Cemented carbide and cutting tool

Abstract

This cemented carbide comprises: a first hard phase composed of a plurality of tungsten carbide particles; and a binder phase including cobalt. The total first hard phase and binder phase content of the cemented carbide is 80.0 vol% or more. The binder phase content of the cemented carbide is 5.0-21.0 vol%. The cobalt content of the binder phase is 50 mass% or more. The 50% cumulative particle diameter D50 of the binder phase is 0.10-0.30 μm on an area basis. The ratio D10 / D90 of the 10% cumulative particle diameter D10 to the 90% cumulative particle diameter D90 of the binder phase is 0.26-0.40 on an area basis. The vanadium content of the cemented carbide is 0.01-0.20 mass%. The chromium content of the cemented carbide is 0.01-1.00 mass%. The tungsten carbide particles include first tungsten carbide particles having a \{11-20\} crystal plane and second tungsten carbide particles present adjacent to the \{11-20\} crystal plane. In an interface region A between the \{11-20\} crystal plane of the first tungsten carbide particles and the second tungsten carbide particles, the ratio AV / ACo of the maximum value AV of the vanadium content to the maximum value ACo of the cobalt content is 0.01-0.5. In the interface region A, the ratio ACr / ACo of the maximum value ACr of the chromium content to the maximum value ACo of the cobalt content is 0.01-2.0. The tungsten carbide particles include third tungsten carbide particles having a {0001} crystal plane and fourth tungsten carbide particles present adjacent to the {0001} crystal plane. In an interface region C between the {0001} crystal plane of the third tungsten carbide particles and the fourth tungsten carbide particles, the ratio BV / BCo of the maximum value BV of the vanadium content to the maximum value BCo of the cobalt content is 0.01-1.2. In the interface region C, the ratio BCr / BCo of the maximum value BCr of the chromium content to the maximum value BCo of the cobalt content is 0.01-2.0.

Description

Carbide alloys and cutting tools

[0001] This disclosure relates to cemented carbide and cutting tools.

[0002] Conventionally, cemented carbide alloys comprising multiple tungsten carbide particles and a binder phase have been used as materials for cutting tools (Patent Document 1).

[0003] International Publication No. 2023 / 228328

[0004] The cemented carbide alloy of the present disclosure comprises a first hard phase consisting of a plurality of tungsten carbide particles and a cobalt-containing binder phase, wherein the total content of the first hard phase and the binder phase of the cemented carbide alloy is 80.0 volume% or more, the content of the binder phase of the cemented carbide alloy is 5.0 volume% or more and 21.0 volume% or less, the cobalt content of the binder phase is 50 mass% or more, the 50% cumulative particle size D50 of the binder phase based on area is 0.10 μm or more and 0.30 μm or less, and the ratio of the 10% cumulative particle size D10 of the binder phase based on area to the 90% cumulative particle size D90 is D The 10 / D90 ratio is 0.26 or more and 0.40 or less, the vanadium content of the cemented carbide is 0.01% by mass or more and 0.20% by mass or less, the chromium content of the cemented carbide is 0.01% by mass or more and 1.00% by mass or less, the tungsten carbide particles include first tungsten carbide particles having a {11-20} crystal plane and second tungsten carbide particles adjacent to the {11-20} crystal plane, and the maximum value A of the cobalt content is in the interface region A between the {11-20} crystal plane of the first tungsten carbide particles and the second tungsten carbide particles. Ｃｏ Maximum vanadium content A Ｖ Ratio A Ｖ / A Ｃｏ It is 0.01 or more and 0.5 or less, and in the interface region A, the maximum value A of the cobalt content Ｃｏ Maximum chromium content A Ｃｒ Ratio A Ｃｒ / A Ｃｏis 0.01 or more and 2.0 or less, and the tungsten carbide particles include a third tungsten carbide particle having a {0001} crystal plane and a fourth tungsten carbide particle existing adjacent to the {0001} crystal plane. In an interface region C between the {0001} crystal plane of the third tungsten carbide particle and the fourth tungsten carbide particle, a maximum value B of the cobalt content Ｃｏ with respect to a maximum value B of the vanadium content Ｖ ratio B Ｖ / B Ｃｏ is 0.01 or more and 1.2 or less, and in the interface region C, a maximum value B of the cobalt content Ｃｏ with respect to a maximum value B of the chromium content Ｃｒ ratio B Ｃｒ / B Ｃｏ is 0.01 or more and 2.0 or less, and it is a cemented carbide.

