Cubic boron nitride sintered body and coated cubic boron nitride sintered body

Abstract

To provide a cubic boron nitride sintered body and a coated cubic boron nitride sintered body that can extend a tool life by having excellent wear resistance and chipping resistance.SOLUTION: In a cubic boron nitride sintered body including cubic boron nitride and a bonding phase, a content ratio of the cubic boron nitride and the bonding phase is within a specific range, the bonding phase comprises a Ti compound phase, an Al compound phase, and a phase containing an element W, a content ratio of the Ti compound phase, the Al compound phase, and the phase containing the element W is within a specific range, the phase containing the element W includes at least one kind selected from the group consisting of W2B and WB, and a ratio I2 / I1 is in a specific range, where I1 is the X-ray diffraction peak intensity of a (111) plane of cubic boron nitride and I2 is the sum of the X-ray diffraction peak intensities of a (211) plane of the W2B and a (110) plane of the WB in the bonding phase.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a cubic boron nitride sintered body and a coated cubic boron nitride sintered body.

Background Art

[0002] The cubic boron nitride sintered body contains cubic boron nitride (hereinafter also referred to as "cBN") and a binder phase. As a tool using a cBN sintered body for cutting iron-based workpieces such as steel and cast iron, a cBN sintered body containing a Ti compound as a binder phase material has been widely used conventionally. This is because the cBN sintered body containing a Ti compound has a low affinity with iron-based workpieces and excellent resistance to reactive wear.

[0003] Therefore, in recent years, various cBN sintered bodies containing Ti compounds have been proposed. For example, Patent Document 1 discloses a cBN-based ultrahigh-pressure sintered body containing cBN particles and a binder phase, wherein the binder phase contains at least one of an Al nitride or oxide, or a Ti nitride, carbide, or carbonitride, and 0.1 to 5.0% by volume of a metal boride having an average particle size of 20 to 300 nm is dispersed. The metal boride contains a metal boride (B) in which the metal component contains at least one of Nb, Ta, Cr, Mo, and W and does not contain Ti, and a metal boride (A) in which the metal component contains only Ti. When the ratio (volume%) of the metal boride (A) containing only Ti as the metal component among the metal borides is Va, and the ratio (volume%) of the metal boride (B) containing at least one of Nb, Ta, Cr, Mo, and W as the metal component and not containing Ti is Vb, a cBN-based ultrahigh-pressure sintered body in which the ratio Vb / Va is 0.1 to 1.0 has been proposed.

[0004] Further, for example, Patent Document 2 discloses a cubic boron nitride-based ultrahigh pressure sintered body cutting tool having a cubic boron nitride-based ultrahigh pressure sintered body containing cubic boron nitride particles, a binder phase, a Ti boride phase, and a W boride phase as a tool substrate. In this tool, the average particle size of the cubic boron nitride particles is 0.5 to 3.5 μm, and the content thereof is 40 to 75% by volume. In the binder phase, a fine Ti boride phase with an average particle size of 50 to 500 nm and a fine W boride phase with an average particle size of 50 to 500 nm are dispersedly distributed. The sum of the production amounts of the fine Ti boride phase and the W boride phase is 5 to 15% by volume in the binder phase. 15 to 35% by volume of the binder phase is at least one of Al nitride and oxide, and the rest is at least one of Ti nitride, carbide, boride, or carbonitride and inevitable impurities. And, 0.5 ≤ (production amount of W boride phase) / (production amount of Ti boride phase) ≤ 1.0 A cubic boron nitride-based ultrahigh pressure sintered body cutting tool characterized by using a cubic boron nitride-based ultrahigh pressure sintered body satisfying the above relationship as a tool substrate has been proposed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, a cubic boron nitride sintered body containing a Ti compound has low thermal conductivity and toughness, and there is room for improvement. In recent years, higher efficiency has been required for cutting processes, and higher speeds, higher feed rates, and deeper cuts have become more prominent. For this reason, in recent cutting processes, it has been required to improve the chipping resistance and wear resistance of tools more than before.

[0007] Against such a background, the cBN-based ultrahigh pressure sintered body described in Patent Document 1 has insufficient thermal conductivity of the cBN sintered body and room for improvement in wear resistance. Further, in the cubic boron nitride-based ultrahigh pressure sintered body cutting tool described in Patent Document 2, in the binder phase, the proportion of Al 2 O 3 and / or AlN, which is inferior in mechanical strength, is large, so there is room for improvement in wear resistance and / or chipping resistance.

[0008] An object of the present invention is to provide a cubic boron nitride sintered body and a coated cubic boron nitride sintered body that can extend the tool life by having excellent wear resistance and chipping resistance.

Means for Solving the Problems

[0009] As a result of repeated research on extending the tool life, the present inventors have found that when the cubic boron nitride sintered body has a specific structure, its wear resistance and chipping resistance can be improved, and as a result, the tool life can be extended, and the present invention has been completed.

[0010] The gist of the present invention is as follows. [1] A cubic boron nitride sintered body containing cubic boron nitride and a binder phase, With respect to 100.0% by volume of the entire cubic boron nitride sintered body, the content ratio of the cubic boron nitride is 10.0% by volume or more and 60.0% by volume or less, and the content ratio of the binder phase is 40.0% by volume or more and 90.0% by volume or less. The binder phase includes a Ti compound phase, an Al compound phase, and a phase containing a W element. With respect to 100.0% by volume of the entire binder phase, the content ratio of the Ti compound phase is 60.0% by volume or more and 92.0% by volume or less, the content ratio of the Al compound phase is more than 0.0% by volume and less than 15.0% by volume, and the content ratio of the phase containing a W element is 5.0% by volume or more and 30.0% by volume or less. The phase containing a W element contains at least one selected from the group consisting of W 2 B and WB. The X-ray diffraction peak intensity of the (111) plane of the cubic boron nitride is I 1 Let the total X-ray diffraction peak intensity of the (211) plane of W 2 B and the (110) plane of WB in the bonding phase be I 2 When it is, I 2 / I 1 is 0.03 or more and 0.60 or less, a cubic boron nitride sintered body. [2] WB in the bonding phase 2 The X-ray diffraction peak intensity of the (101) plane is I 3 When it is, I 3 / I 1 is 0.03 or less, the cubic boron nitride sintered body according to [1]. [3] W in the bonding phase 2 The X-ray diffraction peak intensity of the (211) plane of B is I 4 When it is, I 4 / I 2 is 0.50 or more and 0.95 or less, the cubic boron nitride sintered body according to [1] or [2]. [4] The average thickness λ of the phase containing the W element is 0.03 μm or more and 0.12 μm or less, the cubic boron nitride sintered body according to any one of [1] to [3]. [5] The Ti compound phase contains TiB 2 and The X-ray diffraction peak intensity of the (101) plane of TiB in the bonding phase 2 is I 5 When it is, I 5 / I 1 is 0.07 or more and 0.55 or less, the cubic boron nitride sintered body according to any one of [1] to [4]. [6] The phase containing the W element contains the Co element, In the phase containing the W element, the content ratio of the Co element to the total content ratio of the W element and the Co element is 5 atomic% or more and less than 50 atomic%, the cubic boron nitride sintered body according to any one of [1] to [5]. [7] A 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, A coated cubic boron nitride sintered body, wherein an average thickness of the entire coating layer is 0.5 μm or more and 6.0 μm or less.

