Cutting tool

Abstract

A cutting tool according to the present invention comprises a base material and a diamond layer that covers the base material. The cutting tool has a rake surface and a flank surface. The flank surface is continuous with the rake surface. The ridgeline between the rake surface and the flank surface forms a cutting edge. The diamond layer has a flank surface–covering part. The flank surface–covering part forms the flank surface. The thickness of the flank surface–covering part is 10–25 μm. In a cross-section that is orthogonal to a tangent to the cutting edge, the radius of curvature of the cutting edge is less than the value obtained by multiplying the thickness of the flank surface–covering part by 0.3. The rake surface includes a first portion. The first portion is formed from the flank surface–covering part. The first portion is continuous with the flank surface. The maximum height roughness of the first portion is less than 2 μm.

Description

cutting tools

[0001] The present disclosure relates to cutting tools.

[0002] Japanese Patent Laid-Open Publication No. 2015-085462 (Patent Document 1) discloses a hard-coated cutting tool having a tool body with a diamond coating, the tool body having a cutting edge formed at the intersection ridge between the flank and rake face. In this hard-coated cutting tool, the thickness of the diamond coating on the flank side is 8 μm to 30 μm. When the roundness of the cutting edge of the cutting edge is approximated by an arc with a radius, the radius is 0.1 to 0.8 times the thickness of the diamond coating on the flank side.

[0003] JP 2015-085462 A

[0004] The cutting tool according to the present disclosure is a cutting tool comprising a substrate and a diamond layer coating the substrate. The cutting tool comprises a rake face and a flank. The flank is continuous with the rake face. A ridge between the rake face and the flank forms a cutting edge. The diamond layer has a flank coating portion. The flank coating portion forms the flank. The thickness of the flank coating portion is 10 μm or more and 25 μm or less. In a cross section perpendicular to a tangent to the cutting edge, the radius of curvature of the cutting edge is less than a value obtained by multiplying the thickness of the flank coating portion by 0.3. The rake face includes a first portion. The first portion is formed by the flank coating portion. The first portion is continuous with the flank. The maximum height roughness of the first portion is less than 2 μm.

[0005] FIG. 1 is a schematic plan view showing a cutting tool according to a first embodiment. FIG. 2 is an enlarged schematic plan view showing region II of FIG. 1. FIG. 3 is an enlarged schematic side view showing the configuration of the cutting tool according to the first embodiment. FIG. 4 is a schematic cross-sectional view taken along line IV-IV of FIG. 2. FIG. 5 is an enlarged schematic cross-sectional view showing region V of FIG. 4. FIG. 6 is a flow chart outlining a method for manufacturing a cutting tool according to the first embodiment. FIG. 7 is a schematic cross-sectional view showing a step of sharpening a cutting edge by laser processing a rake face. FIG. 8 is a schematic cross-sectional view showing a configuration of a cutting tool according to a second embodiment. FIG. 9 is a schematic cross-sectional view showing a step of sharpening a cutting edge by laser processing a rake face in the method for manufacturing a cutting tool according to the second embodiment. FIG. 10 is a partial schematic cross-sectional view showing a cutting tool according to the present disclosure in use.

[0006] [Problems to be Solved by the Present Disclosure] When the cutting edge of a cutting tool is covered with a diamond layer, the wear resistance of the tool improves as the thickness of the diamond layer increases. The sharpness of the cutting edge improves as the radius of curvature of the cutting edge decreases. This reduces damage to the cutting tool. However, even when the diamond layer is thick and the radius of curvature of the cutting edge is small, adhesion of chips to the cutting edge may occur due to the surface condition of the diamond layer. This results in the formation of a built-up edge, which makes the tool more susceptible to damage. As described above, it has been difficult to improve the tool life of cutting tools having a diamond layer.

[0007] An object of the present disclosure is to provide a cutting tool capable of improving the tool life. [Effects of the Present Disclosure] According to the present disclosure, it is possible to provide a cutting tool capable of improving the tool life.

[0008] [Outline of the embodiment] First, an outline of the embodiment of the present disclosure will be described.

[0009] (1) A cutting tool according to the present disclosure is a cutting tool having a substrate and a diamond layer coating the substrate. The cutting tool has a rake face and a flank. The flank is continuous with the rake face. A ridge between the rake face and the flank forms a cutting edge. The diamond layer has a flank coating portion. The flank coating portion forms the flank. The thickness of the flank coating portion is 10 μm or more and 25 μm or less. In a cross section perpendicular to a tangent to the cutting edge, the radius of curvature of the cutting edge is less than the value obtained by multiplying the thickness of the flank coating portion by 0.3. The rake face has a first portion. The first portion is formed by the flank coating portion. The first portion is continuous with the flank. The maximum height roughness of the first portion is less than 2 μm.

