Cubic boron nitride sinter

Abstract

A cubic boron nitride sintered body, wherein the cubic boron nitride sintered body comprises cubic boron nitride particles, a binding phase, and voids, wherein the percentage of the cubic boron nitride particles relative to the total volume of the cubic boron nitride particles and the binding phase is 40% vol% or more and 70% vol% or less, the percentage of the binding phase relative to the total volume of the cubic boron nitride particles and the binding phase is 30% vol% or more and 60% vol% or less, the binding phase comprises alumina particles comprising 10% vol% or more and 100% vol% or less of the total volume of the binding phase, the alumina particles having an average particle size of 50 nm or more and 250 nm or less, and the cubic boron nitride sintered body comprises one or more first voids comprising 0.001% vol% or more and 0.100% vol%, at least a portion of each of the first voids being in contact with the alumina particles.

Description

Technical Field

[0001] This disclosure relates to cubic boron nitride sintered bodies. Background Technology

[0002] As a high-hardness material used in cutting tools, there is cubic boron nitride sintered body (hereinafter also referred to as "cBN sintered body" (Patent Document 1, Patent Document 2)).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2016-107396

[0006] Patent Document 2: International Publication No. 2012 / 057183 Summary of the Invention

[0007] The cubic boron nitride sintered body disclosed herein comprises cubic boron nitride particles, a bonding phase, and voids.

[0008] The percentage of the cubic boron nitride particles relative to the total volume of the cubic boron nitride particles and the bound phase is 40% or more and 70% or less.

[0009] The percentage of the binding phase relative to the total volume of the cubic boron nitride particles and the binding phase is 30% or more and 60% or less.

[0010] The bonding phase comprises alumina particles in an amount of 10% to 100% by volume relative to the total bonding phase.

[0011] The alumina particles have an average particle size of 50 nm or more and 250 nm or less.

[0012] The cubic boron nitride sintered body contains one or more first voids comprising more than 0.001% by volume and less than 0.100% by volume.

[0013] At least a portion of each of the first pores is in contact with the alumina particles. Attached Figure Description

[0014] Figure 1 This is an example of an image showing a contrast value in a reflected electron image of a cubic boron nitride sintered body according to Embodiment 1.

[0015] Figure 2 This is an example of a reflected electron image of a cubic boron nitride sintered body according to Embodiment 1.

[0016] Figure 3This is another example of a reflected electron image of the cubic boron nitride sintered body of Embodiment 1. Detailed Implementation

[0017] [The problem this disclosure aims to solve]

[0018] In recent years, the demand for high-efficiency machining has increased. When using tools made of cubic boron nitride for high-efficiency machining, tool life is sometimes shortened due to defects. Therefore, there is a need for a cubic boron nitride sintered body that, when used as a tool material, can also provide a long tool life in high-efficiency machining.

[0019] Therefore, the purpose of this disclosure is to provide a cubic boron nitride sintered body that, when used as a tool material, provides a tool with a long tool life even in high-efficiency machining.

[0020] [The Effects of This Disclosure]

[0021] When the cubic boron nitride sintered body of this disclosure is used as a tool material, the tool can have a long tool life even in high-efficiency machining.

[0022] [Description of embodiments of this disclosure]

[0023] First, embodiments of this disclosure will be described.

[0024] (1) The cubic boron nitride sintered body disclosed herein has cubic boron nitride particles, a bonding phase, and voids.

[0025] The percentage of the cubic boron nitride particles relative to the total volume of the cubic boron nitride particles and the bound phase is 40% or more and 70% or less.

[0026] The percentage of the binding phase relative to the total volume of the cubic boron nitride particles and the binding phase is 30% or more and 60% or less.

[0027] The bonding phase comprises alumina particles in an amount of 10% to 100% by volume relative to the total bonding phase.

[0028] The alumina particles have an average particle size of 50 nm or more and 250 nm or less.

[0029] The cubic boron nitride sintered body contains one or more first voids comprising more than 0.001% by volume and less than 0.100% by volume.

[0030] At least a portion of each of the first pores is in contact with the alumina particles.

[0031] When the cubic boron nitride sintered body of this disclosure is used as a tool material, the tool can have a long tool life even in high-efficiency machining.

[0032] (2) Preferably, the bonding phase is composed of 10% by volume or more and 98% by volume or less of the alumina particles and 2% by volume or more and 90% by volume or less of the first bonding phase particles.

[0033] The first bound phase particles comprise one or both of the following: at least one selected from the second group and at least one selected from the fourth group.

[0034] The second group consists of elements, alloys, and intermetallic compounds. The elements are selected from the first group, which consists of elements from Group 4, Group 5, and Group 6 of the periodic table, as well as aluminum, silicon, iron, cobalt, and nickel. The alloys and intermetallic compounds are composed of two or more elements selected from the first group.

[0035] The fourth group consists of the first compound and a solid solution of the first compound, wherein the first compound is composed of at least one element selected from the first group and at least one element selected from the third group consisting of nitrogen, carbon, boron, and oxygen.

[0036] The first compound does not contain alumina particles.

[0037] As a result, the tool's lifespan is further extended.

[0038] (3) Preferably, the cubic boron nitride sintered body contains a plurality of the first voids.

[0039] The average distance between the first gaps is greater than 1.0 μm and less than 20 μm.

[0040] As a result, the tool's lifespan is further extended.

[0041] (4) Preferably, the average cross-sectional area of ​​the first gap is 0.001 μm. 2 Above and 0.02μm 2 As a result, tool life is further improved.

[0042] (5) Preferably, the cubic boron nitride particles comprise first cubic boron nitride particles.

[0043] The particle size of the first cubic boron nitride particle is more than 5% and less than 50% of the average particle size of the alumina particle.

[0044] The percentage of the first cubic boron nitride particles relative to the volume of the bound phase is more than 1% and less than 30%.

[0045] The first cubic boron nitride particles comprise, on a quantity basis, more than 30% and less than 100% of the first A cubic boron nitride particles.

[0046] At least a portion of each of the first A cubic boron nitride particles is in contact with the alumina particles.

[0047] As a result, the tool's lifespan is further extended.

[0048] [Details of the embodiments disclosed herein]

[0049] Hereinafter, specific examples of the cubic boron nitride sintered body of this disclosure will be described with reference to the accompanying drawings. In the drawings of this disclosure, the same reference numerals denote the same or equivalent parts. In addition, the dimensional relationships such as length, width, thickness, and depth have been appropriately modified for the clarity and simplification of the drawings, and do not necessarily represent the actual dimensional relationships.

[0050] In this specification, expressions such as "A~B" refer to the upper and lower limits of a range (i.e., above A and below B). If no unit is recorded in A but only in B, the unit of A is the same as the unit of B.

[0051] In this specification, when compounds are represented by chemical formulas, all conventionally known atomic ratios are included unless otherwise specified, and are not necessarily limited to atomic ratios within the stoichiometric range. For example, when referred to as "TiN", the ratio of the number of atoms constituting TiN includes all conventionally known atomic ratios.

[0052] [Implementation Method 1: Cubic Boron Nitride Sintered Body]

[0053] One embodiment of this disclosure (hereinafter also referred to as "this embodiment") shows a cubic boron nitride sintered body comprising cubic boron nitride particles, a bonding phase, and voids.

[0054] The percentage of the cubic boron nitride particles relative to the total volume of the cubic boron nitride particles and the bound phase is 40% or more and 70% or less.

[0055] The percentage of the bonding phase relative to the total volume of the cubic boron nitride particles and the bonding phase is 30% to 60% (volume basis).

[0056] The bound phase comprises alumina particles in an amount of 10% to 100% by volume relative to the total bound phase.

[0057] The alumina particles have an average particle size of 50 nm or more and 250 nm or less.

[0058] The cubic boron nitride sintered body contains more than 0.001 vol% and less than 0.100 vol% of one first void.

[0059] At least a portion of each of the first voids is in contact with the alumina particle.

[0060] When the cubic boron nitride sintered body of this embodiment is used as a tool material, the tool can have a long tool life even in high-efficiency machining. The reasons for this are as follows (i) to (iv).

[0061] (i) The cubic boron nitride sintered body of this embodiment comprises cubic boron nitride particles with excellent strength and toughness, wherein the percentage of cubic boron nitride particles relative to the total volume of cubic boron nitride particles and the bonding phase is 40% by volume or more and 70% by volume or less. Therefore, the cubic boron nitride sintered body can also possess excellent strength and toughness. Consequently, tools using this cubic boron nitride sintered body exhibit excellent wear resistance and chipping resistance, resulting in a longer tool life.

[0062] (ii) The cubic boron nitride sintered body of this embodiment contains alumina particles (hereinafter also referred to as "Al2O3 particles") with excellent wear resistance, which account for 10% to 100% of the total volume of the bonding phase. Therefore, the cubic boron nitride sintered body has excellent wear resistance, and tools using the cubic boron nitride sintered body can have a long tool life.

