Cutting tool

Abstract

A cutting tool (1; 101) comprising: a base element (10; 110), a diamond layer (11; 111) arranged on the base element (10; 110), and a first surface (8; 108), a second surface (9; 109) and a cutting edge (4, 5; 105) which is arranged at least in part of a ridge line at which the first surface (8; 108) intersects the second surface (9; 109), wherein the diamond layer (11; 111) is arranged in at least a part of the first surface (8; 108), at least a part of the second surface (9; 109) and at least a part of the cutting edge (4, 5; 105) and a maximum height in the cutting edge (4, 5; 105) is smaller than a maximum height in the first surface (8; 108) and the maximum height in the cutting edge (4, 5; 105) is greater than a maximum height in the second surface (9; 109), wherein in the cutting edge (4, 5; 105) the maximum height is 0.3 to 0.7 µm and an arithmetic mean roughness is 0.06 to 0.1 µm, in the first surface (8; 108) the maximum height is 0.8 to 1.4 µm and an arithmetic mean roughness is 0.1 to 0.25 µm and in the second surface (9; 109) the maximum height is 0.1 to 0.5 µm and an arithmetic mean roughness is 0.04 to 0.08 µm, wherein the cutting edge (4, 5; 105) has a convex-curved surface shape in a cross-section orthogonal to the ridge line, and the cutting edge (4, 5; 105) has a plurality of grooves (13) in a direction which intersects the ridge line, and wherein the plurality of grooves (13) are orthogonal to the ridge line.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a cutting tool having a diamond layer on a base member. BACKGROUND

[0002] A cutting tool comprising a diamond layer deposited on a surface of a base member is known. For example, JP 2002-187793 A discloses a method of smoothing the surface of a diamond layer by a so-called metal bombardment treatment, which requires that positive ions generated in a target collide with the surface of the diamond layer.

[0003] For example, from DE 694 32 642 T2 a cutting tool is known, comprising: a base element, a diamond layer arranged on the base element, and a first surface, a second surface and a cutting edge arranged at least in part of a ridge line at which the first surface intersects the second surface, wherein the diamond layer is arranged in at least part of the first surface, at least part of the second surface and at least part of the cutting edge.

[0004] Other cutting tools with a diamond coating are known from, for example, US 6 161 990 A, DE 10 2013 218 446 A1, US 2015 / 0 117 972 A1 and US 2006 / 0 115 650 A1.

[0005] In addition, a cutting tool with a coating is known from, for example, US 2007 / 0 253 787 A1, the roughness of which is adjusted in the area of ​​the cutting edge.

[0006] Furthermore, a cutting tool is known from US 5 085 542 A, in the cutting edge of which grooves are provided. SHORT DESCRIPTION

[0007] The present invention provides a cutting tool having the features according to claim 1. Further embodiments of the cutting tool are described in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a side view showing a cutting tool in a first embodiment, Fig. 2 is an enlarged view of a side of a first end P of the cutting tool of the Fig. 1, Fig. 3 is a sectional view along the line XX of the Fig. 2, Fig. 4 is an SEM image when the cutting tool of the Fig. 3 viewed from a Y-direction, Fig. 5 is an SEM image when the cutting tool of the Fig.4 viewed from a Z1 direction, Fig. 6 is a SEM image when the cutting tool of the Fig. 4 viewed from a Z2 direction, Fig. 7 is a SEM image when the cutting tool of the Fig. 4 viewed from a Z3 direction, Fig. Figure 8 is an SEM image magnifying an area W of the Fig. 7 represents, Fig. Fig. 9 is a perspective view showing a cutting tool in a second embodiment, Fig. 10 is a perspective view of a cutting insert of the cutting tool of the Fig. 9, Fig. 11 is a sectional view along the line UU of the Fig. 10 and Fig. Fig. 12 is a schematic diagram for explaining a deposition process for a diamond layer of the cutting tool of the Fig. 1. EMBODIMENTS

[0008] Recently, reduction of chatter vibration in an early stage of a cutting process, good chip discharge performance and further smoothness of a finished surface are required for cutting tools.

[0009] The Fig. Figure 1 is a side view of a cutting tool 1 in a first embodiment. This embodiment shows a solid-type end mill as one embodiment of the cutting tools. Examples of the cutting tools include drills and reamers in addition to the end mill.

