Cutting tools

Abstract

In the present invention, a replaceable blade (1) is used to cut a material to be cut made of a non-ferrous metal or an alloy thereof, wood, a wood-based material, or a resin. A coating (14) that coats a substrate (10) is provided. The coating (14) has a columnar structure that is provided to a flank face (3) of a cutting edge (5) in which a rake face (4) and the flank face (3) intersect, and that is provided so as to rise upright from the substrate (10). The material constituting the coating (14) includes one or more substances from among chromium nitrides, oxynitrides, oxides, carbides, carbonates, carbonitrides and carbonitrides.

Description

[Technical Field]

[0001] One aspect of the present disclosure relates to a surface-coated cutting tool used for cutting, for example, non-ferrous metals and their alloys, wood, wood-based materials, or resins. [Background technology]

[0002] Cutting tools are, for example, woodworking cutters and router bits used to cut wood or wood-based composite materials. These cutting tools have blades made of steel, such as tool steel or bearing steel, or cemented carbide. The rake face or flank face of the blade may be coated with a hard, wear-resistant, and corrosion-resistant coating to improve sharpness and extend cutting life. The coating is made of chromium nitride, such as CrN, and is applied to the substrate by, for example, PVD processing.

[0003] Hard coatings made of chromium nitride can provide wear resistance that cannot be achieved with a base material such as tool steel. However, when cutting wood with a high moisture content, for example, chromium components are easily leached. This can erode the surface coating, resulting in a loss of the expected durability. To address this issue, cutting tools have been proposed that have a hard base coating made of chromium nitride and then coated with a main coating made of, for example, chromium oxide or chromium oxynitride.

[0004] Japanese Patent No. 5,576,788 describes a multilayer coating. The multilayer structure includes a hard base coating layer applied to the rake face or flank face and a hard main coating layer applied to the hard base coating layer. The hard base coating layer is made of a chromium nitride, such as CrN. The hard main coating layer is made of a material with higher corrosion resistance than the hard base coating layer, such as chromium oxide (Cr2O3) or chromium oxynitride (CrNO). Japanese Patent No. 6,002,784 describes a coating in which the oxygen concentration of the hard main coating layer varies along its thickness. This coating improves the toughness and heat resistance of the hard main coating layer.

[0005] When a cutting tool cuts a workpiece, the cutting edge faces the following problems. For example, the coating wears. Impacts, vibrations, and other factors can cause chipping, which is when the coating breaks into small pieces. The coating near the cutting edge on the rake face or flank face tapers, causing film cracks. When the cutting edge is damaged by wear, chipping, film cracks, and other factors, it becomes impossible to maintain a sharp cutting edge. Chipping and film cracking progress, for example, from the substrate toward the surface layer of the coating covering the flank face or rake face. Chipping can progress to an area close to the cutting edge. Alternatively, film cracking can occur across the rake face or flank face. In such cases, the cutting edge is damaged, making it impossible to fully utilize the wear resistance and corrosion resistance of the coating. Conventionally known coating structures left room for various improvements in order to adequately suppress damage to the cutting edge. Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, there has been a demand for a cutting tool with a structure that can maintain the sharpness of the cutting edge for a long period of time, for example, by suppressing damage to the coating in the area close to the cutting edge. [Means for solving the problem]

[0007] According to one aspect of the present disclosure, a cutting tool is used for cutting workpieces made of non-ferrous metals and their alloys, wood, wood-based materials, or resins. A coating is provided to cover the substrate. The coating is provided on the flank of the cutting edge where the rake face and the flank face intersect, and has a columnar structure standing up from the substrate. The coating's constituent material includes one or more of chromium nitride, oxynitride, oxide, carbide, carbonate, carbonitride, and carbonate-nitride.

[0008] Therefore, the chromium-containing coating applied to the flank can enhance the durability of the cutting tool. When chipping or cracking occurs in the coating covering the flank from the substrate, the direction of the cracking can be restricted to the direction of the columnar structures. This prevents chipping or cracking from spreading over a wide area of ​​the flank coating, making it less likely for the flank coating to become thin. This helps maintain the sharpness of the cutting edge.

[0009] According to another feature of the present disclosure, a second coating is provided over the coating. The second coating includes one or more of chromium nitride, oxynitride, oxide, carbide, carbonate, carbonitride, and carbonitride. Therefore, for example, by providing a second coating made of a material with higher wear resistance and corrosion resistance than the coating, wear, corrosion, and the like can be suppressed. The coating on the substrate side can control chipping and film cracking on the flank face. The outer second coating can suppress wear, corrosion, and the like on the flank face. This further suppresses damage to the cutting edge adjacent to the flank face.

