cutting tools

Abstract

The cutting tool disclosed herein comprises a rake face, a flank face, and a cutting edge. The cutting edge is located between the rake face and the flank face. The cutting tool includes a substrate composed of a sintered cubic boron nitride body and an oxide layer covering the substrate and constituting a portion or all of at least one of the rake face, the flank face, and the cutting edge. The oxide layer contains at least one element selected from the group consisting of titanium, aluminum, zirconium, and cobalt. The oxide layer has a thickness of 2 μm or less.

Description

Technical Field

[0001] The present disclosure relates to a cutting tool. This application claims priority based on International Patent Application No. PCT / JP2020 / 024453 filed on June 22, 2020. The entire contents of the International Patent Application are incorporated herein by reference. Background Art

[0002] Japanese Patent Application Laid-Open No. 2017-159380 (Patent Document 1) describes an end mill having a plurality of grooves (concave portions) formed on a rake face.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2017-159380 Summary of the Invention

[0006] The cutting tool disclosed herein comprises a rake face, a flank face, and a cutting edge. The cutting edge is located between the rake face and the flank face. The cutting tool includes a substrate composed of a sintered cubic boron nitride body and an oxide layer covering the substrate and constituting a portion or all of at least one of the rake face, the flank face, and the cutting edge. The oxide layer contains at least one element selected from the group consisting of titanium, aluminum, zirconium, and cobalt. The oxide layer has a thickness of 2 μm or less. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 It is a schematic perspective view showing the structure of the cutting tool according to the first embodiment.

[0008] Figure 2 It is a side schematic diagram showing the structure of the cutting tool according to the first embodiment.

[0009] Figure 3 It is along Figure 2 Schematic cross-sectional view when observing along line III-III.

[0010] Figure 4 yes Figure 3 Schematic diagram of the enlarged area IV.

[0011] Figure 5 It is a top view schematically showing the structure of the cutting area.

[0012] Figure 6 It is a cross-sectional schematic diagram showing the structure of the cutting area.

[0013] Figure 7 It is an enlarged schematic cross-sectional view showing the structure of a first modified example of the cutting tool according to the first embodiment.

[0014] Figure 8 It is an enlarged cross-sectional schematic diagram showing the structure of a second modified example of the cutting tool according to the first embodiment.

[0015] Figure 9 This is a first schematic cross-sectional view showing the structure of a cutting tool according to the second embodiment.

[0016] Figure 10 This is a second schematic cross-sectional view showing the structure of the cutting tool according to the second embodiment.

[0017] Figure 11 It is a partial cross-sectional schematic diagram showing the structure of a cutting tool according to a third embodiment.

[0018] Figure 12 It is a partial cross-sectional schematic diagram showing the structure of a cutting tool according to a fourth embodiment.

[0019] Figure 13 This is a first schematic cross-sectional view showing the structure of a cutting tool according to a fifth embodiment.

[0020] Figure 14 This is a second schematic cross-sectional view showing the structure of the cutting tool according to the fifth embodiment.

[0021] Figure 15 Graph showing the relationship between the angle formed by two adjacent straight line portions and the position in the circumferential direction.

[0022] Figure 16 It is a partial cross-sectional schematic diagram showing the structure of a cutting tool according to a fifth embodiment.

[0023] Figure 17 It is a partial cross-sectional schematic diagram showing the structure of a cutting tool according to a sixth embodiment.

[0024] Figure 18 It is a partial cross-sectional schematic diagram showing the structure of a cutting tool according to a seventh embodiment.

[0025] Figure 19 It is a schematic cross-sectional view showing a state in which cutting processing is being performed using a cutting tool according to a fifth embodiment. DETAILED DESCRIPTION

[0026] [Problems to be Solved by the Present Disclosure]

[0027] When using a rotating cutting tool to cut a workpiece, centrifugal force acts on the coolant, making it difficult to effectively deliver the coolant to and retain it near the cutting point. The end mill described in Japanese Patent Application Publication No. 2017-159380 improves lubricity by retaining the coolant in the valley of a recessed portion provided on the rake face. However, this end mill, when subjected to high cutting resistance on the cutting edge, can experience stress concentration in the recessed portion, leading to damage and shortening the tool's lifespan.

[0028] [Effects of the Present Disclosure]

[0029] According to the present disclosure, the life of a cutting tool until the cutting edge is broken can be extended.

[0030] [Summary of Embodiments of the Present Disclosure]

[0031] First, an overview of the embodiments of the present disclosure will be described.

[0032] (1) A cutting tool 100 according to the present disclosure includes a rake face 4, a flank face 3, and a cutting edge 72. The cutting edge 72 is located between the rake face 4 and the flank face 3. The cutting tool 100 includes: a substrate 81 composed of a sintered cubic boron nitride; and an oxide layer 80 that covers the substrate 81 and constitutes a portion or all of at least one of the rake face 4, the flank face 3, and the cutting edge 72. The oxide layer 80 includes at least one element selected from the group consisting of titanium, aluminum, zirconium, and cobalt. The thickness of the oxide layer 80 is 2 μm or less.

[0033] (2) According to the cutting tool 100 according to (1) above, the thickness of the oxide layer 80 can be not less than 30 nm and not more than 300 nm.

[0034] (3) According to the cutting tool 100 involved in (1) or (2) above, when the area sandwiched by a first imaginary line 4b 200 μm away from an imaginary edge line D on the front cutting edge 4 and a second imaginary line 3b 200 μm away from the imaginary edge line D on the back cutting edge 3 is set as a cutting area 22, the proportion of the area occupied by the oxide layer 80 in the cutting area 22 can be greater than 20% and less than 80%, and the imaginary edge line D is a line formed by the intersection of the surface after the front cutting edge 4 is extended and the surface after the back cutting edge 3 is extended.

[0035] (4) According to the cutting tool 100 according to any one of (1) to (3) above, the substrate 81 may include the cubic boron nitride particles 23 and the bonding material 25 in contact with the cubic boron nitride particles 23. The oxide layer 80 may also be connected to the bonding material 25.

[0036] (5) According to the cutting tool 100 according to (4) above, a portion of the cubic boron nitride particles 23 may be exposed from the oxide layer 80 .

[0037] [Details of the embodiments of the present disclosure]

[0038] Hereinafter, the details of the embodiment of the present disclosure (hereinafter also referred to as the present embodiment) will be described based on the drawings. In addition, in the following drawings, the same or corresponding parts are marked with the same reference numerals, and their description will not be repeated.

[0039] (First embodiment)

[0040] Figure 1 It is a schematic perspective view showing the structure of a cutting tool 100 according to the first embodiment. Figure 2 1 is a side view schematically showing the structure of the cutting tool 100 according to the first embodiment. Figure 1 as well as Figure 2 As shown, the cutting tool 100 according to this embodiment is, for example, an end mill, and is composed of a blade 90, a joint 8, and a shank 7. The blade 90 has a first rake face 4, a first relief face 3, a second rake face 15, a second relief face 30, an outer peripheral cutting edge 72, a bottom cutting edge 21, and a front end 58. The shank 7 has a rear end 59. The blade 90 is fixed to the shank 7 via the joint 8. The joint 8 is made of brazing material and is located between the blade 90 and the shank 7.

[0041] The cutting tool 100 is configured to rotate about an axis A. From another perspective, the axis A is the rotation axis of the cutting tool 100. The material constituting the blade 90 includes, for example, a sintered cubic boron nitride (cBN). The shank 7 includes, for example, cemented carbide. Examples of cemented carbide include tungsten carbide (WC)-based cemented carbide, cemented carbide containing Co in addition to WC, and cemented carbide containing WC and carbonitrides such as Cr, Ti, Ta, and Nb.

[0042] The front end 58 of the cutting tool 100 is the portion that faces the workpiece. The rear end 59 of the cutting tool 100 is the portion that faces the tool that rotates the cutting tool 100. The shank 7 is the portion that is attached to the tool that rotates the cutting tool 100. The direction along the axis A is the axial direction. The direction perpendicular to the axial direction is the radial direction. In this specification, the direction from the front end 58 toward the rear end 59 is referred to as the axial rear direction. Conversely, the direction from the rear end 59 toward the front end 58 is referred to as the axial front direction.

[0043] like Figure 1 as well as Figure 2As shown, the first flank surface 3 is connected to the first rake surface 4. The ridge line between the first rake surface 4 and the first flank surface 3 can also constitute a peripheral cutting edge 72. The second rake surface 30 is connected to the second rake surface 15. The ridge line between the second rake surface 15 and the second rake surface 30 constitutes a bottom cutting edge 21. The first rake surface 4 is connected to the second rake surface 15. The first rake surface 4 is located axially rearward relative to the second rake surface 15. The first rake surface 3 is connected to the second rake surface 30. The first rake surface 3 is located axially rearward relative to the second rake surface 30.

[0044] A first chip flute 1 and a second chip flute 2 are formed on the blade portion 90 of the cutting tool 100. The first chip flute 1 is composed of a first rake face 4 and a first chip face 50. The second chip flute 2 is composed of a second rake face 15 and a second chip face 45. The second chip face 45 is connected to the first chip face 50. The first chip flute 1 is arranged in a spiral shape around the axis A. The second chip flute 2 is connected to the first chip flute 1. In the direction along the axis A, the length of the first chip flute 1 is longer than the length of the second chip flute 2.

[0045] The cutting tool 100 involved in this embodiment is, for example, a multi-blade rotary cutting tool 100. Specifically, the number of the peripheral cutting edges 72 is, for example, 2 or more. The lower limit of the number of the peripheral cutting edges 72 is not particularly limited, and for example, it can be 4 or more, or 8 or more. The upper limit of the number of the peripheral cutting edges 72 is not particularly limited, and for example, it can be 20 or less, or 16 or less. Figure 1 In the illustrated cutting tool 100 , the number of the peripheral cutting edges 72 is 5. The number of the bottom cutting edges 21 may be the same as the number of the peripheral cutting edges 72.

