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

Abstract

Provided is a cubic boron nitride sintered body that can extend the life of a tool because of excellent wear resistance and breakage resistance. The cubic boron nitride sintered body includes cubic boron nitride and a binder phase, the content of the cubic boron nitride is 81 vol% or more and 95 vol% or less relative to the total amount of the sintered body; the content of the binder phase is 5 vol% or more and 19 vol% or less relative to the total amount of the sintered body; the content of Al contained in the binder phase is 0.5 mass% or more and 5 mass% or less relative to the total of 100 mass% of all elements contained in the sintered body; the content of W contained in the binder phase is 2 mass% or more and 10 mass% or less relative to the total of 100 mass% of all elements contained in the sintered body; the content of V contained in the binder phase is 2 mass% or more and 8 mass% or less relative to the total of 100 mass% of all elements contained in the sintered body; and the content of Cr contained in the binder phase is 0 mass% or more and 5 mass% or less relative to the total of 100 mass% of all elements contained in the sintered body.

Description

TECHNICAL FIELD

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

[0002] Cubic boron nitride (hereinafter also referred to as "cBN") has a high hardness next to diamond and excellent thermal conductivity. Moreover, cubic boron nitride has a characteristic of having a poor affinity with iron as compared with diamond. Therefore, a cubic boron nitride sintered body composed of a binding phase of metal or ceramic and cubic boron nitride is used for cutting tools or wear-resistant tools and the like.

[0003] Sintered metals have good formability and generally have a complex shape, and therefore, when processing is performed using a tool, breakage of the tool due to thermal shock is likely to occur. Moreover, since sintered metals include hard particles, the tool is likely to be worn. Therefore, cubic boron nitride is generally used in the processing of sintered metals, and particularly, a cubic boron nitride sintered body having a high content of cubic boron nitride has been intensively studied.

[0004] For example, Patent Literature 1 discloses a cBN sintered body in which cBN accounts for 40 to 80 area % (area percentage), the binding phase has an α phase and a β phase, the α phase is (Ti 1-x V x )(C 1-y N y ) having an average composition of x = 0.30 to 0.70 and y = 0.00 to 0.50, and accounts for 70 to 97 area % in the binding phase; the β phase is one of oxides, nitrides, and borides of Al having an average particle diameter of 0.05 to 0.40 μm, and accounts for 3 to 20 area % in the binding phase; the α phase has an A field and a B field, the A field is (Ti 1-xA V xA )(C 1-yA N yA ) in which xA= 0.10 to 0.30 and yA= 0.00 to 0.50, and the B field is (Ti 1-xB V xB )(C 1-yB N yB ) in which xB= 0.70 to 0.90 and yB= 0.00 to 0.50, and the sum of the A field and the B field is 50 area % or more of the α phase.

[0005] In addition, for example, Patent Literature 2 discloses a cBN-based sintered body which is a high-strength cBN-based sintered body, and contains (Ti 1-x V x )(C 1-y N y(x: 0.1 to 0.4, y: 0.1 to 0.5) (hereinafter referred to as the A component), one or two or more of carbides, nitrides, and carbonitrides of Ti (hereinafter referred to as the B component), one or two or more of carbides, nitrides, and carbonitrides of V (hereinafter referred to as the C component), wherein the A component is contained at 10 to 40 vol% (volume percent), the B component is contained at 2 to 10 vol%, the C component is contained at 2 to 10 vol%, but the B component + the C component is contained at 6 to 20 vol%, the A component / the B component + the C component is contained at 1.5 to 7 vol%, and the remainder is cubic boron nitride, and the cutting tool made of the cBN-based sintered body further contains one or two or more of Al2O3, AlN, and AlB2 at 1 to 10 vol%.

[0006] Further, for example, Patent Literature 3 discloses a cubic boron nitride sintered body characterized by being composed of 85 to 95 vol% (volume percent) of cubic boron nitride, 5 to 15 vol% of a binding phase, and inevitable impurities, the binding phase is composed of three or more compounds selected from the group consisting of carbides, nitrides, carbonitrides, oxides, and mutual solid solutions thereof of elements selected from the group consisting of Al, V, Cr, Mn, Co, Ni, Nb, and Mo; the amount of aluminum element contained in the cubic boron nitride sintered body is 0.5 to 5 mass% (mass percent) with respect to the total mass of the cubic boron nitride sintered body; but the binding phase does not contain elemental metals and alloys.

[0007] Prior Art Documents

[0008] Patent Literature

[0009] Patent Literature 1: Japanese Patent Publication No. 2021-151943

[0010] Patent Literature 1: Japanese Patent Publication No. H09-136203

[0011] Patent Literature 1: International Patent Publication No. 2013 / 069657

[0012] Technical Problem

[0013] In recent years, further pursuit of high efficiency in cutting processing has been pursued, and thus high speed, high feed, and deep cutting have become more pronounced. Along with such a tendency, in high-speed processing of sintered metals, cubic boron nitride sintered bodies that can have excellent wear resistance and damage resistance and a long tool life have also been pursued.

[0014] In this background, in the cubic boron nitride sintered body described in Patent Literature 1, the proportion of cubic boron nitride is low, and the wear resistance is insufficient. In addition, in the cubic boron nitride-based sintered body described in Patent Literature 2 and the cubic boron nitride sintered body described in Patent Literature 3, the binding phase does not contain W as a metal element other than Ti and V, and in some cases, the toughness is insufficient, and the damage resistance is likely to decrease.

[0015] The present application has an object to provide a cubic boron nitride sintered body having excellent wear resistance and damage resistance, and thus capable of prolonging tool life. SUMMARY

[0016] The present inventors have repeatedly studied to prolong tool life, and found that the cubic boron nitride sintered body can be improved in wear resistance and damage resistance by being provided with a specific structure, and thus can prolong tool life, and thus completed the present application.

[0017] The gist of the present application is as follows.