Advantages of the Invention

[0011] According to the present invention, it is possible to provide a cubic boron nitride sintered body and a coated cubic boron nitride sintered body that can extend the tool life by having excellent wear resistance and chipping resistance.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments for carrying out the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail, but the present invention is not limited to the following present embodiment. The present invention can be variously modified without departing from the gist thereof.

[0013] The cBN sintered body of the present embodiment is a cBN sintered body containing cBN and a binder phase. With respect to 100.0% by volume of the entire cBN sintered body, the content ratio of cBN is 10.0% by volume or more and 60.0% by volume or less, and the content ratio of the binder phase is 40.0% by volume or more and 90.0% by volume or less. The binder phase includes a Ti compound phase, an Al compound phase, and a phase containing a W element. With respect to 100.0% by volume of the entire binder phase, the content ratio of the Ti compound phase is 60.0% by volume or more and 92.0% by volume or less, the content ratio of the Al compound phase is more than 0.0% by volume and less than 15.0% by volume, and the content ratio of the phase containing a W element is 5.0% by volume or more and 30.0% by volume or less. The phase containing a W element contains at least one selected from the group consisting of WB and WB, and the X-ray diffraction peak intensity of the (111) plane of cBN is I 2 When the total of the X-ray diffraction peak intensities of the (211) plane of WB and the (110) plane of WB in the binder phase is I 1 And W in the binder phase 2 I when the sum of the X-ray diffraction peak intensities of the (211) plane of B and the (110) plane of WB is I 2 And I 2 / I 1 Is 0.03 or more and 0.60 or less.

[0014] By adopting such a configuration, the cBN sintered body of the present embodiment can improve wear resistance and chipping resistance, and as a result, the tool life can be extended. Although the detailed reasons why the cBN sintered body of the present embodiment has improved wear resistance and chipping resistance and a long tool life are not clear, the inventors consider the reasons as follows. However, the reasons are not limited to this. That is, in the cBN sintered body of the present embodiment, with respect to 100.0% by volume of the entire cBN sintered body, since the content ratio of cBN is 10.0% by volume or more, the content ratio of cBN with excellent mechanical strength becomes high, so it is mainly excellent in chipping resistance. On the other hand, in the cBN sintered body of the present embodiment, since the content ratio of cBN is 60.0% by volume or less, the content ratio of cBN with poor reactivity with iron is low, so it is mainly excellent in wear resistance. In addition, in the cBN sintered body of the present embodiment, since the content ratio of the binder phase is 40.0% by volume or more, the content ratio of cBN with poor reactivity with iron becomes relatively low, so it is mainly excellent in wear resistance. On the other hand, in the cBN sintered body of the present embodiment, since the content ratio of the binder phase is 90.0% by volume or less, the content ratio of cBN with excellent mechanical strength becomes relatively high, so it is mainly excellent in chipping resistance. In addition, in the cBN sintered body of the present embodiment, with respect to 100.0% by volume of the entire binder phase, since the content ratio of the Ti compound phase is 60.0% by volume or more, the reactivity with iron is improved, so it is mainly excellent in wear resistance. On the other hand, in the cBN sintered body of the present embodiment, since the content ratio of the Ti compound phase is 92.0% by volume or less, the thermal conductivity is improved, so it is mainly excellent in wear resistance. In addition, in the cBN sintered body of the present embodiment, with respect to 100.0% by volume of the entire binder phase, since the content ratio of the Al compound phase is more than 0.0% by volume, the sinterability is improved, so it is mainly excellent in chipping resistance. On the other hand, in the cBN sintered body of the present embodiment, since the content ratio of the Al compound phase is less than 15.0% by volume, the Al compound (for example, Al 2 O 3Since the content ratio of 2 and / or the content ratio of an Al compound (e.g., AlN) inferior in mechanical strength is decreased, it is excellent in wear resistance and / or defect resistance. Further, since the content ratio of the Al compound phase is less than 15.0% by volume, it is possible to suppress the formation of an aggregated structure in which the phase containing W is aggregated. Furthermore, since the phase containing W is uniformly distributed in the bonding phase, the thermal conductivity of the cBN sintered body is improved, so that it is mainly excellent in wear resistance. Further, in the cBN sintered body of the present embodiment, since the content ratio of the phase containing W element is 5.0% by volume or more with respect to 100.0% by volume of the entire bonding phase, the thermal conductivity is improved, so that it is mainly excellent in wear resistance. On the other hand, in the cBN sintered body of the present embodiment, since the content ratio of the phase containing W element is 30.0% by volume or less, the hardness is improved, so that it is mainly excellent in wear resistance. Further, in the cBN sintered body of the present embodiment, the phase containing W element contains at least one selected from the group consisting of W 2 B and WB, and the X-ray diffraction peak intensity of the (111) plane of cBN is I 1 . Taking the total X-ray diffraction peak intensity of the (211) plane of W 2 B and the (110) plane of WB as I 2 , when I 2 / I 1 is 0.03 or more, the thermal conductivity is improved, so that it is mainly excellent in wear resistance. On the other hand, in the cBN sintered body of the present embodiment, since I 2 / I 1 is 0.60 or less, the toughness is improved, so that the defect resistance is mainly improved. By combining these effects, the cBN sintered body of the present embodiment has a long tool life with improved wear resistance and defect resistance.

