrogen pressures.

[0025] For the targeted setting of suitable coating parameters, at least one layer of Mo-N with a hexagonal crystal structure has a thickness of 2.3 to 5.0 10 -3 A nitrogen pressure of 0.5 to 0.9 mbar may be applied, and layers of Mo-N with cubic or mixed hexagonal / cubic structure are formed at a pressure of 0.5 to 0.9 10 mbar. -3It may be applied at a nitrogen pressure of 1000 mbar. Such coating parameters have proven advantageous for the purpose of producing coatings with improved, reduced wear and friction properties.

[0026] In a second aspect of the present invention, a Mo-N-based coating structure is disclosed, preferably producible by the aforementioned method, comprising a substrate and a hard material layer applied onto the substrate, the hard material layer comprising at least one layer of Mo-N having a hexagonal crystal structure and at least one layer of Mo-N having a cubic crystal structure or a mixed hexagonal / cubic crystal structure. In another example of the second aspect, the hard material layer can be formed as a bilayer comprising one layer of Mo-N having a hexagonal crystal structure and one layer of Mo-N having a cubic crystal structure or a mixed hexagonal / cubic crystal structure, and the thickness of the bilayer may be preferably less than 400 nm, more preferably less than 300 nm, and especially less than 180 nm.

[0027] In another example of the second aspect, the hard material layer may be formed as a multilayer comprising more than two layers, and the hard material layer may preferably comprise an alternating structure comprising one layer of Mo—N having a hexagonal crystal structure and one layer of Mo—N having a cubic crystal structure or a mixed hexagonal / cubic crystal structure.

[0028] According to a preferred embodiment of the present invention, the hard material layer may be formed as a multilayer as described above and have a bilayer period of at most 200 nm, preferably less than 200 nm, which means that the sum of the thickness of the Mo—N layer with hexagonal crystal structure and the thickness of the Mo—N layer with cubic crystal structure or mixed hexagonal / cubic crystal structure may be less than 200 nm, preferably less than 150 nm.

[0029] For better adhesion of the hard layer to the substrate, the Mo—N based coating structure may include an adhesion layer, which may preferably be located between the substrate and the hard material layer, in particular directly on the substrate.

[0030] Similarly, in view of better adhesion of the hard layer to the substrate, the Mo—N-based coating structure may include a support layer, which may preferably be located between the substrate and the hard material layer, in particular directly on the adhesive layer.

[0031] With regard to suitable substrates, the substrate may be made from hardened steel, preferably 17Cr3 / 1.7016 steel.

[0032] Regarding advantageous material selection for the adhesion layer and / or support layer, the adhesion layer and / or support layer may comprise a metal, preferably Mo or Cr, and in particular the adhesion layer and / or support layer may be made of CrN or MoN or TiN or other metal nitrides that may be suitable as support layers.

[0033] In another example of the second aspect, the hard material layer may exhibit an indentation hardness of >32.00+ / -2.00 GPa, preferably >34.00+ / -2.00 GPa, measured according to DIN EN ISO 14577-4.

[0034] In another example of the second aspect, the hard material layer is 6.00 m 3 m -1 N -1 10 -15 Less than 4.00m, preferably 3 m -1 N -1 10 -15 It may exhibit an abrasive wear (measured by a calowear abrasion tester) of less than 100%.

[0035] The antifriction behavior under high loads (200 N and 400 N, respectively) and temperatures (T = 150 °C) was evaluated in reciprocating wear tests in a ball-on-component configuration (0W20 oil (Fuchs 0W20 EVO), 20 Hz frequency, 4.6 mm stroke length, 10 mm diameter 100Cr6 ball counterbody).