[0018] [1] A cubic boron nitride sintered body comprising cubic boron nitride and a binding phase,

[0019] The content of the cubic boron nitride is 81 vol% or more and 95 vol% or less with respect to the total amount of the sintered body;

[0020] The content of the binding phase is 5 vol% or more and 19 vol% or less with respect to the total amount of the sintered body;

[0021] The content of Al contained in the binding phase is 0.5 mass% or more and 5 mass% or less with respect to the total of 100 mass% of all elements contained in the sintered body;

[0022] The content of W contained in the binding phase is 2 mass% or more and 10 mass% or less with respect to the total of 100 mass% of all elements contained in the sintered body;

[0023] The content of V contained in the binding phase is 2 mass% or more and 8 mass% or less with respect to the total of 100 mass% of all elements contained in the sintered body;

[0024] The content of Cr contained in the binding phase is 0 mass% or more and 5 mass% or less with respect to the total of 100 mass% of all elements contained in the sintered body.

[0025] [2] The cubic boron nitride sintered body according to [1], wherein, in the binder phase, the first material S1 is composed of a compound containing W, the second material S2 is composed of a compound containing V and not containing W, and a ratio (S1 / (S1+S2)) of a content (vol%) of the first material S1 to a total content (vol%) of the first material S1 and the second material S2 is 0.35 or more and 1 or less.

[0026] [3] The cubic boron nitride sintered body according to [2], wherein a total content (vol%) of the first material S1 and the second material S2 with respect to a total amount of the binder phase is 35 vol% or more and 97 vol% or less.

[0027] [4] The cubic boron nitride sintered body according to any one of [1] to [3], wherein an average particle diameter of the cubic boron nitride is 0.5 μm or more and 3.0 μm or less.

[0028] [5] A coated cubic boron nitride sintered body comprising the cubic boron nitride sintered body according to any one of [1] to [3], and a coating layer formed on a surface of the cubic boron nitride sintered body,

[0029] an average thickness of the coating layer is 0.5 μm or more and 5.0 μm or less.

[0030] According to the present application, it is possible to provide a cubic boron nitride sintered body having excellent wear resistance and breakage resistance, and thus it is possible to prolong tool life. DETAILED DESCRIPTION

[0031] Hereinafter, an embodiment of the present application (hereinafter, simply referred to as "the present embodiment") will be described in detail, but the present application is not limited to the following present embodiment. The present application can be variously modified without departing from the scope of the gist thereof.

[0032] [Cubic boron nitride sintered body]

[0033] The cubic boron nitride sintered body of the present embodiment includes cubic boron nitride (hereinafter also referred to as "cBN") and a binder phase, the content of the cBN is 81 vol% or more and 95 vol% or less with respect to the total amount of the sintered body; the content of the binder phase is 5 vol% or more and 19 vol% or less with respect to the total amount of the sintered body; the content of Al contained in the binder phase is 0.5 mass% or more and 5 mass% or less with respect to the total of 100 mass% of all elements contained in the sintered body; the content of W contained in the binder phase is 2 mass% or more and 10 mass% or less with respect to the total of 100 mass% of all elements contained in the sintered body; the content of V contained in the binder phase is 2 mass% or more and 8 mass% or less with respect to the total of 100 mass% of all elements contained in the sintered body; and the content of Cr contained in the binder phase is 0 mass% or more and 5 mass% or less with respect to the total of 100 mass% of all elements contained in the sintered body.

[0034] The cubic boron nitride sintered body of the present embodiment can improve the wear resistance and the breakage resistance by the above structure, and thus can prolong the tool life.

[0035] The main reason why the cubic boron nitride sintered body of the present embodiment improves the wear resistance and the breakage resistance of the tool and prolongs the tool life is not clear, but the present inventors believe that the main reason is as follows, but is not limited thereto. That is, in the cubic boron nitride sintered body of the present embodiment, by making the content of the cBN 81 vol% or more, the proportion of the binder phase is relatively low, and thus the hardness is improved and the wear resistance is excellent. On the other hand, in the cubic boron nitride sintered body of the present embodiment, by making the content of the cBN 95 vol% or less, the falling of the cBN particles can be suppressed, and thus the wear resistance is excellent. Furthermore, in cutting processing, the surface roughness of the machined surface of the workpiece is small, and the appearance after processing tends to be good.

[0036] In addition, in the cubic boron nitride sintered body of the present embodiment, by making the content of the binder phase 5 vol% or more, the falling of the cBN particles can be suppressed, and thus the wear resistance is excellent. On the other hand, in the cubic boron nitride sintered body, by making the content of the binder phase 19 vol% or less, the proportion of the content of the cBN is relatively increased, and thus the hardness is improved and the wear resistance is excellent.

[0037] In the cubic boron nitride sintered body of the present embodiment, by making the Al content contained in the binding phase 0.5 mass% or more, the cBN particles are prevented from falling off by the reaction of the Al element with the oxygen atoms on the surface of the cBN particles. In addition, in the cubic boron nitride sintered body of the present embodiment, by making the Al content contained in the binding phase 5 mass% or less, the formation of Al nitride and Al boride is suppressed, and thus the wear resistance is excellent. In the cubic boron nitride sintered body of the present embodiment, by making the W content contained in the binding phase 2 mass% or more, the toughness of the binding phase is improved, and thus the breakage resistance is excellent. On the other hand, in the cubic boron nitride sintered body, by making the W content 10 mass% or less, the hardness of the binding phase is prevented from being lowered, and thus the wear resistance is excellent. Furthermore, in the cubic boron nitride sintered body of the present embodiment, by making the V content contained in the binding phase 2 mass% or more, the diffusion of the W element to the entire binding phase is promoted, the toughness of the binding phase is improved, and thus the breakage resistance is excellent. On the other hand, in the cubic boron nitride sintered body of the present embodiment, by making the V content 8 mass% or less, the sinterability of the cubic boron nitride sintered body is improved. In the cubic boron nitride sintered body of the present embodiment, by making the Cr content contained in the binding phase 0 mass% or more, in the case where Cr is contained, the effect of improving the sinterability of the cubic boron nitride sintered body is obtained. On the other hand, in the cubic boron nitride sintered body, by making the Cr content 5 mass% or less, the toughness of the binding phase is improved, and thus the breakage resistance is excellent.

