Cubic boron nitride sintered bodies and coated cubic boron nitride sintered bodies, and tools having the same.

Abstract

The present invention aims to provide cubic boron nitride sintered bodies and coated cubic boron nitride sintered bodies, as well as tools having the same, which have excellent wear resistance and fracture resistance and can extend tool life. [Solution] A sintered cubic boron nitride body comprising cubic boron nitride and a binder phase, wherein in the cross-sectional structure, the content ratios of cubic boron nitride and the binder phase are within a predetermined range, the binder phase comprises an Al compound phase containing a predetermined compound and a Ti compound phase containing a predetermined compound, the Ti compound phase comprises a composite compound phase containing a predetermined compound, the content ratios of the Al compound phase and the Ti compound phase relative to the entire binder phase are within a predetermined range, and in the range from the interface between cubic boron nitride and the binder phase to a distance of 300 nm toward the binder phase, the content ratio X2 of the composite compound phase relative to the entire binder phase is greater than the content ratio X1 of the composite compound phase relative to the entire binder phase.

Description

[Technical Field]

[0001] The present invention relates to cubic boron nitride sintered bodies, coated cubic boron nitride sintered bodies, and tools having the same. [Background technology]

[0002] A cubic boron nitride sintered body contains cubic boron nitride and a binder phase. Conventionally, cubic boron nitride sintered bodies containing a Ti compound as the binder phase material have been widely used as tools for cutting iron-based workpieces such as steel and cast iron. This is because cubic boron nitride sintered bodies containing a Ti compound have low affinity with iron-based workpieces and excellent reactive wear resistance. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2021 / 010476 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, conventional cubic boron nitride sintered bodies containing Ti compounds have the problem of low thermal conductivity and toughness.

[0005] Furthermore, in recent years, cutting processes have seen increased speed, higher feed rates, and deeper cuts, requiring improved thermal shock resistance of tools compared to conventional methods. In particular, in recent years, when coolant is used in intermittent cutting of carburized and hardened steel, the cutting temperature changes rapidly. Under such harsh cutting conditions, conventional tools are prone to chipping due to thermal shock, which can trigger breakage of coated cutting tools and thus shorten tool life.

[0006] Against this backdrop, Patent Document 1 discloses a cubic boron nitride sintered body that has a long tool life even in high-efficiency machining of high-strength hardened steel, by having a bonding phase that includes first and second bonding particles comprising a compound of titanium and a predetermined element. However, because the bonding phase described in Patent Document 1 includes second bonding particles, the thermal conductivity of the cubic boron nitride sintered body decreases, and in machining where the cutting temperature changes rapidly, the thermal shock resistance is insufficient, and there is room for improvement in fracture resistance.

[0007] The present invention aims to provide cubic boron nitride sintered bodies and coated cubic boron nitride sintered bodies, as well as tools having the same, which have excellent wear resistance and fracture resistance and can extend tool life. [Means for solving the problem]

[0008] The inventors of the present invention have conducted extensive research on extending tool life and have discovered that in a cubic boron nitride sintered body containing a Ti compound, by unevenly distributing a composite compound phase, which has excellent toughness but poor thermal conductivity, near the surface of cubic boron nitride particles, which have excellent thermal conductivity, it is possible to improve toughness without reducing the thermal shock resistance of the cubic boron nitride sintered body. As a result, tool life can be extended, and thus the present invention has been completed.

[0009] <1> A cubic boron nitride sintered body comprising cubic boron nitride and a bonding phase, When the cross-sectional structure of the cubic boron nitride sintered body was observed, the content of cubic boron nitride was 10.0 area% to 60.0 area% of the total 100 area% of the cubic boron nitride sintered body, and the content of the binding phase was 40.0 area% to 90.0 area%. The bonded phase comprises an Al compound phase and a Ti compound phase. The Al compound phase comprises a compound of Al and at least one element selected from the group consisting of C, N, O, and B. The Ti compound phase includes at least one compound selected from the group consisting of Ti and at least one element selected from the group consisting of C, N, O, and B, and Ti and at least one element selected from the group consisting of V, Cr, Zr, Nb, Mo, Hf, Ta, and W, and at least one element selected from the group consisting of C, N, O, and B. The Ti compound phase includes a composite compound phase. The aforementioned composite compound phase includes at least one selected from the group consisting of carbides, nitrides, and carbonitrides, which contain Ti and at least one element selected from the group consisting of V, Cr, Zr, Nb, Mo, Hf, Ta, and W. In the cross-sectional structure, the content of the Al compound phase is greater than 0.0 area% and less than or equal to 20.0 area% of the total area of ​​the binder phase, and the content of the Ti compound phase is greater than or equal to 80.0 area% and less than 100.0 area%. In the cross-sectional structure, if the content ratio of the composite compound phase relative to 100% of the total area of ​​the binder phase is denoted as content ratio X1, and the content ratio of the composite compound phase relative to 100% of the total area of ​​the binder phase in the range from the interface between the cubic boron nitride and the binder phase to a distance of 300 nm toward the binder phase is denoted as content ratio X2, then if content ratio X2 is greater than content ratio X1, Cubic boron nitride sintered body. <2> The ratio of the content ratio X2 to the content ratio X1 is 1.10 or more and 2.10 or less. <1> A cubic boron nitride sintered body as described in [reference]. <3> The aforementioned content percentage X1 is 2.0 area% or more and 30.0 area% or less. <1> or <2> A cubic boron nitride sintered body as described in [reference]. <4> The average particle size of the composite compound phase is 0.8 μm or more and 3.0 μm or less. <1> ~ <3> A cubic boron nitride sintered body as described in any one of the following. <5> In the composite compound phase, the content ratio of at least one element selected from the group consisting of V, Cr, Zr, Nb, Mo, Hf, Ta, and W with respect to the total content ratio with Ti is 0.10 or more and 0.60 or less in atomic ratio. The cubic boron nitride sintered body according to any one of <1> to <4>. <6> The content ratio X2 is 3.0 area% or more and 45.0 area% or less. The cubic boron nitride sintered body according to any one of <1> to <5>. <7> Including the cubic boron nitride sintered body according to any one of <1> to <6>, and a coating layer formed on the surface of the cubic boron nitride sintered body. The coating layer is a single layer or a laminate of two or more layers containing at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, and Si, and at least one element selected from the group consisting of C, N, O, and B. The average thickness of the entire coating layer is 0.5 μm or more and 8.0 μm or less. Coated cubic boron nitride sintered body. <8> A tool including the cubic boron nitride sintered body according to any one of <1> to <6>. <9> A tool including the coated cubic boron nitride sintered body according to <7>.