[0005] FIG. 1 is a diagram for explaining a measurement method of A Ｖ / A Ｃｏ and A Ｃｒ / A Ｃｏ in an interface region A. FIG. 2 is a schematic view of a cutting tool according to Embodiment 2.

[0006] [Problems to be Solved by the Present Disclosure] From the viewpoint of cost reduction, there is a demand for a cemented carbide that enables the tool to have a long life and a cutting tool including the same, even when used as a material for a cutting tool for rough machining of die steel.

[0007] [Effects of the Present Disclosure] According to the present disclosure, it is possible to provide a cemented carbide that enables the tool to have a long life and a cutting tool including the same, even when used as a material for a cutting tool for rough machining of die steel.

[0008] [Description of Embodiments of the Disclosure] First, embodiments of the Disclosure will be listed and described. (1) The cemented carbide of the Disclosure comprises a first hard phase consisting of a plurality of tungsten carbide particles and a cobalt-containing binder phase, wherein the total content of the first hard phase and the binder phase of the cemented carbide is 80.0 volume% or more, the content of the binder phase of the cemented carbide is 5.0 volume% or more and 21.0 volume% or less, the cobalt content of the binder phase is 50 mass% or more, the 50% cumulative particle size D50 of the binder phase based on area is 0.10 μm or more and 0.30 μm or less, and the ratio of the 10% cumulative particle size D10 of the binder phase based on area to the 90% cumulative particle size D90 is D The 10 / D90 ratio is 0.26 or more and 0.40 or less, the vanadium content of the cemented carbide is 0.01% by mass or more and 0.20% by mass or less, the chromium content of the cemented carbide is 0.01% by mass or more and 1.00% by mass or less, the tungsten carbide particles include first tungsten carbide particles having a {11-20} crystal plane and second tungsten carbide particles adjacent to the {11-20} crystal plane, and the maximum value A of the cobalt content is in the interface region A between the {11-20} crystal plane of the first tungsten carbide particles and the second tungsten carbide particles. Ｃｏ Maximum vanadium content A Ｖ Ratio A Ｖ / A Ｃｏ It is 0.01 or more and 0.5 or less, and in the interface region A, the maximum value A of the cobalt content Ｃｏ Maximum chromium content A Ｃｒ Ratio A Ｃｒ / A Ｃｏ The cobalt content is 0.01 or more and 2.0 or less, and the tungsten carbide particles include a third tungsten carbide particle having a {0001} crystal plane and a fourth tungsten carbide particle adjacent to the {0001} crystal plane, and the maximum value B of the cobalt content is in the interface region C between the {0001} crystal plane of the third tungsten carbide particle and the fourth tungsten carbide particle. Ｃｏ The maximum vanadium content B Ｖ Ratio B Ｖ / B ＣｏThe cobalt content is between 0.01 and 1.2, and in the interface region C, the maximum value B of the cobalt content is Ｃｏ The maximum value of chromium content B Ｃｒ Ratio B Ｃｒ / B Ｃｏ It is a cemented carbide alloy with a coefficient of 0.01 or higher and a coefficient of 2.0 or lower.

[0009] In the crystallographic descriptions in this disclosure, individual orientations are indicated by [], collective orientations by <>, individual planes by (), and collective planes by {}. Furthermore, while negative crystallographic exponents are usually indicated by placing a "-" (bar) above the number, in this disclosure, the negative sign is placed before the number.

[0010] According to this disclosure, it is possible to provide a cemented carbide that enables longer tool life, especially when used as a material for cutting tools used for rough machining of die steel. The reason for this is presumed to be as follows.

[0011] The cemented carbide alloy of this disclosure contains a first hard phase consisting of tungsten carbide particles and a cobalt-containing binder phase in a total volume of 80.0% or more, the binder phase content of the cemented carbide alloy is 5.0% to 21.0% by volume, and the cobalt content of the binder phase is 50% by mass or more. As a result, the cemented carbide alloy can have hardness and toughness suitable for cutting tools.

[0012] In the cemented carbide alloy of this disclosure, the D50 of the bonding phase is 0.10 μm or more and 0.30 μm or less, and the D10 / D90 of the bonding phase is 0.26 or more and 0.40 or less. As a result, in the cemented carbide alloy, the fine bonding phase is uniformly dispersed without localizing, and the cemented carbide alloy structure tends to be homogeneous. Therefore, a cutting tool equipped with a cutting edge made of this cemented carbide alloy can have stable chipping resistance.

