Cubic boron nitride sintered body and cutting tool including the same

Abstract

The cubic boron nitride sintered body is a cubic boron nitride sintered body comprising 70 volume% or more and less than 100 volume% of cubic boron nitride particles and a binder, wherein the binder includes an aluminum compound and also includes cobalt as a constituent element, and the cubic boron nitride sintered body has a first region in which the spacing between adjacent cubic boron nitride particles is 0.1 nm or more and 10 nm or less, and when the first region is analyzed using an energy-dispersive X-ray analysis device equipped with a transmission electron microscope, the atomic percentage of aluminum in the first region is 0.1 or more.

Description

Technology Field

[0001] The present disclosure relates to a cubic boron nitride sintered body and a cutting tool comprising the same. The present application claims priority based on Japanese Patent Application No. 2020-130672 filed on July 31, 2020. All contents of the said Japanese patent application are incorporated herein by reference. Background Technology

[0002] Cubic boron nitride sintered bodies (hereinafter also referred to as "cBN sintered bodies") are high-hardness materials used in cutting tools and the like. CBN sintered bodies are typically composed of cubic boron nitride particles (hereinafter also referred to as "cBN particles") and a binder, and their properties tend to differ depending on the content ratio of the cBN particles.

[0003] For this reason, in the field of cutting processes, the types of cBN sintered bodies applied to cutting tools are distinguished and used according to the material of the workpiece and the required machining precision. For example, a cBN sintered body with a high content of cubic boron nitride (hereinafter also referred to as "cBN") (hereinafter also referred to as "High-cBN sintered body") can be suitablely used for cutting sintered alloys, etc.

[0004] However, High-cBN sintered bodies tend to be prone to sudden defects. This is thought to be due to the weak bonding force between cBN particles, causing the cBN particles to detach. For example, International Publication No. 2005 / 066381 (Patent Document 1) discloses a technique for suppressing the occurrence of sudden defects in High-cBN sintered bodies by selecting an appropriate binder. Prior art literature

[0005] Patent Document 1: International Publication No. 2005 / 066381

[0006] A cubic boron nitride sintered body according to one embodiment of the present disclosure is a cubic boron nitride sintered body comprising 70 volume% or more and less than 100 volume% of cubic boron nitride particles and a binder, wherein the binder comprises an aluminum compound and also comprises cobalt as a constituent element, and the cubic boron nitride sintered body has a first region in which the spacing between adjacent cubic boron nitride particles is 0.1 nm or more and 10 nm or less, and when the first region is analyzed using an energy-dispersive X-ray analysis device equipped with a transmission electron microscope, the atomic percentage of aluminum in the first region is 0.1 or more.

[0007] A cutting tool according to one embodiment of the present disclosure comprises the cubic boron nitride sintered body. Brief explanation of the drawing

[0008] FIG. 1 is an example of a second image obtained from a cBN sintered body according to the present embodiment. Figure 2 is an example of a graph illustrating the results of element line analysis. Specific details for implementing the invention

[0009] [Problems to be solved by the present disclosure]

[0010] Recently, due to the rapid increase in the functionality of machine parts, the difficulty of machining workpieces used as machine parts is accelerating. Consequently, the problem of increased costs resulting from the shortened lifespan of cutting tools is becoming a reality. For this reason, further improvement of High-cBN sintered bodies is required. Taking this into account, the present disclosure aims to provide a cubic boron nitride sintered body that enables a long lifespan and a cutting tool comprising the same.

[0011] [Effects of the present disclosure]

[0012] According to the present disclosure, a cubic boron nitride sintered body that enables a long lifespan and a cutting tool including the same can be provided.

[0013] [Description of embodiments of the present disclosure]

[0014] To solve the above problem, the inventors conceived of realizing a long lifespan by increasing the bonding strength between cBN particles in a High-cBN sintered body. Subsequently, as a result of carefully examining the cause of weakening the bonding strength between cBN particles in a High-cBN sintered body, it was discovered that an oxygen layer (oxide film) present on the surface of the cBN particles inhibits sintering between the cBN particles and between the cBN particles and the binder.

[0015] Based on the above findings, the inventors have devised a structure of "cBN particle / Al layer (hereinafter also referred to as "adhesion layer") / cBN particle" between adjacent cBN particles by sintering the cBN particles and the cBN particles after placing Al, which has a higher reactivity with cBN particles than oxygen, around the cBN particles. Since the adhesion layer has a bonding strength stronger than the bonding strength between cBN particles covered by the oxide film, the detachment of cBN particles during cutting can be suppressed by providing the above structure, thereby enabling a long lifespan, and thus the present disclosure has been reached. Furthermore, it was discovered that the adhesion layer suppresses thermal cracking by having the effect of mitigating thermal shrinkage based on heat generated during cutting, and thus the stability against defects in the present disclosure has been significantly improved. The first embodiment of the present disclosure will be described below.

[0016] [1] A cubic boron nitride sintered body according to one embodiment of the present disclosure is a cubic boron nitride sintered body comprising 70 volume% or more and less than 100 volume% of cubic boron nitride particles and a binder, wherein the binder includes an aluminum compound and also includes cobalt as a constituent element, and the cubic boron nitride sintered body has a first region in which the spacing between adjacent cubic boron nitride particles is 0.1 nm or more and 10 nm or less, and when the first region is analyzed using an energy-dispersive X-ray analysis device equipped with a transmission electron microscope, the atomic percentage of aluminum in the first region is 0.1 or more. A cubic boron nitride sintered body having these characteristics can achieve a long lifespan of the cutting tool when applied to a cutting tool.

[0017] [2] When the spacing between adjacent cubic boron nitride particles in the first region is 0.1 nm or more and 7.0 nm or less, it is preferable that the atomic percentage of aluminum in the first region be 0.5 or more. This allows for a longer lifespan to be more fully realized for the cutting tool.

[0018] [3] The first region above comprises at least one first element selected from the group consisting of chromium, titanium, vanadium, cobalt, zirconium, tungsten, niobium, hafnium, tantalum, rhenium, silicon, and molybdenum as a constituent element, and aluminum. When the first region is analyzed using an energy-dispersive X-ray analysis device equipped with a transmission electron microscope, the atomic percentage of aluminum is M, and the atomic percentage of the element present at the highest concentration among the first elements is M1, and the ratio M1 / (M+M1) is preferably 0.50 or less. This allows for a longer lifespan to be more fully realized for the cutting tool.

[0019] [4] It is preferable that the ratio M1 / (M+M1) is 0.010 or higher and 0.30 or lower. This allows for a longer lifespan to be more fully realized for the cutting tool.

[0020] [5] The above cubic boron nitride sintered body preferably contains 80 volume% or more and 95 volume% or less of the cubic boron nitride particles. By doing so, the cubic boron nitride sintered body with a very high content of cBN particles can achieve a long lifespan for the cutting tool.