[0015] The cBN sintered body of the present embodiment contains cBN and a bonding phase. The content ratio of cBN is 10.0% by volume or more and 60.0% by volume or less, and the content ratio of the bonding phase is 40.0% by volume or more and 90.0% by volume or less. In the cBN sintered body of the present embodiment, the total content ratio of cBN and the bonding phase is 100.0% by volume.

[0016] In the cBN sintered body of the present embodiment, since the content ratio of cBN is 10.0% by volume or more, the content ratio of cBN with excellent mechanical strength is high, so the defect resistance is excellent. On the other hand, in the cBN sintered body of the present embodiment, since the content ratio of cBN is 60.0% by volume or less, the content ratio of cBN with poor reactivity with iron is low, so the wear resistance is excellent. From the same viewpoint, the content ratio of cBN is preferably 12.2% by volume or more and 57.2% by volume or less, and more preferably 25.1% by volume or more and 45.2% by volume or less.

[0017] Further, in the cBN sintered body of the present embodiment, since the content ratio of the bonding phase is 40.0% by volume or more, the content ratio of cBN with poor reactivity with iron is relatively low, so the wear resistance is excellent. On the other hand, in the cBN sintered body of the present embodiment, since the content ratio of the bonding phase is 90.0% by volume or less, the content ratio of cBN with excellent mechanical strength is relatively high, so the defect resistance is excellent. From the same viewpoint, the content ratio of the bonding phase is preferably 42.8% by volume or more and 87.8% by volume or less, and more preferably 54.8% by volume or more and 74.9% by volume or less.

[0018] In the cBN sintered body of the present embodiment, the content ratios (by volume%) of cBN and the bonding phase can be obtained by photographing an arbitrary cross-section with a scanning electron microscope (SEM) and analyzing the photographed SEM photograph with commercially available image analysis software. Specifically, it can be obtained by the method described in the examples below.

[0019] In the cBN sintered body of the present embodiment, the bonding phase includes a Ti compound phase, an Al compound phase, and a phase containing a W element. In this embodiment, the content ratio of the Ti compound phase is 60.0% to 92.0% by volume based on 100.0% by volume of the entire bonding phase. The cBN sintered body of this embodiment has excellent wear resistance because the content ratio of the Ti compound phase is 60.0% by volume or more, which improves the reactivity resistance with iron. On the other hand, the cBN sintered body of this embodiment has excellent wear resistance because the content ratio of the Ti compound phase is 92.0% by volume or less, which improves the thermal conductivity. From the same viewpoint, the content ratio of the Ti compound phase is preferably 65.5% to 91.2% by volume, and more preferably 73.4% to 88.8% by volume.

[0020] In the cBN sintered body of this embodiment, the Ti compound phase preferably contains at least one selected from the group consisting of TiC, TiCN, TiN, and TiB. 2 When the Ti compound phase contains such compounds, it tends to have excellent reaction wear resistance. From the same viewpoint, the Ti compound phase more preferably contains at least one selected from the group consisting of TiC, TiCN, and TiB. 2 and even more preferably contains at least one selected from the group consisting of TiC and TiB. 2

[0021] In the cBN sintered body of this embodiment, the content ratio of the Al compound phase is more than 0.0% to less than 15.0% by volume based on 100.0% by volume of the entire bonding phase. The cBN sintered body of this embodiment has excellent defect resistance because the content ratio of the Al compound phase is more than 0.0% by volume, which improves the sinterability. On the other hand, the cBN sintered body of this embodiment has inferior thermal conductivity due to the Al compound (e.g., Al 2 O 3Since the content ratio of [[ID=]] and / or the content ratio of an Al compound (e.g., AlN) inferior in mechanical strength is decreased, it is excellent in wear resistance and / or defect resistance. Further, since the content ratio of the Al compound phase is less than 15.0% by volume, it is possible to suppress the formation of an aggregated structure in which the phase containing W is aggregated. Furthermore, since the phase containing W is uniformly distributed in the bonding phase, the thermal conductivity of the cBN sintered body is improved, so that it is excellent in wear resistance. From the same viewpoint, the content ratio of the Al compound phase is preferably 2.0% by volume or more and 14.2% by volume or less, and more preferably 2.9% by volume or more and 11.5% by volume or less.

[0022] In the cBN sintered body of the present embodiment, the Al compound phase is Al 2 O 3 , AlN, AlB 2 and preferably contains at least one selected from the group consisting of. When the Al compound phase contains such a compound, the sinterability of the cBN sintered body is improved, so that it tends to be excellent in defect resistance. From the same viewpoint, the Al compound phase more preferably contains at least one selected from the group consisting of Al 2 O 3 and AlN, and even more preferably contains Al 2 O 3 .

[0023] In the cBN sintered body of the present embodiment, the content ratio of the phase containing the W element is 5.0% by volume or more and 30.0% by volume or less with respect to 100.0% by volume of the entire bonding phase. In the cBN sintered body of the present embodiment, since the content ratio of the phase containing the W element is 5.0% by volume or more, the thermal conductivity is improved, so that it is excellent in wear resistance. On the other hand, in the cBN sintered body of the present embodiment, since the content ratio of the phase containing the W element is 30.0% by volume or less, the hardness is improved, so that it is excellent in wear resistance. From the same viewpoint, the content ratio of the phase containing the W element is preferably 5.9% by volume or more and 28.4% by volume or less, and more preferably 8.1% by volume or more and 20.5% by volume or less. In addition, in the present embodiment, the content ratios (volume %) of the Ti compound phase, the Al compound phase, and the phase containing the W element in the binder phase can be measured by the method described in the examples below.