[0013] The vanadium content of the cemented carbide alloy disclosed herein is 0.01% by mass or more and 0.20% by mass or less. Vanadium has the effect of suppressing the grain growth of tungsten carbide particles. When the vanadium content of the cemented carbide alloy is 0.01% by mass or more, the occurrence of coarse grains in the cemented carbide alloy can be effectively suppressed. When the vanadium content of the cemented carbide alloy is 0.20% by mass or less, a vanadium-enriched layer, in which vanadium is concentrated in the interface region between WC particles, is less likely to form, and the decrease in interface strength is easily suppressed. Therefore, the hardness and strength of the cemented carbide alloy are improved, and the wear resistance and fracture resistance of cutting tools equipped with an edge made of the cemented carbide alloy are improved.

[0014] The chromium content of the cemented carbide alloy disclosed herein is 0.01% by mass or more and 1.00% by mass or less. Chromium has the effect of suppressing grain growth of tungsten carbide particles. When the chromium content of the cemented carbide alloy is 0.01% by mass or more, the occurrence of coarse grains in the cemented carbide alloy can be effectively suppressed. When the chromium content of the cemented carbide alloy is 1.00% by mass or less, a chromium-enriched layer, in which chromium is concentrated in the interface region between WC particles, is less likely to form, and the reduction in interface strength is easily suppressed. Therefore, the hardness and strength of the cemented carbide alloy are improved, and the wear resistance and fracture resistance of cutting tools equipped with an edge made of the cemented carbide alloy are improved.

[0015] In the interface region A of the cemented carbide alloy disclosed herein, Ｖ / A Ｃｏ is 0.01 or more and 0.5 or less, and A Ｃｒ / A Ｃｏ It is between 0.01 and 2.0. Furthermore, in the interface region C of the cemented carbide of this disclosure, B Ｖ / B Ｃｏ is 0.01 or more and 1.2 or less, and B Ｃｒ / B Ｃｏ This value is between 0.01 and 2.0. According to this, the formation of vanadium-enriched layers and chromium-enriched layers is suppressed in interface region A and interface region C. Therefore, the decrease in interfacial strength between WC particles caused by the vanadium-enriched and chromium-enriched layers is suppressed. Thus, in this cemented carbide, detachment of WC particles due to a decrease in interfacial strength is less likely to occur, and the occurrence of wear starting from chipping is suppressed in cutting tools equipped with an edge made of this cemented carbide.

[0016] (2) In the above (1), A Ｖ / A Ｃｏ is 0.01 or more and 0.3 or less, and A Ｃｒ / A Ｃｏ is 0.01 or more and 1.5 or less, and the above B Ｖ / B Ｃｏ is 0.4 or more and 1.2 or less, and the above B Ｃｒ / B Ｃｏ It may be between 0.5 and 2.0.

[0017] A Ｖ / A Ｃｏ and A Ｃｒ / A Ｃｏ When the above range is maintained, the formation of vanadium-enriched and chromium-enriched layers in interface region A is further suppressed. As a result, the decrease in interfacial strength between WC particles caused by the vanadium-enriched and chromium-enriched layers is further suppressed. Therefore, in cutting tools equipped with cutting edges made of cemented carbide, the occurrence of wear starting from chipping is further suppressed.

[0018] In interface region C, V and Cr are usually more likely to be concentrated than in interface region A, but B Ｖ / B Ｃｏ and B Ｃｒ / B Ｃｏ When the above range is maintained, the formation of vanadium-enriched and chromium-enriched layers in the interface region C is further suppressed. As a result, the decrease in interfacial strength between WC particles caused by the vanadium-enriched and chromium-enriched layers is further suppressed. Therefore, in cutting tools equipped with an edge made of cemented carbide, the occurrence of wear starting from chipping is further suppressed.

[0019] (3) In (1) or (2) above, the cemented carbide further comprises a second hard phase, the second hard phase consisting of at least one first compound selected from the group consisting of TiNbC, TiNbN, and TiNbCN, and the 50% cumulative particle size D50 of the second hard phase based on area may be 0.003 μm or more and 0.05 μm or less. This further improves the hardness of the cemented carbide. Therefore, a cutting tool equipped with a cutting edge made of the cemented carbide can have even better wear resistance.