Advantages of the Invention

[0010] According to the present invention, it is possible to provide a cubic boron nitride sintered body and a coated cubic boron nitride sintered body having excellent wear resistance and chipping resistance and capable of extending the tool life, and a tool having them.

Embodiments for Carrying Out the Invention

[0011] The following describes in detail embodiments for carrying out the present invention (hereinafter simply referred to as "this embodiment"), but the present invention is not limited to the embodiments described below. The present invention can be modified in various ways without departing from its spirit.

[0012] [Cubic boron nitride sintered body] The cubic boron nitride sintered body of this embodiment (hereinafter, cubic boron nitride may be referred to as "cBN") is a cBN sintered body comprising cBN and a binder phase, wherein when the cross-sectional structure of the cBN sintered body is observed, the cBN content is 10.0 area% to 60.0 area% of the total 100 area% of the cBN sintered body, and the binder phase content is 40.0 area% to 90.0 area%. The binder phase comprises an Al compound phase and a Ti compound phase, the Al compound phase comprises a compound of Al and at least one element selected from the group consisting of C, N, O, and B, and the Ti compound phase comprises a compound of Ti and at least one element selected from the group consisting of C, N, O, and B, and at least one element selected from the group consisting of V, Cr, Zr, Nb, Mo, Hf, Ta, and W, and at least one element selected from the group consisting of C, N, O, and B. The Ti compound phase includes a composite compound phase, and the composite compound phase includes at least one selected from the group consisting of Ti and at least one element selected from the group consisting of V, Cr, Zr, Nb, Mo, Hf, Ta, and W, and in the cross-sectional structure, the content of the Al compound phase is greater than 0.0 area% and less than or equal to 20.0 area% of the total 100 area% of the bonded phase, and the content of the Ti compound phase is 80.0 area% or more and less than 100.0 area%. In the cross-sectional structure, when the content of the composite compound phase relative to 100 area% of the total bonded phase is defined as content X1, and in the range from the interface between cBN and the bonded phase to a distance of 300 nm toward the bonded phase, the content of the composite compound phase relative to 100 area% of the total bonded phase is defined as content X2, then content X2 is greater than content X1.

[0013] By adopting this configuration, the cBN sintered body of this embodiment can improve wear resistance and fracture resistance, thereby extending tool life. The factors contributing to the improved wear resistance and fracture resistance of the cBN sintered body in this embodiment, resulting in a longer tool life, are not fully understood, but the inventors speculate that these factors are as follows. However, the factors are not limited to these.

[0014] In this embodiment, when the cross-sectional structure of the cBN sintered body is observed, the cBN content is 10.0 area% or more relative to the total area 100% of the cBN sintered body. This results in a high content of cBN, which has excellent mechanical strength, and therefore primarily exhibits superior fracture resistance. On the other hand, in this embodiment, the cBN sintered body has a cBN content of 60.0 area% or less. This results in a low content of cBN, which has poor reactivity with iron, and therefore primarily exhibits superior wear resistance.

[0015] In this embodiment, when the cross-sectional structure of the cBN sintered body is observed, the content of the binder phase is 40.0 area % or more relative to the total area 100% of the cBN sintered body. As a result, the content of cBN, which has poor reactivity with iron, is relatively low, and therefore the cBN sintered body is mainly excellent in wear resistance. On the other hand, in this embodiment, the content of the binder phase is 90.0 area % or less. As a result, the content of cBN, which has excellent mechanical strength, is relatively high, and therefore the cBN sintered body is mainly excellent in fracture resistance.

[0016] In this embodiment, the cBN sintered body has an Al compound phase containing a compound of Al and at least one element selected from the group consisting of C, N, O, and B. When the cross-sectional structure of the cBN sintered body is observed, the Al compound phase content is greater than 0.0 area% relative to 100 area% of the total bonding phase, which improves the sinterability of the cBN sintered body and thus mainly provides excellent fracture resistance. On the other hand, in this embodiment, the Al compound phase content is 20.0 area% or less, which suppresses the formation of coarse Al compounds and improves chipping resistance, thus mainly providing excellent fracture resistance.

[0017] In this embodiment, the cBN sintered body contains a Ti compound phase which includes at least one compound selected from the group consisting of Ti and at least one element selected from the group consisting of C, N, O, and B, and a compound consisting of Ti and at least one element selected from the group consisting of V, Cr, Zr, Nb, Mo, Hf, Ta, and W, and at least one element selected from the group consisting of C, N, O, and B. When the cross-sectional structure of the cBN sintered body is observed, the content of the Ti compound phase is 80.0 area % or more relative to 100 area % of the total area of ​​the binder phase, which improves the reactivity resistance with iron and therefore mainly provides excellent wear resistance. On the other hand, in this embodiment, the cBN sintered body has a Ti compound phase content of less than 100.0 area % which improves toughness and therefore mainly provides excellent fracture resistance.

[0018] The cBN sintered body of this embodiment has improved toughness and is mainly excellent in fracture resistance, as the Ti compound phase includes a composite compound phase, and the composite compound phase includes at least one carbide, nitride, and carbonitride selected from the group consisting of Ti and at least one element selected from the group consisting of V, Cr, Zr, Nb, Mo, Hf, Ta, and W.

[0019] In this embodiment, when observing the cross-sectional structure of the cBN sintered body, if the content ratio of the composite compound phase relative to 100% of the total area of ​​the binder phase is defined as content ratio X1, and the content ratio of the composite compound phase relative to 100% of the total area of ​​the binder phase in the range from the interface between cBN and the binder phase to a distance of 300 nm toward the binder phase is defined as content ratio X2, then because content ratio X2 is greater than content ratio X1, the composite compound phase, which has excellent toughness but poor thermal conductivity among the Ti compound phases, is unevenly distributed near the surface of the cBN particles, which have excellent thermal conductivity. As a result, the toughness of the cBN sintered body is improved without reducing its thermal shock resistance, and thus it mainly exhibits excellent fracture resistance.

