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 comprises a metal substrate having a first cutting surface and a second cutting surface, which include a cutting edge, wherein at least one DLC hard-material layer is deposited on the substrate and at least one top layer applied in a wet process is deposited on the DLC hard-material layer on the side facing away from the substrate, and wherein the one top layer comprises, directly on the cutting edge, no top layer or a top layer having a layer thickness which is reduced in comparison with the rest of the top layer. The present invention also relates to a method for producing cutting blades of this type.

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 which enclose a cutting edge, wherein at least one DLC hard material layer is deposited on the substrate and at least one cover layer applied using a wet process is deposited on the DLC hard material layer on the side facing away from the substrate, and wherein one cover layer directly at the cutting edge has no cover layer or has a cover layer with a layer thickness that is reduced compared to the remaining cover layer. Furthermore, the present invention relates to a method for producing such cutting blades. According to the prior art, there are numerous inventions whose aim is to optimize the cutting performance of knives, cutting edges, scissors or similar tools through coatings.However, all of the following listed property rights are not applicable or only applicable to a limited extent to household cutting blades made of conventional stainless steels in accordance with DIN EN 10020 (July 2000).

[0003] For example, EP2495081B1 describes a cutting tool with a coating of fine-crystalline diamond. This coating 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.

[0006] EP 3 683 332 A1 also describes a coating of hybridized carbon on a carrier substrate, but unlike DE102019200681A1, 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.

[0007] 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.

[0008] EP 2 714 964B1 describes a woodworking tool with a defined layer thickness and rounded cutting edges. However, if the sliding layer mentioned in claim 1 were omitted, which is essential for a cost-effective solution, this would result in different layer thicknesses and edge rounding. This avoids 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 patent describes a base body made of hard metal, HSS, ceramic, or cermet, which is not a suitable material for household knives.

[0009] Another problem associated with the coating of consumer goods is increasing roughness due to the DLC layer application. This effect is amplified with increasing layer thickness. The cause is layer growth defects, so-called droplets. One solution would be to use a different coating process, such as HiPIMS or high-energy pulse magnetron sputtering, as described in DE 10 2008 021 912 C5 or EP 2 017 366 B1. However, this would be very costly and would only mitigate the problem.

[0010] In general, carbon coatings tend to be difficult to clean when soiled. This problem is further exacerbated by increased roughness, to the point where adequate cleaning with standard household cleaning agents is no longer possible.

[0011] DE 10 2015 101 782 B4 describes a sliding layer applied to a DLC coating. This describes a DLC or PLC coating that does not reduce roughness or eliminate 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.

[0012] 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.

[0013] Based on this, the object of the present invention was to eliminate the disadvantages of 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. Furthermore, the cutting blade should be easy to clean using standard household products. Furthermore, the cutting blades should be manufactured using cost-effective processes.

[0014] 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 9. The further dependent claims describe preferred embodiments.

[0015] According to the invention, a method for producing a cutting blade is provided, in which a) a DLC layer is deposited on a substrate having a first cutting surface and a second cutting surface enclosing a cutting edge by means of physical vapor deposition (PVD).

[0016] Hard material layer is deposited, b) a coating solution is applied to the DLC hard material layer by means of dipping and / or spraying, wherein the coating solution has a surface tension of 18 to 40 mJ / m 2 and c) the coating solution is dried to form the covering layer, the coating solution withdrawing from the cutting edge due to its surface tension, so that there is no covering layer directly at the cutting edge or there is a covering layer with a reduced layer thickness compared to the remaining covering layer.

[0017] It is preferred that the at least one DLC hard material layer contains or consists of amorphous carbon, in particular tetrahedrally amorphous carbon. The advantage of a layer made of tetrahedrally amorphous carbon is its outstanding hardness and thus its wear resistance. However, other hard material layers are also conceivable, which can be applied using PVD, PECVD, CVD processes, or thermal spraying.

[0018] In contrast to solutions known from the prior art, the cutting blade according to the present invention has the advantage of ensuring both good initial sharpness and long-lasting cutting edge retention.

[0019] A preferred embodiment provides that at least one DLC hard material layer with a thickness in the range of 1 to 5 pm, particularly preferably 2 to 4 pm and further preferably 2.5 to 3.5 pm is deposited on the substrate.

