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 comprising a metal substrate having a first cutting surface and a second cutting surface with a cutting edge, at least one DLC hard material layer applied to the substrate, and at least one cover layer applied to the DLC hard material layer by wet processing on the side away from the substrate, the one cover layer being either not provided with a cover layer at the position of the cutting edge or having a cover layer with a reduced layer thickness compared to the rest of the cover layer. Furthermore, the present invention relates to a method for manufacturing such a cutting blade.

Description

[Technical Field]

[0001] The present invention relates to a cutting blade and a method for manufacturing the same, the cutting blade comprising a metal substrate having a first cutting surface and a second cutting surface with a cutting edge, on which at least one DLC hard material layer is applied, and on the side away from the substrate, on the DLC hard material layer, at least one cover layer is applied by wet processing, the one cover layer exactly at the position of the cutting edge having no cover layer or having a cover layer with a reduced layer thickness compared to the remaining cover layers. Furthermore, the present invention relates to a method for manufacturing such a cutting blade. [Background technology]

[0002] According to the prior art, there are numerous inventions directed to the use of coatings to optimize the cutting performance of knives, cutters, scissors or similar tools. However, the following intellectual property rights do not apply, or apply only to a limited extent, to household cutting tools made of conventional rust-free stainless steel according to DIN EN 10020 (July 2000).

[0003] For example, US Pat. No. 5,629,499 describes a cutting tool with a coating of microcrystalline diamond. This is applied by hot-wire CVD at typical substrate temperatures of 600 to 900°C. The substrate is made of a heat-resistant material such as titanium, nickel, niobium, tungsten, carbide, or ceramic. These temperatures are significantly higher than the hardening temperature of stainless steel. Changing the material to one of the aforementioned materials would also result in a significant increase in the cost of the household knife.

[0004] Patent Document 2 describes a razor blade with a DLC layer, a cutting edge radius of less than 1200 angstroms (corresponding to 0.12 μm), and a layer thickness of at least 400 to 2000 angstroms (corresponding to 0.04 μm to 0.2 μm). However, such a small cutting edge radius and thin layer thickness are not sufficient to significantly improve the edge retention properties of a household knife. This is a result of the more severe usage conditions and methods in which a household knife is handled compared to a razor blade.

[0005] Patent Document 3 describes a multilayer cutting tool in which an intermediate layer is composed of hybrid carbon, which forms the cutting edge. Because the thickness of such layers is in the micrometer range, it is not possible to manufacture them cost-effectively from a manufacturing technology perspective. This requires the cutting edge to be ground with micrometer precision, which is very time-consuming. When using thermal spraying to apply thicker layers, there is the drawback of reduced corrosion resistance of typical stainless steel blade materials. Furthermore, it is not economically feasible to manufacture such multilayer structures for consumer goods, and especially for knives with complex shapes.

[0006] US Patent No. 5,629,999 also describes a coating of hybrid carbon on a carrier substrate, which, in contrast to US Patent No. 5,629,999, has a three-dimensional structure. This structuring can be achieved by masking, which is very time-consuming. Subsequent laser treatment has the disadvantage that the thermal energy input would result in a decrease in the corrosion resistance of the stainless steel substrate.

[0007] Patent document 5 describes a cutting tool with a metal carrier layer and a second layer of diamond-like carbon. In this case, only the maximum edge radius is specified, not the layer thickness. Both parameters are essential for good initial sharpness and for maintaining cutting performance over the longest possible service life.

[0008] Patent document 6 specifies a woodworking tool with a defined layer thickness and cutting edge radius. However, omitting the sliding layer mentioned in claim 1, which is essential for a cost-effective solution, would result in a different layer thickness and cutting edge radius. The aim is to avoid costly multi-layer systems consisting of a sliding layer and a functional layer, which are coated in a two-stage process. Furthermore, the patent describes substrates made of carbide, HSS, ceramic, or cermet, materials that are not suitable for household knives.

[0009] The increased roughness caused by the application of DLC layers is another problem associated with the coating of consumer goods. This effect intensifies as the layer thickness increases. It is caused by defects in the layer growth, so-called droplets. One solution would be to use alternative coating methods, such as HiPIMS or high-power impulse magnetron sputtering, as described in US Pat. No. 5,627,497 or US Pat. No. 5,627,497. However, this would be costly and would only alleviate the problem.

[0010] In general, carbon layers tend to be difficult to clean after they have become soiled, a problem exacerbated by their increased roughness to the point that they are no longer able to be properly cleaned with standard household items.

