Insert and cutting tool

Abstract

An insert according to the present disclosure comprises a cubic boron nitride sintered compact including a plurality of cubic boron nitride particles and a binding phase that bind the plurality of cubic boron nitride particles. In the cross-section of the cubic boron nitride sintered compact, the length of grain boundaries between the binding phase and the plurality of cubic boron nitride particles per unit area of the plurality of cubic boron nitride particles is 3.2 μm-1 or greater.

Description

Inserts and Cutting Tools CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to Japanese Patent Application No. 2022-103940, filed on June 28, 2022, the entire disclosure of which is incorporated herein by reference.

[0002] The present disclosure relates to an insert and a cutting tool.

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

[0004] Patent No. 6900590

[0005] An insert according to one embodiment of the present disclosure comprises a cubic boron nitride sintered body including a plurality of cubic boron nitride particles and a binder phase that binds the plurality of cubic boron nitride particles together, wherein 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 in a cross section of the cubic boron nitride sintered body is 3.2 μm or less. －１ That's all.

[0006] FIG. 1 is a perspective view showing an example of an insert according to an embodiment. FIG. 2 is a side cross-sectional view showing an example of an insert according to an embodiment. FIG. 3 is a cross-sectional view showing an example of a coating film according to an embodiment. FIG. 4 is a schematic enlarged view of portion H shown in FIG. 3. FIG. 5 is a cross-sectional view showing an example of a cBN sintered body constituting a substrate according to an embodiment. FIG. 6 is a front view showing an example of a cutting tool according to an embodiment. FIG. 7 is a diagram showing the results of image analysis of photographs of cross sections of a cBN sintered body according to an example and a cBN sintered body according to a comparative example. FIG. 8 is a partially enlarged view of a photograph of a cross section of field No. 1 in a cBN sintered body according to an example. FIG. 9 is a partially enlarged view of a photograph of a cross section of field No. 1 in a cBN sintered body according to a comparative example.

[0007] Hereinafter, modes for carrying out the insert and cutting tool according to the present disclosure (hereinafter referred to as "embodiments") will be described in detail with reference to the drawings. The insert and cutting tool according to the present disclosure are not limited to these embodiments. The embodiments can be appropriately combined within the scope of not causing contradictions in content. In the following embodiments, the same components are designated by the same reference numerals, and redundant explanations will be omitted.

[0008] In the following embodiments, expressions such as "constant," "orthogonal," "perpendicular," or "parallel" may be used, but these expressions do not necessarily mean "constant," "orthogonal," "perpendicular," or "parallel" in a strict sense. In other words, the above expressions allow for deviations due to, for example, manufacturing precision or installation precision.

[0009] Cubic boron nitride (cBN) has hardness second only to diamond and excellent chemical stability, and therefore cBN sintered bodies are widely used as cutting tools for machining ferrous metals such as hardened steel, cast iron, and sintered alloys.

[0010] The above-mentioned prior art has room for further improvement in terms of improving wear resistance and chipping resistance.

[0011] Therefore, there is a need for a technology that can overcome the above-mentioned problems and improve wear resistance and fracture resistance.

[0012] <Insert> First, a specific configuration of the insert 1 according to the embodiment will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is a perspective view showing an example of the insert 1 according to the embodiment. Fig. 2 is a side cross-sectional view showing an example of the insert 1 according to the embodiment.

[0013] As shown in FIG. 1, the insert 1 according to the embodiment is an insert for a cutting tool, and has, for example, a hexahedral shape in which the upper and lower surfaces (surfaces intersecting with the Z axis shown in FIG. 1) are parallelograms.

[0014] (Main Body 2) The insert 1 according to the embodiment includes the main body 2 and the base 10 attached to the main body 2 via a bonding material 40 (see FIG. 2) described later.

[0015] The main body 2 may be formed of, for example, a cemented carbide. The cemented carbide contains W (tungsten), specifically WC (tungsten carbide). The cemented carbide may contain Ni (nickel) or Co (cobalt). The main body 2 may be formed of a cermet. The cermet may contain, for example, Ti (titanium), specifically TiC (titanium carbide) or TiN (titanium nitride). The cermet may contain Ni or Co.

[0016] A seat 4 for attaching the base body 10 is located at the end of the main body 2. A through-hole 5 that passes through the main body 2 from top to bottom is located at the center of the main body 2. A screw 75 is inserted into the through-hole 5 to attach the insert 1 to a holder 70 (described later) (see FIG. 6).

[0017] (Base Body 10) The base body 10 is attached to the seat surface 4 of the main body portion 2. In this way, the base body 10 is integrated with the main body portion 2.

