Cutting tool

Abstract

A cutting tool is a cutting tool having a rake face, a flank face, and a nose land, that is, a cutting edge, connecting the rake face and the flank face. In the cutting tool, a part of the rake face and a part of the flank face adjacent to the cutting edge are composed of a diamond sintered body containing diamond grains. A dislocation density of the part of the flank face is 8 x 1010 / m2 or less. The diamond grains have an average particle diameter of 0.1 μm or more and 50 μm or less. A content rate of the diamond grains in the diamond sintered body is 80 vol% or more and 99 vol% or less. 15 / m 2 The diamond grains have an average particle diameter of 0.1 μm or more and 50 μm or less. A content rate of the diamond grains in the diamond sintered body is 80 vol% or more and 99 vol% or less.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a cutting tool. This application claims priority based on Japanese Patent Application No. 2020-198392 filed on November 30, 2020. The entire contents of the Japanese Patent Application No. 2020-198392 are incorporated by reference in the present specification. BACKGROUND

[0002] In the past, a cutting tool to which a diamond sintered body is applied has been known. For example, in Japanese Patent Application Publication No. 2005-239472 (Patent Literature 1), a high-strength-high-wear-resistance diamond sintered body is disclosed, which has sintered diamond particles having an average particle diameter of 2 μm or less and a balance of a binding phase, characterized in that the content ratio of the sintered diamond particles in the diamond sintered body is 80 vol% or more and 98 vol% or less, the binding phase contains at least one or more elements selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, and molybdenum at a content ratio of 0.5 mass% or more and less than 50 mass% in the binding phase, and cobalt at a content ratio of 50 mass% or more and less than 99.5 mass% in the binding phase, a part or all of the at least one or more elements selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, and molybdenum exist as carbide particles having an average particle diameter of 0.8 μm or less, the structure of the carbide particles is discontinuous, and adjacent diamond particles are bonded to each other.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Application Publication No. 2005-239472 SUMMARY

[0006] The cutting tool of the present disclosure is a cutting tool having a rake face, a flank face, and a nose land connecting the rake face and the flank face. In the cutting tool, a part of the rake face and a part of the flank face adjacent to the nose land are composed of a diamond sintered body containing diamond particles. The dislocation density of the part of the flank face is 8 x 10 15 / m 2 or less. The average particle diameter of the diamond particles is 0.1 μm or more and 50 μm or less. The content ratio of the diamond particles in the diamond sintered body is 80 vol% or more and 99 vol% or less. BRIEF DESCRIPTION OF DRAWINGS

[0007] Figure 1 is a plan view of the cutting insert 100.

[0008] Figure 2This is a 3D view of cutting blade 100.

[0009] Figure 3 This is an enlarged three-dimensional schematic diagram showing the tip 20 of the cutting blade 100.

[0010] Figure 4 yes Figure 3 The enlarged side view of the blade tip 20 is shown.

[0011] Figure 5 This is a three-dimensional schematic diagram showing the tip 20 used as a cutting blade.

[0012] Figure 6 It is a process diagram showing the manufacturing method of the cutting blade. Detailed Implementation

[0013] [The problem this disclosure aims to solve]

[0014] When the diamond sintered body of Patent Document 1 is applied to cutting tools, etc., there is a problem of increased wear on the flank face, resulting in a shorter tool life. This disclosure was made in view of the above situation, and its object is to provide a cutting tool with improved tool life.

[0015] [The Effects of This Disclosure]

[0016] According to this disclosure, cutting tools with improved tool life can be obtained.

[0017] [Summary of Implementation Methods]

[0018] First, embodiments of this disclosure will be described.

[0019] (1) One embodiment of the cutting tool involves a rake face, a flank face, and a cutting edge connecting the rake face and the flank face. In the cutting tool, a portion of the rake face and a portion of the flank face adjacent to the cutting edge are composed of a diamond sintered body containing diamond particles. The dislocation density of a portion of the flank face is 8 × 10⁻⁶. 15 / m 2 The following conditions apply: The average particle size of the diamond particles is 0.1 μm or larger and 50 μm or smaller. The diamond particle content in the diamond sintered body is 80% or larger by volume and 99% or smaller by volume.

[0020] According to the cutting tool described in (1) above, the wear resistance of the flank face is improved by suppressing the reduction in strength of the diamond particles in the flank face. As a result, the life of the cutting tool is improved.

[0021] (2) Alternatively, in the cutting tool described in (1) above, the dislocation density of the diamond sintered body in a portion of the flank face is 7 × 10⁻⁶. 15 / m 2 The following.

[0022] According to the cutting tool of the above (2), it is possible to further improve tool life.

[0023] (3) Also, in the cutting tool of the above (1) or (2), the diamond sintered body can contain a bonding material. Also, the bonding material can contain at least one selected from the group consisting of a single metal, an alloy, and an intermetallic compound. Also, the single metal, the alloy, and the intermetallic compound can contain at least one metal element selected from the group consisting of a Group 4 element of the periodic table, a Group 5 element of the periodic table, a Group 6 element of the periodic table, iron, aluminum, silicon, cobalt, and nickel.