[0010] According to the cutting tool of the present disclosure, excessive protrusion of a part of the first portion is suppressed, which can suppress the occurrence of chip adhesion originating from the excessively protruding portion, thereby improving the tool life.

[0011] (2) According to the cutting tool of (1) above, the rake face may have a first rake face portion and a second rake face portion. The first rake face portion may be spaced apart from the flank face. The second rake face portion may be provided between the first rake face portion and the flank face. The second rake face portion may be continuous with each of the first rake face portion and the flank face. The second rake face portion may be inclined with respect to the first rake face portion in a direction from the first rake face portion toward the flank face. This allows the angle formed between the rake face and the flank face to be increased. This allows the strength of the cutting edge to be improved.

[0012] (3) According to the cutting tool of (2) above, the inclination angle of the second rake face portion relative to the first rake face portion may be 3° or more and 50° or less. When the inclination angle of the second rake face portion is 3° or more, excessive reduction in the strength of the cutting edge can be suppressed. When the second angle θ2 is 50° or less, excessive reduction in the sharpness of the cutting edge can be suppressed.

[0013] (4) According to the cutting tool of (2) above, the thickness of the flank covering portion may be 15 μm or more and 20 μm or less, thereby improving the wear resistance of the cutting tool.

[0014] (5) In the cutting tool according to any one of (1) to (4) above, the radius of curvature of the cutting edge in a cross section perpendicular to the tangent of the cutting edge may be less than a value obtained by multiplying the thickness of the flank covering portion by 0.1, thereby improving the sharpness of the cutting edge.

[0015] (6) In the cutting tool according to any one of (1) to (5) above, the substrate may be made of cemented carbide containing tungsten carbide particles. The tungsten carbide particles may have an average particle size of 2 μm or less. This can prevent the diamond layer from peeling off from the substrate. As a result, the tool life can be further improved.

[0016] (7) According to the cutting tool of any one of (1) to (6) above, the clearance angle of the flank may be 15° or more and 35° or less.

[0017] (8) According to the cutting tool according to any one of (1) to (7) above, the maximum height roughness of the first portion may be less than 1.5 μm.

[0018] [Details of the embodiment] Hereinafter, details of the embodiment of the present disclosure (hereinafter also referred to as the present embodiment) will be described with reference to the drawings. Note that the same or corresponding parts in the following drawings are designated by the same reference numerals, and description thereof will not be repeated.

[0019] First Embodiment <Configuration of Cutting Tool> First, the configuration of a cutting tool according to a first embodiment will be described.

[0020] 1 is a schematic plan view showing a cutting tool according to a first embodiment. The cutting tool 100 according to the first embodiment has a tip portion 6, a body portion 7, and a shank portion 8. The cutting tool 100 is, for example, a ball end mill. The cutting tool 100 is, for example, a rotary cutting tool that rotates about an axis X as a rotation axis.

[0021] Fig. 2 is an enlarged schematic plan view showing region II in Fig. 1. Fig. 3 is an enlarged schematic side view showing the configuration of cutting tool 100 according to the first embodiment. The enlarged schematic side view shown in Fig. 3 is an enlarged schematic side view seen along arrow A in Fig. 2.

[0022] 2 and 3, the cutting tool 100 has a rake face 1 and a flank 2. The rake face 1 is continuous with the flank 2. The ridge between the rake face 1 and the flank 2 forms a cutting edge 3. As shown in FIG. 2, when viewed perpendicularly to the rake face 1, a tangent to the cutting edge 3 is a first imaginary straight line 91.

[0023] Fig. 4 is a schematic cross-sectional view taken along line IV-IV in Fig. 2. The cross section shown in Fig. 4 is perpendicular to a first imaginary straight line 91 (see Fig. 2). As shown in Fig. 4, the cutting tool 100 has a substrate 4 and a diamond layer 5.

[0024] The substrate 4 has a first surface 41 and a second surface 42. The first surface 41 constitutes, for example, a part of the rake face 1. The second surface 42 is continuous with the first surface 41. The second surface 42 is substantially parallel to the flank face 2.

[0025] The diamond layer 5 covers at least a portion of the substrate 4. Specifically, the diamond layer 5 covers the second surface 42. The diamond layer 5 forms the flank 2. The portion of the diamond layer 5 that forms the flank 2 is defined as a flank coating portion 52. The first surface 41 is exposed from the diamond layer 5, for example.

[0026] The diamond layer 5 contains, for example, diamond crystals. The diamond layer 5 is made of, for example, diamond polycrystals. The diamond layer 5 may contain components other than diamond (for example, amorphous components). The diamond layer 5 may not contain diamond crystals. The diamond layer 5 may be made of, for example, DLC (Diamond Like Carbon).