[0018] The base body 10 has a first surface 6 (here, an upper surface) and a second surface 7 (here, a side surface) that is connected to the first surface 6. In the embodiment, the first surface 6 functions as a "rake surface" that scoops up chips generated by cutting, and the second surface 7 functions as a "flank surface." A cutting edge 8 is located on at least a portion of the ridge where the first surface 6 and the second surface 7 intersect, and the insert 1 cuts the workpiece by bringing the cutting edge 8 into contact with the workpiece.

[0019] The substrate 10 is a cubic boron nitride (cBN) sintered body (hereinafter referred to as "cBN sintered body"). cBN has hardness second only to diamond and is excellent in chemical stability. The specific configuration of the cBN sintered body that constitutes the substrate 10 will be described later.

[0020] 2, a substrate 30 made of, for example, cemented carbide or cermet may be located on the underside of the base 10. In this case, the base 10 is joined to the seating surface 4 of the main body 2 via the substrate 30 and a joining material 40. The joining material 40 is, for example, a brazing material. The base 10 may be joined to the main body 2 via the joining material 40 in a portion other than the seating surface 4 of the main body 2.

[0021] In the embodiment, only the base 10, which is a part of the insert 1, is made of a cBN sintered body, but the entire insert 1 may be made of a cBN sintered body.

[0022] (Coating Film 20) The substrate 10 may be covered with a coating film 20. The coating film 20 coats the substrate 10, for example, to improve the abrasion resistance, heat resistance, and the like of the substrate 10. In the example of FIG. 2, the coating film 20 entirely covers the main body 2 and the substrate 10. However, the coating film 20 may be located on at least a portion of the surface of the substrate 10. In this case, the heat resistance and abrasion resistance of the substrate 10 can be improved. The coating film 20 may be located on the upper surface of the main body 2. When the coating film 20 is located on the upper surface of the substrate 10, the abrasion resistance and heat resistance of the first surface 6 (see FIG. 1) are high. When the coating film 20 is located on the side surface of the substrate 10, the abrasion resistance and heat resistance of the second surface 7 (see FIG. 1) are high.

[0023] Here, a specific configuration of the coating film 20 will be described with reference to Fig. 3. Fig. 3 is a cross-sectional view showing an example of the coating film 20 according to the embodiment.

[0024] As shown in FIG. 3 , the coating film 20 includes a hard layer 21. The hard layer 21 is a layer that has superior wear resistance compared to a 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. As shown in FIG. 3 , a plurality of metal nitride layers may be stacked. The hard layer 21 may have 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 configuration of the hard layer 21 will be described later.

[0025] (Metal Layer 22) The coating film 20 includes a metal layer 22. The metal layer 22 is located between the substrate 10 and the hard layer 21. Specifically, one surface (here, the lower surface) of the metal layer 22 contacts the upper surface of the substrate 10, and the other surface (here, the upper surface) of the metal layer 22 contacts the lower surface of the hard layer 21.

[0026] The metal layer 22 has higher adhesion to the substrate 10 than 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. In this way, 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 adhesion between the substrate 10 and the coating film 20 can be improved.

[0027] Simple elements such as Ti, Zr, V, Cr, and Al are not used for the metal layer 22. These elements have low melting points and poor oxidation resistance, making them unsuitable for use in cutting tools. Simple elements such as Hf, Nb, and Ta have poor adhesion to the substrate 10. However, this does not apply to alloys containing Ti, Zr, V, Cr, Ta, Nb, Hf, or Al. Therefore, the metal layer 22 may be made of a metal other than simple elements such as Ti, Zr, V, Cr, Ta, Nb, Hf, and Al. In this case, the oxidation resistance of the metal layer 22 and the adhesion between the substrate 10 and the coating film 20 can be improved.

[0028] The metal layer 22 may be an Al—Cr alloy layer containing an Al—Cr alloy. Such a metal layer 22 has particularly high adhesion to the substrate 10, and is therefore highly effective in improving adhesion between the substrate 10 and the coating film 20.

[0029] When the metal layer 22 is an Al—Cr alloy layer, the Al content in the metal layer 22 may be greater than the Cr content 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 setting such a composition ratio, the adhesion between the substrate 10 and the metal layer 22 is improved.

[0030] The metal layer 22 may contain components other than the above metal elements (Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, Si, and Y). However, from the viewpoint of adhesion to the substrate 10, the metal layer 22 may contain at least 95 atomic % or more of the above metal elements in total. The metal layer 22 may contain 98 atomic % or more of the above 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 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 spectrometry).