[0010] Another feature of the present disclosure relates to a method for manufacturing a cutting tool for machining a workpiece made of non-ferrous metals and their alloys, wood, wood-based materials, or resin. A coating is formed on a substrate so as to include columnar structures standing on the surface of the substrate. The coating is made of a material containing one or more of chromium nitride, oxynitride, oxide, carbide, carbonate, carbonitride, and carbonitride. The coating is formed on both the rake face and the flank face. Part or all of the coating on the rake face is removed to sharpen the cutting edge where the rake face and the flank face intersect.

[0011] Therefore, the durability of the flank and rake face can be improved by the coating containing a chromium material provided on the flank and rake face. Furthermore, when chipping or film cracking progresses within the coating, its direction of progression can be restricted to the direction of the columnar structure. This prevents chipping or film cracking from spreading to the flank or rake face. Furthermore, when sharpening the cutting edge, part or all of the coating covering the rake face is removed. This allows the cutting edge to be sharpened without removing the coating covering the flank. Therefore, the flank has a coating with a columnar structure even after the cutting edge has been sharpened. Therefore, damage to the cutting edge adjacent to the flank due to chipping or film cracking can be suppressed. Thus, the cutting edge can be maintained sharp for a long time. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a perspective view of a cutting tool according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional schematic view of a cutting edge of a blade body. [Figure 3] 1 is a table showing the conditions of the coatings applied to the test samples and the comparative samples. [Figure 4] 1 is a photograph of the flank cross section of test piece 20 observed with an electron microscope. [Figure 5] 1 is a photograph of the flank cross section of comparative product 30 observed with an electron microscope. [Figure 6] 1 is a photograph of the flank cross section of comparative product 40 observed with an electron microscope. [Figure 7] 1 is a photograph of the cutting edge of test piece 20 after cutting, observed with an electron microscope. [Figure 8] 1 is a photograph of the cutting edge of comparative product 30 after cutting, observed with an electron microscope. [Figure 9] 1 is a photograph of the cutting edge of comparative product 40 after cutting, observed with an electron microscope. [Figure 10] 1A and 1B are cross-sectional views of the cutting edge of the test piece 20 before and after cutting. [Figure 11] 10A and 10B are cross-sectional views of the cutting edge of the comparative product 30 before and after cutting. [Figure 12]4A and 4B are cross-sectional views of the cutting edge of the comparative product 40 before and after cutting. [Figure 13] FIG. 10 is a side view of a cutting tool according to a second embodiment. [Figure 14] FIG. 2 is a cross-sectional schematic view of a cutting edge of a blade body. [Figure 15] 1 is a table showing the conditions of the coatings applied to the test samples and the comparative samples. [Figure 16] 1 is a photograph of the flank cross section of test piece 70 observed with an electron microscope. [Figure 17] 1 is a photograph of the flank cross section of test piece 80 observed with an electron microscope. [Figure 18] 1 is a photograph of the flank cross section of comparative product 90 observed with an electron microscope. [Figure 19] 1 is a photograph of the flank cross section of comparative product 100 observed with an electron microscope. [Figure 20] This is a photograph of the cutting edge of test piece 70 after cutting 150 m, observed with an electron microscope. [Figure 21] This is a photograph of the cutting edge of test piece 70 after cutting 400 m, observed with an electron microscope. [Figure 22] 1 is a photograph of the cutting edge of test piece 80 after cutting, observed with an electron microscope. [Figure 23] 1 is a photograph of the cutting edge of comparative product 90 after cutting, observed with an electron microscope. [Figure 24] 1 is a photograph of the cutting edge of Comparative Product 100 after cutting, observed with an electron microscope. [Figure 25] 10A and 10B are cross-sectional views of the cutting edge of the test piece 70 before and after cutting 150 m. [Figure 26] 10A and 10B are cross-sectional views of the cutting edge of the test piece 70 before and after cutting 400 m. [Figure 27] 1A and 1B are cross-sectional views of the cutting edge of a test piece 80 before and after cutting. [Figure 28] 10A and 10B are cross-sectional views of the cutting edge of a comparative product 90 before and after cutting. [Figure 29] 1A and 1B are cross-sectional views of the cutting edge of the comparative product 100 before and after cutting. DETAILED DESCRIPTION OF THE INVENTION

[0013] The cutting tool according to the present disclosure is used to cut a workpiece. The workpiece may be made of, for example, non-ferrous metals such as aluminum and copper, alloys thereof, wood, woody materials, or resin. The technology of the present disclosure can be applied to cutting tools such as flat blades such as plane blades, cutters, chip saws, router bits, knives, and chisels. It can also be applied to replacement blades for these cutting tools.