[0063] (iii) The average particle size of the alumina particles is 50 nm or more and 250 nm or less. If the average particle size of the alumina particles is within the above range, the cubic boron nitride sintered body can have excellent toughness. Therefore, tools using this cubic boron nitride sintered body have excellent chip resistance and can have a long tool life.

[0064] (iv) When tools using cubic boron nitride sintered bodies are used for high-efficiency machining, the tool tip temperature increases. The cubic boron nitride particles and the bonding phase have different coefficients of thermal expansion, making them prone to cracking due to thermal shock and resulting in defects. In cubic boron nitride sintered bodies, the presence of voids absorbs the difference in thermal expansion coefficients between the cubic boron nitride particles and the bonding phase, thus suppressing crack formation. In particular, if at least a portion of the voids is in contact with alumina particles, the absorption effect of the difference in thermal expansion coefficients is high, resulting in excellent crack suppression. On the other hand, if the void content in the cubic boron nitride sintered body is too high, the voids themselves tend to become the initiation point for cracking.

[0065] If the content of the first void in the cubic boron nitride sintered body is 0.001 vol% or more and 0.100 vol% or less, the absorption effect of the difference in thermal expansion coefficients caused by the voids can be obtained, and the voids themselves can be suppressed from becoming the starting point of cracking. That is, if the content of the first void in the cubic boron nitride sintered body is 0.001 vol% or more and 0.100 vol% or less, the generation of cracks can be effectively suppressed. Therefore, the tool using the cubic boron nitride sintered body of this embodiment, which has a first void content of 0.001 vol% or more and 0.10 vol% or less, has excellent chip resistance and can have a long tool life. This is a new insight discovered as a result of in-depth research conducted by the inventors of this invention.

[0066] <Content of cubic boron nitride particles, voids, and bound phases>

[0067] The cubic boron nitride sintered body of this embodiment comprises cubic boron nitride particles, a binding phase, and voids. As long as the effects of this disclosure are achieved, the cubic boron nitride sintered body of this embodiment can contain unavoidable impurities caused by the raw materials used, manufacturing conditions, etc. The cubic boron nitride sintered body of this embodiment can be composed of cubic boron nitride particles, a binding phase, voids, and unavoidable impurities. The content (mass%) of unavoidable impurities in the cubic boron nitride sintered body can be 1% by mass or less. The content of unavoidable impurities in the cubic boron nitride sintered body is determined by ICP emission spectroscopy (measurement device: Shimadzu Corporation "ICPS-8100" (trademark)).

[0068] In the cubic boron nitride sintered body of this embodiment, the percentage of cubic boron nitride particles relative to the total volume of cubic boron nitride particles and the bonding phase (hereinafter also referred to as "cubic boron nitride particle content") is 40% by volume or more and 70% by volume or less. From the viewpoint of improving resistance to defects, the lower limit of the cubic boron nitride particle content is 40% by volume or more, preferably 42% by volume or more, and more preferably 45% by volume or more. From the viewpoint of improving sinterability, the upper limit of the cubic boron nitride particle content is 70% by volume or less, preferably 68% by volume or less, and more preferably 65% ​​by volume or less. The cubic boron nitride particle content is 40% by volume or more and 70% by volume or less, preferably 42% by volume or more and 68% by volume or less, and more preferably 45% by volume or more and 65% by volume or less.

[0069] In the cubic boron nitride sintered body of this embodiment, the percentage of the binding phase relative to the total volume of cubic boron nitride particles and the binding phase (hereinafter also referred to as "binding phase content") is 30% by volume or more and 60% by volume or less. From the viewpoint of improving sinterability, the lower limit of the binding phase content is 30% by volume or more, preferably 31% by volume or more, and more preferably 33% by volume or more. From the viewpoint of improving resistance to defects, the upper limit of the binding phase content of the cubic boron nitride sintered body is 60% by volume or less, preferably 58% by volume or less, and more preferably 54% by volume or less. The binding phase content of the cubic boron nitride sintered body is 30% by volume or more and 60% by volume or less, preferably 31% by volume or more and 58% by volume or less, and more preferably 33% by volume or more and 54% by volume or less.

[0070] Preferably, the cubic boron nitride sintered body of this embodiment is composed of cubic boron nitride particles, a bonding phase, and voids. The percentage of the cubic boron nitride particles relative to the total volume of the cubic boron nitride particles and the bonding phase is 40% to 70% by volume, and the percentage of the bonding phase relative to the total volume of the cubic boron nitride particles and the bonding phase is 30% to 60% by volume. Preferably, the cubic boron nitride sintered body of this embodiment is composed of cubic boron nitride particles, a bonding phase, voids, and unavoidable impurities. The percentage of the cubic boron nitride particles relative to the total volume of the cubic boron nitride particles and the bonding phase is 40% to 70% by volume, and the percentage of the bonding phase relative to the total volume of the cubic boron nitride particles and the bonding phase is 30% to 60% by volume.

[0071] The cubic boron nitride sintered body of this embodiment contains at least one first void, comprising 0.001 vol% or more and 0.100 vol% or less. A first void refers to a void in which at least a portion is in contact with alumina particles. From the viewpoint of achieving an absorption effect due to the difference in the coefficients of thermal expansion between the cubic boron nitride particles and the bonding phase, the lower limit of the content of the first void in the cubic boron nitride sintered body is 0.001 vol% or more, preferably 0.003 vol% or more, and more preferably 0.005 vol% or more. From the viewpoint of suppressing the initiation of cracking, the upper limit of the content of the first void in the cubic boron nitride sintered body is 0.100 vol% or less, preferably 0.080 vol% or less, and more preferably 0.060 vol% or less. The content of the first void in the cubic boron nitride sintered body is 0.001 vol% or more and 0.100 vol% or less, preferably 0.003 vol% or more and 0.080 vol% or less, and more preferably 0.005 vol% or more and 0.060 vol% or less.

[0072] The cubic boron nitride sintered body of this embodiment can contain voids (hereinafter also referred to as "second voids") that do not contact the alumina particles, provided that the effects of this disclosure are achieved. The content of the second voids in the cubic boron nitride sintered body is preferably 0% by volume or more and 0.002% by volume or less, more preferably 0% by volume or more and 0.001% by volume or less, and most preferably 0% by volume. That is, it is most preferable that the second voids are not present. Hereinafter, the first voids and the second voids will also be collectively referred to as "voids".

[0073] The contents of the cubic boron nitride sintered body, including the void content (volume%), the bound phase content (volume%), the cubic boron nitride particle content (volume%), the first void content (volume%), and the second void content (volume%), are determined by the following steps (A1) to (G1).

[0074] (A1) Cut the cubic boron nitride sintered body at any point to prepare a sample containing a cross-section of the cubic boron nitride sintered body. A focused ion beam apparatus or a cross-section polishing machine is used to prepare the cross-section.

[0075] (B1) The above cross-section was observed using SEM at 5000x magnification to obtain reflected electron images and secondary electron images. By setting the observation magnification to 5000x, the voids in the cubic boron nitride sintered body could be clearly identified. In the reflected electron images, areas with voids were black areas, areas with cubic boron nitride particles were dark gray areas, and areas with bound phases were light gray or white areas. In the secondary electron images, areas with voids were concave areas. By comparing the black areas (areas with voids) in the reflected electron images and the concave areas (areas with voids) in the secondary electron images, the areas with voids in the reflected electron images were determined.

[0076] Furthermore, by adjusting the brightness values ​​of the reflected electron image as described below and acquiring the image, the quantitative bias based on image analysis described later can be reduced. When capturing the reflected electron image, the image brightness values ​​are divided into 256 (minimum brightness value: 0, maximum brightness value: 255). The brightness values ​​of the regions with gaps, as determined above, are set to a range of 0 to 30, while the brightness values ​​of the regions containing cubic boron nitride particles are set to a value exceeding 30. Thus, pixels in regions with gaps can be extracted from the reflected electron image. Figure 1 An image showing the brightness value is displayed in the reflected electron image of the cubic boron nitride sintered body of this embodiment. Figure 1 In the cubic boron nitride sintered body 4, the regions containing voids 1 are black, the regions containing cubic boron nitride particles 2 are dark gray, and the regions containing the bonding phase 3 are light gray or white. Figure 1In the image, the vertical axis (not shown) orthogonal to the horizontal line X1 represents the brightness value. Figure 1 The figure indicates that the brightness value along the vertical axis at line X1 varies between 8 and 149.

[0077] (C1) The void content (the total void content (volume %) of the first void and the second void) of the cubic boron nitride sintered body was determined by the following steps. The reflected electron image with the above brightness value adjusted was binarized using image analysis software (WinROOF of Mitani Corporation) under the conditions preset by the image analysis software.

