Cutting blade and method for the production thereof

Abstract

The present invention relates to a cutting blade and to a method for the production thereof. The cutting blade has a metallic substrate having a first cutting face and a second cutting face that form a cutting edge, wherein a DLC hardcoat layer has been deposited on the substrate as outer layer and wherein the outer layer has a hardness of at least (30) GPa and a roughness of not more than 0.15 µm Ra with a layer thickness of 1 to 5 µm.

Description

[0001] Cutting blade and method for its manufacture

[0002] The present invention relates to a cutting blade and a method for its production. The cutting blade has a metallic substrate with a first cutting surface and a second cutting surface enclosing a cutting edge, wherein a DLC hard material layer is deposited on the substrate as a cover layer, and wherein the cover layer has a hardness of at least 30 GPa and a roughness of a maximum of 0.15 μm Ra with a layer thickness of 1 to 5 μm. According to the prior art, there are numerous inventions whose aim is to optimize the cutting performance of knives, blades, scissors, or similar tools through coatings. However, all of the documents listed below are not applicable, or only applicable to a limited extent, for household cutting blades made of conventional stainless steels according to DIN EN 10020 (July 2000).

[0003] For example, EP 2495 081 B1 describes a cutting tool with a coating of fine-crystalline diamond. This is applied using a hot-wire CVD process at typical substrate temperatures between 600°C and 900°C. The substrate consists of temperature-resistant materials such as titanium, nickel, niobium, tungsten, hard metals, or ceramics. These temperatures are significantly higher than the tempering temperature of stainless steels. Changing the material to one of these materials would also lead to a significant cost increase for household knives.

[0004] US Pat. No. 6,289,593 B1 describes a razor blade with a DLC coating and an edge rounding of less than 1200 angstroms (equivalent to 0.12 μm) and a coating thickness of at least 400 to 2000 angstroms (equivalent to 0.04 μm to 0.2 μm). However, such small edge roundings and thin coating thicknesses are not sufficient to significantly increase the edge retention of a household knife. This is due to the harsher operating conditions and handling of a household knife compared to a razor blade.

[0005] DE 10 2019 200 681 Al describes a multi-layer cutting tool in which the middle layer consists of hybridized carbon, which forms the cutting edge. Since the layer thickness of such layers is in the micrometer range, a cost-effective implementation is not feasible from a manufacturing technology perspective. This would require the cutting edge to be ground free with micrometer precision, which is a significant expense. The disadvantage of applying thicker layers via thermal spraying is the reduced corrosion resistance of typical stainless steel knife materials. Furthermore, the production of such a described multi-layer structure is not economically feasible for consumer goods, and especially for knives with complex geometries.EP 3 683 332 A1 also describes a coating of hybridized carbon on a carrier substrate, but unlike DE 10 2019 200 681 A1, it has a three-dimensional structure. This structure can be achieved by masking, but this is very complex. In addition to the additional effort, subsequent laser processing has the disadvantage that the corrosion resistance of a stainless steel substrate would be reduced due to the thermal energy input.

[0006] DE 10 2004 052 068 B4 describes a cutting tool with a metal carrier layer and a second layer of diamond-like carbon. Only the maximum edge rounding is defined, not the layer thickness. Both parameters, however, are essential for good initial sharpness and for maintaining cutting performance for as long as possible.

[0007] EP 2 714 964 B1 describes a woodworking tool with a defined layer thickness and rounded cutting edges. However, if the sliding layer claimed here were omitted, which is essential for a cost-effective solution, this would result in different layer thicknesses and edge rounding. This is intended to avoid a cost-intensive multi-layer system consisting of a sliding layer and a functional layer, which is coated in a two-stage process. Furthermore, the document describes a base body made of hard metal, HSS, ceramic, or cermet, which is not a suitable material for household knives.

[0008] DE 10 2015 101 782 B4 describes a sliding layer applied to a DLC coating. This describes a DLC, PLC, or Gr coating that does not reduce roughness or eliminates the increased roughness of the DLC base layer. Furthermore, the affinity of foodstuffs to carbon-containing coatings makes them difficult to clean. In addition, a further PVD or CVD process would be expensive and likely lead to increased cutting edge rounding and thus reduced sharpness.