[0014] The blade provided in the cutting tool has a substrate and a coating that coats the substrate. The substrate is made of steel such as tool steel, bearing steel, or stainless steel, or cemented carbide. The coating coats at least the flank face of the substrate. The rake face of the substrate may or may not be coated with the coating. In other words, a coating is formed that coats the flank face or coats both the flank face and the rake face.

[0015] A cutting tool according to a first embodiment of the present disclosure will be described with reference to the drawings. As shown in FIGS. 1 and 2 , the cutting tool of the first embodiment is a replaceable blade 1. The replaceable blade 1 is attached to, for example, a replaceable-blade milling cutter for woodworking or a replaceable-blade router bit. The replaceable blade 1 has a rectangular plate-shaped blade body 2. The blade body 2 is provided with a through-hole 6 that penetrates in the plate thickness direction. The blade body 2 is attached to the tool body by fitting the through-hole 6 into a blade attachment portion of the tool body and fastening it with a screw. The blade body 2 has a flank 3 and a rake face 4 that are finished to a flat surface. The flank 3 and the rake face 4 intersect at a cutting edge angle 5a, forming a linear cutting edge 5 at the intersection. The cutting edge angle 5a is an acute angle, e.g., 50° to 60°. With the cutting edge 5 cutting into the workpiece to a predetermined cutting depth, the replaceable blade 1 is moved relative to the workpiece in the cutting direction shown in the drawing. As a result, the cutting edge 5 cuts the workpiece to the predetermined cutting depth.

[0016] As shown in Figure 2, a coating 14 that coats the substrate 10 is formed on the flank 3 and the rake face 4. The coating 14 has a flank coating 15 that coats the substrate flank 11 and a rake face coating 16 that coats the substrate rake face 12.

[0017] 2 includes one or more of chromium nitride, oxynitride, oxide, carbide, carbonate, carbonitride, and carbonate-nitride. Examples of the coating 14 include chromium nitride (CrN), chromium oxynitride (CrNO), chromium oxide (CrO), chromium carbide (CrC), chromium carbonate (CrCO), chromium carbonitride (CrCN), and chromium carbonate-nitride (CrCNO). The coating 14 has a single-layer structure made of one or more chromium materials.

[0018] As shown in FIG. 2, the flank coating 15 is coated on the substrate flank 11. The lower limit of the film thickness 15a of the flank coating 15 is, for example, 3 μm, 5 μm, or 7 μm. The upper limit of the film thickness 15a is, for example, 12 μm, 15 μm, or 20 μm. The film thickness 15a is within the range of each combination of the exemplified lower and upper limits. The film thickness 15a is preferably 5 to 12 μm. The lower limit of the film thickness 15a is set to a film thickness at which the film functions. The upper limit of the film thickness 15a is set to reduce the film formation time and manufacturing costs.

[0019] The flank coating 15 shown in FIG. 2 has a columnar structure rising from the substrate flank 11. The columnar structure is formed by a plurality of columnar particles rising in parallel along the thickness direction of the coating (film thickness). The columnar structure preferably has the same length as the film thickness 15a. The length of the columnar structure may be, for example, 50% or more, 60% or more, 70% or more, 80% or more, or 90% or more of the film thickness 15a. The columnar structure rises, for example, in a direction at an angle of 60° to 120° relative to the substrate flank 11. Adjacent columnar particles preferably rise at the same inclination angle. For example, when the film thickness 15a is 7.5 μm, the particle diameter (thickness) of the particles constituting the columnar structure is 1 to 5 μm. The length, particle diameter, inclination angle, etc. of the columnar structure were measured from a photograph (see FIG. 4) of the cross section of the blade body 2 observed with an electron microscope.

[0020] As shown in Figure 2, chipping and film cracking from the substrate cutting edge 13 toward the flank coating 15 progress along the extension direction of the columnar structure. Therefore, chipping and film cracking progress along the direction of the arrow shown in the flank coating 15 in the figure. In other words, chipping and film cracking do not spread in a direction approximately parallel to the flank 3, for example.

[0021] As shown in Figure 2, the rake face coating 16 has its upper layer removed above the rake face 4 during the manufacturing process of the replaceable blade 1. The rake face 4 is a flat surface that is approximately parallel to the substrate rake face 12 and has a film thickness (distance) 16a from the substrate rake face 12. By finishing the rake face 4, the cutting edge 5 is formed to be sharp. It is also possible to configure the film thickness 16a to be 0 μm, and to remove the entire rake face coating 16.