[0078] A measurement region of 12 μm × 9 μm was defined in the binarized image. Within this measurement region, the area ratio of the regions containing voids was calculated. By treating the calculated area ratio as a volume percentage, the void content (volume %) of the cubic boron nitride sintered body could be determined.

[0079] (D1) The content (volume %) of cubic boron nitride particles was determined using the following steps. The reflected electron image, with the brightness values ​​adjusted as described above, was binarized using image analysis software (WinROOF from Mitani Corporation) under pre-set conditions. In the binarized image, areas with voids were represented by black areas, areas containing cubic boron nitride particles by dark gray areas, and areas containing the bound phase by light gray or white areas.

[0080] A measurement region of 12 μm × 9 μm was defined in the binarized image. Within this measurement region, the area ratio of pixels originating from the dark field (black and dark gray areas) (pixels originating from voids and cBN particles) within the measurement field of view was calculated. The area ratio of cubic boron nitride particles was calculated by subtracting the area ratio of voids (the combined area ratio of the first and second voids) from this area ratio. The content (volume %) of cubic boron nitride particles in the cubic boron nitride sintered body was calculated by treating the calculated area ratio as a volume percentage.

[0081] (E1) The content of the bound phase (volume %) is calculated using the following steps. The area ratio of the bound phase is calculated by subtracting the dark field (pixels originating from voids and cBN particles) from the area ratio of the entire measured field of view (D1) as 100 area % above. The content of the bound phase (volume %) of the cubic boron nitride sintered body is calculated by treating the calculated area ratio as volume %.

[0082] (F1) The content (volume %) of the first void and the content (volume %) of the second void in the cubic boron nitride sintered body were determined by the following steps. The reflected electron image, adjusted for the aforementioned brightness values, was toned down using image analysis software (WinROOF from Mitani Corporation), with blue representing voids and green representing alumina particles. The alumina particles in the reflected electron image were identified using SEM-EDX (energy-dispersive X-ray spectroscopy). Specifically, areas where Al and O were detected by SEM-EDX were considered alumina particles.

[0083] exist Figure 2 An example of a reflected electron image of a cubic boron nitride sintered body according to this embodiment is shown. Figure 2 In the cubic boron nitride sintered body 4, the regions containing voids 1 are black, the regions containing cubic boron nitride particles 2 are dark gray, and the regions containing the bonding phase are light gray or white. Figure 2 In the text, the light gray region in the light gray or white region, which is the region where the bonding phase exists, corresponds to alumina particles 5.

[0084] In the reflectance electron image obtained after the aforementioned color grading, if the blue (void) region is adjacent to the green (Al2O3 particle) region, and the length of the interface between the blue and green regions is 5 nm or more, the void represented by the blue region is determined to be at least partially a first void in contact with the alumina particles. Furthermore, even if the blue (void) region is in contact with the green (Al2O3 particle) region, if the length of the interface between the blue and green regions is less than 5 nm, the region represented by the blue region does not belong to the first void and is determined to be a second void. Based on the above determination, the area ratio of the first void and the area ratio of the second void are calculated in the aforementioned measurement area. By treating the calculated area ratio as a volume percentage, the content of the first void (volume%) and the content of the second void (volume%) in the cubic boron nitride sintered body can be determined.

[0085] (G1) The above-described (A1) to (F1) steps were performed in five different measurement areas. In each measurement area, the content of voids (volume%), the content of cubic boron nitride particles (volume%), the content of the bonding phase (volume%), the content of the first void (volume%), and the content of the second void (volume%) were measured. The average of the measured values ​​in the five measurement areas was taken as the content of voids (volume%), the content of cubic boron nitride particles (volume%), the content of the bonding phase (volume%), the content of the first void (volume%), and the content of the second void (volume%) of the cubic boron nitride sintered body of this embodiment.

[0086] In this specification, very small gaps below the detection limit that cannot be detected in the above-described measurements are removed as noise.

[0087] The following has been confirmed: as long as the measurement is performed using a reflective electron image with the brightness value adjusted as described above, even if the selected measurement area is changed and the measurement is performed multiple times, there is almost no deviation in the measurement results of the content of each component. Even if the measurement area is set arbitrarily, the results will not change arbitrarily.

[0088] <Binding Phase>

[0089] Alumina Particles

[0090] In this embodiment, the bonding phase comprises alumina particles that are 10% or more and 100% or less in volume relative to the total bonding phase, and the average particle size of the alumina particles is 50 nm or more and 250 nm or less.

[0091] From the viewpoint of improving wear resistance, the lower limit of the content of alumina particles relative to the overall bound phase is 10% by volume or more, preferably 13% by volume or more, and more preferably 15% by volume or more. From the viewpoint of improving damage resistance, the upper limit of the content of alumina particles relative to the overall bound phase is 100% by volume or less, preferably 98% by volume or less, and more preferably 95% by volume or less. The content of alumina particles relative to the overall bound phase is 10% by volume or more and 100% by volume or less, preferably 10% by volume or more and 98% by volume or less, more preferably 13% by volume or more and 98% by volume or less, and more preferably 15% by volume or more and 95% by volume or less.

[0092] The content (volume %) of alumina particles in the bonding phase relative to the total bonding phase is determined by the following method. Following the same steps as the method (E1) for determining the content of the bonding phase in the cubic boron nitride sintered body described above, the content (volume %) of the bonding phase in the cubic boron nitride sintered body is calculated. Next, in the same measurement area, alumina particles are identified and their area ratio is determined according to the steps described in the method (F1) for determining the content of the first void in the cubic boron nitride sintered body described above. The content (volume %) of alumina particles in the cubic boron nitride sintered body is obtained by considering this area ratio as volume %. The percentage of the content (volume %) of alumina particles in the cubic boron nitride sintered body relative to the content (volume %) of the bonding phase in the cubic boron nitride sintered body is calculated. This percentage corresponds to the content (volume %) of alumina particles relative to the total bonding phase.

[0093] The content (volume %) of alumina particles relative to the overall bound phase was measured in five different measurement regions. The average of the measured values ​​from the five measurement regions was taken as the content (volume %) of alumina particles relative to the overall bound phase in the cubic boron nitride sintered body of this embodiment.

[0094] The following has been confirmed: as long as the above measurements are performed on the same sample, even if the selected measurement area is changed and multiple measurements are performed, the measurement results will have almost no deviation. Even if the measurement area is set arbitrarily, the results will not change arbitrarily.

[0095] In this embodiment, the average particle size of the alumina particles is 50 nm or more and 250 nm or less. Here, the average particle size of the alumina particles refers to the arithmetic mean diameter based on the number of equivalent circular diameters of the alumina particles observed in any cross-section of the cubic boron nitride sintered body. From the viewpoint of improving the toughness of the cubic boron nitride sintered body, the lower limit of the average particle size of the alumina particles is 50 nm or more, preferably 60 nm or more, and more preferably 70 nm or more. From the viewpoint of improving the defect resistance of the cubic boron nitride sintered body, the upper limit of the average particle size of the alumina particles is 250 nm or less, preferably 230 nm or less, and more preferably 200 nm or less. The average particle size of the alumina particles is 50 nm or more and 250 nm or less, preferably 60 nm or more and 230 nm or less, and more preferably 70 nm or more and 200 nm or less.

[0096] The average particle size (arithmetic mean) of the alumina particles was determined by the following method. Alumina particles were determined according to the steps described in the method (F1) for determining the content of the first void in the cubic boron nitride sintered body. In the aforementioned measurement area, the equivalent circle diameter of each alumina particle was measured using the aforementioned image analysis software. Based on the equivalent circle diameter of each alumina particle in the aforementioned measurement area, the average particle size (arithmetic mean based on the number of particles) of the alumina particles was calculated.

[0097] The above measurements were performed in five different measurement areas. The average particle size of the alumina particles in the five measurement areas was taken as the average particle size of the alumina particles in the cubic boron nitride sintered body of this embodiment.

[0098] The following has been confirmed: as long as the above measurements are performed on the same sample, even if the selected measurement area is changed and multiple measurements are performed, the measurement results will have almost no deviation. Even if the measurement area is set arbitrarily, the results will not change arbitrarily.

[0099] First-phase particles

[0100] In this embodiment, preferably, the bonding phase consists of 10% or more and 98% or less alumina particles and 2% or more and 90% or less first bonding phase particles.

[0101] The first bound phase particles comprise one or both of the following: at least one selected from the second group and at least one selected from the fourth group.

[0102] The second group consists of elements, alloys, and intermetallic compounds. The elements are selected from the first group, which consists of elements from Group 4, Group 5, Group 6 of the periodic table, aluminum, silicon, iron, cobalt, and nickel. The alloys and intermetallic compounds are composed of two or more elements selected from the first group.