[0009] EP 1 915 472 B1 also describes a multilayer structure consisting of a hard tetrahedral carbon intermediate layer and a softer amorphous carbon top layer. The disadvantages regarding both the layer application and the layer material itself are the same as in the previously cited patent.

[0010] Based on this, the object of the present invention was to eliminate the disadvantages existing in the prior art and to provide a cutting blade that is both sharp when delivered and maintains its sharpness and cutting performance for as long as possible under increasing load. This should be applicable to all common knife shapes. Furthermore, the coating system or the application of the coating should not negatively affect the knife or its material. Furthermore, the knife should be easy to clean with standard household products, which requires a defined surface structure.

[0011] This object is achieved by the method for producing a cutting blade having the features of claim 1 and the cutting blade having the features of claim 6. The further dependent claims describe preferred embodiments.

[0012] According to the invention, a method for producing a cutting blade is provided, in which a DLC hard material coating is deposited as a cover layer on a substrate having a first cutting surface and a second cutting surface enclosing a cutting edge by means of physical vapor deposition (PVD). The DLC hard material coating has a hardness of at least 30 GPa and a roughness of a maximum of 0.15 pm Ra at a layer thickness of 1 to 5 pm. The corresponding roughness can be achieved using filter methods. One such filter method is described in more detail in EP3143177B1. During the coating process, the carbon is converted into the plasma state by an arc. This plasma consists of micro- and macroparticles. By appropriately selecting the pulse parameters in terms of current and duration, as well as by applying an electrostatic field, the macroparticles are moved away from the substrate.This creates a hard, wear-resistant, and smooth surface. An alternative to customized filters would be layer deposition using a HiPIMS process. HiPIMS technology is a special magnetron sputtering technology with powerful pulses. Sputtering creates smooth coatings with reduced friction. The high power density at the cathode generates ionized atoms, which ensure hard, highly dense coatings with high wear resistance. HiPIMS technology is highly customizable, offering full control over power, current, voltage duty cycle, and pulse on / off times. A particular advantage of HiPIMS technology is the ability to deposit ta-C.

[0013] The hard coating makes the cutting edge wear-resistant, maintaining long-lasting sharpness. The surface texture of the cutting blade with the specified roughness allows the finished product to be cleaned even with standard household cleaning products.

[0014] In contrast to conventional solutions, the invention presents an advantageous solution which ensures both sufficient initial sharpness and long-lasting cutting edge retention.

[0015] It is preferred that the DLC hard material coating contains or consists of amorphous carbon, in particular tetrahedral amorphous carbon. The advantage of a taC DLC coating is its outstanding hardness and thus its wear resistance. Other hard material coatings are also conceivable, which can be applied using PVD, PECVD, CVD, or thermal spraying processes.

[0016] It is preferred that the at least one DLC hard material layer be deposited on the substrate with a thickness in the range of 2 to 4 μm, and preferably 2.5 to 3.5 μm. This achieves good wear resistance.

[0017] It is preferred that the material of the metallic substrate is selected from the group consisting of steel, ceramic, hard metal, and combinations thereof, in particular a stainless steel. A preferred substrate is a stainless steel with at least 10.5% chromium and at most 1.2% carbon, preferably more than 12% chromium and less than 0.8% carbon, particularly preferably more than 14% chromium and 0.4-0.6% carbon. A stainless steel with the steel code 1.4116, 1.4125, 1.4031, 1.4028, 1.4021, 1.4034, 1.4122, or 1.4006 is particularly preferred. Further suitable steel codes can be found at www.edelstahl-rostfrei.de / fileadmin / user_upload / ISER / images / publikationen / Dok_Martensite_final.pdf.

[0018] To enable easy coating application, the DLC layer or another suitable layer can be applied to both sides of the cutting edge or cutting edge.

[0019] It is preferred that an adhesion promoter layer be deposited between the substrate and the DLC hard material layer. The adhesion promoter layer preferably contains or consists of chromium, titanium, or mixtures or alloys thereof.