[0021] [6] A cutting tool according to one aspect of the present disclosure comprises the cubic boron nitride sintered body. A cutting tool having these features can achieve a long lifespan.

[0022] [Details of embodiments of the present invention]

[0023] Hereinafter, an embodiment of the present invention (hereinafter also referred to as "this embodiment") will be described. However, this embodiment is not limited thereto. Furthermore, in this specification, notations in the form of "A to B" indicate upper and lower limits of a range (i.e., A or greater and B or less). If a unit is not specified in A and a unit is specified only in B, the unit of A and the unit of B are identical. Additionally, when a compound, etc. is represented by a chemical formula in this specification, unless the atomic ratio is specifically limited, it shall include all conventionally known atomic ratios and shall not necessarily be limited only to those within the stoichiometric range.

[0024] [Cubic Boron Nitride Sintered Body (cBN Sintered Body)]

[0025] The cubic boron nitride sintered body (cBN sintered body) according to the present embodiment is a cBN sintered body comprising 70 volume% or more and less than 100 volume% of cubic boron nitride particles (cBN particles) and a binder. The binder includes an aluminum compound (Al compound) and also includes cobalt (Co) as a constituent element. The cBN sintered body has a first region in which the spacing between adjacent cBN particles is 0.1 nm or more and 10 nm or less. When the first region is analyzed using an energy-dispersive X-ray analysis device equipped with a transmission electron microscope (hereinafter also referred to as "TEM-EDX"), the atomic percentage of aluminum (Al) in the first region is 0.1 or more. When a cBN sintered body having these characteristics is applied to a cutting tool, it can realize a long lifespan for the cutting tool.

[0026] Cubic Boron Nitride (cBN) Particles

[0027] The cBN sintered body according to the present embodiment comprises cBN particles in an amount of 70 volume% or more and less than 100 volume% as described above. It is preferable that the cBN sintered body contains cBN particles in an amount of 70 volume% or more and 99 volume% or less, and it is more preferable that it contains cBN particles in an amount of 80 volume% or more and 95 volume% or less. That is, the cBN sintered body is a so-called High-cBN sintered body. The cBN particles have high hardness, strength, and toughness, and serve as a framework within the cBN sintered body. The content (volume%) of cBN particles in the cBN sintered body is substantially the same amount as the content (volume%) of the cBN raw powder (coated cBN powder) used in the mixed powder described later. This is because, although the material inside the capsule containing the mixed powder may melt during ultra-high pressure sintering, the amount of the molten material is minimal; therefore, the content of cBN particles in the cBN sintered body and the content of cBN particles in the mixed powder can be considered substantially the same. By controlling the content of the cBN raw powder used in the mixed powder in this way, the content of cBN particles within the cBN sintered body can be prepared within a desired range.

[0028] The content (volume %) of cBN particles in a cBN sintered body can be confirmed by performing quantitative analysis by inductively coupled high-frequency plasma spectroscopy (ICP) on the cBN sintered body, structural observation using an energy dispersive X-ray analyzer (EDX) equipped with a scanning electron microscope (SEM) or EDX equipped with a transmission electron microscope (TEM), and elemental analysis.

[0029] For example, when using SEM, the content (volume %) of cBN particles can be determined as follows. First, a sample containing a cross-section of the cBN sintered body is prepared by cutting at an arbitrary location on the cBN sintered body. A focused ion beam device, a cross-section polisher device, etc., may be used to prepare the cross-section. Subsequently, a reflected electron image is obtained by observing the cross-section at 2000x magnification using SEM. In the reflected electron image, the region where cBN particles are present appears as a black region, and the region where the binder is present appears as a gray region or a white region, respectively.

[0030] Next, binarization processing is performed on the above-mentioned reflected electron image using image analysis software (e.g., "WinROOF" of Mitani Shoji Bushiki Kaisha), and the area ratios are calculated from the image after the binarization processing. Subsequently, by assuming that the area ratios are continuous in the depth direction of the cross-section, the area ratios can be obtained as the content (volume %) of cBN particles in the cBN sintered body. In addition, the content (volume %) of the binder described later can be obtained simultaneously by this measurement method.

[0031] D based on the area of ​​cBN particles 50 (Average particle size) is not particularly limited and can be, for example, 0.1 to 10 μm. Typically D 50 The smaller side tends to have higher hardness in the cBN sintered body, and the side with smaller grain size variation tends to have more homogeneous properties in the cBN sintered body. D of cBN particles 50 It is preferable to make the size 0.5 to 4 μm.

[0032] D of cBN particles 50The result is obtained as follows. First, a reflected electron image is obtained by preparing a sample containing a cross-section of a cBN sintered body in accordance with the cBN particle content measurement method described above. Next, the circle equivalent diameter of each black region in the reflected electron image is calculated using the image analysis software described above. In this case, it is preferable to calculate the circle equivalent diameters of 100 or more cBN particles by observing at least 5 fields of view.

[0033] Next, the cumulative distribution is obtained by arranging the equivalent diameters of each circle in ascending order from the minimum to the maximum. In the cumulative distribution, the particle size at which the cumulative area is 50% is D. 50 This becomes. Here, the circle equivalent diameter refers to the diameter of a circle having the same area as the measured area of ​​the cBN particle.

[0034] <Binder: Composition other than cBN particles>

[0035] The cBN sintered body according to the present embodiment is provided with a binder as described above. In addition, the cBN sintered body may contain unavoidable impurities resulting from the raw materials used, manufacturing conditions, etc. In this case, the cBN sintered body consists of cBN particles, a binder, and unavoidable impurities. As for the content (volume%) of the binder, it is preferable to be greater than 0 volume% and less than or equal to 30 volume%, and more preferable to be 5 to 20 volume%. The binder plays a role in enabling cBN particles, which are difficult-to-sinter materials, to be sintered at an industrial-level pressure temperature.

[0036] The above binder comprises an Al compound and also comprises Co as a constituent element. The statement that the above binder "comprising Co as a constituent element" means that the above binder comprises at least one of the following: a monometallic Co, a Co alloy, or a mutual solid solution composed of Co and at least one selected from the group consisting of carbon, nitrogen, and oxygen. Examples of Al compounds include CoAl, Al2O3, AlN, and AlB2, and composite compounds thereof. In particular, it is preferable that the above binder comprises WC (tungsten carbide), a monometallic Co, a Co alloy, or either one thereof, and an Al compound. For the following reasons, these components in the binder are considered to be particularly effective in extending the lifespan of the cBN sintered body.

[0037] First, since Co and Al have catalytic functions, they can promote the bonding of cBN particles in the sintering process described later. Second, WC is presumed to be effective in bringing the coefficient of thermal expansion of the binder close to the coefficient of thermal expansion of the cBN particles. Here, the aforementioned catalytic function refers to the function of promoting the diffusion or precipitation of B (boron) and N (nitrogen) constituting the cBN particles through Co or Al.