[0103] The fourth group consists of the first compound and a solid solution of the first compound, wherein the first compound is composed of at least one element selected from the first group and at least one element selected from the third group, which consists of nitrogen, carbon, boron, and oxygen.

[0104] The first compound does not contain alumina particles.

[0105] The first bonding phase particles exhibit particularly high bonding strength to the cubic boron nitride particles. Therefore, the cubic boron nitride sintered body containing the first bonding phase particles possesses excellent wear resistance and chipping resistance, and tools using this cubic boron nitride sintered body can have a longer tool life.

[0106] The first bound phase particles can be any of the following forms (a) to (f).

[0107] (a) Constituting at least one selected from the second group.

[0108] (b) Includes at least one selected from the second group.

[0109] (c) Constituting at least one selected from the fourth group.

[0110] (d) includes at least one selected from the fourth group.

[0111] (e) It consists of at least one selected from the second group and at least one selected from the fourth group.

[0112] (f) includes at least one selected from the second group and at least one selected from the fourth group.

[0113] Here, Group 4 elements of the periodic table include, for example, titanium (Ti), zirconium (Zr), and hafnium (Hf). Group 5 elements include, for example, vanadium (V), niobium (Nb), and tantalum (Ta). Group 6 elements include, for example, chromium (Cr), molybdenum (Mo), and tungsten (W). Hereafter, the elements of the first group, consisting of Group 4 elements, Group 5 elements, Group 6 elements, aluminum, silicon, iron, cobalt, and nickel, will also be referred to as "Element 1".

[0114] Alloys containing the first element include, for example, Ti-Zr, Ti-Hf, Ti-V, Ti-Nb, Ti-Ta, Ti-Cr, and Ti-Mo. Intermetallic compounds containing the first element include, for example, TiCr2, Ti3Al, and Co-Al.

[0115] Examples of first compounds (nitrides) containing the aforementioned first element and nitrogen include titanium nitride (TiN), zirconium nitride (ZrN), hafnium nitride (HfN), vanadium nitride (VN), niobium nitride (NbN), tantalum nitride (TaN), chromium nitride (Cr2N), molybdenum nitride (Mo2N), tungsten nitride (WN), aluminum nitride (AlN), silicon nitride (Si3N4), cobalt nitride (CoN), nickel nitride (NiN), titanium zirconium nitride (TiZrN), titanium hafnium nitride (TiHfN), titanium vanadium nitride (TiVN), titanium niobium nitride (TiNbN), titanium tantalum nitride (TiTaN), titanium chromium nitride (TiCrN), titanium molybdenum nitride (TiMoN), titanium tungsten nitride (TiWN), titanium aluminum nitride (TiAlN, Ti2AlN, Ti3AlN), zirconium hafnium nitride (ZrHfN), zirconium vanadium nitride (ZrVN), and nitrides. Zirconium niobium (ZrNbN), zirconium tantalum nitride (ZrTaN), zirconium chromium nitride (ZrCrN), zirconium molybdenum nitride (ZrMoN), zirconium tungsten nitride (ZrWN), hafnium vanadium nitride (HfVN), hafnium niobium nitride (HfNbN), hafnium tantalum nitride (HfTaN), hafnium chromium nitride (HfCrN), hafnium molybdenum nitride (HfMoN), hafnium tungsten nitride (HfWN), vanadium niobium nitride (VNbN), vanadium tantalum nitride (VTaN) Vanadium chromium nitride (VCrN), vanadium molybdenum nitride (VMoN), vanadium tungsten nitride (VWN), niobium tantalum nitride (NbTaN), niobium chromium nitride (NbCrN), niobium molybdenum nitride (NbMoN), niobium tungsten nitride (NbWN), tantalum chromium nitride (TaCrN), tantalum molybdenum nitride (TaMoN), tantalum tungsten nitride (TaWN), chromium molybdenum nitride (CrMoN), chromium tungsten nitride (CrWN), and molybdenum tungsten nitride (MoWN).

[0116] Examples of first compounds (carbides) containing the aforementioned first element and carbon include titanium carbide (TiC), zirconium carbide (ZrC), hafnium carbide (HfC), vanadium carbide (VC), niobium carbide (NbC), tantalum carbide (TaC), chromium carbide (Cr3C2), molybdenum carbide (MoC), tungsten carbide (WC), silicon carbide (SiC), tungsten cobalt carbide (W2Co3C), and titanium aluminum carbide (Ti2AlC).

[0117] Examples of first compounds (borides) containing the aforementioned first element and boron include titanium boride (TiB2), zirconium boride (ZrB2), hafnium boride (HfB2), vanadium boride (VB2), niobium boride (NbB2), tantalum boride (TaB2), chromium boride (CrB), molybdenum boride (MoB), tungsten boride (WB), aluminum boride (AlB2), cobalt boride (Co2B), nickel boride (Ni2B), and tungsten cobalt boride (W2Co). 21 B6).

[0118] Examples of first compounds (oxides) containing the aforementioned first element and oxygen include titanium oxide (TiO2), zirconium oxide (ZrO2), hafnium oxide (HfO2), vanadium oxide (V2O5), niobium oxide (Nb2O5), tantalum oxide (Ta2O5), chromium oxide (Cr2O3), molybdenum oxide (MoO3), tungsten oxide (WO3), silicon oxide (SiO2), cobalt oxide (CoO), and nickel oxide (NiO).

[0119] Examples of first compounds (carbonitrides) containing the aforementioned first element, carbon, and nitrogen include titanium carbonitride (TiCN), zirconium carbonitride (ZrCN), hafnium carbonitride (HfCN), niobium carbonitride (TiNbCN), zirconium carbonitride (TiZrCN), hafnium carbonitride (TiHfCN), tantalum carbonitride (TiTaCN), and chromium carbonitride (TiCrCN).

[0120] Examples of first compounds (oxynitrides) composed of the aforementioned first element, oxygen, and nitrogen include titanium oxynitride (TiON), zirconium oxynitride (ZrON), hafnium oxynitride (HfON), vanadium oxynitride (VON), niobium oxynitride (NbON), tantalum oxynitride (TaON), chromium oxynitride (CrON), molybdenum oxynitride (MoON), tungsten oxynitride (WON), aluminum oxynitride (AlON), and silicon aluminum oxynitride (SiAlON).

[0121] The solid solution of the aforementioned first compound refers to a state in which two or more of these first compounds are fused into each other's crystal structures; it refers to intrusive solid solutions and substitutional solid solutions. For example, the Al2O3-ZrO2 solid solution can be cited as an example.

[0122] The first compound can be one, or two or more can be used in combination.

[0123] The content of the first binding phase particles in the binding phase is preferably 2% by volume or more and 90% by volume or less. This improves the defect resistance of the cubic boron nitride sintered body. The lower limit of the content of the first binding phase particles in the binding phase is preferably 2% by volume or more, more preferably 3% by volume or more, and more preferably 5% by volume or more. The upper limit of the content of the first binding phase particles in the binding phase is preferably 90% by volume or less, more preferably 87% by volume or less, and even more preferably 85% by volume or less.

[0124] The total content of the first bound phase particles in the bound phase is calculated using the following steps. The content of alumina particles relative to the total bound phase (volume %) is determined using the same method as for determining the content of alumina particles relative to the total bound phase. The total content of the first bound phase particles in the bound phase (volume %) is calculated by subtracting the content of alumina particles relative to the total bound phase (100 volume %) from the total bound phase (100 volume %).

[0125] The composition of the bound phase can be determined by XRD (X-ray diffraction).

[0126] <Distance between the first gap>

[0127] The cubic boron nitride sintered body of this embodiment contains a plurality of first voids, and the average distance between the first voids is preferably 1.0 μm or more and 20 μm or less. This further improves tool life. The reason for this is likely that, in the cubic boron nitride sintered body, the first voids are dispersed, suppressing crack formation substantially uniformly throughout the entire region of the cubic boron nitride sintered body.

[0128] From the viewpoint of suppressing the dense formation of first voids as the starting point of defects, the lower limit of the average distance between the first voids is preferably 1.0 μm or more, more preferably 1.5 μm or more, and even more preferably 2.0 μm or more. From the viewpoint of improving the stress mitigation effect caused by the first voids, the upper limit of the average distance between the first voids is preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less. The average distance between the first voids is preferably 1.0 μm or more and 20 μm or less, more preferably 1.5 μm or more and 15 μm or less, and even more preferably 2.0 μm or more and 10 μm or less.