[0038] The above-described effects complement each other, and thus the cubic boron nitride sintered body of the present embodiment can improve the wear resistance and the breakage resistance, and thus the tool life is extended.

[0039] The cubic boron nitride sintered body of the present embodiment includes cBN and a binding phase. The content of the cBN is 81 vol% or more and 95 vol% or less with respect to the total amount of the sintered body. The content of the binding phase is 5 vol% or more and 19 vol% or less with respect to the total amount of the sintered body. Furthermore, in the cubic boron nitride sintered body of the present embodiment, the total content of the cBN and the binding phase is 100 vol%.

[0040] [Cubic boron nitride (cBN)]

[0041] In the cubic boron nitride sintered body of the present embodiment, by making the content of the cBN 81 vol% or more, the proportion of the binding phase is relatively low, and thus the hardness is improved, and the wear resistance is excellent. On the other hand, in the cubic boron nitride sintered body of the present embodiment, by making the content of the cBN 95 vol% or less, the cBN particles are prevented from falling off, and thus the wear resistance is excellent. From the same perspective, the content of the cBN is preferably 83 vol% or more and 93 vol% or less, and more preferably 85 vol% or more and 91 vol% or less.

[0042] In the cubic boron nitride sintered body of the present embodiment, the content (vol%) of the cBN and the binder phase can be found by taking an arbitrary cross section with a scanning electron microscope (SEM), and then analyzing the taken structure photograph with a commercially available image analysis software. Specifically, it can be found by the method described in the Examples described later.

[0043] In the cubic boron nitride sintered body of the present embodiment, the average particle diameter of the cBN is preferably 0.5 μm or more and 3.0 μm or less. By making the average particle diameter of the cBN 0.5 μm or more in the cubic boron nitride sintered body, the cBN particles can be inhibited from falling off, and by making the average particle diameter of the cBN 3.0 μm or less, the mechanical strength is improved, and the breakage resistance tends to be excellent. From the same perspective, the average particle diameter of the cBN is more preferably 0.5 μm or more and 2.5 μm or less, and further preferably 0.5 μm or more and 2.0 μm or less.

[0044] In the present embodiment, the average particle diameter of the cBN can be found, for example, in the following manner.

[0045] The cross-sectional structure of the cubic boron nitride sintered body is taken with an SEM. The area of the cBN particles is found by analyzing the taken structure photograph, the diameter of a circle equal to the area of the cBN particles is found, and this is taken as the particle diameter of the cBN.

[0046] The average value of the particle diameters of a plurality of cBN particles is found, and this is taken as the average particle diameter of the cBN. The average particle diameter of the cBN can be found by analyzing the image of the cross-sectional structure of the cubic boron nitride sintered body using a commercially available image analysis software. Specifically, it can be found by the method described in the Examples described later.

[0047] [Binder phase]

[0048] In the cubic boron nitride sintered body of the present embodiment, by making the content of the binder phase 5 vol% or more, the cBN particles can be inhibited from falling off, and the wear resistance is excellent. On the other hand, in the cubic boron nitride sintered body, by making the content of the binder phase 19 vol% or less, the content ratio of the cBN is relatively increased, the hardness is improved, and thus the wear resistance is excellent. From the same perspective, the content of the binder phase is preferably 7 vol% or more and 17 vol% or less, and more preferably 9 vol% or more and 15 vol% or less.

[0049] In the cubic boron nitride sintered body of the present embodiment, the content of Al contained in the binding phase is 0.5 mass% or more and 5 mass% or less with respect to the total of 100 mass% of all elements contained in the sintered body; the content of W contained in the binding phase is 2 mass% or more and 10 mass% or less with respect to the total of 100 mass% of all elements contained in the sintered body; the content of V contained in the binding phase is 2 mass% or more and 8 mass% or less with respect to the total of 100 mass% of all elements contained in the sintered body; and the content of Cr contained in the binding phase is 0 mass% or more and 5 mass% or less with respect to the total of 100 mass% of all elements contained in the sintered body.

[0050] In the cubic boron nitride sintered body of the present embodiment, by making the content of Al contained in the binding phase 0.5 mass% or more with respect to the total of 100 mass% of all elements contained in the sintered body, the cBN particles are inhibited from falling off by causing the Al element to react with oxygen atoms on the surface of the cBN particles. In addition, in the cubic boron nitride sintered body of the present embodiment, by making the content of Al contained in the binding phase 5 mass% or less, the formation of Al nitride and Al boride is inhibited, and thus the wear resistance is excellent. From the same perspective, the content of Al contained in the binding phase is preferably 0.5 mass% or more and 3.5 mass% or less, and more preferably 0.5 mass% or more and 2 mass% or less.

[0051] In the cubic boron nitride sintered body of the present embodiment, by making the content of W contained in the binding phase 2 mass% or more with respect to the total of 100 mass% of all elements contained in the sintered body, the toughness of the binding phase is improved, and thus the breakage resistance is excellent. On the other hand, in the cubic boron nitride sintered body, by making the content of W 10 mass% or less, the hardness of the binding phase is inhibited from decreasing, and thus the wear resistance is excellent. From the same perspective, the content of W contained in the binding phase is preferably 2 mass% or more and 9 mass% or less, and more preferably 2 mass% or more and 8 mass% or less.

[0052] In the cubic boron nitride sintered body of the present embodiment, by making the content of V contained in the binding phase 2 mass% or more with respect to the total of 100 mass% of all elements contained in the sintered body, the diffusion of the W element to the entire binding phase is promoted, the toughness of the binding phase is improved, and thus the breakage resistance is excellent. On the other hand, in the cubic boron nitride sintered body of the present embodiment, by making the content of V 8 mass% or less, the sinterability of the cubic boron nitride sintered body is improved. From the same perspective, the content of V contained in the binding phase is preferably 2.5 mass% or more and 8 mass% or less, and more preferably 3 mass% or more and 8 mass% or less.