[0024] (4) Also, in the cutting tool of the above (1) or (2), the diamond sintered body can contain a bonding material. Also, the bonding material can contain at least one selected from the group consisting of a compound and a solid solution derived from the compound. Also, the compound can be composed of at least one selected from the group consisting of a single metal, an alloy, and an intermetallic compound and at least one selected from the group consisting of nitrogen, carbon, and oxygen. Also, the single metal, the alloy, and the intermetallic compound can contain at least one metal element selected from the group consisting of a Group 4 element of the periodic table, a Group 5 element of the periodic table, a Group 6 element of the periodic table, iron, aluminum, silicon, cobalt, and nickel.

[0025] (5) Also, in the cutting tool of the above (3) or (4), the bonding material can contain cobalt.

[0026] (6) Also, in the cutting tool of the above (1) to (5), the surface roughness Ra of a part of the rake face can be 120 nm or less.

[0027] According to the cutting tool of the above (6), it is possible to further improve tool life.

[0028] (7) Also, in the cutting tool of the above (1) to (6), the dislocation density of a part of the rake face can be 10 x 10 15 / m 2 The following.

[0029] According to the cutting tool of the above (7), it is possible to reduce the amount of wear of the crater wear of the rake face. Thus, it is possible to further improve tool life.

[0030] In the cutting tool, the dislocation density of a part of the flank face can be equal to or less than the dislocation density of a part of the rake face, or can be less than the dislocation density of a part of the rake face.

[0031] (8) Also, the cutting tool of (1) to (7) described above can have a base material that holds the diamond sintered body.

[0032] According to the cutting tool of (8) described above, the portion including the nose corner line can be composed of the diamond sintered body, and the other portion, that is, the base material, can be composed of a material that is inexpensive compared to the diamond sintered body, such as a metal material. Therefore, the manufacturing cost of the cutting tool can be reduced.

[0033] (9) Also, in the cutting tool of (1) to (7) described above, the entire rake face and the entire flank face can be composed of the diamond sintered body.

[0034] According to the cutting tool of (9) described above, by composing the entire rake face and the entire flank face, which are related to the tool life, of the diamond sintered body, the tool life can be reliably improved.

[0035] [Details of Embodiments]

[0036] The details of the embodiments of the present disclosure will be described with reference to the accompanying drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and repeated description will not be repeated.

[0037] The cutting tool related to the embodiments is, for example, a cutting insert 100. The cutting tool related to the embodiments is not limited to the cutting insert 100, and hereinafter, the cutting insert 100 will be described as an example of the cutting tool related to the embodiments.

[0038] (Configuration of the cutting tool related to the embodiments)

[0039] The configuration of the cutting insert 100 will be described.

[0040] <Outline configuration of the cutting insert 100>

[0041] Figure 1 is a plan view of the cutting insert 100. Figure 2 is a perspective view of the cutting insert 100. Figure 3 is an enlarged perspective view schematically showing a nose portion 20 of the cutting insert 100. Figure 4 is an enlarged side view schematically showing the nose portion 20. Figure 3 As shown in

[0042] Figure 1 and Figure 2 ​As shown, the cutting insert 100 has the base material 10 and the tip portion 20 which is a sintered body of diamond. The cutting insert 100 is polygonal in shape (for example, triangular in shape) in plan view. The polygonal shape (triangular shape) can also not be a strict polygonal shape (triangular shape). More specifically, the corners of the cutting insert 100 in plan view can also be rounded.

[0043] The base material 10 is polygonal in shape (for example, triangular in shape) in plan view. The base material 10 has a top surface 10a, a bottom surface 10b, and a side surface 10c. The top surface 10a and the bottom surface 10b are end surfaces in the thickness direction of the base material 10. The bottom surface 10b is the opposite surface of the top surface 10a in the thickness direction of the base material 10. The side surface 10c is a surface that connects the top surface 10a and the bottom surface 10b.

[0044] The top surface 10a has a mounting portion 10d. The mounting portion 10d is located at a corner of the top surface 10a in plan view. The distance between the top surface 10a and the bottom surface 10b at the mounting portion 10d is smaller than the distance between the top surface 10a and the bottom surface 10b other than the mounting portion 10d. That is, there is a step between the mounting portion 10d and the portion of the top surface 10a other than the mounting portion 10d.

[0045] The base material 10 is formed with a through-hole 11. The through-hole 11 penetrates the base material 10 in the thickness direction. The through-hole 11 is formed at the center of the base material 10 in plan view. For example, by inserting a fixing member (not shown) into the through-hole 11 and fastening the fixing member to a tool holder (not shown), the cutting insert 100 is supplied for cutting work.

[0046] The base material 10 is formed of, for example, cemented carbide. Cemented carbide is a composite material obtained by sintering carbide particles and a binder material. The carbide particles are, for example, particles of tungsten carbide, titanium carbide, tantalum carbide, or the like. The binder material is, for example, cobalt, nickel, iron, or the like. However, the base material 10 can also be formed of a material other than cemented carbide.

[0047] The tip portion 20 is mounted to the mounting portion 10d. The tip portion 20 is mounted to the base material 10 by, for example, brazing. The tip portion 20 has a rake face 20a, a relief face 20b, and a cutting edge 20c. The rake face 20a is connected to the portion of the top surface 10a other than the mounting portion 10d. The relief face 20b is connected to the side surface 10c. The cutting edge 20c is formed at the ridge line of the rake face 20a and the relief face 20b.

[0048] <Details of the sintered body constituting the tip portion 20>

[0049] The tip portion 20 is formed of a sintered body containing diamond grains and a bonding material. From a different viewpoint, a part of the rake face 20a and a part of the flank face 20b adjacent to the cutting edge 20c as a tip ridge line in the tip portion 20 are composed of a diamond sintered body containing diamond grains.

