Cutting blade and manufacturing method thereof

Abstract

The present invention relates to a cutting blade and a method for manufacturing the same. The cutting blade includes a metal substrate having a first cutting surface and a second cutting surface including a cutting edge, and at least one DLC hard material layer is applied to the substrate as a coating layer, and the coating layer has a hardness of at least 30 GPa and a roughness of at most 0.15 μm Ra with a layer thickness in the range of 1 to 5 μm.

Description

[Technical Field]

[0001] The present invention relates to a cutting blade and a method for manufacturing the same. The cutting blade includes a metal substrate having a first cutting surface and a second cutting surface including a cutting edge, and at least one DLC hard material layer is applied to the substrate as a coating layer, and the coating layer has a layer thickness in the range of 1 to 5 μm, a hardness of at least 30 GPa, and a roughness of at most 0.15 μm Ra. [Background technology]

[0002] According to the prior art, there are numerous inventions for using coatings to optimize the cutting performance of knives, cutting implements, scissors or similar tools, however, none of the documents listed below apply, or only to a limited extent apply, to household blades made of conventional stainless steel according to DIN EN 10020 (July 2000).

[0003] For example, Patent Document 1 describes a cutting tool coated with microcrystalline diamond. This coating is applied by a hot-wire CVD method at a typical substrate temperature between 600 and 900°C. The substrate is made of a heat-resistant material such as titanium, nickel, niobium, tungsten, carbide, or ceramic. These temperatures are far higher than the tempering temperature of stainless steel. Changing the material to one of these would also significantly increase the cost of the household knife.

[0004] Patent Document 2 describes a razor blade having a DLC layer, an edge radius of less than 1200 angstroms (corresponding to 0.12 μm), and a layer thickness of at least 400-2000 angstroms (corresponding to 0.04 μm-0.2 μm). However, such small edge radius and layer thickness are not sufficient to significantly increase the edge retention characteristics of a household knife. This is due to the harsher handling conditions of how household knives are handled compared to razor blades.

[0005] Patent Document 3 describes a multilayer cutting tool, the intermediate layer forming the cutting edge of which is made of hybridized carbon. The thickness of such layers is in the micrometer range, making them impossible to manufacture cost-effectively from a manufacturing technology perspective. This is because the cutting edge needs to be ground with micrometer precision, which is very time-consuming. Using thermal spraying to apply thicker layers has the disadvantage of reducing the corrosion resistance of typical stainless steel blade materials. Furthermore, it is not economically feasible to manufacture such multilayer structures for consumer goods, especially knives with complex geometries.

[0006] In contrast to Patent Document 5, Patent Document 4 also describes coating a support substrate with hybrid carbon, which has a three-dimensional structure. This structuring can be achieved by masking, but is very time-consuming. Subsequent laser processing has the disadvantage that the thermal energy input leads to a decrease in the corrosion resistance of the stainless steel substrate.

[0007] Patent Document 6 describes a cutting tool having a metal carrier layer and a second layer of diamond-like carbon. In this example, only the maximum edge radius is defined, not the layer thickness. Both of these parameters are essential for maintaining good initial sharpness and cutting performance over the longest possible service life.

[0008] Patent Document 7 describes a woodworking tool with a cutting edge of defined layer thickness and radius. However, if the sliding layer, which is essential for the cost-effective solution claimed therein, is omitted, this would result in different layer thicknesses and edge radiuses. The aim is to avoid costly multilayer systems consisting of a sliding layer and a functional layer, which are coated in a two-stage process. Furthermore, this document describes substrates made of carbide, HSS, ceramic, or cermet, which are not suitable for household knives.

[0009] Patent Document 8 describes a sliding layer applied to a DLC layer. In this example, it is noted that the DLC or PLC layer does not reduce the roughness or eliminate the increased roughness of the DLC-based layer. Furthermore, the affinity of food products for carbon-based coatings makes them difficult to remove. Additionally, a separate PVD or CVD process would incur high costs and possibly result in increased rounding of the cutting edge, thus reducing sharpness.