[0020] The cBN sintered body of this embodiment contains cBN and a binder phase. The cBN content is 10.0 area% to 60.0 area%, and the binder phase content is 40.0 area% to 90.0 area%. In the cBN sintered body of this embodiment, the total content of cBN and the binder phase is 100.0 area%.

[0021] In the cBN sintered body of this embodiment, the content ratio (area %) of cBN and the binder phase, as well as the Ti compound phase, Al compound phase, and composite compound phase in the binder phase, can be determined by taking a scan electron microscope (SEM) photograph of an arbitrary cross-section, analyzing the SEM image with commercially available image analysis software, and combining this with analysis using an energy-dispersive X-ray spectrometer (EDS). Specifically, this can be determined by the method described in the examples below.

[0022] [Cubic boron nitride (cBN)] In the cBN sintered body of this embodiment, when the cross-sectional structure of the cBN sintered body is observed, if the cBN content is 10.0 area% or more relative to the total area 100% of the cBN sintered body, the cBN content, which has excellent mechanical strength, is high, and therefore the material has excellent fracture resistance. On the other hand, in the cBN sintered body of this embodiment, if the cBN content is 60.0 area% or less, the cBN content, which has poor reactivity with iron, is low, and therefore the material has excellent wear resistance. From a similar viewpoint, the cBN content is preferably 15.0 area% to 55.0 area%, more preferably 20.0 area% to 50.0 area%, and even more preferably 25.0 area% to 40.0 area%.

[0023] [Binded phase] In this embodiment, when the cross-sectional structure of the cBN sintered body is observed, the content of the binder phase is 40.0 area% or more relative to 100 area% of the total area of ​​the cBN sintered body. As a result, the content of cBN, which has poor reactivity with iron, is relatively low, and therefore the cBN sintered body is mainly excellent in wear resistance. On the other hand, in this embodiment, the content of the binder phase is 90.0 area% or less. As a result, the content of cBN, which has excellent mechanical strength, is relatively high, and therefore the cBN sintered body is mainly excellent in fracture resistance. From a similar viewpoint, the content of the binder phase is preferably 45.0 area% to 85.0 area%, more preferably 50.0 area% to 80.0 area%, and even more preferably 60.0 area% to 75.0 area%.

[0024] [Al compound phase] The cBN sintered body of this embodiment contains an Al compound phase as the binding phase. The content of the Al compound phase is between 0.0 area% and 20.0 area% of the total area of ​​the bonding phase. A content of Al compound phase greater than 0.0 area% improves the sinterability of the cBN sintered body, resulting in superior fracture resistance. On the other hand, a content of Al compound phase of 20.0 area% or less suppresses the formation of coarse Al compounds, improving chipping resistance, thus also resulting in superior fracture resistance. From a similar viewpoint, the content of Al compound phase is preferably between 2.1 area% and 17.9 area% of the total area of ​​the bonding phase, more preferably between 3.0 area% and 15.0 area%, and even more preferably between 5.0 area% and 12.1 area%.

[0025] The cBN sintered body of this embodiment has an Al compound phase which contains a compound of Al and at least one element selected from the group consisting of C, N, O, and B. When the Al compound phase contains such a compound, the sinterability of the cBN sintered body is improved, and it tends to have excellent fracture resistance. From a similar viewpoint, the Al compound phase preferably contains at least one selected from the group consisting of Al2O3, AlN, and AlB2, more preferably contains at least one selected from the group consisting of Al2O3 and AlN, and even more preferably contains Al2O3.

[0026] [Ti compound phase] The cBN sintered body of this embodiment contains a Ti compound phase as the binding phase. When the Ti compound phase content is 80.0 area% or more relative to 100 area% of the total bonded phase, the reactivity resistance with iron is improved, resulting in excellent wear resistance. On the other hand, when the Ti compound phase content is less than 100.0 area%, the toughness is improved, resulting in excellent fracture resistance. From a similar viewpoint, the Ti compound phase content is preferably 82.1 area% to 97.9 area%, more preferably 85.0 area% to 97.0 area%, and even more preferably 87.9 area% to 95.0 area%.

[0027] The Ti compound phase includes at least one compound selected from the group consisting of Ti and at least one element selected from the group consisting of C, N, O, and B, and at least one compound selected from the group consisting of Ti and at least one element selected from the group consisting of C, N, O, and B. When the Ti compound phase contains such compounds, its reactivity resistance with iron is improved, and therefore it is mainly excellent in wear resistance. From a similar viewpoint, the Ti compound phase preferably contains at least one selected from the group consisting of TiC, TiCN, TiN, and TiB2, in addition to the composite compound phase described later, more preferably contains at least one selected from the group consisting of TiC, TiCN, and TiB2, even more preferably contains at least one selected from the group consisting of TiC and TiB2, and particularly preferably contains TiC and TiB2.

[0028] [Composite compound phase] In this embodiment, the cBN sintered body contains a composite compound phase in the Ti compound phase. The content ratio X1 of the composite compound phase relative to 100% of the total area of ​​the binder phase is preferably 2.0 area% to 30.0 area%. When the content ratio X1 is 2.0 area% or more, toughness is improved, and thus the material tends to have excellent fracture resistance. On the other hand, when the content ratio X1 of the composite compound phase is 30.0 area% or less, the Ti compound phase contains a relatively large amount of Ti compound phase other than the composite compound phase, which improves the thermal conductivity of the binder phase and improves thermal shock resistance, thus the material tends to have excellent fracture resistance. Furthermore, since the thermal conductivity is improved, wear resistance also tends to improve. From a similar viewpoint, the content ratio X1 of the composite compound phase is more preferably 2.5 area% to 18.9 area%, even more preferably 3.8 area% to 15.0 area%, and particularly preferably 6.3 area% to 10.7 area%.