[0046] Figure 3 It is along Figure 2 Schematic cross-sectional view when observing along line III-III. Figure 3 The cross section shown is a cross section perpendicular to the axis. Figure 3 As shown, a plurality of first chip grooves 1 are arranged along the circumferential direction (rotation direction R). Similarly, a plurality of first flank faces 3 are arranged along the circumferential direction. Similarly, a plurality of peripheral cutting edges 72 are arranged along the circumferential direction. That is, when the combination of the first flank face 3, the first chip groove 1 and the peripheral cutting edge 72 is set as a cutting component, the plurality of cutting components are arranged along the circumferential direction. In this cutting component, the first chip groove 1 is located in front of the first flank face 3 in the rotation direction. In this cutting component, the first front cutting face 4 is located in front of the peripheral cutting edge 72 in the rotation direction. In this cutting component, the first chip surface 50 is located in front of the first front cutting face 4 in the rotation direction.

[0047] like Figure 3As shown, in the rotation direction R, the first flank surface 3 and the first chip discharge groove 1 are arranged alternately. One end of the first flank surface 3 can also constitute a peripheral cutting edge 72. The other end of the first flank surface 3 constitutes a tail portion 6. The first flank surface 3 can also be connected to the first rake surface 4 at the peripheral cutting edge 72. The first flank surface 3 is connected to the first chip discharge surface 50 at the tail portion 6. In the radial direction, the length from the axis A to the peripheral cutting edge 72 (first length L1) is longer than the length from the axis A to the tail portion 6 (second length L2).

[0048] Figure 4 yes Figure 3 An enlarged schematic diagram of region IV. Figure 4 As shown in FIG. 1 , the cutting tool 100 according to the first embodiment includes a cutting edge 72. The cutting edge 72 is located between the rake face 4 and the flank face 3. Figure 4 As shown, the cutting edge 72 may be arc-shaped and convex outward in a cross section perpendicular to the axis A. The cutting edge 72 may also be chamfered (honed). The cutting tool 100 includes a substrate 81. The substrate 81 is composed of a cubic boron nitride sintered body.

[0049] The cutting tool 100 has a cutting area 22. The cutting area 22 is an area sandwiched by a first imaginary line 4b 200 μm away from the imaginary edge line D on the front cutting surface 4 and a second imaginary line 3b 200 μm away from the imaginary edge line D on the back cutting surface 3. The imaginary edge line D is a line formed by the intersection of the surface after the front cutting surface 4 is extended (the second extended surface C2) and the surface after the back cutting surface 3 is extended (the first extended surface C1). Specifically, the cutting area 22 includes a first cutting area portion 4a, a second cutting area portion 3a and a cutting edge 72. The first cutting area portion 4a is located on the front cutting surface 4. The first cutting area portion 4a is connected to the cutting edge 72. The second cutting area portion 3a is located on the back cutting surface 3. The second cutting area portion 3a is connected to the cutting edge 72. The cutting edge 72 is an area sandwiched by the first cutting area portion 4a and the second cutting area portion 3a.

[0050] Figure 5 It is a schematic plan view showing the structure of the cutting area 22 . Figure 5 The schematic top view shown is a view observed in a direction perpendicular to the cutting area 22. Figure 5 As shown, substrate 81 includes cubic boron nitride particles 23 and a bonding material 25. The bonding material 25 is in contact with the cubic boron nitride particles 23. The bonding material 25 may be sandwiched between two adjacent cubic boron nitride particles 23. The bonding material 25 may also be provided to surround the cubic boron nitride particles 23. The bonding material 25 includes at least one of aluminum (Al), titanium (Ti), chromium (Cr), zirconium (Zr), cobalt (Co), and tungsten (W).

[0051] like Figure 5 As shown, the cutting tool 100 has an oxide layer 80. The oxide layer 80 is in contact with the substrate 81. The oxide layers 80 can also be set to be separated from each other. The bonding material 25 can also have a first bonding material portion 25a and a second bonding material portion 25b. When viewed from a direction perpendicular to the cutting area 22, the second bonding material portion 25b can also be surrounded by the oxide layer 80. The second bonding material portion 25b is in contact with the oxide layer 80. When viewed from a direction perpendicular to the cutting area 22, the first bonding material portion 25a can also be separated from the second bonding material portion 25b by the oxide layer 80. The first bonding material portion 25a can also be in contact with the oxide layer 80 and the cubic boron nitride particles 23 respectively. The second bonding material portion 25b can also be separated from the cubic boron nitride particles 23.

[0052] The ratio of the area occupied by the oxide layer 80 in the cutting region 22 is, for example, 20% or more and 80% or less. This ratio is the value obtained by dividing the total area of the oxide layer 80 present in the cutting region 22 by the area of the cutting region 22. The lower limit of the ratio of the area occupied by the oxide layer 80 in the cutting region 22 is not particularly limited and may be, for example, 25% or more, 30% or more, or 35% or more. The upper limit of the ratio of the area occupied by the oxide layer 80 in the cutting region 22 is not particularly limited and may be, for example, 75% or less, 70% or less, or 65% or less.

[0053] The proportion of the area occupied by the oxide layer 80 in the cutting region 22 is not particularly limited, and may be, for example, greater than 20% and less than 75%, greater than 20% and less than 70%, greater than 20% and less than 65%, greater than 25% and less than 80%, greater than 30% and less than 80%, greater than 35% and less than 80%, greater than 25% and less than 75%, greater than 25% and less than 70%, or greater than 30% and less than 75%.

[0054] Next, a method for measuring the proportion of the area occupied by the oxide layer 80 in the cutting area 22 is described. First, after cutting the area including the cutting area 22 by a FIB (Focused Ion Beam) device or a WEDM, a sample for observing a cross section in a direction perpendicular to the cutting edge ridge is prepared using a cross section polisher device or the like. Next, a scanning electron microscope (SEM) is used to observe multiple fields of view (approximately four fields of view) with a surface length of 150 μm or more within a range of 200 μm from the cutting edge ridge (the area in the rake face direction and the area in the flank face direction is 400 μm in total). The magnification of the SEM is 50,000 times. In the observed cross section, the proportion of blocks of an oxide layer having a thickness of 10 nm or more in the surface layer is taken as the area ratio of the oxide layer. EDS is used to determine whether the observed area is an oxide layer. The acceleration voltage is set to 5 kV. The area where 10 at% or more of oxygen is detected by K-rays or L-rays is determined to be an oxide layer.

[0055] Oxide layer 80 includes at least one element selected from the group consisting of titanium (Ti), aluminum (Al), zirconium (Zr), and cobalt (Co). Examples of oxide layer 80 include TiO, Al2O3, TiBNO, ZrO, AlBNO, CoO, or CoWBO. Oxide layer 80 may include two or more oxides. Specifically, oxide layer 80 may include oxide films of at least two of TiO, Al2O3, TiBNO, ZrO, AlBNO, CoO, and CoWBO. The type of oxide compound can be identified using a micro-X-ray diffraction (XRD) device or a transmission electron microscope (TEM).

[0056] The oxide layer 80 forms part of or all of at least any one of the rake face 4, the flank face 3, and the cutting edge 72. The oxide layer 80 may also form part of or all of the rake face 4. The oxide layer 80 may also form part of or all of the flank face 3. The oxide layer 80 may also form part of or all of the cutting edge 72. The oxide layer 80 may also form part of or all of the cutting region 22.

[0057] Figure 6 2 is a schematic cross-sectional view showing the structure of the cutting region 22 . Figure 6 The cross-sectional view shown is perpendicular to the axis A. Figure 6As shown, a portion of the oxide layer 80 is exposed in the cutting region 22. From another perspective, the oxide layer 80 constitutes a portion of the cutting region 22. The oxide layer 80 may also be connected to the bonding material 25. The oxide layer 80 may also be formed by oxidizing a portion of the elements constituting the bonding material 25. From another perspective, the oxide layer 80 may also include the elements included in the bonding material 25. The oxide layer 80 covers the substrate 81. The oxide layer 80 may also cover all or a portion of the cubic boron nitride particles 23. The oxide layer 80 may also cover all or a portion of the bonding material 25. The oxide layer 80 may also be in contact with the cubic boron nitride particles 23 in a manner that covers a portion of the cubic boron nitride particles 23. A portion of the cubic boron nitride particles 23 may also be exposed from the oxide layer 80.

[0058] like Figure 6 As shown, a portion of the cubic boron nitride particles 23 may also be exposed in the cutting region 22. From another perspective, the cubic boron nitride particles 23 may also constitute a portion of the cutting region 22. The bonding material 25 may also be located further inward than the oxide layer 80. A portion of the bonding material 25 may also be exposed in the cutting region 22. From another perspective, the bonding material 25 may also constitute a portion of the cutting region 22.

[0059] like Figure 6 As shown, the thickness T of the oxide layer 80 is, for example, 30 nm or more and 300 nm or less. The thickness T of the oxide layer 80 is the thickness in a direction perpendicular to the tangent line of the cutting region 22. The lower limit of the thickness T of the oxide layer 80 is not particularly limited and may be, for example, 45 nm or more, 60 nm or more, or 75 nm or more. The upper limit of the thickness T of the oxide layer 80 is not particularly limited and may be, for example, 275 nm or less, 250 nm or less, or 225 nm or less.

[0060] The thickness T of the oxide layer 80 is not particularly limited. For example, it can be greater than 30 nm and less than 275 nm, greater than 30 nm and less than 250 nm, greater than 30 nm and less than 225 nm, greater than 45 nm and less than 300 nm, greater than 60 nm and less than 300 nm, greater than 75 nm and less than 300 nm, greater than 45 nm and less than 275 nm, or greater than 60 nm and less than 250 nm.