[0020] A further preferred embodiment provides that in step c) a covering layer is formed directly on the cutting edge with a layer thickness that is reduced by a factor of 3, preferably by a factor of 5, particularly preferably by a factor of 10 compared to the remaining covering layer. It is preferred that the at least one covering layer is deposited on the DLC hard material layer with a thickness in the range of 0.2 to 3 μm, preferably from 0.5 to 2.5 μm and particularly preferably from 1 to 2 μm. In this case, it must be ensured that the layer thicknesses remain within a defined process window. A certain layer thickness is necessary to level out the micro-roughness. Furthermore, a certain layer thickness should not be exceeded for cost and layer adhesion reasons.

[0021] Furthermore, it is preferred that the coating solution has a surface tension in the range of 20 to 30 mJ / m 2 , particularly preferably from 22 to 26mJ / m 2 has.

[0022] The application of the coating or the complete coating process should preferably take place below 250°C, preferably below 220°C, particularly preferably below 200°C.

[0023] The coating solution preferably contains or consists of a polysilazane. This eliminates the need for a costly vacuum process. After appropriate pre-cleaning with solvents, it can be applied by spraying or dipping. This eliminates the need for a costly vacuum process. Furthermore, the polysilazane layer is stable in the pH range of 3 to 12.

[0024] In addition to polysilazane layers, glass or glass-like layers or hybrid layers, layers based on ceramics or other anti-fingerprint coatings as well as polymer resin or fluoropolymer layers can also be used.

[0025] 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 key 1.4116, 1.4125, 1.4031, 1.4028, 1.4021, 1.4034, 1.4122, or 1.4006 is particularly preferred. Other suitable steel keys are www.edelstahl-rostfrei.de / fileadmin / user upload / ISER / images Martensite final.pdf.

[0026] According to the invention, a cutting blade is also provided which contains a metallic substrate with a first cutting surface and a second cutting surface which enclose a cutting edge, wherein at least one DLC hard material layer is deposited on the substrate and at least one cover layer applied by a wet process is deposited on the DLC hard material layer on the side facing away from the substrate, and wherein the one cover layer directly on the cutting edge has no cover layer or has a cover layer with a reduced layer thickness compared to the remaining cover layer.

[0027] It is preferred that the at least one DLC hard material layer contains or consists of amorphous carbon, in particular tetrahedral amorphous carbon. A tetrahedral amorphous carbon layer is particularly suitable due to its outstanding hardness and thus its wear resistance.

[0028] A preferred embodiment provides that the at least one DLC hard material layer preferably has a hardness of at least 30 GPa, particularly preferably at least 34 GPa and very particularly preferably from 38 GPa to 45 GPA.

[0029] Preferably, the at least one DLC hard material layer has a thickness in the range from 1 to 5 pm, preferably from 2 to 4 pm and particularly preferably from 2.5 to 3.5 pm.

[0030] The top layer preferably contains or consists of polysilazane, as polysilazane is stable in the pH range of 3 to 12. The polysilazane top layer exhibits good chemical and mechanical resistance. This is supported by the covalent bond to the substrate or the underlying DLC ​​layer.

[0031] The top layer should exhibit good adhesion to the substrate or the underlying DLC ​​layer. The top layer preferably has cross-cut values ​​of 0 to 2, particularly preferably 0 to 1, and particularly preferably 0, as determined according to DIN EN ISO 2409.

[0032] In addition to polysilazane layers, glass or glass-like layers or hybrid layers, layers based on ceramics or other anti-fingerprint coatings as well as polymer resin or fluoropolymer layers can also be used.

[0033] It is preferred that directly at the cutting edge the covering layer has a layer thickness reduced by a factor of 3, preferably by a factor of 5, particularly preferably by a factor of 10, compared to the remaining covering layer.

[0034] Furthermore, it is preferred that the cover layer has a thickness in the range of 0.2 to 3 pm, preferably of 0.5 to 2.5 pm and particularly preferably of 1 to 2 pm.

[0035] The cover layer preferably has a surface roughness Ra of 0.05 to 0.22 pm, particularly preferably of 0.08 to 0.20 pm.