[0050] Dislocation density of the diamond sintered body:

[0051] The dislocation density of the part of the flank face 20b is 8 x 10 15 / m 2 or less. The dislocation density of the diamond sintered body (specifically, the diamond grains) in the part of the flank face 20b can be 7 x 10 15 / m 2 or less. The dislocation density of the part of the rake face 20a can be 10 x 10 15 / m 2 or less. The dislocation density of the part of the flank face 20b can be lower than the dislocation density of the part of the rake face 20a, or can be higher than the dislocation density of the part of the flank face 20b.

[0052] By making the dislocation density of the diamond grains 8 x 10 15 / m 2 or less, generation of cracks of the diamond grains can be suppressed, and the strength can be suppressed from decreasing, and a diamond sintered body excellent in wear resistance can be formed. In addition, the diamond sintered body described above has a high thermal conductivity. Therefore, thermal wear due to temperature rise of the tip during cutting processing can be suppressed. In addition, the inventors of the present application confirmed that a diamond sintered body having a dislocation density of the diamond grains of less than 8.1 x 10 13 / m 2 cannot be manufactured. The dislocation density of the part of the flank face 20b can be 8.1 x 10 13 / m 2 or more and 8 x 10 15 / m 2 or less, or can be 8.1 x 10 13 / m 2 or more and 7 x 10 15 / m 2 or less. The dislocation density of the part of the rake face 20a can be 8.1 x 10 13 / m 2 or more and 10 x 10 15 / m 2 or less.

[0053] Previously, the relationship between the dislocation density of diamond particles in a diamond sintered body and the physical properties of the diamond sintered body was not considered. Therefore, the inventors of this invention conducted an in-depth study on the relationship between the dislocation density of diamond particles in a diamond sintered body and the wear resistance of the diamond sintered body. As a result, it was discovered for the first time that, compared with conventional diamond sintered bodies, reducing the dislocation density of diamond particles can suppress wear during machining. The reason is believed to be that by reducing the dislocation density, the heat generated during machining can be effectively transferred to the entire diamond sintered body, thus suppressing wear of the diamond sintered body caused by heat generation. Furthermore, this investigation revealed that the dislocation density of diamond particles in existing diamond sintered bodies (e.g., the diamond sintered body described in Patent Document 1) is 1.01 × 10⁻⁶. 16 / m 2 Above and less than 1.18×10 16 / m 2 .

[0054] In this embodiment, the location for measuring the dislocation density in a portion of the flank face 20b is as follows: Figure 3 as well as Figure 4 The diagram shows the position adjacent to the cutting edge 20c, which serves as the tool tip edge. Specifically, an imaginary point 20cb is set at a distance L (specifically 100 μm) from any position 20ca on the cutting edge 20c in a direction perpendicular to the rake face 20a. A straight line is drawn from this imaginary point 20cb in a direction parallel to the rake face 20a and perpendicular to the tangent at any position 20ca on the cutting edge 20c. The intersection point 20cc of this straight line and the flank face 20b is taken as the location for measuring the dislocation density.

[0055] In addition, when measuring the dislocation density on a portion of the rake face 20a of the tool tip 20, an imaginary line is drawn along the cutting edge 20c at a position on the rake face 20a that is a certain distance (specifically 100 μm) away from the cutting edge 20c, and any position on this imaginary line is taken as the measurement position.

[0056] In this specification, the dislocation density of the diamond sintered body was measured in a large-scale radiometric facility (e.g., the Kyushu Synchrotron Light Research Center (Saga Prefecture)). Specifically, the measurement was performed using the method described below.

[0057] A tool tip 20, constructed from a diamond sintered body, was prepared as the test specimen. The observation surfaces (rake face 20a and flank face 20b) of the test specimen, including the aforementioned measurement locations, were mirror-polished using a diamond polishing slurry with an average particle size of 3 μm. The specimen was then immersed in hydrochloric acid for 72 hours. As a result, the bound phase dissolved in the hydrochloric acid on the observation surfaces of the test specimen, leaving only diamond particles.

[0058] For the measurement position of the test body, X-ray diffraction measurement was performed under the following conditions to obtain the line profile of the diffraction peak from each of the (111), (220), (311), (331), (422), (440), and (531) planes as the main orientation of diamond.

[0059] X-ray source: Synchrotron radiation

[0060] Apparatus conditions: Detector NaI (fluorescence cutoff by appropriate ROI)

[0061] Energy: 18 keV (wavelength: 0.7 A) )

[0062] Diffracting crystal: Si (111)

[0063] Incident slit: Width 3 mm x height 0.5 mm

[0064] Light receiving slit: Double slit (width 3 mm x height 0.5 mm)

[0065] Mirror: Platinum-coated mirror

[0066] Incident angle: 2.5 mrad

[0067] Scanning method: 2Θ-Θ scan

[0068] Measurement peaks: Seven of the (111), (220), (311), (331), (422), (440), and (531) planes of diamond. However, in cases where it is difficult to obtain the profile due to texture, orientation, etc., the peak of the plane index is excluded.

[0069] Measurement conditions: In the full width at half maximum corresponding to each measurement peak, the measurement points were set to nine or more points. The peak top intensity was 2000 counts or more. Since the edges of the peak are also used for analysis, the measurement range was about 10 times the full width at half maximum.