[0027] The rake face 1 is, for example, planar. The rake face 1 is constituted by a flank covering portion 52 and the base material 4. The portion of the rake face 1 constituted by the flank covering portion 52 is defined as a first portion 16. The first portion 16 is continuous with the flank 2. From another perspective, the ridge line between the first portion 16 and the flank 2 constitutes the cutting edge 3. The portion of the rake face 1 constituted by the base material 4 is defined as a second portion 17. In other words, the rake face 1 has the first portion 16 and the second portion 17. The second portion 17 is substantially parallel to the first portion 16.

[0028] The thickness H of the flank covering portion 52 is 10 μm or more and 25 μm or less. The thickness H is the thickness of the flank covering portion 52 in a direction perpendicular to the flank 2. The thickness H may be, for example, 15 μm or more and 20 μm or less, or 15 μm or more and 17 μm or less. The thickness H may be, for example, 12 μm or more, or 14 μm or more. The thickness H may be, for example, 22 μm or less, or 18 μm or less.

[0029] <Maximum Height Roughness> The maximum height roughness defined as Rz (hereinafter also referred to as maximum height roughness Rz or Rz) is an index for quantifying surface roughness. The maximum height roughness Rz is a surface texture parameter defined in JIS (Japanese Industrial Standards) B0601:2013.

[0030] The Rz of the first portion 16 is less than 2 μm. The Rz of the first portion 16 may be, for example, 1.8 μm or less, less than 1.5 μm, or 1.2 μm or less. The Rz may be, for example, 0.01 μm or more, or 0.5 μm or more.

[0031] Rz is measured using, for example, a laser microscope ("OPTELICS HYBRID" (trademark) manufactured by Lasertech). For example, five different measurement areas are set within the first portion 16. Each of the five measurement areas is a linear area. The position of each of the five measurement areas is set to an arbitrary position within the first portion 16. The average value of Rz measured in each of the five measurement areas is taken to be the Rz of the first portion 16. In other words, the sum of the Rz values ​​of the five measurement areas divided by 5 is taken to be the Rz of the first portion 16. The measurement pitch is, for example, 0.1 μm. The measurement range is, for example, 10 μm.

[0032] <Radius of Curvature and Second Inclination Angle> Figure 5 is an enlarged schematic cross-sectional view showing region V in Figure 4. As shown in Figure 5, in a cross section perpendicular to the first imaginary line 91, the shape of the cutting edge 3 may be substantially arc-shaped. In a cross section perpendicular to the first imaginary line 91, the radius of curvature R of the cutting edge 3 is less than the value obtained by multiplying the thickness H (see Figure 4) of the flank covering portion 52 by 0.3. The radius of curvature R may be, for example, less than the value obtained by multiplying the thickness H by 0.2, or less than the value obtained by multiplying the thickness H by 0.1, or less than the value obtained by multiplying the thickness H by 0.08. The radius of curvature R is, for example, greater than the value obtained by multiplying the thickness H by 0.001. The radius of curvature R is, for example, 0.5 µm or greater and 7 µm or less.

[0033] As shown in FIGS. 4 and 5 , in a cross section perpendicular to the first imaginary line 91, a line perpendicular to the rake face 1 and tangent to the cutting edge 3 is defined as a second imaginary line 92. In the cross section perpendicular to the first imaginary line 91, the flank 2 is inclined with respect to the second imaginary line 92 in a direction from the cutting edge 3 toward the rake face 1. From another perspective, the flank 2 is inclined with respect to the second imaginary line 92 in a direction from the front end 58 toward the rear end 59. In the cross section perpendicular to the first imaginary line 91, the inclination angle of the flank 2 with respect to the second imaginary line 92 (first angle θ1) is, for example, 15° or more and 35° or less. The first angle θ1 may be, for example, 17° or more, or 19° or more. The first angle θ1 may be, for example, 33° or less, or 30° or less. The first angle θ1 is the clearance angle of the flank 2.

[0034] The radius of curvature R and the first angle θ1 are measured using, for example, a non-contact surface texture measuring device "PF-60" manufactured by Mitaka Kohki. For example, five different measurement areas are set on the rake face 1 and the flank face 2. Each of the five measurement areas is a linear area that extends substantially perpendicular to a tangent to the cutting edge 3 (first virtual straight line 91, see FIG. 2 ) and intersects with the cutting edge 3. The position of each of the five measurement areas is set to an arbitrary position within the first portion 16. The measurement pitch is, for example, 0.1 μm. The measurement range is, for example, 200 μm.

[0035] In each of the five measurement regions, curves indicating the shapes of the flank 2, cutting edge 3, and rake face 1 are obtained. Based on the five obtained curves, the radius of curvature of the cutting edge 3 in each of the five measurement regions is measured. The average value of the radii of curvature of the cutting edge 3 in the five measurement regions is taken as the radius of curvature R of the cutting edge 3 in the cutting tool 100. In other words, the sum of the radii of curvature of the cutting edge 3 in the five measurement regions divided by 5 is taken as the radius of curvature R of the cutting edge 3 in the cutting tool 100.