[0024] In the cBN sintered body of the present embodiment, the phase containing the W element is the above-described W 2 In addition to B and WB, it may contain at least one selected from the group consisting of metals, carbides, nitrides, borides of W, and solid solutions thereof, and alloys, carbides, nitrides, borides, and solid solutions thereof containing at least one selected from the group consisting of W and at least one selected from the group consisting of Co, Al, Ti, Ni, V, Cr, Zr, Nb, Mo, Hf, and Ta. When the phase containing the W element contains such materials, the bonding strength between particles in the cBN sintered body is improved, and the tendency is excellent in chip resistance.

[0025] In the cBN sintered body of the present embodiment, the phase containing the W element preferably contains the Co element. When the phase containing the W element contains the Co element, the bonding strength between particles in the cBN sintered body is improved, and the toughness is further improved, so that the tendency is excellent in chip resistance. In addition, in the present embodiment, when there are a plurality of phases containing the W element, "the phase containing the W element contains the Co element" includes not only the case where all of the phases containing the W element contain the Co element, but also the case where only some of the phases containing the W element contain the Co element. The compound containing the W element and the Co element is not particularly limited, and examples thereof include CoW 2 B 2 and the like. In the phase containing the W element, when the Co element is included, the content ratio of the Co element to the total content ratio of the W element and the Co element is preferably 5 atomic% or more and less than 50 atomic%. In the cBN sintered body of the present embodiment, in the phase containing the W element, since the content ratio of the Co element to the total content ratio of the W element and the Co element is 5 atomic% or more, the toughness is improved, and thus the cBN sintered body tends to be more excellent in defect resistance. On the other hand, in the cBN sintered body of the present embodiment, in the phase containing the W element, since the content ratio of the Co element to the total content ratio of the W element and the Co element is less than 50 atomic%, the hardness is improved, and thus the cBN sintered body tends to be more excellent in wear resistance. From the same viewpoint, the content ratio of the Co element to the total content ratio of the W element and the Co element is more preferably 6 atomic% or more and 43 atomic% or less, and even more preferably 9 atomic% or more and 33 atomic% or less. In addition, in the present embodiment, the content ratio (atomic%) of the Co element in the phase containing the W element can be measured by the method described in the examples below.

[0026] In the cBN sintered body of the present embodiment, the average thickness λ of the phase containing the W element is preferably 0.03 μm or more and 0.12 μm or less. In the cBN sintered body of the present embodiment, since the average thickness λ of the phase containing the W element is 0.03 μm or more, the toughness of the bonding phase is improved, and thus the cBN sintered body tends to be more excellent in defect resistance. On the other hand, in the cBN sintered body of the present embodiment, since the average thickness λ of the phase containing the W element is 0.12 μm or less, it indicates that there are few aggregated structures of the phase containing the W element and it is uniformly distributed in the bonding phase, and since the thermal conductivity is improved, the cBN sintered body tends to be more excellent in wear resistance. From the same viewpoint, the average thickness λ of the phase containing the W element is more preferably 0.04 μm or more and 0.11 μm or less, and even more preferably 0.05 μm or more and 0.10 μm or less. In addition, in the present embodiment, the average thickness λ of the phase containing the W element can be measured by the method described in the examples below.

[0027] In the cBN sintered body of the present embodiment, the phase containing the W element is W 2It contains at least one selected from the group consisting of B and WB, and the X-ray diffraction peak intensity of the (111) plane of cBN is I 1 Let it be, and W in the binder phase 2 The sum of the X-ray diffraction peak intensities of the (211) plane of B and the (110) plane of WB is I 2 Let it be, then I 2 / I 1 is 0.03 or more and 0.60 or less. In the cBN sintered body of this embodiment, since I 2 / I 1 is 0.03 or more, the thermal conductivity is improved, so it has excellent wear resistance. On the other hand, in the cBN sintered body of this embodiment, since I 2 / I 1 is 0.60 or less, the toughness is improved, so the defect resistance is improved. From the same viewpoint, I 2 / I 1 is preferably 0.04 or more and 0.56 or less, more preferably 0.06 or more and 0.54 or less, and even more preferably 0.08 or more and 0.52 or less.

[0028] In the cBN sintered body of this embodiment, the X-ray diffraction peak intensity of the (111) plane of cBN is I 1 Let it be, and WB in the binder phase 2 The X-ray diffraction peak intensity of the (101) plane of is I 3 Let it be, then I 3 / I 1 is preferably 0.03 or less. In the cBN sintered body of this embodiment, since I 3 / I 1 is 0.03 or less, it indicates that the formation of hexagonal W boride with low mechanical strength is suppressed, and the toughness is improved, so it tends to be more excellent in defect resistance. From the same viewpoint, I 3 / I 1 is more preferably 0.02 or less, even more preferably 0.01 or less, and even more preferably 0.00. Also, in the cBN sintered body of this embodiment, it is preferable that the phase containing W does not substantially contain WB 2 . In addition, in this embodiment, WB 2"Substantially free of" means that WB is not detected by X-ray diffraction measurement in the binder phase. 2 This means that it is not detected.

[0029] In the cBN sintered body of the present embodiment, the total of the X-ray diffraction peak intensities of the (211) plane of WB and the (110) plane of WB in the binder phase is defined as I 2 When the X-ray diffraction peak intensity of the (211) plane of WB in the binder phase is defined as I 2 in the binder phase, 2 and the X-ray diffraction peak intensity of the (211) plane of WB is defined as I 4 when I 4 / I 2 is preferably 0.50 or more and 0.95 or less. In the cBN sintered body of the present embodiment, since I 4 / I 2 is 0.50 or more, the thermal conductivity is improved, and thus the wear resistance tends to be further excellent. On the other hand, in the cBN sintered body of the present embodiment, since I 4 / I 2 is 0.95 or less, the hardness is improved, and thus the wear resistance tends to be further excellent. From the same viewpoint, I 4 / I 2 is more preferably 0.51 or more and 0.94 or less, and even more preferably 0.57 or more and 0.92 or less.