[0031] Since Ti has poor wettability with the base 10 according to the embodiment, the metal layer 22 may contain as little Ti as possible from the viewpoint of improving adhesion to the base 10. Specifically, the content of Ti in the metal layer 22 may be 15 atomic % or less.

[0032] In this way, in the insert 1 according to the embodiment, the metal layer 22, which has higher wettability with the substrate 10 than the hard layer 21, is provided between the substrate 10 and the hard layer 21, thereby improving the adhesion between the substrate 10 and the coating film 20. Since the metal layer 22 also has high adhesion with the hard layer 21, peeling of the hard layer 21 from the metal layer 22 is unlikely to occur.

[0033] The cBN used for the substrate 10 is an insulator, and as an insulator, there is room for improvement in the adhesion of cBN to a film formed by a PVD (physical vapor deposition) method. In contrast, in the insert 1 according to the embodiment, by providing the conductive metal layer 22 on the surface of the substrate 10, the adhesion between the hard layer 21 formed by PVD and the metal layer 22 is high.

[0034] (Hard Layer 21) Next, the configuration of the hard layer 21 will be described with reference to Fig. 4. Fig. 4 is a schematic enlarged view of the portion H shown in Fig. 3.

[0035] As shown in FIG. 4, the hard layer 21 has a laminated portion 23 located on the metal layer 22 and a third metal nitride layer 24 located on the laminated portion 23 .

[0036] The laminated portion 23 has a plurality of first metal nitride layers 23 a and a plurality of second metal nitride layers 23 b. The laminated portion 23 has a configuration in which the first metal nitride layers 23 a and the second metal nitride layers 23 b are alternately laminated.

[0037] The thickness of each of the first metal nitride layer 23 a and the second metal nitride layer 23 b may be 50 nm or less. By forming the first metal nitride layer 23 a and the second metal nitride layer 23 b thin in this manner, the residual stress of the first metal nitride layer 23 a and the second metal nitride layer 23 b is small. As a result, for example, peeling or cracking of the first metal nitride layer 23 a and the second metal nitride layer 23 b is less likely to occur, and therefore the durability of the coating film 20 is high.

[0038] The first metal nitride layer 23a is a layer in contact with the metal layer 22, and the second metal nitride layer 23b is formed on the first metal nitride layer 23a.

[0039] 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 .

[0040] For example, suppose that metal layer 22 contains two types of metals (here, a "first metal" and a "second metal"). In this case, first metal nitride layer 23a contains nitrides of the first metal and a third metal. The third metal is a metal not contained in metal layer 22. Furthermore, second metal nitride layer 23b contains nitrides of the first metal and the second metal.

[0041] For example, in an embodiment, the metal layer 22 may 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.

[0042] In this way, by positioning the first metal nitride layer 23a containing the metal contained in the metal layer 22 on the metal layer 22, adhesion between the metal layer 22 and the hard layer 21 is strong. This makes it difficult for the hard layer 21 to peel off from the metal layer 22, and therefore the durability of the coating film 20 is high.

[0043] The first metal nitride layer 23a, i.e., the AlTiN layer, has excellent adhesion to the metal layer 22, as described above, and also has excellent wear resistance, for example. The second metal nitride layer 23b, i.e., the AlCrN layer, has excellent heat resistance and oxidation resistance, for example. In this way, by including the first metal nitride layer 23a and the second metal nitride layer 23b with different compositions, the coating film 20 can control the properties of the hard layer 21, such as wear resistance and heat resistance. This can extend the tool life of the insert 1. For example, the hard layer 21 according to the embodiment can improve mechanical properties, such as adhesion to the metal layer 22 and wear resistance, while maintaining the excellent heat resistance of AlCrN.

[0044] The laminated portion 23 may be formed by, for example, an arc ion plating (AIP) method. The AIP method uses arc discharge in a vacuum atmosphere to evaporate target metals (here, an AlTi target and an AlCr target), and then, N ２ This is a method of depositing a metal nitride (here, AlTiN and AlCrN) by bonding with a gas. The metal layer 22 may also be deposited by the AIP method.

[0045] 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 of the stacked portion 23. The third metal nitride layer 24 is, for example, a metal nitride layer containing Ti and Al (AlTiN layer) similar to the first metal nitride layer 23a.

[0046] The thickness of the third metal nitride layer 24 may be thicker than the thicknesses of the first metal nitride layer 23 a and the second metal nitride layer 23 b. Specifically, when the thicknesses of the first metal nitride layer 23 a and the second metal nitride layer 23 b are 50 nm or less as described above, the thickness of the third metal nitride layer 24 may be 1 μm or more. For example, the thickness of the third metal nitride layer 24 may be 1.2 μm.