[0036] Similarly, the inclination angle of the flank 2 with respect to the second imaginary straight line 92 in each of the five measurement regions is measured based on the five curves obtained. The average value of the inclination angles of the flank 2 with respect to the second imaginary straight line 92 in the five measurement regions is set to be the first angle θ1. In other words, the sum of the inclination angles of the flank 2 with respect to the second imaginary straight line 92 in the five measurement regions divided by 5 is set to be the first angle θ1.

[0037] <Material of the Substrate> The substrate 4 is made of, for example, a cemented carbide containing tungsten carbide (WC) particles. The cemented carbide constituting the substrate 4 contains, for example, tungsten carbide particles and a binder such as cobalt.

[0038] The average particle size of the WC particles contained in the cemented carbide constituting the substrate 4 is, for example, 2 μm or less. The average particle size of the WC particles contained in the cemented carbide constituting the substrate 4 may be, for example, 1.5 μm or less, or 1 μm or less. The average particle size of the WC particles contained in the cemented carbide constituting the substrate 4 may be, for example, 0.01 μm or more, or 0.1 μm or more.

[0039] In this specification, the average particle size of the WC particles is the average value of the equivalent circle diameters of the WC particles. The average equivalent circle diameter of the WC particles means the arithmetic mean of the number of equivalent circle diameters of the WC particles measured on the surface or cross section of the cemented carbide. The average equivalent circle diameter of the tungsten carbide particles is measured by the following procedure.

[0040] Specifically, any surface or cross section of the cemented carbide is mirror-finished. Examples of mirror-finishing methods include polishing with diamond paste, using a focused ion beam (FIB) device, using a cross-section polisher (CP) device, and a combination of these methods.

[0041] The machined surface of the cemented carbide is photographed using a scanning electron microscope ("S-3400N" manufactured by Hitachi High-Technologies Corporation). Three images are prepared. Each of the three images captures a different area. The photographed location can be set as desired. The photographing conditions are backscattered electron images. The observation magnification is 5000x. The accelerating voltage is 10 kV.

[0042] The three captured backscattered electron images are imported into a computer using image analysis software (ImageJ, version 1.51j8: https: / / imagej.nih.gov / ij / ). The three captured backscattered electron images are then subjected to binarization processing. The binarization processing is performed under conditions preset in the image analysis software by pressing the "Make Binary" button on the computer screen after the images have been imported. In the image after binarization processing, tungsten carbide particles and areas other than the tungsten carbide particles can be distinguished by the shade of color. For example, in the image after binarization processing, tungsten carbide particles are shown as black areas, and areas other than the tungsten carbide particles are shown as white areas.

[0043] A rectangular measurement field of view measuring 25.3 μm in length and 17.6 μm in width is set in each of the three acquired images after binarization processing. Using the image analysis software, the circle-equivalent diameter (Heywood diameter: equivalent area circle-equivalent diameter) of each of all tungsten carbide particles (black areas) in the three measurement fields is measured. The number-based arithmetic mean value of the circle-equivalent diameters of all tungsten carbide particles in the three measurement fields is calculated. In this specification, this arithmetic mean value corresponds to the average circle-equivalent diameter of the WC particles.

[0044] As far as the applicant has measured, it has been confirmed that, as long as measurements are made on the same sample, even if the above measurement is performed multiple times by changing the selected location of the measurement field, there is little variation in the measurement results, and that setting the measurement field arbitrarily will not be arbitrary.

[0045] <Method of Manufacturing Cutting Tool> Next, a method of manufacturing the cutting tool 100 according to the first embodiment will be described.

[0046] Fig. 6 is a flow diagram that schematically shows a method for manufacturing a cutting tool according to the first embodiment. As shown in Fig. 6, the method for manufacturing cutting tool 100 includes a step (S10) of forming a diamond layer on a substrate, a step (S20) of sharpening the cutting edge by laser processing the rake face, and a step (S30) of smoothing the rake face by ion etching.

[0047] First, a step (S10) of depositing a diamond layer on a substrate is carried out. Specifically, diamond layer 5 is deposited on substrate 4 using, for example, HFCVD (Hot Filament Chemical Vapor Deposition). As a result, each of first surface 41 and second surface 42 of substrate 4 is covered with diamond layer 5.

[0048] Next, a step (S20) of sharpening the cutting edge by laser processing the rake face is carried out. Fig. 7 is a cross-sectional schematic diagram showing the step (S20) of sharpening the cutting edge by laser processing the rake face. As shown in Fig. 7, at least a portion of the diamond layer 5 constituting the rake face 1 is removed using laser processing. Specifically, a laser 81 is irradiated toward the cutting tool 100. The irradiation direction of the laser 81 is the direction along arrow B. The irradiation direction of the laser 81 is, for example, substantially parallel to the rake face 1. From another perspective, the irradiation direction of the laser 81 is, for example, substantially parallel to the first surface 41.