[0029] In this embodiment, the cBN sintered body preferably has a composite compound phase content X2 relative to 100% of the total area of ​​the binder phase in the range from the interface between cBN and the binder phase to a distance of 300 nm toward the binder phase, which is 3.0 area% or more and 45.0 area% or less. When the content X2 is 3.0 area% or more, the propagation of cracks generated during cutting into the cBN is suppressed, and thus the material tends to have excellent fracture resistance. On the other hand, when the content X2 is 45.0 area% or less, the sinterability is improved, and thus the material tends to have excellent fracture resistance. From a similar viewpoint, the content X2 is more preferably 4.5 area% or more and 41.4 area% or less, even more preferably 6.2 area% or more and 27.4 area% or less, and particularly preferably 9.7 area% or more and 20.5 area% or less. In the definition of content ratio X2, "the entire bonded phase" refers to the entire bonded phase within a distance of 300 nm from the interface between cBN and the bonded phase toward the bonded phase, while "content ratio X2 of the composite compound phase" refers to the content ratio of the composite compound phase within a distance of 300 nm from the interface between cBN and the bonded phase toward the bonded phase. Furthermore, if the bonded phase region is narrow and there is a double overlap between the range from the interface between cBN and the bonded phase toward the bonded phase and the range from another interface between cBN and the bonded phase toward the bonded phase, the area of ​​the overlapping portion is not counted twice. Similarly, if there is a triple or more overlap in the said range, the area of ​​the overlapping portion is not counted three or more times.

[0030] The ratio of the above-mentioned content ratio X2 to the above-mentioned content ratio X1 (X2 / X1) is preferably 1.10 or more and 2.10 or less. When the ratio of the content ratio X2 to the content ratio X1 (X2 / X1) is 1.10 or more, the effect of unevenly distributing the composite compound phase, which has excellent toughness but poor thermal conductivity, near the surface of the cBN particles, which has excellent thermal conductivity, is more effectively and reliably achieved, and the toughness is improved without reducing the thermal shock resistance of the cBN sintered body, resulting in a tendency for excellent fracture resistance. On the other hand, when the ratio of the content ratio X2 to the content ratio X1 (X2 / X1) is 2.10 or less, the frequency of contact between the binder phase other than the composite compound phase and the composite compound phase in the binder phase increases, improving the toughness of the binder phase, resulting in a tendency for excellent fracture resistance. In addition, the thermal conductivity is improved, so the wear resistance also tends to improve. From a similar viewpoint, the ratio of content X2 to content X1 (X2 / X1) is more preferably 1.16 or more and 2.05 or less, even more preferably 1.31 or more and 1.97 or less, and particularly preferably 1.37 or more and 1.81 or less.

[0031] The cBN sintered body of this embodiment comprises a composite compound phase containing Ti and at least one element selected from the group consisting of carbides, nitrides, and carbonitrides, which contain at least one element selected from the group consisting of V, Cr, Zr, Nb, Mo, Hf, Ta, and W (hereinafter also referred to as element M). When the composite compound phase contains such a compound, the toughness is improved, and thus the material exhibits excellent fracture resistance. From a similar viewpoint, the composite compound phase more preferably contains at least one element selected from the group consisting of carbides, nitrides, and carbonitrides containing Ti and element M, even more preferably contains at least one element selected from the group consisting of carbides and nitrides containing Ti and element M, and particularly preferably contains carbides containing Ti and element M. Furthermore, element M is preferably at least one element selected from the group consisting of V, Zr, Nb, Mo, Ta, and W, more preferably at least one element selected from the group consisting of Zr, Nb, Mo, Ta, and W, and even more preferably W.

[0032] In this embodiment, the cBN sintered body preferably has an average particle size of the composite compound phase of 0.8 μm or more and 3.0 μm or less. An average particle size of 0.8 μm or more of the composite compound phase tends to more effectively and reliably achieve the toughness improvement effect due to the inclusion of the composite compound phase. On the other hand, an average particle size of 3.0 μm or less of the composite compound phase tends to more effectively and reliably achieve the effect of making the above-mentioned content ratio X2 greater than the above-mentioned content ratio X1. From a similar viewpoint, the average particle size of the composite compound phase is more preferably 1.0 μm or more and 2.8 μm or less, even more preferably 1.2 μm or more and 2.4 μm or less, and particularly preferably 1.4 μm or more and 2.0 μm or less. The average particle size of the composite compound phase is measured by the method described in the examples.

[0033] In this embodiment, the cBN sintered body preferably has an atomic ratio M / (Ti+M) of 0.10 or more and 0.60 or less in the composite compound phase, where the ratio of the content of element M to the total content of element M and Ti is 0.10 or more. When the atomic ratio M / (Ti+M) in the composite compound phase is 0.10 or more, the effect of improving toughness due to the inclusion of the composite compound phase tends to be more effective and reliable. On the other hand, when the atomic ratio M / (Ti+M) in the composite compound phase is 0.60 or less, the sinterability is improved, and therefore the material tends to have excellent fracture resistance. From a similar viewpoint, it is more preferable that the atomic ratio M / (Ti+M) is 0.11 or more and 0.57 or less, even more preferable that it is 0.17 or more and 0.55 or less, and particularly preferable that it is 0.30 or more and 0.48 or less.

[0034] [Other aspects] The bonding phase of the cBN sintered body of this embodiment may include, in addition to the Al compound phase and the Ti compound phase, at least one element selected from a third group, which consists of a metal of at least one element selected from a first group consisting of Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W, Al, Si, Co, and Ni; an alloy of at least two elements selected from the first group; and a compound of at least one element selected from the first group and at least one element selected from a second group consisting of C, N, O, and B. The bonding phase further containing such components improves sinterability and tends to have excellent fracture resistance. Examples of such components include V, VC, VN, Cr, Cr3C2, CrN, Cr2N, Hf, HfC, HfN, Ta, TaC, TaN, Si, SiC, Si3N4, W, WC, Mo, Mo2C, Nb, NbC, NbN, Zr, ZrC, ZrN, ZrO2, Co, CoAl, and Ni. Among these, from the same viewpoint as described above, it is more preferable to include VC, TaC, WC, Mo2C, NbC, ZrN, CrN, Ni, or Co, and even more preferable to include Ni or Co. Furthermore, when such compounds are included, their content is preferably 0.1 area% to 10.0 area% and more preferably 0.5 area% to 9.0 area% of 100 area% of the total bonded phase.

[0035] In this embodiment, the composition of cBN and each compound in the bonded phase can be identified using a commercially available X-ray diffraction analyzer. For example, by performing X-ray diffraction measurements of a 2θ / θ focused optical system using Cu-Kα rays under predetermined conditions using a Rigaku X-ray diffractometer (product name "SmartLab"), the composition of cBN and the bonded phase can be identified. Suitable measurement conditions include, for example, output: 45kV, 200mA, incident solar slit: 5°, diverging longitudinal slit: 2 / 3°, diverging longitudinal limiting slit: 5mm, scattering slit: 2 / 3°, receiving solar slit: 5°, receiving slit: 0.3mm, sampling width: 0.02°, scan speed: 1° / min, and 2θ measurement range: 30~90°. In addition, when it is difficult to identify by X-ray diffraction measurement, the composition of each compound can also be specified by the method described in the examples below (analysis by SEM image and EDS analysis).