[0020] (4) In any of (1) to (3) above, the mode of the particle size distribution of the tungsten carbide particles based on area may be 0.2 μm or more and 0.8 μm or less. This further improves the hardness of the cemented carbide. Therefore, a cutting tool equipped with a cutting edge made of the cemented carbide can have even better wear resistance.

[0021] (5) The cutting tool of this disclosure is a cutting tool having an cutting edge made of a cemented carbide as described in any of (1) to (4) above. The cutting tool of this disclosure can have a long life, especially when used for rough machining of die steel.

[0022] [Details of Embodiments of the Disclosure] Specific examples of cemented carbide and cutting tools of the Disclosure will be described below with reference to the drawings. In the drawings of the Disclosure, the same reference numerals indicate the same or equivalent part. In addition, dimensional relationships such as length, width, thickness, and depth have been modified as appropriate for clarity and simplification of the drawings and do not necessarily represent actual dimensional relationships.

[0023] In this disclosure, the notation "A to B" means A or greater and B or less. If no unit is specified for A, and only a unit is specified for B, then the unit for A and the unit for B are the same.

[0024] In this disclosure, when compounds and the like are represented by chemical formulas, unless otherwise specified, the atomic ratios should include all conventionally known atomic ratios and should not necessarily be limited to those within the stoichiometric range.

[0025] In this disclosure, if one or more numerical values ​​are listed as the lower and upper limits of a numerical range, any combination of any one numerical value listed as the lower limit and any one numerical value listed as the upper limit shall also be disclosed.

[0026] In this disclosure, “equipment,” “includes,” “possesses,” and variations thereof are open-ended terms. Open-ended terms may or may not include additional elements in addition to the essential elements. The statement “consists of” is a closed term. However, even a configuration expressed in closed terms may include additional elements that are usually incidental or irrelevant to the subject technology.

[0027] [Embodiment 1: Carbide Alloy] The carbide alloy of one embodiment of the present disclosure (hereinafter also referred to as "Embodiment 1") is a carbide alloy comprising a first hard phase consisting of a plurality of tungsten carbide particles and a binder phase containing cobalt. The total content of the first hard phase and the binder phase of the carbide alloy is 80.0 volume% or more. The content of the binder phase of the carbide alloy is 5.0 volume% or more and 21.0 volume% or less. The cobalt content of the binder phase is 50 mass% or more. The 50% cumulative particle size D50 of the binder phase based on area is 0.10 μm or more and 0.30 μm or less. The ratio D10 / D90 of the 10% cumulative particle size D10 to the 90% cumulative particle size D90 of the binder phase based on area is 0.26 or more and 0.40 or less. The vanadium content of the carbide alloy is 0.01 mass% or more and 0.20 mass% or less. The chromium content of the cemented carbide is 0.01% by mass or more and 1.00% by mass or less. The tungsten carbide particles include first tungsten carbide particles having a {11-20} crystal plane and second tungsten carbide particles adjacent to the {11-20} crystal plane. At the interface region A between the {11-20} crystal plane of the first tungsten carbide particles and the second tungsten carbide particles, the maximum value A of the cobalt content is Ｃｏ Maximum vanadium content A Ｖ Ratio A Ｖ / A Ｃｏ It is between 0.01 and 0.5. In interface region A, the maximum value of cobalt content A Ｃｏ Maximum chromium content A Ｃｒ Ratio A Ｃｒ / A ＣｏThe cobalt content is between 0.01 and 2.0. The tungsten carbide particles include third tungsten carbide particles having a {0001} crystal plane and fourth tungsten carbide particles adjacent to the {0001} crystal plane. At the interface region C between the {0001} crystal plane of the third tungsten carbide particle and the fourth tungsten carbide particle, the maximum value B of the cobalt content is Ｃｏ The maximum vanadium content B Ｖ Ratio B Ｖ / B Ｃｏ The value is between 0.01 and 1.2. In the interface region C, the maximum value of cobalt content B Ｃｏ The maximum value of chromium content B Ｃｒ Ratio B Ｃｒ / B Ｃｏ The value is between 0.01 and 2.0.