[0022] A cutting tool according to a second embodiment of the present disclosure will be described with reference to the drawings. As shown in Figures 13 and 14, the cutting tool of the second embodiment is, for example, a router bit 50 for woodworking. The router bit 50 is cylindrical and cuts a workpiece by rotating around the axis 51a of the shank 51. A blade body 55 is brazed to a recessed tip seat 52 at the tip of the shank 51. A chip discharge groove 53 is provided at the front of the blade body 55 in the direction of rotation to discharge chips generated during cutting.

[0023] As shown in Figures 13 and 14, the cutting body 55 has a flank 56 and a rake face 57. The flank 56 and the rake face 57 intersect at a cutting edge angle 58a, forming a linear cutting edge 58 at the intersection. The cutting edge angle 58a is an acute angle, for example, 50° to 60°. The rake face 57 faces generally forward in the direction of rotation of the router bit 50. The flank 56 faces generally radially outward from the router bit 50. The router bit 50 is rotated with the cutting edge 58 cutting into the workpiece to a predetermined depth of cut. By moving the router bit 50 relative to the workpiece in the cutting direction shown in Figure 14, the cutting edge 58 cuts the workpiece to a predetermined depth of cut.

[0024] As shown in FIG. 14 , the flank 56 and rake face 57 of the router bit 50 are flat surfaces following the substrate flank 61 and substrate rake face 62. The substrate flank 61 and substrate rake face 62 intersect at a cutting edge angle 58a to form a substrate cutting edge 63 at the intersection. The rake face 57 includes a coating 64 that coats the substrate 60, and the coating 64 is exposed at the rake face 57. The flank 56 has a flank coating 66 that includes the coating 64 and a second coating 65. The second coating 65 coats the coating 64, and the second coating 65 is exposed at the flank 56.

[0025] The coating 64 and the second coating 65 shown in FIG. 14 contain one or more of chromium nitride, oxynitride, oxide, carbide, carbonate, carbonitride, and carbonate nitride. Examples of the coating 64 and the second coating 65 include chromium nitride (CrN), chromium oxynitride (CrNO), chromium oxide (CrO), chromium carbide (CrC), chromium carbonate (CrCO), chromium carbonitride (CrCN), and chromium carbonate nitride (CrCNO). The coating 64 and the second coating 65 each have a single-layer structure containing one or more chromium materials. The coating 64 and the second coating 65 preferably have different types and mixing ratios of chromium materials, but may have the same type and / or mixing ratio of chromium materials.

[0026] As shown in FIG. 14 , in the flank coating 66, the coating 64 covers the substrate flank 61 with a thickness 66a. In the flank coating 66, the second coating 65 covers the coating 64 with a thickness 66b. The ratio of the thickness 66a of the coating 64 to the thickness 66b of the second coating 65 is, for example, 1:1 to 3:1, and preferably 1.5:1 to 2.5:1. The lower limit of the total thickness 66c, which is the sum of the thickness 66a of the coating 64 and the thickness 66b of the second coating 65, is, for example, 3 μm, 5 μm, or 7 μm. The upper limit of the total thickness 66c is, for example, 12 μm, 15 μm, or 20 μm. The total thickness 66c falls within the range of each combination of the exemplified lower and upper limits. The total thickness 66c is preferably 5 to 12 μm.

[0027] The coating 64 shown in FIG. 14 has a columnar structure in the flank coating 66 that rises from the substrate flank 61. The columnar structure is formed by parallel arrangement of multiple columnar particles that rise in a direction perpendicular to the substrate flank 61. The columnar structure preferably has the same length as the film thickness 66a of the coating 64. The length of the columnar structure may be, for example, 50% or more, 60% or more, 70% or more, 80% or more, or 90% or more of the film thickness 66a of the coating 64. The columnar structure rises, for example, in a direction at an angle of 60° to 120° relative to the substrate flank 61. The angle is within a range of ±30° relative to the direction perpendicular to the substrate flank 61 (90°). Adjacent columnar particles preferably rise at the same inclination angle. The particle diameter (thickness) of the particles that make up the columnar structure is, for example, 1 to 3 μm, assuming that the film thickness 66a of the coating 64 is 5 μm. The length, particle size, and inclination angle of the columnar structure were measured using a photograph of the cross section of the blade 55 observed with an electron microscope (see FIG. 16).

[0028] 14 has columnar structures rising from the coating 64 in the flank coating 66. Alternatively, the second coating 65 may have a granular structure made up of a plurality of particles in which no clear columnar structures can be discerned in the flank coating 66. The particle diameter of the particles in the second coating 65 is, for example, 50 to 150% of the particle diameter of the particles making up the coating 64.

