METHOD FOR PRODUCING COMPONENTS AND COMPONENTS PRODUCED IN ACCORDANCE WITH SAID METHOD

Abstract

A method for producing components, in particular for energy systems such as fuel cells or electrolyzers, has the following steps: rolling-off a metal sheet having a thickness of less than 500 m, from a first roll; transporting the metal sheet through at least one coating plant in which the metal sheet is coated on at least one side by means of a physical and/or chemical vapor deposition process; performance of at least one forming process on the coated metal sheet; formation of a plurality of components by parting from the coated metal sheet; and rolling-up of the remaining coated metal sheet to give a second roll, with continuous transport of the metal sheet from the first roll to the second roll being carried out.

Claims

1. A process for producing components, in particular components for energy systems such as fuel cells or electrolyzers, the process comprising: providing a first roll of metal sheet having a thickness of less than 500 m; rolling-off the metal sheet from the first roll by transporting a first end of the first roll in a direction of advance; transporting the first end of the first roll and subsequent regions of the metal sheet through at least one coating plant in which the metal sheet is coated on at least one side by means of a physical and/or chemical vapor deposition process; performing at least one forming process on the coated metal sheet; forming a plurality of components by parting from the coated metal sheet; and rolling-up the remaining coated metal sheet to give a second roll, with continuous transport of the metal sheet from the first roll to the second roll being carried out.

2. The process as claimed in claim 1, wherein the at least one forming process comprises deep drawing or extrusion or hydroforming.

3. The process as claimed in claim 1, wherein a layer system comprising a covering layer facing away from the metal sheet is applied to the metal sheet by means of the at least one coating plant, with the covering layer being formed by a homogeneous or heterogeneous solid metallic solution which either contains a first chemical element from the group of the noble metals in the form of iridium in a concentration of at least 99% or contains a first chemical element from the group of the noble metals in the form of iridium and a second chemical element from the group of the noble metals in the form of ruthenium, with the first chemical element and the second chemical element being present in a total concentration of at least 99%, and additionally contains at least one nonmetallic chemical element from the group consisting of nitrogen, carbon, and fluorine.

4. The process as claimed in claim 3, wherein the layer system further comprises an undercoat layer system where the undercoat layer system comprises at least one undercoat layer comprising at least one chemical element from the group consisting of titanium, niobium, hafnium, zirconium, and tantalum.

5. The process as claimed in claim 4, wherein the at least one undercoat layer comprises: a first undercoat layer in the form of a metallic alloy layer comprising the chemical elements titanium and niobium; and a second undercoat layer comprising at least one chemical element from the group consisting of titanium, niobium, hafnium, zirconium, tantalum and additionally at least one nonmetallic element from the group consisting of nitrogen, carbon, boron, fluorine.

6. The process as claimed in claim 5, wherein the second undercoat layer is arranged between the first undercoat layer and the covering layer.

7. A bipolar plate comprising at least one component which has been produced as claimed in claim 1.

8. The bipolar plate as claimed in claim 7, wherein the at least one component comprises two components which are joined to one another by bonding.

9. A fuel cell, in particular polymer electrolyte fuel cell, comprising at least one bipolar plate as claimed in claim 7.

10. An electrolyzer comprising at least one bipolar plate as claimed in claim 7.

11. A process for producing energy systems, the process comprising: continuously transporting a metal sheet having a thickness of less than 500 m from a first roller to a second roller; coating the metal sheet with an undercoat layer system comprising at least one undercoat layer comprising at least one chemical element from the group consisting of titanium, niobium, hafnium, zirconium, and tantalum; coating the metal sheet with covering layer formed by a homogeneous or heterogeneous solid metallic solution; performing at least one forming process on the coated metal sheet; and forming a plurality of components by parting from the coated metal sheet.

12. The process as claimed in claim 11, wherein the homogeneous or heterogeneous solid metallic solution contains: a first chemical element from the group of the noble metals in the form of iridium in a concentration of at least 99%; and at least one nonmetallic chemical element from the group consisting of nitrogen, carbon, and fluorine.

