Method for manufacturing a coated panel unit and coated panel unit

Abstract

This invention relates to a method for manufacturing sheet metal units, and preferably for further processing of sheet metal units, comprising a coating step (II) in which a first initial coating (7), preferably a single layer, is applied to a first surface (5) of a metal plate (3) to form a sheet metal unit (1) having the metal plate (3) and at least the first initial coating (7), and a heating step (III) in which the sheet metal unit (1) is heated to a heating temperature or above the heating temperature. According to the invention, the alloy of the preferred metal first initial coating (7) comprises titanium as a first alloying element, aluminum as a second alloying element, manganese as a third alloying element, and zinc as a fourth alloying element.

Description

[0001] The present invention relates to a method for manufacturing a sheet metal unit according to the preamble of claim 1 and a sheet metal unit according to claim 11.

[0002] The sheet metal unit of the type described in this invention comprises a metal sheet and an aluminum-silicon coating (AlSi coating). This AlSi coating is applied to at least one surface of the metal sheet. The AlSi coating provides corrosion protection to the metal sheet by facilitating the formation of a passivation layer on the metal sheet surface. However, the corrosion protection of the passivation layer is limited, meaning that the passivation layer only provides sufficient corrosion protection to the metal sheet in dry areas, such as vehicle bodies. Therefore, a particular disadvantage of this sheet metal unit is that, without additional measures, it cannot be applied to wet areas, such as vehicle bodies.

[0003] DE 10 2016 102 504 A1 discloses an aluminum-based coating for steel plates or strips and a method for manufacturing them. DE 10 2020 201 451 A1 discloses a hot-formed steel plate, a method for manufacturing a hot-formed steel plate component, and a hot-formed steel plate component. EP 2 848 709 B1 discloses a method for manufacturing a steel component with a metallic anti-corrosion coating and a steel component.

[0004] The technical problem to be solved by this invention is to provide a sheet metal unit that can cover a wider range of applications compared with known sheet metal units.

[0005] The aforementioned technical problem is solved by the features of the independent claim. Preferred improvements of the invention are disclosed in the dependent claims.

[0006] According to the present invention, a method for manufacturing sheet metal units, and preferably for further processing of sheet metal units, is provided. The method includes a coating step in which a first initial coating, preferably a single layer, is applied to a first surface of a metal sheet to form a sheet metal unit having the metal sheet and at least the first initial coating. The method further includes a heating step in which the sheet metal unit is heated to a heating temperature or above the heating temperature. According to the present invention, the alloy of the preferred metal first initial coating comprises titanium as a first alloying element, aluminum as a second alloying element, manganese as a third alloying element, and zinc as a fourth alloying element. Combined with these four alloying elements, preferably only with these four alloying elements, the coating can meet the different requirements of the sheet metal unit in further processing and application. The alloying element titanium prevents alloying of the coating with iron during the heating step. The alloying element aluminum avoids the formation of oxide scale on the surface during the heating step. The alloying element manganese improves the heat resistance of the coating during the heating step. The alloying elements zinc and manganese achieve the desired corrosion resistance and weldability.

[0007] In one specific embodiment, the heating temperature may be specified to be in the range of 300°C to 1100°C, preferably in the range of 450°C to 1000°C, particularly preferably in the range of 550°C to 1000°C, and most preferably in the range of 700°C to 950°C, and / or the heating temperature corresponds to the austenitizing temperature AC1 of the alloy of the metal sheet, and / or the heating temperature corresponds to the austenitizing temperature AC3 of the alloy of the metal sheet. Starting at a temperature of 300°C, the diffusion process begins; from 450°C, the diffusion process leading to segregation accelerates. Up to 700°C, the sheet elements can be pre-diffused in a heating device, for example, as a coil, without altering the sheet properties. Between 550°C and 700°C, the diffusion process accelerates, making it possible, for example, to provide slabs and / or cold-formed parts using this method. Between 700°C and 1100°C, the sheet elements can be further processed, for example, in a hot-forming step. The minimum temperature required for this is the austenitizing temperature. The austenitizing temperature AC1 starts at approximately 700°C, and full austenitization of the structure is preferably completed at 950°C. For applications of rapid heating methods, it is advantageous to apply higher temperatures, up to 1100°C, to the sheet metal units for a short period of time. In principle, the sheet metal units can exhibit, for example, sloping or stepped temperature profiles within these temperature ranges.