[0053] In the cubic boron nitride sintered body of the present embodiment, by making the content of Cr included in the bonding phase 0 mass% or more with respect to the total of 100 mass% of all elements included in the sintered body, the effect of improving the sinterability of the cubic boron nitride sintered body is obtained in the case where Cr is included. On the other hand, in the cubic boron nitride sintered body, by making the content of Cr 5 mass% or less, the toughness of the bonding phase is improved, so that the damage resistance is excellent. From the same perspective, the content of Cr included in the bonding phase is preferably 0 mass% or more and 4.4 mass% or less, more preferably 0 mass% or more and 3.8 mass% or less.

[0054] In the cubic boron nitride sintered body of the present embodiment, other elements besides the above can be included in the bonding phase. Specific examples of the other elements include Ti, Zr, Nb, Mo, Hf, Ta, Mn, Fe, Co, Ni, and the like, but are not limited thereto, and are preferably Ti, Mo, Ta, Co, Ni, more preferably Ti, Co.

[0055] For example, these other elements originate from the barrel or balls for a ball mill, high-melting-point metal capsules for filling, and the like, and can be contained unavoidably or intentionally added. In addition, the content of the above other elements is not particularly limited, and for example, the content of the above other elements can be 0 mass% or more and 10 mass% or less with respect to the total of 100 mass% of all elements included in the sintered body.

[0056] In the bonding phase used in the present embodiment, the first material S1 is composed of a compound including W, and the second material S2 is composed of a compound not including W but including V, and the ratio (S1 / (S1+S2)) of the content (vol%) of the above first material S1 to the total content (vol%) of the first material S1 and the second material S2 is preferably 0.35 or more and 1 or less. In the cubic boron nitride sintered body, by making (S1 / (S1+S2)) 0.35 or more, the toughness of the bonding phase is improved, so that the damage resistance tends to be excellent. From the same perspective, the above ratio (S1 / (S1+S2)) is more preferably 0.40 or more and 1 or less, further preferably 0.45 or more and 1 or less, and still further preferably 0.76 or more and 1 or less.

[0057] Among them, as the compound constituting the first material S1 and the second material S2, at least one selected from the group consisting of carbide, nitride, boride, oxide, and a solid solution thereof is preferably included, at least one selected from the group consisting of carbide, nitride, boride, and a solid solution thereof is more preferably included, and at least one selected from the group consisting of carbide, nitride, and a solid solution thereof is further preferably included.

[0058] In the binding phase used in the present embodiment, the total content (vol%) of the first material S1 and the second material S2 with respect to the total amount of the binding phase is preferably 35 vol% or more and 97 vol% or less. In the cubic boron nitride sintered body, by making the total content of the first material S1 and the second material S2 35 vol% or more, the toughness of the binding phase is improved, and the damage resistance tends to be excellent. In addition, in the cubic boron nitride sintered body, by making the total content 97 vol% or less, the production tends to be easy. From the same perspective, the total content of the first material S1 and the second material S2 is more preferably 45 vol% or more and 97 vol% or less, further preferably 50 vol% or more and 97 vol% or less, and still further preferably 74 vol% or more and 97 vol% or less.

[0059] Further, in the binding phase, in addition to the first material S1 and the second material S2, other materials can be contained, and the total content of the first material S1, the second material S2, and the other materials is 100 vol%. For example, when the total content of the first material S1 and the second material S2 is 35 vol%, the remaining 65 vol% is the other materials. The other materials are composed of any one or both of a metal and a compound that do not contain W and V.

[0060] The specific examples of the first material S1 composed of a compound containing W are not particularly limited, and for example, WC, Co3W3C, W2Co 21 B6, CoWB, W2C, WB, and the like, and WC is preferable. In addition, by increasing the ratio (S1 / (S1+S2)), the toughness of the binding phase is improved, and the damage resistance tends to be excellent, and therefore, as the first material S1 composed of a compound containing W, a material in which V is further solid-solved among the compounds listed as specific examples of the first material S1 is preferable. Further, the first material S1 other than the above is not particularly limited, and for example, VC, VN, V(C,N), VB in which W is solid-solved, and VC, VN, V(C,N) in which W is solid-solved are preferable.

[0061] In addition, the specific examples of the second material S2 composed of a compound containing V and not containing W are not particularly limited, and for example, VC, VN, V(C,N), VB, and the like are listed, and VC and VN are preferable.

[0062] Further, the specific examples of the other materials are not particularly limited, and for example, Al, AlN, AlB2, Al2O3, CrN, Cr2N, Cr3C2, Cr7C3, Cr 23 C6, Cr2O3, CrB2, TiN, TiC, Ti(C,N), TiB2, Co, Co 5.47 N, CoN, and the like, and Al2O3, Cr2N, Cr3C2, TiN, and Co are preferable.

[0063] In the cubic boron nitride sintered body of the present embodiment, the structure photograph of the cubic boron nitride sintered body taken by a scanning electron microscope (SEM) can be analyzed by using a commercially available image analysis software, and the contents (vol%) of the cubic boron nitride and the binder phase can be calculated. More specifically, the cubic boron nitride sintered body is mirror-polished in a direction orthogonal to the surface thereof. Then, the backscattered electron image of the mirror-polished surface of the cubic boron nitride sintered body after the mirror-polishing is observed using the SEM. At this time, the mirror-polished surface of the cubic boron nitride sintered body is observed on the SEM at a magnification of 1000 to 20000 times using the backscattered electron image. By using an energy dispersive X-ray analysis device (EDS) attached to the SEM, the black region can be determined as the cubic boron nitride, and the gray region and the white region can be determined as the binder phase. Thereafter, the structure photograph of the above-mentioned cross section of the cubic boron nitride is taken using the SEM. The obtained structure photograph is analyzed using a commercially available image analysis software, and the area occupancy of the cubic boron nitride and the binder phase is calculated, respectively, and the contents (vol%) thereof are calculated from the area occupancy.