[0036] The cover layer preferably has a surface tension of 10 to 30 mJ / m 2 , particularly preferably from 15 to 25 mJ / m 2 This ensures easy cleaning when soiled.

[0037] It is preferred that the material of the metallic substrate be 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 is particularly preferred.

[0038] It is preferred that the angle between the first cutting surface and the second cutting surface is in the range of 15° to 40°, preferably from 20° to 35°, and particularly preferably from 25° to 32°. To achieve good initial sharpness, the rounding radius of the cutting edge is preferably in the range of 1 to 6 pm, particularly preferably in the range of 1.5 to 5 pm, and most preferably in the range of 2 to 4 pm.

[0039] 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.

[0040] It shows

[0041] Fig.l a sectional view of the cutting blade according to the invention

[0042] Fig.2 a first microscopic image of the cutting edge of the cutting blade according to the invention

[0043] Fig. 3 is a further microscopic image of the cutting edge of the cutting blade according to the invention from Fig. 2 in higher resolution

[0044] Fig. 4 shows a further microscopic image of the cutting blade according to the invention with regard to the structure of the coating

[0045] Fig. 5 is a diagram showing the cutting performance of the cutting blade according to the invention compared to an uncoated cutting blade of the prior art

[0046] 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 and the second cutting surface 4 have a coating of a DLC hard material layer 6. The DLC hard material layer is in turn provided with a cover layer 7 made of polysilazane. From the illustration in Fig. 1, it can be seen that at the cutting edge 5, the cover layer 7 has a layer thickness that decreases toward the cutting edge 5, which is due to the edge alignment.

[0047] Fig. 2 shows a microscopic image of the cutting blade 1 according to the invention in the region of the cutting edge 5. The cutting edge 5 is surrounded by the first cutting surface 3 (top) and the second cutting surface 4 (bottom).

[0048] Fig. 3 shows, analogously to Fig. 2, a cutting blade 1 according to the invention in the region of the cutting edge 5, but in higher resolution.

[0049] Fig. 4 shows a microscopic image of a cutting blade 1 according to the invention in a sectional view, which illustrates the structure of the coating. The substrate 2 is coated here with a DLC hard material layer 6. The DLC hard material layer has a layer thickness of 2.58 pm. The DLC hard material layer 6 is coated with a cover layer made of polysilazane 7, whereby an interface 8 between the two coatings can be seen. The cover layer has a layer thickness of 1.51 pm. In Fig. 4 it can be seen that in regions 9, 10 in which the DLC hard material layer 6 has a higher or lower layer thickness due to an inhomogeneous coating, the cover layer 7 can compensate for these deviations and has a smoothing effect, so that the surface of the cover layer 7 has a very low surface roughness, whereby the surface is very easy to clean.

[0050] Fig. 5 shows a diagram illustrating the cutting performance of a cutting blade according to the invention compared to an uncoated steel knife. This shows that with an uncoated steel knife according to the prior art, the cutting depth decreases rapidly after just a few cutting cycles, whereas the cutting depth of the cutting blade according to the invention remains virtually constant even after 60 cutting cycles.

[0051] Example

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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, preferably at least 34 GPa, and particularly preferably at least 38 GPa. To improve adhesion, an adhesion promoter layer consisting of or containing chromium or titanium may be required.

[0057] 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.

[0058] The final coating step is the application of the top layer, which is preferably a polysilazane layer. In addition to polysilazane layers, glass or glass-like layers, hybrid layers, ceramic-based layers, or other anti-fingerprint coatings, as well as polymer resin or fluoropolymer layers, can also be used. This layer application reduces roughness and also allows the knife to be cleaned with standard household cleaning products.

[0059] The blade is usually cleaned before the coating is applied. The polysilazane layer can be applied by dipping or spraying and is then dried or baked in an oven. The dried coating has a surface tension in the range of 20 to 30 mJ / m 2 , particularly preferably from 22 to 26mJ / m 2 This significantly improves cleanability. The layer thickness is in the range of 0.2 to 3 μm, preferably 0.5 to 2.5 μm, and particularly preferably 1 to 2 μm. The cover layer should exhibit good adhesion to the substrate or the underlying DLC ​​layer. The cover layer preferably has cross-cut values ​​of 0 to 2, particularly preferably 0 to 1, and particularly preferably 0, determined according to DIN EN ISO 2409.