[0008] In one exemplary embodiment, the first initial coating may be specified to be a single layer and / or have only one layer after the coating step is completed and / or before the heating step begins and / or before the heating temperature is reached, wherein, preferably, all alloying elements are uniformly distributed and / or uniformly mixed with each other in this single layer. This simplifies the coating process and allows it to be carried out in a shorter process time, for example, in a single pass-through process of cold-rolled strip manufacturing.

[0009] In one exemplary embodiment, it may be specified that during the heating step, preferably upon reaching the heating temperature, the preferred single-layer first initial coating transforms into a preferred three-layer first coating system, and / or the alloying elements in the sole layer of the first initial coating segregate upon forming the first coating system. Preferably, the first coating system, after alloying element segregation, primarily, preferably exactly, has three layers: a first connecting layer, a preferred hierarchical first intermediate layer, and a first surface layer. Only through the formation and arrangement of these layers can the various requirements of the sheet metal unit in further processing be met. The corresponding layers can satisfy specific requirements in further processing, such as the surface layer providing anti-scaling protection, the connecting layer forming a diffusion barrier, and the intermediate layer ensuring corrosion protection.

[0010] In one specific embodiment, it may be specified that the sole layer of the first initial coating, during the heating step, preferably upon reaching the heating temperature, transforms into such a state that the first coating system and / or alloying elements segregate such that the first connecting layer is arranged between the metal plate and the first intermediate layer, and / or the first intermediate layer is arranged between the first connecting layer and the first surface layer, and / or the surface of the first surface layer facing away from the intermediate layer is free from further coating and / or covered by a paint layer. The arrangement of the first connecting layer ensures, for example, that iron is prevented from diffusing from the metal plate into the coating, and avoids the undesirable zinc-iron alloying according to the invention. The arrangement of the first intermediate layer, for example, ensures that the alloying elements zinc and manganese can interact electrochemically with each other. The arrangement of the first surface layer prevents the formation of an oxide scale on this layer during the heating step.

[0011] In one exemplary embodiment, the first connecting layer may be specified to primarily, preferably only, contain a first alloying element, namely titanium, and / or the first intermediate layer may primarily, preferably only, contain a third alloying element, namely manganese, and a fourth alloying element, namely zinc, and / or the first surface layer may contain a second alloying element, preferably substantially aluminum, and / or a fourth alloying element, namely zinc. This allows the requirements of the sheet metal unit for further processing and application to be met with a particularly short process time.

[0012] In one specific embodiment, it may be specified that a first alloying element, namely titanium, in the first connecting layer, preferably in the core of the first connecting layer, has a weight percentage at least 50%, preferably 100%, higher than that in the first initial coating, and / or a third alloying element, namely manganese, and a fourth alloying element, namely zinc, in the first intermediate layer, preferably in the core of the first intermediate layer, together having a weight percentage at least 60%, preferably 70%, higher than that in the initial coating, and / or a second alloying element, namely aluminum, in the first surface layer, preferably in the core of the first surface layer, and / or a fourth alloying element, namely zinc, having a weight percentage at least 50%, preferably 100%, higher than that in the initial coating. Under these conditions, the requirements of the sheet metal unit for further processing and application can be met particularly economically. Where the first surface layer may contain the second alloying element, namely aluminum, and the fourth alloying element, namely zinc, the coating further provides active corrosion protection and can be used, for example, without the need for painting.

[0013] In one exemplary embodiment, the alloying elements in the alloy of the first initial coating may be specified to have the following weight percentages:

[0014] - Titanium: less than or equal to 10% by weight, preferably 2.5 to 7.5% by weight, particularly preferably 2.5 to 5% by weight, and

[0015] - Aluminum: less than or equal to 20% by weight, preferably 5 to 15% by weight, particularly preferably 5 to 10% by weight, and

[0016] - Manganese: less than or equal to 55% by weight, preferably 30 to 55% by weight, particularly preferably 35 to 45% by weight, and

[0017] Zinc: less than or equal to 45% by weight, preferably 25 to 45% by weight, particularly preferably 35 to 42.5% by weight, and preferably...

[0018] - The remainder consists of unavoidable impurities and / or associated elements.

[0019] Extensive proprietary analysis has shown that only these weight percentages can meet all the requirements for further processing and application of the sheet metal unit.

[0020] In one specific embodiment, the alloying elements in the alloy of the first initial coating may be specified to have the following weight ratios:

[0021] - The weight ratio of titanium to aluminum is 1:2, and / or

[0022] - The weight ratio of zinc to manganese is 1:2, and / or

[0023] - The weight ratio of titanium to aluminum to zinc to manganese is 1:2:7:10.

[0024] Extensive proprietary analysis has shown that, at these weight ratios, the requirements according to the invention can be met particularly well and effectively.

[0025] In one specific embodiment, it may be specified that, during the coating step, a second initial coating identical to the first initial coating is applied to the second surface of the metal sheet. Preferably, during the heating step, alloying elements in the single layer of the second initial coating segregate to form a second coating system identical to the first coating system. In further processing and application, having a double-sided coating is particularly advantageous. This avoids the need for additional cleaning and protection measures on the uncoated metal sheet surface.

[0026] Furthermore, according to the present invention, a sheet metal unit, preferably as described above, comprising a metal plate, preferably a metal plate according to any one of the preceding claims, and a first coating system disposed on the metal plate and / or a second coating system disposed on the metal plate, preferably a coating system according to any one of the preceding claims, wherein the first coating system preferably comprises substantially three layers, namely a first connecting layer and preferably a graded first intermediate layer and a first surface layer, and / or the second coating system substantially comprises three layers, namely a second connecting layer and preferably a graded second intermediate layer and a second surface layer, wherein, particularly preferably, the first connecting layer and / or the second connecting layer primarily, preferably only, a first alloying element, namely titanium, and / or the first intermediate layer and / or the second intermediate layer primarily, preferably only, a third alloying element, namely manganese, and a fourth alloying element, namely zinc, and / or the first surface layer and / or the second surface layer comprises a second alloying element, preferably substantially aluminum, and / or a fourth alloying element, namely zinc. This sheet metal unit has the same advantages already mentioned in relation to the method.

[0027] The embodiments of the present invention are described below with reference to the accompanying drawings.

[0028] In the attached diagram:

[0029] Figure 1 A purely schematic flowchart illustrates a method for manufacturing a sheet metal unit with a first coating system, and

[0030] Figure 2 A sheet metal unit with a first conversion coating and a second coating system is shown in a side view.

[0031] exist Figure 1A method for manufacturing sheet metal unit 1 is shown. The method includes a providing step I, in which a metal sheet 3 is provided. The metal sheet 3 is here formed, exemplarily only, from a sheet metal blank. Of course, in all embodiments of sheet metal unit 1, the metal sheet 3 may also be formed, exemplarily, from a long strip of metal sheet or, exemplarily, from a sheet metal roll.

[0032] The material of metal plate 3 is, by way of example only, a hardenable steel material, which preferably belongs to the material category used to manufacture the highest strength steel plate components. This hardenable steel has a strength R that is preferably greater than 980 MPa, preferably greater than 1180 MPa, and particularly preferably greater than 1650 MPa. M The material of the metal sheet, preferably an alloy of the metal sheet, hereby exemplarily contains the following alloying elements in weight percentage (wt%):

[0033] - Carbon, in the weight percentage range of 0.20 wt% to 0.42 wt%, preferably in the range of 0.30 wt% to 0.38 wt%, and

[0034] - Silicon, with a weight percentage of less than or equal to 2.2% by weight, preferably in the range of 1.0% to 1.8% by weight, and

[0035] - Manganese, in a weight percentage ranging from 0.6 wt% to 3.5 wt%, preferably from 0.8 wt% to 2.0 wt%, and

[0036] - Boron, in a weight percentage of 0.001% to 0.1% (preferably in the range of 0.003% to 0.005% (wt)), and

[0037] - Nitrogen, with a weight fraction less than or equal to 0.01% by weight, and

[0038] - Sulfur, with a weight fraction less than or equal to 0.01% by weight, and

[0039] - Phosphorus, in a weight fraction of less than or equal to 0.02% by weight, and preferably

[0040] - Alloy residue consisting of iron and / or impurities.

[0041] In terms of timing, after providing step I, a coating step II is performed in the method. In coating step II, a coating material is applied to the first surface 5 of the metal plate 3 to form a first initial coating 7 of the metal disposed on the first surface. The coating material in coating step II is, here only exemplarily, deposited on the first surface by means of physical vapor deposition (PVD). The metal plate 3 and the first initial coating 7 together form the plate unit 1.