[0010] The cutting tool 1, which is in the Fig.1, has a rotation axis O and a rod shape extending from a first end P to a second end Q. The cutting tool 1 has a cutting edge part 2, which is arranged on one side of the first end P, and a shank part 3, which is arranged on one side of the second end Q. As shown in the Fig. 1 and Fig. 2, the cutting edge part 2 has a second cutting edge 4 (end cutting edge) which is arranged on one side of the first end P, a first cutting edge 5 (edge ​​cutting edge) which extends from an outer edge end of the second cutting edge 4 towards the second end Q, a first groove 6, at least a part of which is arranged along the first cutting edge 5, and a notch 7 which is arranged between the second cutting edge 2 and the first groove 6. The Fig.Fig. 2 is a partial enlarged view of a side of the first end P in the cutting tool 1 (a left side in the Fig. 1). In the present embodiment, the first end P is arranged at an end portion on one side of the cutting edge part 2 in the cutting tool 1, and the second end Q is arranged at an end portion on one side of the shank part 3 in the cutting tool 1.

[0011] As it is in the Fig.1, the cutting tool 1 in the present embodiment has the first groove 6, an outer peripheral surface, and a ridge line along which the first groove 6 intersects the outer peripheral surface. In particular, the first groove 6 has a first surface 8 (outer peripheral rake surface) arranged along the ridge line, and the outer peripheral surface has a second surface 9 (outer peripheral flank surface) arranged along the ridge line. In other words, the first cutting edge 5 is arranged in at least a part of the ridge line at which the first surface 8 intersects the second surface 9, as shown in FIG. Fig.3. It can also be said that the first surface 8 has a rake face region, and the second surface 9 has a flank surface region. The first groove 6 can be used as a space through which chips generated by the first cutting edge 5 can pass.

[0012] The cutting tool 1 also comprises a base element 10 and a diamond layer 11 arranged on the base element 10, as shown in the Fig. 3. Although the Fig. 3 shows an embodiment in which the diamond layer 11 is in contact with the base member 10, a layer other than the diamond layer 11 may be arranged between the base member 10 and the diamond layer 11.

[0013] In the present embodiment, the diamond layer 11 is disposed in at least a part of the first surface 8, at least a part of the second surface 9, and at least a part of the first cutting edge 5. Durability of each of the first surface 8, the second surface 9, and the first cutting edge 5 can be improved because the diamond layer 11 is disposed in the above-mentioned areas. In particular, when the diamond layer 11 is disposed over the entirety of the first surface 8, the second surface 9, and the first cutting edge 5, the durability of the first surface 8, the second surface 9, and the first cutting edge 5 can be further improved.

[0014] In the cutting tool 1 of the present embodiment, a maximum height Rz (hereinafter referred to as "Rye" for identification) in a part of the first cutting edge 5 on which the diamond layer 11 is arranged is smaller than a maximum height Rz (hereinafter referred to as "Ryr" for identification) in a part of the first surface 8 on which the diamond layer 11 is arranged.

[0015] The maximum height Rye in the part of the first cutting edge 5 where the diamond layer 11 is disposed is greater than a maximum height Rz (hereinafter referred to as "Ryf" for identification) in a part of the second surface 9 where the diamond layer 11 is disposed. That is, a relationship of Ryf < Rye < Ryr is achieved.

[0016] Since Ryf < Rye, a surface of the diamond layer 11 in the second surface 9 is smoother than a surface of the diamond layer 11 in the first cutting edge 5. This leads to improved roughness of the finished surface of a workpiece. Since Rye < Ryr, a surface of the diamond layer 11 in the first surface 8 is rougher than a surface of the diamond layer 11 in the first cutting edge 5. Therefore, when chips come into contact with the first surface 8, the chips tend to deform or change at the first surface 8. Consequently, the chips are less likely to extend excessively, resulting in improved chip discharge performance.

[0017] In addition, the first cutting edge 5 is less likely to come into excessive contact with the workpiece because the first cutting edge 5 is smoother than the first surface 8. The first cutting edge 5 is less likely to come into flat contact with the workpiece, and cutting resistance is reducible at the beginning of a cutting operation because the first cutting edge 5 is rougher than the second surface 9. Consequently, chatter vibration is less likely to occur at the first cutting edge 5.

[0018] The Fig. 4 to 7 each show, by means of scanning electron microscope (SEM) images, a surface state of the diamond layer 11 under the conditions that Ryf < Rye < Ryr is achieved in the cutting tool 1 of the present embodiment. Fig. 4 is an SEM image of the first cutting edge 5. The Fig.5 to 7 are SEM images taken in the direction of the arrow Z1 to Z3 in the Fig. 4. The second surface 9 is smoother than the first surface 8, as is the case, for example, in the Fig. 7 is shown.

[0019] Hereinafter, an arithmetic mean roughness in the first cutting edge 5 is denoted as "Rae," an arithmetic mean roughness in the surface 8 is denoted as "Rar," and an arithmetic mean roughness in the second surface 9 is denoted as "Raf." Chatter vibration is less likely to occur at the beginning of the cutting process, and chip discharge performance is further improved, and surface roughness of a finished surface becomes better and smoother when the cutting tool 1 satisfies the following conditions.