[0070] The line profile obtained by the above-described X-ray diffraction measurement is formed in a shape including both the true spread caused by physical quantities such as inhomogeneous strain of the test body and the spread caused by the apparatus. In order to obtain the inhomogeneous strain and the crystallite size, the component caused by the apparatus is removed from the measured line profile to obtain the true line profile. The true line profile is obtained by fitting the obtained line profile and the line profile caused by the apparatus using a pseudo Voigt function and subtracting the line profile caused by the apparatus. As a standard sample for removing the diffraction line spread caused by the apparatus, LaB6 is used. In addition, in the case of using synchrotron radiation having high parallelism, the diffraction line spread caused by the apparatus can also be considered to be 0.

[0071] The real line profile obtained is analyzed using a modified Williamson-Hall method and a modified Warren-Averbach method, whereby the dislocation density is calculated. The modified Williamson-Hall method and the modified Warren-Averbach method are known line profile analysis methods for calculating dislocation density.

[0072] The formula of the modified Williamson-Hall method is represented by the following formula (I).

[0073] [Num 1]

[0074]

[0075] In the above formula (I), ΔK represents the half width of the line profile. D represents the crystallite size. M represents the configuration parameter. b represents the Burgers vector. p represents the dislocation density. K represents the scattering vector. O(K 2 C) represents the higher order term of K 2 C. C represents the average value of the contrast factor.

[0076] C in the above formula (I) is represented by the following formula (II).

[0077] C = C h00 [1 - q (h 2 k 2 +h 2 l 2 +k 2 l 2 ) / (h 2 +k 2 +l 2 ) 2 ] (II)

[0078] In the above formula (II), the respective contrast factors C h00 of the screw dislocation and the edge dislocation and the coefficient q related to the contrast factor are calculated using the calculation code ANIZC, under the conditions that the slip system is <110> {111}, the elastic stiffness C 11 is 1076 GPa, C 12 is 125 GPa, C 44 is 576 Gpa. In the above formula (II), h, k, and l respectively correspond to the Miller indices (hkl) of the diamond. The contrast factor C h00 is 0.183 in the screw dislocation and is 0.204 in the edge dislocation. The coefficient q related to the contrast factor is 1.35 in the screw dislocation and is 0.30 in the edge dislocation. Furthermore, the screw dislocation ratio is fixed at 0.5 and the edge dislocation ratio is fixed at 0.5.

[0079] In addition, using a contrast factor C between dislocations and inhomogeneous strain, the following equation (III) holds. In the following equation (III), R e represents the effective radius of a dislocation. ε(L) represents inhomogeneous strain.

[0080] <ε(L) 2 >=(pCb 2 / 4π)ln(R e / L) (III)

[0081] According to the relationship of the above equation (III) and the Warren-Averbach equation, as a modified Warren-Averbach method, the dislocation density p and the crystallite size can be obtained as shown in the following equation (IV). In the following equation (IV), A(L) represents a Fourier series. A S (L) represents a Fourier series related to the crystallite size. L represents a Fourier length.

[0082] lnA(L)=lnA S (L)-(πL 2 ρb 2 / 2)ln(R e / L)(K 2 C)+O(K 2 C) 2 (IV)

[0083] Detailed contents of the modified Williamson-Hall method and the modified Warren-Averbach method are described in “T. Ungar and A. Borbely, “The effect of dislocation contrast on x-ray line broadening: A new approach to line profile analysis” Appl. Phys. Lett., vol. 69, no. 21, p. 3173, 1996.” and “T. Ungar, S. Ott, P. Sanders, A. Borbely, J. Weertman, “Dislocations, grain size and planar faults in nanostructured copper determined by high resolution X-ray diffraction and a new procedure of peak profile analysis” Acta Mater., vol. 46, no. 10, pp. 3693-3699, 1998.”.

[0084] The inventors of the present application have confirmed that, as long as the dislocation density of diamond particles is measured in the same test sample, the measurement results hardly deviate even if the selection site of the measurement range is changed and the calculation is performed multiple times. That is, the inventors of the present application have found that, even if the measurement field is arbitrarily set, the results do not arbitrarily change.

[0085] In the present embodiment, the diamond sintered body contains a bonding material. The bonding material can contain at least one selected from the group consisting of a single metal, an alloy, and an intermetallic compound. The single metal, the alloy, and the intermetallic compound can contain at least one metal element selected from the group consisting of a Group 4 element of the periodic table, a Group 5 element of the periodic table, a Group 6 element of the periodic table, iron, aluminum, silicon, cobalt, and nickel (hereinafter, also referred to as "Group A").

[0086] In addition, the bonding material can contain at least one selected from the group consisting of a compound and a solid solution derived from the compound. The compound can be composed of at least one selected from the group consisting of a single metal, an alloy, and an intermetallic compound, and at least one selected from the group consisting of nitrogen, carbon, and oxygen (hereinafter, also referred to as "Group B"). The single metal, the alloy, and the intermetallic compound can contain at least one metal element selected from the group consisting of a Group 4 element of the periodic table, a Group 5 element of the periodic table, a Group 6 element of the periodic table, iron, aluminum, silicon, cobalt, and nickel.

[0087] In other words, the above bonding material can be any one of the following (a) to (f).

[0088] (a) The above bonding material is composed of at least one selected from the group consisting of a single metal, an alloy, and an intermetallic compound, the single metal, the alloy, and the intermetallic compound containing at least one metal element selected from Group A.