[0042] The alloy of the initial coating 7 has titanium as the first alloying element, aluminum as the second alloying element, manganese as the third alloying element, and zinc as the fourth alloying element. The alloying elements in the first initial coating 7 may, by way of example only, have the following weight percentages in the following weight percentages:

[0043] - Titanium: 5% by weight, and

[0044] - Aluminum: 10% by weight, and

[0045] - Manganese: 50% by weight, and

[0046] - Zinc: 35% by weight, and preferred

[0047] - The remainder consists of unavoidable impurities and / or associated elements.

[0048] For the sake of completeness, it is hereby reiterated that the alloying elements in the alloy of the first initial coating 7 may, by way of example only, have the following weight percentages in weight percentage:

[0049] - Titanium: less than or equal to 10% by weight, preferably 2.5 to 7.5% by weight, particularly preferably 2.5 to 5% by weight, and

[0050] - Aluminum: less than or equal to 20% by weight, preferably 5 to 15% by weight, particularly preferably 5 to 10% by weight, and

[0051] - Manganese: less than or equal to 55% by weight, preferably 30 to 55% by weight, particularly preferably 35 to 45% by weight, and

[0052] Zinc: less than or equal to 45% by weight, preferably 25 to 45% by weight, particularly preferably 35 to 42.5% by weight, and preferably...

[0053] The remainder consists of unavoidable impurities and / or associated elements.

[0054] Furthermore, the alloying elements in the first initial coating 7 can preferably have the following weight ratios:

[0055] - The weight ratio of titanium to aluminum is 1:2, and / or

[0056] - The weight ratio of zinc to manganese is 1:2, and / or

[0057] - The weight ratio of titanium to aluminum to zinc to manganese is 1:2:7:10.

[0058] After coating step II is completed, the initial coating 7 initially exists as a single layer, that is, the first initial coating 7 has only one layer in which all alloying elements of the alloy of the initial coating 7 are uniformly distributed and uniformly mixed with each other.

[0059] In terms of timing, after coating step II, heating step III is performed in this method. In heating step III, the sheet metal unit 1 is heated at least to the austenitizing temperature AC1, preferably AC3, of the alloy of the metal sheet 3 using heating device 8. During heating step III, i.e., from reaching the austenitizing temperature AC1, preferably AC3, of the alloy of the metal sheet 3, the single-layer first initial coating 7 is transformed into a three-layer first coating system 9. Specifically, during heating step III, the alloying elements in the single layer of the first initial coating 7 segregate in the formation of the first coating system, and specifically, the segregation occurs such that the first coating system substantially has exactly three layers and / or three layers after the alloying element segregation. One of the three layers is a first connecting layer 11, one of the three layers is a graded first intermediate layer 13, and one of the three layers is a first surface layer 15.

[0060] The first connecting layer 11 is disposed between the metal plate 3 and the first intermediate layer 13, and serves to improve the adhesion of the first intermediate layer on the metal plate 3 and act as a barrier between intermetallic phases, thereby preventing iron from diffusing from the metal plate 3 into the first intermediate layer 13. The first intermediate layer 13 is disposed between the first connecting layer 11 and the first surface layer 15, which helps to form a passivation layer, increases the melting point, and improves solderability and hot formability. The first surface layer 15 serves as an anti-oxidation layer and / or an anti-oxidation layer. The surface of the first surface layer 15 facing away from the first intermediate layer 13 may be covered with a paint layer (not shown).

[0061] The first connecting layer 11 may have a thickness ranging from 0.05 µm to 5 µm. The first intermediate layer 13 may have a thickness ranging from 0.1 µm to 10 µm. The first surface layer 15 may have a thickness ranging from 0.05 µm to 5 µm. The first intermediate layer 13 has a thickness at least twice, preferably at least five times, greater than that of the first connecting layer 11 or the first surface layer 15.

[0062] In the first connecting layer 11, the content of the first alloying element, titanium, by weight percentage is at least 50%, preferably 100%, higher than that in the first initial coating 7. All four alloying elements are present in the first intermediate layer 11, wherein the third alloying element, manganese, and the fourth alloying element, zinc, together constitute at least 60%, preferably 70%, by weight. In the first surface layer 15, the content of the second alloying element, aluminum, and / or the fourth alloying element, zinc, by weight percentage is at least 50%, preferably 100%, higher than that in the first initial coating 7.