[0064] In addition, in the present embodiment, in the same observation field of view as the structure photograph of the cubic boron nitride sintered body taken by a scanning electron microscope (SEM) for calculating the contents (vol%) of the cubic boron nitride and the binder phase, the contents (mass%) of each element in the binder phase can be calculated using an energy dispersive X-ray analysis device (EDS). More specifically, the EDS analysis is performed in the entire observation field of view of the above-mentioned mirror-polished surface at a magnification, and the content ratio (mass%) of each element when the total of all elements contained in the cubic boron nitride sintered body is 100 mass% is calculated.

[0065] Here, the mirror-polished surface of the cubic boron nitride sintered body is a cross section of the cubic boron nitride sintered body obtained by mirror-polishing the surface or an arbitrary cross section of the cubic boron nitride sintered body. As a method of obtaining the mirror-polished surface of the cubic boron nitride sintered body, for example, a method of polishing using a diamond polishing paste can be exemplified.

[0066] The composition of the binder phase can be identified using a commercially available X-ray diffractometer. For example, by using an X-ray diffractometer (product name "RINT TTRIII") manufactured by Rigaku Corporation, X-ray diffraction measurement using a 2θ / θ focusing method optical system of Cu-Kα rays is performed under the following conditions, and the composition of the binder phase can be identified. Here, the measurement conditions can be as follows:

[0067] <Example of Measurement Conditions>

[0068] • Output power: 50 kV, 250 mA;

[0069] • Incidence side slit: 5°;

[0070] • divergent longitudinal slit: 1 / 2°;

[0071] • divergent longitudinal limiting slit: 10 mm;

[0072] • divergent slit: 2 / 3°;

[0073] • light-receiving side shuttle slit: 5°;

[0074] • light-receiving slit: 0.15 mm;

[0075] • BENT monochromator;

[0076] • light-receiving monochromatic slit: 0.8 mm;

[0077] • sampling width: 0.02°;

[0078] • scanning speed: 1° / min;

[0079] • 2θ measurement range: 30-90°.

[0080] Further, in the present embodiment, the contents of cubic boron nitride and the bonding phase and the composition of the bonding phase can be measured by the method described in the Examples described later. Specifically, the composition of the bonding phase can be determined by analyzing the measurement results of the X-ray analysis device and the elemental mapping results using EDS.

[0081] [Coated cubic boron nitride sintered body]

[0082] The coated cubic boron nitride sintered body of the present embodiment includes the above-described cubic boron nitride sintered body and a coating layer formed on the surface of the cubic boron nitride sintered body.

[0083] By forming the coating layer on the surface of the cubic boron nitride sintered body, the wear resistance of the cubic boron nitride sintered body is further improved. Preferably, the coating layer includes at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, and Si and at least one element selected from the group consisting of C, N, O, and B. In addition, the coating layer can have a single layer structure, or a laminated structure including two or more layers. When the coating layer has such a structure, the wear resistance of the coated cubic boron nitride sintered body of the present embodiment is further improved.

[0084] Examples of the compound forming the coating layer are not particularly limited, and for example, TiN, TiC, TiCN, TiAlN, TiSiN, AlCrN, and the like can be listed. Among them, TiCN, TiAlN, and AlCrN are preferred. The coating layer can have a structure in which a plurality of layers having different compositions are laminated. In this case, the average thickness of each layer is, for example, preferably 0.3 μm or more and 4.5 μm or less.

[0085] The average thickness of the entire coating is preferably 0.5 μm or more and 5.0 μm or less. When the average thickness of the entire coating is 0.5 μm or more in the coated cubic boron nitride sintered body of the present embodiment, the wear resistance tends to be improved. On the other hand, when the average thickness of the entire coating is 5.0 μm or less, it tends to be possible to suppress breakage due to peeling. From the same perspective, the average thickness of the entire coating is more preferably 0.5 μm or more and 4.0 μm or less, and further preferably 1.0 μm or more and 3.0 μm or less.

[0086] The thickness of each layer constituting the coating and the thickness of the entire coating can be measured by observing the cross-sectional structure of the coated cubic boron nitride sintered body using an optical microscope, SEM, transmission electron microscope (TEM), or the like. Further, the thickness of each layer and the thickness of the entire coating can be measured from three or more cross sections in the vicinity of a position 50 μm from the center of the edge of the surface opposite to the metal evaporation source, and the average values thereof can be calculated to obtain the average thickness of each layer and the average thickness of the entire coating in the coated cubic boron nitride sintered body.

[0087] Further, the components of each layer constituting the coating can be measured by analyzing the cross-sectional structure of the coated cubic boron nitride sintered body using EDS or wavelength dispersive X-ray analysis device (WDS), or the like.

[0088] The method for producing the coating in the coated cubic boron nitride sintered body of the present embodiment is not particularly limited, and for example, chemical vapor deposition, physical vapor deposition such as ion plating, arc ion plating, sputtering, and ion mixing can be exemplified. Among them, arc ion plating is more preferable because it provides more excellent adhesion of the coating to the cubic boron nitride sintered body.

[0089] Since the cubic boron nitride sintered body or the coated cubic boron nitride sintered body of the present embodiment has excellent wear resistance and breakage resistance, it is preferably used as a cutting tool or a wear-resistant tool, and more preferably as a cutting tool. Further preferably, the cubic boron nitride sintered body or the coated cubic boron nitride sintered body of the present embodiment is used as a sintered metal-specific cutting tool or a cast iron-specific cutting tool. When the cubic boron nitride sintered body or the coated cubic boron nitride sintered body of the present embodiment is used as a cutting tool or a wear-resistant tool, the tool life can be extended compared to conventional ones.

[0090] The cubic boron nitride sintered body of the present embodiment can be produced, for example, by the following method.