[0020] Specifically, the excellent cutting tool 1 described above can be obtained when Rye is 0.3-0.7 µm, Rae is 0.06-0.1 µm, Ryr is 0.8-1.4 µm, Rar is 0.1-0.25 µm, Ryf is 0.1-0.5 µm, and Raf is 0.04-0.08 µm. The maximum heights Rye, Ryr, and Ryf and the arithmetic mean roughness values ​​Rae, Rar, and Raf must be calculated based on methods for measuring a maximum height Rz and an arithmetic mean roughness value Ra in accordance with JIS B0601'2001.

[0021] Hereinafter, an SP3 ratio is a ratio (SP3 / SP2) obtained from an SP3 peak derived from diamond crystals measurable by Raman spectrum analysis and an SP2 peak derived from a graphite phase. When an SP3 ratio in the first cutting edge 5 is larger than an SP3 ratio in each of the first surface 8 and the second surface 9, a proportion of diamond crystals 12 in the first cutting edge 5 is large. This improves the hardness of the diamond layer 11, resulting in a cutting tool 1 having excellent wear resistance.

[0022] In each of the first surface 8 and the second surface 9, the proportion of diamond crystals 12 is low, and the proportion of a graphite phase with low hardness is high. Therefore, a surface condition can be adapted to the shape of a workpiece during a cutting process, thereby improving chip discharge efficiency and also smoothing the roughness of the finished surface.

[0023] The SP3 ratio is also measurable in the surface of the diamond layer 11, or alternatively, is measurable in a cross-section of the diamond layer 11. One of these two measurement types must be selected to compare an SP3 ratio in the first cutting edge 5 and an SP3 ratio in each of the first surface 8 and the second surface 9. When the SP3 ratio is measured in the cross-section of the diamond layer 11, and as a result, an SP3 ratio at an interface position in a thickness range up to 1 µm from an interface between the base member 10 and the diamond layer 11 in a direction toward the diamond layer 11 is larger than an SP3 ratio at a thickness mid-position of the diamond layer 11, adhesion between the base member 10 and the diamond layer 11 can be improved, and fracture resistance of the diamond layer 11 can also be improved.

[0024] If a contour of each of the diamond crystals 12 is perceptible, for example as in the Fig. 8, when viewing the first cutting edge 5 at magnifications of 10,000-30,000, the protrusions of the diamond crystals 12, which have strong eigenform characteristics, are smoothed. Therefore, the diamond layer 11 is less likely to excessively contact a workpiece at the first cutting edge 5. The reason for this is as follows. While the contour of each of the diamond crystals 12 is noticeable, the protrusions of the diamond crystals 12, which have strong eigenform characteristics and protrude from the surface of the diamond layer 11, are smoothed, resulting in a state in which traces due to the eigenform of the diamond crystals 12 are invisible.

[0025] In the present embodiment, the term "mode shape" refers to maintaining a crystal structure inherent to diamond, and the term "mode shape characteristics" is an index indicating a measure of similarity to the crystal structure inherent to diamond.

[0026] Examples of diamond crystals include diamond crystals with a micro-size (microcrystals) and diamond crystals with a nano-size (nanocrystals). In particular, the micro-size diamond crystals are capable of further improving the hardness of the diamond layer 11.

[0027] If a large amount of polishing residue remains after a polishing process performed to form the first cutting edge 5, the large amount of polishing residue may enter a grain boundary between the diamond crystals 12. It is therefore difficult to perceive the grain boundary, which serves as a contour of the diamond crystals 12, in other words, no diamond crystals 12 are perceptible. In contrast, little or no polishing residue remains in an embodiment shown in the Fig. 8, since the contours of the diamond crystals 12 are perceptible in the first cutting edge 5. In a state in which little or no polishing residue remains, a machining surface is less likely to be damaged by the polishing residue during a cutting operation. Fig. Fig. 8 is an SEM photograph of a key part of the first cutting edge 5 in the Fig.7, which is magnified at a magnification of 25,000. The Fig. 8 shows an embodiment in which the diamond crystal 12 is identified. If the grain boundary, which serves as the contour of the diamond crystals 12, cannot be identified in the SEM image in which the first cutting edge 5 is magnified at a magnification of 25,000, it is necessary to observe an SEM image in which the first cutting edge 5 is magnified at a magnification of 30,000.

[0028] In cases where the diamond crystals 12 cannot be identified when the first surface 8 is viewed at the same magnification as the viewing magnification of the first cutting edge 5, chips are less likely to be twisted because the chips tend to deform or change on the first surface 8.

[0029] Although an average particle diameter of the diamond crystals 12, when the first cutting edge 5 as in the Fig. 8 is not limited to a specific value, the average particle diameter can be set to, for example, 0.5-3 µm. The diamond layer 11 is less likely to come into excessive contact with the workpiece at the first cutting edge 5 when the average particle diameter of the diamond crystals 12 is within the above range.