[0011] Patent Document 9 describes a slip layer applied to a DLC layer. In this case, it is stated that the DLC or PLC layer does not reduce the roughness and does not eliminate the increased roughness of the DLC-based layer. Furthermore, the affinity of food to carbon-based coatings makes them difficult to clean. Furthermore, a separate PVD or CVD process would incur high costs and likely result in increased rounding of the cutting edge and therefore reduced sharpness.

[0012] Patent document 10 also describes a multilayer structure consisting of a hard tetrahedral carbon intermediate layer and a soft amorphous carbon cover layer. In terms of applying the layers and the coating material itself, the drawbacks correspond to the above patent specification. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] European Patent No. 2495081 [Patent Document 2] U.S. Patent No. 6,289,593 [Patent Document 3] German Patent Application Publication No. 102019200681 [Patent Document 4] European Patent Application Publication No. 3683332 [Patent Document 5] German Patent Invention No. 102004052068 [Patent Document 6] European Patent No. 2714964 [Patent Document 7] German Patent Invention No. 102008021912 [Patent Document 8] European Patent No. 2017366 [Patent Document 9] German Patent Invention No. 102015101782 [Patent Document 10] European Patent No. 1915472 Summary of the Invention [Problem to be solved by the invention]

[0014] Based on this, the object of the present invention is to provide a cutting blade that eliminates the drawbacks present in the prior art and that is sharp upon delivery and maintains its sharpness and cutting performance for as long as possible, even under increasing load. Furthermore, the cutting blade should be easy to clean with standard household products. Furthermore, the cutting blade should be manufactured using a cost-effective method. [Means for solving the problem]

[0015] 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 9. The further dependent claims describe preferred embodiments.

[0016] According to the present invention, there is provided a method of manufacturing a cutting blade, the method comprising: a) applying a DLC hard material layer by physical vapor deposition (PVD) onto a substrate having a first cutting surface and a second cutting surface, the substrate comprising a cutting edge; b) A dipping and / or spraying process is used to apply the coating solution to the DLC hard material layer, and the coating solution has a concentration of 18-40 mJ / m 2 and has a surface tension of c) The coating solution is dried to form a cover layer, which is retracted from the cutting edge by surface tension, leaving either no cover layer at the cutting edge or a cover layer with a thickness that is smaller than that of the rest of the cover layer.

[0017] Preferably, at least one DLC hard material layer comprises or consists of amorphous carbon, in particular tetrahedral amorphous carbon. The advantage of a tetrahedral amorphous carbon layer is its excellent hardness and therefore its wear resistance. Furthermore, other hard material layers are also possible, which can be applied by PVD, PECVD, CVD or thermal spraying methods.

[0018] In contrast to the solutions known from the prior art, the cutting blade according to the invention benefits from being able to ensure both good initial sharpness and long-lasting edge retention properties.

[0019] One preferred embodiment comprises that at least one DLC hard material layer having a thickness of 1-5 μm, particularly preferred 2-4 μm, even more preferred 2.5-3.5 μm is applied to the substrate.

[0020] Another preferred embodiment provides that in step c) a cover layer is formed directly on the cutting edge, having a layer thickness that is 3 times, preferably 5 times, particularly preferably 10 times thinner than the remaining cover layer.

[0021] At least one cover layer, having a thickness in the range of 0.2-3 μm, preferably 0.5-2.5 μm, particularly preferably 1-2 μm, is applied to the DLC hard material layer. When doing so, it must be ensured that the layer thickness remains within specified control limits. A certain layer thickness is required to smooth out micro-roughness. Furthermore, for reasons of cost and layer adhesion, a certain layer thickness should not be exceeded.

[0022] The coating solution preferably has a concentration of 20-30 mJ / m 2 , particularly preferably 22-26 mJ / m 2 The surface tension ranges from 0.01 to 0.1.

[0023] Applying the coating or carrying out the complete coating process should preferably occur below 250°C, preferably below 220°C, particularly preferably below 200°C.

[0024] Preferably, the coating solution contains or consists of polysilazane. No costly vacuum process is required. After appropriate pre-cleaning, it can be applied by spraying or immersing in a solvent. No costly vacuum process is required. Furthermore, the polysilazane layer remains stable in the pH range of 3-12.

[0025] In addition to polysilazane layers, glass or glass-like or hybrid layers, ceramic-based layers or other anti-fingerprint coatings, as well as polymer resin or fluoropolymer layers may also be used.