[0089] (b) The above bonding material contains at least one selected from the group consisting of a single metal, an alloy, and an intermetallic compound, the single metal, the alloy, and the intermetallic compound containing at least one metal element selected from Group A.

[0090] (c) The above bonding material is composed of at least one selected from the group consisting of a compound and a solid solution derived from the compound, the compound being composed of at least one metal element selected from Group A and at least one non-metal element selected from Group B.

[0091] (d) The bonding material described above contains at least one selected from the group consisting of a compound composed of at least one metal element selected from Group A and at least one nonmetal element selected from Group B and a solid solution derived from the compound.

[0092] (e) The bonding material described above is composed of at least one selected from the group consisting of a single metal, an alloy, and an intermetallic compound containing at least one metal element selected from Group A and at least one selected from the group consisting of a compound composed of at least one metal element selected from Group A and at least one nonmetal element selected from Group B and a solid solution derived from the compound.

[0093] (f) The bonding material described above contains at least one selected from the group consisting of a single metal, an alloy, and an intermetallic compound containing at least one metal element selected from Group A and at least one selected from the group consisting of a compound composed of at least one metal element selected from Group A and at least one nonmetal element selected from Group B and a solid solution derived from the compound.

[0094] The Group 4 elements of the periodic table include, for example, titanium (Ti), zirconium (Zr), and hafnium (Hf). The Group 5 elements of the periodic table include, for example, vanadium (V), niobium (Nb), and tantalum (Ta). The Group 6 elements of the periodic table include, for example, chromium (Cr), molybdenum (Mo), and tungsten (W).

[0095] In one aspect of the present embodiment, the bonding material described above preferably contains at least one selected from the group consisting of cobalt, titanium, iron, tungsten, and boron, and more preferably contains cobalt. The bonding material can contain titanium in addition to cobalt. The most abundant component in the bonding material is preferably cobalt.

[0096] The composition of the bonding material contained in the diamond sintered body can be determined by the EDX attached to the SEM described above.

[0097] The average particle diameter of the diamond particles in the sintered body constituting the tip portion 20 is preferably 0.1 μm or more and 50 μm or less. The average particle diameter of the diamond particles can be 0.2 μm or more and 40 μm or less. By making the average particle diameter of the diamond particles 0.1 μm or more, the diamond particles are densely sintered to form a diamond sintered body excellent in damage resistance. By making the average particle diameter of the diamond particles 50 μm or less, a diamond sintered body excellent in cutting stability is formed without anisotropy in the case where the tip is used as a cutting tool.

[0098] In the present embodiment, the average particle diameter of the diamond particles refers to a value obtained by calculating an average of median particle diameters d50 of a plurality of diamond particles respectively measured in each measurement field at five arbitrary positions. Specifically, the average particle diameter of the diamond particles in the sintered body constituting the tip portion 20 is calculated by the following method.

[0099] In the calculation of the average particle diameter of the diamond particles in the sintered body constituting the tip portion 20, first, a sample including a cross section is cut out from an arbitrary position of the tip portion 20. The cutting out of the sample is performed using, for example, a focused ion beam device, a cross section polisher device, or the like.

[0100] Second, the cross section of the cut-out sample is observed by a scanning electron microscope (SEM). By the observation, a reflected electron image of the cross section of the cut-out sample (hereinafter referred to as "SEM image") is obtained. In the observation based on the SEM, the magnification is adjusted so as to include 100 or more diamond particles in the measurement field. The SEM images are acquired at five positions in the cross section of the cut-out sample.

[0101] Third, the distribution of the particle diameters of the diamond particles included in the measurement field is acquired by image processing of the SEM images. The image processing is performed using, for example, Win ROOF ver. 7.4.5, WinROOF2018, or the like manufactured by Saneyoshi Corporation. The particle diameter of each diamond particle is obtained by calculating the equivalent circle diameter from the area of each diamond particle as a result of the image processing. Further, in acquiring the distribution of the particle diameters of the diamond particles, the diamond particles partially located outside the measurement field are not taken into account.

[0102] Fourth, the median particle diameter d50 of the diamond particles included in the measurement field is determined from the distribution of the particle diameters of the diamond particles included in the measurement field obtained as described above. The determined median particle diameters d50 are averaged for the five SEM images, and the value obtained thereby is regarded as the average particle diameter of the diamond particles in the sintered body constituting the tip portion 20.

[0103] The content ratio (volume percentage) of the diamond particles in the sintered body constituting the tip portion 20 is preferably 80 volume percent or more and 99 volume percent or less. The content ratio (volume percentage) of the diamond particles in the diamond sintered body can be confirmed by performing an observation of the structure, elemental analysis, and the like on the diamond sintered body using an energy dispersive X-ray analysis device (EDX) attached to a scanning electron microscope (SEM) ("JSM-7800F" (trade name) manufactured by JEOL Ltd.) (hereinafter also referred to as "SEM-EDX"). Specifically, the content ratio of the diamond particles in the sintered body constituting the tip portion 20 is calculated by the following method.

[0104] In the calculation of the content ratio (proportion) of the diamond particles in the sintered body constituting the tip portion 20, first, a sample including a cross section is cut out from an arbitrary position of the tip portion 20. The cutting out of the sample is performed using, for example, a focused ion beam device, a cross-section polisher device, or the like.