[0036] In the present embodiment, the cBN sintered body may unavoidably contain impurities. Examples of unavoidable impurities include, but are not particularly limited to, lithium, calcium, silicon, and magnesium contained in the raw material powder. Usually, the content ratio of unavoidable impurities is 1% by mass or less based on the entire cBN sintered body. Therefore, unavoidable impurities hardly affect the characteristic values of the cBN sintered body.

[0037] [Method for manufacturing cubic boron nitride sintered body] (Preparation and weighing process of raw material powder) The cBN sintered body of the present embodiment can be manufactured, for example, by the following method. As the raw material powder, cubic boron nitride (cBN) powder, Al powder, TiC powder, TiCN powder, TiN powder, TiC 0.8 powder, TiCN 0.8 powder, TiN 0.8 powder, Ni powder, Co powder, TiWC powder (Ti 0.6 W 0.4 C, Ti 0.8 W 0.2 C), WC powder, TiWTaC powder (Ti 0.6 W 0.3 Ta 0.1 C), VC powder, VN powder, Cr3C2 powder, Cr2N powder, Mo2C powder, NbC powder, NbN powder, HfC powder, HfN, ZrC powder, ZrN powder, WC powder, etc. are prepared. Here, by adjusting the average particle size of the raw material powder containing the M element, the average particle size of the obtained composite compound phase can also be adjusted. In addition, by appropriately adjusting the ratio of each raw material powder, the content ratios (area %) of cBN and the bonding phase in the obtained cBN sintered body can be controlled within the above specific range. Further, by appropriately adjusting the ratio of the raw material powder containing the M element, the atomic ratio M / (Ti + M) in the composite compound phase can be controlled within the above specific range.

[0038] (Modification process, stirring process) Here, the surface of the cBN powder is modified with an anionic polymer, and the raw material powder containing the M element is modified with a cationic polymer (modification step). The surface-modified cBN powder and the raw material powder containing the M element are stirred in ethanol for 1 to 24 hours to cause electrostatic adsorption between the powders, and then centrifugation is performed to remove excess polymer (stirring step).

[0039] Through these modification and stirring processes, the content ratio X2 tends to become larger than the content ratio X1. Furthermore, by going through the modification and stirring processes, and by increasing the processing time of the stirring process, the ratio of content ratio X2 to content ratio X1 (X2 / X1) tends to increase. Moreover, by reducing the average particle size of the raw material powder containing element M, and then going through the modification and stirring processes, the ratio of content ratio X2 to content ratio X1 (X2 / X1) tends to increase. When the ratio (X2 / X1) increases through these methods, the content ratio X2 also tends to increase.

[0040] (Mixing process) Next, each prepared raw material powder is placed in a cylinder for a ball mill together with alumina balls, hexane solvent, and paraffin and mixed. By appropriately adjusting the proportion of each raw material powder, the content percentage (area %) of the Ti compound phase and the Al compound phase in the binding phase, and the content percentage X1 (area %) of the composite compound phase in the Ti compound phase can be controlled to the above-mentioned specific range. The composite compound phase may use carbide, nitride, and carbonitride raw materials containing Ti and M elements as described above, or a carbide, nitride, and carbonitride raw material of M element and TiC 0.8 , TiCN 0.8 , and / or TiN 0.8 It is obtained by using raw materials. Furthermore, when using raw material powder containing an element M in which the atomic ratio of element M to the total of Ti and element M is small, the atomic ratio M / (Ti+M) in the composite compound phase tends to be small. In addition, as a raw material other than the composite compound phase, TiC0.8 Powder, TiCN 0.8 Powder and / or TiN 0.8 When powder is used and its proportion is large, the atomic ratio M / (Ti+M) in the composite compound phase tends to be small.

[0041] (Filling process, drying process, sintering process) The raw material powder, mixed in a ball mill, is filled into a high-melting-point metal capsule made of Zr in a glove box under a nitrogen atmosphere (filling process). To remove moisture and organic components adsorbed on the surface of the filled raw material powder, vacuum heat treatment is performed with the capsule open (drying process). After vacuum heat treatment, the capsule is sealed, and the raw material powder filled in the capsule is sintered at high temperature and pressure (sintering process). The sintering conditions are, for example, pressure: 4.0 GPa to 7.0 GPa, temperature: 1200°C to 1500°C, and sintering time: 20 minutes to 60 minutes.

[0042] Furthermore, for a more specific manufacturing method, the method described in the examples below may be used.

[0043] [Coated cubic boron nitride sintered body] The coated cubic boron nitride sintered body of this embodiment comprises the cBN sintered body described above and a coating layer formed on the surface of the cBN sintered body, wherein the coating layer is a single layer or a stack of two or more layers containing at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, and Si, and at least one element selected from the group consisting of C, N, O, and B, and the average thickness of the entire coating layer is 0.5 μm or more and 8.0 μm or less. The abrasion resistance of the cBN sintered body is further improved by forming a coating layer on its surface. Furthermore, the coated cBN sintered body of this embodiment, in which the coating layer has the above-mentioned components and composition, exhibits excellent abrasion resistance. Moreover, the abrasion resistance is mainly improved when the average thickness of the entire coating layer is 0.5 μm or more, and the fracture resistance is mainly improved when the average thickness is 8.0 μm or less, as it suppresses the occurrence of defects caused by peeling. From this viewpoint, the average thickness of the entire coating layer is preferably 1.0 μm or more and 6.5 μm or less, and more preferably 1.5 μm or more and 6.0 μm or less.

[0044] Examples of compounds that form the coating layer include TiCN, TiC, TiN, TiAlN, TiSiN, CrN, and NbN. The coating layer may have a structure in which multiple layers with different compositions are alternately stacked. In this case, the average thickness of each layer is, for example, 5 nm to 500 nm.

[0045] The thickness of each layer constituting the coating layer, as well as the overall thickness of the coating layer, can be measured from the cross-sectional structure of the coated cBN sintered body using an optical microscope, scanning electron microscope (SEM), or transmission electron microscope (TEM). Furthermore, the average thickness of each layer and the overall thickness of the coating layer in a coated cubic boron nitride sintered body can be determined by measuring the thickness of each layer and the overall thickness of the coating layer from three or more cross-sections located approximately 50 μm from the cutting edge of the surface facing the metal evaporation source toward the center of that surface, and then calculating the average value.