[0030] In the cBN sintered body of the present embodiment, the Ti compound phase contains TiB 2 When the X-ray diffraction peak intensity of the (111) plane of cBN is defined as I 1 and the X-ray diffraction peak intensity of the (101) plane of TiB 2 in the binder phase is defined as I 5 when I 5 / I 1 is preferably 0.07 or more and 0.55 or less. In the cBN sintered body of the present embodiment, since the Ti compound phase contains TiB 2 and I 5 / I 1 is 0.07 or more, the bonding strength between cBN and the binder phase is improved, and thus the chipping resistance tends to be further excellent. On the other hand, in the cBN sintered body of the present embodiment, since I 5 / I 1 is 0.55 or less, TiB with low mechanical strength2 Since the ratio is small, the toughness is improved and it tends to be more excellent in defect resistance. From the same viewpoint, I 5 / I 1 is preferably 0.08 or more and 0.53 or less, and more preferably 0.09 or more and 0.42 or less.

[0031] In the present embodiment, the composition of the bonding phase can be identified using a commercially available X-ray diffractometer. For example, when X-ray diffraction measurement of a 2θ / θ focusing optical system using Cu-Kα rays is performed under the following conditions using an X-ray diffractometer (product name "SmartLab") manufactured by Rigaku Corporation, the composition of the bonding phase can be identified. Here, the measurement conditions are Output: 45 kV, 200 mA, Incident-side Soller slit: 5°, Divergence vertical slit: 2 / 3°, Divergence vertical limiting slit: 5 mm, Scattering slit 2 / 3°, Receiving-side Soller slit: 5°, Receiving slit: 0.3 mm, Sampling width: 0.02°, Scan speed: 1° / min, The 2θ measurement range is preferably 30 to 90°. In the present embodiment, the composition of the bonding phase can be measured by the method described in the examples below.

[0032] In the present embodiment, the X-ray diffraction peak intensities of each compound in cBN and the bonding phase can be measured using a commercially available X-ray diffractometer. For example, the X-ray diffraction peak intensity can be measured using an X-ray diffractometer (product name "SmartLab") manufactured by Rigaku Corporation. An example of the measurement conditions is the same as the measurement conditions in the method for identifying the composition of the bonding phase described above.

[0033] The cBN sintered body of this embodiment may unavoidably contain impurities. Examples of the impurities include, but are not particularly limited to, lithium 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, the unavoidable impurities hardly affect the characteristic values of the cBN sintered body.

[0034] The coated cBN sintered body of this embodiment includes the above-described cBN sintered body and a coating layer formed on the surface of the cBN sintered body. By forming a coating layer on the surface of the cBN sintered body, the wear resistance of the cBN sintered body is further improved. The coating layer preferably contains 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. Further, the coating layer may have a single-layer structure or a laminated structure including two or more layers. When the coating layer has such a structure, the wear resistance of the coated cBN sintered body of this embodiment is further improved.

[0035] The method for manufacturing the coating layer in the coated cBN sintered body of this embodiment is not particularly limited. Examples thereof include chemical vapor deposition methods and physical vapor deposition methods such as ion plating methods, arc ion plating methods, sputtering methods, and ion mixing methods. Among them, the arc ion plating method is more preferable because it has even better adhesion between the coating layer and the cBN sintered body.

[0036] Examples of the compound for forming the coating layer include, but are not particularly limited to, TiN, TiC, TiCN, TiAlN, TiSiN, and CrAlN. The coating layer may have a structure in which a plurality of layers having different compositions are alternately laminated. In this case, the average thickness per layer of each layer is, for example, 5 nm or more and 500 nm or less.

[0037] The average thickness of the entire coating layer is preferably 0.5 μm or more and 6.0 μm or less. In the coated cBN sintered body of the present embodiment, when the average thickness of the entire coating layer is 0.5 μm or more, the wear resistance tends to improve. On the other hand, when the average thickness of the entire coating layer is 6.0 μm or less, the occurrence of defects due to peeling can be suppressed. From the same viewpoint, the average thickness of the entire coating layer is more preferably 1.0 μm or more and 5.5 μm or less, and even more preferably 1.0 μm or more and 5.0 μm or less.

[0038] The thickness of each layer constituting the coating layer and the thickness of the entire coating layer can be measured from the cross-sectional structure of the coated cBN sintered body using an optical microscope, SEM, transmission electron microscope (TEM), etc. The average thickness of each layer and the average thickness of the entire coating layer in the coated cBN sintered body can be obtained, for example, when the coating layer is formed by the arc ion plating method, in the vicinity of a position 50 μm from the cutting edge of the surface facing the metal evaporation source toward the center of the surface, from three or more cross-sections, by measuring the thickness of each layer and the thickness of the entire coating layer and calculating the average value.

[0039] In addition, the composition of each layer constituting the coating layer can be measured from the cross-sectional structure of the coated cBN sintered body using EDS, wavelength dispersive X-ray analyzer (WDS), etc.

[0040] Since the cBN sintered body or the coated cBN sintered body of the present embodiment is excellent in wear resistance and defect resistance, it is preferably used as a cutting tool or a wear-resistant tool, and among them, it is preferably used as a cutting tool. The cBN sintered body or the coated cBN sintered body of the present embodiment is more preferably used as a cutting tool for cast iron. When the cBN sintered body or the coated cBN sintered body of the present embodiment is used as a cutting tool or a wear-resistant tool, the tool life can be extended compared to the conventional case.

[0041] The cBN sintered body of the present embodiment can be manufactured, for example, by the following method. As raw material powders, cBN powder, TiC powder, TiC 0.8 powder, TiCN powder, Ti(CN)0.8 powder, TiN powder, TiN 0.8 Prepare powder, WC powder, Co powder, and Al powder. Further, by appropriately adjusting the ratio of each raw material powder, the content ratio (volume %) of cBN and the binder phase in the obtained cBN sintered body can be controlled within the above-specified range. Also, by appropriately adjusting the ratio of each raw material powder, the content ratio (volume %) of the Ti compound phase, the phase containing W element, and the Al compound phase in the binder phase can be controlled within the above-specified range. Furthermore, by appropriately adjusting the ratio of each raw material powder, the content ratio of Co element to the total content ratio of W element and Co element in the phase containing W element can be controlled within the above-specified range. Next, put the prepared raw material powder into a ball mill cylinder together with a cemented carbide ball, a solvent, and paraffin and mix them. Fill the raw material powder mixed by a ball mill into a high-melting-point metal capsule made of Zr 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, perform vacuum heat treatment with the capsule open. After the vacuum heat treatment, seal the capsule and sinter the raw material powder filled in the capsule at high temperature and high pressure. The conditions for high-pressure sintering are, for example, pressure: 4.0 - 7.0 GPa, temperature: 1250 - 1550 °C, sintering time: 20 - 60 minutes.