13. The process as claimed in claim 11, wherein the homogeneous or heterogeneous solid metallic solution contains: a first chemical element from the group of the noble metals in the form of iridium and a second chemical element from the group of the noble metals in the form of ruthenium, with the first chemical element and the second chemical element being present in a total concentration of at least 99%; and at least one nonmetallic chemical element from the group consisting of nitrogen, carbon, and fluorine.

14. The process as claimed in claim 11, wherein the at least one undercoat layer comprises: a first undercoat layer in the form of a metallic alloy layer comprising the chemical elements titanium and niobium and a second undercoat layer comprising at least one chemical element from the group consisting of titanium, niobium, hafnium, zirconium, tantalum and additionally at least one nonmetallic element from the group consisting of nitrogen, carbon, boron, fluorine.

15. The process as claimed in claim 14, wherein the second undercoat layer is arranged between the first undercoat layer and the covering layer.

16. The process as claimed in claim 11, further comprising bonding two components of the plurality of components to one another to form a bipolar plate.

17. A bipolar plate comprising two components bonded to one another, each component comprising: a sheet metal substrate having a thickness of less than 500 m; an undercoat layer system comprising at least one undercoat layer comprising at least one chemical element from the group consisting of titanium, niobium, hafnium, zirconium, and tantalum; and a covering layer formed by a homogeneous or heterogeneous solid metallic solution.

18. The bipolar plate as claimed in claim 17, wherein the homogeneous or heterogeneous solid metallic solution contains: a first chemical element from the group of the noble metals in the form of iridium in a concentration of at least 99%; and at least one nonmetallic chemical element from the group consisting of nitrogen, carbon, and fluorine.

19. The bipolar plate as claimed in claim 17, wherein the homogeneous or heterogeneous solid metallic solution contains: a first chemical element from the group of the noble metals in the form of iridium and a second chemical element from the group of the noble metals in the form of ruthenium, with the first chemical element and the second chemical element being present in a total concentration of at least 99%; and at least one nonmetallic chemical element from the group consisting of nitrogen, carbon, and fluorine.

20. The bipolar plate as claimed in claim 17, wherein the at least one undercoat layer comprises: a first undercoat layer in the form of a metallic alloy layer comprising the chemical elements titanium and niobium and a second undercoat layer, arranged between the first undercoat layer and the covering layer, comprising at least one chemical element from the group consisting of titanium, niobium, hafnium, zirconium, tantalum and additionally at least one nonmetallic element from the group consisting of nitrogen, carbon, boron, fluorine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Further advantages, features and details may be derived from the following description of preferred working examples and the figures.

[0056] The features and feature combinations mentioned above in the description can be used not only in the combination indicated in each case but also in other combinations or alone.

[0057] The figures thus show:

[0058] FIG. 1 a schematic process flow diagram for the proposed process;

[0059] FIG. 2 a component formed by the proposed process; and

[0060] FIG. 3 a section through the component of FIG. 2 in the region of the applied layer system.

DETAILED DESCRIPTION

[0061] FIG. 1 schematically shows a process flow diagram for the proposed process for producing components 1a, 1b, 1c, in which a first roll 20 of metal sheet 2 is provided and the metal sheet 2 is rolled off from a first reel 30 and transported in the direction of a second reel 30 in a roll-to-roll process.

[0062] A thickness of the material of the metal sheet 2 is less than 500 m.

[0063] The first end of the first roll 20 and subsequent metal sheet regions are transported through at least one first coating plant 200a in which the undercoat layer system 4 (cf FIG. 3) is produced. The metal sheet 2 is coated on at least one side by means of a physical and/or chemical vapor deposition process, with full-area or only partial coating of the metal sheet 2 carried out.

[0064] The metal strip 2 and subsequent metal sheet regions are transported through at least one second coating plant 200b in which the covering layer 3a (cf FIG. 3) is produced. The metal sheet 2 is coated on at least one side by means of a physical and/or chemical vapor deposition process, at least in the region of the undercoat layer system 4.

[0065] The coated metal sheet 2 is then transported into at least one forming unit 300. There, forming processes are carried out on the coated metal sheet 2, in particular to produce gas distributor structures 5. Here, the coated metal sheet 2 is deformed three-dimensionally, and optionally provided with slots or cut-outs in a further forming and/or shear cutting unit 400. The coated and formed metal sheet 2 is fed to a stamping unit 500 in order to produce a plurality of components 1a, 1b, 1c. Parting of the components 1a, 1b, 1c from the coated, formed metal sheet 2 is carried out. The components 1a, 1b, 1c are transported away by means of a transport unit 600.