[0030] The average particle diameter of the diamond crystals 12 can be evaluated as follows. Areas of the individual diamond crystals 12 surrounded by the contour are identified, and an average value of these areas is converted into a circle. The average particle diameter of the diamond crystals 12 can be evaluated as a diameter of the circle. When measuring the areas, the measurement is performed on the diamond crystals 12 that are visible on the image, but the diamond crystals 12, some of which extend beyond the image, are excluded from the measurement object.

[0031] The first ridge line, where the first cutting edge 5 is located, has a line shape macroscopically, but it is not required to have a precise line shape. The ridge line where the first surface 8 intersects the second surface 9 may have a curved surface shape microscopically. When the ridge line has the curved surface shape, the first cutting edge 5 is less prone to breakage, resulting in improved durability of the first cutting edge 5. The first cutting edge, which has the curved surface shape microscopically, must be manufactured by applying a chamfering process or a honing process to the ridge line.

[0032] The Fig. Figure 4 shows an embodiment in which the first cutting edge 5 has a curved surface shape. The first cutting edge 5, which in the Fig.4, has a convex-curved surface shape in a cross-section orthogonal to the ridge line. The first cutting edge 5, which is in the Fig. 4, also has a plurality of second grooves 13 extending in a direction intersecting the ridge line, as shown in the Fig. 5 to 7.

[0033] As is evident from the fact that for the first cutting edge 5 in the Fig.4 is easily perceived to have the curved surface shape, it is not necessarily required to evaluate in a cross-section whether the first cutting edge 5 has the convex-curved surface shape. The shape of the first cutting edge 5 in a direction orthogonal to the ridge line can be evaluated using, for example, a contact-type surface roughness measuring instrument using a probe or a non-contact-type surface roughness measuring instrument using lasers.

[0034] When the first cutting edge 5 has the second grooves 13, it is possible to reduce the contact area of ​​the first cutting edge 5 with respect to a workpiece at the beginning of the cutting process. This results in reduced cutting resistance, and chatter vibration is less likely to occur at the first cutting edge 5.

[0035] When the first cutting edge 5 has the second grooves 13, it becomes easier to guide a chip flow direction in an extension direction of the plurality of second grooves 13. That is, it becomes easier to control the chip flow direction. Therefore, chips are less likely to be trapped, resulting in improved chip discharge performance.

[0036] In particular, when the plurality of second grooves 13 are orthogonal to the ridge line, it is possible to further improve chip discharge performance. The term "orthogonal" means that the extension direction of the second grooves 13 and an extension direction of the ridge line do not necessarily have to form exactly 90°. In cases where the angle formed by the extension direction of the second grooves 13 and the extension direction of the ridge line is in a range of approximately 80-100°, the plurality of second grooves 13 are considered orthogonal to the ridge line.

[0037] For example, in embodiments described in the Fig. 5 and Fig.6, the ridge line along which the first cutting edge 5 is arranged extends in a left-right direction, whereas a plurality of the second grooves 13 each extend vertically. Accordingly, the majority of the second grooves 13 are orthogonal to the ridge line.

[0038] When, in a front view of the first surface 8, a length L1 of each of the second grooves 13 in a direction orthogonal to the ridge line is larger than a width W1 of each of the second grooves 13 in a direction along the ridge line, the chip flow direction can be more easily controlled by the second grooves 13, thereby further improving the chip discharge performance.

[0039] When a length L1 of each of the second grooves 13 in the direction orthogonal to the ridge line in the front view of the first surface 8 is longer than a length L2 of each of the second grooves 13 in the direction orthogonal to the ridge line in the front view of the second surface 9, the chip discharge performance can be further improved and the surface roughness of a finished surface can be further improved. The reason for this is as follows. The chip flow direction can be more easily controlled because the length L1 of each of the second grooves 13 in the front view of the first surface 8 is relatively long, and each of the second grooves 13 is less likely to contact the finished surface because the length L2 of each of the second grooves 13 in the front view of the second surface 9 is relatively short.

[0040] The configuration of the first cutting edge 5, which is arranged along the ridge line along which the first surface 8 intersects the second surface 9, has been described above. The second cutting edge 4 may have a similar configuration to that of the first cutting edge 5. In particular, when the second cutting edge 4 is arranged in at least a part of a ridge line at which the third surface having the rake face region intersects the fourth surface having the flank region, the diamond layer 11 may be arranged in at least a part of the third surface, at least a part of the fourth surface, and at least a part of the second cutting edge 4. A maximum height Rz in a portion of the second cutting edge 4 at which the diamond layer 11 is arranged may be smaller than a maximum height Rz in a portion of the third surface at which the diamond layer 11 is arranged.The maximum height Rz in the portion of the second cutting edge 4 at which the diamond layer 11 is arranged may be greater than a maximum height Rz at a portion of the fourth surface at which the diamond layer 11 is arranged.