[0049] A laser processing area 82 is formed around the focus F of the laser 81. The laser processing area 82 is an area where the energy of the laser 81 is concentrated. The portion of the cutting tool 100 within the laser processing area 82 is removed. By scanning the laser 81, the diamond layer 5 constituting the rake face 1 is removed within a predetermined range. This makes it possible to sharpen the cutting edge 3. In other words, the radius of curvature R of the cutting edge 3 can be reduced.

[0050] When the direction of irradiation of the laser 81 is perpendicular to the rake face 1, most of the irradiated laser 81 hits the cutting tool 100. In this case, a large area of ​​the diamond layer 5 is heated due to irradiation with the laser 81. Therefore, the surface roughness of the diamond layer 5 is likely to deteriorate due to the heat generation. Specifically, for example, an oxidation reaction occurs in the heated diamond layer 5, which deteriorates the surface roughness of the diamond layer 5.

[0051] According to the method for manufacturing cutting tool 100 according to the first embodiment, the direction of irradiation of laser 81 is substantially parallel to rake face 1. As a result, part of laser 81 passes through focal point F without hitting cutting tool 100. This makes it possible to reduce the area of ​​diamond layer 5 that generates heat due to irradiation with laser 81. As a result, it is possible to suppress deterioration of the surface roughness of diamond layer 5. By suppressing deterioration of the surface roughness of diamond layer 5, it is possible to shorten the processing time in the step (S30) of smoothing the rake face using ion etching, which will be described later.

[0052] Next, a step (S30) of smoothing the rake face using ion etching is performed. Ion etching is performed so that each of the rake face 1 and the flank 2 is etched. The rake face 1 is smoothed. Specifically, the maximum height roughness of the first portion 16 is reduced. The processing time for the ion etching is set to, for example, 0.3 hours. By setting the processing time for the ion etching to about 0.3 hours, it is possible to prevent the thickness H (see FIG. 4) of the flank covering portion 52 from becoming excessively small. In this manner, the cutting tool 100 according to the first embodiment shown in FIGS. 1 to 4 is manufactured.

[0053] Second Embodiment <Configuration of Cutting Tool> Next, the configuration of a cutting tool 100 according to a second embodiment will be described. The cutting tool 100 according to the second embodiment differs from the cutting tool 100 according to the first embodiment mainly in that the rake face 1 has a first rake face portion 11 and a second rake face portion 12, but is substantially identical to the cutting tool 100 according to the first embodiment in other respects. The following description will focus on the differences from the cutting tool 100 according to the first embodiment.

[0054] Fig. 8 is a cross-sectional schematic diagram showing the configuration of a cutting tool 100 according to a second embodiment. The cross section shown in Fig. 8 corresponds to the cross section shown in Fig. 4. As shown in Fig. 8, the diamond layer 5 may cover the first surface 41 of the substrate 4. The portion of the diamond layer 5 covering the first surface 41 is defined as a rake face covering portion 51. From another perspective, the diamond layer 5 has a rake face covering portion 51 and a flank face covering portion 52.

[0055] The rake face 1 may have a first rake face portion 11 and a second rake face portion 12. The first rake face portion 11 is formed of, for example, a diamond layer 5. The first rake face portion 11 is spaced apart from the flank face 2. The first rake face portion 11 is substantially parallel to the first surface 41.

[0056] The second rake face portion 12 is provided between the first rake face portion 11 and the flank 2. The second rake face portion 12 is continuous with both the first rake face portion 11 and the flank 2. The ridge line between the second rake face portion 12 and the flank 2 forms the cutting edge 3.

[0057] The second rake face portion 12 is inclined relative to the first rake face portion 11 in a direction from the first rake face portion 11 toward the flank 2. Specifically, in a direction perpendicular to the rake face 1, the second rake face portion 12 is inclined in a direction from the first rake face portion 11 toward the flank 2. When the rake face 1 has the first rake face portion 11 and the second rake face portion 12, the direction perpendicular to the rake face 1 is defined as the direction perpendicular to the first rake face portion 11.

[0058] The inclination angle of the second rake face portion 12 relative to the first rake face portion 11 is set to a second angle θ2. In a cross section perpendicular to the tangent of the cutting edge 3, the second angle θ2 is the angle formed between an extension line 93 of the first rake face portion 11 and the second rake face portion 12. The second angle θ2 is, for example, 3° or greater and 50° or less. The second angle θ2 may be, for example, 3° or greater and 40° or less. The second angle θ2 may be, for example, 5° or greater, or 10° or greater. The second angle θ2 may be, for example, 35° or less, 30° or less, or 20° or less.