[0047] As a result, for example, when the friction coefficient of the third metal nitride layer 24 is low, the adhesion resistance of the insert 1 can be improved. For example, when the hardness of the third metal nitride layer 24 is high, the wear resistance of the insert 1 can be improved. For example, when the oxidation onset temperature of the third metal nitride layer 24 is high, the oxidation resistance of the insert 1 can be improved.

[0048] 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 effects of improving the above-mentioned welding resistance, wear resistance, etc. are further enhanced.

[0049] The thickness of metal layer 22 may be, for example, 0.1 μm or more and less than 0.6 μm. That is, metal layer 22 may be thicker than each of first metal nitride layer 23 a and second metal nitride layer 23 b, and thinner than stack portion 23.

[0050] <Configuration of cBN sintered body> Next, the configuration of the cBN sintered body 11 constituting the base body 10 according to the embodiment will be described with reference to Fig. 5. Fig. 5 is a cross-sectional view showing an example of the cBN sintered body 11 constituting the base body 10 according to the embodiment.

[0051] 5, a cBN sintered body 11 constituting a substrate 10 according to 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 made of cubic boron nitride (cBN).

[0052] The binder phase 13 refers to the portion of the cBN sintered body 11 other than the plurality of cBN particles 12. The binder phase 13 is located between the plurality of cBN particles 12. The binder phase 13 bonds the plurality of cBN particles 12. That is, in the cBN sintered body 11, the plurality of cBN particles 12 are bonded via the binder phase 13.

[0053] The binder phase 13 may be, for example, a carbide containing Ti (TiC), a nitride containing Ti (TiN), a carbonitride containing Ti (TiCN), a boride containing Ti, Al, AlN, and Al ２ O ３ The boride containing Ti includes at least one compound selected from the group consisting of: ２ ) are listed.

[0054] Such a binder phase 13 can more firmly bind the plurality of cBN particles 12 together, thereby reducing the shedding of the cBN particles 12 from the binder phase 13 and / or the occurrence of cracks in the cBN sintered body 11. This improves the wear resistance and fracture resistance of the insert 1 including the substrate 10 made of the cBN sintered body 11.

[0055] In the cross section of the cBN sintered material 11 according to the embodiment, the length of the grain boundary between the cBN particles 12 and the binder phase 13 per unit area of ​​the cBN particles 12 is 3.2 μm. －１ That's all.

[0056] The cross section of the cBN sintered material 11 according to the embodiment is not particularly limited and may be any cross section of the cBN sintered material 11. For example, a photograph of the cross section of the cBN sintered material 11 can be taken with a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

[0057] By applying image analysis to the photograph of the cross section of the cBN sintered body 11, it is possible to obtain 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. For image analysis of the photograph of the cross section of the cBN sintered body 11, image processing software such as Image J can be used.

[0058] First, by applying image analysis to a photograph of the cross section of the cBN sintered body 11, the area of ​​the cross section of the cBN sintered body 11 (cross-sectional area of ​​the cBN sintered body 11) (μm ２ ) and the content (area %) of the plurality of cBN particles 12 in the cBN sintered body 11 are obtained. The content 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 cross section of the cBN sintered body 11 × 100. Next, the cross section area of ​​the cBN sintered body 11 is multiplied by the content of the plurality of cBN particles 12 in the cBN sintered body 11 / 100 to obtain the sum of the areas (μm ２ ) is obtained.

[0059] By applying image analysis to a photograph of the cross section of the cBN sintered material 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 material 11 is obtained.

[0060] Next, the total length of the grain boundaries between the plurality of cBN particles 12 and the binder phase 13 as described above is divided by the total area of ​​the plurality of cBN particles 12 as described above, thereby obtaining the length (μm －１ ) is obtained.

[0061] 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. －１In the above cases, 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. This can improve the bonding between the plurality of cBN particles 12 and the binder phase 13. That is, the plurality of cBN particles 12 can be more firmly bonded (sintered) by the binder phase 13.

[0062] In other words, it is possible to reduce bonding between the plurality of cBN particles 12. As a result, it is possible to reduce shedding 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 arise from the bonding portions between the plurality of cBN particles 12. This makes it possible to improve the wear resistance and fracture resistance of the insert 1 including the substrate 10 made of the cBN sintered body 11.

[0063] In the cross section of the cBN sintered material 11 according to 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 material 11 is 2.2 μm. －１ It may be more than that.