[0061] Next, a method for measuring the thickness of the oxide layer 80 will be described. Figure 6As shown, the thickness T of the oxide layer 80 can be measured by observing the cross section of the cutting area 22 using an SEM. Specifically, after the area including the cutting area 22 is cut by a FIB device or WEDM, a cross-section polishing machine device is used to prepare a sample for observing the cross section in the direction perpendicular to the cutting edge ridge. Next, using an SEM, within a range of 200 μm from the cutting edge ridge (the area in the direction of the front cutting edge and the area in the direction of the back cutting edge is 400 μm in total), multiple fields of view (approximately four fields of view) are observed with a surface length of more than 150 μm. The magnification of the SEM is 50,000 times. In the observed cross section, a block of an oxide layer with a thickness of more than 10 nm is determined. The determined block is analyzed using image analysis software (WINROOF). Specifically, the thickness of the block is measured at intervals of 100 nm, and their average value is used as the thickness of the oxide layer 80.

[0062] Next, the method for forming oxide layer 80 will be described. Oxide layer 80 can also be formed by irradiating the surface of substrate 81 with laser light to oxidize a portion of the elements constituting bonding material 25. Specifically, the surface of substrate 81 where cutting region 22 is formed is irradiated with laser light. The laser light is, for example, a YAG laser. The wavelength of the laser light is, for example, 1064 nm. The output of the laser light is, for example, 5 W. The surface including cutting region 22 is irradiated with the laser light using a galvanometer scanner.

[0063] (First Modification)

[0064] Next, the structure of a first modified example of the cutting tool 100 according to the first embodiment will be described. Figure 7 It is an enlarged schematic cross-sectional view showing the structure of a first modified example of the cutting tool 100 according to the first embodiment. Figure 7 The schematic diagram shown is Figure 3 Corresponding to region IV. Figure 7 As shown, the cutting edge 72 of the cutting tool 100 may also be pointed. In this case, the imaginary ridgeline D coincides with the cutting edge 72. The first cutting region 4a is the region sandwiched between the cutting edge 72 and a first imaginary line 4b 200 μm away from the cutting edge 72 on the rake face 4. The second cutting region 3a is the region sandwiched between the cutting edge 72 and a second imaginary line 3b 200 μm away from the cutting edge 72 on the flank face 3.

[0065] (Second Modification)

[0066] Next, the structure of a second modified example of the cutting tool 100 according to the first embodiment will be described. Figure 8 It is an enlarged cross-sectional schematic diagram showing the structure of a second modified example of the cutting tool 100 according to the first embodiment. Figure 8 The schematic diagram shown is Figure 3 Corresponding to region IV. Figure 8 As shown, the cutting edge 72 of the cutting tool 100 may also have a flat negative land. The cutting edge 72 may also be inclined relative to both the rake face 4 and the flank face 3. The first cutting region 4a is the region bounded by the boundary between the cutting edge 72 and the rake face 4 and a first imaginary line 4b 200 μm away from the imaginary ridgeline D on the rake face 4. The second cutting region 3a is the region bounded by the boundary between the cutting edge 72 and the flank face 3 and a second imaginary line 3b 200 μm away from the imaginary ridgeline D on the flank face 3.

[0067] (Second embodiment)

[0068] Next, the structure of the cutting tool 100 according to the 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 primarily in that the oxide layer 80 covers the entire surface of the substrate 81. The remaining structures are the same as those of the cutting tool 100 according to the first embodiment. The following description will focus on the structures that differ from the cutting tool 100 according to the first embodiment.

[0069] Figure 9 This is a first schematic cross-sectional view showing the structure of a cutting tool 100 according to the second embodiment. Figure 9 The schematic diagram shown is Figure 3 Corresponding to region IV. Figure 9 As shown, in a cross section perpendicular to the axis A, the blade portion 90 of the cutting tool 100 according to the second embodiment has a base material 81 and an oxide layer 80. The oxide layer 80 has, for example, a first oxide film 91 and a second oxide film 92. The base material 81 has a first surface 10. The first surface 10 is opposite to the rake face 4. The first oxide film 91 has a second surface 56 and a third surface 55. The second surface 56 is in contact with the first surface 10. The third surface 55 is located on the opposite side of the second surface 56. The third surface 55 constitutes at least a portion of the rake face 4. In other words, the entire surface of the third surface 55 may be the rake face 4, or a portion of the third surface 55 may be the rake face 4.

[0070] The substrate 81 has a fifth surface 31. The fifth surface 31 is connected to the first surface 10. The fifth surface 31 is opposite to the flank surface 3. The boundary between the first surface 10 and the fifth surface 31 is the first ridge line 20. The second oxide film 92 constitutes at least a portion of the flank surface 3. The second oxide film 92 has a sixth surface 57 in contact with the fifth surface 31 and a seventh surface 93 opposite to the sixth surface 57. The seventh surface 93 constitutes at least a portion of the flank surface 3. In other words, the entire surface of the seventh surface 93 may be the flank surface 3, or a portion of the seventh surface 93 may be the flank surface 3.

[0071] like Figure 9 As shown, the first oxide film 91 may be connected to the second oxide film 92. The first oxide film 91 may be formed integrally with the second oxide film 92. The thickness of the second oxide film 92 may be smaller than that of the first oxide film 91.

[0072] The thickness of the first oxide film 91 (hereinafter also referred to as the first thickness) is, for example, 2 μm or less. The first thickness is the thickness of the first oxide film 91 in a direction perpendicular to the tangent line of the first rake face 4. The first thickness can be, for example, 1 μm or less, or 0.1 μm or less. The lower limit of the first thickness is not particularly limited, but can be, for example, 0.01 μm or more.

[0073] The thickness of the second oxide film 92 (hereinafter also referred to as the second thickness) is, for example, 2 μm or less. The second thickness is the thickness of the second oxide film 92 in a direction perpendicular to the tangent line of the first flank surface 3. The second thickness can be, for example, 1 μm or less, or 0.1 μm or less. The lower limit of the second thickness is not particularly limited, but can be, for example, 0.01 μm or greater.

[0074] (Observation method of oxide film)

[0075] Next, the observation method of the first oxide film 91 and the second oxide film 92 is described. First, the measurement sample is cut at a cross section perpendicular to the axis. The measurement sample is embedded in resin, and the cross section is processed with CP (Cross section polish). The composition of each of the first oxide film 91 and the second oxide film 92 can be determined, for example, using an energy dispersive X-ray analyzer (EDX) attached to a scanning electron microscope (SEM). As an SEM, for example, "JSM-7800F" manufactured by JEOL Ltd. can be used. As an EDX, for example, an Octane Elect EDS system can be used. The measurement magnification can be set to 5000 times, for example.

[0076] When the creepage distance from the peripheral cutting edge 72 to the tail portion 6 in the first chip flute 1 is defined as D1, the thickness of the first oxide film 91 is defined as the average of the thickness of the first oxide film 91 at a position 0.1×D1 away from the peripheral cutting edge 72 toward the tail portion 6, the thickness of the first oxide film 91 at a position 0.5×D1 away from the peripheral cutting edge 72 toward the tail portion 6, and the thickness of the first oxide film 91 at a position 0.9×D1 away from the peripheral cutting edge 72 toward the tail portion 6. When the creepage distance from the peripheral cutting edge 72 to the tail portion 6 in the first flank face 3 is defined as D2, the thickness of the second oxide film 92 is defined as the thickness of the second oxide film 92 at a position 0.5×D2 away from the peripheral cutting edge 72 toward the tail portion 6 (in other words, the center position of the first flank face 3).

[0077] Figure 10 This is a second schematic cross-sectional view showing the structure of the cutting tool 100 according to the second embodiment. Figure 10 The schematic diagram shown is Figure 3 The region V corresponds to Figure 10 As shown, the substrate 81 has an eighth surface 40. The eighth surface 40 is opposite to the first chip discharge surface 50. The eighth surface 40 is connected to the first surface 10 and the fifth surface 31, respectively. In the circumferential direction, the eighth surface 40 is located between the first surface 10 and the fifth surface 31. The boundary between the eighth surface 40 and the fifth surface 31 constitutes the second ridge line 5. The first oxide film 91 may also be in contact with the eighth surface 40. The first oxide film 91 may also be in contact with the second ridge line 5. The second oxide film 92 may also be in contact with the second ridge line 5. The first oxide film 91 may also be continuously provided from the first ridge line 20 to the second ridge line 5 in the first chip discharge groove 1. The second oxide film 92 may also be continuously provided from the first ridge line 20 to the second ridge line 5 on the first back face 3.

[0078] The first oxide film 91 may include at least one of aluminum, titanium, chromium, zirconium, cobalt, and tungsten. The first oxide film 91 may also be, for example, a coating film. The coating film may be formed, for example, by CVD (Chemical Vapor Deposition) or PVD (Physical Vapor Deposition).

[0079] The first oxide film 91 may be formed by irradiating the surface of the substrate 81 with laser light to oxidize a portion of the elements constituting the substrate 81. The first oxide film 91 may be an oxide of a portion of the elements constituting the substrate 81. Specifically, the first oxide film 91 may be an oxide of an element constituting the bonding material 25 contained in the substrate 81. For example, the first oxide film 91 may include Al2O3, TiO2, CoO, W2O3, or the like.

[0080] The second oxide film 92 may include at least one of aluminum, titanium, chromium, zirconium, cobalt, and tungsten. The second oxide film 92 may be, for example, a coating film. The coating film may be formed, for example, by CVD or PVD.

[0081] The second oxide film 92 may also be formed by irradiating the surface of the substrate 81 with laser light to oxidize a portion of the elements constituting the substrate 81. The second oxide film 92 may also be an oxide of a portion of the elements constituting the substrate 81. Specifically, the second oxide film 92 may also be an oxide of an element constituting the bonding material 25 contained in the substrate 81. The second oxide film 92 may contain, for example, Al2O3, TiO2, CoO, or W2O3.

[0082] (Third embodiment)

[0083] Next, the structure of the cutting tool 100 according to the third embodiment will be described. The cutting tool 100 according to the third embodiment differs from the cutting tool 100 according to the second embodiment in that it does not include the second oxide film 92. The remaining structures are the same as those of the cutting tool 100 according to the second embodiment. The following mainly describes the structures that differ from the cutting tool 100 according to the second embodiment.