[0036] The present invention will be described in more detail below based on examples and with reference to the drawings. Detailed Description of the Invention [Brief explanation of the drawings]

[0037] [Figure 1] 1 shows a Mo—N based coating structure according to the present invention, showing a dual layer structure. [Figure 2] 1 shows a Mo—N based coating structure according to the present invention, showing a multi-layer structure. [Figure 3] 1 shows the surface of a Mo—N based coating structure according to the invention on a wear scar on a sample after 3 hours (200 N test). [Figure 4] 1 shows the surface of a Mo—N based coating structure according to the invention on a wear scar on a sample after 3 hours (400 N test). [Figure 5] 1 shows the surface of a Mo—N based coating structure according to the invention on a wear scar on a sample after 3 hours (400 N test). DETAILED DESCRIPTION OF THE INVENTION

[0038] The hexagonal molybdenum nitride-based single-layer and multilayer coating systems are implemented using a PVD coating machine containing at least two sputter cathodes, preferably four, two of which are equipped with metallic Mo targets. The multilayer coating system is shown schematically in Figure 1.

[0039] In some invention examples: The coating is deposited on a cylindrical steel substrate 1 made of surface-hardened steel of the 17Cr3 / 1.7016 type, which is mounted on a three-times rotating tooling system. The hardened steel 17Cr3 / 1.7016 should not be understood as limiting the substrates that can be used in accordance with the present invention, but should be understood only as an example. Also, other substrate materials, such as other hardened steel materials similar to 17Cr3 / 1.7016, can be considered suitable substrate temperature-sensitive materials in the context of the present invention. However, the substrate materials that can be used in the context of the present invention are not limited to hardened steel materials.

[0040] Prior to coating, the substrate is heated to a temperature of 100°C to 150°C, preferably 110°C to 140°C, in particular 130°C, and etched using a pure Ar plasma, Ar ions being extracted from the plasma beam supported by an electron emitter.

[0041] The deposition of hexagonal molybdenum nitride based coating systems, e.g., adhesion layers and single-phase molybdenum nitride layers or single-phase molybdenum nitride layers only, is carried out by closed-field unbalanced magnetron sputtering from two metallic Mo targets.

[0042] The coating system of the present invention, in some embodiments, comprises: Adhesion layer 2: To ensure adhesion of the following multilayer system onto substrate 1, such as a steel substrate (although the adhesion layer is optional), adhesion layer 2 is formed by heating at 2.0 10 -3 The deposition is carried out at a constant target power in the pressure range of 1000 mbar. The bias voltage is set to -150 V (mf). The material of the adhesion layer 2 can be a metal, such as molybdenum (Mo) or chromium (Cr), but is most preferably Cr or a nitride, such as CrN or MoN.

[0043] Optionally, a support layer 3, for example CrN or MoN, or TiN, or other suitable transition metal nitride, can be made on the adhesion layer 2.

[0044] -Hexagonal molybdenum nitride layer 4: The process window is approximately 10 kW target power and 2.0·10 -3 It is specified in mbar argon base pressure. -3 ~5.0 10 -3 Preferred nitrogen partial pressure of 1.5 mbar, more preferably 2.8 10 -3 ~4.5·10 -3 A nitrogen partial pressure of 4.0 mbar also allows the formation of hexagonal molybdenum nitride in the low energy region of magnetron sputtering. Most preferably, the present invention provides a nitrogen partial pressure of 4.0 mbar. -3 A nitrogen partial pressure of 1000 mbar allows the formation of molybdenum nitride with a hexagonal crystal structure.

[0045] Cubic molybdenum nitride layer 5: Under the same basic conditions as the Mo-N layer 4, the nitrogen partial pressure was increased to 0.5 10 -3 mbar~0.9 10 -3 mbar, preferably 0.6 10 -3 mbar~0.8 10 -3 By using a pressure of 0.7-10 mbar, it is possible to form single-phase molybdenum nitride with a cubic crystal structure. -3 A nitrogen partial pressure of 1000 mbar allows the formation of molybdenum nitride with a cubic crystal structure.