[0010] Patent document 9 also describes a multilayer structure consisting of a hard tetrahedral carbon intermediate layer and a softer amorphous carbon coating layer. With regard to the application of the layers and the coating material itself, the issues correspond to those described in the above patent specification. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] European Patent Publication No. 2495081B1 [Patent Document 2] U.S. Patent No. 6,289,593 B1 [Patent Document 3] German Patent Publication No. 102019200681A1 [Patent Document 4] European Patent Publication No. 3683332A1 [Patent Document 5] German Patent No. 102019200681A1 [Patent Document 6] German Patent No. 102004052068B4 [Patent Document 7] European Patent Publication No. 2714964B1 [Patent Document 8] German Patent No. 1015101782B4 [Patent Document 9] European Patent Publication No. 1915472B1 [Patent Document 10] European Patent Publication No. 3143177B1 Summary of the Invention

[0012] Based on this problem, the object of the present invention was to eliminate the problems existing in the prior art and to provide a cutting blade that is sharp at the time of delivery and maintains its sharpness and cutting performance as long as possible even under increasing load. This should apply to all common blade geometries. Furthermore, the coating system or application of the coating should not have a negative effect on the knife and its material. Furthermore, the cutting blade should be easy to clean with standard household products, which requires a defined surface structure.

[0013] This object is solved by a method for manufacturing a cutting blade having the features of claim 1 and by a cutting blade having the features of claim 6. The further dependent claims describe preferred embodiments.

[0014] The present invention provides a method for manufacturing a cutting blade, in which a substrate having a first cutting surface and a second cutting surface, including a cutting edge, is coated with a DLC hard coating as an upper layer by physical vapor deposition (PVD). The DLC hard coating has a coating thickness of 1 to 5 μm, a hardness of at least 30 GPa, and a roughness of at most 0.15 μm Ra. The appropriate roughness can be achieved using a filtering method, which is described in detail in U.S. Patent No. 5,629,493. During the coating process, carbon is converted into a plasma state by an electric arc. This plasma is composed of microparticles and macroparticles. By selecting appropriate pulse parameters in terms of current and duration and applying an electrostatic field, the macroparticles are moved away from the substrate. This results in a hard, wear-resistant, and smooth surface.

[0015] An alternative to customized filters is layer deposition using the HiPIMS process. HiPIMS technology is a special magnetron sputtering technique with powerful pulses. Sputtering is used to produce smooth coatings with reduced friction. A high power density at the cathode creates ionized atoms, ensuring a hard, highly condensed coating with high wear resistance. HiPIMS technology is highly customizable, allowing full control over power, current, voltage duty cycle, and pulse on / off times. A particular advantage of HiPIMS technology is the possibility to deposit ta-C.

[0016] The hard material layer serves to increase wear resistance and ensure long-lasting sharpness, and the surface structure of the cutting edge with specified roughness means that the final product can be washed with standard household cleaning agents.

[0017] Unlike conventional solutions, the present invention provides an advantageous solution that ensures both sufficient initial sharpness and long-lasting cutting performance.

[0018] Preferably, the DLC hard material layer contains or consists of amorphous carbon, especially tetrahedral amorphous carbon. The advantage of the TaCDLC coating is its outstanding hardness and therefore wear resistance. In addition, further hard material layers can be applied using PVD, PECVD, CVD processes or thermal spraying.

[0019] Preferably, at least one DLC hard material layer is deposited on the substrate with a thickness in the range of 2-4 μm, preferably 2.5-3.5 μm, which ensures good wear resistance.

[0020] The metallic substrate material is preferably selected from the group consisting of steel, ceramic, carbide, and combinations thereof, especially stainless steel. Stainless steel with a minimum of 10.5% chromium and a maximum of 1.2% carbon is the preferred substrate, preferably greater than 12% chromium and less than 0.8% carbon, and particularly preferably greater than 14% chromium and 0.4-0.6% carbon. Stainless steels with the following steel keying are particularly preferred: 1.4116, 1.4125, 1.4031, 1.4028, 1.4021, 1.4034, 1.4122, or 1.4006. Other suitable steel keyings can be found at www.edelstahl-rostfrei.de / fileadmin / user_upload / ISER / images / publikationen / Dok_Martensite_final.pdf / publikationen / Dok_Martensite_final.pdf.