[0042] Let the X-ray diffraction peak intensity of the (111) plane of cBN be I 1 and let the total of the X-ray diffraction peak intensities of the (211) plane of W 2 B and the (110) plane of WB be I 2 When it is set, I 2 / I 1 As a method for controlling within the above-specified range, although not particularly limited, for example, methods such as appropriately adjusting the type and blending ratio of the raw material powder or appropriately adjusting the temperature at which the raw material powder is sintered can be mentioned. Specifically, I 2 / I 1As a method of increasing it, for example, reducing the content ratio (volume %) of cBN in the cBN sintered body, increasing the content ratio (volume %) of the W-containing phase in the binder phase, or in the raw material of the Ti compound phase, a compound raw material in which the atomic ratio of the metal element to the non-metal element is a non-stoichiometric ratio (TiC 0.8 , Ti(CN) 0.8 or TiN 0.8 ) is used, and its ratio is increased, or the temperature at which the raw material powder is sintered is increased, and further, in the phase containing the W element, the content ratio of the Co element to the total content ratio of the W element and the Co element is within the above-described range.

[0043] W in the binder phase 2 Let the sum of the X-ray diffraction peak intensities of the (211) plane of B and the (110) plane of WB be I 2 and for W in the binder phase 2 Let the X-ray diffraction peak intensity of the (211) plane of B be I 4 When it is set as I 4 / I 2 , as a method of controlling it within the above specific range, although not particularly limited, for example, adjusting the type and blending ratio of the raw material powder as appropriate, or adjusting the temperature at which the raw material powder is sintered as appropriate. Specifically, as a method of increasing I 4 / I 2 , for example, increasing the content ratio of the Co element to the total content ratio of the W element and the Co element in the phase containing the W element, or in the raw material of the Ti compound phase, a compound raw material in which the atomic ratio of the metal element to the non-metal element is a non-stoichiometric ratio (TiC 0.8 , Ti(CN) 0.8 or TiN 0.8 ) is used, and its ratio is increased, or the temperature at which the raw material powder is sintered is lowered.

[0044] Let the X-ray diffraction peak intensity of the (111) plane of cBN be I 1 and for WB in the binder phase 2 let the X-ray diffraction peak intensity of the (101) plane be I 3 When it is set as I 3 / I 1As a method for controlling to the above specific range, although not particularly limited, for example, a method of appropriately adjusting the type and blending ratio of the raw material powder or a method of appropriately adjusting the temperature at which the raw material powder is sintered can be mentioned. Specifically, I 3 / I 1 As a method for reducing, for example, in the raw material of the Ti compound phase, a compound raw material (TiC 0.8 , Ti(CN) 0.8 or TiN 0.8 ) in which the atomic ratio of the metal element and the non-metal element is a non-stoichiometric ratio can be used, or a method of lowering the temperature at which the raw material powder is sintered can be mentioned. Further, as a method for making the phase containing W in the binder phase substantially free of WB 2 , for example, in the raw material of the Ti compound phase, a compound raw material (TiC 0.8 , Ti(CN) 0.8 or TiN 0.8 ) in which the atomic ratio of the metal element and the non-metal element is a non-stoichiometric ratio is used in a specific amount or more, and the temperature at which the raw material powder is sintered is set to 1500 °C or lower. Specifically, for example, a compound raw material (TiC 0.8 , Ti(CN) 0.8 or TiN 0.8 ) is set to 50% by volume or more based on 100% by volume of the total raw material of the Ti compound phase, and the temperature at which the raw material powder is sintered is set to 1500 °C or lower, whereby the phase containing W in the binder phase tends to be substantially free of WB 2 .

[0045] When the X-ray diffraction peak intensity of the (111) plane of cBN is I 1 and the X-ray diffraction peak intensity of the (101) plane of TiB 2 in the binder phase is I 5 , as a method for controlling I 5 / I 1 to the above specific range, although not particularly limited, for example, a method of appropriately adjusting the type and blending ratio of the raw material powder or a method of appropriately adjusting the temperature at which the raw material powder is sintered can be mentioned. Specifically, I 5 / I 1As a method of increasing [it], for example, there are methods such as reducing the content ratio (volume %) of cBN in the cBN sintered body, increasing the content ratio (volume %) of the Ti compound phase in the binder phase, and increasing the temperature at which the raw material powder is sintered.

[0046] As a method of controlling the average thickness λ (μm) of the phase containing the W element within the above-specified range, although not particularly limited, for example, there is a method of appropriately adjusting the type and blending ratio of the raw material powder. Specifically, as a method of reducing the average thickness λ (μm) of the phase containing the W element, for example, there are methods such as reducing the content ratio (volume %) of the Al compound phase in the binder phase and increasing the content ratio of the Co element with respect to the total content ratio of the W element and the Co element in the phase containing the W element.

[0047] Also, in the phase containing the W element, when the content ratio of the Co element with respect to the total content ratio of the W element and the Co element is increased, the content ratio of CoW 2 B 2 tends to increase to such an extent that it can be detected by X-ray diffraction measurement.

[0048] Also, the cBN sintered body of the present embodiment can be processed into a predetermined shape by a wire electrical discharge machining machine, a laser cutting machine, etc., to manufacture a cutting tool or wear-resistant tool provided with the cBN sintered body.

Examples

[0049] Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

[0050] (Example 1) [Preparation of Raw Material Powder] cBN powder, TiC powder, TiC 0.8 powder, TiCN powder, Ti(CN) 0.8 powder, TiN powder, TiN 0.8Powder, WC powder, Co powder, and Al powder were mixed at the ratios shown in Table 2 below. The average particle size of each raw material powder was as shown in Table 1. The average particle size of the raw material powder was measured by the Fisher method (Fisher Sub-Sieve Sizer (FSSS)) described in the American Society for Testing and Materials (ASTM) standard B330.