[0105] Second, the cross section of the cut-out sample is observed by SEM. Through the observation, an SEM image of the cross section of the cut-out sample is obtained. In the observation based on SEM, the magnification is adjusted so as to include 100 or more diamond particles within the measurement field of view. SEM images are acquired at five positions within the cross section of the cut-out sample.

[0106] Third, the proportion of the diamond particles included within the measurement field of view is calculated by performing image processing on the SEM images. The image processing is performed, for example, by performing a binarization process of the SEM images using Win ROOF ver. 7.4.5, WinROOF2018, or the like manufactured by Saneyoshi Shoji Co., Ltd. The dark field in the SEM image after the binarization process corresponds to the region in which the diamond particles exist. The value obtained by dividing the area of the dark field by the area of the measurement region is regarded as the volume ratio of the diamond particles in the sintered body constituting the tip portion 20.

[0107] In the cutting tool of the present embodiment, the surface roughness Ra of a part of the rake face 20a at the tip portion 20 can be 120 nm or less. The surface roughness Ra of a part of the rake face 20a can be 55 nm or less. The surface roughness Ra can be measured, for example, using a laser microscope. The measurement position of the surface roughness Ra is the same position as the measurement position of the dislocation density.

[0108] In the present specification, the "surface roughness Ra" refers to the arithmetic average roughness Ra defined in JIS B 0601, and is defined as a value obtained by extracting a reference length in the direction of the average line of a roughness curve, summing up and averaging the distances (absolute values of deviations) from the average line of the extracted portion to the measurement curve.

[0109] <Modification example>

[0110] The cutting tool according to the present embodiment is different from the cutting insert 100 shown in FIG. 1 in that the cutting tool as a whole can be composed of a diamond sintered body. Figures 1 to 4 The cutting insert 100 shown in FIG. 1 is different from the cutting tool shown in FIG. 2 in that the cutting insert 100 as a whole is composed of a diamond sintered body. Figure 5 is a perspective view showing a nose portion 20 used as a cutting insert. Figure 5 The nose portion 20 shown in FIG. 3 is composed of a diamond sintered body as a whole, and the nose portion 20 itself is used as a cutting insert. From a different viewpoint, Figure 5 The rake face 20a as a whole and the flank face 20b as a whole of the cutting tool shown in FIG. 4 are composed of a diamond sintered body.

[0111] <Manufacturing method of cutting insert>

[0112] In order to realize the cutting insert 100 as the cutting tool of the present embodiment, the following countermeasures are required: as the diamond sintered body to be the nose portion 20, a diamond sintered body having a sufficiently low dislocation density is obtained, and in a machining process for forming the flank face 20b or the rake face 20a of the diamond sintered body, machining that reduces the machining load on the diamond sintered body and avoids an increase in the dislocation density is performed. Hereinafter, one example of a manufacturing method of the cutting insert 100 will be described. Figure 6 is a process chart showing a manufacturing method of the cutting insert 100. As shown in Figure 6 The manufacturing method of the cutting insert 100 including the nose portion 20 has a powder preparation process S1, a powder mixing process S2, and a sintering process S3 as a manufacturing process of the sintered body constituting the nose portion 20, and a machining process S4 including a process of machining the flank face 20b and the rake face 20a and a process of fixing the nose portion 20 to the base material 10.

[0113] In the powder preparation process S1, a raw powder of diamond particles (hereinafter also referred to as "diamond powder") and a raw powder of a bonding material (hereinafter, also referred to as "bonding material raw powder") are prepared. The diamond powder is not particularly limited, and a publicly known diamond particle can be used as the raw powder.

[0114] The average particle diameter of the diamond powder is not particularly limited, and can be set to 0.1 μm or more and 50 μm or less, for example.

[0115] The bonding material raw powder is not particularly limited, and can be a powder containing elements constituting the bonding material. As the bonding material raw powder, for example, a powder of cobalt, a powder of titanium, or the like can be listed. The bonding material raw powder can be used alone or in combination with a plurality of powders according to the composition of the target bonding phase.

[0116] In the powder mixing step S2, mixing of the diamond powder and the binder material raw material powder is performed. The mixing is performed using, for example, a mortar or a ball mill. However, the mixing method is not limited thereto. The mixing method can be wet or dry. Hereinafter, the mixture of the diamond powder, the binder material powder, and the boron powder is referred to as "mixed powder". At this time, the diamond powder and the binder material raw material powder described above can be mixed at an arbitrary mixing ratio so that the content rate of the diamond particles in the diamond sintered body is within the range described above.

[0117] In the sintering step S3, the mixed powder is sintered. The sintering is performed by disposing the mixed powder in a container and holding the mixed powder at a predetermined sintering temperature under a predetermined sintering pressure. In order to prevent impurities from being mixed into the mixed powder (sintered body), the container is formed of a high-melting-point metal such as tantalum, niobium, or the like. The sintering step S3 in the present embodiment includes a step S31 of sintering the mixed powder and a step S32 of reducing dislocations in the diamond particles described later.

[0118] In the step S31 of sintering the mixed powder, the mixed powder described above is sintered at a sintering pressure of 4 GPa or more and less than 5 GPa, a sintering temperature of 1400°C or more and 1550°C or less, and a sintering time of 15 minutes or more and 60 minutes or less.

[0119] In the present embodiment, the path from a state of normal temperature (23 ± 5°C) and atmospheric pressure to a state of the sintering pressure and the sintering temperature is not particularly limited.