[0064] By applying image analysis to the photograph of the cross section of the cBN sintered body 11, the cross-sectional area (μm ２ ) and the sum (μm) 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. Next, the sum of the lengths of the grain boundaries between the plurality of cBN particles 12 and the binder phase 13 as described above is divided by the cross-sectional area of ​​the cBN sintered body 11 to obtain the length (μm) 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. －１ ) is obtained.

[0065] The length of the grain boundary between the cBN particles 12 and the binder phase 13 per unit area of ​​the cBN sintered body 11 is 2.2 μm. －１In the above cases, 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. This can improve the bonding between the plurality of cBN particles 12 and the binder phase 13. That is, the plurality of cBN particles 12 can be more firmly bonded (sintered) by the binder phase 13.

[0066] In other words, it is possible to reduce bonding between the plurality of cBN particles 12. As a result, it is possible to reduce shedding 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 arise from the bonding portions between the plurality of cBN particles 12. This makes it possible to improve the wear resistance and fracture resistance of the insert 1 including the substrate 10 made of the cBN sintered body 11.

[0067] In the cross section of the cBN sintered material 11 according to the embodiment, the content of the cBN particles 12 in the cBN sintered material 11 may be at least 60 area % or more. The content of the cBN particles 12 in the cBN sintered material 11 may be 65 area % or more. By applying image analysis to a photograph of the cross section of the cBN sintered material 11, the content (area %) of the cBN particles 12 in the cBN sintered material 11 is obtained.

[0068] In the cross section of the cBN sintered body 11 according to the embodiment, the content of the plurality of cBN particles 12 in the cBN sintered body 11 may be 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 chipping resistance of the insert 1 including the substrate 10 made 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 insert 1 including the substrate 10 made of the cBN sintered body 11 can be improved.

[0069] <Method for Manufacturing cBN Sintered Material> Next, an example of a method for manufacturing the cBN sintered material 11 according to the embodiment will be described. The method for manufacturing the cBN sintered material 11 is not limited to the method described below.

[0070] First, a mixture of 72 to 82 volume % TiN raw material powder, 13 to 23 volume % Al raw material powder, and 1 to 11 volume % Al ２ O ３ Raw material powders are prepared. An organic solvent is added to each of the prepared raw material powders. The organic solvent can be acetone or an alcohol such as isopropyl alcohol (IPA). Then, the raw material powders in the organic solvent are pulverized and mixed in a ball mill for 20 to 24 hours. After the raw material powders are pulverized and mixed, the organic solvent is evaporated to obtain a first mixed powder.

[0071] Next, cBN powder having an average particle size of 2.0 to 4.5 μm is added 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%. An organic solvent is added to the first mixed powder and the cBN powder. The organic solvent can be acetone or an alcohol such as IPA. Then, the first mixed powder and the cBN powder are pulverized and mixed in the organic solvent in a ball mill for 20 to 24 hours. After the first mixed powder and the cBN powder are pulverized and mixed, the organic solvent is evaporated to obtain a second mixed powder.

[0072] Next, the obtained second mixed powder is heat-treated in a vacuum furnace at 650 to 1000° C. for 1 to 4 hours in a vacuum atmosphere to obtain a third mixed powder.

[0073] Next, an organic solvent is added to the obtained third mixed powder. As the organic solvent, acetone or an alcohol such as IPA can be used. Then, the third mixed powder in the organic solvent is pulverized and mixed in a ball mill for 20 to 24 hours. After the third mixed powder is pulverized and mixed, an organic binder is added to the third mixed powder in the organic solvent. As the organic binder, paraffin, acrylic resin, or the like can be used. Then, the organic solvent is evaporated to obtain a fourth mixed powder.

[0074] In the step using a ball mill, a dispersant may be added as needed.

[0075] The fourth mixed powder is molded into a predetermined shape to obtain a molded body. For molding, known methods such as uniaxial pressing or cold isostatic pressing (CIP) can be used. The molded body is heated at a predetermined temperature within a range of 500 to 1000°C to evaporate and remove the organic binder, thereby obtaining a molded body for firing.

[0076] Next, the compact to be fired is placed in an ultra-high pressure heating apparatus and heated at a temperature of 1200 to 1500° C. under a pressure of 4 to 6 GPa for 15 to 30 minutes, thereby obtaining the cBN sintered body 11 according to the embodiment.