[0051]

Table 1

[0052]

Table 2

[0053] [Mixing of Raw Material Powders] The raw material powders were placed in a cylinder for a ball mill together with cemented carbide balls, hexane solvent, and paraffin and mixed for 6 hours.

[0054] [Filling Process and Drying Process] The mixed raw material powders were 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 powders, vacuum heat treatment was performed with the capsule open. After the vacuum heat treatment, the capsule was sealed.

[0055] [Sintering Process] Thereafter, the raw material powders filled in the capsule were sintered under high temperature and high pressure. The conditions for high pressure sintering are shown in Table 3 below.

[0056]

Table 3

[0057] [Analysis by SEM Image] Regarding the cBN sintered body obtained by high-pressure sintering, the content ratios (volume %) of cBN and the bonding phase were determined by analyzing the micrograph 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 mirror-polished in a direction perpendicular to its surface. Next, using an SEM, the backscattered electron image of the mirror-polished surface of the cBN sintered body revealed by mirror polishing was observed. At this time, using an SEM, the mirror-polished surface of the cBN sintered body magnified at a magnification selected so that 100 or more and 300 or fewer cBN particles were included was observed with a backscattered electron image. By using the energy dispersive X-ray analyzer (EDS) attached to the SEM, the black region was identified as cBN, and the gray and white regions were identified as the bonding phase. Furthermore, in the bonding phase, it was identified that the dark gray region is the Al compound phase, the light gray region is the Ti compound phase, and the white region is the phase containing the W element. Thereafter, a micrograph of the above cross-section of cBN was taken using an SEM. Using commercially available image analysis software, the occupied areas of cBN and the bonding phase were determined from the obtained micrograph, and the content ratios (volume %) were determined from the occupied areas. Also, the content ratios (volume %) of the Ti compound phase, Al compound phase, and the phase containing the W element in the bonding phase were similarly calculated from the micrograph based on the ratios of the respective phases to the exclusive area of the bonding phase. Here, the mirror-polished surface of the cBN sintered body was defined as the cross-section of the cBN sintered body obtained by mirror-polishing the surface or an arbitrary cross-section of the cBN sintered body. The method for obtaining the mirror-polished surface of the cBN sintered body was the method of polishing using diamond paste. Also, the composition of the bonding phase was 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 composition of the bonding phase. Output: 45 kV, 200 mA, Incident-side Soller slit: 5°, Divergent vertical slit: 2 / 3°, Divergent vertical limiting slit: 5 mm, Scattering slit 2 / 3°, Receiving-side Soller slit: 5°, Receiving slit: 0.3 mm, Sampling width: 0.02°, Scan speed: 1° / min, 2θ measurement range: 30 to 90°. These measurement results are shown in Table 4 below. Also, in the phase containing the W element, when the Co element is included, the content ratio (atomic %) of the Co element with respect to the total content ratio of the W element and the Co element was calculated as follows. First, in the same observation field as the microstructure photograph of the cBN sintered body taken by SEM in the same manner as above, EDS analysis of the entire field of view was performed to measure the content ratios (atomic %) of the W element and the Co element contained in the cBN sintered body. From the obtained values, the content ratio (atomic %) of the Co element with respect to the total content ratio of the W element and the Co element was calculated. The results are shown in Table 5.

[0058] [Analysis by X-ray diffraction (XRD)] Analysis by X-ray diffraction (XRD) was performed on the Ti compound phase, the Al compound phase, and the phase containing the W element contained in the cBN sintered body obtained by the sintering process. The analysis results of the Ti compound phase, the Al compound phase, and the phase containing the W element by XRD are shown in Table 5 below. In Table 5, only the phases for which distinct peaks were identified by X-ray diffraction measurement are shown. For the phase containing the W element, except for Comparative Product 10, it was specified from the analysis using EDS that there is a phase containing both the W element and the Co element. Also, except for Invention Product 12 and Comparative Product 11, distinct peaks of the phase containing both the W element and the Co element could not be identified by X-ray diffraction measurement, but except for Comparative Product 10, it was confirmed that the Co element is contained in the phase containing the W element, and in Invention Product 12 and Comparative Product 11, CoW 2 B 2 was detected. From this, it is presumed that the samples other than Invention Product 12, Comparative Product 10, and Comparative Product 11 contain at least CoW 2 B 2 in a proportion that is not detected by X-ray diffraction measurement. Also, from the obtained X-ray diffraction pattern, the X-ray diffraction peak intensity of the (111) plane of cBN, and the W in the bonding phase 2 B's (211) plane, WB's (110) plane, WB2 The (101) plane of 2 and the X-ray diffraction peak intensity of the (101) plane of TiB were determined, and each ratio was calculated. The X-ray diffraction intensity ratio was determined by the ratio of peak heights. These results are shown in Table 6 below. Note that the XRD measurement was performed using an X-ray diffractometer (product name "SmartLab") manufactured by Rigaku Corporation, with a 2θ / θ focusing optical system using Cu-Kα rays. The measurement conditions were the same as those in the method for identifying the composition of the bonded phase described above. Also, the identification of each peak was based on the following PDF cards. cBN: No.00-035-1365 W 2 B: No.01-089-1991 WB: No.00-006-0541 WB 2 : No.01-089-3928 TiB 2 : No.00-035-0741

[0059] [Method for calculating the average thickness λ of the phase containing W element] It was determined by combining the observation of the backscattered electron image of the cross-sectional structure and the analysis by EDS. It was identified that the black region in the backscattered electron image of the cross-sectional structure is cBN, the dark gray region is the Al compound phase, the light gray region is the Ti compound phase, and the white region is the phase containing the W element. The average thickness λ (μm) of the phase containing the W element was calculated from the following formula. The results are shown in Table 7. λ = X / N L X: In the cross-sectional structure, the ratio of the area occupied by the phase containing the W element to the area occupied by the entire bonded phase was determined. N L : In the cross-sectional structure, when an arbitrary straight line is drawn, N is obtained by dividing the total number of phases containing the W element intercepted by the straight line by the total length of the bonded phase intercepted by the straight line. L was determined.