[0020] The application of the coating or the complete coating process should take place on a stainless steel substrate below 250°C, preferably below 220°C, particularly preferably below 200°C.

[0021] According to the invention, a cutting blade is also provided, comprising a metallic substrate with a first cutting surface and a second cutting surface enclosing a cutting edge, wherein a DLC hard material coating is deposited on the substrate as a cover layer. The DLC hard material coating has a hardness of at least 30 GPa and a roughness of a maximum of 0.15 pm Ra with a layer thickness of 1 to 5 pm.

[0022] It is preferred that the DLC hard material layer contains or consists of amorphous carbon, in particular tetrahedral amorphous carbon.

[0023] Furthermore, it is preferred that the at least one DLC hard material layer has a hardness of 35 GPa, preferably at least 40 GPa.

[0024] It is preferred that the at least one DLC hard material layer has a thickness in the range of 2 to 4 μm, and preferably 2.5 to 3.5 μm. This achieves good wear resistance.

[0025] Good adhesion of the coating to the substrate or cutting edge is also crucial. This should be between HF1 and HF3, preferably between HF1 and HF2, and especially preferably HF1. ​​To optimize the adhesion of the DLC coating to the substrate, an adhesion promoter layer can also be used.

[0026] It is preferred that the angle between the first cutting surface and the second cutting surface be in the range of 15° to 40°, preferably 20° to 35°, and particularly preferably 25° to 32°. This allows for low forces to be applied to separate the materials being cut.

[0027] To achieve sufficient initial sharpness, the rounding of the cutting edge should be less than or equal to 6 pm, preferably from 1.5 to 5 pm, particularly preferably from 2 to 4 pm. This limitation has the advantage of providing sufficient initial sharpness for use.

[0028] It is preferred that an adhesion promoter layer be deposited between the substrate and the DLC hard material layer. The adhesion promoter layer preferably contains or consists of chromium, titanium, or mixtures or alloys thereof.

[0029] The subject matter of the invention will be explained in more detail with reference to the following figures and the example, without wishing to restrict it to the specific embodiments shown here.

[0030] It shows

[0031] Fig.l a sectional view of a first cutting blade according to the invention

[0032] Fig. 2 shows a sectional view of another cutting blade according to the invention with an adhesion promoter layer. Fig. 1 shows a cutting blade 1 according to the invention. The cutting blade 1 consists of a substrate 2, wherein the first cutting surface 3, the second cutting surface 4 and the cutting edge 5 have a coating of a DLC hard material layer 6.

[0033] Fig. 2 shows a further cutting blade 1 according to the invention. The cutting blade 1 consists of a substrate 2, wherein the first cutting surface 3, the second cutting surface 4, and the cutting edge 5 are provided with an adhesion promoter layer 7, on which a coating of a DLC hard material layer 6 is deposited.

[0034] Example

[0035] First, the raw blade is made from the selected material. Depending on the manufacturing process, this can be done by cutting a strip steel knife (using a laser, punching, or similar) or, in the case of a forged blade, by cutting and forging. The blade material is preferably made of a martensitic, corrosion-resistant steel, such as 1.4116 or X50CrMoV15, which offers a good combination of hardness and corrosion resistance. Other steel alloys are also suitable in principle.

[0036] The next step in the process is tempering the blade. This involves hardening the blade in a hardening process and then tempering it one or more times. This two-stage process serves to increase wear resistance and subsequently optimize toughness. Such processes are widespread in industry. To achieve a uniform and fine grain size, normalizing may be required prior to tempering.

[0037] The hardened raw blade is then ground or polished in a process that usually involves several steps. This achieves the final contour in terms of dimensional accuracy, creates an attractive appearance, and improves corrosion resistance. One of the final steps is the attachment or grinding of the cutting edge. The cutting edge angle is typically in the range of 15° to 40°, preferably 20° to 35°, and particularly preferably 25° to 32°. Furthermore, the cutting edge rounding is crucial for initial sharpness. This should have a rounding radius of less than 6 μm, preferably less than 5 μm, and particularly preferably less than 4 μm.