[0046] According to another preferred embodiment of the present invention, the deposition of a hexagonal molybdenum nitride-based multilayer coating system is carried out by closed-field unbalanced magnetron sputtering from at least two metallic Mo targets. The coating system is shown in Figure 2. The coating system is deposited on a cylindrical steel substrate 1 made of surface-hardened 17Cr3 steel, which is mounted on a three-turn tooling system.

[0047] Prior to coating, the substrate 1 is heated to a temperature of 100°C to 150°C, preferably 110°C to 140°C, in particular 130°C, and etched using a pure Ar plasma, where Ar ions are extracted from a plasma beam supported by an electron emitter.

[0048] For example, deposition of a molybdenum nitride multilayer coating system, such as an alternating coating of adhesion layers 2 and hexagonal single-phase / cubic mixed 5 or single-phase molybdenum nitride layers 4, is performed by closed-field unbalanced magnetron sputtering from two metallic Mo targets.

[0049] The coating system according to the present invention comprises: Adhesive layer 2: To ensure adhesion of the following multilayer system to substrate 1, such as a steel substrate, adhesive layer 2 is heated at 2.0 10 -3Deposition is performed at a constant target power in the mbar pressure range. The bias voltage is set to -150 V (mf). The adhesion layer material can be a metal, such as molybdenum (Mo) or chromium (Cr), but is most preferably Cr or a nitride, such as CrN, MoN, or TiN, or other suitable adhesion layer material.

[0050] Optionally, a support layer 3, for example CrN or MoN or TiN or other suitable transition layer material, can be made on top of the adhesion layer 2.

[0051] Molybdenum nitride multilayers 8: Molybdenum nitride layers are deposited alternately, including at least single-phase hexagonal layers 4 and single-phase cubic molybdenum nitride layers 5 and / or mixed-phase hexagonal / cubic molybdenum nitride layers 5. The layers 4, 5 are combined into a multilayer system 8. The multilayer coating system 8 includes a variable number of at least one or more bilayers 6', each bilayer 6' including at least one Mo-N layer 4 having a hexagonal crystal structure and at least one MoN layer 5 having a cubic single-phase or cubic / hexagonal mixed-phase crystal structure, i.e., hexagonal Mo-N + cubic Mo-N or hexagonal Mo-N + mixed hexagonal / cubic Mo-N. All bilayers 6' are deposited with a constant target power of 10 kW and a bias voltage applied to the substrate by a pulsed power supply set at approximately -150 V (mf). The deposition time of the bilayers is adjusted so that the thickness of the at least one bilayer 6' is preferably <400 nm, preferably <200 nm. Most preferably, the present invention allows the deposition of multilayer coating systems with improved protective properties when the total thickness of the at least one bilayer is less than 180 nm.

[0052] The total coating thickness of the hexagonal MoN-based multilayer coating system 8 can be adjusted by adjusting the number of bilayers 6' deposited.

[0053] Single-layer, single-phase hexagonal and cubic MoN coatings exhibit high indentation hardnesses of 29.00±2.00 GPa and 31.00±2.00 GPa, respectively. The MoN-based multilayer system reported here,8 with alternating hexagonal and cubic / mixed structures, has an indentation hardness of 35.00±2.00 GPa.

[0054] Single-layer, single-phase hexagonal and cubic MoN coatings are 7.00±1.00m 3 m -1 N -1 10 -15 and 10.00±1.00m 3 m -1 N -1 10 -15 Surprisingly, the MoN-based multilayer system 8 reported here, with alternating hexagonal and cubic / mixed crystal structures, exhibits a typical calo-wear of 4.00 m 3 m -1 N -1 10 -15 Has less than 100% Caro wear.