[0026] Preferably, the metal substrate material is selected from the group consisting of steel, ceramic, carbide, and combinations thereof, particularly stainless steel. Stainless steel is the preferred substrate, containing a minimum of 10.5% chromium and a maximum of 1.2% carbon, preferably more than 12% chromium and less than 0.8% carbon, and particularly preferably more than 14% chromium and 0.4-0.6% carbon. Particular preference is given to stainless steels with the steel key 1.4116, 1.4125, 1.4031, 1.4028, 1.4021, 1.4034, 1.4122, or 1.4006. Other suitable steel keys can be found at www.edelstahl-rostfrei.de / fileadmin / user_upload / ISER / images / publikationen / Dok_Martensite_final.pdf.

[0027] The cutting blade comprises a metal substrate having a first cutting surface and a second cutting surface comprising the cutting edge, on which at least one DLC hard material layer is applied, and at least one cover layer applied by wet processing is deposited on the DLC hard material layer on the side remote from the substrate, and exactly at the position of the cutting edge, one coating layer does not have a cover layer or has a cover layer with a layer thickness reduced compared to the rest of the cover layer.

[0028] Preferably, at least one DLC hard material layer comprises or consists of amorphous carbon, in particular tetrahedral amorphous carbon. Due to its excellent hardness and therefore its wear resistance, tetrahedral amorphous carbon layers are particularly suitable.

[0029] A preferred embodiment provides that the at least one DLC hard material layer preferably has a hardness of at least 30 GPa, with at least 34 GPa being particularly preferred and 38 GPa-45 GPa being very particularly preferred.

[0030] Preferably, the at least one DLC hard material layer has a thickness in the range of 1-5 μm, preferably 2-4 μm, particularly preferably 2.5-3.5 μm.

[0031] The cover layer preferably comprises or consists of polysilazanes, since polysilazanes are stable in the pH range of 3-12. Polysilazane cover layers are highly resistant to chemicals and mechanical abrasion. Covalent bonding to the substrate or underlying DLC ​​layer helps achieve this.

[0032] The cover layer should adhere well to the substrate and the underlying DLC ​​layer. The cover layer preferably has a crosscut value, determined in accordance with DIN EN ISO 2409, of 0-2, particularly preferably 0-1, and particularly preferably 0.

[0033] In addition to polysilazane layers, glass or glass-like or hybrid layers, ceramic-based layers or other anti-fingerprint coatings, as well as polymer resin or fluoropolymer layers may also be used.

[0034] It is preferred to reduce the coating thickness of the cover layer exactly at the cutting edge by a factor of 3, preferably 5, particularly preferably 10, compared to the remainder of the cover layer.

[0035] Furthermore, the cover layer preferably has a thickness in the range of 0.2-3 μm, preferably 0.5-2.5 μm, particularly preferably 1-2 μm.

[0036] Preferably, the cover layer has a surface roughness Ra of 0.05-0.22 μm, particularly preferably 0.08-0.20 μm.

[0037] Preferably, the cover layer has a thermal conductivity of 10-30 mJ / m 2 , particularly preferably 15-25 mJ / m 2 This ensures that the cover layer can be easily cleaned if it becomes soiled.

[0038] Preferably, the metallic substrate material is selected from the group consisting of steel, ceramic, carbide, and combinations thereof, in particular stainless steel. Stainless steel with a minimum of 10.5% chromium and a maximum of 1.2% carbon, preferably more than 12% chromium and less than 0.8% carbon, and particularly preferably more than 14% chromium and 0.4-0.6% carbon, is the preferred substrate. Particular preference is given to stainless steel with the steel key 1.4116.

[0039] Preferably, the angle between the first and second cutting planes is in the range of 15°-40°, preferably 20°-35°, particularly preferably 25°-32°.

[0040] To achieve good initial sharpness, the radius of the cutting edge is preferably in the range of 1-6 μm, particularly preferably 1.5-5 μm, most preferably 2-4 μm.

[0041] The following figures and examples are intended to explain the subject matter of the present invention in more detail without intending to limit it to the specific embodiments shown therein. [Brief explanation of the drawings]

[0042] [Figure 1] 1 is a cross-sectional view of a cutting blade according to the present invention. [Figure 2] 1 is a first microscope image of the cutting edge of a cutting blade according to the present invention. [Figure 3] 3 is another microscopic image at high resolution of the cutting edge of the cutting blade according to the present invention shown in FIG. 2; [Figure 4] 10 is another microscope image of a cutting blade according to the present invention in terms of coating structure. [Figure 5] 1 is a chart showing the cutting performance of a cutting blade according to the present invention compared to an uncoated cutting blade of the prior art. DETAILED DESCRIPTION OF THE INVENTION

[0043] A cutting blade 1 according to the invention is shown in Figure 1. The cutting blade 1 consists of a substrate 2, the first cutting surface 3 and the second cutting surface 4 of which are coated with a DLC hard material layer 6. The DLC hard material layer in turn is provided with a cover layer 7 made of polysilazane. The diagram in Figure 1 shows that at the cutting edge 5, the thickness of the cover layer 7 decreases towards the cutting edge 5, which is due to the disappearance of the cutting edge.