[0029] 14, chipping and cracking from the substrate cutting edge 63 toward the flank coating 66 progress along the extending direction of the columnar structure of the coating 64. Therefore, chipping and cracking progress along the direction of the arrow shown in the coating 64 of the flank coating 66 in the figure.

[0030] As shown in FIG. 14 , the rake face coating 67 has its upper layer removed from the rake face 57. The rake face 57 is a plane approximately parallel to the substrate rake face 62, with a film thickness (distance) 67a from the substrate rake face 62. Alternatively, the rake face 57 may be located on the substrate rake face 62 (film thickness 67a is 0 μm). Alternatively, the rake face 57 may be located within the coating 64, at the interface between the coating 64 and the second coating 65, or within the second coating 65. By finishing the rake face 57, the cutting edge 58 is formed sharply. The rake face 57 may not be parallel to the substrate rake face 62, but may be inclined in a direction that reduces the amount of finishing (amount removed) and increases the cutting angle. This facilitates finishing (polishing). The entire rake face coating 67 may be removed, and the substrate rake face 62 may serve as the rake face 57. Since the base material of the rake face 57 wears away first, the cutting edge 58 is maintained sharp by the coating 64 and the second coating 65 .

[0031] The method for manufacturing a cutting tool coated with a coating begins with forming a substrate having a flank and a rake face (Step 1). A coating material containing a chromium material is prepared. If a second coating is to be formed, an additional material containing another chromium material is prepared if necessary (Step 2). A coating containing a chromium material is applied to the flank and rake face of the substrate using a PVD process (Step 3). When forming a coating with a columnar structure that coats the flank and rake face of the substrate, the coating is grown in a columnar shape in a direction that rises from the flank and rake face of the substrate. In other words, the crystals are grown so that the grain size is larger and extends longer in a specified direction than in conventional PVD coating formation.

[0032] The columnar structure of the coating covering the flank face is allowed to grow until it reaches a predetermined length (Step 4). If a second coating is to be applied, a coating is first formed on the base flank face and base rake face, and then a second coating is formed on top of the first coating. After the coating is formed, the rake face is ground flat to remove part or all of the top layer of the coating covering the rake face (Step 5). This gives the cutting edge where the rake face and flank face intersect a sharp finish.

[0033] Arc ion plating can be used as the PVD in step 3. Alternatively, magnetron sputtering, for example, can be used as the PVD. Regarding step 4, CrN, CrNO, CrO, CrC, CrCO, CrCN, and CrCNO can all be formed into large grains and long columnar structures using the same PVD process. [Example]

[0034] Examples according to the present disclosure will be described below using specific numbers. As shown in FIG. 3, a test sample 20 according to Example 1, a comparison sample 30, and a comparison sample 40 were prepared. The test sample 20 of Example 1 is the replaceable blade 1 of the first embodiment. The comparison samples 30 and 40 are replaceable blades in which the same cemented carbide substrate as the test sample 20 is coated with a coating of a conventional coating structure. The test sample 20, comparison sample 30, and comparison sample 40 are coated with a single layer of coating made of chromium nitride (CrN). The coating does not contain chromium oxide (Cr2O3).

[0035] As shown in Figure 4, a coating 21 is coated on a substrate 27 of a test piece 20. A flank coating 22 coated on a substrate flank 28 is formed with a film thickness 22a of 7.5 µm. The flank coating 22 has a columnar structure that stands up from the substrate flank 28 in a direction substantially perpendicular to the substrate flank 28. The tips of the columnar structures are exposed on the flank 24. The entire coating on the rake face 25 was removed by grinding (see Figure 7).

[0036] As shown in Figure 5, a substrate 37 of the comparative product 30 is coated with a coating 31. A flank coating 32 coated on the substrate flank 38 is formed with a film thickness 32a of 7.6 µm. The flank coating 32 includes columnar structures extending in a direction substantially perpendicular to the substrate flank 38, but these columnar structures are short, approximately 10% of the film thickness 32a. Granular structures with smaller grain sizes than the columnar structures are formed in the gaps between the columnar structures. The flank coating 32 has an intermediate structure between the columnar structure and the granular structure. The tips of both the columnar structure and the granular structure are exposed on the flank 34. The entire coating on the rake face 35 was removed by grinding (see Figure 8).

[0037] As shown in Figure 6, a substrate 47 of the comparative product 40 is coated with a coating 41. A flank coating 42 coated on the substrate flank 48 is formed with a film thickness 42a of 7.8 µm. The flank coating 42 has a grain size smaller than that of the grains constituting the flank coating 22 (see Figure 4), and has a granular structure in which the longitudinal direction cannot be clearly discerned. The tips of the granular structure are exposed on the flank 44. The entire coating on the rake face 45 was removed by grinding (see Figure 9).