[0021] To facilitate coating application, the DLC layer or another suitable layer can be applied to both sides of the cutting blade or to the cutting edge itself.

[0022] Preferably, an adhesion layer is deposited between the substrate and the DLC hard material layer. The adhesion promoting layer preferably contains or consists of chromium, titanium, or mixtures or alloys thereof.

[0023] Applying the coating or carrying out the complete coating process should preferably occur at temperatures below 250°C, preferably below 220°C, particularly preferably below 200°C in the case of stainless steel substrates.

[0024] The present invention also provides a cutting blade comprising a metal substrate having a first cutting surface and a second cutting surface, each including a cutting edge, wherein a DLC hard material layer is coated on the substrate as a coating layer, the DLC hard material layer having a thickness of 1 to 5 μm, a hardness of at least 30 GPa, and a roughness of at most 0.15 μm Ra.

[0025] Preferably, the DLC hard material layer contains or consists of amorphous carbon, in particular tetrahedral amorphous carbon.

[0026] The at least one DLC hard material layer preferably has a hardness of at least 35 GPa, preferably at least 40 GPa.

[0027] The at least one DLC hard material layer preferably has a thickness in the range of 2 to 4 μm, preferably 2.5 to 3.5 μm, which ensures good wear resistance.

[0028] It is also extremely important that the layer adheres well to the substrate and cutting edge. The adhesion of the layer should be between adhesion classes HF1 and HF3, preferably between adhesion classes HF1 and HF2, and particularly preferably adhesion class HF1. ​​An adhesion promoter layer can also be used to optimize the adhesion of the DLC layer to the substrate.

[0029] Preferably, the angle between the first and second cutting planes is in the range of 15° to 40°, preferably in the range of 20° to 35°, particularly preferably in the range of 25° to 32°, which means that less force is needed to separate the cut material.

[0030] To achieve sufficient initial sharpness, the cutting edge must be rounded to 6 μm or less, preferably 1.5 to 5 μm, and most preferably 2 to 4 μm. This limitation has the advantage of providing sufficient initial sharpness for use.

[0031] Preferably, an adhesion layer is deposited between the substrate and the DLC hard material layer. The adhesion promoting layer preferably contains or consists of chromium, titanium, or mixtures or alloys thereof.

[0032] The following figures and examples are not intended to limit the invention to the specific embodiments shown herein, but are intended to more fully illustrate the subject matter of the invention. [Brief explanation of the drawings]

[0033] In the drawings: [Figure 1] FIG. 1 shows a cross-sectional view of a first cutting blade according to the present invention. [Figure 2] FIG. 2 shows a cross-sectional view of another cutting blade according to the present invention having an adhesion promoter layer. DETAILED DESCRIPTION OF THE INVENTION

[0034] A cutting blade 1 according to the invention is shown in Figure 1. The cutting blade 1 is made of a substrate 2, of which a first cutting surface 3, a second cutting surface 4 and a cutting edge 5 have a coating made of a DLC hard material layer 6.

[0035] A cutting blade 1 according to the present invention is shown in Figure 2. The cutting blade 1 is made of a substrate 2, which is provided with an adhesion promoting layer 7 on its first cutting surface 3, second cutting surface 4 and cutting edge 5, and on which a coating of a DLC hard material layer 6 is deposited. example First, the blade body is made from the selected material. This can be done by cutting the steel (by laser, punching, etc.) to create a strip knife, or by forging the blade from a solid piece of steel, depending on the manufacturing tolerances. Martensitic corrosion-resistant steels such as 1.4116 and X50CrMoV15 are preferred blade materials, as they offer a good combination of hardness and corrosion resistance. In principle, other steel alloys are also suitable.