[0055] Coated components without additional surface modification, such as a 26 mm diameter piston pin, were tested under high loads (200 N and 400 N, respectively) and temperatures (T = 150 °C) using 0W20 oil (Fuchs 0W20 EVO) in a reciprocating wear test in a ball-on-component configuration (20 Hz frequency, 4.6 mm stroke length, 10 mm diameter 100Cr6 ball). Post-test wear scar, volume loss, and component surface film analysis were used to determine the benefits of the coating system reported herein. The single-layer, single-phase hexagonal molybdenum nitride-coated component showed minor coating delamination in the wear scar already after a 200 N test. This can be attributed to the relatively high compressive stress typically associated with the coating. Figure 3 shows the coating delamination in the wear scar on a sample after 3 hours.

[0056] The extent of these small localized delaminations increases after the 400 N test. The calculated counterbody wear volume is 5.30 10 -3 mm 3 This is shown in Figure 4, which shows the wear scar on the sample after a 3 hour but 400 N test.

[0057] On the other hand, the Mo-N based multilayer system according to the invention, for example with a bilayer thickness of 130 nm, does not show delamination in any of the load classes tested. Antifriction pair: Coated component versus 100Cr6 ball, applying a load of 400 N and 0W20 commercial engine oil (Fuchs 0W20 EVO), results in a stable coefficient of friction well below 0.05 [-]. The calculated counterbody wear volume is 2.00 10 -3 mm 3 This is illustrated by Figure 5, which shows no delamination on the wear track of the sample after 3 hours under a 400 N load.

Claims

1. A method for manufacturing a Mo—N-based coating structure, comprising: - providing a substrate (1) to be coated; - applying a hard material layer (6) onto said substrate (1), said hard material layer (6) comprising at least one layer (4) of Mo—N with a hexagonal crystal structure and at least one layer (5) of Mo—N with a cubic crystal structure or a mixed hexagonal / cubic crystal structure, - said hard material layer (6) is applied by a low temperature closed field unbalanced reactive magnetron sputtering coating process; The method for producing a Mo—N-based coating structure, wherein applying the hard material layer (6) onto the substrate (1) comprises first applying at least one layer (4) of Mo—N having a hexagonal crystal structure, and then applying at least one layer (5) of Mo—N having a cubic crystal structure or a mixed hexagonal / cubic crystal structure onto the layer (4) of Mo—N having a hexagonal crystal structure.

2. 2. The method according to claim 1, wherein an adhesive layer (2) is applied onto the substrate (1), the adhesive layer (2) being preferably applied between the substrate (1) and the hard material layer (6), the adhesive layer (2) being in particular applied directly onto the substrate (1).

3. 3. The method according to claim 1 or 2, wherein a support layer (3) is applied onto the substrate (1), preferably between the substrate (1) and the hard material layer (6), and wherein the support layer (3) is applied in particular directly onto the adhesive layer (2).

4. The method according to any one of claims 1 to 3, wherein target poisoning is performed to obtain suitable operating parameters.

5. The method according to any one of claims 1 to 4, wherein a process temperature below 250°C, preferably below 220°C, in particular below 180°C is used during the coating process.

6. 6. The method according to any one of claims 1 to 5, wherein the hard material layer (6) is applied as a double layer (6') comprising one layer (4) of Mo-N with a hexagonal crystal structure and one layer (5) of Mo-N with a cubic or mixed hexagonal / cubic crystal structure.

7. The method according to any one of claims 1 to 6, wherein at least two sputter cathodes are used, preferably at least four cathodes, for applying the coating structure.

8. The method according to any one of claims 1 to 7, wherein the substrate (1) is mounted on a triple rotary tooling system during the coating process.

9. The method according to any one of the preceding claims, wherein the substrate (1) is heated to a temperature of 100-150°C, preferably 110-140°C, in particular 130°C, before the coating process.

10. The method according to any one of claims 1 to 9, wherein the substrate (1) is cleaned before the coating process, said cleaning preferably comprising etching, in particular etching with argon plasma.

11. The coating is carried out in a protective gas atmosphere, preferably argon is used as the protective gas, and argon is about 1 to 3.10 －３ 11. The method according to claim 1, wherein a pressure of 0.5 to 1.0 mbar is used.