[0041] In cases where the third surface, the fourth surface, and the second cutting edge 4 have the above configurations, chatter vibration is less likely to occur at the beginning of the cutting process, chip discharge performance can be further improved, and the surface roughness of a finished surface can be better and smoother.

[0042] As a material of the base member 10, it is possible to use hard materials such as cemented carbide, cermet, silicon nitride, alumina, and cubic boron nitride. In particular, when the material of the base member 10 is cemented carbide, the cutting tool 1 has excellent fracture resistance.

[0043] The adhesion between the base member 10 and the diamond layer 11 is high when the interface roughness between the base member 10 and the diamond layer 11 is 0.12-0.8 µm. The interface roughness can be obtained as follows. While observing a cross-sectional SEM image showing the interface between the base member 10 and the diamond layer 11, the interface is identified by tracing the interface between the base member 10 and the diamond layer 11 in the image. An arithmetic mean roughness Ra at the identified interface is calculated in accordance with JIS B0601 2001. The arithmetic mean roughness Ra is evaluated as the interface roughness.

[0044] An outer peripheral surface having the second surface 9 in the cutting tool 1 can be smoothed by a polishing process such as a brushing process and a blasting process.

[0045] When a thickness of the diamond layer 11 in the first cutting edge 5, which is arranged on a side of the first end P in the cutting tool 1, particularly in a region from the first end P of the cutting tool 1 in a direction along the rotation axis O to a position 5 mm away therefrom, is greater than a thickness of the diamond layer 11 at a position 10 mm from the first end P of the cutting tool 1 in a direction toward the second end Q, the diamond layer 11 is less likely to be worn away at the first cutting edge 5, and a smoothness of the surface of the diamond layer 11 in the first surface 8 can be easily maintained. A ratio (t z / tx ) a layer thickness tx the diamond layer 11 in the first cutting edge 5, which is arranged in the area starting from the first end P in the direction along the rotation axis O to the position 5 mm away therefrom, and a layer thickness t z of the diamond layer 11, which is arranged at the position 10 mm from the first end P of the cutting tool 1 in the direction of the second end Q, is preferably in a range of 0.5-0.9, more preferably 0.6-0.8. A preferred range of the layer thickness t x is 5-12 µm.

[0046] When a thickness of the diamond layer 11 in the first surface 8 is smaller than a thickness of the diamond layer 11 in the first cutting edge 5, excessive cutting resistance is less likely to act at the beginning of the cutting process.

[0047] If a ratio (t g / t x ) of the layer thickness t xthe diamond layer 11 in the first cutting edge 5 and a layer thickness t g of the diamond layer 11 in the first surface 8 is 0.6-0.9, the diamond layer 11 is less likely to be worn away in the first cutting edge 5, and smoothness of the diamond layer 11 in the first surface 8 can be maintained.

[0048] A thickness of the diamond layer 11 in the first cutting edge 5 denotes a thickness of the diamond layer 11 in a direction along a bisector of the first surface 8 and the second surface 9 in the sectional view shown in the Fig. 3. A thickness of the diamond layer 11 in the first surface 8 refers to a thickness of the diamond layer 11 in a portion of the first surface 8 which is closest to a deepest portion of the first groove 6.

[0049] The deepest portion of the first groove 6 denotes a position which is arranged at a shortest distance from the rotation axis O. A diameter “d” of a circle passing through the position which is arranged at the shortest distance around the rotation axis O, namely a maximum inscribed circle “c”, which can be drawn inside the cutting tool 1 in the sectional view, as shown in the Fig. 3 is a web thickness.

[0050] A cutting tool 101 of a second embodiment is described below. The following description mainly focuses on differences between the cutting tool 101 of the second embodiment and the cutting tool 1 of the first embodiment, and descriptions of configurations similar to the cutting tool 1 of the first embodiment are omitted.

[0051] As it is in the Fig.9, the present embodiment shows an indexable end mill as one embodiment of cutting tools. The cutting tool 101 (end mill) of the present embodiment has a rotation axis O and comprises a rod-shaped holder 32 extending from a first end P to a second end Q, and a cutting insert (hereinafter referred to as an "insert") 34 arranged at a predetermined location on one side of the first end P in / on the holder. The embodiment shown in Fig. 9, comprises, as the insert, a first insert 34a for an inner cutting edge and a second insert 34b for an outer cutting edge. The second insert 34b is arranged at a location farther from the rotation axis than the first insert 34a.