[0038] The above binder may include other components in addition to WC, an Al compound, and Co as a constituent element. It is preferable that the other component of the binder include at least one element selected from the group consisting of chromium (Cr), titanium (Ti), vanadium (V), zirconium (Zr), tungsten (W), niobium (Nb), hafnium (Hf), tantalum (Ta), rhenium (Re), silicon (Si), and molybdenum (Mo). By incorporating at least one element selected from the above group into the Al compound, a greater number of Al layers (adhesion layers) that are strongly bonded to the cBN particles can be created between adjacent cBN particles. The content of at least one element selected from the above group in the binder is preferably 50 atomic percent or less, and more preferably 30 atomic percent or less, from the viewpoint of preventing inhibition of the reaction between Al and cBN. In addition, since at least one element selected from the above group is a component for obtaining the desired effect of the present disclosure, the lower limit may be 0 atomic%. Here, in this specification, "Al layer (adhesion layer)" refers to a layer (region) containing Al as a binder component among the binder layers occupying the space between adjacent cBN particles within the cBN sintered body. In addition, "Al layer (adhesion layer)" may refer to the first region described below. Furthermore, the content (atomic%) of at least one element selected from the above group in the binder is determined by taking the total elements measured by the following XRD and ICP analysis as 100 atomic%.

[0039] The composition of the binder can be determined by combining XRD (X-ray diffraction measurement) and ICP. Specifically, first, a test specimen with a thickness of approximately 0.45 to 0.5 mm is cut from a cBN sintered body, and by performing XRD analysis on this specimen, compounds, metals, etc., determined from the X-ray diffraction peaks are determined. Next, the specimen is immersed in hydrofluoric acid (a mixed acid with a volume ratio of concentrated nitric acid (60%):distilled water:concentrated hydrofluoric acid (47%) = 2:2:1) in a sealed container to obtain an acid treatment solution in which the binder is dissolved. In addition, ICP analysis is performed on the acid treatment solution to perform quantitative analysis of each metal element. Finally, the composition of the binder can be determined by interpreting the results of the XRD and the ICP analysis.

[0040] Examples of unavoidable impurities that may be included in the cBN sintered body according to the present embodiment include iron, magnesium, calcium, sodium, lithium, etc. The above unavoidable impurities may be included in the cBN sintered body as impurities alone in an amount of 0.01 mass% or less, or as a total amount of all impurities in an amount of 0.1 mass% or less. In this specification, regarding "unavoidable impurities" that may be included in the cBN sintered body, they are treated as a third component other than cBN and binder.

[0041] <Section 1>

[0042] The cBN sintered body according to the present embodiment has a first region in which the spacing between adjacent cBN particles is 0.1 nm or more and 10 nm or less. When the first region is analyzed using an energy-dispersive X-ray analysis device (TEM-EDX) equipped with a transmission electron microscope, the atomic percentage of Al in the first region is 0.1 or more. The first region is a region formed in the region where a binder exists within the cBN sintered body.

[0043] (Analysis by TEM-EDX)

[0044] The first region can be identified by analyzing, using TEM-EDX, a region within the cBN sintered body where cBN particles are adjacent to each other to form a structure of "cBN particle / binder layer / cBN particle" (hereinafter also referred to as the "first structure"). Below, a method for identifying the first region using TEM-EDX will be described.

[0045] First, a sample is taken from a cBN sintered body, and a thinned section with a thickness of 30 to 100 nm is prepared from the sample using an argon ion slicer. Subsequently, the section is photographed using a TEM (transmission electron microscope) at a magnification in which 10 to 30 cBN particles are observed in one field of view, thereby obtaining a first image. In addition, in the first image, one region in which an interfacial structure of the cBN particles is formed by the proximity of the cBN particles is arbitrarily selected. At this time, regarding the region in which the interfacial structure of the cBN particles is tilted in the depth direction with respect to the field of view, the region is excluded from selection or the section is finely adjusted so that the interfacial structure of the cBN particles tilted in the depth direction becomes perpendicular to the field of view. This is because there is a concern that the measurement of the distance between particles (D) described later and the elemental line analysis described later cannot be properly performed when the interface shape structure of the above cBN particles is tilted in the depth direction with respect to the field of view of observation. Subsequently, a position is determined so that the selected region in which the above interface shape structure is formed passes near the center of the image, and by changing the observation magnification to 2 million times and observing, a second image of size 100 nm × 100 nm is obtained. In the second image, the region in which the above interface shape structure is formed exists in such a way that it extends from one end of the image, which is the region in which the first structure is formed, through near the center of the image, to another end (the other end) opposite to this end.

[0046] Next, a profile of HAADF image intensity is obtained by performing elemental line analysis in a direction perpendicularly intersecting the region where the aforementioned interface shape structure is formed, as confirmed in the second image. In addition, the difference from the background to the peak value in the profile is calculated, and then two points on the profile that are half the value of this difference are extracted, and the distance between these two points is defined as the inter-particle distance (D). This inter-particle distance (D) corresponds to the spacing between adjacent cBN particles. That is, since the region where the interface shape structure is formed is detected as being greater (stronger) than the intensity of the region where cBN particles exist as HAADF image intensity, it can be used to quantify the spacing between adjacent cBN particles (inter-particle distance (D)). When the inter-particle distance (D) is 0.1 nm or more and 10 nm or less, that region is specified as the first region.

[0047] In the specific method of the first region described above, it is preferable to prepare a second image of 10 fields of view for the cBN sintered body used as a sample. In this specification, the analysis described above is repeated based on the second image of 10 fields of view, and if a region in which the distance between particles (D) is 0.1 to 10 nm is identified in at least 6 fields of view or more of the second image (i.e., if the first region is observed), the cBN sintered body used as a sample is considered to have a first region.

[0048] Here, FIG. 1 is an example of a second image obtained from a cBN sintered body according to the present embodiment. Referring to FIG. 1, the black region corresponds to a region where B and N are the main constituent elements (a region where cBN particles exist), and the white region or gray region corresponds to a region where binder components other than B and N exist. In addition, the entire second image corresponds to a "region where an interfacial shape structure of cBN particles is formed" selected from the first image.

[0049] FIG. 2 is an example of a graph illustrating the results of elemental line analysis. In the graph, the distance (nm) at which elemental line analysis was performed is plotted on the horizontal axis, and the HAADF image intensity (au) calculated from the results of elemental line analysis is plotted on the vertical axis. The “distance (D)” shown in FIG. 2 refers to the “distance between particles (D)” obtained by calculating the difference from the background to the peak value and then extracting two points on the profile that are half the value of this difference.