[0129] The average distance between the first voids was determined using the following method. Following the same steps as in the method (F1) for determining the content of the first voids in the cubic boron nitride sintered body described above, the first voids were extracted from the reflected electron image. A measurement area (12 μm × 9 μm) was set in the binarized image. Within this measurement area, the centroid position of each first void was derived using the image processing software described above. Using the obtained centroid coordinates as the parent point, Vino segmentation was performed to calculate each Vino region. For adjacent Vino regions, the length of the line segment connecting the centroid coordinates of the parent point was calculated. The calculated length of the line segment was used as the distance between the first voids. The average distance between the first voids was calculated within the measurement area. The average distance between the first voids was measured in five different measurement areas. The average of the measured values ​​from the five measurement areas was used as the average distance between the first voids in the cubic boron nitride sintered body of this embodiment.

[0130] The following has been confirmed: as long as the above measurements are performed on the same sample, even if the selected measurement area is changed and multiple measurements are performed, the measurement results will have almost no deviation. Even if the measurement area is set arbitrarily, the results will not change arbitrarily.

[0131] <Cross-sectional area of ​​the first gap>

[0132] In the cubic boron nitride sintered body of this embodiment, the average cross-sectional area of ​​the first void is preferably 0.001 μm. 2 Above and 0.02μm 2 Therefore, tool life is further improved. This is presumably because the thermal stress mitigation effect caused by the first void is enhanced, and the first void is prevented from becoming the starting point of cracking.

[0133] From the viewpoint of improving the mitigation effect of thermal stress caused by the first void, the lower limit of the average cross-sectional area of ​​the first void is preferably 0.001 μm. 2 The above, more preferably 0.002μm 2 The above is further preferably 0.003μm. 2 That concludes the discussion. From the perspective of preventing the first pore from becoming the starting point of cracking, the upper limit of the average cross-sectional area of ​​the first pore is preferably 0.02 μm. 2 Hereinafter, 0.015 μm is more preferred. 2 Hereinafter, 0.010 μm is further preferred. 2 The average cross-sectional area of ​​the first pore is preferably 0.001 μm. 2 Above and 0.02μm 2 Hereinafter, 0.002 μm is more preferred. 2 Above and 0.015μm 2Hereinafter, 0.003 μm is further preferred. 2 Above and 0.010μm 2 the following.

[0134] The average cross-sectional area of ​​the first voids was determined using the following method. Following the same steps as in (F1) of the method for determining the content of first voids in the cubic boron nitride sintered body described above, the first voids were extracted from the reflected electron image. A measurement region (12 μm × 9 μm) was set in the binarized image. Within this measurement region, the cross-sectional area of ​​each first void was measured using the image processing software described above. In cases where two or more first voids are close together, even if the pixels representing each first void are adjacent by one pixel, the two or more first voids adjacent to that pixel are considered as one void, and the cross-sectional area is calculated. The average cross-sectional area of ​​all first voids within the measurement region was calculated. Here, the average cross-sectional area refers to the arithmetic mean based on the number of cross-sectional areas. If only one first void exists within the measurement region, the cross-sectional area of ​​that single first void is considered the average cross-sectional area. The average cross-sectional area was measured in five different measurement regions. The average of the measured values ​​from the five measurement regions was taken as the average cross-sectional area of ​​the first voids in the cubic boron nitride sintered body of this embodiment.

[0135] The following has been confirmed: as long as the above measurements are performed on the same sample, even if the selected measurement area is changed and multiple measurements are performed, the measurement results will have almost no deviation. Even if the measurement area is set arbitrarily, the results will not change arbitrarily.

[0136] <Cubic boron nitride particles>

[0137] Cubic boron nitride particles are composed of cubic boron nitride. As long as the effects of this disclosure are utilized, cubic boron nitride particles may contain unavoidable impurities.

[0138] In the cubic boron nitride sintered body of this embodiment, preferably, the cubic boron nitride particles include first cubic boron nitride particles, the particle size of which is 5% to 50% of the average particle size of the alumina particles, the percentage of the first cubic boron nitride particles relative to the volume of the binding phase is 1% to 30%, and the first cubic boron nitride particles comprise 30% to 100% of the number of first A cubic boron nitride particles, with at least a portion of each of the first A cubic boron nitride particles in contact with the alumina particles. This further improves the lifespan of cutting tools using this cubic boron nitride sintered body. The reason for this is not yet clear, but it is speculated that the contact between the first A cubic boron nitride particles, which have a smaller particle size than the alumina particles, and the alumina particles suppresses grain growth of the alumina particles, thereby increasing the flexural strength of the cubic boron nitride sintered body.

[0139] First cubic boron nitride particles

[0140] In this embodiment, the first cubic boron nitride particle refers to a cubic boron nitride particle whose particle size is 5% to 50% of the average particle size of the alumina particles. Here, the particle size of the first cubic boron nitride particle refers to the equivalent circle diameter of the first cubic boron nitride particle observed in any cross-section of the cubic boron nitride sintered body. It is presumed that this first cubic boron nitride particle is easily disposed between alumina particles, and the grain growth inhibition effect of the alumina particles caused by the first cubic boron nitride particle is easily obtained. If the particle size of the first cubic boron nitride particle is 5% or more of the average particle size of the alumina particles, the decrease in defect resistance caused by the decrease in toughness in the cubic boron nitride sintered body can be suppressed.

[0141] Specifically, the particle size of the first cubic boron nitride particles is preferably 2.5 nm or more and 125 nm or less, more preferably 5 nm or more and 100 nm or less, and even more preferably 10 nm or more and 80 nm or less.

[0142] In the cubic boron nitride sintered body of this embodiment, the first cubic boron nitride particles are determined by the following steps (A2) to (E2).

[0143] (A2) Cut the cubic boron nitride sintered body at any point to prepare a sample containing a cross-section of the cubic boron nitride sintered body. A focused ion beam apparatus or a cross-section polishing machine is used to prepare the cross-section.

[0144] (B2) The above cross-section was observed using SEM at 30,000x magnification to obtain reflected electron images and secondary electron images. The observation area was set to have a bound phase area percentage of 50% or more. In the reflected electron image, areas with voids were black areas, areas with cubic boron nitride particles were dark gray areas, and areas with bound phases were light gray or white areas. In the secondary electron image, areas with voids were concave areas.

[0145] exist Figure 3 An example of a reflected electron image in the observation region of the cubic boron nitride sintered body of this embodiment is shown. Figure 3 In the cubic boron nitride sintered body 4, the regions containing cubic boron nitride particles 2 are dark gray regions, while the regions containing the bonding phase are light gray or white regions. Figure 3 In the above, the light gray region in the light gray or white region, which is the region where the bonding phase exists, corresponds to alumina particles 5, and the white region corresponds to the first bonding phase particles 6.

[0146] (C2) The above reflected electron image was binarized using image analysis software (WinROOF from Mitani Corporation). A measurement area of ​​3.0 μm × 1.8 μm was set in the binarized image.

[0147] (D2) In the above-mentioned measurement area, using the above-mentioned image analysis software, based on the steps of (D1) of the method for determining the content (volume%) of cubic boron nitride particles, the pixels originating from cubic boron nitride particles are determined based on the pixels originating from the dark field (black area and dark gray area) (pixels originating from voids and cubic boron nitride particles) and the pixels originating from the black area (pixels originating from voids), and the equivalent circle diameter of the cubic boron nitride particle is determined.

[0148] (E2) The first cubic boron nitride particle is determined by comparing the equivalent circular diameter of each cubic boron nitride particle with the average particle size (arithmetic mean) of the alumina particles.

[0149] The percentage of the first cubic boron nitride particles relative to the volume basis of the bonding phase is preferably 1% or more and 30% or less. If the percentage of the first cubic boron nitride particles relative to the volume basis of the bonding phase is 1% or more, it is easy to obtain the grain growth suppression effect of the alumina particles caused by the first cubic boron nitride particles. If the percentage of the first cubic boron nitride particles relative to the volume basis of the bonding phase is 30% or less, the decrease in sinterability caused by the increase in the surface area of ​​the first cubic boron nitride particles with low sinterability can be suppressed. The percentage of the first cubic boron nitride particles relative to the volume basis of the bonding phase is preferably 1% or more and 30% or less, more preferably 2% or more and 25% or less, and even more preferably 3% or more and 20% or less.

[0150] In this embodiment, the percentage of the first cubic boron nitride particles relative to the volume basis of the binding phase is determined by the following steps (A3) to (D3).

[0151] (A3) Following the same steps as (A2) to (D2) of the method for determining the first cubic boron nitride particles described above, the first cubic boron nitride particles are determined in the aforementioned measurement area. Using the aforementioned image processing software, the area ratio (area %) of the first cubic boron nitride particles in the aforementioned measurement area is measured. By treating the calculated area ratio as volume %, the content (volume %) of the first cubic boron nitride particles in the cubic boron nitride sintered body is calculated.

[0152] (B3) In the above-mentioned measurement area, the content of the binding phase of the cubic boron nitride sintered body is measured by the same method as (E1) for measuring the content of the binding phase (volume%).