[0059] The second rake face portion 12 is composed of a first portion 16, a second portion 17, and a third portion 18. The first portion 16 is provided between the flank 2 and the second portion 17. The second portion 17 is a portion of the second rake face portion 12 that is formed by the base material 4. The second portion 17 is continuous with the first portion 16. The second portion 17 is spaced apart from the flank 2. The second portion 17 is provided between the first portion 16 and the third portion 18.

[0060] The third portion 18 is a portion of the second rake face portion 12 that is configured by the rake face covering portion 51. The third portion 18 is provided between the second portion 17 and the first rake face portion 11. The third portion 18 is continuous with both the second portion 17 and the first rake face portion 11. The third portion 18 is spaced apart from the first portion 16.

[0061] As shown in Figure 9, the width W of the second rake face portion 12 in a direction perpendicular to the tangent to the cutting edge 3 (see Figure 2) is, for example, 0.01 mm or more and 0.2 mm or less. In the base material 4, the second portion 17 is continuous with each of the first surface 41 and the second surface 42. The second portion 17 is provided between the first surface 41 and the second surface 42. The second portion 17 is inclined with respect to the first surface 41 in a direction from the first rake face portion 11 toward the flank surface 2. The second surface 42 is spaced apart from the first surface 41.

[0062] <Method for Manufacturing Cutting Tool> Next, a method for manufacturing a cutting tool 100 according to a second embodiment will be described. FIG. 9 is a cross-sectional schematic view illustrating a step (S20) of sharpening the cutting edge by laser processing the rake face in the method for manufacturing a cutting tool 100 according to the second embodiment. As shown in FIG. 9 , in the method for manufacturing a cutting tool 100 according to the second embodiment, the irradiation direction of the laser 81 (arrow B) is inclined with respect to the rake face 1. From another perspective, the irradiation direction of the laser 81 is inclined, for example, substantially with respect to the first surface 41. The inclination angle of the irradiation direction of the laser 81 with respect to the rake face 1 is the second angle θ2 (see FIG. 8 ). From another perspective, the irradiation direction of the laser 81 is substantially parallel to the second rake face portion 12 (see FIG. 8 ). As a result, the second rake face portion 12 is formed while reducing the radius of curvature R of the cutting edge 3.

[0063] <Usage> Next, usage of the cutting tool 100 according to the present disclosure will be described.

[0064] FIG. 10 is a partial cross-sectional schematic diagram showing a cutting tool 100 according to the present disclosure in use. As shown in FIG. 10 , a workpiece 90 is prepared. The workpiece 90 is made of, for example, a cemented carbide alloy. Specifically, the workpiece 90 is made of, for example, a cemented carbide alloy. The workpiece 90 may be made of, for example, ceramics such as alumina, silicon carbide, silicon, or CFRP (Carbon Fiber Reinforced Plastics). While the cutting tool 100 rotates about the axis X, the cutting edge 3 comes into contact with the workpiece 90. This cuts the workpiece 90.

[0065] Next, the effects of the cutting tool 100 according to the present disclosure will be described. For example, when the workpiece is made of a hard and brittle material such as cemented carbide, it is necessary to use the cutting tool to cut ceramic particles with high hardness. In this case, a cutting tool having a diamond layer with high hardness is typically used. When the cutting edge of a cutting tool is covered with a diamond layer, the thicker the diamond layer, the more rounded the cutting edge becomes. In this case, the sharpness of the cutting edge decreases, making the tool more susceptible to damage. On the other hand, if the diamond layer is too thin, the tool's wear resistance becomes excessively low. Even when a sufficient diamond layer thickness and high sharpness of the cutting edge are achieved by machining the diamond layer, chip adhesion to the cutting edge may occur due to the surface condition of the diamond layer. In this case, the formation of a built-up edge makes the tool more susceptible to damage. In particular, when the workpiece is made of cemented carbide, tungsten carbide particles contained in the cemented carbide are likely to adhere to the cutting edge. As described above, it has been difficult to improve the tool life of cutting tools with diamond layers.

[0066] According to the cutting tool 100 of the present disclosure, the diamond layer 5 has a flank coating portion 52. The flank coating portion 52 constitutes the flank 2. The rake face 1 has a first portion 16. The first portion 16 is constituted by the flank coating portion 52. The maximum height roughness of the first portion 16 is less than 2 μm. In this way, excessive protrusion of a portion of the first portion 16 is suppressed. When the cutting tool 100 is used to cut a workpiece 90, chips are likely to come into contact with the first portion 16. This makes it possible to suppress the occurrence of chip adhesion originating from an excessively protruding portion. As a result, the tool life can be improved.

[0067] According to the cutting tool 100 according to the present disclosure, the thickness of the flank covering portion 52 is 10 μm or more and 25 μm or less. When the thickness of the flank covering portion 52 is 10 μm or more, the wear resistance of the cutting tool 100 can be sufficiently improved.