[0036] The next step in the process is conditioning the blade, in which the blade is hardened and then tempered one or more times. The purpose of this two-stage process is to increase wear resistance and then optimize toughness. This process is widespread in the industry. A normalizing heat treatment may be performed beforehand in certain circumstances to achieve a uniform, fine grain size.

[0037] The hardened blade body is then typically ground or polished in a process involving several steps to achieve the final contour in terms of dimensional accuracy, create a pleasing appearance, and improve corrosion resistance.

[0038] One of the final steps is sharpening or grinding 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°. Rounding the cutting edge is also important for initial sharpness. This should have a radius of less than 6 μm, preferably less than 5 μm, and particularly preferably less than 4 μm.

[0039] The DLC layer is then applied. Typically, a pre-cleaning (wet chemical, ultrasonic, etc.) is required in the same PVD system, along with a plasma micro-cleaning, to activate the surface before the actual DLC layer is applied to the system. A tetrahedral amorphous layer, with its outstanding abrasion resistance, is the preferred choice here. The hardness of this layer should be at least 30 GPa. To improve adhesion, an adhesion-promoting layer consisting of or containing chromium or titanium may be required.

[0040] The layer thickness should be 1 to 5 μm, preferably 2 to 4 μm, and particularly preferably 2.5 to 3.5 μm. It is also crucial that the layer adheres well to the substrate and the cutting edge. The layer adhesion, tested according to DIN 4856, should be between adhesion classes HF1 and HF3, preferably between adhesion classes HF1 and HF2, and particularly preferably adhesion class HF1.

Claims

1. A method for manufacturing a cutting blade (1) by applying a DLC hard material layer (6) as a coating layer to a substrate (2) having a cutting edge (5), a first cutting surface (3), and a second cutting surface (4) by physical vapor deposition (PVD), comprising: A method for manufacturing the DLC hard material layer (6), which has a layer thickness of 1-5 μm, a hardness of at least 30 GPa and a roughness of at most 0.15 μm Ra.

2. 2. A method according to claim 1, characterized in that at least one of the DLC hard material layers (6) comprises or consists of amorphous carbon, in particular tetrahedral amorphous carbon.

3. 3. A method according to claim 1 or 2, characterized in that the at least one DLC hard material layer (6) having a thickness in the range of 2 to 4 μm, preferably 2.5 to 3.5 μm, is applied to the substrate (2).

4. 4. The method according to claim 1, wherein the material of the metal substrate is selected from the group consisting of steel, ceramic, carbide and combinations thereof, in particular stainless steel, preferably stainless steel with a steel key of 1.4116, 1.4125, 1.4031, 1.4028, 1.4021, 1.4034, 1.4122 or 1.4006.

5. 5. The method according to any one of claims 1 to 4, characterized in that an adhesion promoting layer (7) is applied between the substrate (2) and the DLC hard material layer (6), said adhesion promoting layer preferably containing or consisting of chromium and / or titanium.

6. The cutting blade (1) comprises a metal substrate (2) having a first cutting surface (3) and a second cutting surface (4) including a cutting edge (5), and at least one DLC hard material layer (6) is applied to the substrate (2) as a coating layer having a layer thickness of 1 to 5 μm, a hardness of at least 30 GPa, and a roughness of at most 0.15 μm Ra.

7. 7. Cutting blade according to claim 6, characterized in that the at least one DLC hard material layer (6) comprises or consists of amorphous carbon, in particular tetrahedral amorphous carbon.

8. 8. Cutting blade according to claim 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.

9. Cutting blade according to any 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 μm, preferably 2.5 to 3.5 μm.

10. 10. Cutting blade according to any one of claims 6 to 9, characterized in that the material of the metal substrate is selected from the group consisting of steel, ceramic, carbide and combinations thereof, in particular stainless steel, preferably stainless steel with a steel key of 1.4116.

11. 11. Cutting blade according to any 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 of 15° to 40°, preferably 20° to 35°, particularly preferably 25° to 32°.

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

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

14. A cutting blade according to any one of claims 6 to 13, which can be produced by a method according to any one of claims 1 to 4.

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