[0046] Furthermore, the composition of each layer constituting the coating layer can be measured from the cross-sectional structure of the coated cBN sintered body using methods such as EDS or wavelength-dispersive X-ray analysis (WDS).

[0047] The method for manufacturing the coating layer in the coated cBN sintered body of this embodiment is not particularly limited, but examples include chemical vapor deposition, ion plating, arc ion plating, sputtering, and ion mixing. Among these, arc ion plating is preferred because it provides superior adhesion between the coating layer and the cBN sintered body.

[0048] [tool] The tool of this embodiment includes the cBN sintered body or the coated cBN sintered body described above. The tool of this embodiment may have the same configuration as known tools, except that it includes the cBN sintered body or coated cBN sintered body. Since the cBN sintered body or coated cBN sintered body of this embodiment has excellent wear resistance and fracture resistance, tools containing them can be used, for example, as cutting tools or wear-resistant tools, and are preferably used as cutting tools. It is even more preferable that the cBN sintered body or coated cBN sintered body of this embodiment be included in cutting tools for carburized and hardened steel. When the cBN sintered body or coated cBN sintered body of this embodiment is included in cutting tools or wear-resistant tools, the tool life can be extended compared to conventional tools. [Examples]

[0049] The present invention will be described more specifically below with reference to examples. The present invention is not limited in any way by the following examples.

[0050] (Example 1) [Preparation and weighing of raw material powders] The raw material powders include cubic boron nitride (cBN) powder, Al powder, TiC powder, TiCN powder, TiN powder, and TiC 0.8 Powder, TiN 0.8 Raw material powders containing elements M were prepared by weighing them according to the ratios shown in Tables 1 and 2 below. The types of raw material powders containing elements M are as shown in Table 1. The average particle sizes were 2.0 μm (cBN powder), 1.8 μm (Al powder), 1.0 μm (TiC powder), 1.0 μm (TiCN powder), 1.0 μm (TiN powder), and 1.0 μm (TiC 0.8 powder), 1.0μm (TiN 0.8The particle sizes were 1.5 μm (Ni powder) and 1.5 μm (Co powder), and the average particle sizes of the raw material powders containing element M are shown in Tables 1 and 2. The average particle size of the raw material powders was measured using the Fisher Sub-Sieve Sizer (FSSS) method described in ASTM standard B330.

[0051] [Table 1]

[0052] [Table 2]

[0053] [Modification process] Of the weighed raw material powders, the surface of the cBN powder was modified using sodium polystyrene sulfonate, an anionic polymer, and the raw material powder containing element M was modified using polydiallyldimethylammonium chloride, a cationic polymer.

[0054] [Agitation process] Next, the surface-modified cBN powder and the raw material powder containing element M were stirred in ethanol to induce electrostatic adsorption between the powders. The stirring time was as shown in Table 3. After stirring, centrifugation was performed to remove excess polymer. For comparative samples 8 and 10, the modification and stirring steps were omitted.

[0055] [Table 3]

[0056] [Mixing process] The raw material powder after the stirring process and the remaining raw material powder after weighing were placed in a cylinder for a ball mill along with alumina balls, hexane solvent, and paraffin, and mixed for 6 hours. For comparative samples 8 and 10, the modification and stirring processes were omitted, and the weighed raw material powder was mixed as described above.

[0057] [Filling process and drying process] The mixed raw material powder was filled into a high melting point metal capsule made of Zr (hereinafter simply referred to as "capsule") under a nitrogen atmosphere in a glove box. In order to remove the moisture and organic components adsorbed on the surface of the filled raw material powder, vacuum heat treatment was performed with the capsule open. After the vacuum heat treatment, the capsule was sealed.

[0058] [Sintering process] Next, the raw material powder filled in the capsule was sintered at high temperature and high pressure for 60 minutes. The sintering conditions are shown below. · Sintering temperature: 1250 °C, · Pressure: 6.0 GPa.

[0059] [Analysis of composition by X-ray diffraction (XRD)] Regarding the cBN and the bonding phase contained in the cBN sintered body obtained by the sintering process, analysis of the composition by X-ray diffraction (XRD) was performed. The compositions of the cBN and the bonding phase were identified using an X-ray diffractometer (product name "SmartLab") manufactured by Rigaku Corporation. Specifically, X-ray diffraction measurement of the 2θ / θ focusing optical system using Cu-Kα rays was performed under the following conditions to identify the compositions of the cBN and the bonding phase. [X-ray diffraction measurement conditions] Output: 45 kV, 200 mA, Incident side solar slit: 5°, Divergent vertical slit: 2 / 3°, Divergent vertical limiting slit: 5 mm, Scattering slit 2 / 3°, Receiving side solar slit: 5°, Receiving slit: 0.3 mm, Sampling width: 0.02°, Scan speed: 1° / min, 2θ measurement range: 30 to 90°. The analysis results are shown in Tables 4-6. In Tables 4-6, only the phases for which clear peaks were obtained by X-ray diffraction measurements are identified. Carbides, nitrides, and carbonitrides containing Ti, which were difficult to identify by X-ray diffraction measurements, as well as carbides, nitrides, and carbonitrides containing both Ti and M elements, were identified by combining them with analysis using EDS, which will be described later.

[0060] [Analysis of SEM images and analysis using EDS] For the cBN sintered body obtained by the above sintering process, the content ratio (area %) of cBN and the binder phase was determined by analyzing cross-sectional microstructure images of the cBN sintered body taken with a scanning electron microscope (SEM) using commercially available image analysis software. More specifically, the cBN sintered body was polished in a direction perpendicular to its surface to obtain a mirror-polished surface. Next, the mirror-polished surface of the cBN sintered body, magnified at 5000x, was observed using a backscattered electron image with an SEM. Using an energy-dispersive X-ray analyzer (EDS) attached to the SEM, the black areas were identified as cBN, and the gray and white areas as the binder phase. Furthermore, within the binder phase, the dark gray areas were identified as the Al compound phase, and the light gray and white areas as the Ti compound phase. Subsequently, microstructure images of the above cross-section of cBN were taken using the SEM. The microstructure images were taken to include a 15 μm × 15 μm field of view, and a total of 20 field of view images were obtained. Using image analysis software, the occupied areas of cBN and the bonded phase were determined from the tissue photographs, and the content percentage (area %) was calculated from these occupied areas. Similarly, the content percentage (area %) of the Ti compound phase and the Al compound phase in the bonded phase were calculated from the tissue photographs, based on the occupied area of ​​each phase relative to the occupied area of ​​the bonded phase. The average of the content percentages obtained from 20 fields of view of the tissue photographs was used as the content percentage for each sample. Furthermore, for inventions 29 and 30, in which the bonded phase contains materials other than the Al compound phase and the Ti compound phase, these were identified by combining them with the EDS mapping analysis described later, and the occupied areas of the Al compound phase and the other phases other than the Ti compound phase were determined and their content percentage (area %) was calculated.