[0060] During drying, the effect of edge alignment also results in the dry top layer having a reduced layer thickness compared to the remaining top layer. The reduction in layer thickness from the side surface to the cutting edge is on the order of a factor of 3, preferably a factor of 5, and particularly preferably a factor of 10. This minimizes rounding of the cutting edge and thus avoids a measurable reduction in sharpness.

[0061] If not already done in a previous step, the handle is attached.

Claims

A method for producing a cutting blade (1), in which a) a DLC hard material layer (6) is deposited 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), b) a coating solution is applied to the DLC hard material layer (6) by means of dipping and / or spraying processes, wherein the coating solution has a surface tension of 18 to 40 mJ / m 2and c) the coating solution is dried to form the cover layer (7), wherein the coating solution withdraws from the cutting edge (5) due to its surface tension, so that directly at the cutting edge (5) there is no cover layer (7) or there is a cover layer (7) with a reduced layer thickness compared to the remaining cover layer (7). 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 tetrahedrally amorphous carbon. Method according to one of claims 1 or 2, characterized in that the at least one DLC hard material layer (6) is applied to the substrate with a thickness in the range of 1 to 5 pm, preferably 2 to 4 pm and particularly preferably 2.5 to 3.5 pm (2) is deposited. Method according to one of claims 1 to 3, characterized in that in step c) a cover layer (7) is formed directly on the cutting edge (5) with a layer thickness reduced by a factor of 3, preferably by a factor of 5, particularly preferably by a factor of 10 compared to the remaining cover layer (7). Method according to one of claims 1 to 4, characterized in that the at least one cover layer (7) is deposited on the DLC hard material layer (6) with a thickness in the range of 0.2 to 3 μm, preferably from 0.5 to 2.5 μm and particularly preferably from 1 to 2 μm. Method according to one of claims 1 to 5, characterized in that the coating solution has a surface tension in the range of 20 to 30 mJ / m 2 , particularly preferably from 22 to 26mJ / m 2The method according to any one of claims 1 to 6, characterized in that the coating solution contains a polysilazane. The method according to any one of claims 1 to 7, 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.

9. 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) and at least one cover layer (7) applied by a wet process is deposited on the DLC hard material layer (6) on the side facing away from the substrate (2), and wherein one cover layer (7) directly on the cutting edge (5) has no cover layer (7) or has a cover layer (7) with a reduced layer thickness compared to the remaining cover layer (7).

10. Cutting blade according to claim 9, characterized in that the at least one DLC hard material layer (6) contains or consists of amorphous carbon, in particular tetrahedral amorphous carbon.

11. Cutting blade according to one of claims 9 or 10, characterized in that the at least one DLC hard material layer (6) has a hardness of at least 30 GPa, preferably at least 34 GPa, particularly preferably from 38 GPa to 45 GPA.

12. Cutting blade according to one of claims 9 to 11, characterized in that the at least one DLC hard material layer (6) has a thickness in the range from 1 to 5 pm, preferably from 2 to 4 pm and particularly preferably from 2.5 to 3.5 pm.

13. Cutting blade according to one of claims 9 to 12, characterized in that the cover layer contains polysilazane or consists of polysilazane.

14. Cutting blade according to one of claims 9 to 13, characterized in that directly on the cutting edge (5) the Cover layer (7) has a layer thickness reduced by a factor of 3, preferably by a factor of 5, particularly preferably by a factor of 10, compared to the remaining cover layer (7).

15. Cutting blade according to one of claims 9 to 14, characterized in that the cover layer (7) has a thickness in the range from 0.2 to 3 pm, preferably from 0.5 to 2.5 pm and particularly preferably from 1 to 2 pm.

16. Cutting blade according to one of claims 9 to 15, characterized in that the cover layer has a surface roughness Ra of 0.05 to 0.22 pm, preferably of 0.08 to 0.20 pm.

17. Cutting blade according to one of claims 9 to 16, 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.

18. Cutting blade according to one of claims 9 to 17, 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°.

19. Cutting blade according to one of claims 9 to 18, 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.

20. Cutting blade according to one of claims 9 to 19 and manufacturable by the method according to one of claims 1 to 8.

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