[0077] In this way, in 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 is 3.2 μm －１ As described above, the cBN sintered material 11 can be obtained. In addition, in the cross section of the cBN sintered material 11, 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 material 11 is 2.2 μm. －１ As described above, the cBN sintered body 11 can be obtained. The cBN sintered body 11 can be obtained so that the content of the plurality of cBN grains 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. The obtained cBN sintered body 11 can be used to obtain the insert 1 including the substrate 10.

[0078] <Cutting Tool> Next, the configuration of a cutting tool 100 including the insert 1 described above will be described with reference to Fig. 6. Fig. 6 is a front view showing an example of the cutting tool 100 according to an embodiment.

[0079] As shown in FIG. 6 , a cutting tool 100 according to the embodiment includes an insert 1 and a holder 70 for fixing the insert 1 .

[0080] The holder 70 is a rod-shaped member extending from a first end (the upper end in FIG. 6 ) to a second end (the lower end in FIG. 6 ). The holder 70 is made of, for example, steel or cast iron. Steel, which has high toughness among these materials, may be used.

[0081] The holder 70 has a pocket 73 at the end on the first end side. The pocket 73 is a portion where the insert 1 is attached, and has a seating surface that intersects with the rotation direction of the workpiece and a constraint side surface that is inclined relative to the seating surface. The seating surface is provided with a screw hole into which a screw 75, which will be described later, is threaded.

[0082] The insert 1 is positioned in the pocket 73 of the holder 70 and attached to the holder 70 by a screw 75. That is, the screw 75 is inserted into the through hole 5 of the insert 1, and the tip of the screw 75 is inserted into a threaded hole formed in the seating surface of the pocket 73 to screw the threaded portions together. In this way, the insert 1 is attached to the holder 70 so that the cutting edge portion 3 protrudes outward from the holder 70.

[0083] In the embodiment, a cutting tool used for so-called turning is exemplified. Examples of turning include internal diameter machining, external diameter machining, and grooving. The cutting tool is not limited to that used for turning. For example, the insert 1 may be used in a cutting tool used for milling. Examples of cutting tools used for milling include milling cutters such as flat milling cutters, face milling cutters, side milling cutters, and groove milling cutters, and end mills such as single-blade end mills, multi-blade end mills, tapered-blade end mills, and ball end mills.

[0084] For example, cutting of a workpiece includes (1) a step of rotating the workpiece, (2) a step of bringing the cutting edge portion 3 of the insert 1 into contact with the rotating workpiece to cut the workpiece, and (3) a step of separating the insert 1 from the workpiece. Representative examples of the material of the workpiece include carbon steel, alloy steel, stainless steel, cast iron, and non-ferrous metals.

[0085] Examples of the present disclosure will be described below, but the present disclosure is not limited to the following examples.

[0086] EXAMPLES A cBN sintered body according to an example was produced as follows.

[0087] First, 77% by volume of TiN raw material powder, 18% by volume of Al raw material powder, and 5% by volume of Al ２ O ３After adding acetone and a dispersant to the raw material powders, the raw material powders were pulverized and mixed in acetone for 24 hours in a ball mill. After the pulverization and mixing of the raw material powders, the acetone was evaporated to obtain a first mixed powder.

[0088] Next, cBN powder with 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 were crushed and mixed in acetone in a ball mill for 24 hours. After crushing and mixing the first mixed powder and the cBN powder, the acetone was evaporated to obtain a second mixed powder.

[0089] Next, the obtained second mixed powder was subjected to heat treatment in a vacuum furnace at a temperature of 800° C. for 2 hours in a vacuum atmosphere, thereby obtaining a third mixed powder.

[0090] Next, acetone and a dispersant were added to the obtained third mixed powder, and then the third mixed powder in acetone was pulverized and mixed in a ball mill for 24 hours. After the obtained third mixed powder was pulverized and mixed, an organic binder was further added to the third mixed powder in acetone. Then, the acetone was evaporated to obtain a fourth mixed powder.

[0091] Next, the fourth mixed powder was uniaxially pressed to obtain a green body, which was then heated at 800°C to evaporate and remove the organic binder, thereby obtaining a green body to be fired.

[0092] Next, the obtained molded body for sintering was placed in an ultra-high pressure heating apparatus and heated at a temperature of 1350° C. under a pressure of 5 GPa for 20 minutes, thereby obtaining a cBN sintered body according to the example.

[0093] Comparative Example A cBN sintered body according to a comparative example was produced as follows.

[0094] First, 77% by volume of TiN raw material powder, 18% by volume of Al raw material powder, and 5% by volume of Al ２ O ３After adding acetone and a dispersant to the raw material powders, the raw material powders were pulverized and mixed in acetone for 24 hours in a ball mill. After the pulverization and mixing of the raw material powders, the acetone was evaporated to obtain a fifth mixed powder.