[0050] (Atomic percentage of aluminum in the first region)

[0051] In the cBN sintered body according to the present embodiment, when the first region is analyzed using TEM-EDX, the atomic percentage of Al in the first region is 0.1 or higher. The atomic percentage of Al can be obtained from the elemental line analysis results for the second image described above. Specifically, as the atomic percentage of Al, the maximum value of the Al peak excluding the background value obtained from the elemental line analysis results is adopted. This is because if the area of ​​the Al peak obtained from the elemental line analysis is adopted as the atomic percentage of Al, the analysis error increases. Furthermore, the atomic percentage of Al in the first region is determined by setting the total element measured in the elemental line analysis to 100 atomic percentage.

[0052] In this specification, "the atomic percentage of Al in the first region is 0.1 or more" means that the average value of the atomic percentage of Al in six or more first regions, in which the distance between particles (D) in the second image of 10 fields of view extracted from the cBN sintered body used as a sample is specified to be 0.1 nm or more or 10 nm or less, is 0.1 or more. The upper limit of the atomic percentage of Al in the first region is not particularly limited. Any upper limit may be taken as long as it is measurable. For example, the atomic percentage of Al in the first region may be 50 or less, 30 or less, or 15 or less.

[0053] Here, in the cBN sintered body according to the present embodiment, when the spacing between adjacent cubic boron nitride particles in the first region is 0.1 nm or more and 7.0 nm or less, it is preferable that the atomic percentage of Al is 0.5 or more. When the atomic percentage of Al in the first region is 0.5 or more, the bonding strength between cBN particles can be further increased. Accordingly, when the cBN sintered body is applied to a cutting tool, the long lifespan of the cutting tool can be more sufficiently realized.

[0054] (Other elements in the first domain)

[0055] The first region preferably comprises at least one first element selected from the group consisting of chromium (Cr), titanium (Ti), vanadium (V), cobalt (Co), zirconium (Zr), tungsten (W), niobium (Nb), hafnium (Hf), tantalum (Ta), rhenium (Re), silicon (Si), and molybdenum (Mo) as constituent elements, and Al. In this case, when the first region is analyzed using an energy-dispersive X-ray analyzer (TEM-EDX) equipped with a transmission electron microscope, the ratio M1 / (M+M1) is preferably 0.50 or less, where M is the atomic percentage of Al and M1 is the atomic percentage of the element present at the highest concentration among the first elements. It is more preferable that the ratio M1 / (M+M1) is 0.010 or more and 0.30 or less. When a cBN sintered body having these characteristics is applied to a cutting tool, the long lifespan of the cutting tool can be more fully realized.

[0056] Here, in this specification, "M1" in the ratio M1 / (M+M1) refers to the atomic percentage value of the element present at the highest concentration in the first region among the first elements, as described above. Accordingly, the first elements included in the first region satisfy the relationship in which the ratio M1 / (M+M1) is 0.50 or less between the atomic percentage of the element present at the highest concentration among them and the atomic percentage of aluminum, and each first element satisfies the relationship in which "atomic percentage of the first element / (atomic percentage of the first element + atomic percentage of aluminum) is 0.50 or less" between the atomic percentage of the element present at the highest concentration among them and the atomic percentage of aluminum. Furthermore, it is more preferable that the first elements included in the first region satisfy the relationship in which the ratio M1 / (M+M1) is 0.010 or more and 0.30 or less between the atomic percentage of the element present at the highest concentration among them in the first region and the atomic percentage of aluminum. In addition, the first element included in the first region may be just one selected from the group mentioned above, or two or more.

[0057] The value of the ratio M1 / (M+M1) in the first region can be obtained in the same manner as the atomic % value of Al in the first region. That is, based on the maximum peak value of the element present at the highest concentration in the first region among the first elements obtained from the element line analysis results and the maximum peak value of Al, the atomic % value (M1) of the element present at the highest concentration in the first region among the first elements and the atomic % value (M) of Al are obtained. Subsequently, the ratio M1 / (M+M1) can be calculated by dividing M1 by the sum of M1 and M (M+M1). In addition, the statement “ratio M1 / (M+M1) is 0.50 or less (0.010 or more and 0.30 or less)” in this specification means that the average value of each ratio M1 / (M+M1) in six or more first regions, in which the distance between particles (D) is specified to be 0.1 nm or more and 10 nm or less in a second image of 10 fields of view extracted from a cBN sintered body used as a sample, is 0.50 or less (0.010 or more and 0.30 or less).

[0058] <Action>

[0059] The cBN sintered body according to the present embodiment has an atomic percentage of Al in the first region of the above-described first region of 0.1 or more. In this case, although the detailed mechanism is unclear, it is inferred that the cBN sintered body has a higher bonding strength between cBN particles for the following reasons, thereby enabling a longer lifespan. That is, the fact that the atomic percentage of Al in the first region of the above-described first region is 0.1 or more means that a large amount of Al is contained (high concentration) in the first region (between adjacent cBN particles). When Al is present at a high concentration in the first region, Al, which has high reactivity with cBN particles, can react with the cBN particles more during sintering. Accordingly, it is thought that numerous "cBN particle / Al layer (adhesion layer) / cBN particle" structures can be created between adjacent cBN particles, thereby increasing the bonding strength between the cBN particles.

[0060] In addition, it is desirable that each element included in the group consisting of Cr, Ti, V, Co, Zr, W, Nb, Hf, Ta, Re, Si, and Mo be included in the first region such that the ratio M1 / (M+M1) satisfies a relationship of 0.50 or less, because this can improve the hardness of the adhesion layer produced by sintering. In this case, it is inferred that as the physical properties of the adhesion layer bonding the cBN particles are improved, the bonding strength between the cBN particles becomes sufficiently high, thereby suppressing the detachment of cBN particles during cutting and enabling a long lifespan.

[0061] [Cutting Tool]

[0062] The cutting tool according to the present embodiment comprises the cBN sintered body. Specifically, it is preferable that the cutting tool comprises the cBN sintered body as a substrate. A film may be coated on a part or all of the surface of the cBN sintered body serving as the substrate.

[0063] The shape and use of the cutting tool according to the present embodiment are not particularly limited. For example, the shape and use of the cutting tool may include a drill, an end mill, a cutting chip with an interchangeable blade for a drill, a cutting chip with an interchangeable blade for an end mill, a cutting chip with an interchangeable blade for milling, a cutting chip with an interchangeable blade for turning, a metal saw, a gear cutting tool, a reamer, a tap, a chip for milling a crankshaft pin, etc.

[0064] Furthermore, the cutting tool according to the present embodiment is not limited to the entire tool being made of a cBN sintered body, but also includes cases where only a part of the tool (particularly the blade portion (cutting edge portion), etc.) is made of a cBN sintered body. For example, a cutting tool according to the present embodiment includes cases where only the blade portion of a base (support) made of cemented carbide, etc., is composed of a cBN sintered body. In this case, the blade portion may be considered as a cutting tool based on the wording. In other words, even if the cBN sintered body occupies only a part of the cutting tool, the cBN sintered body is referred to as a cutting tool.