[0028] <Composition of the cemented carbide> The cemented carbide of Embodiment 1 comprises a first hard phase consisting of tungsten carbide particles and a binder phase containing cobalt. The total content of the first hard phase and the binder phase of the cemented carbide is 80.0 volume% or more, may be 81.3 volume% to 100 volume%, 92 volume% to 100 volume%, 90 volume% to 99 volume%, 92 volume% to 98 volume%, or 94 volume% to 97 volume%.

[0029] The binder phase content of the cemented carbide in Embodiment 1 is 5.0 volume% or more and 21.0 volume% or less, and may be 7 volume% or more and 20 volume% or less, or 10 volume% or more and 18 volume% or less.

[0030] The cemented carbide of Embodiment 1 may contain a second hard phase in addition to the first hard phase and the binder phase. The second hard phase consists of at least one first compound selected from the group consisting of TiNbC, TiNbN, and TiNbCN. The content of the second hard phase in the cemented carbide may be greater than 0 vol% and 20 vol% or less, greater than 0 vol% and 18.7 vol% or less, greater than 0 vol% and 10 vol% or less, or 1 vol% to 5 vol%.

[0031] The cemented carbide of Embodiment 1 may consist of a first hard phase and a binder phase. To the extent that the effects of this disclosure are not impaired, the cemented carbide of Embodiment 1 may consist of a first hard phase, a binder phase and impurities. The cemented carbide of Embodiment 1 may consist of a first hard phase, a binder phase and a second hard phase. To the extent that the effects of this disclosure are not impaired, the cemented carbide of Embodiment 1 may consist of a first hard phase, a binder phase, a second hard phase and impurities.

[0032] Examples of the impurities mentioned above include iron (Fe), calcium (Ca), silicon (Si), and sulfur (S). The impurity content of the cemented carbide is acceptable as long as it does not impair the effects of this disclosure. For example, the impurity content of the cemented carbide may be 0% by mass or more and less than 0.1% by mass. The impurity content of the cemented carbide is measured by ICP emission spectrometry (Inductively Coupled Plasma Emission Spectroscopy). The measuring instrument can be the "ICPS-8100" (trademark) manufactured by Shimadzu Corporation.

[0033] The method for measuring the content of the first hard phase, the binder phase, and the second hard phase of cemented carbide is as follows: (A1) Cut out a section of cemented carbide at an arbitrary location to expose the cross-section. Polish the cross-section to a mirror finish using a cross-section polisher (manufactured by JEOL Ltd.).

[0034] (B1) The mirror-finished surface of the cemented carbide is photographed with a scanning electron microscope (SEM) to obtain a backscattered electron image. The imaging area is set to the central part of the cross-section of the cemented carbide, that is, a position that does not include parts with properties clearly different from the bulk portion, such as near the surface of the cemented carbide (a position where the entire imaging area is the bulk portion of the cemented carbide). The observation magnification is 5000x. The measurement conditions are an acceleration voltage of 3kV, a current of 2nA, and a working distance (WD) of 5mm.

[0035] (C1) The backscattered electron image obtained in (B1) above is imported into a computer and binarized using image analysis software (OpenCV, SciPy). In the image after binarization, the first region consisting of the first hard phase and the second region consisting of the bonded phase and the second hard phase can be distinguished by the intensity of the colors. For example, in the image after binarization, the first hard phase is shown as a black region, and the bonded phase and the second hard phase are shown as white regions.

[0036] (D1) The imaging area described in (B1) above is analyzed using an energy-dispersive X-ray spectrometer (SEM-EDX) attached to the scanning electron microscope (instrument: Carl Zeiss Gemini 450™) to obtain an elemental mapping image.

[0037] (E1) By superimposing the binarized image obtained in (C1) above with the elemental mapping image obtained in (D1) above, the regions where the first hard phase, the bonded phase, and the second hard phase exist are identified on the binarized image. Regions shown in black in the binarized image and where tungsten (W) and carbon (C) exist in the elemental mapping image correspond to the regions where the first hard phase exists. Regions shown in white in the binarized image and where cobalt (Co) exists in the elemental mapping image correspond to the regions where the bonded phase exists. Regions shown in white in the binarized image and where titanium (Ti) or niobium (Nb) exists in the elemental mapping image correspond to the regions where the second hard phase exists.

[0038] (F1) A rectangular measurement field of view of 24.9 μm × 18.8 μm is set in the binarized image. Using the image analysis software described above, the area percentages of the first hard phase, the binding phase, and the second hard phase are measured, with the total area of ​​the measurement field of view as the denominator.