[0120] The high-pressure high-temperature generating device used in the manufacturing method of the diamond sintered body of the present embodiment is not particularly limited as long as it is a device that can obtain the conditions of the target pressure and temperature. From the viewpoint of improving productivity and workability, the high-pressure high-temperature generating device is preferably a belt-type high-pressure high-temperature generating device. In addition, the container that accommodates the mixed powder is not particularly limited as long as it is a high-pressure high-temperature resistant material, and for example, tantalum (Ta), niobium (Nb), or the like is preferably used.

[0121] In order to prevent impurities from being mixed into the diamond sintered body, for example, the mixed powder described above is first put into a capsule made of a high-melting-point metal such as Ta, Nb, or the like, and is heat-sealed in a vacuum to remove adsorbed gas and air from the mixed powder. Thereafter, the step S31 of sintering the mixed powder described above and the step S32 of reducing dislocations in the diamond particles described later are preferably performed. For example, after the step S31 of sintering the mixed powder described above, the mixed powder described above is preferably not taken out of the capsule made of the high-melting-point metal, and the step S32 of reducing dislocations in the diamond particles is continued in this state.

[0122] The sintering pressure is preferably 4 GPa or more and less than 5 GPa, and more preferably 4.5 GPa or more and less than 5 GPa.

[0123] The sintering temperature is preferably 1400°C or more and 1550°C or less, and more preferably 1450°C or more and 1550°C or less.

[0124] The sintering time is preferably 15 minutes or more and 60 minutes or less, and more preferably 15 minutes or more and 20 minutes or less.

[0125] In the process S32 of reducing dislocations in the diamond particles, the mixed powder is heated at a holding pressure of 6.5 GPa or more and 8 GPa or less, a holding temperature of 1600°C or more and 1900°C or less, and a holding time of 50 minutes or more and 190 minutes or less, to reduce dislocations in the diamond particles. Thus, the diamond sintered body of the present disclosure is obtained. The inventors of the present application believe that, by this process, the dissolution and reprecipitation of diamond are promoted, but the reprecipitated diamond particles have few dislocations, and thus a diamond sintered body with few dislocations is obtained.

[0126] The holding pressure is preferably 6.5 GPa or more and 8 GPa or less, and more preferably 6.5 GPa or more and 7 GPa or less.

[0127] The holding temperature is preferably 1600°C or more and 1900°C or less, and more preferably 1600°C or more and 1700°C or less.

[0128] The holding time is preferably 50 minutes or more and 190 minutes or less, and more preferably 60 minutes or more and 180 minutes or less.

[0129] In the machining process S4, the diamond sintered body obtained in the sintering process S3 is machined to be shaped into the shape of the nose portion 20. In addition, the nose portion 20 is attached to the base material 10. In this way, the cutting insert 100 can be obtained.

[0130] In the machining process S4, the relief surface 20b and the rake surface 20a of the nose portion 20 are machined. At this time, the relief surface 20b or the rake surface 20a, which is the machined surface, is machined with reduced machining load. As a result, it is possible to suppress the case where the dislocation density of the relief surface 20b or the rake surface 20a increases due to the machining. As a machining method with reduced machining load, for example, low-output laser machining, polishing machining with reduced machining load, or the like can be used.

[0131] (EFFECTS OF THE CUTTING TOOL ACCORDING TO THE EMBODIMENTS)

[0132] Hereinafter, the effects of the cutting insert 100 will be described.

[0133] In the cutting insert 100 according to the present embodiment, the dislocation density of the diamond grains in the relief surface 20b is 8 x 10 15 / m 2 Hereinafter, the dislocation density in the diamond grains constituting the relief surface 20b is suppressed from increasing, and thus the strength is suppressed from decreasing. As a result, the wear resistance of the relief surface 20b is improved, and thus the life of the cutting insert 100 is improved.

[0134] Further, by making the dislocation density of a portion of the rake surface 20a of the cutting insert 100 10 x 10 15 / m 2 Hereinafter, the amount of wear of the crater wear of the rake surface 20a can be reduced. Further, by making the surface roughness Ra of the rake surface 20a 120 nm or less, the tool life can be further improved. Further, by making the surface roughness Ra of the rake surface 20a 55 nm or less, the effect of improving the tool life can be further increased.

[0135] (Example)

[0136] A cutting test performed to confirm the effect of the cutting insert 100 will be described.

[0137] <Sample>

[0138] In Tables 1 and 2, the conditions of the tip portion, i.e., the sample, composed of a diamond sintered body for the cutting test are shown. As shown in Table 1, Sample 1 to Sample 17 were provided in the cutting test.

[0139] Here, the dislocation density of a portion of the relief surface of each sample was made 8 x 10 15 / m 2 This was made Condition Al. The dislocation density of the diamond sintered body in the portion of the relief surface was made 7 x 10 15 / m 2 This was made Condition A2. The dislocation density of the diamond sintered body in the portion of the relief surface was made 6 x 10 15 / m 2 This was made Condition A3.

[0140] The average particle diameter of the diamond grains in each sample was made 0.1 μm or more and 50 μm or less as Condition Bl. The content rate of the diamond grains in each sample was made 80 vol% or more and 99 vol% or less as Condition Cl.