[0084] Figure 11 It is a partial cross-sectional schematic diagram showing the structure of a cutting tool 100 according to the third embodiment. Figure 11 The area shown is Figure 3 Corresponding to region IV. Figure 11 As shown, the first oxide film 91 may also include a fourth surface 71 connecting the second surface 56 and the third surface 55. The fourth surface 71 of the first oxide film 91 is provided along the fifth surface 31 of the substrate 81. The ridge line between the third surface 55 and the fourth surface 71 constitutes the peripheral cutting edge 72. No oxide film is provided on the fifth surface 31. From another perspective, the fifth surface 31 of the substrate 81 is exposed from the first oxide film 91. The fourth surface 71 constitutes at least a portion of the first flank surface 3. The first flank surface 3 may also include the fourth surface 71 and the fifth surface 31.

[0085] (Fourth embodiment)

[0086] Next, the structure of the cutting tool 100 according to the fourth embodiment will be described. The cutting tool 100 according to the fourth embodiment differs from the cutting tool 100 according to the second embodiment in that the first oxide film 91 and the second oxide film 92 are separated. The remaining structures are the same as those of the cutting tool 100 according to the second embodiment. The following mainly describes the structures that differ from the cutting tool 100 according to the second embodiment.

[0087] Figure 12It is a partial cross-sectional schematic diagram showing the structure of a cutting tool 100 according to a fourth embodiment. Figure 12 The area shown is Figure 3 Corresponding to region IV. Figure 12 As shown, the first oxide film 91 may be separated from the second oxide film 92. A portion of the first surface 10 is exposed from the first oxide film 91. The first surface 10 includes a first region 18 in contact with the first oxide film 91 and a second region 17 connected to the first region 18 and separated from the first oxide film 91. The third surface 55 and the second region 17 constitute the rake face 4.

[0088] A portion of the fifth surface 31 is exposed from the second oxide film 92. The fifth surface 31 includes a third region 33 in contact with the second oxide film 92 and a fourth region 34 connected to the third region 33 and separated from the second oxide film 92. The seventh surface 93 and the fourth region 34 constitute the flank surface 3. The ridgeline between the second region 17 and the fourth region 34 constitutes the peripheral cutting edge 72. The second oxide film 92 may also include a portion whose thickness increases as it moves away from the peripheral cutting edge 72.

[0089] (Fifth embodiment)

[0090] Next, the structure of the cutting tool 100 according to the fifth embodiment will be described. The cutting tool 100 according to the fifth embodiment differs from the cutting tool 100 according to the second embodiment in that the first surface 10 of the substrate 81 is composed of a plurality of straight line portions. Otherwise, the cutting tool 100 is identical to the cutting tool 100 according to the second embodiment. The following description will focus on the structures that differ from the cutting tool 100 according to the second embodiment.

[0091] Figure 13 It is a first schematic cross-sectional view showing the structure of a cutting tool 100 according to the fifth embodiment. Figure 13 The area shown is Figure 3 Corresponding to region IV. Figure 13 In FIG, only the substrate 81 is shown, and the oxide film is not shown.

[0092] like Figure 13As shown, in a cross section perpendicular to the axis A, the first surface 10 is composed of a plurality of straight portions. The plurality of straight portions include, for example, a first straight portion 11, a second straight portion 12, a third straight portion 13, and a fourth straight portion 14. The first straight portion 11 is connected to the first flank surface 3. The first straight portion 11 is inclined relative to the fifth surface 31. The boundary between the first straight portion 11 and the fifth surface 31 is the first ridge line 20. The second straight portion 12 is inclined relative to the first straight portion 11. The second straight portion 12 is connected to the first straight portion 11. The second straight portion 12 is located on the opposite side of the fifth surface 31 relative to the first straight portion 11. From another perspective, the first straight portion 11 is located between the second straight portion 12 and the fifth surface 31.

[0093] Third straight portion 13 is inclined relative to second straight portion 12. Third straight portion 13 is connected to second straight portion 12. Third straight portion 13 is located on the opposite side of first straight portion 11 relative to second straight portion 12. From another perspective, second straight portion 12 is located between third straight portion 13 and first straight portion 11. Fourth straight portion 14 is inclined relative to third straight portion 13. Fourth straight portion 14 is connected to third straight portion 13. Fourth straight portion 14 is located on the opposite side of second straight portion 12 relative to third straight portion 13. From another perspective, third straight portion 13 is located between fourth straight portion 14 and second straight portion 12.

[0094] The angle formed by two adjacent straight line portions among the plurality of straight line portions may become smaller as they move away from the fifth surface 31. Specifically, the first angle θ1 formed by the first straight line portion 11 and the second straight line portion 12 may be greater than the second angle θ2 formed by the second straight line portion 12 and the third straight line portion 13. The second angle θ2 formed by the second straight line portion 12 and the third straight line portion 13 may be greater than the third angle θ3 formed by the third straight line portion 13 and the fourth straight line portion 14. The first angle θ1 is, for example, greater than or equal to 140° and less than or equal to 180°. The lower limit of the first angle θ1 is not particularly limited, and for example, it may be greater than or equal to 150°, or may be greater than or equal to 160°. The upper limit of the first angle θ1 is not particularly limited, and for example, it may be less than or equal to 178°, or may be less than or equal to 175°.

[0095] The boundary between the first straight portion 11 and the second straight portion 12 is the first position X1. The boundary between the second straight portion 12 and the third straight portion 13 is the second position X2. The boundary between the third straight portion 13 and the fourth straight portion 14 is the third position X3. The length of the first straight portion 11 (the linear distance between the outer peripheral cutting edge 72 and the first position X1) may be greater than the length of the second straight portion 12 (the linear distance between the first position X1 and the second position X2). The length of the second straight portion 12 (the linear distance between the first position X1 and the second position X2) may be greater than the length of the third straight portion 13 (the linear distance between the second position X2 and the third position X3).

[0096] In the rotational direction, the distance between the peripheral cutting edge 72 and the first position X1 (first distance a1) may be equal to the distance between the first position X1 and the second position X2 (second distance a2). In the rotational direction, the distance between the first position X1 and the second position X2 (second distance a2) may be equal to the distance between the second position X2 and the third position X3 (third distance a3).

[0097] Figure 14 This is a second schematic cross-sectional view showing the structure of the cutting tool 100 according to the fifth embodiment. Figure 14 The area shown is Figure 3 The area V corresponds to Figure 14 In FIG, only the substrate 81 is shown, and the oxide film is not shown.

[0098] like Figure 14 As shown, in a cross section perpendicular to axis A, eighth surface 40 may also be composed of multiple straight portions. For example, eighth surface 40 includes a fifth straight portion 41, a sixth straight portion 42, a seventh straight portion 43, and an eighth straight portion 44. Fifth straight portion 41 is inclined relative to fifth surface 31. Fifth straight portion 41 is connected to second ridgeline 5. Sixth straight portion 42 is inclined relative to fifth straight portion 41. Sixth straight portion 42 is connected to fifth straight portion 41. Sixth straight portion 42 is located on the opposite side of second ridgeline 5 relative to fifth straight portion 41. From another perspective, fifth straight portion 41 is located between sixth straight portion 42 and second ridgeline 5.

[0099] Seventh straight portion 43 is inclined relative to sixth straight portion 42. Seventh straight portion 43 is connected to sixth straight portion 42. Seventh straight portion 43 is located on the opposite side of fifth straight portion 41 relative to sixth straight portion 42. From another perspective, sixth straight portion 42 is located between seventh straight portion 43 and fifth straight portion 41. Eighth straight portion 44 is inclined relative to seventh straight portion 43. Eighth straight portion 44 is connected to seventh straight portion 43. Eighth straight portion 44 is located on the opposite side of sixth straight portion 42 relative to seventh straight portion 43. From another perspective, seventh straight portion 43 is located between eighth straight portion 44 and sixth straight portion 42.

[0100] A fourth angle θ formed by the fifth straight portion 41 and the sixth straight portion 42 n-1 It may be greater than the fifth angle θ formed by the sixth straight portion 42 and the seventh straight portion 43. n-2 The fifth angle θ formed by the sixth straight line portion 42 and the seventh straight line portion 43 is n-2 It may be greater than the sixth angle θ formed by the seventh straight portion 43 and the eighth straight portion 44. n-3 .

[0101] The boundary between the fifth straight portion 41 and the sixth straight portion 42 is the fourth position X n-1 The boundary between the sixth straight line portion 42 and the seventh straight line portion 43 is the fifth position X n-2 The boundary between the seventh straight line portion 43 and the eighth straight line portion 44 is the sixth position X n-3 The length of the fifth straight line portion 41 (the distance between the second ridge line 5 and the fourth position X n-1 The straight line distance between the fourth position X n-1 With the fifth position X n-2 The length of the sixth straight portion 42 (the fourth position X n-1 With the fifth position X n-2 The straight line distance between the fifth position X n-2 With the sixth position X n-3 straight-line distance between them).

[0102] In the rotation direction, the second edge line 5 and the fourth position X n-1 The distance between the fourth position X and the fourth position X (the fourth distance b1) can also be n-1 With the fifth position X n-2 The distance between them (fifth distance b2) is equal. In the rotation direction, the fourth position X n-1 With the fifth position X n-2 The distance between the fifth position X and the fifth position X (fifth distance b2) can also be n-2 With the sixth position X n-3 The distances between them (sixth distance b3) are equal.

[0103] Figure 15 : is a diagram showing the relationship between the angle formed by two adjacent straight line portions and the position in the circumferential direction. Figure 15 As shown, in the first surface 10, the angle formed by two adjacent straight portions may also decrease monotonically as the distance from the first ridge line 20 toward the eighth surface 40 is reached. In a cross section perpendicular to the axis A, the first surface 10 may, for example, be composed of five or more straight portions. Similarly, in the eighth surface 40, the angle formed by two adjacent straight portions may also decrease monotonically as the distance from the second ridge line 5 toward the first surface 10 is reached. In a cross section perpendicular to the axis A, the eighth surface 40 may, for example, be composed of five or more straight portions. In a cross section perpendicular to the axis A, the surface of the base material 81 opposite the first chip flute 1 may also be composed of multiple straight portions.

[0104] The lower limit of the number of straight line portions is not particularly limited, and may be, for example, 10 or more, or 20 or more. The upper limit of the number of straight line portions is not particularly limited, and may be, for example, 50 or less, or 40 or less.

[0105] like Figure 15 As shown, on the first surface 10, the difference between the maximum value of the angle formed by two adjacent straight line portions and the minimum value of the angle formed by two adjacent straight line portions (angle difference B) is, for example, 8° or greater. The lower limit of the angle difference B is not particularly limited and may be, for example, 10° or greater or 12° or greater. The upper limit of the angle difference B is not particularly limited and may be, for example, 30° or less.

[0106] Figure 16 It is a partial cross-sectional schematic diagram showing the structure of a cutting tool 100 according to a fifth embodiment. Figure 16 The area shown is Figure 3 corresponds to region IV.

[0107] like Figure 16 As shown, in a cross section perpendicular to the axis A, the cutting tool 100 according to the fourth embodiment includes a substrate 81, a first oxide film 91, and a second oxide film 92. The first surface 10 is opposed to the rake face 4. The first oxide film 91 includes a second surface 56 and a third surface 55. The second surface 56 is in contact with the first surface 10. The third surface 55 is located on the opposite side of the second surface 56. The third surface 55 is the rake face 4.

[0108] Substrate 81 has a fifth surface 31. Fifth surface 31 is connected to first surface 10. Fifth surface 31 is opposite to flank surface 3. Second oxide film 92 constitutes flank surface 3. Second oxide film 92 has a sixth surface 57 in contact with fifth surface 31 and a seventh surface 93 opposite to sixth surface 57. Seventh surface 93 is flank surface 3.

[0109] like Figure 16 As shown, in a cross section perpendicular to the axis A, the rake face 4 may also be composed of multiple straight line portions. The rake face 4 may also include a ninth straight line portion 51, a tenth straight line portion 52, an eleventh straight line portion 53, and a twelfth straight line portion 54. The ninth straight line portion 51 is opposite the first straight line portion 11. The tenth straight line portion 52 is opposite the second straight line portion 12. The eleventh straight line portion 53 is opposite the third straight line portion 13. The twelfth straight line portion 54 is opposite the fourth straight line portion 14.

[0110] The ninth straight portion 51 is connected to the first flank surface 3. The ninth straight portion 51 is inclined relative to the first flank surface 3. The boundary between the ninth straight portion 51 and the first flank surface 3 is the peripheral cutting edge 72. The tenth straight portion 52 is inclined relative to the ninth straight portion 51. The tenth straight portion 52 is connected to the ninth straight portion 51. The tenth straight portion 52 is located on the opposite side of the first flank surface 3 relative to the ninth straight portion 51. From another perspective, the ninth straight portion 51 is located between the tenth straight portion 52 and the first flank surface 3.

[0111] The eleventh straight portion 53 is inclined relative to the tenth straight portion 52. The eleventh straight portion 53 is connected to the tenth straight portion 52. The eleventh straight portion 53 is located on the opposite side of the ninth straight portion 51 relative to the tenth straight portion 52. From another perspective, the tenth straight portion 52 is located between the eleventh straight portion 53 and the ninth straight portion 51. The twelfth straight portion 54 is inclined relative to the eleventh straight portion 53. The twelfth straight portion 54 is connected to the eleventh straight portion 53. The twelfth straight portion 54 is located on the opposite side of the tenth straight portion 52 relative to the eleventh straight portion 53. From another perspective, the eleventh straight portion 53 is located between the twelfth straight portion 54 and the tenth straight portion 52.

[0112] (Sixth embodiment)

[0113] Next, the structure of the cutting tool 100 according to the sixth embodiment will be described. The cutting tool 100 according to the sixth embodiment differs from the cutting tool 100 according to the fifth embodiment in that it does not include the second oxide film 92. The remaining structures are the same as those of the cutting tool 100 according to the fifth embodiment. The following description will focus on the structures that differ from the cutting tool 100 according to the fifth embodiment.

[0114] Figure 17 It is a partial cross-sectional schematic diagram showing the structure of a cutting tool 100 according to the sixth embodiment. Figure 17 The area shown is Figure 3 Corresponding to region IV. Figure 17 As shown, the first oxide film 91 may further include a fourth surface 71 connecting the second surface 56 and the third surface 55. The fourth surface 71 of the first oxide film 91 is provided along the fifth surface 31 of the substrate 81. The ridge line between the third surface 55 and the fourth surface 71 constitutes the peripheral cutting edge 72. No oxide film is provided on the fifth surface 31. From another perspective, the fifth surface 31 of the substrate 81 is exposed from the first oxide film 91. The fourth surface 71 constitutes at least a portion of the first flank surface 3. The first flank surface 3 may also include the fourth surface 71 and the fifth surface 31.

[0115] (Seventh embodiment)

[0116] Next, the structure of the cutting tool 100 according to the seventh embodiment will be described. The cutting tool 100 according to the seventh embodiment differs from the cutting tool 100 according to the fifth embodiment in that the first oxide film 91 and the second oxide film 92 are separated. The remaining structures are the same as those of the cutting tool 100 according to the fifth embodiment. The following mainly describes the structures that differ from the cutting tool 100 according to the fifth embodiment.

[0117] Figure 18It is a partial cross-sectional schematic diagram showing the structure of a cutting tool 100 according to the seventh embodiment. Figure 18 The area shown is Figure 3 Corresponding to region IV. Figure 18 As shown, first oxide film 91 may be separated from second oxide film 92. A portion of first surface 10 is exposed from first oxide film 91. First surface 10 includes first region 18 in contact with first oxide film 91 and second region 17 connected to first region 18 and separated from first oxide film 91. Third surface 55 and second region 17 constitute rake face 4. Second region 17 may also be a portion of first straight portion 11.

[0118] A portion of fifth surface 31 is exposed from second oxide film 92. Fifth surface 31 includes a third region 33 in contact with second oxide film 92 and a fourth region 34 connected to third region 33 and separated from second oxide film 92. Second oxide film 92 includes a sixth surface 57 in contact with fifth surface 31 and a seventh surface 93 opposing sixth surface 57. Seventh surface 93 and fourth region 34 constitute flank surface 3. The ridgeline between second region 17 and fourth region 34 constitutes peripheral cutting edge 72. Second oxide film 92 may also include a portion whose thickness increases as it moves away from peripheral cutting edge 72.

[0119] In the above embodiment, the cutting tool 100 is, for example, a rotary cutting tool 100, more specifically, a multi-blade rotary cutting tool 100. The cutting tool 100 is, for example, an end mill, but is not limited to an end mill. The cutting tool 100 may also be, for example, a reamer, a drill, or a tap. The cutting tool 100 may also be a turning tool. The cutting tool 100 may also be a non-regrinding blade.

[0120] Next, the effects of the cutting tool 100 according to this embodiment will be described.

[0121] Figure 19 1 is a schematic cross-sectional view showing a state in which a cutting process is being performed using the cutting tool 100 according to the fifth embodiment. Figure 19 As shown, chips 61 of the workpiece 60 cut by the cutting edge 72 of the cutting tool 100 are discharged while in contact with the rake face 4. If the friction between the chips 61 and the rake face 4 is high, the chips 61 may be welded to the rake face 4. The welding of the chips 61 may cause the cutting edge 72 to break.

[0122] The cutting tool 100 disclosed herein includes a substrate 81 composed of a sintered cubic boron nitride body, and an oxide layer 80 covering the substrate 81 and constituting a portion or all of at least one of the rake face 4, the flank face 3, and the cutting edge 72. The oxide layer 80 contains at least one element selected from the group consisting of titanium, aluminum, zirconium, and cobalt. The thickness of the oxide layer 80 is 2 μm or less. This improves the wear resistance of the substrate 81, thereby extending the life of the cutting tool 100 until the cutting edge 72 is damaged.

[0123] According to the cutting tool 100 involved in the present disclosure, the thickness of the oxide layer 80 can be greater than 30 nm and less than 300 nm. When the thickness of the oxide layer 80 is too thin, the function of improving lubricity by utilizing the oxide layer 80 cannot be fully utilized, and the wear resistance of the cutting tool 100 is reduced. On the other hand, when the thickness of the oxide layer 80 is too thick, the oxide layer 80 is easily peeled off. When the oxide layer 80 is peeled off from the substrate 81, the cubic boron nitride sintered body is exposed, and thus the wear resistance of the cutting tool 100 is reduced. By making the thickness of the oxide layer 80 greater than 30 nm and less than 300 nm, the reduction in the wear resistance of the cutting tool 100 can be suppressed. Therefore, the life of the cutting tool 100 until the cutting edge 72 is damaged can be further extended.

[0124] According to the cutting tool 100 of the present disclosure, when the area sandwiched between a first imaginary line 4b 200 μm away from an imaginary ridgeline D on the rake face 4 and a second imaginary line 3b 200 μm away from the imaginary ridgeline D on the flank face 3 is defined as the cutting region 22, the area occupied by the oxide layer 80 can be between 20% and 80%. If the area occupied by the oxide layer 80 in the cutting region 22 is too small, the lubricity-enhancing function of the oxide layer 80 cannot be fully realized, and the wear resistance of the cutting tool 100 is reduced. On the other hand, if the area occupied by the oxide layer 80 in the cutting region 22 is too large, the tensile stress in the oxide layer 80 increases, causing the oxide layer 80 to collapse and become easily detached. When the oxide layer 80 peels from the substrate 81, the cubic boron nitride sintered body is exposed, thereby reducing the wear resistance of the cutting tool 100. By limiting the area ratio of the oxide layer 80 to 20% or more and 80% or less in the cutting region 22, it is possible to suppress the reduction in the wear resistance of the cutting tool 100. As a result, the life of the cutting tool 100 until the cutting edge 72 is damaged can be further extended.

[0125] In addition, according to the cutting tool 100 involved in the present disclosure, in a cross section perpendicular to the axis A, the first surface 10 of the substrate 81 may also be composed of multiple straight portions. Specifically, in a cross section perpendicular to the axis A, the first surface 10 may also have a first straight portion 11, a second straight portion 12 inclined relative to the first straight portion 11 and connected to the first straight portion 11, and a third straight portion 13 inclined relative to the second straight portion 12 and connected to the second straight portion 12. When the chip 61 moves on the rake face 4, the chip 61 curls with a certain curvature. Therefore, a gap 9 is formed between the curled chip 61, the ninth straight portion 51 opposite to the first straight portion 11, and the tenth straight portion 52 opposite to the second straight portion 12. Similarly, a gap 9 is formed between the curled chip 61, the tenth straight portion 52 opposite to the second straight portion 12, and the eleventh straight portion 53 opposite to the third straight portion 13. During cutting of the workpiece 60, coolant is drawn into the gap 9 by capillary action. This effectively delivers and retains the coolant near the cutting point. This reduces friction between the chips 61 and the rake face 4, thus preventing breakage of the cutting edge 72.

[0126] Example 1

[0127] (Sample Preparation)

[0128] First, cutting tools 100 of samples 1-1 to 1-12 were prepared. The cutting tools 100 of samples 1-1 to 1-12 were end mills. In the end mills, a substrate 81 was brazed to the front end of a shank made of cemented carbide. The substrate 81 was made of a cBN sintered body. In the cutting tools 100 of samples 1-1 to 1-11, an oxide layer 80 was formed in the cutting region 22 (see Figure 5 as well as Figure 6 The oxide layer 80 is TiO. In the cutting tool 100 of Sample 1-12, the oxide layer 80 is not formed in the cutting region 22 .

[0129] In the cutting tool 100 of Sample 1-1, the oxide layer 80 had a thickness of 0.015 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 30%. In the cutting tool 100 of Sample 1-2, the oxide layer 80 had a thickness of 0.03 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 48%. In the cutting tool 100 of Sample 1-3, the oxide layer 80 had a thickness of 0.06 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 50%. In the cutting tool 100 of Sample 1-4, the oxide layer 80 had a thickness of 0.1 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 56%. In the cutting tool 100 of Sample 1-5, the oxide layer 80 had a thickness of 0.25 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 64%. In the cutting tool 100 of Sample 1-6, the thickness of the oxide layer 80 was 0.3 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 68%.

[0130] In the cutting tool 100 of Sample 1-7, the oxide layer 80 had a thickness of 0.7 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 74%. In the cutting tool 100 of Sample 1-8, the oxide layer 80 had a thickness of 0.03 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 14%. In the cutting tool 100 of Sample 1-9, the oxide layer 80 had a thickness of 0.03 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 22%. In the cutting tool 100 of Sample 1-10, the oxide layer 80 had a thickness of 0.27 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 80%. In the cutting tool 100 of Sample 1-11, the oxide layer 80 had a thickness of 0.26 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 85%.

[0131] (Evaluation method)

[0132] Next, the cutting tools 100 of samples 1-1 to 1-12 were used to machine the workpiece 60. The workpiece 60 was SCM415. The cutting speed (Vc) was 300 mm / min. The feed rate (f) was 0.02 mm / edge. The lateral depth of cut (Ae) was 0.2 mm. The axial depth of cut (Ap) was 3.0 mm. The coolant was a 20-fold diluted emulsion.

[0133] (Evaluation Results)

[0134] Table 1

[0135]

[0136] Table 1 shows the chip life when the workpiece 60 was machined using the cutting tools 100 of samples 1-1 to 1-12. The chip life is the time from the start of machining to the chipping of the cutting edge 72. As shown in Table 1, the chip life when the workpiece 60 was machined using the cutting tools 100 of samples 1-1 to 1-11 was 34 minutes or more and 88 minutes or less. On the other hand, the chip life when the workpiece 60 was machined using the cutting tool 100 of sample 1-12 was 20 minutes. Based on the above results, it was confirmed that the chip life of the cutting edge 72 was prolonged by providing the oxide layer 80 in the cutting region 22.

[0137] The chip life when machining the workpiece 60 using the cutting tools 100 of Samples 1-2 to 1-6 was longer than the chip life when machining the workpiece 60 using the cutting tools 100 of Samples 1-1 and 1-7, respectively. The above results confirm that setting the thickness of the oxide layer 80 to 0.03 μm or more and 0.3 μm or less increases the chip life of the cutting edge 72.

[0138] The chip life when machining the workpiece 60 using the cutting tools 100 of Samples 1-2 and 1-9 was longer than the chip life when machining the workpiece 60 using the cutting tool 100 of Sample 1-8. The thickness of the oxide layer 80 in the cutting tools 100 of Samples 1-2, 1-8, and 1-9 was approximately the same. These results confirm that the chip life of the cutting edge 72 is prolonged by increasing the area occupied by the oxide layer 80 to 20% or more in the cutting region 22.

[0139] The chip life when machining the workpiece 60 using the cutting tools 100 of Samples 1-5 and 1-10 was longer than the chip life when machining the workpiece 60 using the cutting tool 100 of Sample 1-11. The thickness of the oxide layer 80 in the cutting tools 100 of Samples 1-5, 1-10, and 1-11 was approximately the same. These results confirm that the chip life of the cutting edge 72 is prolonged by reducing the area occupied by the oxide layer 80 to 80% or less in the cutting region 22.

[0140] Example 2

[0141] (Sample Preparation)

[0142] Next, cutting tools 100 of samples 2-1 to 2-12 were prepared. The cutting tools 100 of samples 2-1 to 2-12 were end mills. In the end mills, a substrate 81 was brazed to the front end of a shank made of cemented carbide. The substrate 81 was made of a cBN sintered body. In the cutting tools 100 of samples 2-1 to 2-11, an oxide layer 80 was formed in the cutting region 22 (see Figure 5 as well as Figure 6 The oxide layer 80 includes Al 2 O 3 , TiO, and TiBNO. In the cutting tool 100 of sample 2-12, the oxide layer 80 is not formed in the cutting region 22 .

[0143] In the cutting tool 100 of Sample 2-1, the oxide layer 80 had a thickness of 0.016 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 32%. In the cutting tool 100 of Sample 2-2, the oxide layer 80 had a thickness of 0.03 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 50%. In the cutting tool 100 of Sample 2-3, the oxide layer 80 had a thickness of 0.07 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 45%. In the cutting tool 100 of Sample 2-4, the oxide layer 80 had a thickness of 0.11 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 53%. In the cutting tool 100 of Sample 2-5, the oxide layer 80 had a thickness of 0.24 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 58%. In the cutting tool 100 of Sample 2-6, the thickness of the oxide layer 80 was 0.3 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 62%.

[0144] In the cutting tool 100 of Sample 2-7, the oxide layer 80 had a thickness of 0.6 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 72%. In the cutting tool 100 of Sample 2-8, the oxide layer 80 had a thickness of 0.03 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 15%. In the cutting tool 100 of Sample 2-9, the oxide layer 80 had a thickness of 0.03 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 21%. In the cutting tool 100 of Sample 2-10, the oxide layer 80 had a thickness of 0.25 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 78%. In the cutting tool 100 of Sample 2-11, the oxide layer 80 had a thickness of 0.25 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 85%.

[0145] (Evaluation method)

[0146] Next, the cutting tools 100 of samples 2-1 to 2-12 were used to machine the workpiece 60. The workpiece 60 was SCM416. The cutting speed (Vc) was 300 mm / min. The feed rate (f) was 0.02 mm / edge. The lateral depth of cut (Ae) was 0.2 mm. The axial depth of cut (Ap) was 3.0 mm. The coolant was a 20-fold diluted emulsion.

[0147] (Evaluation Results)

[0148] Table 2

[0149]

[0150] Table 2 shows the chip life when the workpiece 60 was machined using the cutting tools 100 of samples 2-1 to 2-12. The chip life is the time from the start of machining until the cutting edge 72 is chipped. As shown in Table 2, the chip life when the workpiece 60 was machined using the cutting tools 100 of samples 2-1 to 2-11 was 43 minutes or more and 105 minutes or less. On the other hand, the chip life when the workpiece 60 was machined using the cutting tool 100 of sample 2-12 was 24 minutes. The above results confirm that providing the oxide layer 80 in the cutting region 22 increases the chip life of the cutting edge 72.

[0151] The chip life when machining the workpiece 60 using the cutting tools 100 of Samples 2-2 to 2-6 was longer than the chip life when machining the workpiece 60 using the cutting tools 100 of Samples 2-1 and 2-7, respectively. The above results confirm that setting the thickness of the oxide layer 80 to 0.03 μm or more and 0.3 μm or less increases the chip life of the cutting edge 72.

[0152] The chip life when machining the workpiece 60 using the cutting tools 100 of Samples 2-2 and 2-9 was longer than the chip life when machining the workpiece 60 using the cutting tool 100 of Sample 2-8. The thickness of the oxide layer 80 in the cutting tools 100 of Samples 2-2, 2-8, and 2-9 was approximately the same. These results confirm that the chip life of the cutting edge 72 is prolonged by increasing the area occupied by the oxide layer 80 to 20% or more in the cutting region 22.

[0153] The chip life when machining the workpiece 60 using the cutting tools 100 of Samples 2-5 and 2-10 was longer than the chip life when machining the workpiece 60 using the cutting tool 100 of Sample 2-11. The thickness of the oxide layer 80 in the cutting tools 100 of Samples 2-5, 2-10, and 2-11 was approximately the same. These results confirm that the chip life of the cutting edge 72 is prolonged by reducing the area occupied by the oxide layer 80 to 80% or less in the cutting region 22.