[0091] cBN powder, Al powder, WC powder, VC powder, VN powder, Cr2N powder, Cr3C2 powder, TiN powder, and Co powder were prepared as raw material powders. Here, by appropriately adjusting the average particle diameter of the cBN powder in the raw material, the average particle diameter of the cBN in the cubic boron nitride sintered body obtained can be controlled to be within the above specific range. In addition, by appropriately adjusting the proportions of each of the raw material powders, the contents of the cBN and the bonding phase in the cubic boron nitride sintered body obtained can be controlled to be within the above specific ranges. Then, the prepared raw material powders were mixed with a superhard alloy ball, a solvent, and paraffin in a cylinder for a ball mill. The raw material powders mixed in the ball mill were filled into a high-melting-point metal capsule made of Ta, and vacuum heat treatment was performed in an opened state of the capsule to remove moisture and other adhering components adsorbed to the surfaces of the powders.

[0092] Then, the capsule was sealed, and the raw material powders filled in the capsule were sintered at high pressure. When filling the capsule, a base material made of superhard alloy was preferably placed on the bottom surface thereof. Thus, a cubic boron nitride sintered body having a base material made of superhard alloy can be produced, and the wear resistance and / or the breakage resistance of the tool tend to be further improved. As to the conditions for high-pressure sintering, for example, the pressure: 7.0 to 8.0 GPa, the temperature: 1900 to 2050°C, and the sintering time: 30 to 50 minutes.

[0093] In the bonding phase used in the present embodiment, the first material S1 is made of a compound containing W, and the second material S2 is made of a compound containing V but not containing W. The method of increasing the ratio (S1 / (S1+S2)) of the content (vol%) of the above first material S1 to the total content (vol%) of the first material S1 and the second material S2 is not particularly limited, and for example, the following methods can be listed: placing a base material made of superhard alloy in the capsule filled with the raw material powders in the preparation process of the cubic boron nitride sintered body; increasing the sintering temperature; decreasing the content ratio of cBN; increasing the average particle diameter of cBN; increasing the Al content; and decreasing the Cr content in the case of containing Cr, and the like.

[0094] In addition, the method of increasing the total content (vol%) of the above first material S1 and the above second material S2 is not particularly limited, and for example, the following methods can be listed: using a capsule in which a base material made of superhard alloy is placed as the capsule filled with the raw material powders in the preparation process of the cubic boron nitride sintered body; increasing the sintering temperature; decreasing the content ratio of cBN; increasing the average particle diameter of cBN; increasing the W content; and decreasing the Cr content in the case of containing Cr, and the like.

[0095] In addition, the cubic boron nitride sintered body of the present embodiment can be processed into a predetermined shape by a wire-cut electrical discharge machine or a laser cutting machine, or the like, and a cutting tool or a wear-resistant tool having the cubic boron nitride sintered body can be manufactured.

[0096] Examples

[0097] Hereinafter, the present application will be described in further detail by way of examples, but the present application is not limited to these examples.

[0098] (Example 1)

[0099] [Preparation of raw material powder]

[0100] Cubic boron nitride powder, Al powder, WC powder, VC powder, VN powder, Cr2N powder, Cr3C2 powder, TiN powder, and Co powder were mixed in the proportions shown in Table 1. The average particle diameters of the cBN powder, VC powder, and VN powder were as shown in Table 1. In addition, the average particle diameters of the Al powder, WC powder, Cr2N powder, Cr3C2 powder, TiN powder, and Co powder were 1.8 μm, 2.0 μm, 6.0 μm, 6.0 μm, 1.5 μm, and 1.5 μm, respectively. The average particle diameters of the raw material powders were measured by the Fisher Sub-Sieve Sizer (FSSS) method described in the American Society for Testing and Materials (ASTM) standard B330. Further, "-" in Table 1 indicates that there is no value in the column because the raw material corresponding to the column is not included.

[0101] Table 1

[0102]

[0103] [Mixing step]

[0104] The raw material powder, hexane solvent, paraffin, and superhard alloy ball were further mixed together in a cylinder for a ball mill.

[0105] [Loading step and drying step]

[0106] The mixed raw material powder was loaded into a disc-shaped capsule of a high-melting metal made of Ta. In addition, for Invention Nos. 3 to 5 and Comparative No. 1, a capsule having a substrate made of superhard alloy on the bottom surface was used, and for the other, a capsule not having a substrate made of superhard alloy was used. As the substrate made of superhard alloy, a material having 93.5 mass% of WC, 6.0 mass% of Co, and 0.5 mass% of Cr3C2 was used. Next, vacuum heat treatment was performed in a state where the capsule was open, and after removing moisture and other adhering components adsorbed on the surface of the powder, the capsule was sealed.

[0107] [High-pressure sintering]

[0108] Then, the raw material powder loaded in the capsule was subjected to high-pressure sintering. The conditions of the high-pressure sintering are shown in Table 2.

[0109] Table 2

[0110]

[0111] [Measurement and analysis]

[0112] As for the cubic boron nitride sintered body obtained by high-pressure sintering, the structure photograph of the cubic boron nitride sintered body taken by a scanning electron microscope (SEM) was analyzed by using a commercially available image analysis software, and the contents (volume %) of the cubic boron nitride and the binder phase were calculated. More specifically, the cubic boron nitride sintered body was mirror-polished in a direction orthogonal to the surface thereof. Then, the backscattered electron image of the mirror-polished surface of the cubic boron nitride sintered body after the mirror-polishing was observed using the SEM. At this time, the mirror-polished surface of the cubic boron nitride sintered body was observed using the backscattered electron image on the SEM, and the magnification was selected so as to contain 100 or more to 400 or less of the particles of the cubic boron nitride. By using an energy dispersive X-ray analysis device (EDS) attached to the SEM, the black regions were determined as the cubic boron nitride, and the gray regions and the white regions were determined as the binder phase. Thereafter, the structure photograph of the above mirror-polished surface of the cubic boron nitride was taken using the SEM. The obtained structure photograph was analyzed using the commercially available image analysis software, and the area occupied by the cubic boron nitride and the binder phase was calculated, respectively, and the contents (volume %) thereof were calculated from the area occupied thereby.