[0095] 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 acetone were crushed and mixed in a ball mill for 24 hours. After crushing and mixing the fifth mixed powder and the cBN powder, an organic binder was further added to the fifth mixed powder and the cBN powder in acetone. Then, the acetone was evaporated to obtain a sixth mixed powder.

[0096] Next, the sixth mixed powder was uniaxially pressed to obtain a green body, which was then heated at 800°C to evaporate and remove the organic binder, thereby obtaining a green body to be fired.

[0097] Next, the obtained molded body for sintering was placed in an ultra-high pressure heating apparatus and heated at a temperature of 1350° C. under a pressure of 5 GPa for 20 minutes, thereby obtaining a cBN sintered body according to the comparative example.

[0098] (Image Analysis) Photographs of the cross sections of the obtained cBN sintered bodies according to the Examples and the Comparative Examples were taken using a scanning electron microscope (SEM). Photographs of the cross sections of the cBN sintered bodies according to the Examples were taken at visual fields No. 1, No. 2, No. 3, and No. 4. Photographs of the cross sections of the cBN sintered bodies according to the Comparative Examples were taken at visual fields No. 1, No. 2, and No. 3.

[0099] Next, image analysis was performed on the photographs of the cross sections of the cBN sintered bodies according to the examples and the comparative examples using image processing software Image J. By performing image analysis on the photographs of the cross sections of the cBN sintered bodies, the cross-sectional area (μm ２), the content (area %) of cBN particles in the cBN sintered body, and the sum of the lengths (μm) of the grain boundaries between the cBN particles and the binder phase in the cross section of the cBN sintered body were obtained.

[0100] From the cross-sectional area of ​​the cBN sintered body and the content of cBN particles in the cBN sintered body, the total area of ​​the cBN particles in the cross section of the cBN sintered body (μm ２ The length of the grain boundary between the cBN particle and the binder phase per unit area of ​​the cBN particle (μm －１ The length of the grain boundary between the cBN grains and the binder phase per unit area of ​​the cBN sintered body (μm －１ ) was obtained.

[0101] FIG. 7 shows the results of image analysis of photographs of cross sections of the cBN sintered body according to the example and the cBN sintered body according to the comparative example.

[0102] As shown in FIG. 7, for each cross section of the cBN sintered body according to the example, the length of the grain boundary between the cBN particle and the binder phase per unit area of ​​the cBN particle in the cross section of the cBN sintered body according to the example was 3.2 μm. －１ For each cross section of the cBN sintered body according to the example, the length of the grain boundary between the cBN grain and the binder phase per unit area of ​​the cBN sintered body in the cross section of the cBN sintered body according to the example was 2.2 μm. －１ For each cross section of the cBN sintered body according to the example, the content of cBN particles in the cross section of the cBN sintered body according to the example was 55 area % or more and 85 area % or less.

[0103] On the other hand, as shown in FIG. 7, for each cross section of the cBN sintered body according to the comparative example, the length of the grain boundary between the cBN particle and the binder phase per unit area of ​​the cBN particle in the cross section of the cBN sintered body according to the comparative example is 3.2 μm. －１For each cross section of the cBN sintered body according to the comparative example, the length of the grain boundary between the cBN grains and the binder phase per unit area of ​​the cBN sintered body in the cross section of the cBN sintered body according to the comparative example was less than 2.2 μm. －１ It was less than.

[0104] Fig. 8 is a partially enlarged view of a photograph of a cross section of a cBN sintered body according to an example, taken in field No. 1. Fig. 9 is a partially enlarged view of a photograph of a cross section of a cBN sintered body according to a comparative example, taken in field No. 1.

[0105] 8 and 9, it was confirmed that the contact area between the cBN particles and the binder phase in the cBN sintered bodies of the Examples was larger than that in the cBN sintered bodies of the Comparative Examples. That is, it was confirmed that the frequency of bonding between cBN particles in the cBN sintered bodies of the Examples was lower than that in the cBN sintered bodies of the Comparative Examples. In other words, it was confirmed that the dispersibility of cBN particles in the binder phase in the cBN sintered bodies of the Examples was higher than that in the binder phase in the cBN sintered bodies of the Comparative Examples.

[0106] As described above, the insert according to the embodiment (insert 1 as an example) comprises a cubic boron nitride sintered body (cBN sintered body 11 as an example) including a plurality of cubic boron nitride particles (cBN particles 12 as an example) and a binder phase (binder phase 13 as an example) that binds the plurality of cubic boron nitride particles together. 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 That's all.