[0154] Example 3

[0155] (Sample Preparation)

[0156] Next, cutting tools 100 of samples 3-1 to 3-12 were prepared. The cutting tools 100 of samples 3-1 to 3-12 were end mills. In the end mills, a substrate 81 was brazed to the front end of a shank made of cemented carbide. The substrate 81 was made of a cBN sintered body. In the cutting tools 100 of samples 3-1 to 3-11, an oxide layer 80 was formed in the cutting region 22 (see Figure 5 as well as Figure 6 The oxide layer 80 includes Al 2 O 3 , ZrO, and AlBNO. In the cutting tool 100 of Sample 3-12, the oxide layer 80 is not formed in the cutting region 22 .

[0157] In the cutting tool 100 of Sample 3-1, the oxide layer 80 had a thickness of 0.015 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 32%. In the cutting tool 100 of Sample 3-2, the oxide layer 80 had a thickness of 0.03 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 50%. In the cutting tool 100 of Sample 3-3, the oxide layer 80 had a thickness of 0.06 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 45%. In the cutting tool 100 of Sample 3-4, the oxide layer 80 had a thickness of 0.11 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 53%. In the cutting tool 100 of Sample 3-5, the oxide layer 80 had a thickness of 0.26 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 58%. In the cutting tool 100 of Sample 3-6, the thickness of the oxide layer 80 was 0.3 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 62%.

[0158] In the cutting tool 100 of Sample 3-7, the oxide layer 80 had a thickness of 0.5 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 72%. In the cutting tool 100 of Sample 3-8, the oxide layer 80 had a thickness of 0.03 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 16%. In the cutting tool 100 of Sample 3-9, the oxide layer 80 had a thickness of 0.03 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 22%. In the cutting tool 100 of Sample 3-10, the oxide layer 80 had a thickness of 0.27 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 78%. In the cutting tool 100 of Sample 3-11, the oxide layer 80 had a thickness of 0.25 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 85%.

[0159] (Evaluation method)

[0160] Next, the cutting tools 100 of samples 3-1 to 3-12 were used to machine the workpiece 60. The workpiece 60 was SCM415. The cutting speed (Vc) was 150 mm / min. The feed rate (f) was 0.03 mm / edge. The lateral depth of cut (Ae) was 0.2 mm. The axial depth of cut (Ap) was 3.0 mm. The coolant was a 20-fold diluted emulsion.

[0161] (Evaluation Results)

[0162] Table 3

[0163]

[0164] Table 3 shows the chip life when the workpiece 60 was machined using the cutting tools 100 of samples 3-1 to 3-12. The chip life is the time from the start of machining until the cutting edge 72 is chipped. As shown in Table 3, the chip life when the workpiece 60 was machined using the cutting tools 100 of samples 3-1 to 3-11 was 36 minutes or more and 98 minutes or less. On the other hand, the chip life when the workpiece 60 was machined using the cutting tool 100 of sample 3-12 was 17 minutes. The above results confirm that the chip life of the cutting edge 72 is prolonged by providing the oxide layer 80 in the cutting region 22.

[0165] The chip life when machining the workpiece 60 using the cutting tools 100 of Samples 3-2 to 3-6 was longer than the chip life when machining the workpiece 60 using the cutting tools 100 of Samples 3-1 and 3-7, respectively. These results confirm that setting the thickness of the oxide layer 80 to 0.03 μm or more and 0.3 μm or less increases the chip life of the cutting edge 72.

[0166] The chip life when machining the workpiece 60 using the cutting tools 100 of Samples 3-2 and 3-9 was longer than the chip life when machining the workpiece 60 using the cutting tool 100 of Sample 3-8. The thickness of the oxide layer 80 in the cutting tools 100 of Samples 3-2, 3-8, and 3-9 was approximately the same. These results confirm that the chip life of the cutting edge 72 is prolonged by increasing the area occupied by the oxide layer 80 to 20% or more in the cutting region 22.

[0167] The chip life when machining the workpiece 60 using the cutting tools 100 of Samples 3-5 and 3-10 was longer than the chip life when machining the workpiece 60 using the cutting tool 100 of Sample 3-11. The thickness of the oxide layer 80 in the cutting tools 100 of Samples 3-5, 3-10, and 3-11 was approximately the same. These results confirm that the chip life of the cutting edge 72 is prolonged by reducing the area occupied by the oxide layer 80 to 80% or less in the cutting region 22.

[0168] Example 4

[0169] (Sample Preparation)

[0170] Next, cutting tools 100 of samples 4-1 to 4-12 were prepared. The cutting tools 100 of samples 4-1 to 4-12 were end mills. In the end mills, a substrate 81 was brazed to the front end of a shank made of cemented carbide. The substrate 81 was made of a cBN sintered body. In the cutting tools 100 of samples 4-1 to 4-11, an oxide layer 80 was formed in the cutting region 22 (see Figure 5 as well as Figure 6 The oxide layer 80 includes CoO and CoWBO. In the cutting tool 100 of Sample 4-12, the oxide layer 80 is not formed in the cutting region 22.

[0171] In the cutting tool 100 of Sample 4-1, the oxide layer 80 had a thickness of 0.013 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 32%. In the cutting tool 100 of Sample 4-2, the oxide layer 80 had a thickness of 0.03 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 50%. In the cutting tool 100 of Sample 4-3, the oxide layer 80 had a thickness of 0.06 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 45%. In the cutting tool 100 of Sample 4-4, the oxide layer 80 had a thickness of 0.11 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 53%. In the cutting tool 100 of Sample 4-5, the oxide layer 80 had a thickness of 0.25 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 58%. In the cutting tool 100 of Sample 4-6, the thickness of the oxide layer 80 was 0.3 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 62%.

[0172] In the cutting tool 100 of Sample 4-7, the oxide layer 80 had a thickness of 0.5 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 72%. In the cutting tool 100 of Sample 4-8, the oxide layer 80 had a thickness of 0.03 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 16%. In the cutting tool 100 of Sample 4-9, the oxide layer 80 had a thickness of 0.03 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 22%. In the cutting tool 100 of Sample 4-10, the oxide layer 80 had a thickness of 0.26 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 78%. In the cutting tool 100 of Sample 4-11, the oxide layer 80 had a thickness of 0.26 μm, and the area ratio of the oxide layer 80 in the cutting region 22 was 85%.

[0173] (Evaluation method)

[0174] Next, the cutting tools 100 of samples 4-1 to 4-12 were used to machine the workpiece 60. The workpiece 60 was Ti-6Al-4V. The cutting speed (Vc) was 800 mm / min. The feed rate (f) was 0.02 mm / edge. The lateral depth of cut (Ae) was 0.2 mm. The axial depth of cut (Ap) was 0.5 mm. The coolant was a 20-fold diluted emulsion.

[0175] (Evaluation Results)

[0176] Table 4

[0177]

[0178] Table 4 shows the chip life when machining the workpiece 60 using the cutting tools 100 of samples 4-1 to 4-12. The chip life is the time from the start of machining until the cutting edge 72 is chipped. As shown in Table 4, the chip life when machining the workpiece 60 using the cutting tools 100 of samples 4-1 to 4-11 was 23 minutes or more and 70 minutes or less. On the other hand, the chip life when machining the workpiece 60 using the cutting tool 100 of sample 4-12 was 12 minutes. The above results confirm that providing the oxide layer 80 in the cutting region 22 increases the chip life of the cutting edge 72.

[0179] The chip life when machining the workpiece 60 using the cutting tools 100 of Samples 4-2 to 4-6 was longer than the chip life when machining the workpiece 60 using the cutting tools 100 of Samples 4-1 and 4-7, respectively. The above results confirm that setting the thickness of the oxide layer 80 to 0.03 μm or more and 0.3 μm or less increases the chip life of the cutting edge 72.

[0180] The chip life when machining the workpiece 60 using the cutting tools 100 of Samples 4-2 and 4-9 was longer than the chip life when machining the workpiece 60 using the cutting tool 100 of Sample 4-8. The thickness of the oxide layer 80 in the cutting tools 100 of Samples 4-2, 4-8, and 4-9 was approximately the same. These results confirm that the chip life of the cutting edge 72 is prolonged by increasing the area occupied by the oxide layer 80 to 20% or more in the cutting region 22.

[0181] The chip life when machining the workpiece 60 using the cutting tools 100 of Samples 4-5 and 4-10 was longer than the chip life when machining the workpiece 60 using the cutting tool 100 of Sample 4-11. The thickness of the oxide layer 80 in the cutting tools 100 of Samples 4-5, 4-10, and 4-11 was approximately the same. These results confirm that the chip life of the cutting edge 72 is prolonged by reducing the area occupied by the oxide layer 80 to 80% or less in the cutting region 22.

[0182] Example 5

[0183] (Sample Preparation)

[0184] First, cutting tools 100 of Samples 5-1 to 5-6 were prepared. Each of these cutting tools 100 had a substrate 81 brazed to the tip of a cemented carbide shank. The substrate 81 consisted of a cBN sintered body. In each of these cutting tools 100, an oxide film was formed on the substrate 81. In the case of Samples 5-1 to 5-5, no oxide film was formed on the substrate 81.

[0185] In the cutting tool 100 of sample 5-1, the thickness of the first oxide film 91 constituting the first rake face 4 is 5 μm. The thickness of the second oxide film 92 constituting the first flank face 3 is 8 μm. The first oxide film 91 and the second oxide film 92 are coated on the substrate 81 by PVD (see Figure 16 The first oxide film 91 and the second oxide film 92 are respectively a stacked structure of Al2O3 and TiO2.

[0186] In the cutting tool 100 of sample 5-2, the thickness of the first oxide film 91 constituting the first rake face 4 is 2 μm. The thickness of the second oxide film 92 constituting the first flank face 3 is 1 μm. The first oxide film 91 and the second oxide film 92 are formed by surface treating the substrate 81 with a laser to oxidize the elements contained in the substrate 81 (see Figure 16 ). The first oxide film 91 and the second oxide film 92 include Al2O3 and TiO2, respectively.

