Cutting insert and cutting tool

Abstract

This cutting insert is provided with a cubic boron nitride sintered body containing a plurality of cubic boron nitride particles and a binding phase in which the plurality of cubic boron nitride particles are bound. In the cross section of the cubic boron nitride sintered body, the length of the grain boundary between the plurality of cubic boron nitride particles and the binder phase per unit area of the plurality of cubic boron nitride particles is 3.2 [mu] m-1 or more.

Description

Cross-references to related applications

[0001] This application claims the benefit of priority from Japanese patent application No. 2022-103940 filed on Jun. 28, 2022, the disclosure of which is hereby incorporated by reference in its entirety. Technical Field

[0002] The present invention relates to a cutting insert and a cutting tool. Background Art

[0003] Cubic boron nitride (cBN) has a hardness second only to diamond and excellent chemical stability. Therefore, cBN sintered bodies are widely used as cutting tools for machining iron-based metals such as hardened steel, cast iron, or sintered alloys.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent No. 6900590 Summary of the invention

[0007] A cutting insert according to one embodiment of the present invention comprises a cubic boron nitride sintered body, which contains a plurality of cubic boron nitride particles and a binding phase for binding the plurality of cubic boron nitride particles. In a cross section of the cubic boron nitride sintered body, the length of a grain boundary between the plurality of cubic boron nitride particles and the binding phase per unit area of ​​the plurality of cubic boron nitride particles is 3.2 μm －1 above. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a perspective view showing an example of the cutting insert according to the embodiment.

[0009] Figure 2 It is a side cross-sectional view showing an example of the cutting insert according to the embodiment.

[0010] Figure 3 This is a cross-sectional view showing an example of a coating layer according to an embodiment.

[0011] Figure 4 yes Figure 3 A schematic enlarged view of section H is shown.

[0012] Figure 5 This is a cross-sectional view showing an example of a cBN-based sintered body constituting the substrate of the embodiment.

[0013] Figure 6 This is a front view showing an example of a cutting tool according to an embodiment.

[0014] Figure 7The diagram shows the results of image analysis corresponding to the photographs of each cross section of the cBN sintered body of the example and the photographs of each cross section of the cBN sintered body of the comparative example.

[0015] Figure 8 This is a partially enlarged view of a cross-sectional photograph of field No. 1 of a cBN-based sintered body of an example.

[0016] Fig. 9 This is a partially enlarged view of a cross-sectional photograph of field No. 1 of a cBN-based sintered body of a comparative example. DETAILED DESCRIPTION

[0017] Hereinafter, the mode for implementing the cutting insert and the cutting tool of the present invention (hereinafter, referred to as "embodiment") is described in detail with reference to the accompanying drawings. The cutting insert and the cutting tool of the present invention are not limited to this embodiment. The various embodiments can be appropriately combined within the scope that does not conflict with the content. In the following various embodiments, the same symbols are attached to the same parts, and repeated descriptions are omitted.

[0018] In the embodiments shown below, expressions such as "certain", "orthogonal", "perpendicular" or "parallel" are sometimes used, but these expressions do not need to be "certain", "orthogonal", "perpendicular" or "parallel" in a strict sense. That is, the above expressions allow for deviations in manufacturing accuracy, setting accuracy, etc.

[0019] Cubic boron nitride (cBN) has a hardness second only to diamond and excellent chemical stability. Therefore, cBN sintered bodies are widely used as cutting tools for machining iron-based metals such as hardened steel, cast iron, or sintered alloys.

[0020] In the above-mentioned prior art, there is room for further improvement in terms of improving wear resistance and fracture resistance.

[0021] Therefore, it is desired to realize a technology that can overcome the above-mentioned problems and improve wear resistance and fracture resistance.

[0022] <Cutting insert>

[0023] First, refer to Figure 1 and Figure 2 The specific structure of the cutting insert 1 according to the embodiment will be described. Figure 1 It is a perspective view showing an example of the cutting insert 1 according to the embodiment. Figure 2 It is a side sectional view showing an example of the cutting insert 1 according to the embodiment.

[0024] like Figure 1 As shown, the cutting insert 1 of the embodiment is a cutting insert for a cutting tool, for example, having an upper surface and a lower surface (with Figure 1 The shape of the surface (where the Z axis intersects) shown is a hexahedron of a parallelogram.

[0025] (Main body 2)

[0026] The cutting insert 1 of the embodiment includes: a main body 2; Figure 2 ) and is installed on the base 10 of the main body 2.

[0027] The main body 2 is formed of, for example, cemented carbide. Cemented carbide contains W (tungsten), specifically, WC (tungsten carbide). Cemented carbide may also contain Ni (nickel) or Co (cobalt). The main body 2 may also be formed of cermet. Cermet contains, for example, Ti (titanium), specifically, TiC (titanium carbide) or TiN (titanium nitride). Cermet may also contain Ni or Co.

[0028] The end of the main body 2 is provided with a support surface 4 for mounting the base 10. A through hole 5 is provided in the center of the main body 2, which passes through the main body 2 from top to bottom. A screw 75 (see FIG. 1 ) for mounting the cutting insert 1 on a tool holder 70 described later is inserted into the through hole 5. Figure 6 ).

[0029] (Base 10)

[0030] The base 10 is attached to the support surface 4 of the main body 2. Thus, the base 10 and the main body 2 are integrated.

[0031] The base 10 has a first surface 6 (here, the upper surface) and a second surface 7 (here, the side surface) connected to the first surface 6. In the embodiment, the first surface 6 functions as a "front face" for scraping off chips generated by cutting, and the second surface 7 functions as a "flank face". A cutting edge 8 is provided on at least a portion of the ridgeline where the first surface 6 and the second surface 7 intersect, and the cutting insert 1 cuts the workpiece by bringing the cutting edge 8 into contact with the workpiece.