[0038] A cutting test was conducted on red pine plywood using a cutter (cutting diameter 35 mm) equipped with replaceable blade 1. The cutting conditions were a rotation speed of 7714 rpm, a workpiece feed rate of 0.643 m / min, a radial depth of cut of the cutting tool into the workpiece of 9 mm, and an axial depth of cut of the cutting tool of 9 mm, and 150 m of workpiece was cut. The sharpness of the cutting edge 5 after cutting was evaluated based on the observation of the condition of the cutting edge 5 after cutting and the measurement of the change in the cutting edge line before and after cutting. The change in the cutting edge line was evaluated based on the amount of recession of the cutting edge on the rake face 4 and the roundness radius of the cutting edge 5.

[0039] As shown in Figure 7, after the cutting test of the test piece 20, crater wear was formed along the cutting edge 26a on the rake face 25a due to wear, and the cutting edge 26a extended linearly. The cutting edge 26a, which is made of the coating 21, chipped and cracked in the columnar direction, but the chipping and cracking did not spread toward the flank face 24a. The film thickness and cutting edge shape were maintained.

[0040] As shown in Fig. 10, the amount of recession of the cutting edge of the rake face after the cutting test of the test piece 20 is about 9 µm. The cutting edge 26a after the cutting test maintains a sharp state with an extremely small radius of roundness compared to the cutting edge 26 before the cutting test.

[0041] As shown in FIG. 8, after the cutting test of the comparative product 30, the rake face 35a and flank 34a were worn, and the thickness of the coating 31 on the cutting edge 36a was not maintained.

[0042] As shown in Figure 11, after the cutting test of the comparative sample 30, the amount of recession of the cutting edge on the rake face was about 16 μm. Compared to the cutting edge 36 before the cutting test, the cutting edge 36a after the cutting test had a rounded shape with a larger radius, and the sharp cutting edge of the coating was lost.

[0043] As shown in FIG. 9, after the cutting test of the comparative product 40, the rake face 45a and the flank 44a were worn, and the thickness of the coating 41 on the cutting edge 46a was not maintained.

[0044] As shown in Fig. 12, after the cutting test of the comparative product 40, the amount of recession of the cutting edge of the rake face is about 12 µm. Compared to the cutting edge 46 before the cutting test, the cutting edge 46a after the cutting test has a rounded shape with a larger radius, and the sharp cutting edge of the coating is impaired.

[0045] As shown in Figures 7 to 12, Test Sample 20 with a columnar structure showed little recession of the cutting edge on the rake face even after 150 meters of cutting, and it was found that the sharp cutting edge was maintained. After 150 meters of cutting, Comparison Sample 30 with an intermediate structure showed chipping of the cutting edge, which became rounded and lost its sharpness. Comparison Sample 40 with a granular structure showed more chipping of the cutting edge than Comparison Sample 30, and its sharpness was further lost.

[0046] A cutting test was conducted on red pine plywood using a router bit 50 (cutting diameter: 12 mm). The cutting conditions were a rotation speed of 18,000 rpm, a workpiece feed rate of 0.643 m / min, a radial cutting depth of 3 mm, and an axial cutting depth of 10 mm. 150 m of workpiece was cut. For specimen 70, a 400 m cutting test was also conducted, which is longer than the normal tool life. The sharpness of the cutting edge 58 after cutting was evaluated based on the condition of the cutting edge 58 after cutting and the measurement of the change in the cutting edge line before and after cutting. The change in the cutting edge line was evaluated based on the amount of recession on the rake face and the radius of the cutting edge 58.

[0047] As shown in Figure 15, test specimens 70 and 80 according to the second example and comparative specimens 90 and 100 were prepared. Test specimen 70 was the router bit 50 of the second embodiment (see Figure 13). The blade of test specimen 80 corresponded to blade body 2 of the first embodiment (see Figure 2). Comparative specimens 90 and 100 were router bits with the same substrate as test specimen 70 but coated with a conventional coating structure. Test specimen 70 and comparative specimen 90 were coated with a chromium nitride (CrN) coating and a second chromium oxide (Cr2O3) coating. Test specimen 80 and comparative specimen 100 were coated only with a chromium nitride (CrN) coating and not with a second chromium oxide (Cr2O3) coating. The entire coating on the rake faces of test specimens 70 and 80 and comparative specimens 90 and 100 was removed by grinding.