[0065] The cutting tool according to the present embodiment may include a coating that covers at least the blade portion. In this case, the coating may be formed on the blade portion of the cBN sintered body by a conventionally known method. The method for forming the coating may include physical vapor deposition methods such as ion plating, arc ion plating, sputtering, and ion mixing. Additionally, the coating may be formed by chemical vapor deposition. The composition of the coating is not particularly limited, and any conventionally known coating may be adopted. For example, examples of coating compositions include AlTiSiN, AlCrN, TiZrSiN, CrTaN, HfWSiN, CrAlN, TiN, TiBNO, TiCN, TiCNO, TiB2, TiAlN, TiAlCN, TiAlON, TiAlONC, Al2O3, etc.

[0066] Since the cutting tool according to the present embodiment includes the cBN sintered body, it is possible to suppress the detachment of cBN particles during cutting, thereby enabling a long lifespan.

[0067] [Method for manufacturing a cubic boron nitride sintered body]

[0068] Regarding the method for manufacturing a cBN sintered body according to the present embodiment, there are no particular limitations as long as a cBN sintered body as described above can be obtained that enables long life when applied to a cutting tool. However, from the perspective of yield, etc., it is preferable to obtain a cBN sintered body by, for example, the following manufacturing method. The inventors have discovered that in the process of manufacturing a cBN sintered body, a cBN sintered body capable of long life can be manufactured by preparing a raw material powder of a binder with a high Al content as described below, and by applying a coating technology different from the conventional one to the surface of the raw material powder of cBN particles.

[0069] Specifically, the method for manufacturing a cBN sintered body according to the present embodiment preferably comprises: a process of preparing a binder raw material powder with a high Al content (first process); a process of obtaining coated cBN powder by coating a metal on the surface of the cBN raw material powder (second process); a process of preparing a mixed powder consisting of 70 volume% or more and less than 100 volume% of cBN powder and the remainder of the binder raw material powder by mixing the binder raw material powder and the coated cBN powder (third process); and a process of obtaining a cBN sintered body by sintering the mixed powder (fourth process). Each process will be described in detail below.

[0070] Process 1

[0071] The first process is a process of preparing a binder raw material powder with a high proportion of Al. The binder raw material powder can be prepared by preparing it as follows. First, for example, WC powder, Co powder, and Al powder are prepared by manufacturing them using a conventionally known method or by obtaining them from the market. In addition, since the binder raw material powder may contain other elements in addition to WC, Co, and Al, it is preferable to prepare a powder containing at least one element selected from the group consisting of Cr, Ti, V, Zr, Nb, Hf, Ta, Re, Si, and Mo as the other element. Subsequently, the binder raw material powder can be prepared by mixing each of the above-described powders in a predetermined ratio and then grinding them using a wet ball mill, a wet bead mill, etc.

[0072] Regarding the Al content in the binder raw material powder, it is set to 20 to 40 mass%, and it is desirable to increase the amount of Al incorporated compared to conventional binders of this type. Accordingly, the diffusion of metals such as Al, which are coated on the surface of cBN in the second process described later, into the binder during sintering can be suppressed. The mixing method of each powder is not particularly limited, but from the perspective of mixing efficiently and homogeneously, it is preferable to use ball mill mixing, bead mill mixing, planetary mill mixing, or jet mill mixing. Each mixing method may be wet or dry.

[0073] Process 2

[0074] The second process is a process for obtaining coated cBN powder by coating the surface of the cBN raw material powder with metal. For the cBN raw material powder, commercially available cBN particles may be used, or cBN powder obtained from B and N by a conventionally known ultra-high pressure synthesis method may be used. Here, it is preferable to perform heat treatment on the cBN raw material powder as a pretreatment before coating the surface of the cBN raw material powder with metal. Specifically, for the purpose of purification, a reduction treatment is performed on the cBN raw material powder by heating it under a nitrogen atmosphere with a low oxygen partial pressure. At this time, the heat treatment temperature is preferably 900 to 1600°C. The heat treatment time is not particularly limited as long as it is continued until the surface of the cBN raw material powder is sufficiently purified, and for example, it can be 1 to 20 hours. The oxygen partial pressure during the reduction treatment is 1 × 10⁻⁶. -29 It is desirable to use a low oxygen partial pressure of atm or lower. By heat treatment under such a low oxygen partial pressure, the purification of the cBN raw material powder can be carried out sufficiently and efficiently. Accordingly, oxidation of the cBN surface, which is a factor that inhibits sintering, can be suppressed to expose the surface of the clean cBN particles, thereby improving the adhesion between the metal coating the surface of the cBN raw material powder and the cBN particles.

[0075] Next, in the second process, a metal such as Al is coated on the surface of the cBN raw material powder by using an arc plasma powder method (APD method). A coated cBN powder can be obtained by the above. By using the APD method, unlike coating methods such as the generally known sputtering method, AIP method, and CVD method, nanoparticles can be deposited on the surface of the cBN raw material powder, thereby allowing the metal to be present on the surface of the cBN raw material powder with a large surface area. In such coated cBN powder, the bonding reaction between the cBN particles and the metal is easily promoted during sintering, and the metal film becomes difficult to peel off in the third process described later. For this reason, the metal such as Al can be localized between adjacent cBN particles, making it possible to manufacture a cBN sintered body with enhanced bonding strength between cBN particles. Al is preferred as the metal to coat the surface of the cBN raw material powder. Accordingly, it is easy to selectively position Al between the cBN particles. In addition, in the second process, it is also desirable to coat the cBN raw material powder with at least one element (first element) selected from the group consisting of Cr, Ti, V, Co, Zr, W, Nb, Hf, Ta, Re, Si, and Mo by using the same coating method. That is, it is desirable to coat the cBN raw material powder with one first element selected from the above group, or it is desirable to coat the cBN raw material powder with two or more first elements. The value of the ratio M1 / (M+M1) can be controlled by adjusting the coating amount of Al and the first element.

[0076] Process 3

[0077] The third process is a process for preparing a mixed powder consisting of 70 volume% or more and less than 100 volume% of cBN powder and the remainder of the binder raw material powder by mixing the binder raw material powder and the coated cBN powder. Specifically, in the third process, it is preferable to prepare the mixed powder by performing wet ball mill mixing using ethanol, acetone, etc., as a solvent with respect to the binder raw material powder and the coated cBN powder. After preparing the mixed powder, the solvent is removed by natural drying. In addition, it is preferable to perform heat treatment (e.g., at 850°C or higher under vacuum) on the mixed powder, as this can remove impurities such as moisture adsorbed on the surface.

[0078] Process 4

[0079] The fourth process is a process for obtaining a cBN sintered body by sintering the above-mentioned mixed powder. In this process, a cBN sintered body is manufactured by sintering the above-mentioned mixed powder under high temperature and high pressure conditions. Specifically, in the fourth process, the vacuum-sealed above-mentioned mixed powder is sintered using an ultra-high temperature and high pressure device. The temperature condition for sintering is preferably 1500°C or higher and less than 2000°C, and more preferably 1600°C to 1900°C. The holding time is preferably 10 to 50 minutes. The sintering pressure condition is not particularly limited, but is preferably 5.5 to 8 GPa. A cBN sintered body can be manufactured by the above.