[0141] A surface roughness Ra of a part of the rake face of each sample was set to be 120 nm or less as condition Dl. A surface roughness Ra of a part of the rake face of each sample was set to be 55 nm or less as condition D2. A dislocation density of a part of the rake face of each sample was set to be 10 x 10 15 / m 2 A dislocation density of a part of the rake face was set to be 6 x 10 15 / m 2 A dislocation density of a part of the rake face was set to be 6 x 10

[0142]

[0143]

[0144] Samples 1, 2, 4, 5, 6, 8 to 17 satisfied condition Al. Samples 1, 4, 5, 8 to 17 also satisfied condition A2. Samples 1, 4, 5, 8 to 11 also satisfied condition A3.

[0145] Samples 1 to 17 all satisfied condition El. Samples 1 to 3, 8 to 17 also satisfied condition E2.

[0146] Sample 13 did not satisfy condition Bl. Sample 14 and sample 17 did not satisfy condition Cl. Samples 10, 11 did not satisfy condition Dl.

[0147] <Test Method>

[0148] The first test method, the second test method, and the third test method were used in the cutting test. The first test method was used for the evaluation of samples 1 to 7, the second test method was used for the evaluation of samples 8 to 11, and the third test method was used for the evaluation of samples 12 to 17. Details of the first test method, the second test method, and the third test method are shown in Table 3.

[0149]

[0150] <Results>

[0151] The results of the cutting test are shown in Table 4. As shown in Table 4, samples 1, 2, 4 to 6, 8 to 12, 15, 16 showed relatively long tool life. On the other hand, in samples 3, 7, 13, 14, 17, a notch (hereinafter referred to as "initial notch") was generated at the tip portion 20 at the initial stage of cutting.

[0152]

[0153] As described above, samples 1, 2, 4-6, 8-12, 15, and 16 satisfy conditions A1, B1, and C1, while samples 3, 7, 13, 14, and 17 do not satisfy any one of conditions A1, B1, and C1. This comparison shows that by satisfying conditions A1, B1, and C1, the tool life of the cutting insert 100 is improved.

[0154] Furthermore, focusing on samples 8 to 11, the tool life of samples 8 and 9, which meet condition D1, is longer than that of samples 10 and 11, which do not meet condition D1. This comparison shows that by further satisfying condition D1, the tool life of the cutting insert 100 is further improved.

[0155] Furthermore, considering samples 4 and 5, the tool life of sample 4, which satisfies condition D2, is longer than that of sample 5, which satisfies condition D1 but not condition D2. This comparison shows that by further satisfying condition D2, the tool life of the cutting insert 100 is further improved.

[0156] The embodiments disclosed herein should be considered exemplary in all respects, not limiting. The essential scope of this disclosure is not defined by the foregoing embodiments, but by the claims, and is intended to include all modifications equivalent to and within the scope of the claims.

[0157] Explanation of reference numerals in the attached figures

[0158] 10: Substrate; 10a: Top surface; 10b: Bottom surface; 10c: Side surface; 10d: Mounting part; 11: Through hole; 20: Tool tip; 20a: Rake face; 20b: Back face; 20c: Cutting edge; 20ca: Position; 20cb: Imaginary point; 20cc: Intersection point; 100: Cutting insert; S1: Powder preparation process; S2: Powder mixing process; S3: Sintering process; S4: Machining process.

Claims

1. A cutting tool having a rake face, a flank face, and a nose corner line connecting the rake face and the flank face, wherein, a part of the rake face and a part of the flank face adjacent to the nose corner line are composed of a diamond sintered body containing diamond grains, the average particle diameter of the diamond grains is 0.1 μm or more and 50 μm or less, The dislocation density of a portion of the flank face is 8 x 10 15 / m 2 Hereinafter, the content rate of the diamond grains in the diamond sintered body is 80 vol% or more and 99 vol% or less.

3. The cutting tool according to claim 1 or 2, wherein, 2. The cutting tool of claim 1, wherein, The dislocation density of the diamond compact in a portion of the flank face is 7 x 10 15 / m 2 Below. the diamond sintered body contains a binding material, the binding material contains at least one selected from the group consisting of a single metal, an alloy, and an intermetallic compound, the single metal, the alloy, and the intermetallic compound contain at least one metal element selected from the group consisting of a Group 4 element of the periodic table, a Group 5 element of the periodic table, a Group 6 element of the periodic table, iron, aluminum, silicon, cobalt, and nickel.

4. The cutting tool according to claim 1 or 2, wherein, the diamond sintered body contains a binding material, the binding material contains at least one selected from the group consisting of a compound and a solid solution derived from the compound, the compound is composed of at least one selected from the group consisting of a single metal, an alloy, and an intermetallic compound and at least one selected from the group consisting of nitrogen, carbon, and oxygen, the single metal, the alloy, and the intermetallic compound contain at least one metal element selected from the group consisting of a Group 4 element of the periodic table, a Group 5 element of the periodic table, a Group 6 element of the periodic table, iron, aluminum, silicon, cobalt, and nickel. the binding material contains cobalt.

5. The cutting tool of claim 4, wherein, the surface roughness Ra of the part of the rake face is 120 nm or less.

6. The cutting tool according to claim 1 or 2, wherein, the cutting tool is provided with a base material that holds the diamond sintered body.

7. The cutting tool according to claim 1 or 2, wherein, The dislocation density of a portion of the rake face is 10 x 10 15 / m 2 Below.

8. The cutting tool according to claim 1 or 2, wherein, the entire rake face and the entire flank face are composed of the diamond sintered body.

9. The cutting tool according to claim 1 or 2, wherein, the entire rake face and the entire flank face are composed of the diamond sintered body.

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