[0048] As shown in Figure 16, a substrate 78 of a test piece 70 is coated with a coating 71 and a second coating 72. Coating 71 of the flank coating 73 coated on a substrate flank 79 is formed with a film thickness 73a of 5.3 µm. Second coating 72 coated on coating 71 of the flank coating 73 is formed with a film thickness 73b of 2.7 µm. In other words, the total film thickness 73c of the flank coating 73 is 8 µm, and the ratio of film thickness 73a of coating 71 to film thickness 73b of second coating 72 is approximately 2:1.

[0049] As shown in Figure 16, in the flank coating 73, the coating 71 has columnar structures that stand up from the substrate flank 79 in a direction approximately perpendicular to the substrate flank 79. The columnar structures extend in the thickness direction with a length equal to the film thickness 73a. The second coating 72 is composed of an intermediate structure consisting of columnar structures that are shorter in the thickness direction than the particles of the coating 71 and granular structures whose particle diameters are smaller than those of the particles of the coating 71. The tips of the granular structures of the second coating 72 are exposed on the flank 75.

[0050] As shown in FIG. 17 , a substrate 87 of a test piece 80 is coated with a coating 81. A flank coating 82 coated on a substrate flank 88 is formed with a film thickness 82a of 7.5 μm. The flank coating 82 has a columnar structure extending in a direction inclined at approximately 60° with respect to the substrate flank 88. The columnar particles extend in the thickness direction with a length equal to the film thickness 82a. The tips of the columnar structures are exposed on the flank 84.

[0051] As shown in Figure 18, a substrate 98 of a comparative product 90 is coated with a coating 91 and a second coating 92. Coating 91 of a flank coating 93 coated on a substrate flank 99 is formed with a film thickness 93a of 5.3 µm. Second coating 92 coated on coating 91 of flank coating 93 is formed with a film thickness 93b of 2.7 µm. In other words, the total film thickness 93c of flank coating 93 is 8 µm, and the ratio of film thickness 93a of coating 91 to film thickness 93b of second coating 92 is approximately 2:1.

[0052] 18, in the flank coating 93, the coating 91 has a granular structure in which the longitudinal direction cannot be clearly determined. The second coating 92 is composed of a granular structure with a larger grain size than the grains of the coating 91. The tips of the granular structure of the second coating 92 are exposed on the flank 95.

[0053] As shown in Figure 19, a substrate 107 of a comparative product 100 is coated with a coating 101. A flank coating 102 coated on a substrate flank 108 is formed with a film thickness 102a of 3.5 µm. The particles that make up the flank coating 102 are smaller in diameter than the columnar particles of the flank coating 82 (see Figure 17) and are granular in shape with no clear longitudinal direction. The tips of the granular particles are exposed on the flank 104.

[0054] As shown in Figure 20, after a 150-m cutting test of the test piece 70, crater wear was formed on the rake face 76a along the cutting edge 77a, and the cutting edge 77a clearly extended in a straight line. When chipping or film cracking occurred, it occurred in the columnar direction of the flank coating 73, as shown schematically in the figure, and columnar particles fell off one by one from the tip while maintaining the sharpness of the cutting edge 77a. Therefore, chipping or film cracking did not spread toward the flank 75a. The film thickness was maintained before and after chipping or film cracking, and the cutting edge shape was maintained.

[0055] As shown in Figure 21, after a 400m cutting test of the test piece 70, crater wear was formed along the cutting edge 77b on the rake face 76b due to wear, and the cutting edge 77b extended linearly. No chipping or film cracking occurred in the direction of the flank face 75b. The film thickness and cutting edge shape were maintained.

[0056] As shown in Figure 25, after a 150 m cutting test of the test piece 70, the amount of recession of the cutting edge of the rake face (76, 76a) is about 6 μm. The cutting edge 77a after the cutting test maintains a sharp state with an extremely small radius of roundness compared to the cutting edge 77 before the cutting test.

[0057] As shown in Figure 26, after a 400 m cutting test of the test piece 70, the amount of recession of the cutting edge of the rake face (76, 76b) is about 15 μm. The cutting edge 77b after the cutting test has an enlarged radius of roundness and a slightly rounded shape compared to the cutting edge 77 before the cutting test.

[0058] As shown in Figure 22, after a 150m cutting test of the test piece 80, a depression was formed along the cutting edge 86a due to wear on the rake face 85a, but the cutting edge 86a remained in a generally linear state. No chipping or film cracking spread toward the flank face 84a. The film thickness was maintained, and the cutting edge shape was generally maintained.