[0080] <Effects of Action>

[0081] The method for manufacturing a cBN sintered body according to the present embodiment can manufacture a cBN sintered body capable of long lifespan by undergoing each of the above-described processes.

[0082] Examples

[0083] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited thereto.

[0084] [Preparation of Samples]

[0085] cBN sintered bodies of samples 1 to 36 were prepared according to the following procedure.

[0086] <Sample 1>

[0087] (Process 1)

[0088] First, commercially available WC powder, Co powder, and Al powder were prepared. Next, each of the aforementioned powders was mixed in a mass ratio of WC:Co:Al of 32:38:30. At this time, the average particle size of each powder was 5 μm. In addition, the powder mixed in the above mass ratio was ground using a bead mill to prepare the binder raw material powder.

[0089] (Process 2)

[0090] First, commercially available cBN powder (average particle size 2 μm) was prepared as the cBN raw material powder. Heat treatment was performed on the above cBN raw material powder. The heat treatment was 1×10 -29 The process was carried out under ultra-low oxygen conditions of atm or less, at a heat treatment temperature of 1200℃, and a heat treatment time of 10 hours.

[0091] Next, regarding the cBN raw material powder subjected to the heat treatment described above, coated cBN powder was obtained by coating the surface of the cBN raw material powder with Al using the APD method under the following coating conditions.

[0092] <Coverage Conditions>

[0093] Coating device: Nanoparticle forming device ("APD-P", manufactured by Advance Rico Co., Ltd.)

[0094] Target: Use 2 units of pure Al (99.999% purity).

[0095] Introductory Gas: 10 -4 After depressurizing the vacuum to Pa, introduce argon gas to increase the pressure inside the device to 10 -1 Set to Pa

[0096] Discharge voltage: 150 V

[0097] Discharge frequency: 5 Hz

[0098] Capacitor capacitance: 1080 μF

[0099] Shot count: 10000

[0100] Processed powder amount: 25 g

[0101] Powder container rotation speed: 50 rpm.

[0102] (Process 3)

[0103] The above-mentioned coated cBN powder and the above-mentioned binder raw material powder were mixed in a volume ratio of 60:40, and uniformly mixed by a wet ball milling method using ethanol. Afterwards, the solvent was removed by natural drying, and the above-mentioned mixed powder was heat-treated under a vacuum at 900°C. By the above, a mixed powder was prepared.

[0104] (Process 4)

[0105] A cBN sintered body was prepared by sintering the above-mentioned mixed powder. Specifically, the above-mentioned mixed powder was filled into a Ta (tantalum) container and vacuum-sealed. Subsequently, this was sintered for 15 minutes under conditions of 6.5 GPa and 1700°C using a belt-type ultra-high pressure high temperature generator. The cBN sintered body of Sample 1 was prepared by the above.

[0106] <Sample 2>

[0107] In the third process, the cBN sintered body of Sample 2 was produced in the same manner as Sample 1, except that the volume ratio of the coated cBN powder to the binder raw material powder was mixed to be 70:30.

[0108] <Sample 3>

[0109] In the third process, the cBN powder to binder raw material powder was mixed in a volume ratio of 75:25, and in the second process, the heat treatment temperature for the cBN raw material powder was set to 1000°C, the heat treatment time to 12 hours, and the number of shots for the coating conditions was set to 5000, except that the cBN sintered body of Sample 3 was produced in the same manner as Sample 1.

[0110] <Sample 4>

[0111] In the third process, the cBN sintered body of Sample 4 was prepared in the same manner as Sample 1, except that the volume ratio of the coated cBN powder to the binder raw material powder was mixed to be 80:20.

[0112] <Sample 5>

[0113] In the third process, the cBN sintered body of Sample 5 was prepared in the same manner as Sample 1, except that the volume ratio of the coated cBN powder to the binder raw material powder was 89:11.

[0114] <Sample 6>

[0115] In the third process, the cBN sintered body of Sample 6 was prepared in the same manner as Sample 1, except that the volume ratio of the coated cBN powder to the binder raw material powder was mixed to be 95:5.

[0116] Sample 7

[0117] In the third process, the cBN sintered body of Sample 7 was prepared in the same manner as Sample 1, except that the volume ratio of the coated cBN powder to the binder raw material powder was mixed to be 99:1.

[0118] <Sample 8>

[0119] With respect to the commercially available cBN powder prepared as the cBN raw material powder in Sample 1, 1×10 -29Heat treatment was performed under conditions of atm or less, 1200℃, and 10 hours. The cBN raw powder subjected to this heat treatment was filled into a Ta (tantalum) container and vacuum-sealed, and then sintered for 15 minutes under conditions of 6.5 GPa and 1700℃ using a belt-type ultra-high pressure high temperature generator. Through the above, the cBN sintered body of Sample 8 was prepared.

[0120] <Sample 9>

[0121] In the second process, the cBN sintered body of Sample 9 was prepared in the same manner as Sample 2, except that heat treatment and Al coating were not applied to the cBN raw powder.

[0122] <Sample 10>

[0123] In the second process, a cBN sintered body of sample 10 was prepared in the same manner as sample 5, except that an Al coating was not applied to the surface of the heat-treated cBN raw powder.

[0124] <Sample 11>

[0125] In the second process, the heat treatment conditions for the commercially available cBN powder prepared as the cBN raw material powder were set to 1400°C and 20 hours, and Al was coated on the surface of the heat-treated cBN raw material powder with a coating condition of 1000 shots, except that the cBN sintered body of Sample 11 was produced in the same manner as Sample 6.

[0126] <Sample 12>

[0127] In the second process, the commercially available cBN powder prepared as the cBN raw material powder was heat-treated at 1200°C and for 10 hours, and Al was coated on the surface of the heat-treated cBN raw material powder with a coating condition of 5000 shots, except that the cBN sintered body of Sample 12 was produced in the same manner as Sample 5.

[0128] <Sample 13>

[0129] In the second process, a cBN sintered body of Sample 13 was prepared in the same manner as Sample 12, except that Al was coated on the surface of the heat-treated cBN raw powder with a coating condition of 25,000 shots.

[0130] <Sample 14>

[0131] In the second process, the commercially available cBN powder prepared as the cBN raw material powder was heat-treated at 1400°C for 20 hours, and Al was coated on the surface of the heat-treated cBN raw material powder with a coating condition of 50000 shots, except that the cBN sintered body of Sample 14 was produced in the same manner as Sample 5.

[0132] <Sample 15>

[0133] In the second process, the heat treatment conditions for the commercially available cBN powder prepared as the cBN raw material powder were set to 1200°C and 6 hours, and Al was coated on the surface of the heat-treated cBN raw material powder with a coating condition of 20000 shots, except that the cBN sintered body of Sample 15 was produced in the same manner as Sample 5.