[0066] The remaining coated metal sheet 2 is rolled up by means of the second reel 30 to give a second roll 20, with the metal sheet 2 being transported continuously from the first roll 20 to the second roll 20. Processing of the metal strip 2 is carried out in an efficient and cost-saving manner in an in-line process.

[0067] It can be necessary to cool the coated metal sheet after passage through the at least one coating plant. For this reason, at least one cooling chamber can be installed between the at least one coating plant and the at least one forming unit. Furthermore, the at least one coating plant can be preceded by at least one vacuum chamber which serves not only for optional preheating or heating of the metal strip but especially for setting the required atmospheric pressure over the metal strip before it goes into the at least one coating plant. Thus, a physical and/or chemical vapor deposition process is usually carried out under reduced pressure.

[0068] FIG. 2 shows components 1a, 1b having gas distributor structures 5 produced by the process depicted in FIG. 1, with the components 1a, 1b having been joined together by laser welding to give a bipolar plate 10. Each component 1a, 1b has a layer system 3 comprising a covering layer 3a. Reference numerals which are the same as in FIG. 1 denote identical elements.

[0069] FIG. 3 shows a section through the component 1a of FIG. 2 in the region of the applied layer system 3. The layer system 3 has been applied over the full area of one side of the metal sheet 2 composed of stainless steel. The layer system 3 comprises the covering layer 3a and the undercoat layer system 4 comprising a first undercoat layer 4a and a second undercoat layer 4b.

[0070] The metal sheet 2 has been made in the form of a conductor, here for a bipolar plate 10 of a polymer electrolyte fuel cell for the reaction of (reformed) hydrogen, from a stainless steel, in particular from an austenitic steel which satisfies very high known demands in respect of corrosion resistance, e.g. having the DIN ISO material number 1.4404.

[0071] The layer system 3 is produced on the metal sheet 2 by means of a coating process, for example a vacuum-based coating process (PVD), with the metal sheet 2 being coated in one process pass firstly with a first undercoat layer 4a, for example in the form of a 0.5 m thick titanium layer, subsequently with a second undercoat layer 4b, for example in the form of a 1 m thick titanium nitride layer, and subsequently with the covering layer 3a, for example in the form of a 10 nm thick iridium-carbon layer. The covering layer 3a corresponds to a layer which is open on one side since only one covering layer surface is in contact with a further layer, here the second undercoat layer 4b. Thus, a free surface of the covering layer 3a in a fuel cell is arranged directly adjoining an electrolyte, in particular a polymer electrolyte, and is exposed thereto.

[0072] In a second working example, the metal sheet 2 for the bipolar plate 10 is firstly coated with a first undercoat layer 4a in the form of a metallic alloy layer having a thickness of 100 nm, with the metallic alloy layer having the composition Ti.sub.0.67 Nb.sub.0.33. A second undercoat layer 4b having a thickness of 400 nm and the composition (Ti.sub.0.67Nb.sub.0.33).sub.1-xN.sub.x where x=0.40-0.55 is subsequently applied. A covering layer 3a having a thickness of 10 nm and the composition iridium-carbon is then applied on top.

[0073] The advantage is an extraordinarily high stability against oxidation of the bipolar plate 10. Even at long-term application of +3000 mV relative to a standard hydrogen electrode, no increase in resistance is found in sulfuric acid solution having a pH of 3. In terms of external appearance, the free surface of the covering layer 3a, thus the surface of the covering layer 3a facing away from the metal sheet 2, remains shiny and silvery even after application of +2000 mV relative to a standard hydrogen electrode for 50 hours. Even under a scanning electron microscope, no traces of corrosion extending through the thickness of the covering layer 3a to the metal sheet 2 or reaching the metal sheet 2 can be seen.

[0074] The covering layer 3a of the second working example can be applied either by means of the vacuum-based PVD sputtering technique or by means of a cathodic ARC coating process, also known as vacuum arc deposition. Despite a higher number of droplets, in other words a number of metal droplets higher than in the sputtering technique, the covering layer 3a produced in the cathodic ARC process also has the advantageous properties of high corrosion resistance combined with time-stable surface conductivity of the covering layer 3a produced by means of the sputtering technique.