[0044] Figure 2 shows a microscope image of a cutting blade 1 according to the invention in the region of the cutting edge 5. The cutting edge 5 is bounded by a first cutting surface 3 (upper part) and a second cutting surface 4 (lower part).

[0045] Like FIG. 2, FIG. 3 shows a cutting blade 1 according to the invention in the region of the cutting edge 5, but in higher resolution.

[0046] FIG. 4 shows a microscopic image of a cross section of a cutting blade 1 according to the invention, illustrating the coating structure. Here, a substrate 2 is coated with a DLC hard material layer 6. The DLC hard material layer has a thickness of 2.58 μm. The DLC hard material layer 6 is coated with a polysilazane cover layer 7, and the interface 8 between the two coatings is visible. The cover layer has a thickness of 1.51 μm. FIG. 4 shows that in regions 9 and 10, the DLC hard material layer 6 has a thicker or thinner layer due to uneven coating, and the cover layer 7 can correct these deviations, exhibiting a smoothing effect, resulting in a surface with very low surface roughness and making the surface very easy to clean.

[0047] The diagram in Figure 5 shows the cutting performance of a cutting blade according to the present invention compared to an uncoated metal blade. It can be readily seen that the depth of cut of the uncoated metal blade according to the prior art decreases rapidly after only a few cutting cycles, whereas the depth of cut of the cutting blade according to the present invention remains substantially constant even after 60 cutting cycles. Example First, the blade body is fabricated from the selected material. Depending on manufacturing tolerances, this can be done by cutting the steel (by laser, punching, etc.) to create a steel band knife, or by forging the blade from a solid piece of steel. Martensitic corrosion-resistant steels such as 1.4116 or X50CrMoV15 are preferred blade materials, offering an excellent combination of hardness and corrosion resistance. In principle, other steel alloys are also suitable.

[0048] The next step in the process is to harden the blade. In this process, the blade is hardened in a hardening process and then hardened one or more times. The purpose of this two-step process is to increase wear resistance and then optimize toughness. Such processes are widely used in industry. In certain circumstances, a normalizing heat treatment may be performed beforehand to achieve a uniform, fine grain size.

[0049] The hardened blade body is then polished or ground, typically in a process involving multiple steps, to achieve the final contour in terms of dimensional accuracy, create an attractive appearance, and improve corrosion resistance.

[0050] One of the last steps is to attach or sharpen the cutting edge. The cutting edge angle is usually in the range of 15°-40°, preferably 20°-35°, and particularly preferably 25°-32°. The rounding of the cutting edge is also important for the initial sharpness. This should be a rounding radius of less than 6 μm, preferably less than 5 μm, and particularly preferably less than 4 μm.

[0051] Next, the DLC layer is applied. Usually, in PVD systems, pre-cleaning (wet chemicals, ultrasound, etc.) and plasma micro-cleaning in PVD systems are required to activate the surface before the actual DLC layer is applied. A tetrahedral amorphous layer is preferred here, as it has excellent abrasion resistance. The hardness of this layer should be at least 30 GPa, preferably at least 34 GPa, and particularly preferably at least 38 GPa. To improve adhesion, an adhesion-promoting layer made of or containing chromium or titanium may be required.

[0052] The layer thickness should be in the range of 1-5 μm, preferably 2-4 μm, particularly preferably 2.5-3.5 μm. It is also very important that the layer adheres firmly to the substrate and the cutting edge. The layer adhesion, tested according to DIN 4856, should be between HF1 and HF3, preferably between HF1 and HF2, particularly preferably HF1.

[0053] The final coating step is the application of a cover layer, preferably a polysilazane layer. In addition to the polysilazane layer, glass or glass-like or hybrid layers, ceramic-based layers or other anti-fingerprint coatings, as well as polymer resin or fluoropolymer layers, can also be used. Applying layers ensures reduced roughness and also makes the blade easier to clean with standard household products.

[0054] The knife is usually cleaned before applying the layer. The polysilazane layer can be applied by dipping or spraying, and then dried or baked in an oven. The dried coating has a yield of 20-30 mJ / m 2 , preferably 22-26 mJ / m 2This significantly improves cleaning properties. The layer thickness should be applied in the range of 0.2-3 μm, preferably 0.5-2.5 μm, particularly preferably 1-2 μm. The cover layer should have better adhesion to the substrate and the underlying DLC ​​layer. The cover layer preferably has a crosscut value, determined in accordance with DIN EN ISO 2409, of 0-2, particularly preferably 0-1, and particularly preferably 0.