[0052] The first insert 34a and the second insert 34b may be different in shape, or alternatively may have the same shape. The first insert 34a and the second insert 34b have the same shape in the embodiment, which in the Fig. 9. Therefore, the first insert 34a and the second insert 34b are collectively referred to herein as the insert 34.

[0053] As it is in the Fig. 10, the insert 34 has a first surface 108 (an upper surface in the Fig. 10), which has a chip surface area, a second surface 109 (a side surface in the Fig.10), which has a flank surface area, and a cutting edge 105 arranged in at least part of a ridge line at which the first surface 108 intersects the second surface 109. The insert 34 has a through hole 36 open in a central part of the first surface 108. The through hole 36 is used, for example, when a screw is inserted to fix the insert 34 to the holder 32.

[0054] As it is in the Fig. 11, which is a sectional view along the line UU of the Fig. 10, the insert 34 comprises the base element 110 and a diamond layer 111 disposed on the base element 110. Here, the diamond layer 111 is disposed in at least a portion of the first surface 108, at least a portion of the second surface 109, and at least a portion of the cutting edge 105.

[0055] In the insert 34 in the present embodiment, a maximum height Rye in a portion of the cutting edge 105 at which the diamond layer 111 is arranged is smaller than a maximum height Ryr in a portion of the first surface 108 at which the diamond layer 111 is arranged.

[0056] The maximum height Rye in the portion of the cutting edge 105 where the diamond layer 111 is disposed is greater than a maximum height Ryf in a portion of the second surface 109 where the diamond layer 111 is disposed. That is, a relationship of Ryf < Rye < Ryr is achieved as in the case of the cutting tool 1 of the first embodiment.

[0057] Therefore, the cutting edge 105 is less likely to make flat contact with a workpiece at the beginning of a cutting operation. Consequently, cutting resistance can be reduced, and chatter vibration is less likely to occur in the cutting edge 105. Furthermore, when chips come into contact with the first surface 108, the chips tend to deform or change on the first surface 108, and the chips are less likely to extend excessively, resulting in improved clamping output performance. It is also possible to improve the roughness of the finished surface of the workpiece. Manufacturing process

[0058] A method of manufacturing the above cutting tool 1 is described below. The following manufacturing method is one of embodiments of methods of manufacturing the cutting tool 1. Therefore, the cutting tool 1 is not limited to one manufactured by the following manufacturing method.

[0059] First, a centerless process is performed on a surface of a first member formed of a hard material such as cemented carbide, cermet, silicon nitride, alumina, and cubic boron nitride. Subsequently, a columnar second member is manufactured by applying a sharpening process to the first member. If desired, a polishing process may be performed on a portion of the second member that serves as a flank area. A base member 10 before depositing a diamond layer 11 thereon can be obtained by performing an etching process including an acid treatment and an alkali treatment in this order.

[0060] During the alkali treatment, a main crystal phase of the semi-material exposed on a surface of the base member 10 can be roughened by pouring an alkaline solution containing an aqueous alkaline solution and abrasive diamond grains into an ultrasonic washing tank and applying ultrasound thereto. The etched base member 10 is washed with water and then dried. Here, a state of an SP3 ratio in the diamond layer 11 is adjustable depending on the ultrasonic power applied during the ultrasonic washing, controlling a particle diameter of the abrasive diamond grains, and the alkali treatment time.

[0061] Subsequently, the diamond layer 11 is deposited on the surface of the base member 10. A hot wire CVD method is suitably applicable as a method of depositing the diamond layer 11. One of the embodiments of the deposition method is described with reference to Fig. 12. A depositing device 50, which is shown in the Fig. 12, has a chamber 51. The chamber 51 has therein a sample stand 53 which is designed to have the samples (the etched base members 10) placed thereon. In the present embodiments, each of the rod-shaped base members 10 is placed on the sample stand 53 in an upright state, specifically in a direction in which a cutting edge part 2 is arranged on an upper side and a shank part 3 is arranged on a lower side. A first cutting edge 5 and a first groove 6, which form the cutting edge part 2, are shown in the Fig. 12 omitted.

[0062] Heaters 54, such as wires, are arranged around the base elements 10. The heaters 54 are each connected to power sources 55 located outside the chamber 41. The temperature of each of the base elements 10, which sit on the sample stand 53, can be adjusted to 850-930 °C by adjusting the arrangement positions of the heaters 54 and by adjusting the current value supplied to each of the heaters 54. The heaters 54 are each supported by a support body 58.

[0063] The chamber 51 has a gas supply inlet 56 and a gas outlet 57. The diamond layer 11 can be deposited by supplying hydrogen gas and methane gas from the gas supply inlet 56 into the evacuated chamber 51 and spraying these gases onto each of the base elements 10.