[0113] Here, the mirror-polished surface of the cubic boron nitride sintered body is a cross section of the cubic boron nitride sintered body obtained by mirror-polishing the surface or an arbitrary cross section of the cubic boron nitride sintered body. The method for obtaining the mirror-polished surface (hereinafter also referred to as "cross section") of the cubic boron nitride sintered body is polishing using a diamond polishing paste.

[0114] In addition, the composition of the binder phase was identified using an X-ray diffractometer (product name "RINT TTR III") manufactured by Rigaku Corporation, and specifically, the composition of the binder phase was identified by analyzing the results obtained by X-ray diffraction measurement using a 2θ / θ focusing method optical system using Cu-Kα rays under the following conditions, and the elemental mapping results using an EDS.

[0115] [Measurement conditions]

[0116] • Output power: 50 kV, 250 mA

[0117] • Incident side slit: 5°

[0118] • Divergence longitudinal slit: 1 / 2°

[0119] • Divergence longitudinal limiting slit: 10 mm

[0120] • Diffraction slit: 2 / 3°;

[0121] • Light-receiving side slit: 5°;

[0122] • Light-receiving slit: 0.15 mm;

[0123] • BENT monochromator;

[0124] • Light-receiving monochromatic slit: 0.8 mm;

[0125] • Sampling width: 0.02°;

[0126] • Scanning speed: 1° / min;

[0127] • 2θ measurement range: 30 to 90°.

[0128] Specifically, it was determined that the obtained cubic boron nitride sintered body contained the following materials by the X-ray diffraction measurement by the above-described method.

[0129] • Co3W3C, W2Co 21 B6 and Co 5.47 N

[0130] • WC (except for Inventive 3, Inventive 4, Inventive 5, and Comparative 1)

[0131] • VC (except for Comparative 12)

[0132] • VN (Inventive 2 and Inventive 3)

[0133] • TiN and TiB2(Inventive 21 and Comparative 12)

[0134] In addition, with respect to the compound containing the W element and / or the V element, it was determined or presumed that the obtained cubic boron nitride sintered body further contained the following materials by using the element mapping of the EDS.

[0135] • Presumed to be Co3W3C and W2Co 21 a material containing the V element in addition to the compound of B6 (except for Comparative 12)

[0136] • a material containing the V element in addition to the compound presumed to be WC (except for Inventive 3, Inventive 4, Inventive 5, Comparative 1, and Comparative 12)

[0137] • a material containing the W element in addition to the compound presumed to be VC (except for Comparative 12)

[0138] • a material containing the W element in addition to the compound presumed to be VN (Inventive 2 and Inventive 3)

[0139] In addition, as to the compound containing the Al element and the compound containing the Cr element, no clear peak was obtained in the X-ray diffraction measurement, and thus identification was performed by using the element mapping of the EDS. As a result, it was determined or presumed that the obtained cubic boron nitride sintered body further contained the following materials.

[0140] • AlN, AlB2, and Al203(except for Comparative Example 5)

[0141] • presumed to be Cr3C2, Cr7C3, and Cr 23 Cr carbides of C6, and materials in which these Cr carbides further contain the Co element (except for Inventive Example 12, Inventive Example 14, and Comparative Example 9)

[0142] • Cr nitrides presumed to be CrN and Cr2N, and materials in which these Cr nitrides further contain the Co element (except for Inventive Example 12, Inventive Example 14, Inventive Example 20, and Comparative Example 9)

[0143] • materials presumed to be Cr carbonitrides in which the above-described Cr carbides and Cr nitrides are mutually solid-solved (except for Inventive Example 12, Inventive Example 14, Inventive Example 20, and Comparative Example 9)

[0144] In the observation field of view in which the structure photograph for calculating the content ratio of the above-described cBN and the binder phase was obtained, element mapping using the EDS was performed, and the distribution of W and V was confirmed. From the mapping image obtained by image analysis, the area occupied by the first material S1 composed of a compound containing W, and the second material S2 composed of a compound not containing W but containing V was calculated, and the content (vol%) of each of S1 and S2 with respect to the entire content of the binder phase of 100 vol% was calculated. In Table 3, the ratio of the content of S1 to the total content of S1 and S2 (S1 / (S1+S2)) and the total content of S1 and S2 are shown.

[0145] In addition, by performing image analysis on the structure photograph of the cubic boron nitride sintered body photographed by the above-described SEM, the area of the cBN particle was calculated, and the diameter of a circle having an area equal to that of the cBN particle was taken as the particle diameter of the cBN. Next, the value satisfying the following formula was calculated as D 50 , which is the average particle diameter of the cBN in the cubic boron nitride sintered body. 50

[0146] (cBN particles having a particle diameter of D 50 (the area occupied by cBN particles having a particle diameter of D

[0147] Further, as described above, the cross section was observed using the SEM, and the composition of each element in the binder phase was calculated using the EDS attached to the SEM.

[0148] ​Further, in the same observation field of view as the structural photograph of the cubic boron nitride sintered body taken by the SEM for the purpose of finding the contents (vol.%) of the cubic boron nitride and the binder phase, the contents (mass%) of each element in the binder phase were found using the EDS. Specifically, the EDS analysis was performed in the entire observation field of view of the aforementioned magnified mirror-polished surface, and the content ratio (mass%) of each element when the total of all elements contained in the cubic boron nitride sintered body was 100 mass% was calculated.

[0149] These measurement results are shown together in Table 4.

[0150] Table 3

[0151]

[0152] Table 4

[0153]

[0154] [Manufacture of cutting tool]

[0155] The obtained cubic boron nitride sintered body was cut using a wire-cut electric discharge machining machine in accordance with the tool shape of the blade shape specified in ISO Standard CNGA120408. The cut cubic boron nitride sintered body was welded to a base metal composed of superhard alloy. At this time, in Inventive Examples 3 to 5 and Comparative Example 1, the obtained cubic boron nitride sintered body was welded to the base metal together with the aforementioned base material composed of superhard alloy. The welded tool was honed, thereby obtaining a cutting tool.