[0038] The DLC coating is then applied. Pre-cleaning (wet-chemical, ultrasonic, etc.) is usually required, as is fine plasma cleaning in the PVD system, if necessary, to activate the surface before the actual DLC coating is applied in the same system. A tetrahedral amorphous coating, which offers outstanding wear resistance, is preferred. The hardness of this coating should be at least 30 GPa. To improve adhesion, a primer layer consisting of or containing chromium or titanium may be required.

[0039] The layer thickness should be applied in the range of 1 to 5 μm, preferably 2 to 4 μm, and particularly preferably 2.5 to 3.5 μm. Good layer adhesion to the substrate or cutting edge is also of great importance. The layer adhesion should be between HF1 and HF3, preferably between HF1 and HF2, and particularly preferably HF1 - tested according to DIN 4856.

Claims

WMF GmbH 239PCT 2662 Patent claims 1. A method for producing a cutting blade (1), in which a DLC hard material layer (6) is deposited as a cover layer on a substrate (2) having a first cutting surface (3) and a second cutting surface (4) which enclose a cutting edge (5) by means of physical vapor deposition (PVD), wherein the DLC hard material layer (6) has a hardness of at least 30 GPa and a roughness of at most 0.15 pm Ra with a layer thickness of 1 to 5 pm.

2. Method according to claim 1, characterized in that the at least one DLC hard material layer (6) contains or consists of amorphous carbon, in particular tetrahedral amorphous carbon.

3. Method according to one of claims 1 or 2, characterized in that the at least one DLC hard material layer (6) is deposited on the substrate (2) with a thickness in the range of 2 to 4 pm and preferably of 2.5 to 3.5 pm.

4. Method according to one of claims 1 to 3, characterized in that the material of the metallic substrate is selected from the group consisting of steel, ceramic, hard metal and combinations thereof, in particular a stainless steel, preferably a stainless steel with the steel key 1.4116, 1.4125, 1.4031, 1.4028, 1.4021, 1.4034, 1.4122 or 1.4006. Method according to one of claims 1 to 4, characterized in that an adhesion promoter layer (7) is deposited between the substrate (2) and the DLC hard material layer (6), wherein the adhesion promoter layer preferably contains or consists of chromium and / or titanium. Cutting blade (1) containing a metallic substrate (2) with a first cutting surface (3) and a second cutting surface (4) which enclose a cutting edge (5), wherein at least one DLC hard material layer (6) is deposited on the substrate (2) as a cover layer with a hardness of at least 30 GPa and a roughness of at most 0.15 pm Ra with a layer thickness of 1 to 5 pm. Cutting blade according to claim 6, characterized in that the at least one DLC hard material layer (6) contains or consists of amorphous carbon, in particular tetrahedrally amorphous carbon.Cutting blade according to one of claims 6 or 7, characterized in that the at least one DLC hard material layer (6) has a hardness of at least 35 GPa, preferably at least 40 GPa. Cutting blade according to one of claims 6 to 8, characterized in that the at least one DLC hard material layer (6) has a thickness in the range of 2 to 4 pm and preferably of 2.5 to 3.5 pm. Cutting blade according to one of claims 6 to 9, characterized in that the material of the metallic substrate. is selected from the group consisting of steel, ceramic, hard metal and combinations thereof, in particular a stainless steel, preferably a stainless steel with the steel key 1.4116.

11. Cutting blade according to one of claims 6 to 10, characterized in that the angle between the first cutting surface (3) and the second cutting surface (4) is in the range from 15° to 40°, preferably from 20° to 35° and particularly preferably from 25° to 32°.

12. Cutting blade according to one of claims 6 to 11, characterized in that the cutting edge (5) has a rounding radius of 1 to 6 pm, preferably of 1.5 to 5 and particularly preferably of 2 to 4 pm.

13. Cutting blade according to one of claims 6 to 12, characterized in that an adhesion promoter layer (7) is deposited between the substrate (2) and the DLC hard material layer (6), the adhesion promoter layer preferably containing or consisting of chromium and / or titanium.

14. Cutting blade according to one of claims 6 to 13 and manufacturable by the method according to one of claims 1 to 4.

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