[0068] According to the cutting tool 100 of the present disclosure, in a cross section perpendicular to the tangent line of the cutting edge 3, the radius of curvature R of the cutting edge 3 is less than the value obtained by multiplying the thickness of the flank covering portion 52 by 0.3. This sufficiently improves the sharpness of the cutting edge 3. As a result, damage to the tool can be made less likely to progress.

[0069] According to the cutting tool 100 according to the second embodiment, the rake face 1 has a first rake face portion 11 and a second rake face portion 12. The second rake face portion 12 is inclined relative to the first rake face portion 11 in a direction from the first rake face portion 11 toward the flank face 2. This increases the angle formed by the rake face 1 and the flank face 2. This improves the strength of the cutting edge 3.

[0070] According to the cutting tool 100 according to the second embodiment, the inclination angle (second angle θ2) of the second rake face portion 12 relative to the first rake face portion 11 is equal to or greater than 3° and equal to or less than 50°. When the second angle θ2 is equal to or greater than 3°, the angle formed between the second rake face portion 12 and the flank 2 can be prevented from becoming excessively small. This can prevent the strength of the cutting edge 3 from being excessively reduced. When the second angle θ2 is equal to or less than 50°, the angle formed between the second rake face portion 12 and the flank 2 can be prevented from becoming excessively large. This can prevent the sharpness of the cutting edge 3 from being excessively reduced.

[0071] According to the cutting tool 100 of the present disclosure, the substrate 4 is made of cemented carbide containing tungsten carbide particles. The average particle size of the tungsten carbide particles is 2 μm or less. As the average particle size of the tungsten carbide particles decreases, the adhesion between the substrate 4 and the diamond layer 5 improves. Therefore, by having the average particle size of the tungsten carbide particles be 2 μm or less, the adhesion between the substrate 4 and the diamond layer 5 can be improved. This can prevent the diamond layer 5 from peeling off from the substrate 4. As a result, the tool life can be further improved.

[0072] Although the cutting tool 100 is described above as being a ball end mill, the cutting tool 100 according to the present disclosure is not limited to a ball end mill. For example, the cutting tool 100 may be a radius end mill or the like. The cutting tool 100 may also be a turning tool such as a cutting insert.

[0073] (Sample Preparation) First, cutting tools 100 according to Samples 1 to 22 were prepared. Samples 1, 3, 4, 8 to 18, and 22 are examples. Samples 2, 5 to 7, and 19 to 21 are comparative examples. Cutting tools 100 according to Samples 1 to 22 were manufactured according to the above-described method for manufacturing cutting tools 100 according to the present disclosure. Specifically, cutting tools 100 were manufactured using the conditions shown in Table 1 below.

[0074]

[0075] Table 1 shows the manufacturing conditions and parameters of the cutting tool 100 for Samples 1 to 22. As shown in Table 1, the step (S20) of sharpening the cutting edge by laser processing the rake face was performed for Samples 1 to 18, 21, and 22. The irradiation direction of the laser 81 was parallel to the rake face 1 for Samples 1 to 7. The irradiation direction of the laser 81 was inclined with respect to the rake face 1 for Samples 8 to 18 and 22. From another perspective, the cutting tool 100 for Samples 8 to 18 and 22 had a second rake face portion 12. For Sample 21, the irradiation direction of the laser 81 was perpendicular to the rake face 1. For Samples 19 and 20, the step (S20) of sharpening the cutting edge by laser processing the rake face was not performed.

[0076] The ion etching treatment time in the step (S30) of smoothing the rake face by ion etching was set to 0.3 hours in Samples 1 to 6, 8 to 19, 21, and 22. In Samples 7 and 20, the step (S30) of smoothing the rake face by ion etching was not performed.

[0077] In Samples 1 to 7 and 19 to 21, the second angle θ2 was 0°. In other words, in Samples 1 to 7 and 19 to 21, the rake face 1 was flat (see FIG. 4). In Samples 8 to 18 and 22, the second angle θ2 was set to be equal to or greater than 3° and equal to or less than 55°. In other words, in Samples 8 to 18 and 22, the rake face 1 had a first rake face portion 11 and a second rake face portion 12 (see FIG. 7).

[0078] In the samples according to the example (Samples 1, 3, 4, 8 to 18, and 22), the thickness H was 10.1 μm or more and 24.8 μm or less. The value (R / H) obtained by dividing the radius of curvature R by the thickness H was 0.076 or more and 0.272 or less. In other words, the radius of curvature R was equal to or greater than the value obtained by multiplying the thickness H by 0.076 and equal to or less than the value obtained by multiplying the thickness H by 0.272. The Rz of the first portion 16 was 0.08 μm or more and 1.92 μm or less.