[0134] <Sample 16>

[0135] In the second process, a cBN sintered body of sample 16 was prepared in the same manner as sample 15, except that Al was coated on the surface of the heat-treated cBN raw powder with a coating condition of 35,000 shots.

[0136] <Sample 17>

[0137] In the second process, a cBN sintered body of sample 17 was prepared in the same manner as sample 15, except that Al was coated on the surface of the heat-treated cBN raw powder with a coating condition of 50,000 shots.

[0138] <Sample 18>

[0139] In the second process, the commercially available cBN powder prepared as the cBN raw material powder was heat-treated at 1100°C for 9 hours, and Al was coated on the surface of the heat-treated cBN raw material powder with a coating condition of 80000 shots, except that the cBN sintered body of sample 18 was produced in the same manner as sample 5.

[0140] <Sample 19>

[0141] In the second process, regarding the coating conditions for coating the surface of the heat-treated cBN raw powder with metal, one of the two targets was changed to Cr (purity 99.999%), and the shot ratio (Al:Cr) of the two targets was changed to 499:1 (number of shots 5000), thereby coating the surface of the cBN raw powder with metal, except that the cBN sintered body of Sample 19 was produced in the same manner as Sample 5.

[0142] <Sample 20>

[0143] In the second process, the cBN sintered body of Sample 20 was produced in the same manner as Sample 19, except that the shot ratio (Al:Cr) of the two targets was changed to 99:1 (the number of shots was 5000) to coat the surface of the cBN raw powder with metal.

[0144] <Sample 21>

[0145] In the second process, the cBN sintered body of Sample 21 was produced in the same manner as Sample 19, except that the shot ratio (Al:Cr) of the two targets was changed to 9:1 (the number of shots was 5000) to coat the surface of the cBN raw powder with metal.

[0146] <Sample 22>

[0147] In the second process, the cBN sintered body of Sample 22 was produced in the same manner as Sample 19, except that the shot ratio (Al:Cr) of the two targets was changed to 7:3 (the number of shots was 5000) to coat the surface of the cBN raw powder with metal.

[0148] <Sample 23>

[0149] In the second process, the cBN sintered body of Sample 23 was produced in the same manner as Sample 19, except that the shot ratio (Al:Cr) of the two targets was changed to 6:4 (the number of shots was 5000) to coat the surface of the cBN raw powder with metal.

[0150] <Sample 24>

[0151] In the second process, the cBN sintered body of Sample 24 was produced in the same manner as Sample 19, except that the shot ratio (Al:Cr) of the two targets was changed to 5:5 (the number of shots was 5000) to coat the surface of the cBN raw powder with metal.

[0152] <Sample 25>

[0153] In the second process, the cBN sintered body of Sample 25 was produced in the same manner as Sample 19, except that the shot ratio (Al:Cr) of the two targets was changed to 4:6 (the number of shots was 5000) to coat the surface of the cBN raw powder with metal.

[0154] <Sample 26>

[0155] In the second process, regarding the coating conditions for coating a metal on the surface of the heat-treated cBN raw powder, cBN sintered body of sample 26 was produced in the same manner as sample 21, except that one of the two targets was changed from Cr to V (purity 99.999%).

[0156] <Sample 27>

[0157] In the second process, regarding the coating conditions for coating a metal on the surface of the heat-treated cBN raw powder, cBN sintered body of sample 27 was produced in the same manner as sample 21, except that one of the two targets was changed from Cr to Co (purity 99.999%).

[0158] <Sample 28>

[0159] In the second process, regarding the coating conditions for coating a metal on the surface of the heat-treated cBN raw powder, cBN sintered body of sample 28 was produced in the same manner as sample 21, except that one of the two targets was changed from Cr to Zr (purity 99.999%).

[0160] <Sample 29>

[0161] In the second process, regarding the coating conditions for coating a metal on the surface of the heat-treated cBN raw powder, cBN sintered body of sample 29 was produced in the same manner as sample 21, except that one of the two targets was changed from Cr to W (purity 99.999%).

[0162] <Sample 30>

[0163] In the second process, regarding the coating conditions for coating a metal on the surface of the heat-treated cBN raw powder, cBN sintered body of sample 30 was produced in the same manner as sample 21, except that one of the two targets was changed from Cr to Nb (purity 99.999%).

[0164] Sample 31

[0165] In the second process, regarding the coating conditions for coating a metal on the surface of the heat-treated cBN raw powder, cBN sintered body of sample 31 was produced in the same manner as sample 21, except that one of the two targets was changed from Cr to Hf (purity 99.999%).

[0166] <Sample 32>

[0167] In the second process, regarding the coating conditions for coating a metal on the surface of the heat-treated cBN raw powder, cBN sintered body of sample 32 was produced in the same manner as sample 21, except that one of the two targets was changed from Cr to Ta (purity 99.999%).

[0168] Sample 33

[0169] In the second process, regarding the coating conditions for coating a metal on the surface of the heat-treated cBN raw powder, cBN sintered body of sample 33 was produced in the same manner as sample 21, except that one of the two targets was changed from Cr to Re (purity 99.999%).

[0170] <Sample 34>

[0171] In the second process, regarding the coating conditions for coating a metal on the surface of the heat-treated cBN raw powder, cBN sintered body of sample 34 was prepared in the same manner as sample 21, except that one of the two targets was changed from Cr to Si (purity 99.999%).

[0172] <Sample 35>

[0173] In the second process, regarding the coating conditions for coating a metal on the surface of the heat-treated cBN raw powder, cBN sintered body of sample 35 was prepared in the same manner as sample 21, except that one of the two targets was changed from Cr to Mo (purity 99.999%).

[0174] <Sample 36>

[0175] In the second process, regarding the coating conditions for coating a metal on the surface of the heat-treated cBN raw powder, cBN sintered body of sample 36 was prepared in the same manner as sample 21, except that one of the two targets was changed from Cr to Ti (purity 99.999%).

[0176] 〔evaluation〕

[0177] <Measurement of inter-particle distance (D), atomic percentage of Al and ratio M1 / (M+M1), and determination of the presence or absence of the first region>

[0178] For each cBN sintered body of Samples 1 to 18, a smooth surface was produced by cutting at an arbitrary location and polishing the exposed surface. Subsequently, sections were prepared by thinning to a thickness of 50 nm using an argon ion slicer. Then, elemental line analysis was performed on a second image (100 nm × 100 nm) using TEM-EDX according to the method described above. The beam diameter of the TEM-EDX was set to 0.2 nm, and the scan interval was set to 0.6 nm. From the obtained measurements, the inter-particle distance (D) and the atomic percentage of Al were calculated according to the method described above, and the presence or absence of a first region was determined. Specifically, the determination of the presence or absence of a first region was made by observing 10 arbitrary second images of Samples 1 to 18; if 6 or more first regions were observed, it was classified as "first region present," and if 5 or fewer were observed, it was classified as "first region absent." In addition, for samples having a “first region,” the average value of the distance between particles (D) obtained from elemental line analysis targeting the six or more first regions specified as the first region was calculated. In addition, the atomic percentage of Al was calculated from the average value of the maximum peaks of Al obtained from the elemental line analysis. The results are shown in Table 1. Samples 2 to 7 and samples 11 to 18 are examples, and samples 1 and samples 8 to 10 are comparative examples.