[0039] (G1) The measurement described in (F1) above is performed in five distinct, non-overlapping measurement fields. In this disclosure, the average area percentage of the first hard phase in the five measurement fields corresponds to the content (volume %) of the first hard phase in the cemented carbide. The average area percentage of the binder phase in the five measurement fields corresponds to the content (volume %) of the binder phase in the cemented carbide. The average area percentage of the second hard phase in the five measurement fields corresponds to the content (volume %) of the second hard phase in the cemented carbide.

[0040] It has been confirmed that, as long as the measurement is performed on the same sample, there is almost no variation in the measurement results even if the above measurement is performed multiple times by changing the selected area of ​​the measurement field.

[0041] <First Hard Phase> <Composition of the First Hard Phase> In the cemented carbide of Embodiment 1, the first hard phase consists of a plurality of tungsten carbide particles (hereinafter also referred to as "WC particles"). The tungsten carbide particles include not only "pure WC particles (WC that do not contain any impurity elements, and WC in which the content of impurity elements is below the detection limit)" but also "WC particles that contain impurities internally, as long as the effects of this disclosure are not impaired." Examples of impurities include iron (Fe), molybdenum (Mo), and sulfur (S).

[0042] <Mode in the area-based particle size distribution of tungsten carbide particles> In the cemented carbide of Embodiment 1, the mode in the area-based particle size distribution of tungsten carbide particles may be 0.2 μm or more and 0.8 μm or less, 0.21 μm or more and 0.75 μm or less, 0.3 μm or more and 0.7 μm or less, or 0.4 μm or more and 0.6 μm or less.

[0043] In this disclosure, the method for measuring the mode of the area-based particle size distribution of tungsten carbide particles in cemented carbide is as follows:

[0044] (A2) Using the same method as (A1) to (E1) for measuring the content of the first hard phase, the binder phase, and the second hard phase of the cemented carbide described above, the region where the first hard phase exists is identified in the binarized image.

[0045] (B2) Prepare five binarized images in which the region of the first hard phase is identified, and set a rectangular measurement field of view of 40.3 μm vertically × 30.2 μm horizontally in each image. Use image analysis software (ImageJ ver. 1.51J8) to identify the outer edge of each tungsten carbide particle in the measurement field of view and measure the area of ​​each tungsten carbide particle.

[0046] (C2) Based on all tungsten carbide particles in the five measurement fields, the mode of the area-based particle size distribution of tungsten carbide particles is measured. In this disclosure, the mode of the area-based particle size distribution of tungsten carbide particles measured above corresponds to the mode of the area-based particle size distribution of tungsten carbide particles in cemented carbide.

[0047] It has been confirmed that, as long as the measurement is performed on the same sample, there is almost no variation in the measurement results even if the above measurement is performed multiple times by changing the selected area of ​​the measurement field.

[0048] <Bonding Phase> <Composition of Bonding Phase> In the cemented carbide of Embodiment 1, the cobalt content of the bonding phase is 50% by mass or more. This allows the cemented carbide to have excellent toughness. The cobalt content of the bonding phase may be 80% by mass or more and 100% by mass or less, or 90% by mass or more and 100% by mass or less.

[0049] The method for measuring the cobalt content of the binder phase is as follows: An elemental mapping image and a binarized image are acquired in the same manner as (A1) to (E1) of the above-described methods for measuring the content of the first hard phase, the binder phase, and the second hard phase of the cemented carbide. By superimposing the elemental mapping image and the binarized image, the region where the binder phase exists is identified in the elemental mapping image. A rectangular measurement field of view of 24.9 μm × 18.8 μm is set in the elemental mapping image. The cobalt content is measured in the region where the binder phase exists within the measurement field of view. The above measurement is performed in five different measurement fields that do not overlap with each other. In this disclosure, the average of the cobalt content in the region where the binder phase exists in the five measurement fields of view corresponds to the cobalt content of the binder phase.

[0050] It has been confirmed that, as long as the measurement is performed on the same sample, there is almost no variation in the measurement results even if the above measurement is performed multiple times by changing the selected area of ​​the measurement field.

[0051] In the cemented carbide of Embodiment 1, the binder phase may further contain at least one first element selected from the group consisting of silicon, germanium, rhenium, and ruthenium. This improves the deformation resistance of the binder phase. The binder phase can consist of cobalt and the first element.