[0064] Specific deposition conditions for the diamond layer 11 are described below. The mixing ratio of a gas mixture introduced during deposition is controlled. Specifically, the mixing ratio (volume %) of methane is controlled when the diamond layer 11 is deposited, so that the mixing ratio is large in an initial phase and subsequently decreases. This allows the SP3 ratio in the diamond layer 11 to be controlled.

[0065] After the diamond layer 11 is deposited, a gas bombardment treatment is performed using the deposition device 50 under conditions of a bias voltage of 200-600 V, more suitably 250-450 V, a gas pressure of 2.5-4.5 Pa, and a treatment time of 15-45 minutes. This allows the maximum height of the diamond layer 11 in each of a first surface 8, a second surface 9, and a first cutting edge 5 to be controlled within a predetermined range. EXAMPLES

[0066] A 10 wt% amount of metallic cobalt (Co) powder, a 0.2 wt% amount of titanium carbide (TiC) powder, and a 0.8 wt% amount of chromium carbide (Cr3C2) powder were added to a tungsten carbide (WC) powder having an average particle diameter of 0.5 µm. These were mixed together and formed into a columnar shape, followed by sintering. This was then subjected to a centerless machining and sharpening process, thereby forming a first member having an end mill shape. Acid treatment and alkali treatment were performed on the first member. Subsequently, a base member (6 mm diameter, 10 mm cutting edge length, 3 mm land thickness, two flutes) was prepared by washing, with distilled water, a surface of a second member as a precursor to a base member.During the alkali treatment, an aqueous alkaline solution containing abrasive diamond grains having an average particle diameter of 5 µm was prepared in a tank for an ultrasonic washing machine, and the second element was immersed therein and treated under ultrasonic washing conditions using power and time as shown in Table 1. Interface roughness of the base element was controlled by changing the centerless conditions and the oxygen treatment conditions.

[0067] Subsequently, the base element was placed in the deposition device as described in the Fig.12, a diamond layer was deposited on a surface of the base member by a hot-wire CVD method. The deposition apparatus was provided with a reaction chamber having a diameter of Ø25 cm and a height of 20 cm. The reaction chamber contained therein a total of four tungsten wires having a thickness of Ø0.4 mm. Two of the four tungsten wires were arranged in a longitudinal direction of the base member, and the remaining two tungsten wires were arranged on a side surface to hold the base member therebetween. The base member was set in an upright state in which a cutting edge part was arranged on an upper side and a shank part was arranged on a lower side.

[0068] A diamond layer was deposited on the base member in a vacuum by heating to 920°C under the conditions that a deposition temperature was 920°C for five minutes in an initial stage and a deposition temperature was 900°C in a later stage. After the diamond layer was deposited, a maximum height of each of the first cutting edge, the first surface, and the second surface before the gas bombardment treatment described later was measured by using, as a measuring point, a center position of a length in the longitudinal direction corresponding to a cutting part.

[0069] A solid type end mill was obtained by performing the gas bombardment treatment after depositing the diamond layer within the deposition apparatus under conditions shown in Table 1.

[0070] The maximum heights Rye, Ryr, and Ryf and the arithmetic mean roughness values ​​Rae, Rar, and Raf of the first cutting edge, the first surface, and the second surface in the obtained end mill were measured, respectively, using the mean position of the length in the longitudinal direction corresponding to the cutting part as a measurement point. Measurements were performed by Raman scattering spectroscopy at an interface position between the diamond layer and the base member and at an intermediate position in the first cutting edge, the first surface, and the second surface at the position described above, and the SP3 ratios (S 1e , S 1r , S 1f , S 2e S 2r and S 2f ) were estimated.

[0071] SEM observations of the surfaces of the first cutting edge, the first face, and the second face were performed to check whether contours of diamond crystals were visible. If the contours of the diamond crystals were visible, an average particle diameter of the diamond crystals was measured. When the average particle diameter was measured, the measurements were performed in a field of view in which 10 or more diamond crystals were visible, with the result being 0.8 µm. Further, thicknesses of the diamond layer were measured by performing SEM observations of cross-sections of the diamond layer at a position 2 mm behind the first end of the end mill in a direction along the rotation axis and at a position 10 mm behind the first end. The results are shown in Tables 1 and 2.