[0153] (C3) Based on the content (volume %) of the first cubic boron nitride particles obtained in (A3) above and the content (volume %) of the binding phase obtained in (B3) above, the percentage of the first cubic boron nitride particles relative to the binding phase based on volume is calculated. The percentage of the first cubic boron nitride particles relative to the binding phase based on volume is measured in five different measurement regions. The average of the measured values ​​in the five measurement regions is taken as the percentage of the first cubic boron nitride particles relative to the binding phase based on volume in the cubic boron nitride sintered body of this embodiment.

[0154] The following has been confirmed: as long as the above measurements are performed on the same sample, even if the selected measurement area is changed and multiple measurements are performed, the measurement results will have almost no deviation. Even if the measurement area is set arbitrarily, the results will not change arbitrarily.

[0155] "Cuboid Boron Nitride Particles, No. 1A"

[0156] In this embodiment, the first A cubic boron nitride particles refer to cubic boron nitride particles in which at least a portion of the first cubic boron nitride particles are in contact with alumina particles. Preferably, the first cubic boron nitride particles comprise 30% to 100% of the first A cubic boron nitride particles, and at least a portion of each of the first A cubic boron nitride particles is in contact with alumina particles. Therefore, it is presumably easy to obtain a grain growth suppression effect on alumina particles caused by the first cubic boron nitride particles.

[0157] From the viewpoint of improving the suppression effect on the grain growth of alumina particles brought about by the first cubic boron nitride particles, the lower limit of the content of the first α-cubic boron nitride particles based on the number of the first cubic boron nitride particles is preferably 30% or more, more preferably 40% or more, and even more preferably 50% or more. The higher the upper limit of the content of the first α-cubic boron nitride particles based on the number of the first cubic boron nitride particles, the more preferred it is; therefore, it is preferably 100% or less, and from a manufacturing viewpoint, it can be set to 98% or less or 95% or less. The content of the first α-cubic boron nitride particles based on the number of the first cubic boron nitride particles is preferably 30% or more and 100% or less, preferably 40% or more and 98% or less, and preferably 50% or more and 95% or less.

[0158] In the cubic boron nitride sintered body of this embodiment, the content of the first cubic boron nitride particle 1A as a basis of the number of the first cubic boron nitride particles is determined by the following steps (A4) to (C4).

[0159] (A4) The first cubic boron nitride particles in the above-described measurement area are determined using the same method as (A3) to (D3) in the method for determining the first cubic boron nitride particles described above. The number of first cubic boron nitride particles in the above-described measurement area is measured using the image analysis software described above. When two or more first cubic boron nitride particles are close to each other, even if adjacent pixels representing first cubic boron nitride particles are adjacent by one pixel, the two or more first cubic boron nitride particles adjacent to that pixel are considered as one first cubic boron nitride particle, and the number is counted.

[0160] (B4) In the above-described measurement area, a color grading is performed, with green representing cubic boron nitride particles and red representing alumina particles. Based on this color grading, first A cubic boron nitride particles that are in contact with at least a portion of the first cubic boron nitride particles are extracted. Here, contact between an alumina particle and a first cubic boron nitride particle means that the length of their interface is 5 nm or more. Therefore, even if a first cubic boron nitride particle is in contact with an alumina particle, if the length of their interface is less than 5 nm, the cubic boron nitride particle is not considered to be a first A cubic boron nitride particle. The number of first A cubic boron nitride particles in the above-described measurement area is measured using the image analysis software described above. When two or more first A cubic boron nitride particles are close together, even if adjacent pixels representing first A cubic boron nitride particles are adjacent by one pixel, the two or more first A cubic boron nitride particles adjacent to that pixel are considered as one, and the number is counted.

[0161] (C4) Based on the number of first cubic boron nitride particles obtained in (A3) above and the number of 1A cubic boron nitride particles obtained in (B4) above, the content rate of the first cubic boron nitride particles based on the number of 1A cubic boron nitride particles is calculated. The content rate of the first cubic boron nitride particles based on the number of 1A cubic boron nitride particles is measured in five different measurement regions. The average of the measured values ​​in the five measurement regions is taken as the content rate of the first cubic boron nitride particles based on the number of 1A cubic boron nitride particles in the cubic boron nitride sintered body of this embodiment.

[0162] The following has been confirmed: as long as the above measurements are performed on the same sample, even if the selected measurement area is changed and multiple measurements are performed, the measurement results will have almost no deviation. Even if the measurement area is set arbitrarily, the results will not change arbitrarily.

[0163] <Application>

[0164] The cubic boron nitride sintered body disclosed herein is suitable for use in cutting tools, wear-resistant tools, grinding tools, etc.

[0165] Cutting tools, wear-resistant tools, and grinding tools using the cubic boron nitride sintered body of this disclosure can be entirely composed of cubic boron nitride sintered body, or only a portion thereof (e.g., the cutting tip portion in the case of a cutting tool) can be composed of cubic boron nitride sintered body. Furthermore, a coating film can also be formed on the surface of each tool.

[0166] Cutting tools can include drill bits, end mills, indexable cutting inserts for drill bits, indexable cutting inserts for end mills, indexable cutting inserts for milling, indexable cutting inserts for turning, metalworking saws, gear cutting tools, reamers, taps, and cutting tools.

[0167] As wear-resistant tools, examples include die heads, scribing tools, scribing wheels, and dressers. As grinding tools, examples include grinding stones.

[0168] [Implementation Method 2: Method for Manufacturing Cubic Boron Nitride Sintered Body]

[0169] The cubic boron nitride sintered body disclosed herein can be produced, for example, by the following method.

[0170] <Raw Material Preparation Process>

[0171] Prepare cubic boron nitride powder (hereinafter also referred to as "cBN powder") and alumina powder. When the bonding phase includes a first bonding phase particles in addition to the alumina particles, prepare the raw material powder of the first bonding phase particles (hereinafter also referred to as "first bonding phase raw material powder").

[0172] There are no particular limitations on the cBN powder; any known cBN powder can be used. The D of the cBN powder... 50 The average particle size is not particularly limited; for example, it can be set to 0.1–12.0 μm. In this specification, the average particle size of the raw material powder refers to the median particle size D of the equivalent circle diameter. 50 The average particle size was measured using a particle size distribution measuring device (trade name: MT3300EX) manufactured by Microtrac.

[0173] Two cBN powders with different average particle sizes are preferably used. In this case, the average particle size of the cBN powder with a larger average particle size is preferably set to 0.5–5 μm. The average particle size of the cBN powder with a smaller average particle size is preferably set to 0.01–0.3 μm. By using the cBN powder with a smaller average particle size, the grain growth of alumina particles can be effectively suppressed in the sintering process described later. Therefore, the strength of the resulting cubic boron nitride sintered body is improved.

[0174] There are no particular limitations on the alumina powder; any known alumina powder can be used. The D of the alumina powder... 50 The average particle size is not particularly limited; for example, it can be set to 0.05–0.25 μm.

[0175] The first bonding phase raw material powder can be configured to have a composition identical to at least a portion of the components constituting the first bonding phase. As the bonding phase raw material powder, a powder composed of an element, an alloy, an intermetallic compound, a first compound, or a solid solution of the first compound can be used. The element is an element selected from Group 4, Group 5, Group 6 of the periodic table, aluminum, silicon, iron, cobalt, and nickel. The alloy and intermetallic compound are composed of two or more elements selected from the first group. The first compound is composed of at least one element selected from the first group and at least one element selected from a third group consisting of nitrogen, carbon, boron, and oxygen. More specifically, ZrO2 powder, Al2O3-ZrO2 solid solution powder, ZrB2 powder, TiC powder, TiN powder, Ti2AlN powder, Ti2AlC powder, WC-Co powder, Al powder, etc., can be used. The first bonding phase raw material powder is not particularly limited and can be prepared by conventionally known methods. The D of the first bonding phase raw material powder... 50 The average particle size is not particularly limited; for example, it can be set to 0.05–2 μm.

[0176] <Mixed Processes>

[0177] Next, the prepared cBN powder and alumina powder are mixed using a planetary stirrer (hereinafter referred to as "one-time mixing") to obtain a one-time mixed powder. If two cBN powders with different particle sizes are used as cBN powder, they are also mixed. An alumina medium is used for stirring. The mixing method can be either wet or dry. The mixing time for one-time mixing can be set to 0.1 hours or more and less than 2 hours, or 0.1 hours or more and less than 1.5 hours. By using an alumina medium and setting the mixing time as described above, the porosity of the cubic boron nitride sintered body can be controlled. This is a new insight discovered by the inventors of this invention.