[0061] The content ratio (area %) of the composite compound phase and the Ti compound phase other than the composite compound phase in the bonded phase was calculated by combining image analysis of microstructure images of cBN sintered bodies taken with SEM, as described above, with mapping analysis using EDS. Specifically, mapping analysis was performed on the same field of view as the field of view from which the above microstructure images were obtained. By analyzing this, composite compound phases with an atomic ratio of M (M / (Ti+M)) of 0.10 or more relative to the total of Ti and M elements were identified, and Ti compound phases other than the composite compound phases with an atomic ratio of less than 0.10 were identified. From the area occupied by each phase relative to the area occupied by the bonded phase, the content ratio X1 (area %) of the composite compound phase and the content ratio (area %) of the Ti compound phase other than the composite compound phase were calculated relative to 100% of the total bonded phase area. The average value of the content ratios obtained from the analysis of 20 fields of view was used as the content ratio for each sample.

[0062] Furthermore, using commercially available image analysis software, tissue photographs of the same field of view as described above were analyzed to determine the occupied area of ​​the bonded phase and the occupied area of ​​the composite compound phase in the range from the interface between cBN and the bonded phase to a distance of 300 nm toward the bonded phase. The content ratio X2 (area %) of the composite compound phase relative to 100% of the total bonded phase area in the above range was then calculated. The average of the content ratios obtained from the analysis of 20 fields of view was used as the content ratio for each sample. From the obtained values, the relationship between the above content ratio X1 and the above content ratio X2 was confirmed, and the ratio of the above content ratio X2 to the above content ratio X1 (X2 / X1) was calculated.

[0063] In the composite compound phase, the proportion of element M relative to the total proportion of elements Ti and M (atomic ratio M / (Ti+M)) was calculated as follows. First, point analysis by EDS was performed on an arbitrary point on the composite compound phase in the same field of view from which the above microstructure photograph was obtained. Point analysis was performed at the center of the field of view, with the field of view being such that the composite compound phase was in the center of the field of view and occupied at least 80% of the total area of ​​the field of view. One point analysis was performed per field of view, and the proportion of element M relative to the total proportion of elements Ti and M (atomic ratio M / (Ti+M)) was calculated from the obtained results. The average value of the proportions obtained from point analyses of 20 points in 20 fields of view was taken as the average value of M / (Ti+M) for each sample. Furthermore, the type of element M was identified from the obtained results.

[0064] In the composite compound phase, the atomic ratio of element C relative to the total content of elements C and N was calculated as follows. The results of point analysis performed to determine the atomic ratio of element M relative to the total content of elements Ti and M (atomic ratio M / (Ti+M)) were analyzed, and the atomic ratio of element C relative to the total content of elements C and N was calculated. The average value of the content ratios obtained from point analysis of 20 points in 20 fields was used as the content ratio for each sample. If the content ratio of element C relative to the total content of elements C and N was 0.2 or less, it was classified as a nitride containing elements Ti and M ((Ti,M)N); if the content ratio was greater than 0.2 and less than 0.8, it was classified as a carbonitride containing elements Ti and M ((Ti,M)(C,N)); and if the content ratio was 0.8 or more, it was classified as a carbide containing elements Ti and M ((Ti,M)C).

[0065] In Ti compound phases other than the composite compound phase, the content ratio of element C relative to the total content ratio of elements C and N was calculated as follows. First, the results of mapping analysis of the same field of view from which the above tissue photographs were obtained were analyzed to identify regions where the atomic ratio M / (Ti+M) was less than 0.10 and the content ratio of element B was less than 0.05. An arbitrary point was selected on the identified region and point analysis was performed using EDS. Point analysis was performed at the center of the field of view, with the field of view being such that the identified region was in the center of the field of view and occupied at least 80% of the total area of ​​the field of view. One point analysis was performed per field of view, and the content ratio of element C relative to the total content ratio of elements C and N was calculated from the obtained results. The average value of the content ratios obtained from a total of 20 point analyses across 20 fields of view was used as the content ratio for each sample. Furthermore, if the proportion of element C relative to the total proportion of elements N and C was 0.2 or less, it was classified as TiN; if the proportion was greater than 0.2 but less than 0.8, it was classified as TiCN; and if the proportion was 0.8 or more, it was classified as TiC. The region where the proportion (atomic ratio) of element B was less than 0.05 was targeted in order to exclude TiB2, which was identified by X-ray diffraction measurements, from the analysis points.

[0066] In the analysis of SEM images and EDS, the mirror-polished surface of the cBN sintered body is the surface of the cBN sintered body or a cross-section of the cBN sintered body obtained by mirror polishing an arbitrary cross-section. The mirror-polished surface of the cBN sintered body was obtained by polishing with diamond paste. The results obtained above are shown in Tables 4-6.

[0067] Furthermore, by analyzing the images of the tissue photographs described above, the area of ​​the composite compound particles within the cross-sectional tissue was determined, and the diameter of a circle with an area equal to that area was defined as the particle size of the composite compound phase. The area-based average value of the particle size of the composite compound phase present in the tissue photographs was calculated. The average value obtained from the analysis of 20 fields of view was determined as the average particle size of the composite compound phase for each sample. These measurement results are shown in Table 6.

[0068] [Table 4]

[0069] [Table 5]

[0070] [Table 6]

[0071] [Manufacturing of cutting tools] The cBN sintered body obtained above was cut using a wire electrical discharge machine to match the insert shape of the tool as defined in ISO standard CNGA120408. The cut cBN sintered body was brazed to a base metal made of cemented carbide. The brazed tool was then honed to obtain a cutting tool.