[0032] The substrate 10 is a cubic boron nitride (cBN) sintered body (hereinafter referred to as “cBN sintered body”). cBN has a hardness second only to diamond and excellent chemical stability. The specific structure of the cBN sintered body constituting the substrate 10 will be described later.

[0033] like Figure 2As shown, a substrate 30 formed of, for example, cemented carbide or cermet may be provided on the lower surface of the substrate 10. In this case, the substrate 10 is bonded to the supporting surface 4 of the main body 2 via the substrate 30 and the bonding material 40. The bonding material 40 is, for example, brazing material. In the portion other than the supporting surface 4 of the main body 2, the substrate 10 may be bonded to the main body 2 via the bonding material 40.

[0034] In the embodiment, only the base body 10 as a part of the cutting insert 1 is composed of the cBN sintered body, but the entire cutting insert 1 may be composed of the cBN sintered body.

[0035] (Coating 20)

[0036] The substrate 10 may be covered with a coating 20. The coating 20 covers the substrate 10 for the purpose of improving the wear resistance and heat resistance of the substrate 10, for example. Figure 2 In the example, the coating 20 covers the main body 2 and the substrate 10 as a whole. It is not limited to this, and the coating 20 can be located on at least a portion of the surface of the substrate 10. This can improve the heat resistance and wear resistance of the substrate 10. The coating 20 can also be located on the upper surface of the main body 2. When the coating 20 is located on the upper surface of the substrate 10, the first surface 6 (refer to Figure 1 ) has high wear resistance and heat resistance. When the coating 20 is located on the side of the substrate 10, the second surface 7 (refer to Figure 1 )'s wear resistance and heat resistance.

[0037] Here, refer to Figure 3 , the specific structure of the coating 20 is described. Figure 3 It is a cross-sectional view showing an example of the coating layer 20 according to the embodiment.

[0038] like Figure 3 As shown, the coating 20 includes a hard layer 21. The hard layer 21 is a layer having better wear resistance than the metal layer 22 described later. The hard layer 21 has one or more metal nitride layers. The hard layer 21 may be a single layer. Figure 3 As shown, a plurality of metal nitride layers may be stacked. The hard layer 21 may include: a stacked portion 23 in which a plurality of metal nitride layers are stacked; and a third metal nitride layer 24 located on the stacked portion 23. The structure of the hard layer 21 will be described later.

[0039] (Metal layer 22)

[0040] The coating layer 20 includes a metal layer 22. The metal layer 22 is located between the substrate 10 and the hard layer 21. Specifically, the metal layer 22 is in contact with the upper surface of the substrate 10 at one surface (here, the lower surface), and is in contact with the lower surface of the hard layer 21 at the other surface (here, the upper surface).

[0041] The metal layer 22 has a higher bonding property with the substrate 10 than with the hard layer 21. Examples of metal elements having such properties include Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, Si, and Y. The metal layer 22 contains at least one of the above metal elements. When the metal layer 22 contains at least one element selected from the group consisting of Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, Si, and Y, the bonding property between the substrate 10 and the coating layer 20 can be improved.

[0042] The simple substance of Ti, the simple substance of Zr, the simple substance of V, the simple substance of Cr and the simple substance of Al cannot be used as the metal layer 22. This is because they all have low melting points and low oxidation resistance, and are therefore not suitable for use in cutting tools. The simple substance of Hf, the simple substance of Nb, and the simple substance of Ta have low bonding with the substrate 10. However, there is no such limitation for alloys containing Ti, Zr, V, Cr, Ta, Nb, Hf or Al. Therefore, the metal layer 22 may contain metals other than the simple substances of Ti, Zr, V, Cr, Ta, Nb, Hf and Al. In this case, the oxidation resistance of the metal layer 22 and the bonding strength between the substrate 10 and the coating 20 can be improved.

[0043] The metal layer 22 may be an Al—Cr alloy layer containing an Al—Cr alloy. Such a metal layer 22 has particularly high bonding properties with the substrate 10 , and thus has a high effect of improving bonding properties between the substrate 10 and the coating layer 20 .

[0044] When the metal layer 22 is an Al-Cr alloy layer, the content of Al in the metal layer 22 may be greater than the content of Cr in the metal layer 22. For example, the composition ratio (atomic %) of Al to Cr in the metal layer 22 may be 70:30. By adopting such a composition ratio, the bonding between the substrate 10 and the metal layer 22 is higher.

[0045] The metal layer 22 may also contain components other than the above-mentioned metal elements (Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, Si and Y). However, from the viewpoint of bonding with the substrate 10, the metal layer 22 may contain at least 95 atomic % or more of the above-mentioned metal elements in total. The metal layer 22 may also contain 98 atomic % or more of the above-mentioned metal elements in total. For example, when the metal layer 22 is an Al-Cr alloy layer, the metal layer 22 may contain at least 95 atomic % or more of Al and Cr in total. The metal layer 22 may also contain at least 98 atomic % or more of Al and Cr in total. The proportion of the metal components in the metal layer 22 can be determined, for example, by analysis using EDS (energy dispersive X-ray spectrometer).

[0046] Since Ti has poor wettability with the substrate 10 of the embodiment, the metal layer 22 contains as little Ti as possible from the viewpoint of improving bonding with the substrate 10. Specifically, the content of Ti in the metal layer 22 may be 15 atomic % or less.