[0107] In the cross section of the cubic boron nitride sintered body, the length of the grain boundary between the cubic boron nitride particles and the binder phase per unit area of ​​the cubic boron nitride sintered body is 2.2 μm. －１ That's all.

[0108] In the cross section of the cubic boron nitride sintered body, the 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.

[0109] This improves the dispersion of the cBN particles in the binder phase, thereby improving the bonding between the cBN particles and the binder phase, thereby improving the wear resistance and fracture resistance of the insert including the substrate made of a cBN sintered body.

[0110] The insert 1 according to the embodiment may further have a coating film (for example, a coating film 20) located on the cBN sintered body 11. By having the coating film, the wear resistance and heat resistance can be further improved.

[0111] In the above-described embodiment, an example has been shown in which the shapes of the upper and lower surfaces of the cutting tool 100 are parallelograms, but the shapes of the upper and lower surfaces of the cutting tool 100 may be rhombic, square, etc. The shapes of the upper and lower surfaces of the cutting tool 100 may be triangular, pentagonal, hexagonal, etc.

[0112] The shape of cutting tool 100 may be a positive type or a negative type. A positive type is a type in which the side surfaces are inclined with respect to a central axis passing through the centers of the upper and lower surfaces of cutting tool 100, and a negative type is a type in which the side surfaces are parallel to the central axis.

[0113] Supplementary Note (1): A cubic boron nitride sintered body comprising a plurality of cubic boron nitride particles and a binder phase binding the plurality of cubic boron nitride particles, wherein 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 in a cross section of the cubic boron nitride sintered body is 3.2 μm －１ Supplementary note (2): In a 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 or less. －１The insert according to Supplementary Note (1), wherein the above-mentioned. Supplementary Note (3): The insert according to Supplementary Note (1) or (2), wherein the 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 in a cross section of the cubic boron nitride sintered body. Supplementary Note (4): The binder phase is selected from the group consisting of carbides containing Ti, nitrides containing Ti, carbonitrides containing Ti, borides containing Ti, Al, AlN, and Al. ２ O ３ An insert according to any one of Appendices (1) to (3), containing at least one compound selected from the group consisting of: Appendix (5): An insert according to any one of Appendices (1) to (4), further comprising a coating film located on at least a portion of the surface of the cubic boron nitride sintered body. Appendix (6): An insert according to Appendices (5), wherein the coating film includes a hard phase and a metal layer located between the cubic boron nitride sintered body and the hard phase, the metal layer consisting of a metal other than Ti, Zr, V, Cr, Ta, Nb, Hf, and Al. Appendix (7): An insert according to Appendices (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. Appendix (8): A cutting tool comprising a rod-shaped holder having a pocket at an end thereof, and the insert according to any one of Appendices (1) to (7) located in the pocket.

[0114] Further advantages and / or modifications may readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

[0115] REFERENCE SIGNS LIST 1 insert 2 main body 3 cutting edge portion 4 bearing surface 5 through hole 6 first surface 7 second surface 8 cutting edge 10 substrate 11 cBN sintered body 12 cBN particles 13 binder phase 20 coating film 21 hard layer 22 metal layer 23 laminated portion 23a first metal nitride layer 23b second metal nitride layer 24 third metal nitride layer 30 substrate 40 bonding material 70 holder 73 pocket 75 screw 100 cutting tool

Claims

1. Cubic boron nitride sintered body comprising a plurality of cubic boron nitride particles and a binder phase binding the plurality of cubic boron nitride particles Equipped with In a 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 That's all. insert.

2. In a 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 That's all. The insert according to claim 1.

3. 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 in a cross section of the cubic boron nitride sintered body; The insert according to claim 1.

4. The binder phase may be selected from the group consisting of Ti-containing carbides, Ti-containing nitrides, Ti-containing carbonitrides, Ti-containing borides, Al, AlN, and Al. ２ O ３ Contains at least one compound selected from the group consisting of The insert according to claim 1.

5. A coating film located on at least a portion of the surface of the cubic boron nitride sintered body. Further comprising: The insert according to claim 1.

6. The coating film is A hard phase, and A metal layer located between the cubic boron nitride sintered body and the hard phase. Including, The metal layer is made of a metal other than Ti, Zr, V, Cr, Ta, Nb, Hf, and Al. The insert according to claim 5.

7. 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. The insert according to claim 6.

8. a rod-shaped holder having a pocket at one end; An insert according to any one of claims 1 to 7 located within the pocket; A cutting tool comprising: