cBN sintered body

Abstract

Sintered cBN comprising cubic boron nitride particles and a binder phase, the sintered cBN being characterized in that: the binder phase contains a Ti-Al alloy having at least one element selected from Si, Mg and Zn and also contains Ti2CN and TiB2; when a peak intensity of Ti2CN which appears at 2θ of 41.9° to 42.2° in XRD is defined as ITi2CN and a peak intensity of the Ti-Al alloy which appears at the 2θ of 39.0° to 39.3° is defined as ITi-Al, an ITi2CN / ITi-Al value is 2.0 to 30.0 inclusive; and the average aspect ratio of regions in which Ti element and B element are overlapped each other in an element mapping image of Ti and B which is obtained by AES is 1.7 to 6.5 inclusive and the area ratio of the region is 0.025 to 0.120% inclusive.

Description

[Technical Field]

[0001] The present invention relates to a rigid composite material, a cubic boron nitride sintered body (hereinafter sometimes referred to as cBN). This application claims priority based on Japanese Patent Application No. 2021-14845, filed on February 2, 2021. All contents contained in said Japanese Patent Application are incorporated herein by reference. [Background technology]

[0002] Although cBN sintered bodies are less hard than diamonds, they are used as cutting tools due to their low reactivity with Fe-based and Ni-based materials, and also as drilling tips for drilling tools.

[0003] Here, drilling tools are tools used to dig and bore into the ground or bedrock. On the other hand, underground rocks are not uniform in composition or strength and are brittle materials. Therefore, unlike cutting processes that prioritize cutting and scraping performance, drilling tools need to withstand the impact and vibration required to break the rock, and furthermore, they need to withstand the rotation required to efficiently remove the broken rock. Under these circumstances, proposals have been made to improve the cutting and drilling performance of cemented carbide and cBN sintered bodies.

[0004] For example, Patent Document 1 describes a cBN sintered body having a bonded phase in which 45 to 75 volume percent of cubic boron nitride particles with an average particle size of 0.5 to 3.5 μm and Ti boride particles with an average particle size of 50 to 500 nm are dispersed, and the relationship between the volume percent of the cubic boron nitride particles (X) and the volume percent of the Ti boride generated (Y) satisfies (-0.05x + 4.5) ≤ Y ≤ (-0.2x + 18), and the proportion of the Ti boride not in contact with the cubic boron nitride particles is 15 to 65 volume percent of all the Ti boride, and this cBN sintered body is said to have excellent toughness and, when used as a cutting tool, excellent fracture resistance and wear resistance.

[0005] Furthermore, for example, Patent Document 2 describes a cBN sintered body in which 25 to 90% by volume of cubic boron nitride and / or wurtzite-type boron nitride is used as the hard phase, the remaining binder phase is mainly composed of ceramics, and the surface of the particles of the hard phase has a first layer consisting of at least one of Ti-containing boronitride, borocarbide, boronite, boronite oxide, boronite oxide, boronite carbide, boronite oxide, and boronite carbon oxide, and a second layer consisting of at least one of Al-containing boronitride, borocarbide, boronite, boronite oxide, boronite carbide, boronite oxide, and boronite carbon oxide is formed on the entire surface of the first layer, and this cBN sintered body is said to have excellent fracture resistance.

[0006] Furthermore, for example, Patent Document 3 describes a self-sintered polycrystalline cubic boron nitride compact having a first phase of cBN particles and a ceramic binder phase containing a titanium compound, wherein the first phase accounts for more than 80 volume percent of the compact, and furthermore, the compact contains a binder phase having conductivity or semiconductivity due to the use of Ti2AlC as a binder precursor, resulting in a high-content cBN sintered body with excellent machinability by electrical discharge machining, and the cBN sintered body is said to be suitable for cutting cast iron and cemented carbide. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 5804448 [Patent Document 2] Japanese Patent Application Publication No. 5-310474 [Patent Document 3] Special Publication No. 2013-537116 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] The present invention has been made in view of the above circumstances and proposals, and aims to provide a cBN sintered body, which is a hard composite material that has excellent fatigue wear resistance and abrasive wear resistance, and furthermore, when used as an excavation tool, has resistance to damage factors such as chipping caused by impact and vibration for breaking rock. [Means for solving the problem]

[0009] The cBN sintered body according to an embodiment of the present invention is 1) Having a bonding phase with cubic boron nitride particles, 2) The cubic boron nitride has an average particle size of 0.5 to 30.0 μm and a content of 65.0 to 93.0 vol%, 3 The bonding phase includes Ti2CN and TiB2 in addition to a Ti-Al alloy having one or more of Si, Mg, and Zn. 4 )The peak intensity of Ti2CN that appears in XRD when 2θ is between 41.9° and 42.2° is I Ti2CN Assuming that the peak intensity of the Ti-Al alloy where 2θ appears between 39.0° and 39.3° is I Ti-Al When that happens, I Ti2CN / I Ti-Al The value is between 2.0 and 30.0. 5 ) In the elemental mapping image of Ti and B obtained by Auger electron spectroscopy, the areas where the Ti element and the B element overlap. When approximated as an ellipse, the portion of the circle with a circularity of 1 is excluded from the extracted area. The average aspect ratio of is 1.7 or more and 6.5 or less, and the aforementioned part The sum of the areas excluding the perfectly circular portion with a roundness of 1. The area ratio is between 0.025% and 0.120%. [Effects of the Invention]

[0010] The aforementioned cBN sintered body exhibits excellent fatigue wear resistance and abrasive wear resistance, and furthermore, even when used as a drilling tool, it has resistance to damage factors such as chipping caused by impact and vibration used to break up rock. [Brief explanation of the drawing]

[0011] [Figure 1]This is a diagram schematically showing the overlapping region of Ti element and B element based on the elemental mapping by Auger electron spectroscopy in Example 14. [Figure 2] This is a diagram in which the overlapping region in Fig. 1 is approximated by an ellipse.

Mode for Carrying Out the Invention

[0012] The present inventor has intensively studied to obtain a cBN sintered body that is excellent in fatigue wear resistance and abrasive wear resistance and has resistance to damage factors such as defects caused by impact and vibration for rock breaking even when used as an excavation tool.

[0013] As a result, there is a predetermined relationship between the XRD peaks of Ti2CN and Ti-Al alloy contained in the bonding phase, and the area ratio of the overlapping region of Ti element and B element in the bonding phase is within a predetermined range, and when the average aspect ratio of the said region is within a predetermined range, it has been found that it is excellent in fatigue wear resistance and abrasive wear resistance, and further has resistance to damage factors such as defects caused by impact and vibration for rock breaking even when used as an excavation tool.

[0014] Hereinafter, the cBN sintered body according to the embodiment of the present invention will be described in detail mainly focusing on the case where it is applied to an excavation tool. In the description of this specification and the claims, when a numerical range is expressed as "A to B", "A~B" (both A and B are numerical values), it is synonymous with "not less than A and not more than B", and the range includes the upper limit value (B) and the lower limit value (A). Also, when only the upper limit value (B) has a unit described, the units of the upper limit value (B) and the lower limit value (A) are the same.

[0015] 1. Cubic boron nitride (cBN) particles The average particle size of the cBN particles and the content of the cBN particles in the cBN sintered body will be described.

[0016] (1) Average particle size The average particle size of the cBN particles used in this embodiment is not particularly limited, but it is more preferable that it is in the range of 0.5 μm or more and 30.0 μm or less.

[0017] The reason for this is that, in addition to the increased fracture resistance due to the inclusion of cBN particles within the sintered body, if the average particle size is between 0.5 μm and 30.0 μm, even when used as a drilling tool, it more reliably suppresses chipping and fractures originating from the uneven cutting edge shape caused by the detachment of cBN particles from the tool surface. Furthermore, it reliably suppresses the propagation of cracks that develop from the interface between the cBN particles and the binding phase, or cracks that develop from the fracture of the cBN particles themselves, resulting in even greater fracture resistance.

[0018] Here, the average particle size of the cBN particles can be determined as follows. The cross-section of the cBN sintered body is polished to a mirror finish, and the polished surface is observed using a scanning electron microscope (SEM) to obtain a secondary electron image. Next, the portion containing the cBN particles in the obtained image is extracted using image processing, and the average particle size is calculated based on the maximum length of each particle obtained from the image analysis, as described later.

[0019] Here, in order to extract the cBN particle portion from the image using image processing, the image is displayed in a 256-level monochrome with 0 being black and 255 being white, in order to clearly distinguish between the cBN particle portion and the bonded phase. A binarization process is then performed using a threshold value calculated as (wv) / 2+v for the peak pixel value (v) of the cBN particle portion and the peak pixel value (w) of the bonded phase portion.

[0020] For determining the pixel values ​​of the cBN particle portion, it is preferable to select a region of approximately 0.5 μm × 0.5 μm, for example, and use the average value obtained from at least three different locations within the same image region as the aforementioned pixel value of the cBN particle. Similarly, for determining the pixel values ​​of the binding phase portion, it is preferable to select a region of approximately 0.2 μm × 0.2 μm to 0.5 μm × 0.5 μm, and use the average value obtained from at least three different locations within the same image region as the peak value of the aforementioned pixel value of the binding phase.

[0021] Furthermore, after binarization, a process is used to separate the parts where cBN particles are thought to be in contact with each other, such as using watershed image processing to separate cBN particles that appear to be in contact.

[0022] After the binarization process described above, the parts of the image corresponding to cBN particles (the black areas) are subjected to particle analysis, and the maximum length of each cBN particle is determined and taken as the diameter of each cBN particle. For the particle analysis to determine the maximum length, the larger of the two lengths obtained by calculating the Ferret diameter for each cBN particle is taken as the maximum length, and this value is taken as the diameter of each cBN particle.

[0023] Assuming each cBN particle is an ideal sphere with this diameter, the volume calculated is used as the volume of each particle to determine the cumulative volume. Based on this cumulative volume, a graph is plotted with the volume percentage (%) on the vertical axis and the diameter (μm) on the horizontal axis. The diameter when the volume percentage is 50% is taken as the average particle size of the cBN particles. This is done for three observation regions, and the average value is taken as the average particle size of the cBN particles (μm, this average particle size is called D50).

[0024] When performing this particle analysis, the length per pixel (μm) is set using a scale value known in advance by SEM. As the observation area, an area in which at least 30 cBN particles can be observed is preferred; that is, if the average particle size of the cBN particles is about 3 μm, an observation area of ​​about 15 μm × 15 μm is preferred.

[0025] (2)Content The content (vol%) of cBN particles in the cBN sintered body is not particularly limited, but is preferably 65.0 vol% or more and 93.0 vol% or less.

[0026] The reason for this is that if the cBN content is less than 65.0 vol%, there are fewer hard materials (cBN particles) in the cBN sintered body, which can reduce fracture resistance when used as a drilling tool, for example. On the other hand, if the content exceeds 93.0 vol%, voids that can become crack initiation points are formed in the cBN sintered body, which can reduce fracture resistance.

[0027] The cBN particle content in a cBN sintered body can be determined as follows: The cross-sectional structure of the cBN sintered body is observed using a scanning electron microscope (SEM), the portion containing cBN particles is extracted from the resulting secondary electron image using image processing, and the area occupied by cBN particles is calculated through image analysis. This process is performed for at least three observation areas, and the average of the calculated area values ​​is taken as the cBN particle content (vol%). For this image processing, an observation area of ​​approximately 15 μm × 15 μm is desirable, where at least 30 cBN particles are observed within the area, i.e., when the average particle size of the cBN particles is 3 μm.

[0028] 2. Bonded phase The bonding phase preferably includes Ti2CN and TiB2 in addition to a Ti-Al alloy having one or more of Si, Mg, and Zn. Here, "one or more of Si, Mg, and Zn" means one of Si, Mg, or Zn, or two of Si, Mg, or Zn, or all three of Si, Mg, and Zn.

[0029] When the XRD peak intensities of the Ti2CN and Ti-Al alloy contained in the binder phase have a predetermined relationship, that is, In XRD, the peak intensity of Ti2CN appearing when 2θ is between 41.9° and 42.2° is I Ti2CN Assuming that the peak intensity of the Ti-Al alloy where 2θ appears between 39.0° and 39.3° is I TiAlWhen it is set as such, the ratio of peak intensities, I Ti2CN / I TiAl is preferably 2.0 or more and 30.0 or less. When the ratio of peak intensities is within this range, the cBN sintered body is excellent in wear resistance and abrasive wear resistance, and for example, it becomes a cBN sintered body with high resistance to damage factors such as defects due to impact and vibration during rock excavation.

[0030] The reason is that when I Ti2CN / I TiAl is less than 2.0, due to the excessive presence of Ti-Al alloy in the cBN sintered body, the cBN particles react with this TiAl to form coarse TiB2, and excessive AlN is generated. Therefore, this TiB2 and AlN become the starting points of fracture during rock excavation and the like. On the other hand, when I Ti2CN / I TiAl is greater than 30.0, it is considered that the Ti-Al alloy in the cBN sintered body decreases, resulting in a decrease in the adhesion force between the cBN particles and the bonding phase and a decrease in the toughness of the cBN sintered body.

[0031] Here, the peak intensity (I Ti2CN ) of Ti2CN and the peak intensity (I TiAl ) of the Ti-Al alloy are determined by XRD measurement using CuKα radiation. With the peak of the 111 diffraction line of cBN set as 2θ = 43.3, based on this peak position (angle), the peak between 2θ of 41.9° and 42.2° is regarded as Ti2CN, and the peak between 2θ of 39.0° and 39.3° is regarded as the Ti-Al alloy. After background noise removal, peak search is performed and confirmed respectively.

[0032] Also, in the elemental mapping images of Ti and B by Auger Electron Spectroscopy (hereinafter referred to as AES), there is a location where the Ti element and the B element overlap. It is preferable that the aspect ratio of this overlapping location is 1.7 or more and 6.5 or less, and the area ratio is 0.025% or more and 0.120% or less. As an example of this overlapping location, the observation result of the sintered body of Example 14 described later in FIG. 1 is shown.

[0033] Here, the aspect ratio is preferably such that, when the overlapping area shown in Figure 1 is approximated as an ellipse by image analysis as shown in Figure 2, the average aspect ratio (average value of the ratio of the longer side to the shorter side) of the area excluding the circular portion with a circularity of 1 extracted is between 1.7 and 6.5. The degree of roundness is calculated as 4π × (area) / (perimeter squared), and a circle is called a perfect circle when this value is 1.

[0034] Furthermore, the area ratio is the ratio of the sum of the areas of the parts of the AES observation area excluding the perfectly circular portion with a circularity of 1, and is preferably 0.025% or more and 0.120% or less.

[0035] The reason for setting the average aspect ratio within the aforementioned range is that if it is less than 1.7, the overlapping portion will not be able to sufficiently bend (refract) the cracks that have formed in the cBN sintered body, and the toughness of the cBN sintered body will not be sufficiently improved. On the other hand, if it exceeds 6.5, the cracks that have formed in the cBN sintered body will propagate within this portion, and similarly the toughness of the cBN sintered body will not be sufficiently improved.

[0036] The reason for setting the area ratio within the aforementioned range is that if the area ratio of the overlapping areas of Ti and B elements is less than 0.025%, even if the average aspect ratio is in the range of 1.7 to 6.5, the overlapping areas will not sufficiently bend (refract) the propagation of cracks generated in the cBN sintered body, and the toughness of the cBN sintered body will not be sufficiently improved. On the other hand, if it exceeds 0.120%, the probability of the overlapping areas bending the propagating cracks increases, but they are more likely to become the starting point for crack generation, i.e., the starting point for fatigue fracture.

[0037] To calculate the average aspect ratio and area ratio by image analysis, at least three locations within the sintered body are observed and the images are processed. The average of the obtained values ​​is used as the average aspect ratio and area ratio. For the observation area used in image processing, if the average particle size of the cBN particles is 3 μm, an observation area of ​​approximately 5.0 μm × 3.5 μm is desirable.

[0038] The above description includes the following features. (Note 1) A cBN sintered body having cubic boron nitride particles and a bonding phase, 1) The bonding phase includes Ti2CN and TiB2 in addition to a Ti-Al alloy having one or more of Si, Mg, and Zn. 2) The peak intensity of Ti2CN that appears in XRD when 2θ is between 41.9° and 42.2° is I Ti2CN Assuming that the peak intensity of the Ti-Al alloy where 2θ appears between 39.0° and 39.3° is I Ti-Al In that case, I Ti2CN / I Ti-Al The value is between 2.0 and 30.0. 3) In the elemental mapping image of Ti and B obtained by Auger electron spectroscopy, the average aspect ratio of the area where the Ti element and the B element overlap is 1.7 or more and 6.5 or less, and the area ratio of the said area is 0.025% or more and 0.120% or less. A cBN sintered body characterized by the following features. (Note 2) The cBN sintered body according to Appendix 1, characterized in that the average particle size of the cubic boron nitride particles is 0.5 μm or more and 30.0 μm or less. (Note 3) The cBN sintered body according to Appendix 1 or Appendix 2, characterized in that the average content of the cubic boron nitride particles is 65.0 vol% or more and 93.0 vol% or less. [Examples]

[0039] Next, examples will be described. However, the present invention is not limited in any way to examples applied to tools for cutting rock.

[0040] This example was manufactured by the following steps (1) to (3). Note that the raw material powder contained trace amounts of unavoidable impurities.

[0041] (1) Preparation of raw material powder As hard raw materials, cBN raw materials were prepared such that the average particle size after sintering ranged from 0.5 to 35.0 μm, as shown in Table 2. As raw material powders constituting the binder phase, Ti2AlC and Ti3AlC2 raw materials were prepared. Both the Ti2AlC and Ti3AlC2 raw materials had average particle sizes of 5 μm and 50 μm, respectively.

[0042] In addition, TiN powder (0.6), TiCN powder (0.6), TiC powder (0.6), TiAl3 powder (0.4), and SiO2 powder (0.02), ZnO powder (0.8), and MgO powder (0.8) were prepared separately as bonding phase forming raw material powders. The blending composition of these raw materials is shown in Table 1. Here, the number in parentheses after the name of each powder is the average particle size (D50), and the unit is μm.

[0043] (2) Mixing and preheating treatment Of these prepared powders, those not containing Si, Mg, or Zn were filled into a ball mill container lined with cemented carbide along with cemented carbide balls and acetone and mixed. The mixing time was 1 hour to avoid finely grinding the raw material powders. Although not performed in this example, it is more preferable to mix the raw material powders while breaking up any agglomeration using an ultrasonic stirring device.

[0044] Next, the mixed raw material powder was subjected to a preheat treatment under a vacuum atmosphere of 1 Pa or less at the temperatures indicated as "Heat treatment temperature after mixing" in Table 2, to evaporate the adsorbed water from the powder surface.

[0045] Here, the preheating temperature is preferably 250 to 900°C under a vacuum atmosphere of 1 Pa or less. The reason is that if the temperature is below 250°C, the adsorbed water does not evaporate sufficiently, and during ultra-high pressure high-temperature sintering, Ti2AlC and Ti3AlC2 react with the remaining moisture and decompose into TiO2 and Al2O3. On the other hand, if the temperature exceeds 900°C, Ti2AlC and Ti3AlC2 also react with oxygen during preheating and decompose into TiO2 and Al2O3, reducing the content of Ti2AlC and Ti3AlC2 in the bonding phase and lowering the toughness of the cBN sintered body.

[0046] Next, powders other than those containing Si, Mg, and Zn, which had undergone preheat treatment, and one or more of SiO2, ZnO, and MgO powders were filled into a ball mill container lined with cemented carbide along with cemented carbide balls and acetone and mixed. The mixing time was 1 hour to avoid finely grinding the raw material powders. Although not done in this example, it is more preferable to mix the raw material powders while breaking up any agglomeration using an ultrasonic stirring device.

[0047] (3) Molding and sintering Next, molded bodies are prepared from the obtained sintered raw material powder and placed in an ultra-high pressure, high-temperature sintering apparatus. By sintering at a pressure of 5 GPa and a temperature of 1600°C, the cBN sintered bodies of the present invention (referred to as example sintered bodies) 1 to 20 shown in Table 2 are produced. (However, numbers 3, 7, 8, 10, 14, 17, and 18 are missing.) A sample was prepared. The values ​​in Table 2 were measured using the method described above. Here, the average particle size and content of cBN particles were measured using an observation area in which at least 30 cBN particles were observed, while other observation areas were measured using the sizes exemplified.

[0048] For comparison, a comparative sintered body was prepared. As the raw material powders, cBN raw material was prepared as the hard raw material, such that the average particle size after sintering was 1.0 to 4.0 μm as shown in Table 4, and raw material powders containing Ti2AlC or Ti3AlC2 were prepared as the raw material powders constituting the binder phase. Here, the average particle size (D50) of the Ti2AlC and Ti3AlC2 raw materials was 5 μm and 50 μm, respectively (the other powders had the same average particle size as in the examples). These were mixed using a ball mill under the same conditions as in the examples, with the powders other than the SiO2 powder in the compositions shown in Tables 1 and 3. Subsequently, this was subjected to a preheat treatment at a predetermined temperature in the range of 100°C to 1200°C under a vacuum atmosphere of 1 Pa or less (indicated as "heat treatment temperature after mixing" in Table 4). Then, a molded body was prepared from the raw material powder obtained by mixing the amount of SiO2 powder with the compositions shown in Tables 1 and 3 under the same conditions as in the examples. This was then placed in an ultra-high pressure, high-temperature sintering apparatus and sintered at a pressure of 5 GPa and a temperature of 1600°C to produce comparative example cBN sintered bodies (referred to as comparative example sintered bodies) 1 to 8 shown in Table 4. The values ​​in Table 4 were obtained in the same manner as in the examples.

[0049] [Table 1]

[0050] In Table 1, "-" indicates that the substance is not contained, and "*" indicates that a portion of it was also used as a binding phase raw material for comparative examples.

[0051] [Table 2]

[0052] In Table 2, "*" indicates that the presence of Al2O3 was confirmed by an electron probe microanalyzer (EPMA).

[0053] [Table 3]

[0054] In Table 3, "-" indicates that the substance is not contained.

[0055] [Table 4]

[0056] In Table 4, "*1" indicates that no peak for TiAl3 was detected by XRD, and "*2" indicates that the presence of Al2O3 was confirmed by EPMA.

[0057] Next, the sintered body 1 of the present invention ~ 20 (however, numbers 3, 7, 8, 10, 14, 17, and 18 are missing) And from comparative sintered bodies 1 to 5, respectively, example tools 1 to 20 having the shape of ISO standard RNGN090300 were obtained. (However, numbers 3, 7, 8, 10, 14, 17, and 18 are missing.) (Examples 1-20) (However, numbers 3, 7, 8, 10, 14, 17, and 18 are missing.) ) and comparative tools 1 to 8 (referred to as comparative examples 1 to 8) were prepared, mounted on an NC lathe, and the following wet cutting tests were performed.

[0058] Cutting speed: 150m / min Depth of cut: 0.3mm Feed rate: 0.1 mm / rev Workpiece material: Granite (from Takine) Shape: Φ150mm x 200mmL Cutting fluid material: Water-soluble cutting fluid (NeoCool, manufactured by MORESCO Corporation) The amount of wear and condition of the cutting edge were checked when the cutting length (cutting distance) was 800m. However, the cutting edge was observed every 100m of cutting length, and the presence or absence of chipping and the amount of wear were measured. If the amount of wear exceeded 2000μm, the cutting test was stopped at that point. The results are shown in Table 5.

[0059] [Table 5]

[0060] In Table 5, "*" indicates the state when the cutting distance is 100m.

[0061] As is clear from Table 5, all of the examples exhibited excellent resistance to abrasive wear, with minimal wear and no chipping, and also possessed resistance to damage factors such as chipping caused by impact and vibration during rock breaking, even when used as drilling tools. In contrast, the comparative examples all showed chipping or high wear after only a short cutting length, exhibiting low resistance to abrasive wear and being prone to chipping, making them unsuitable for use as drilling tools.

[0062] The embodiments disclosed herein are illustrative in all respects and are not restrictive. The scope of the present invention is indicated by the claims rather than by the embodiments described herein, and all modifications within the scope are intended to be included in the meaning of equivalents of the claims.

Claims

1. A cBN sintered body having cubic boron nitride particles and a bonding phase, 1) The cubic boron nitride has an average particle size of 0.5 to 30.0 μm and a content of 65.0 to 93.0 vol%, 2) The bonding phase is a Ti-Al alloy having one or more of Si, Mg, and Zn, in addition to Ti ２ CN, TiB ２ Includes, 3) Ti appears in XRD when 2θ is between 41.9° and 42.2° ２ The peak intensity of CN is I Ｔｉ２ＣＮ The peak intensity of the Ti-Al alloy where the same 2θ appears between 39.0° and 39.3° is defined as I Ｔｉ－Ａｌ In that case, I Ｔｉ２ＣＮ / I Ｔｉ－Ａｌ The value is between 2.0 and 30.

0. 4) In the elemental mapping images of Ti and B obtained by Auger electron spectroscopy, When the overlapping region of Ti and B elements is approximated as an ellipse, the average aspect ratio of the region excluding the circular portion with a circularity of 1 is 1.7 or greater and 6.5 or less, and the area ratio of the sum of the areas of the region excluding the circular portion with a circularity of 1 is 0.025% or greater and 0.120% or less. A cBN sintered body characterized by the features described above.

Images