[0072] The obtained cutting tools were used as samples, and the following cutting tests were performed and evaluated. [Cutting Test] Workpiece material: SCM435H (HRC58) Workpiece shape: A round bar with two equally spaced grooves on its outer surface. Machining method: External turning, Cutting speed: 200m / min, Feed rate: 0.10mm / rev, Cutting depth: 0.20 mm, Coolant: Used (water-soluble coolant), Evaluation criteria: Tool life was defined as the point at which the flank wear width of the tool reached 0.15 mm or when chipping occurred. The machining time until tool life was reached was measured. Furthermore, the damage pattern of samples that reached tool life when the flank wear width reached 0.15 mm was defined as "normal wear," and the damage pattern of samples that reached tool life when chipping occurred was defined as "chipping." The results of the above test are shown in Table 7.

[0073] [Table 7]

[0074] As shown in Table 7, the cutting tool using the invented cBN sintered body exhibits superior wear resistance and fracture resistance compared to the comparative cutting tool using the cBN sintered body, resulting in a longer tool life.

[0075] (Example 2) Next, as shown in Table 8, the surfaces of the cBN sintered bodies of Invention 3, Invention 4, Invention 15, and Invention 17 obtained in Example 1 were subjected to ion bombardment treatment, and then a coating layer was formed by arc ion plating. When forming the first and second layers, they were formed in this order on the surface of the cBN sintered body. For Inventions 32, 38, 42, 46, and 50, which contain two types of compounds in the composition of the first layer, layers of each compound with a thickness of 50 nm per layer were alternately and repeatedly formed to achieve the average thickness of the first layer. The respective treatment conditions were as follows. The composition and average thickness of the coating layer are as shown in Table 8 below.

[0076] [Conditions for ion bombardment treatment] • Substrate temperature: 500℃, • Pressure: Ar gas atmosphere at 2.7 Pa Voltage: -400V, ·Current: 40A, • Duration: 30 minutes.

[0077] [Coating layer formation conditions] • Substrate temperature: 500℃, • Pressure: Nitrogen (N2) gas atmosphere at 3.0 Pa (nitride layer), or a mixed gas atmosphere of nitrogen (N2) gas and acetylene (C2H2) gas at 3.0 Pa (carbonitride layer) Voltage: -60V, ·Current: 120A.

[0078] [Table 8]

[0079] The obtained coated cBN sintered body was subjected to a cutting test in the same manner as in Example 1, and the invention was evaluated. The results are shown in Table 9.

[0080] [Table 9]

[0081] As shown in Table 9, coated cBN sintered bodies with a coating layer formed on the surface (inventions 31-50) exhibited even greater wear resistance and fracture resistance than cBN sintered bodies without a coating layer (inventions 3, 4, 15, and 17), resulting in a longer tool life. [Industrial applicability]

[0082] The cubic boron nitride sintered body and the coated cubic boron nitride sintered body of the present invention have excellent wear resistance and fracture resistance, which extends tool life compared to conventional tools, and therefore have high potential for industrial application.

Claims

1. A cubic boron nitride sintered body comprising cubic boron nitride and a bonding phase, When the cross-sectional structure of the cubic boron nitride sintered body was observed, the content of cubic boron nitride was 10.0 area% to 60.0 area% of the total 100 area% of the cubic boron nitride sintered body, and the content of the binding phase was 40.0 area% to 90.0 area%. The bonded phase comprises an Al compound phase and a Ti compound phase. The Al compound phase comprises a compound of Al and at least one element selected from the group consisting of C, N, O, and B. The Ti compound phase includes at least one compound selected from the group consisting of Ti and at least one element selected from the group consisting of C, N, O, and B, and Ti and at least one element selected from the group consisting of V, Cr, Zr, Nb, Mo, Hf, Ta, and W, and at least one element selected from the group consisting of C, N, O, and B. The Ti compound phase includes a composite compound phase, The composite compound phase includes at least one selected from the group consisting of carbides, nitrides, and carbonitrides, which contain Ti and at least one element selected from the group consisting of V, Cr, Zr, Nb, Mo, Hf, Ta, and W. In the cross-sectional structure, the content of the Al compound phase is greater than 0.0 area% and less than or equal to 20.0 area% of the total area of ​​the binder phase, and the content of the Ti compound phase is greater than or equal to 80.0 area% and less than 100.0 area%. In the cross-sectional structure, when the content ratio of the composite compound phase relative to 100% of the total area of ​​the binder phase is defined as content ratio X1, and the content ratio of the composite compound phase relative to 100% of the total area of ​​the binder phase in the range from the interface between the cubic boron nitride and the binder phase to a distance of 300 nm toward the binder phase is defined as content ratio X2, then if content ratio X2 is greater than content ratio X1, Cubic boron nitride sintered body.

2. The ratio of the content ratio X2 to the content ratio X1 is 1.10 or more and 2.10 or less. The cubic boron nitride sintered body according to claim 1.

3. The aforementioned content ratio X1 is 2.0 area% or more and 30.0 area% or less. The cubic boron nitride sintered body according to claim 1.

4. The average particle size of the composite compound phase is 0.8 μm or more and 3.0 μm or less. The cubic boron nitride sintered body according to claim 1.

5. In the composite compound phase, the content ratio of at least one element selected from the group consisting of V, Cr, Zr, Nb, Mo, Hf, Ta, and W to the total content ratio of Ti and at least one element selected from the group consisting of V, Cr, Zr, Nb, Mo, Hf, Ta, and W is 0.10 or more and 0.60 or less in atomic ratio. The cubic boron nitride sintered body according to claim 1.

6. The aforementioned content ratio X2 is 3.0 area% or more and 45.0 area% or less. The cubic boron nitride sintered body according to claim 1.

7. A cubic boron nitride sintered body according to any one of claims 1 to 6, and a coating layer formed on the surface of the cubic boron nitride sintered body, The coating layer is a single layer or a laminate of two or more layers, comprising at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, and Si, and at least one element selected from the group consisting of C, N, O, and B. The average thickness of the entire coating layer is 0.5 μm or more and 8.0 μm or less. Coated cubic boron nitride sintered body.

8. A tool comprising a cubic boron nitride sintered body according to any one of claims 1 to 6.

9. A tool comprising a coated cubic boron nitride sintered body as described in claim 7.

Images