[0060]

Table 4

[0061]

Table 5

[0062]

Table 6

[0063]

Table 7

[0064] [Fabrication of Cutting Tool] The obtained cBN sintered body was cut out to match the insert shape tool shape defined by ISO standard CNGA120408 using a wire electrical discharge machining machine. The cut cBN sintered body was joined to a base alloy made of cemented carbide by brazing. The brazed tool was subjected to honing to obtain a cutting tool.

[0065] [Cutting Test] A cutting test was conducted under the following conditions using the obtained cutting tool. Workpiece material: SCM415H case-hardened and quenched steel (HRC60), Workpiece material shape: round bar, φ80mm×200mm, Machining method: external turning, Cutting speed: 250 m / min, Feed: 0.1 mm / rev, Depth of cut: 0.1 mm, Coolant: used (water-soluble coolant), Evaluation item: The tool life was defined as the time when the flank wear width of the tool reached 0.10 mm or when chipping occurred, and the machining time until the tool life was measured. Also, the damage form of the sample when the flank wear width of the tool reached 0.10 mm and the tool life was achieved was defined as "normal wear", and the damage form of the sample when chipping occurred and the tool life was achieved was defined as "chipping". The measurement results are shown in Table 8.

[0066]

Table 8

[0067] As can be seen from the results shown in Table 8, the cutting tool using the cBN sintered body of the invention product is superior in wear resistance and chipping resistance to the cutting tool using the cBN sintered body of the comparative product, and has a long tool life.

[0068] (Example 2) Next, as shown in Table 9, after subjecting the surfaces of the cBN sintered bodies of Invention Products 2, 5, 8, and 9 obtained in Example 1 to ion bombardment treatment, a coating layer was formed by the arc ion plating method. When forming the first layer and the second layer, they were formed on the surface of the cBN sintered body in this order. The respective treatment conditions were as follows. Also, the composition and average thickness of the coating layer were as shown in Table 9 below. Note that the composition of the first layer, Ti 0.50 Al 0.50 N / Ti 0.33 Al 0.67 Regarding N, 50 nm of Ti per layer 0.50 Al 0.50 N and Ti 0.33 Al 0.67 N and were alternately and repeatedly formed. At this time, the alternately and repeatedly formed Ti 0.50 Al 0.50 N / Ti 0.33 Al 0.67 N was formed so that the total thickness became the average thickness of the first layer.

[0069] [Ion bombardment treatment conditions] Substrate temperature: 500 °C Pressure: Ar gas atmosphere of 2.7 Pa Voltage: -400 V Current: 40 A Time: 30 minutes

[0070] [Coating layer formation conditions] Substrate temperature: 500 °C Pressure: Nitrogen (N 2 ) gas atmosphere (nitride layer) of 3.0 Pa, or nitrogen (N 2 ) gas and acetylene gas (C2 H 2 ) Mixed gas atmosphere with gas (carbonitride layer) Voltage: -60 V Current: 120 A

[0071]

Table 9

[0072] Using a coated cBN sintered body with a coating layer formed on the surface, a cutting test was conducted in the same manner as in Example 1. The results are shown in Table 10 below.

[0073]

Table 10

[0074] As can be seen from the results shown in Table 10, the coated cBN sintered bodies (Inventive articles 26 to 45) with a coating layer formed on their surfaces are more wear-resistant than the cBN sintered bodies without a coating layer (Inventive articles 1 to 25), and have a longer tool life.

Industrial Applicability

[0075] The cBN sintered body and the coated cBN sintered body of the present invention are excellent in wear resistance and chipping resistance, so that the tool life can be extended compared with the prior art, and thus have high industrial applicability in that regard.

Claims

1. A cubic boron nitride sintered body containing cubic boron nitride and a binder phase, with respect to 100.0% by volume of the entire cubic boron nitride sintered body, the content ratio of the cubic boron nitride is 10.0% by volume or more and 60.0% by volume or less, and the content ratio of the binder phase is 40.0% by volume or more and 90.0% by volume or less, the binder phase includes a Ti compound phase, an Al compound phase, and a phase containing a W element, with respect to 100.0% by volume of the entire binder phase, the content ratio of the Ti compound phase is 60.0% by volume or more and 92.0% by volume or less, the content ratio of the Al compound phase is more than 0.0% by volume and less than 15.0% by volume, and the content ratio of the phase containing a W element is 5.0% by volume or more and 30.0% by volume or less, The phase containing the W element is W 2 and includes at least one selected from the group consisting of B and WB, The X-ray diffraction peak intensity of the (111) plane of the cubic boron nitride is I 1 Let it be, and the total of the X-ray diffraction peak intensities of the (211) plane of WB and the (110) plane of WB in the binder phase is I 2 When it is, I 2 When it is, I 2 / I 1 Is 0.03 or more and 0.60 or less, a cubic boron nitride sintered body.

2. WB in the binding phase 2 When the X-ray diffraction peak intensity of the (101) plane of 3 is I 3 / I 1 is 0.03 or less, the cubic boron nitride sintered body according to claim 1.

3. W in the bonding phase 2 When the X-ray diffraction peak intensity of the (211) plane of B is I 4 When taken as such, I 4 / I 2 is 0.50 or more and 0.95 or less. The cubic boron nitride sintered body according to claim 1

4. The cubic boron nitride sintered body according to Claim 1, wherein the average thickness λ of the phase containing a W element is 0.03 μm or more and 0.12 μm or less.

5. The Ti compound phase contains TiB 2 and TiB in the binding phase 2 When the X-ray diffraction peak intensity of the (101) plane of is I 5 When it is, I 5 / I 1 is 0.07 or more and 0.55 or less, The cubic boron nitride sintered body according to claim 1.

6. The phase containing a W element contains a Co element, In the phase containing a W element, the content ratio of the Co element to the total content ratio of the W element and the Co element is 5 atomic% or more and less than 50 atomic%. The cubic boron nitride sintered body according to Claim 1.

7. A coated cubic boron nitride sintered body, comprising the 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, wherein the average thickness of the entire coating layer is 0.5 μm or more and 6.0 μm or less.

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