[0063] Upon mechanical damage, such as scratches or stone impacts, the first coating system 9 locally forms a water-insoluble, passive anti-corrosion coating under the action of corrosive media, such as alkali metal salts, preferably NaCl, and atmospheric oxygen. This coating blocks the corrosive attack of the corrosive media. In other words, the first intermediate layer 13, containing zinc and manganese, together with NaCl, forms a so-called "galvanic cell" in which an electrochemical reaction can occur. Contact between the first intermediate layer 13 and atmospheric oxygen and the corrosive media, i.e., NaCl, is achieved through damage. Atmospheric oxygen and / or zinc advantageously contribute to the formation of the anti-corrosion coating. The anti-corrosion coating is a black solid layer and may contain at least manganese oxide and / or zinc oxide and / or a mixture of zinc and manganese oxides. Because the anti-corrosion coating is water-insoluble and fixed in position, no red rust corrosion products subsequently appear. Another advantageous improvement of the invention is that a fourth alloying element, namely zinc, is present in the first surface layer 15, thereby additionally providing corrosion protection through zinc and / or zinc oxide when there is no paint layer or damage to the surface paint layer.

[0064] The method has been described above only with reference to the first coating system 9. Of course, a second coating system 17, obtained in the same manner as the first coating system 9, can be applied to the second surface 16 of the metal plate 3. The second coating system 17 has a second connecting layer 19, which is preferably identical to the first connecting layer 11 in terms of structure, material, layer thickness, arrangement, and function. The second coating system 17 has a second intermediate layer 21, which is preferably identical to the first intermediate layer 13 in terms of structure, material, layer thickness, arrangement, and function. The second coating system 17 has a second surface layer 23, which is preferably identical to the first surface layer 15 in terms of structure, material, layer thickness, arrangement, and function. Corresponding to the first coating system 9, in the second coating system 17, the second connecting layer 19 is also arranged between the metal plate 3 and the second intermediate layer 21. Furthermore, the second intermediate layer 21 is arranged between the second connecting layer 21 and the second surface layer.

[0065] The method may also include a further processing step in which the sheet metal unit 1, having the metal plate 3 and the first coating system 9 and / or the second coating system 17, is further processed into a hardened steel plate component through cold forming and / or hot forming and / or pressure hardening processes. This steel plate component can be used as a vehicle body component and / or structural component and / or vehicle chassis component.

[0066] List of reference numerals

[0067] 1. Sheet metal unit

[0068] 3 Metal Plates

[0069] 5 First Surface

[0070] 7 First initial coating

[0071] 8. Heating equipment

[0072] 9 First Coating System

[0073] 11 First Connector Layer

[0074] 13 First Intermediate Layer

[0075] 15 First surface layer

[0076] 16 Second Surface

[0077] 17 Second Coating System

[0078] 19 Second Connecting Layer

[0079] 21 Second Intermediate Layer

[0080] 23 Second Surface Layer

[0081] I provide steps

[0082] II. Coating Step

[0083] III. Heating Step

Claims

1. A method for manufacturing sheet metal units, and preferably for further processing the sheet metal units, comprising: In the coating step (II), a first initial coating (7), preferably a single layer, is applied to the first surface (5) of the metal plate (3), thereby forming a plate unit (1) having the metal plate (3) and at least the first initial coating (7), and Heating step (III), in which the plate unit (1) is heated to or above the heating temperature, Its features are, The alloy of the first initial coating (7) of the preferred metal has titanium as the first alloying element, aluminum as the second alloying element, manganese as the third alloying element and zinc as the fourth alloying element.

2. The method according to claim 1, characterized in that, The heating temperature is in the range of 300°C to 1100°C, preferably in the range of 450°C to 1000°C, particularly preferably in the range of 550°C to 1000°C, most preferably in the range of 700°C to 950°C, and / or the heating temperature corresponds to the austenitizing temperature AC1 of the alloy of the metal plate (3), and / or the heating temperature corresponds to the austenitizing temperature AC3 of the alloy of the metal plate (3).

3. The method according to claim 1 or 2, characterized in that, The first initial coating (7) is a single layer and / or has only one layer after the coating step (II) is completed and / or before the heating step (III) begins and / or before the heating temperature is reached, wherein it is preferably specified that all alloying elements are uniformly distributed and / or uniformly mixed with each other in the single layer.

4. The method according to any one of the preceding claims, characterized in that, During the heating step (III), preferably when the heating temperature is reached, the first initial coating (7) preferably a single layer is transformed into a first coating system (9) preferably three layers, and / or the alloying elements in the only layer of the first initial coating (7) segregate in the formation of the first coating system (9), wherein it is preferably specified that the first coating system (9) mainly, preferably exactly, has three layers after the alloying elements segregate, namely a first connecting layer (11) and a first intermediate layer (13) preferably graded and a first surface layer (15).