[0059] 27, after a 150 m cutting test of the test piece 80, the amount of recession of the cutting edge of the rake face (85, 85a) is about 8 μm. The cutting edge 86a after the cutting test remains sharp compared to the cutting edge 86 before the cutting test.

[0060] As shown in Figure 23, after a 150-m cutting test of the comparative product 90, a dent was formed along the cutting edge 97a due to wear on the rake face 96a. However, the coating on the flank 95a had cracks, with the cemented carbide substrate of the cutting edge 97a at its apex. Compared to the cutting edge 77a (see Figure 20) and the cutting edge 86a (see Figure 22), the cutting edge 97a has a rounded shape with the corners on the flank 95a removed. In other words, the coating does not maintain its sharp cutting edge. When chipping or cracking occurs, granular particles located on the cutting edge 97a fall off, as shown schematically in the figure. As a result, the chipping or cracking spreads in the cutting direction, resulting in the entire cutting edge 97a becoming uniformly rounded.

[0061] As shown in Figure 28, after a 150m cutting test of the comparative sample 90, the amount of recession of the cutting edge of the rake face (96, 96a) is about 15 μm. The cutting edge 97a after the cutting test has a rounded shape with a larger radius than the cutting edge 97 before the cutting test. In other words, the sharp cutting edge of the coating has been damaged.

[0062] As shown in Fig. 24, after a 150m cutting test of the comparative product 100, the rake face 105a and the flank 104a are worn. The coating is cracked and the coating as the cutting edge 106a is chipped.

[0063] As shown in Figure 29, after a 150m cutting test of the comparative product 100, the amount of recession of the cutting edge of the rake face (105, 105a) is about 12μ. After the cutting test, the cutting edge 106a is worn. The coating is cracked and the coating as the cutting edge 106a is chipped. Compared to the cutting edge 106 before the cutting test, the sharpness of the coating has been impaired.

[0064] As shown in Figures 20-29, the columnar structure specimens 70 and 80 maintained their sharp cutting edge even after 150 meters of cutting. The columnar structure specimen 70, which had an oxide coating, maintained its sharp cutting edge on the rake face. The columnar structure specimen 70 had a smaller recession on the rake face than the specimen 80, which had no oxide coating. The comparative specimen 90, which had a granular structure specimen coated with an oxide coating, had chipped and rounded cutting edges after 150 meters of cutting, impairing its sharpness. The comparative specimen 100, a conventionally known specimen with a granular structure, had a sharper cutting edge than the comparative specimen 90 due to cracking and wear in the flank direction of the coating. The recession on the rake face of the specimen 70 after 150 meters of cutting was less than half that of the comparative specimen 100, and the sharpness of the coating was maintained even after 400 meters of cutting.

[0065] The various embodiments described in detail above with reference to the accompanying drawings are exemplary of the present invention and are not intended to limit the scope of the present invention. The detailed description teaches one of ordinary skill in the art how to make, use, and / or practice various aspects of the present teachings, but is not intended to limit the scope of the present invention. Furthermore, each of the additional features and teachings described above may be applied and / or used separately or in conjunction with other features and teachings to provide improved cutting tools and / or methods of making and using the same.

Claims

1. A cutting tool for cutting a workpiece made of non-ferrous metals and their alloys, wood, wood-based materials, or resin, a coating that covers a substrate, the coating being provided on the flank along a cutting edge where a rake face and a flank intersect, and having a columnar structure that stands up from the substrate; the coating comprises one or more of a nitride, an oxynitride, an oxide, a carbide, a carbonate, a carbonitride, and a carbonitride of chromium; a second coating covering the coating, the second coating including one or more of nitride, oxynitride, oxide, carbide, carbonate, carbonitride, and carbonate nitride of chromium; a cutting tool in which the thickness of the second coating on the flank face is equal to or less than the thickness of the coating.

2. A method for manufacturing a cutting tool for cutting a workpiece made of non-ferrous metals and their alloys, wood, woody materials, or resins, comprising: forming a coating on a substrate so as to include columnar structures standing on a surface of the substrate, the coating being made of a material containing one or more of chromium nitride, oxynitride, oxide, carbide, carbonate, carbonitride, and carbonate nitride, and the coating being formed over a rake face and a flank face; forming a second coating on the outside of the coating, the second coating containing one or more of nitride, oxynitride, oxide, carbide, carbonate, carbonitride, and carbonate nitride of chromium, the second coating being formed over the rake face and the flank face; A method for manufacturing a cutting tool, comprising removing part or all of the coating and all of the second coating from the rake face, or removing part of the second coating from the rake face, to sharpen a cutting edge where the rake face and the flank intersect, and making the film thickness of the second coating on the flank equal to or less than the film thickness of the coating.

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