[0055] The effect of cutting edge disappearance during drying means that the thickness of the cover layer becomes thinner when dried compared to the rest of the cover layer. The reduction in layer thickness from the side to the cutting edge is three times, preferably five times, and particularly preferably ten times. This minimizes the rounding of the cutting edge and thus prevents any measurable loss of sharpness.

[0056] In the previous step, the handle is attached if not already done.

Claims

1. A method for manufacturing a cutting blade (1), comprising the steps of: a) a DLC hard material layer (6) is applied by physical vapor deposition (PVD) onto a substrate (2) having a first cutting surface (3) and a second cutting surface (4) with a cutting edge (5); b) a dipping method and / or a spraying method is used to apply a coating solution to the DLC hard material layer (6), the coating solution having a surface tension of 18-40 mJ / m2; c) the coating solution is dried to form a cover layer (7), which is retracted from the cutting edge (5) by its surface tension, so that exactly at the position of the cutting edge (5), the cover layer (7) is either absent or has a smaller layer thickness compared to the rest of the cover layer (7).

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

3. 2. The method according to claim 1, characterized in that the at least one DLC hard material layer (6) is applied onto the substrate (2) with a thickness in the range of 1-5 μm, preferably 2-4 μm, particularly preferably 2.5-3.5 μm.

4. 2. The method according to claim 1, characterized in that in step c) a cover layer (7) is formed exactly on the cutting edge (5) having a layer thickness that is 3 times, preferably 5 times, particularly preferably 10 times thinner than the remaining part of the cover layer (7).

5. 2. The method according to claim 1, characterized in that the at least one cover layer (7) having a thickness of 0.2-3 μm, preferably 0.5-2.5 μm, particularly preferably 1-2 μm, is applied onto the DLC hard material layer (6).

6. 2. The method of claim 1, wherein the coating solution has a concentration of 20-30 mJ / m 2 , particularly preferably 22-26 mJ / m 2 The method is characterized in that the surface tension is in the range of

7. 10. The method of claim 1, wherein the coating solution comprises a polysilazane.

8. 2. The method according to claim 1, 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, 1.4125, 1.4031, 1.4028, 1.4021, 1.4034, 1.4122 or 1.4006.

9. 1. A cutting blade (1), comprising a metal substrate (2) having a first cutting surface (3) and a second cutting surface (4) with a cutting edge (5), wherein at least one DLC hard material layer (6) is applied onto the substrate (2), and at least one cover layer (7) is applied onto the DLC hard material layer (6) on a side remote from the substrate (2) by wet processing, wherein exactly at the position of the cutting edge (5), the one cover layer (7) is either absent or has a cover layer (7) with a thickness smaller than that of the remaining part of the cover layer (7).

10. 10. The cutting blade of claim 9, 1. A cutting blade, characterized in that said at least one DLC hard material layer (6) comprises or consists of amorphous carbon, in particular tetrahedral amorphous carbon.

11. 11. Cutting blade according to claim 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, more preferably 38 GPa-45 GPa.

12. 10. The cutting blade of claim 9, A cutting blade characterized in that the at least one DLC hard material layer (6) preferably has a thickness in the range of 1-5 μm, preferably 2-4 μm, particularly preferably 2.5-3.5 μm.

13. 10. The cutting blade of claim 9, wherein the cover layer comprises or consists of polysilazane.

14. 10. A cutting blade according to claim 9, characterized in that exactly at the location of the cutting edge (5) the coating thickness of the cover layer (7) is three times, preferably five times, particularly preferably ten times, lower than in the remaining part of the cover layer (7).

15. 10. Cutting blade according to claim 9, characterized in that the thickness of the cover layer (7) is in the range of 0.2-3 μm, preferably 0.5-2.5 μm, particularly preferably 1-2 μm.

16. 10. Cutting blade according to claim 9, characterized in that the cover layer has a surface roughness Ra of 0.05-0.22 μm, preferably 0.08-0.20 μm.

17. 10. A cutting blade according to claim 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.

18. 10. A cutting blade according to claim 9, characterized in that the angle between the first cutting surface (3) and the second cutting surface (4) is in the range of 15°-40°, preferably 20°-35°, particularly preferably 25°-32°.

19. 10. Cutting blade according to claim 9, characterized in that the cutting edge (5) has a radius of rounding of 1-6 μm, preferably 1.5-5 μm, particularly preferably 2-4 μm.

20. 10. A cutting blade according to claim 9, which is producible by the method according to any one of claims 1 to 8.

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