[0178] Next, the primary mixed powder is mixed with the first bound phase powder (hereinafter also referred to as "secondary mixing") to obtain a secondary mixed powder. The mixing method is set to be a method without pulverization. Examples include jet milling, media-free planetary mixing, etc.

[0179] <Sintering Process>

[0180] The mixed powder, in contact with a WC-6%Co hard alloy disk and Co (cobalt) foil, is filled into a Ta (tantalum) container and vacuum-sealed. Using a belt-type ultra-high pressure and high temperature generator, the mixed powder filled in the Ta container is pressurized to a pressure of 5 GPa or higher and 7 GPa or lower, then heated to a temperature of 1300°C or higher and 1500°C or lower, and sintered under the pressure and temperature conditions after pressurization and heating for 15 minutes or more and 30 minutes or less. By setting the above sintering conditions, the porosity of the cubic boron nitride sintered body can be controlled. This is a new insight discovered by the inventors of this invention. Thus, a cubic boron nitride sintered body of this embodiment is produced.

[0181] <Features of the manufacturing method of this embodiment>

[0182] Previously, in the manufacture of cubic boron nitride sintered bodies containing alumina particles, the low sinterability of alumina particles easily leads to the formation of voids that can become the initiation point for cracks, resulting in a tendency for the cubic boron nitride sintered body to have reduced resistance to defects. To reduce voids, increasing the sintering temperature has been considered. However, if the sintering temperature is increased, the alumina particles undergo grain growth, increasing the grain size and reducing strength and wear resistance. Therefore, it is difficult to simultaneously achieve wear resistance and resistance to defects in cubic boron nitride sintered bodies containing alumina particles.

[0183] The inventors of this invention conducted in-depth research and discovered that by employing the above-mentioned mixing and sintering processes in the manufacturing method of cubic boron nitride sintered bodies, the void content can be controlled, and a cubic boron nitride sintered body with excellent wear resistance due to the presence of alumina particles and excellent resistance to chipping can be obtained.

[0184] [Postscript 1]

[0185] Preferably, the cubic boron nitride sintered body of this embodiment is composed of cubic boron nitride particles, a bonding phase, and voids. The percentage of the cubic boron nitride particles relative to the total volume of the cubic boron nitride particles and the bonding phase is 40% or more and 70% or less, and the percentage of the bonding phase relative to the total volume of the cubic boron nitride particles and the bonding phase is 30% or more and 60% or less.

[0186] [Postscript 2]

[0187] Preferably, the cubic boron nitride sintered body of this embodiment is composed of cubic boron nitride particles, a bonding phase, voids, and unavoidable impurities. The percentage of the cubic boron nitride particles relative to the total volume of the cubic boron nitride particles and the bonding phase is 40% or more and 70% or less, and the percentage of the bonding phase relative to the total volume of the cubic boron nitride particles and the bonding phase is 30% or more and 60% or less.

[0188] Example

[0189] The present embodiment will be further described in detail through the examples. However, the present embodiment is not limited to these examples.

[0190] [Example 1]

[0191] [Preparation of Cubic Boron Nitride Sintered Bodies]

[0192] Prepare cubic boron nitride sintered bodies for each of the sample No. shown in Tables 1 to 4 according to the following steps.

[0193] <Raw Material Preparation Process>

[0194] Two known cBN powders with different average particle sizes (average particle size 2 μm (referred to as "large cBN powder particle size" in Table 1) and average particle size 0.1 μm (referred to as "small cBN powder particle size" in Table 1)), a known alumina powder (average particle size 0.1 μm, referred to as "Al2O3 powder" in Table 1), and a known first binding phase raw material powder were prepared. As the first binding phase powders, the following powders were prepared: ZrO2 powder (average particle size 1 μm), Al2O3-ZrO2 solid solution powder (average particle size 1 μm), ZrB2 powder (average particle size 2 μm), TiC powder (average particle size 1.2 μm), TiN powder (average particle size 0.5 μm), Ti2AlN powder (average particle size 0.4 μm), Ti2AlC powder (average particle size 0.5 μm), WC-Co powder (average particle size 2 μm), Al powder (average particle size 2 μm), NbN powder (average particle size 2 μm), HfC powder (average particle size 2 μm), Mo2N powder (average particle size 2 μm), Si3N4 powder (average particle size 2 μm), and VC powder (average particle size 2 μm).

[0195] cBN powder, alumina powder, and the first binding phase raw material powder were prepared according to the mixing ratios (volume basis) shown in Table 1. In Table 1, "-" indicates that the corresponding raw material powder was not used. For example, in sample 2, cBN powder (average particle size 2 μm, large particle size) : Al2O3 powder : ZrO2 powder : Al powder = 55.0 : 18.0 : 22.0 : 5.0 was used.

[0196] Table 1

[0197]

[0198] <Mixing Process>

[0199] Next, cBN powder and alumina powder were mixed under the conditions described in the "Method", "Time" and "Medium" columns of Table 2 to obtain a single-mixed powder (single-mix). For example, in Sample 1, an alumina medium with a diameter of 0.5 mm was used in a planetary stirrer and mixed for 0.25 hours.

[0200] Next, the primary mixed powder and the first bound phase powder were mixed under the conditions specified in the "Method," "Hours / Number of Times," and "Media" columns of "Secondary Mixing" in Table 2 to obtain a secondary mixed powder. For example, in Sample 1, a wet milling machine was used for 30 passes. In Sample 9, the mixture was mixed for 20 hours using a ball mill with a 5 mm diameter cemented carbide media.

[0201] <Sintering Process>

[0202] The mixed powder, in contact with a WC-6%Co hard alloy disk and Co (cobalt) foil, was filled into a Ta (tantalum) container and vacuum-sealed. Using a belt-type ultra-high pressure, high-temperature generator, the mixed powder filled in the Ta container was pressurized to 6 GPa, then heated to the temperature listed in the "Temperature" column of Table 2 under "Sintering Conditions." Sintering was performed under the pressure and temperature conditions specified in the "Time" column to obtain a cubic boron nitride sintered body. For example, in sample 1, sintering was performed at a pressure of 6 GPa and a temperature of 1350 °C for 0.25 hours to obtain a cubic boron nitride sintered body.

[0203] Table 2

[0204]

[0205] <Evaluation>

[0206] Content (volume %) of cubic boron nitride particles, content (volume %) of the bound phase, content (volume %) of the first void, and content (volume %) of the second void.

[0207] For each cubic boron nitride sintered body, the contents (volume%) of cubic boron nitride particles, the contents (volume%) of the bonding phase, the contents (volume%) of the first void, and the contents (volume%) of the second void were measured. The specific measurement method is as described in Example 1, and therefore will not be repeated. The contents (volume%) of the first void and the contents (volume%) of the second void are shown in the "First Void Content" and "Second Void Content" columns of Tables 3 and 4. In all samples, it was confirmed that the cubic boron nitride sintered body consisted of cubic boron nitride particles, the bonding phase, and voids. That is, the total contents (volume%) of cubic boron nitride particles and the bonding phase in the cubic boron nitride sintered body were calculated by subtracting the contents (volume%) of the first void and the contents (volume%) of the second void from the total cubic boron nitride sintered body (100 vol%). In all samples, it was confirmed that the volume ratio of cubic boron nitride particles to the binder phase in the cubic boron nitride sintered body maintained the ratio of the raw material cBN powder (the sum of both when two types were used) to the binder phase raw material powder (the sum of alumina powder and the first binder phase raw material powder).

[0208] Composition of the bound phase

[0209] For each cubic boron nitride sintered body, the composition of the bonding phase and the content (volume%) of alumina particles relative to the total bonding phase were determined. The specific measurement method is as described in Example 1, and therefore will not be repeated. It was confirmed that the bonding phase of Sample 1 consisted of 100 vol% alumina particles. It was confirmed that the bonding phase of the other samples consisted of alumina particles and a first bonding phase. That is, the total of alumina particles in the bonding phase and the first bonding phase particles was 100 vol%. The composition of the first bonding phase for each sample is shown in the "Composition of First Bonding Phase" column of Tables 3 and 4. The content (volume%) of alumina particles relative to the total bonding phase is shown in the "Al2O3 / Bonding Phase" column of Tables 3 and 4. In all samples, the value obtained by subtracting the content (volume%) of alumina particles relative to the total bonding phase from the total bonding phase (100 vol%) corresponds to the content of the first bonding phase particles in the bonding phase.

[0210] Average particle size of alumina particles

[0211] For each cubic boron nitride sintered body, the average particle size (arithmetic mean diameter based on the number of equivalent circle diameters) of the alumina particles was measured. The specific measurement method is as described in Embodiment 1, and therefore will not be repeated. The results are shown in the "Average Particle Size of Al2O3" column of Tables 3 and 4.