[0047] Thus, in the cutting insert 1 of the embodiment, the bonding property between the substrate 10 and the coating 20 can be improved by providing the metal layer 22 having higher wettability with the substrate 10 than with the hard layer 21 between the substrate 10 and the hard layer 21. Since the bonding property between the metal layer 22 and the hard layer 21 is also high, it is also difficult for the hard layer 21 to peel off from the metal layer 22.

[0048] The cBN used as the substrate 10 is an insulator, and the bonding between the cBN as an insulator and the film formed by the PVD method (physical vapor deposition) has room for improvement. In contrast, in the cutting insert 1 of the embodiment, since the conductive metal layer 22 is provided on the surface of the substrate 10, the bonding between the hard layer 21 formed by PVD and the metal layer 22 is high.

[0049] (Hard layer 21)

[0050] Next, refer to Figure 4 The structure of the hard layer 21 will be described. Figure 4 yes Figure 3 A schematic enlarged view of section H is shown.

[0051] like Figure 4 As shown, the hard layer 21 includes: a stacked portion 23 located on the metal layer 22 ; and a third metal nitride layer 24 located on the stacked portion 23 .

[0052] The stacked portion 23 includes a plurality of first metal nitride layers 23a and a plurality of second metal nitride layers 23b. The stacked portion 23 has a structure in which the first metal nitride layers 23a and the second metal nitride layers 23b are alternately stacked.

[0053] The thickness of the first metal nitride layer 23a and the second metal nitride layer 23b can be less than 50 nm, respectively. In this way, by forming the first metal nitride layer 23a and the second metal nitride layer 23b thinly, the residual stress of the first metal nitride layer 23a and the second metal nitride layer 23b is small. Therefore, for example, peeling or cracking of the first metal nitride layer 23a and the second metal nitride layer 23b is unlikely to occur, and thus the durability of the coating layer 20 is high.

[0054] The first metal nitride layer 23 a is a layer in contact with the metal layer 22 , and the second metal nitride layer 23 b is formed on the first metal nitride layer 23 a .

[0055] The first metal nitride layer 23 a and the second metal nitride layer 23 b may contain the metal contained in the metal layer 22 .

[0056] For example, two metals (here, "first metal" and "second metal") are included in the metal layer 22. In this case, the first metal nitride layer 23a contains nitrides of the first metal and the third metal. The third metal is a metal not included in the metal layer 22. In addition, the second metal nitride layer 23b contains nitrides of the first metal and the second metal.

[0057] For example, in the embodiment, the metal layer 22 may also contain Al and Cr. In this case, the first metal nitride layer 23a may contain Al. Specifically, the first metal nitride layer 23a may be an AlTiN layer containing AlTiN, which is a nitride of Al and Ti. The second metal nitride layer 23b may be an AlCrN layer containing AlCrN, which is a nitride of Al and Cr.

[0058] Thus, the first metal nitride layer 23a containing the metal contained in the metal layer 22 is located on the metal layer 22, so that the metal layer 22 and the hard layer 21 have high bonding properties. Therefore, the hard layer 21 is difficult to peel off from the metal layer 22, so the durability of the coating layer 20 is high.

[0059] The first metal nitride layer 23a, i.e., the AlTiN layer, has excellent wear resistance, for example, in addition to the above-mentioned bonding with the metal layer 22. The second metal nitride layer 23b, i.e., the AlCrN layer, has excellent heat resistance and oxidation resistance, for example. In this way, the coating 20 can control the properties of the hard layer 21, such as the wear resistance and heat resistance, by containing the first metal nitride layer 23a and the second metal nitride layer 23b having different compositions. Thus, the tool life of the cutting insert 1 can be extended. For example, in the hard layer 21 of the embodiment, it is possible to improve mechanical properties such as bonding with the metal layer 22 and wear resistance while maintaining the excellent heat resistance of AlCrN.

[0060] The laminated portion 23 can be formed, for example, by an arc ion plating method (AIP method). The AIP method is a method of evaporating a target metal (here, an AlTi target and an AlCr target) by arc discharge in a vacuum atmosphere, and forming a metal nitride (here, AlTiN and AlCrN) by combining with N2 gas. The metal layer 22 can also be formed by the AIP method.

[0061] The third metal nitride layer 24 may be located on the stacked portion 23. Specifically, the third metal nitride layer 24 is in contact with the second metal nitride layer 23b in the stacked portion 23. The third metal nitride layer 24 is, for example, a metal nitride layer (AlTiN layer) containing Ti and Al, similarly to the first metal nitride layer 23a.

[0062] The thickness of the third metal nitride layer 24 may be thicker than the thickness of the first metal nitride layer 23a and the second metal nitride layer 23b. Specifically, as described above, when the thickness of the first metal nitride layer 23a and the second metal nitride layer 23b is 50nm or less, the thickness of the third metal nitride layer 24 may be 1μm or more. For example, the thickness of the third metal nitride layer 24 may be 1.2μm.

[0063] Thus, for example, when the friction coefficient of the third metal nitride layer 24 is low, the anti-sticking property of the cutting insert 1 can be improved. For example, when the hardness of the third metal nitride layer 24 is high, the wear resistance of the cutting insert 1 can be improved. For example, when the oxidation start temperature of the third metal nitride layer 24 is high, the oxidation resistance of the cutting insert 1 can be improved.

[0064] The thickness of the third metal nitride layer 24 may be thicker than the thickness of the laminated portion 23. Specifically, in the embodiment, when the thickness of the laminated portion 23 is 0.5 μm or less, the thickness of the third metal nitride layer 24 may be 1 μm or more. For example, when the thickness of the laminated portion 23 is 0.3 μm, the thickness of the third metal nitride layer 24 may be 1.2 μm. In this way, by making the third metal nitride layer 24 thicker than the laminated portion 23, the above-mentioned anti-adhesion and wear resistance and the like are improved more.