[0075] In a third working example, the layer system 3 is produced on a metal sheet 2 in the form of a structured perforated stainless steel sheet. The metal sheet 2 has been electrolytically polished in an H.sub.2SO.sub.4/H.sub.3PO.sub.4 bath before application of a layer system 3. After application of a single undercoat layer in the form of a tantalum carbide layer having a thickness of several 1000 nm, a covering layer 3a in the form of an iridium-carbon layer having a thickness of several 100 nm is applied.

[0076] The advantage of the undercoat layer composed of the tantalum carbide is not only its extraordinary corrosion resistance but also the fact that it does not absorb any hydrogen and thus serves as hydrogen barrier for the metal sheet 2. This is particularly advantageous when titanium is used as metal sheet.

[0077] The layer system 3 of the third working example is suitable for use in an electrolysis cell for producing hydrogen at current densities which are greater than 500 mA cm.sup.2.

[0078] The advantage of the metalloid layer or the second undercoat layer, which in the simplest case is composed of, for example, titanium nitride, which is located in an intermediate position in the layer system and/or is closed on both sides is its low electrical resistance of 10-12 mcm.sup.2. The covering layer can likewise also be produced without a second undercoat layer or metalloid layer, with a possible increase in resistance.

[0079] Some layer systems with their characteristic values are shown by way of example in Table 1.

TABLE-US-00001 TABLE 1 Layers and selected characteristic values Corrosion current 2000 mV relative to Specific standard hydrogen Oxidation stability at surface electrode in A cm.sup.2 2000 mV measured as resistance in in aqueous sulfuric change in the surface Layer system/layer m cm.sup.2 acid solution resistance in m cm.sup.2 thickness at T = 20 C. (pH = 3) at T = 80 C. Target value: <20 m cm.sup.2 1 Gold/3 m 9 >100 pitting current 9-10 (as reference) 2 Ti/0.5 m 8 0.001 12 TiN/1 m Ir.sub.0.99C.sub.0.01/10 nm 3 Ti.sub.0.67Nb.sub.0.33/0.1 m 7-8 0.01 1-2 (Ti.sub.0.67Nb.sub.0.33).sub.1xN.sub.x where x = 0.40-0.55/0.4 m Ir.sub.0.99C.sub.0.01/10 nm 4 Zr/0.5 m 11 0.001 11-12 ZrN/1 m Ir.sub.0.99C.sub.0.01/10 nm 5 Ta/0.05 m 10 0.001 17-18 TaC/0.5 m Ir.sub.0.991C.sub.0.009/5 nm 6 ZrB.sub.2/0.3 m 7 Pitting reaction after Ir.sub.0.7B.sub.0.3/5 nm 4 hours exposure

[0080] Only some illustrative layer systems are shown in Table 1. The layer systems advantageously display no increase in resistance at an anodic stress of +2000 mV relative to a standard hydrogen electrode in sulfuric acid solution at a temperature of 80 C. over a number of weeks. The layer systems applied in high vacuum by means of a sputtering or ARC process or in a fine vacuum by means of PECVD processes (plasma-enhanced chemical vapor deposition processes) had in some cases acquired a dark discoloration after this time of exposure. However, no visible corrosion phenomena or significant changes in surface resistances occurred.

LIST OF REFERENCE NUMERALS

[0081] 1a, 1b, 1c component [0082] 2 metal sheet [0083] 2 coated metal sheet [0084] 2 coated and formed metal sheet [0085] 2 remaining metal sheet [0086] 3 layer system [0087] 3a covering layer [0088] 4 undercoat layer system [0089] 4a first undercoat layer [0090] 4b second undercoat layer [0091] 5 gas distributor structure [0092] 10 bipolar plate [0093] 20 first roll of metal sheet [0094] 20 second roll of remaining metal sheet [0095] 30, 30 reel [0096] 100 plant [0097] 200a, 200b coating unit(s) [0098] 300 forming unit(s) [0099] 400 forming and/or shear cutting unit [0100] 500 stamping unit [0101] 600 transport unit