[0179] In addition, since sample 8 did not have a binder, a measurable first region could not be detected. For sample 9, in the elemental line analysis performed on the region where the interfacial shape structure of randomly extracted cBN particles was formed, the distance (D) between all particles exceeded 10 nm.

[0180] In addition, for each cBN sintered body of samples 19 to 36, a second image (100 nm × 100 nm) was obtained in the same manner as for each cBN sintered body of samples 1 to 18, and elemental line analysis was performed on this second image using TEM-EDX. From the obtained measurements, the inter-particle distance (D), atomic % of Al, and ratio M1 / (M+M1) were determined according to the method described above, and the presence or absence of the first region was also determined. The results are shown in Table 2. Samples 19 to 36 are all examples. In addition, in Table 2, the results for samples 5 and 10 are also specified to show the results of the cutting test described later.

[0181] <1st Cutting Test>

[0182] A cutting tool (substrate shape: SNGN090308, blade treatment T 01225) for each sample was manufactured from each cBN sintered body of Samples 1 to 18 above. Using this, a cutting test (first cutting test) was performed under the following cutting conditions.

[0183] <Cutting Conditions>

[0184] Cutting speed: 1500 m / min.

[0185] Feed rate: 0.2 mm / rev.

[0186] Insertion depth: 0.8 mm

[0187] Coolant: WET

[0188] Coolant: Emulsion 96 (diluted 20 times with water)

[0189] Cutter: RM3080R (Manufactured by Sumitomo Electric Vehicle Co., Ltd.)

[0190] Cutting method: Intermittent cutting

[0191] Lathe: NEXUS 530-II HS (Manufactured by Yamazaki Corporation)

[0192] Workpiece: FC250.

[0193] The blade was observed at every 0.5 km of cutting distance, and the amount of blade detachment was measured. The amount of blade detachment was defined as the width of retraction due to wear from the blade ridge position prior to cutting. In the case of chipping, the size of the chipping was defined as the amount of detachment. The cutting distance at which the amount of blade detachment became 0.1 mm or more was measured. Furthermore, the above cutting distance was defined as the life of the cutting tool. The results are shown in Table 1. It can be evaluated that the longer the cutting distance, the longer the life of the cutting tool.

[0194] <2nd Cutting Test>

[0195] A cutting tool (substrate shape: TNGA160404, blade processing T01225) for each sample was fabricated from each cBN sintered body of the above samples 5 and 10, and samples 19 to 36. Using this, a cutting test (second cutting test) was performed under the following cutting conditions.

[0196] <Cutting Conditions>

[0197] Cutting speed: 250 m / min.

[0198] Feed rate: 0.15 mm / rev.

[0199] Cut: 0.1 mm

[0200] Coolant: DRY

[0201] Cutting method: Continuous cutting

[0202] Lathe: LB400 (Manufactured by Okuma Kabushiki Kaisha)

[0203] Workpiece: Sintered part (Quenched Sintered Alloy D40 manufactured by Sumitomo Electric Company, Hardness of quenched cutting section: HRB75).

[0204] The blade was observed at every 0.3 km of cutting distance to measure the amount of blade wear. The cutting distance at which the amount of blade wear exceeded 100 μm was measured. In addition, the above cutting distance was defined as the lifespan of the cutting tool. The results are shown in Table 2. It can be evaluated that the longer the cutting distance, the longer the lifespan of the cutting tool.

[0205]

[0206]

[0207] [Consideration]

[0208] According to Table 1, it can be understood that the cutting tools obtained from each of the cBN sintered bodies of Samples 2 to 7 and Samples 11 to 18, which are examples, have a longer lifespan compared to the cutting tools obtained from the cBN sintered bodies of Sample 1 and Samples 8 to 10, which are comparative examples.

[0209] According to Table 2, it can be understood that the cutting tool obtained from each of the cBN sintered bodies of Sample 5 and Samples 19 to 36, which are examples, has a longer lifespan compared to the cutting tool obtained from the cBN sintered body of Sample 10, which is a comparative example.

[0210] Although the embodiments and examples of the present disclosure have been described above, it is also intended from the outset to appropriately combine the configurations of each of the above-described embodiments and examples.

[0211] The embodiments and examples disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the invention is defined by the claims, not by the embodiments and examples described above, and is intended to include all modifications within the meaning and scope equivalent to the claims.

Claims

Claim 1 A cubic boron nitride sintered body comprising 70 volume% or more and less than 100 volume% of cubic boron nitride particles and a binder, wherein the binder comprises an aluminum compound and also comprises cobalt as a constituent element, and the cubic boron nitride sintered body comprises a first region in which the spacing between adjacent cubic boron nitride particles is 0.1 nm or more and 10 nm or less, and when the first region is analyzed using an energy-dispersive X-ray analysis device equipped with a transmission electron microscope, the atomic percentage of aluminum in the first region is 0.1 or more, and the first region is a cubic boron nitride sintered body in which at least 6 regions are observed from 10 images of size 100 nm × 100 nm taken at a magnification of 2 million times, in which an interface-shaped structure between adjacent cubic boron nitride particles is formed. Claim 2 A cubic boron nitride sintered body according to claim 1, wherein the spacing between adjacent cubic boron nitride particles in the first region is 0.1 nm or more and 7.0 nm or less, and the atomic % of aluminum in the first region is 0.5 or more. Claim 3 A cubic boron nitride sintered body according to claim 1 or 2, wherein the first region comprises aluminum and at least one first element selected from the group consisting of chromium, titanium, vanadium, cobalt, zirconium, tungsten, niobium, hafnium, tantalum, rhenium, silicon, and molybdenum as constituent elements, and when the first region is analyzed using an energy-dispersive X-ray analysis device equipped with a transmission electron microscope, the ratio M1 / (M+M1) is 0.50 or less, where M is the atomic percentage of the aluminum and M1 is the atomic percentage of the element present at the highest concentration among the first elements. Claim 4 A cubic boron nitride sintered body according to claim 3, wherein the ratio M1 / (M+M1) is 0.010 or more and 0.30 or less. Claim 5 A cubic boron nitride sintered body according to claim 1 or 2, wherein the cubic boron nitride sintered body comprises 80 volume% or more and 95 volume% or less of the cubic boron nitride particles. Claim 6 A cutting tool comprising a cubic boron nitride sintered body as described in claim 1 or 2.

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