[0072] Cutting performance was evaluated by conducting a cutting test using the obtained end mills under the following cutting conditions. The results are shown in Table 2. Cutting process: Drilling (through hole) Workpiece: CFRP Cutting speed (feed): 100 mm / min Delivery rate: 0.075 mm / tooth Cutting depth: 8 mm deep, Ø6 mm bore diameter Cutting condition: wet (using a cutting fluid)

[0073] Evaluation method: The presence or absence of chatter vibration in the initial machining phase was examined. The absence of chatter vibration is indicated by the symbol "◯", the presence of slight chatter vibration is indicated by the symbol "△", and the presence of chatter vibration greater than that indicated by the symbol "△" is indicated by the symbol "▲". A tendency toward chip enlargement during machining is evaluated as a chip discharge performance. The roughness of a finished surface after machining a cutting length of 20 m was measured. The cutting length until no further machinability was reached was evaluated. The results are shown in Table 3. Table 3 Sample No. Cutting performance Chatter vibration Chip output capacity Roughness of the finished surface (µm) Cutting length (m) 1 ◯ ◯ 1,2 52 2 ◯ ◯ 1,4 50 3 ◯ ◯ 1,5 49 4 ◯ ◯ 1,8 46 5 ◯ ◯ 2 45 6 ◯ ◯ 2,1 44 7 ◯ ◯ 2,3 42 8 △ ◯ 2,5 40 9 ▲ ▲ 3 35 10 △ ◯ 5 28 11 ▲ ▲ 5 30

[0074] Tables 1 to 3 show the following. In samples Nos. 1 to 8, where Rye is smaller than Ryr and Ryf is larger than Ryf, chatter vibration was absent or slight in the initial machining stage, chip discharge performance was good, the roughness of the finished surface was low and smooth, and the cutting length became longer. List of reference symbols 1, 101 cutting tool 2 cutting edge part 3 Shaft part 4 second cutting edge (cutting edge) 5 first cutting edge (cutting edge) 6 first groove (chip groove) 7 notch 105 cutting edge 8,108 first area 9,109 second area 10, 110 base element 11, 111 diamond layer 12 diamond crystals 13 groove (second groove) 32 holders 34 deployment 34a first use 34b second use 36 through hole

Claims

[1] A cutting tool (1; 101), comprising: a base element (10; 110), a diamond layer (11; 111) arranged on the base element (10; 110), and a first surface (8; 108), a second surface (9; 109) and a cutting edge (4, 5; 105) which is arranged at least in part of a ridge line at which the first surface (8; 108) intersects the second surface (9; 109), wherein the diamond layer (11; 111) is arranged in at least a part of the first surface (8; 108), at least a part of the second surface (9; 109) and at least a part of the cutting edge (4, 5; 105) and a maximum height in the cutting edge (4, 5; 105) is smaller than a maximum height in the first surface (8; 108) and the maximum height in the cutting edge (4, 5; 105) is greater than a maximum height in the second surface (9; 109), wherein in the cutting edge (4, 5; 105) the maximum height is 0.3 to 0.7 µm and an arithmetic mean roughness is 0.06 to 0.1 µm, in the first surface (8; 108) the maximum height is 0.8 to 1.4 µm and an arithmetic mean roughness is 0.1 to 0.25 µm and in the second surface (9; 109) the maximum height is 0.1 to 0.5 µm and an arithmetic mean roughness is 0.04 to 0.08 µm, wherein the cutting edge (4, 5; 105) has a convex-curved surface shape in a cross-section orthogonal to the ridge line, and the cutting edge (4, 5; 105) has a plurality of grooves (13) in a direction which intersects the ridge line, and wherein the plurality of grooves (13) are orthogonal to the ridge line. [2] The cutting tool (1; 101) according to claim 1, wherein an SP3 ratio in the cutting edge (4, 5; 105) is larger than an SP3 ratio in each of the first surface (8; 108) and the second surface (9; 109), an SP3 ratio being a ratio (SP3 / SP2) obtainable from an SP3 peak derived from diamond crystals (12) measurable by Raman spectrum analysis and an SP2 peak derived from a graphite phase. [3] The cutting tool (1; 101) according to claim 1 or 2, wherein contours of the diamond crystals (12) are perceptible when viewing the cutting edge (4, 5; 105) with a magnification of 10,000 to 30,000 times. [4] The cutting tool (1; 101) according to claim 1, wherein, in a front view of the first surface (8; 108), a length of each of the grooves (13) in a direction orthogonal to the ridge line is larger than a width of each of the grooves (13) in a direction along the ridge line. [5] The cutting tool (1; 101) according to any one of the preceding claims, wherein, in a front view of the first surface (8; 108), a length of each of the grooves (13) in a direction orthogonal to the ridge line is greater than a length of each of the grooves (13) in a direction orthogonal to the ridge line in a front view of the second surface (9; 109). [6] The cutting tool (1; 101) according to any one of the preceding claims, wherein a thickness of the diamond layer (11; 111) in the first surface (8; 108) is smaller than a thickness of the diamond layer (11; 111) in the cutting edge (4, 5; 105). [7] The cutting tool (1; 101) according to any one of the preceding claims, wherein a thickness of the diamond layer (11; 111) in the first surface (8; 108) is smaller than a thickness of the diamond layer (11; 111) in the second surface (9; 109).

Images