[0079] In Samples 2, 19, and 20, the value (R / H) obtained by dividing the radius of curvature R by the thickness H was 0.3 or more. In Sample 5, the thickness H of the flank covering portion 52 was less than 10 μm. In Sample 6, the thickness H was greater than 25 μm. In Samples 7 and 19 to 21, Rz of the first portion 16 was 2 μm or more.

[0080] In Samples 1 to 22, the average particle size of the tungsten carbide particles contained in the cemented carbide constituting the substrate 4 was 0.5 μm or more and 3 μm or less. In Samples 11 to 18, the average particle size of the tungsten carbide particles was 0.5 μm or more and 2 μm or less. In Samples 1 to 22, the first angle θ1 was 15° or more and 40° or less. In Samples 1 to 22, the radius of the tip portion 6 was 0.5 mm.

[0081] (Evaluation Method) Next, the tool life of the cutting tools 100 according to Samples 1 to 22 was evaluated. Specifically, the cutting tools 100 according to Samples 1 to 22 were used to drill a hemispherical hole having a diameter of 10 mm and a depth of 5 mm in a workpiece 90. The workpiece 90 was made of cemented carbide. In the machining, the rotation speed of the cutting tool 100 was 30,000 rpm. The table feed rate was 200 m / min. The depth of cut in a direction parallel to the axis X (axial depth of cut ap) was 0.04 mm. The depth of cut in a direction perpendicular to the axis X (radial depth of cut ae) was 0.2 mm. The volume (machined volume) of the workpiece 90 that the cutting tool 100 was able to cut before breaking was measured.

[0082] (Evaluation results)

[0083]

[0084] Table 2 shows the evaluation results for Samples 1 to 22. As shown in Table 2, in the samples according to the comparative examples (Samples 2, 5 to 7, and 19 to 21), the processed volume was 679.9 mm ３ In the samples according to the embodiment (samples 1, 3, 4, 8 to 18, and 22), the processed volume was 1046 mm ３ That was all.

[0085] From the above results, it was confirmed that the cutting tool 100 according to the example had an improved tool life compared to the cutting tool 100 according to the comparative example.

[0086] The embodiments and examples disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims, not by the above description, and is intended to include meanings equivalent to the claims and all modifications within the scope thereof.

[0087] 1 Rake face, 2 Flank face, 3 Cutting edge, 4 Base material, 5 Diamond layer, 6 Tip portion, 7 Body portion, 8 Shank portion, 11 First rake face portion, 12 Second rake face portion, 16 First portion, 17 Second portion, 18 Third portion, 41 First surface, 42 Second surface, 51 Rake face coated portion, 52 Flank coated portion, 58 Front end, 59 Rear end, 81 Laser, 82 Laser processing area, 90 Workpiece, 91 First virtual line, 92 Second virtual line, 100 Cutting tool, A, B Arrow, F Focus, H Thickness, R Radius of curvature, W Width, X Axis, θ1 First angle, θ2 Second angle.

Claims

1. A cutting tool comprising a substrate and a diamond layer covering the substrate, wherein the cutting tool includes a rake face and a flank face continuous with the rake face, a ridge line between the rake face and the flank face constitutes a cutting edge, the diamond layer has a flank face covering portion that constitutes the flank face, the thickness of the flank face covering portion is 10 μm or more and 25 μm or less, in a cross-section perpendicular to the tangent of the cutting edge, the radius of curvature of the cutting edge is less than a value obtained by multiplying the thickness of the flank face covering portion by 0.3, the rake face includes a first portion that is constituted by the flank face covering portion and is continuous with the flank face, and the maximum height roughness of the first portion is less than 2 μm.

2. The cutting tool according to claim 1, wherein the rake face has a first rake face portion spaced apart from the flank face, and a second rake face portion provided between the first rake face portion and the flank face and continuous with each of the first rake face portion and the flank face, and the second rake face portion is inclined with respect to the first rake face portion in a direction from the first rake face portion toward the flank face.

3. The cutting tool according to claim 2, wherein an inclination angle of the second rake face portion with respect to the first rake face portion is 3° or more and 50° or less.

4. The cutting tool according to any one of claims 1 to 3, wherein the thickness of the flank face covering portion is 15 μm or more and 20 μm or less.

5. The cutting tool according to any one of claims 1 to 4, wherein in a cross-section perpendicular to the tangent of the cutting edge, the radius of curvature of the cutting edge is less than a value obtained by multiplying the thickness of the flank face covering portion by 0.

1.

6. The cutting tool according to any one of claims 1 to 5, wherein the substrate is constituted by a cemented carbide containing tungsten carbide particles, and an average particle diameter of the tungsten carbide particles is 2 μm or less.

7. The cutting tool according to any one of claims 1 to 6, wherein a flank angle of the flank face is 15° or more and 35° or less.

8. The cutting tool according to any one of claims 1 to 7, wherein the maximum height roughness of the first portion is less than 1.5 μm.

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