[0156] [Cutting test]

[0157] A cutting test was performed using the above-obtained cutting tool under the following conditions.

[0158] • Cut material: SMF5040 carburized and quenched metal (HRA 70);

[0159] • Cut material shape: gear shape, φ 45 mm (tooth height 8 mm) x 30 mm;

[0160] • Cutting speed: 150 m / min;

[0161] • Feed: 0.1 mm / rev;

[0162] • Cutting depth: 0.2 mm;

[0163] • Coolant: none (dry cutting process);

[0164] • Evaluation item: The machining time until the tool life was measured. The tool life was until the wear width of the flank face reached 0.15 mm or the cutting tool was broken. The damage morphology at the tool life was observed by SEM. The damage morphology "chipping" means that a small notch was generated, but the wear width of the flank face reached 0.15 mm before the cutting tool was broken. The measurement results are shown in Table 5.

[0165] Table 5

[0166]

[0167] From the results shown in Table 5, the cubic boron nitride sintered body in the application includes cubic boron nitride and a binder phase, the content of the cubic boron nitride is 81 vol% or more and 95 vol% or less with respect to the total amount of the sintered body, the content of the binder phase is 5 vol% or more and 19 vol% or less with respect to the total amount of the sintered body, the content of Al contained in the binder phase is 0.5 mass% or more and 5 mass% or less with respect to the total of 100 mass% of all elements contained in the sintered body, the content of W contained in the binder phase is 2 mass% or more and 10 mass% or less with respect to the total of 100 mass% of all elements contained in the sintered body, the content of V contained in the binder phase is 2 mass% or more and 8 mass% or less with respect to the total of 100 mass% of all elements contained in the sintered body, the content of Cr contained in the binder phase is 0 mass% or more and 5 mass% or less with respect to the total of 100 mass% of all elements contained in the sintered body, and the application has more excellent cutting performance and longer tool life compared to the comparative examples different from the application.

[0168] (Example 2)

[0169] Next, as shown in Table 6, after ion bombardment heat treatment was performed on the surface of the cubic boron nitride sintered body of the application 1, the application 4, the application 6, and the application 7 obtained in Example 1, a coating layer was formed by an arc ion plating method. In forming the first layer and the second layer, the surface of the cubic boron nitride sintered body was formed in the order described above. The treatment conditions thereof are shown below, respectively. In addition, the composition and the average thickness of the coating layer are shown in Table 6 below. Further, "-" in Table 6 indicates that the layer was not formed.

[0170] [Conditions of ion bombardment heat treatment]

[0171] Substrate temperature: 500°C;

[0172] Pressure: 2.7 Pa of Ar gas atmosphere;

[0173] Voltage: -400 V;

[0174] Current: 40 A;

[0175] Time: 30 minutes

[0176] [Coating formation conditions]

[0177] Substrate temperature: 500°C

[0178] Pressure: 3.0 Pa of nitrogen (N2) gas environment (nitride layer) or 3.0 Pa of a mixed gas environment of nitrogen (N2) gas and acetylene (C2H2) gas (carbonitride layer)

[0179] Voltage: -60 V

[0180] Current: 120 A

[0181] Table 6

[0182]

[0183] A coated cubic boron nitride sintered body having a coating formed on the surface was used to perform the same cutting test as in Example 1. The results are shown in Table 7 below.

[0184] Table 7

[0185]

[0186] As can be seen from the results shown in Table 7, the cubic boron nitride sintered body is more excellent in cutting performance and has a longer tool life if a coating is formed on the surface thereof.

[0187] Industrial Applicability

[0188] The cubic boron nitride sintered body of the present application has excellent wear resistance and breakage resistance, and can extend the tool life compared to the past, and is high in industrial availability in this respect.

Claims

1. A cubic boron nitride sintered body comprising cubic boron nitride and a binder phase, the content of the cubic boron nitride is 81 vol% or more and 95 vol% or less with respect to the total amount of the sintered body; the content of the binder phase is 5 vol% or more and 19 vol% or less with respect to the total amount of the sintered body; the content of Al contained in the binder phase is 0.5 mass% or more and 5 mass% or less with respect to the total of 100 mass% of all elements contained in the sintered body; the content of W contained in the binder phase is 2 mass% or more and 10 mass% or less with respect to the total of 100 mass% of all elements contained in the sintered body; the content of V contained in the binder phase is 2 mass% or more and 8 mass% or less with respect to the total of 100 mass% of all elements contained in the sintered body; the content of Cr contained in the binder phase is 0 mass% or more and 5 mass% or less with respect to the total of 100 mass% of all elements contained in the sintered body; wherein the binder phase comprises a first material S1 and a second material S2, the first material S1 is composed of a compound containing W, the second material S2 is composed of a compound containing V and not containing W, and the compounds constituting the first material S1 and the second material S2 include at least one selected from the group consisting of carbide, nitride, boride, oxide, and a solid solution thereof; wherein the ratio S1 / (S1+S2) of the volume percentage content of the first material S1 to the total volume percentage content of the first material S1 and the second material S2 is 0.35 or more and 1 or less.

2. The cubic boron nitride compact according to claim 1, wherein the total volume percentage content of the first material S1 and the second material S2 is 35 vol% or more and 97 vol% or less with respect to the total amount of the binder phase.

3. The cubic boron nitride compact according to claim 1 or 2, wherein the average particle diameter of the cubic boron nitride is 0.5 μm or more and 3.0 μm or less.

4. A coated cubic boron nitride sintered body comprising the cubic boron nitride sintered body according to claim 1 or 2, and a coating layer formed on the surface of the cubic boron nitride sintered body, the average thickness of the coating layer is 0.5 μm or more and 5.0 μm or less.

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