[0212] The distance between the first gap

[0213] For each cubic boron nitride sintered body sample, the average distance between the first voids was measured. The specific measurement method is as described in Embodiment 1, and therefore will not be repeated. The results are shown in the "Distance between the first voids" column of Tables 3 and 4.

[0214] Cross-sectional area of ​​the first gap

[0215] For each cubic boron nitride sintered body sample, the average cross-sectional area of ​​the first void was measured. The specific measurement method is as described in Embodiment 1, and therefore will not be repeated. The results are shown in the "Cross-sectional area of ​​the first void" column of Tables 3 and 4.

[0216] First cubic boron nitride particles

[0217] For each sample of cubic boron nitride sintered body, a first cubic boron nitride particle with a particle size of 5% to 50% of the average particle size of alumina particles was identified, and the percentage of the binding phase relative to the first cubic boron nitride particle was measured as a volume basis. The specific measurement method is as described in Example 1, and therefore will not be repeated. The results are shown in the "First cBN / Binding Phase" column of Tables 3 and 4.

[0218] For the cubic boron nitride sintered bodies of each sample, the content of the first cubic boron nitride particles (based on the number of the first cBN particles, i.e., cA) was determined. The specific determination method is as described in Embodiment 1, and therefore will not be repeated. The results are shown in the "First A-cBN / First cBN" column of Tables 3 and 4. Samples marked with "-" in the "First A-cBN / First cBN" column do not contain first cubic boron nitride particles, therefore this measurement was not performed.

[0219] <Cutting Test>

[0220] Cutting tools (shape: TCGW110208) were fabricated using cBN sintered bodies from specimens 1 to 48. Cutting tests were conducted on these tools using a machining center under the following cutting conditions. These cutting conditions are equivalent to high-efficiency, high-load cutting of cast iron.

[0221] Workpiece to be cut: Centrifugally cast cast iron

[0222] Cutting speed Vc: 1000m / min

[0223] Feed rate f: 0.35 mm / rev

[0224] Cut Ap: 0.2mm

[0225] Coolant: Wet

[0226] Cutting method: 50 cuts / 0.8km, cutting a length of 0.8km with a certain kerf, resulting in 50 tool-workpiece collisions.

[0227] Evaluation method: Derive the cutting distance (km) up to the point of failure. The longer the cutting distance, the longer the tool life.

[0228] The results are shown in the "Lifetime" column of Tables 3 and 4.

[0229]

[0230]

[0231] <Inspection>

[0232] The cubic boron nitride sintered bodies of samples 1, 2, 4 to 6, 10, 11, 14 to 48 are equivalent to the examples.

[0233] In the cubic boron nitride sintered body of sample 3, the average particle size of alumina particles is less than 50 nm, which is equivalent to the comparative example.

[0234] In the cubic boron nitride sintered body of sample 7, the average particle size of alumina particles is greater than 250 nm, which is equivalent to the comparative example.

[0235] In the cubic boron nitride sintered body of sample 8, the content of the first void is greater than 0.10% by volume, which is equivalent to the comparative example.

[0236] In the cubic boron nitride sintered body of sample 9, the content of the first void is less than 0.001% by volume, which is equivalent to the comparative example.

[0237] In the cubic boron nitride sintered body of sample 12, the percentage of cubic boron nitride particles relative to the total volume of cubic boron nitride particles and the bonding phase is greater than 70% by volume, and the content of the first void is greater than 0.10% by volume, which is equivalent to a comparative example.

[0238] In the cubic boron nitride sintered body of sample 13, the content of cubic boron nitride particles relative to the total content of cubic boron nitride particles and the bonding phase is less than 39% by volume, and the content of the first void is less than 0.001% by volume, which is equivalent to the comparative example.

[0239] The following was confirmed: the cubic boron nitride sintered bodies (Examples) of Samples 1, 2, 4-6, 10, 11, 14-48 exhibited longer tool life compared to the cubic boron nitride sintered bodies (Comparative Examples) of Samples 3, 7-9, 12, and 13. This is presumably because the samples conforming to the Examples exhibited excellent resistance to chipping even under high-efficiency, high-load cutting of cast iron.

[0240] The embodiments and examples of this disclosure have been described above, but it is also intended from the outset that the above-described embodiments and examples may be appropriately combined or modified.

[0241] The embodiments and examples disclosed herein should be considered exemplary in all respects, and not restrictive. The scope of the invention is defined not by the foregoing embodiments and examples, but by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0242] Explanation of reference numerals in the attached figures

[0243] 1: Void; 2: Cubic boron nitride particles; 3: Binding phase; 4: Cubic boron nitride sintered body; 5: Alumina particles; 6: First binding phase particles.

Claims

1. A cubic boron nitride sintered body, wherein, The cubic boron nitride sintered body comprises cubic boron nitride particles, a bonding phase, and voids. The percentage of the cubic boron nitride particles relative to the total volume of the cubic boron nitride particles and the bound phase is 40% or more and 70% or less. The percentage of the bonding phase relative to the total volume of the cubic boron nitride particles and the bonding phase is 30% to 60% (by volume). The bonding phase comprises alumina particles in an amount of 10% to 100% by volume relative to the total bonding phase. The alumina particles have an average particle size of 50 nm or more and 250 nm or less. The cubic boron nitride sintered body contains one or more first voids comprising more than 0.001% by volume and less than 0.100% by volume. At least a portion of each of the first pores is in contact with the alumina particles.

2. The cubic boron nitride sintered body according to claim 1, wherein, The bonding phase consists of 10% by volume and 98% by volume of the alumina particles and 2% by volume and 90% by volume of the first bonding phase particles. The first bound phase particles comprise one or both of the following: at least one selected from the second group and at least one selected from the fourth group. The second group consists of elements, alloys, and intermetallic compounds. The elements are selected from the first group, which consists of elements from Group 4, Group 5, and Group 6 of the periodic table, as well as aluminum, silicon, iron, cobalt, and nickel. The alloys and intermetallic compounds are composed of two or more elements selected from the first group. The fourth group consists of the first compound and a solid solution of the first compound, wherein the first compound is composed of at least one element selected from the first group and at least one element selected from the third group consisting of nitrogen, carbon, boron, and oxygen. The first compound does not contain alumina particles.

3. The cubic boron nitride sintered body according to claim 1 or 2, wherein, The cubic boron nitride sintered body contains a plurality of the first voids. The average distance between the first gaps is greater than 1.0 μm and less than 20 μm.

4. The cubic boron nitride sintered body according to any one of claims 1 to 3, wherein, The average cross-sectional area of ​​the first void is 0.001 μm. 2 Above and 0.02μm 2 the following.

5. The cubic boron nitride sintered body according to any one of claims 1 to 4, wherein, The cubic boron nitride particles comprise first cubic boron nitride particles. The particle size of the first cubic boron nitride particle is more than 5% and less than 50% of the average particle size of the alumina particle. The percentage of the first cubic boron nitride particles relative to the volume of the bound phase is more than 1% and less than 30%. The first cubic boron nitride particles comprise, on a quantity basis, more than 30% and less than 100% of the first A cubic boron nitride particles. At least a portion of each of the first A cubic boron nitride particles is in contact with the alumina particles.

6. The cubic boron nitride sintered body according to any one of claims 1 to 5, wherein, The content of the first void is 0.005% by volume or more and 0.060% by volume or less.

7. The cubic boron nitride sintered body according to any one of claims 1 to 6, wherein, The cubic boron nitride sintered body contains more than 0% by volume and less than 0.002% by volume of a second void that does not contact the alumina particles.

8. The cubic boron nitride sintered body according to any one of claims 1 to 7, wherein, The alumina particles have an average particle size of 70 nm or more and 200 nm or less.

9. The cubic boron nitride sintered body according to claim 3, wherein, The average distance between the first gaps is greater than 2.0 μm and less than 10 μm.

10. The cubic boron nitride sintered body according to any one of claims 4 to 9, wherein, The average cross-sectional area of ​​the first void is 0.003 μm. 2 Above and 0.010μm 2 the following.

11. The cubic boron nitride sintered body according to any one of claims 5 to 10, wherein, The percentage of the first cubic boron nitride particles relative to the volume basis of the bound phase is more than 3% and less than 20%.

12. The cubic boron nitride sintered body according to claim 5, wherein, The content of the first cubic boron nitride particle is 50% or more and 95% or less.

13. The cubic boron nitride sintered body according to any one of claims 1 to 12, wherein, The cubic boron nitride sintered body is composed of cubic boron nitride particles, the bonding phase, and the voids.

14. The cubic boron nitride sintered body according to any one of claims 1 to 12, wherein, The cubic boron nitride sintered body is composed of cubic boron nitride particles, the bonding phase, the voids, and unavoidable impurities.

15. The cubic boron nitride sintered body according to claim 14, wherein, The unavoidable impurities in the cubic boron nitride sintered body are less than 1% by mass.

Images