[0065] The thickness of the metal layer 22 may be, for example, not less than 0.1 μm and less than 0.6 μm. That is, the metal layer 22 may be thicker than the first metal nitride layer 23 a and the second metal nitride layer 23 b , and thinner than the stacked portion 23 .

[0066] <Structure of cBN sintered body>

[0067] Next, refer to Figure 5 , the structure of the cBN-based sintered body 11 constituting the substrate 10 of the embodiment will be described. Figure 5 This is a cross-sectional view showing an example of a cBN-based sintered body 11 constituting the substrate 10 according to the embodiment.

[0068] like Figure 5 As shown, the cBN-based sintered body 11 constituting the substrate 10 of the embodiment includes a plurality of cubic boron nitride (cBN) particles (hereinafter referred to as “cBN particles”) 12 and a binder phase 13. The cBN particles 12 are particles composed of cubic boron nitride (cBN).

[0069] The binder phase 13 refers to a portion other than the plurality of cBN particles 12 in the cBN sintered body 11. The binder phase 13 is located between the plurality of cBN particles 12. The binder phase 13 binds the plurality of cBN particles 12. That is, in the cBN sintered body 11, the plurality of cBN particles 12 are bound via the binder phase 13.

[0070] The binder phase 13 contains at least one compound selected from the group consisting of, for example, carbides (TiC) containing Ti, nitrides (TiN) containing Ti, carbonitrides (TiCN) containing Ti, borides containing Ti, Al, AlN, and Al2O3. Examples of borides containing Ti include titanium diboride (TiB2).

[0071] Such a binder phase 13 can more firmly bind a plurality of cBN particles 12. As a result, the detachment of the cBN particles 12 from the binder phase 13 and / or the occurrence of cracks in the cBN sintered body 11 can be reduced. As a result, the wear resistance and fracture resistance of the cutting insert 1 including the substrate 10 composed of the cBN sintered body 11 can be improved.

[0072] In the cross section of the cBN sintered body 11 of the embodiment, the length of the grain boundary between the plurality of cBN particles 12 and the binder phase 13 per unit area of ​​the plurality of cBN particles 12 is 3.2 μm. －1 above.

[0073] The cross section of the cBN sintered body 11 of the embodiment is not particularly limited, and may be any cross section of the cBN sintered body 11. For example, a cross section of the cBN sintered body 11 can be photographed using a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

[0074] By applying image analysis to the photograph of the cross section of the cBN sintered body 11, the length of the grain boundary between the plurality of cBN particles 12 and the binder phase 13 per unit area of ​​the plurality of cBN particles 12 in the cross section of the cBN sintered body 11 can be obtained. For the image analysis of the photograph of the cross section of the cBN sintered body 11, for example, image processing software such as Image J can be used.

[0075] First, by applying image analysis to a photograph of a cross section of the cBN sintered body 11, the cross-sectional area of ​​the cBN sintered body 11 (cross-sectional area of ​​the cBN sintered body 11) (μm 2) and the content rate (area %) of the plurality of cBN particles 12 in the cBN sintered body 11. The content rate of the plurality of cBN particles 12 in the cBN sintered body 11 is the ratio of the sum of the areas of the plurality of cBN particles 12 contained in the cross section of the cBN sintered body 11 to the area of ​​the cross section of the cBN sintered body 11 × 100. Next, the sum of the areas of the plurality of cBN particles 12 in the cross section of the cBN sintered body 11 (μm) is obtained by multiplying the cross-sectional area of ​​the cBN sintered body 11 by the content rate of the plurality of cBN particles 12 in the cBN sintered body 11 / 100. 2 ).

[0076] By applying image analysis to a photograph of the cross section of the cBN sintered body 11 , the total length (μm) of the grain boundaries between the plurality of cBN particles 12 and the binder phase 13 in the cross section of the cBN sintered body 11 is obtained.

[0077] Next, the lengths of the grain boundaries between the plurality of cBN particles 12 and the binder phase 13 per unit area of ​​the plurality of cBN particles 12 (μm) are obtained by dividing the sum of the lengths of the grain boundaries between the plurality of cBN particles 12 and the binder phase 13 by the sum of the areas of the plurality of cBN particles 12. －1 ).

[0078] The length of the boundary between the plurality of cBN particles 12 and the binder phase 13 per unit area of ​​the plurality of cBN particles 12 is 3.2 μm. －1 When the above, the contact area between the BN particles 12 and the binder phase 13 can be increased. That is, the dispersibility of the plurality of cBN particles 12 in the binder phase 13 can be improved. Thus, the bonding between the plurality of cBN particles 12 and the binder phase 13 can be improved. That is, the plurality of cBN particles 12 can be more firmly bonded (sintered) by the binder phase 13.

[0079] In other words, the bonding between the plurality of cBN particles 12 can be reduced. As a result, the detachment of the cBN particles 12 from the binder phase 13 and / or the occurrence of cracks in the cBN sintered body 11, which are thought to be generated from the bonding portion between the plurality of cBN particles 12, can be reduced. As a result, the wear resistance and fracture resistance of the cutting insert 1 including the base 10 composed of the cBN sintered body 11 can be improved.

[0080] In the cross section of the cBN sintered body 11 of the embodiment, the length of the grain boundary between the plurality of cBN particles 12 and the binder phase 13 per unit area of ​​the cBN sintered body 11 is 2.2 μm. －1 above.