12. 12. The method according to any one of claims 1 to 11, wherein a bias voltage of -120V (mf) to -180V (mf), preferably a bias voltage of -150V (mf) is used.

13. 13. The method according to any one of claims 1 to 12, wherein the at least one layer (4) of Mo—N with hexagonal crystal structure and the at least one layer (5) of Mo—N with cubic crystal structure or mixed hexagonal / cubic crystal structure are applied under different coating conditions, in particular different nitrogen pressures.

14. The at least one layer (4) of Mo—N having a hexagonal crystal structure has a molecular weight of 2.3 to 5.0·10 －３ The layer (5) of Mo—N with a cubic or mixed hexagonal / cubic structure is applied at a nitrogen pressure of 0.5 to 0.9 mbar. －３ 14. The method according to any one of claims 1 to 13, applied at a nitrogen pressure of 10 ...

15. A Mo-N based coating structure, a substrate (1), a Mo—N-based coating structure, comprising a hard material layer (6) applied onto said substrate (1), said hard material layer (6) comprising a stack structure in which at least one layer (4) of Mo—N with a hexagonal crystal structure and at least one layer (5) of Mo—N with a cubic crystal structure or a mixed hexagonal / cubic crystal structure are deposited in this order on said substrate (1).

16. 16. A Mo-N based coating structure according to claim 15, wherein the hard material layer (6) is formed as a double layer (6') consisting of one layer (4) of Mo-N with a hexagonal crystal structure and one layer (5) of Mo-N with a cubic crystal structure or a mixed hexagonal / cubic crystal structure, the thickness of the double layer (6') being preferably less than 400 nm, more preferably less than 300 nm, in particular less than 180 nm.

17. 17. The Mo-N based coating structure according to claim 15 or 16, wherein the hard material layer (6) is formed as a multilayer (8) comprising more than two layers, the hard material layer (6) preferably comprising an alternating structure, the alternating structure comprising one layer (4) of Mo-N with a hexagonal crystal structure and one layer (5) of Mo-N with a cubic crystal structure or a mixed hexagonal / cubic crystal structure.

18. The Mo-N based coating structure according to any one of claims 15 to 17, wherein the Mo-N based coating structure comprises an adhesion layer (2), which is preferably arranged between the substrate (1) and the hard material layer (6), in particular directly on the substrate (1).

19. The Mo-N based coating structure according to any one of claims 15 to 18, wherein the Mo-N based coating structure comprises a support layer (3), which is preferably arranged between the substrate (1) and the hard material layer (6), in particular directly on the adhesion layer (2).

20. 18. The Mo—N based coating structure according to claim 17, wherein the sum of the thickness of the layer (4) of Mo—N with hexagonal crystal structure and the thickness of the layer (5) of Mo—N with cubic crystal structure or mixed hexagonal / cubic crystal structure is less than 200 nm, preferably less than 150 nm.

21. Mo—N based coating structure according to any one of claims 15 to 20, wherein said substrate (1) is made from hardened steel, preferably 17Cr3 / 1.7016 steel.

22. A Mo-N based coating structure described in any one of claims 15 to 21, wherein the adhesive layer (2) and / or the support layer (3) contains a metal, preferably Mo or Cr, and in particular consists of CrN or MoN.

23. 23. A Mo-N based coating structure according to any one of claims 15 to 22, wherein said hard material layer (6) exhibits an indentation hardness of >32.00 + / - 2.00 GPa, preferably >34.00 + / - 2.00 GPa, measured according to DIN EN ISO 14577-4.

24. The hard material layer (6) is 6.00 m ３ m －１ N －１ ・10 －１５ Less than 4.00 m, preferably ３ m －１ N －１ ・10 －１５ The Mo-N based coating structure according to any one of claims 15 to 23, exhibiting a Caro abrasion of less than 1000 kJ / cm.

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