5. The method according to claim 3 or 4, characterized in that, The first initial coating (7) is the only layer that, during the heating step (III), preferably when the heating temperature is reached, is transformed into the first coating system and / or the alloying elements are segregated such that the first connecting layer (11) is arranged between the metal plate (3) and the first intermediate layer (13), and / or the first intermediate layer (13) is arranged between the first connecting layer (11) and the first surface layer (15), and / or the surface of the first surface layer (15) facing away from the intermediate layer (13) is not covered by any additional coating and / or is covered by a paint layer.

6. The method according to claim 5, characterized in that, The first connecting layer (11) mainly, preferably only has a first alloying element, namely titanium, and / or the first intermediate layer (13) mainly, preferably only has a third alloying element, namely manganese, and a fourth alloying element, namely zinc, and / or the first surface layer (15) has a second alloying element, namely aluminum, and / or a fourth alloying element, namely zinc.

7. The method according to claim 5 or 6, characterized in that, The first alloying element, namely titanium, is present in the first connecting layer (11), preferably in the core of the first connecting layer (11), having a weight percentage at least 50%, preferably 100%, higher than that in the first initial coating (7), and / or the third alloying element, namely manganese, and the fourth alloying element, namely zinc, are present in the first intermediate layer (13), preferably in the core of the first intermediate layer (13), having a total weight percentage at least 60%, preferably 70%, higher than that in the first initial coating (7), and / or the second alloying element, namely aluminum, is present in the first surface layer (15), preferably in the core of the first surface layer (15), and / or the fourth alloying element, namely zinc, having a weight percentage at least 50%, preferably 100%, higher than that in the first initial coating (7).

8. The method according to any one of the preceding claims, characterized in that, The alloying elements in the first initial coating (7) have the following weight percentages in weight percentage: - Titanium: less than or equal to 10% by weight, preferably 2.5 to 7.5% by weight, particularly preferably 2.5 to 5% by weight, and - Aluminum: less than or equal to 20% by weight, preferably 5 to 15% by weight, particularly preferably 5 to 10% by weight, and - Manganese: less than or equal to 55% by weight, preferably 30 to 55% by weight, particularly preferably 35 to 45% by weight, and - Zinc: less than or equal to 45% by weight, preferably 25 to 45% by weight, particularly preferably 35 to 42.5% by weight, and preferably... - The remainder consists of unavoidable impurities and / or associated elements.

9. The method according to any one of the preceding claims, characterized in that, The alloying elements in the first initial coating (7) have the following weight ratios: - The weight ratio of titanium to aluminum is 1:2, and / or - The weight ratio of zinc to manganese is 1:2, and / or - The weight ratio of titanium to aluminum to zinc to manganese is 1:2:7:

10.

10. The method according to any one of the preceding claims, characterized in that, In the coating step (II), a second initial coating identical to the first initial coating (7) is applied to the second surface (16) of the metal plate (3), wherein it is preferably specified that during the heating step (III), the alloying elements in the only layer of the second initial coating segregate in the case of forming a second coating system (17) identical to the first coating system (9).

11. A sheet metal unit, preferably a sheet metal unit according to any one of the preceding claims, comprising: Metal plate (3), preferably a metal plate according to any one of the preceding claims, and A first coating system (9) disposed on the metal plate (3), preferably the first coating system (9) according to any one of the preceding claims, and / or a second coating system (17) disposed on the metal plate (3), preferably the second coating system (17) according to any one of the preceding claims. Preferably, the first coating system (9) has essentially three layers: a first connecting layer (11), a preferred graded first intermediate layer (13), and a first surface layer (15); and / or the second coating system has essentially three layers: a second connecting layer (19), a preferred graded second intermediate layer (21), and a second surface layer (23). In particular, it is specified that the first connecting layer (11) and / or the second connecting layer (19) mainly and preferably only have a first alloying element, namely titanium, and / or the first intermediate layer (13) and / or the second intermediate layer (21) mainly and preferably only have a third alloying element, namely manganese, and a fourth alloying element, namely zinc, and / or the first surface layer (15) and / or the second surface layer (23) have a second alloying element, namely preferably substantially aluminum, and / or a fourth alloying element, namely zinc.

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