[0081] By applying image analysis to a photograph of the cross section of the cBN based sintered body 11, the cross-sectional area (μm2 ) and the sum of the lengths of the grain boundaries between the plurality of cBN particles 12 and the binder phase 13 in the cross section of the cBN sintered body 11 (μm). Next, by dividing the sum of the lengths of the grain boundaries between the plurality of cBN particles 12 and the binder phase 13 by the cross-sectional area of ​​the cBN sintered body 11, the lengths of the grain boundaries between the plurality of cBN particles 12 and the binder phase 13 per unit area of ​​the cBN sintered body 11 (μm) are obtained. －1 ).

[0082] The length of the grain boundary between the plurality of cBN particles 12 and the binder phase 13 per unit area of ​​the cBN-based sintered body 11 is 2.2 μm －1 When the above, the contact area between the plurality of cBN particles 12 and the binder phase 13 can be increased. That is, the dispersibility of the plurality of cBN particles 12 in the binder phase 13 can be improved. Thus, the bonding between the plurality of cBN particles 12 and the binder phase 13 can be improved. That is, the plurality of cBN particles 12 can be more firmly bonded (sintered) by the binder phase 13.

[0083] In other words, the bonding between the plurality of cBN particles 12 can be reduced. As a result, the detachment of the cBN particles 12 from the binder phase 13 and / or the occurrence of cracks in the cBN sintered body 11, which are thought to be generated from the bonding portion between the plurality of cBN particles 12, can be reduced. As a result, the wear resistance and fracture resistance of the cutting insert 1 including the base 10 composed of the cBN sintered body 11 can be improved.

[0084] In the cross section of the cBN sintered body 11 of the embodiment, the content of the plurality of cBN particles 12 in the cBN sintered body 11 may be at least 60 area %. The content of the plurality of cBN particles 12 in the cBN sintered body 11 may be 65 area % or more. The content (area %) of the plurality of cBN particles 12 in the cBN sintered body 11 is obtained by applying image analysis to a photograph of the cross section of the cBN sintered body 11.

[0085] In the cross section of the cBN sintered body 11 of the embodiment, the content of the plurality of cBN particles 12 in the cBN sintered body 11 is 55 area % or more and 85 area % or less. When the content of the plurality of cBN particles 12 in the cBN sintered body 11 is 55 area % or more, the fracture resistance of the cutting insert 1 including the substrate 10 composed of the cBN sintered body 11 can be improved. When the content of the plurality of cBN particles 12 in the cBN sintered body 11 is 85 area % or less, the wear resistance of the cutting insert 1 including the substrate 10 composed of the cBN sintered body 11 can be improved.

[0086] <Method for producing cBN sintered body>

[0087] Next, an example of a method for producing the cBN sintered body 11 according to the embodiment will be described. The method for producing the cBN sintered body 11 is not limited to the method described below.

[0088] First, prepare 72-82 volume % TiN raw material powder, 13-23 volume % Al raw material powder, and 1-11 volume % Al2O3 raw material powder. Add an organic solvent to each prepared raw material powder. As an organic solvent, alcohols such as acetone or isopropyl alcohol (IPA) can be used. Thereafter, each raw material powder in the organic solvent is crushed and mixed with a ball mill for 20-24 hours. After each raw material powder is crushed and mixed, the organic solvent is evaporated to obtain a first mixed powder.

[0089] Next, add cBN powder having an average particle size of 2.0 to 4.5 μm to the obtained first mixed powder. Here, the volume ratio of the first mixed powder to the cBN powder is 22 to 32%: 68 to 78%. Add an organic solvent to the first mixed powder and the cBN powder. As the organic solvent, alcohols such as acetone or IPA can be used. Thereafter, the first mixed powder and the cBN powder in the organic solvent are crushed and mixed in a ball mill for 20 to 24 hours. After the first mixed powder and the cBN powder are crushed and mixed, the organic solvent is evaporated to obtain a second mixed powder.

[0090] Next, the obtained second mixed powder is subjected to heat treatment in a vacuum furnace at 650 to 1000° C. for 1 to 4 hours in a vacuum atmosphere, thereby obtaining a third mixed powder.

[0091] Next, an organic solvent is added to the obtained third mixed powder. As the organic solvent, an alcohol such as acetone or IPA is used. Thereafter, the third mixed powder in the organic solvent is crushed and mixed using a ball mill for 20 to 24 hours. After the third mixed powder is crushed and mixed, an organic binder is added to the third mixed powder in the organic solvent. As the organic binder, paraffin wax, acrylic resin, etc. can be used. Thereafter, the fourth mixed powder is obtained by evaporating the organic solvent.

[0092] In the process using a ball mill, a dispersant may be added as needed.

[0093] The fourth mixed powder is formed into a predetermined shape to obtain a compact. For the forming, a known method such as a uniaxial press or a cold isostatic press (CIP) can be used. The compact is heated at a predetermined temperature in the range of 500 to 1000° C. to evaporate and remove the organic binder, thereby obtaining a compact for firing.

[0094] Next, the sintered compact is placed in an ultrahigh pressure heating device and heated at a temperature of 1200 to 1500° C. for 15 to 30 minutes under a pressure of 4 to 6 GPa. Thus, the cBN-based sintered body 11 of the embodiment is obtained.

[0095] Thus, a cBN sintered body 11 can be obtained in which the length of the grain boundary between the plurality of cBN particles 12 and the binder phase 13 per unit area of ​​the plurality of cBN particles 12 in the cross section of the cBN sintered body 11 is 3.2 μm. －1 In addition, a cBN sintered body 11 can be obtained in which the length of the grain boundary between the plurality of cBN particles 12 and the binder phase 13 per unit area of ​​the cBN sintered body 11 is 2.2 μm in the cross section of the cBN sintered body 11. －1 In addition, a cBN sintered body 11 can be obtained, wherein the content of the plurality of cBN particles 12 in the cBN sintered body 11 is 55 area % or more and 85 area % or less in the cross section of the cBN sintered body 11. Using the obtained cBN sintered body 11, a cutting insert 1 including a substrate 10 can be obtained.

[0096] <Cutting tools>

[0097] Next, refer to Figure 6 The structure of a cutting tool including the above-mentioned cutting insert 1 will be described. Figure 6 It is a front view of an example of the cutting tool according to the embodiment.

[0098] like Figure 6 As shown, a cutting tool 100 according to the embodiment includes a cutting insert 1 and a tool holder 70 for fixing the cutting insert 1 .

[0099] The handle 70 is from the first end ( Figure 6 ) toward the second end ( Figure 6 The handle 70 is a rod-shaped member extending from the lower end of the handle 70. The handle 70 is made of, for example, steel or cast iron. Among these materials, particularly high toughness steel can be used.

[0100] The tool holder 70 has a slot 73 at the end of the first end. The slot 73 is a portion for assembling the cutting insert 1, and has a support surface intersecting the rotation direction of the cut material and a side surface that limits the inclination relative to the support surface. A screw hole for screwing a screw 75 described later is provided on the support surface.

[0101] The cutting insert 1 is located in the slot 73 of the tool holder 70 and is assembled to the tool holder 70 by means of a screw 75. That is, the screw 75 is inserted into the through hole 5 of the cutting insert 1, and the front end of the screw 75 is inserted into the screw hole formed on the support surface of the slot 73, so that the threaded parts are tightened. Thus, the cutting insert 1 is assembled to the tool holder 70 in a manner that the cutting edge 3 protrudes outward from the tool holder 70.

[0102] In the embodiment, a cutting tool for so-called turning processing is illustrated. As turning processing, for example, inner diameter processing, outer diameter processing and slotting processing can be listed. As a cutting tool, it is not limited to turning processing. For example, the cutting insert 1 can also be used as a cutting tool for hobbing processing. As a cutting tool for hobbing processing, for example, milling cutters such as flat milling cutters, front milling cutters, side milling cutters and slotting milling cutters, and end mills such as single-edge end mills, multi-edge end mills, tapered end mills and ball end mills can be listed.

[0103] For example, the cutting process of a workpiece includes the following steps: (1) a step of rotating the workpiece; (2) a step of bringing the cutting edge portion 3 of the cutting insert 1 into contact with the rotating workpiece to cut the workpiece; and (3) a step of separating the cutting insert 1 from the workpiece. Representative examples of the material of the workpiece include carbon steel, alloy steel, stainless steel, cast iron, or nonferrous metals.

[0104] Example

[0105] Hereinafter, examples of the present invention will be described, but the present invention is not limited to the following examples.

[0106] (Example)

[0107] The cBN-based sintered body of the example was produced in the following manner.

[0108] First, acetone and a dispersant were added to 77 volume % TiN raw material powder, 18 volume % Al raw material powder, and 5 volume % Al2O3 raw material powder, and the raw material powders in acetone were crushed and mixed for 24 hours using a ball mill. After the raw material powders were crushed and mixed, the acetone was evaporated to obtain a first mixed powder.

[0109] Next, cBN powder having an average particle size of 3 μm was added to the obtained first mixed powder. The volume ratio of the first mixed powder to the cBN powder was 27:73. After adding acetone and a dispersant to the first mixed powder and the cBN powder, the first mixed powder and the cBN powder in acetone were crushed and mixed with a ball mill for 24 hours. After the first mixed powder and the cBN powder were crushed and mixed, the acetone was evaporated to obtain a second mixed powder.

[0110] Next, the obtained second mixed powder was subjected to heat treatment in a vacuum furnace at a temperature of 800° C. in a vacuum atmosphere for 2 hours, thereby obtaining a third mixed powder.

[0111] Next, after adding acetone and a dispersant to the obtained third mixed powder, the third mixed powder in acetone was crushed and mixed with a ball mill for 24 hours. After the obtained third mixed powder was crushed and mixed, an organic binder was further added to the third mixed powder in acetone. Thereafter, the acetone was evaporated to obtain a fourth mixed powder.

[0112] Next, the fourth mixed powder was compacted by a uniaxial press to obtain a compact. The compact was heated at 800° C. to evaporate and remove the organic binder, thereby obtaining a compact for firing.

[0113] Next, the obtained sintered body was placed in an ultrahigh pressure heating device and heated at a temperature of 1350° C. for 20 minutes under a pressure of 5 GPa. Thus, a cBN-based sintered body of the example was obtained.

[0114] (Comparative Example)

[0115] A cBN-based sintered body of the comparative example was produced in the following manner.

[0116] First, acetone and a dispersant were added to 77 volume % TiN raw material powder, 18 volume % Al raw material powder, and 5 volume % Al2O3 raw material powder, and the raw material powders in acetone were crushed and mixed for 24 hours using a ball mill. After the raw material powders were crushed and mixed, the acetone was evaporated to obtain a fifth mixed powder.

[0117] Next, cBN powder having an average particle size of 3 μm was added to the obtained fifth mixed powder. The volume ratio of the fifth mixed powder to the cBN powder was 27:73. After adding acetone and a dispersant to the fifth mixed powder and the cBN powder, the fifth mixed powder and the cBN powder in the acetone were crushed and mixed with a ball mill for 24 hours. After the fifth mixed powder and the cBN powder were crushed and mixed, an organic binder was further added to the fifth mixed powder and the cBN powder in the acetone. Thereafter, the acetone was evaporated to obtain a sixth mixed powder.

[0118] Next, the obtained sixth mixed powder was compacted by a uniaxial press to obtain a compact. The obtained compact was heated at a temperature of 800° C. to evaporate and remove the organic binder, thereby obtaining a compact for firing.

[0119] Next, the obtained sintered compact was placed in an ultrahigh pressure heating device and heated at a temperature of 1350° C. for 20 minutes under a pressure of 5 GPa. Thus, a cBN-based sintered body of the comparative example was obtained.

[0120] (Image Analysis)

[0121] The obtained cBN sintered body of the example and the cBN sintered body of the comparative example were photographed by scanning electron microscope (SEM) to take cross-sectional photographs of the cBN sintered body. Here, cross-sectional photographs of the cBN sintered body of the example were taken in fields No. 1, No. 2, No. 3, and No. 4. Cross-sectional photographs of the cBN sintered body of the comparative example were taken in fields No. 1, No. 2, and No. 3.

[0122] Next, the cross-sectional photographs of the cBN sintered bodies of the examples and the comparative examples were analyzed using the image processing software Image J. The cross-sectional area (μm 2 ), the content of cBN particles in the cBN sintered body (area %), and the sum of the lengths of the grain boundaries between the cBN particles and the binder phase in the cross section of the cBN sintered body (μm).

[0123] The total area of ​​the cBN particles in the cross section of the cBN sintered body (μm) was calculated from the cross-sectional area of ​​the cBN sintered body and the content of the cBN particles in the cBN sintered body. 2 The length of the grain boundary between the cBN particles and the binder phase per unit area of ​​the cBN particles (μm) was calculated based on the sum of the lengths of the grain boundaries between the cBN particles and the binder phase and the sum of the areas of the cBN particles. －1 The length (μm) of the grain boundary between the cBN particles and the binder phase per unit area of ​​the cBN sintered body is calculated based on the sum of the lengths of the grain boundaries between the cBN particles and the binder phase and the cross-sectional area of ​​the cBN sintered body 11. －1 ).

[0124] Figure 7 The diagram shows the results of image analysis corresponding to the photographs of each cross section of the cBN sintered body of the example and the photographs of each cross section of the cBN sintered body of the comparative example.

[0125] like Figure 7 As shown, regarding each cross section of the cBN sintered body of the example, the length of the grain boundary between the cBN particles and the binder phase per unit area of ​​the cBN particles in the cross section of the cBN sintered body of the example is 3.2 μm. －1 As for each cross section of the cBN sintered body of the example, the length of the grain boundary between the cBN particles and the binder phase per unit area of ​​the cBN sintered body is 2.2 μm.－1 Regarding each cross section of the cBN sintered body of the example, the content of cBN particles in the cBN sintered body in the cross section of the cBN sintered body of the example was 55 area % or more and 85 area % or less.

[0126] On the other hand, Figure 7 As shown, regarding each cross section of the cBN sintered body of the comparative example, the length of the grain boundary between the cBN particles and the binder phase per unit area of ​​the cBN particles in the cross section of the cBN sintered body of the comparative example is less than 3.2 μm. －1 Regarding each cross section of the cBN sintered body of the comparative example, the length of the grain boundary between the cBN particles and the binder phase per unit area in the cross section of the cBN sintered body of the comparative example was less than 2.2 μm. －1 .

[0127] Figure 8 This is a partially enlarged view of a photograph of a cross section of field No. 1 of a cBN-based sintered body of an example. Fig. 9 This is a partially enlarged view of a photograph of a cross section of field No. 1 of a cBN-based sintered body of a comparative example.

[0128] like Figure 8 and Fig. 9 As shown, it can be confirmed that the contact area between the cBN particles and the binder phase of the cBN sintered body of the embodiment is larger than the contact area between the cBN particles and the binder phase of the cBN sintered body of the comparative example. In other words, it can be confirmed that the frequency of bonding between the cBN particles of the cBN sintered body of the embodiment is lower than the frequency of bonding between the cBN particles of the cBN sintered body of the comparative example. In other words, it can be confirmed that the dispersibility of the cBN particles in the binder phase of the cBN sintered body of the embodiment is higher than the dispersibility of the cBN particles in the binder phase of the cBN sintered body of the comparative example.

[0129] As described above, the cutting insert of the embodiment (as an example, the cutting insert 1) has a cubic boron nitride sintered body (as an example, a cBN sintered body 11) containing a plurality of cubic boron nitride particles (as an example, a plurality of cBN particles 12) and a binder phase (as an example, a binder phase 13) that binds the plurality of cubic boron nitride particles. In the cross section of the cubic boron nitride sintered body, the length of the grain boundary between the plurality of cubic boron nitride particles and the binder phase per unit area of ​​the plurality of cubic boron nitride particles is 3.2 μm. －1 above.

[0130] In the cross section of the cubic boron nitride sintered body, the length of the grain boundary between the plurality of cubic boron nitride particles and the binder phase per unit area of ​​the cubic boron nitride sintered body is 2.2 μm. －1 above.

[0131] In a cross section of the cubic boron nitride sintered body, a content rate of the plurality of cubic boron nitride particles in the cubic boron nitride sintered body is 55 area % or more and 85 area % or less.

[0132] This improves the dispersibility of the plurality of cBN particles in the binder phase, thereby improving the bonding between the plurality of cBN particles and the binder phase. Therefore, the wear resistance and fracture resistance of the cutting insert including the matrix composed of the cBN sintered body can be improved.

[0133] The cutting insert 1 of the embodiment may further include a coating layer (for example, the coating layer 20) located on the cBN sintered body 11. By including the coating layer, the wear resistance and the heat resistance can be further improved.

[0134] In the above embodiment, the example shown is a case where the shape of the upper surface and the lower surface of the cutting tool 100 is a parallelogram, but the shape of the upper surface and the lower surface of the cutting tool 100 may also be a rhombus or a square, etc. The shape of the upper surface and the lower surface of the cutting tool 100 may also be a triangle, a pentagon, a hexagon, etc.

[0135] The shape of the cutting tool 100 may be positive or negative. The positive type is a type in which the side surface is inclined relative to the central axis passing through the center of the upper surface and the center of the lower surface of the cutting tool 100, and the negative type is a type in which the side surface is parallel to the above central axis.

[0136] Note (1): A cutting insert comprising a cubic boron nitride sintered body comprising a plurality of cubic boron nitride particles and a binding phase for binding the plurality of cubic boron nitride particles, wherein in a cross section of the cubic boron nitride sintered body, a length of a grain boundary between the plurality of cubic boron nitride particles and the binding phase per unit area of ​​the plurality of cubic boron nitride particles is 3.2 μm －1 above.

[0137] Note (2): The cutting insert according to Note (1), wherein in a cross section of the cubic boron nitride sintered body, a length of a grain boundary between the plurality of cubic boron nitride particles and the binder phase per unit area of ​​the cubic boron nitride sintered body is 2.2 μm. －1 above.

[0138] Note (3): The cutting insert according to note (1) or (2), wherein, in a cross section of the cubic boron nitride sintered body, a content of the plurality of cubic boron nitride particles in the cubic boron nitride sintered body is 55 area % or more and 85 area % or less.

[0139] Note (4): The cutting insert according to any one of Notes (1) to (3), wherein the binder phase contains at least one compound selected from the group consisting of carbides containing Ti, nitrides containing Ti, carbonitrides containing Ti, borides containing Ti, Al, AlN and Al2O3.

[0140] Appendix (5): The cutting insert according to any one of Appendix (1) to (4), further comprising a coating layer located on at least a portion of the surface of the cubic boron nitride sintered body.

[0141] Note (6): The cutting insert according to Note (5), wherein the coating includes a hard phase and a metal layer located between the cubic boron nitride sintered body and the hard phase, and the metal layer contains a metal other than Ti, Zr, V, Cr, Ta, Nb, Hf and Al.

[0142] Note (7): The cutting insert according to Note (6), wherein the metal layer contains at least one element selected from the group consisting of Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, Si and Y.

[0143] Appendix (8): A cutting tool comprising a rod-shaped shank having a groove at an end thereof, and a cutting insert according to any one of Appendix (1) to (7) located in the groove.

[0144] More effects and variations can be easily derived by those skilled in the art. Therefore, the broader aspects of the present invention are not limited by the specific details and representative embodiments shown and described above. Therefore, various changes can be made without departing from the spirit or scope of the general inventive concept defined by the attached scope of the invention and its equivalents.

[0145] Description of Reference Numerals

[0146] 1 Cutting blade

[0147] 2 Main body

[0148] 3 cutting edge

[0149] 4 Support surface

[0150] 5Through holes

[0151] 6 Side 1

[0152] 7 Side 2

[0153] 8 cutting edges

[0154] 10 Matrix

[0155] 11cBN sintered body

[0156] 12cBN particles

[0157] 13 Adhesive phase

[0158] 20 coatings

[0159] 21Hard layer

[0160] 22 metal layers

[0161] 23Lamination

[0162] 23a First metal nitride layer

[0163] 23b Second metal nitride layer

[0164] 24Third metal nitride layer

[0165] 30 substrates

[0166] 40Jointing materials

[0167] 70 handle

[0168] 73 card slots

[0169] 75 screws

[0170] 100 cutting tools

Claims

1. A cutting insert comprising a cubic boron nitride sintered body, wherein the cubic boron nitride sintered body comprises a plurality of cubic boron nitride particles and a binding phase for binding the plurality of cubic boron nitride particles. In the cross section of the cubic boron nitride sintered body, the length of the grain boundary between the plurality of cubic boron nitride particles and the binder phase per unit area of ​​the plurality of cubic boron nitride particles is 3.2 μm. －1 above.

2. The cutting insert according to claim 1, wherein In the cross section of the cubic boron nitride sintered body, the length of the grain boundary between the plurality of cubic boron nitride particles and the binder phase per unit area of ​​the cubic boron nitride sintered body is 2.2 μm －1 above.

3. The cutting insert according to claim 1 or 2, wherein: In a cross section of the cubic boron nitride sintered body, a content rate of the plurality of cubic boron nitride particles in the cubic boron nitride sintered body is 55 area % or more and 85 area % or less.

4. The cutting insert according to any one of claims 1 to 3, wherein The binder phase contains at least one compound selected from the group consisting of carbides containing Ti, nitrides containing Ti, carbonitrides containing Ti, borides containing Ti, Al, AlN, and Al2O3.

5. The cutting insert according to any one of claims 1 to 4, wherein The invention further comprises a coating layer located on at least a part of the surface of the cubic boron nitride sintered body.

6. The cutting insert according to claim 5, wherein: The coating layer includes a hard phase and a metal layer located between the cubic boron nitride sintered body and the hard phase, wherein the metal layer contains a metal other than a single substance of Ti, Zr, V, Cr, Ta, Nb, Hf, and Al.

7. The cutting insert according to claim 6, wherein: The metal layer contains at least one element selected from the group consisting of Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, Si and Y.

8. A cutting tool comprising: A rod-shaped handle with a slot at the end; A cutting insert according to any one of claims 1 to 7 located in the groove.

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