[0187] In the cutting tool 100 of sample 5-3, the thickness of the first oxide film 91 constituting the first rake face 4 is 2 μm. The thickness of the second oxide film 92 constituting the first flank face 3 is 0.5 μm. The first oxide film 91 and the second oxide film 92 are formed by surface treating the substrate 81 with a laser to oxidize the elements contained in the substrate 81 (see Figure 16 ). The first oxide film 91 and the second oxide film 92 contain Al 2 O 3 , TiO 2 , and CoO, respectively.

[0188] In the cutting tool 100 of sample 5-4, the thickness of the first oxide film 91 constituting the first rake face 4 is 2 μm. The thickness of the second oxide film 92 constituting the first flank face 3 is 0 μm. The first oxide film 91 is formed by oxidizing the elements contained in the substrate 81 by surface treatment with laser (refer to Figure 17 ). The first oxide film 91 contains Al2O3, TiO2 and CoO.

[0189] In the cutting tool 100 of sample 5-5, the thickness of the first oxide film 91 constituting the first rake face 4 is 2 μm. The thickness of the second oxide film 92 constituting the first flank face 3 is 0 μm. The first oxide film 91 is formed by oxidizing the elements contained in the base material 81 by surface treatment using laser light (see Figure 17 ). The first oxide film 91 contains TiO2, CoO, and W2O3.

[0190] (Evaluation method)

[0191] Next, the workpiece 60 was machined using the cutting tools 100 of samples 5-1 to 5-6 (see Figure 19 The workpiece 60 is Ti-6Al-4V. The cutting speed (Vc) is 500 mm / min. The feed rate (f) is 0.015 mm / edge. The lateral depth of cut (Ae) is 0.05 mm. The axial depth of cut (Ap) is 0.5 mm. The coolant is a 20-fold diluted emulsion.

[0192] (Evaluation Results)

[0193] Table 5

[0194]

[0195] Table 5 shows the defect life when the workpiece 60 was processed using the cutting tools 100 of samples 5-1 to 5-6. The defect life is the time from the start of processing to the time when the cutting edge 72 is defective. As shown in Table 5, the tool life when the workpiece 60 was processed using the cutting tools 100 of samples 5-1 to 5-5 was more than 18 minutes and less than 29 minutes. On the other hand, the tool life when the workpiece 60 was processed using the cutting tool 100 of sample 5-6 was 9 minutes. Based on the above results, it was confirmed that in the cross section perpendicular to the axis A, by forming the rake face 4 with the first oxide film 91, the defect of the cutting edge 72 can be suppressed.

[0196] The chip life when the workpiece 60 was machined using the cutting tools 100 of samples 5-2 to 5-5 was longer than the chip life when the workpiece 60 was machined using the cutting tool 100 of sample 5-1. The above results confirm that the chip life of the cutting edge 72 is prolonged by setting the thickness of the first oxide film to 2 μm or less.

[0197] (Note)

[0198] The above description includes the following additional features.

[0199] (Supplementary Note 1) The cutting tool 100 according to the present disclosure includes a rake face 4, a flank face 3, a substrate 81, and a first oxide film 91. The flank face 3 is connected to the rake face 4. The substrate 81 has a first surface 10 opposite the rake face 4. The first oxide film 91 has a second surface 56 in contact with the first surface 10 and a third surface 55 located on the opposite side of the second surface 56. The ridgeline between the rake face 4 and the flank face 3 constitutes a cutting edge 72. The third surface 55 constitutes at least a portion of the rake face 4.

[0200] (Supplementary Note 2) In the cutting tool 100 according to (Supplementary Note 1), the first oxide film 91 may further include a fourth surface 71 connecting the second surface 56 and the third surface 55. The fourth surface 71 may constitute at least a portion of the flank surface 3. The ridge line between the third surface 55 and the fourth surface 71 may constitute a cutting edge 72.

[0201] (Supplementary Note 3) In the cutting tool 100 according to (Supplementary Note 1) or (Supplementary Note 2), the first oxide film 91 may include at least one of aluminum, titanium, chromium, zirconium, cobalt, and tungsten.

[0202] (Supplementary Note 4) The cutting tool 100 according to (Supplementary Note 1) may further include a second oxide film 92 constituting at least a portion of the flank surface 3. The thickness of the second oxide film 92 may be smaller than that of the first oxide film 91.

[0203] (Supplementary Note 5) In the cutting tool 100 according to the above-mentioned (Supplementary Note 4), the first oxide film 91 and the second oxide film 92 may be connected.

[0204] (Supplementary Note 6) In the cutting tool 100 according to (Supplementary Note 4), the first oxide film 91 and the second oxide film 92 may be separated.

[0205] (Supplementary Note 7) In the cutting tool 100 according to any one of (Supplementary Note 4) to (Supplementary Note 6), the first oxide film 91 may include at least one of aluminum, titanium, chromium, zirconium, cobalt, and tungsten.

[0206] (Supplementary Note 8) In the cutting tool 100 according to any one of (Supplementary Note 4) to (Supplementary Note 7), the second oxide film 92 may include at least one of aluminum, titanium, chromium, zirconium, cobalt, and tungsten.

[0207] (Supplementary Note 9) In the cutting tool 100 according to any one of (Supplementary Note 1) to (Supplementary Note 8), the substrate 81 may include cubic boron nitride.

[0208] (Supplementary Note 10) In addition to the cutting tool 100 according to any one of the above (Supplementary Note 1) to (Supplementary Note 9), the cutting tool 100 may be a multi-blade rotary cutting tool 100.

[0209] The embodiments and examples disclosed herein are to be considered in all respects as illustrative and non-restrictive. The scope of the present invention is indicated by the claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0210] Description of Reference Numerals

[0211] 1: First chip flute; 2: Second chip flute; 3: Flank face (first flank face); 3a: Second cutting area; 3b: Second imaginary line; 4: Rake face (first rake face); 4a: First cutting area; 4b: First imaginary line; 5: Second ridgeline; 6: Tail; 7: Shank; 8: Joint; 9: Gap; 10: First surface; 11: First straight portion; 12: Second straight portion; 13: Third straight portion; 14: Fourth straight portion; 15: Second rake face; 17: Second area; 18: First area; 20: First ridgeline; 21: Bottom cutting edge; 22: Cutting area; 23: Cubic boron nitride particles; 25: Bonding material; 25a: First bonding material portion; 25b: Second bonding material portion; 30: Second flank face; 31: Fifth surface; 33: Third area; 34: Fourth area; 40: Eighth surface; 41: Fifth straight portion Line portion; 42: Sixth straight portion; 43: Seventh straight portion; 44: Eighth straight portion; 45: Second chip removal surface; 50: First chip removal surface; 51: Ninth straight portion; 52: Tenth straight portion; 53: Eleventh straight portion; 54: Twelfth straight portion; 55: Third surface; 56: Second surface; 57: Sixth surface; 58: Front end; 59: Rear end; 60: Workpiece; 61: Chips; 71: Fourth surface; 72: Cutting edge (peripheral cutting edge); 80: Oxide layer; 81: Base material; 90: Blade portion; 91: First oxide film; 92: Second oxide film; 93: Seventh surface; 100: Cutting tool; A: Axis; B: Angle difference; C1: First extension surface; C2: Second extension surface; D: Imaginary edge line; L1: First length; L2: Second length; R: Rotation direction; X1: First position; X2: Second position; X3: Third position; X4: Second position n-1 : Fourth position; X n-2 : Fifth position; X n-3 : sixth position; a1: first distance; a2: second distance; a3: third distance; b1: fourth distance; b2: fifth distance; b3: sixth distance; θ1: first angle; θ2: second angle; θ3: third angle; θ n-1 : The fourth angle; θ n-2 : The fifth angle; θn-3 : The sixth angle.

Claims

1. A cutting tool, The cutting tool comprises: Rake face; Flank surface; and a cutting edge located between the rake face and the flank face, in, The cutting tool includes: a substrate composed of a cubic boron nitride sintered body; and an oxide layer covering the substrate and constituting a portion or all of at least any one of the rake face, the flank face, and the cutting edge. The oxide layer contains at least one element selected from the group consisting of titanium, aluminum, zirconium and cobalt, The thickness of the oxide layer is less than 2 μm, The substrate comprises cubic boron nitride particles and a bonding material in contact with the cubic boron nitride particles. The oxide layer is connected to the bonding material, The oxide layer contains the elements contained in the bonding material, When a region sandwiched between a first imaginary line 200 μm away from an imaginary ridgeline on the rake face and a second imaginary line 200 μm away from the imaginary ridgeline on the flank face is defined as a cutting region, The area ratio of the oxide layer in the cutting region is 20% or more and 80% or less, The virtual ridgeline is a line formed by the intersection of a surface obtained by extending the rake face and a surface obtained by extending the flank face.

2. The cutting tool according to claim 1, wherein The thickness of the oxide layer is greater than or equal to 30 nm and less than or equal to 300 nm.

3. The cutting tool according to claim 2, wherein The thickness of the oxide layer is greater than or equal to 60 nm and less than or equal to 250 nm.

4. The cutting tool according to claim 1, wherein A portion of the oxide layer is exposed in the cutting region.

5. The cutting tool according to claim 1, wherein A portion of the cubic boron nitride particles is exposed from the oxide layer.

6. The cutting tool according to any one of claims 1 to 3, wherein In a cross section perpendicular to an axis serving as a rotation axis of the cutting tool, the cutting edge has an arc shape convex outward.

7. The cutting tool according to any one of claims 1 to 3, wherein The oxide layer includes two or more oxides selected from the group consisting of TiO, Al2O3, TiBNO, ZrO, AlBNO, CoO, and CoWBO.

8. The cutting tool according to any one of claims 1 to 3, wherein The oxide layer constitutes a part or the entirety of the rake face.

9. The cutting tool according to any one of claims 1 to 3, wherein The oxide layer constitutes a part or the entirety of the flank surface.

10. The cutting tool according to any one of claims 1 to 3, wherein The oxide layer constitutes a part or the entirety of the cutting edge.

11. The cutting tool according to any one of claims 1 to 3, wherein The oxide layer covers the entire surface of the substrate.

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