[0052] In the cemented carbide of Embodiment 1, the binder phase may include, in addition to cobalt and the first element, at least one second element selected from the group consisting of iron, nickel, and chromium. The binder phase may consist of cobalt, the first element, and the second element.

[0053] ≪D50 and D10 / D90 of the Binder Phase≫ In the cemented carbide of Embodiment 1, the 50% cumulative particle size D50 of the binder phase based on area (hereinafter also referred to as "D50 of the binder phase") is 0.10 μm or more and 0.30 μm or less, and may be 0.11 μm or more and 0.28 μm or less, or 0.12 μm or more and 0.20 μm or less.

[0054] In the cemented carbide of Embodiment 1, the ratio D10 / D90 (hereinafter also referred to as "D10 / D90 of the binder phase") of the 10% cumulative particle size D10 to the 90% cumulative particle size D90 based on the area of ​​the binder phase is 0.26 or more and 0.40 or less, and may be 0.27 or more and 0.38 or less, or 0.30 or more and 0.35 or less. The above D50 and D10 / D90 can be combined as appropriate.

[0055] In this disclosure, the methods for measuring the D50 and D10 / D90 of the bonding phase in cemented carbide are as follows.

[0056] (A3) Using the same method as (A1) to (E1) for measuring the content of the first hard phase, the content of the binder phase, and the content of the second hard phase of the cemented carbide described above, the region where the binder phase exists is identified in the binarized image.

[0057] (B3) Prepare five binarized images in which the region of the bonded phase has been identified, and set a rectangular measurement field of view of 40.3 μm vertically × 30.2 μm horizontally in each image. Use image analysis software (ImageJ ver. 1.51J8) to identify the outer edge of each bonded phase in the measurement field of view and measure the area of ​​each bonded phase.

[0058] (C3) Based on all the bonding phases in the five measurement fields, the D50 of the bonding phase and the ratio D10 / D90 of the bonding phase to D10 are measured. In this disclosure, the D50 of the bonding phase and the D10 / D90 of the bonding phase measured above correspond to the D50 of the bonding phase and the D10 / D90 of the bonding phase in cemented carbide, respectively.

[0059] It has been confirmed that, as long as the measurement is performed on the same sample, there is almost no variation in the measurement results even if the above measurement is performed multiple times by changing the selected area of ​​the measurement field.

[0060] <Second Hard Phase> <Composition> In Embodiment 1, the second hard phase consists of at least one first compound selected from the group consisting of TiNbC, TiNbN, and TiNbCN. In this disclosure, each of TiNbC, TiNbN, and TiNbCN is not limited to the case where the ratio of the total number of Ti and Nb atoms to the total number of C and N atoms is 1:1, and may include conventionally known ratios as long as they do not impair the effects of this disclosure.

[0061] The second hard phase may contain metallic elements such as tungsten (W), chromium (Cr), and cobalt (Co) to the extent that it does not impair the effects of the present disclosure. The total content of W, Cr, and Co in the second hard phase may be 0% by mass or more and less than 0.1% by mass. The content of W, Cr, and Co in the second hard phase is measured by STEM-EDX.

[0062] The method for measuring the composition of the second hard phase is as follows: (A4) A sample with a thickness of 30 nm to 100 nm is prepared by thinning an ion slicer (device: IB09060CIS™ manufactured by JEOL Ltd.) at an arbitrary position on the cemented carbide. The acceleration voltage of the ion slicer is 6 kV for thinning and 2 kV for finishing.

[0063] (B4) The above sample is observed at 50,000x magnification using a scanning transmission electron microscope (STEM) (JFM-ARM300F™ manufactured by JEOL Ltd.) to obtain a STEM-HAADF (HAADF: high-angle angular dark field) image. The imaging area for the STEM-HAADF image is set to the central part of the sample, that is, a position that does not include parts that clearly have different properties from the bulk portion, such as the vicinity of the surface of the cemented carbide (a position where the entire imaging area is the bulk portion of the cemented carbide). The measurement condition is an acceleration voltage of 200 kV.

[0064] (C4) Next, elemental mapping analysis is performed on the STEM-HAADF image using the EDX attached to the STEM to obtain an elemental mapping image. In the elemental mapping image, the region containing titanium (Ti) and niobium (Nb), and one or both of carbon (C) and nitrogen (N) is identified as the second hard phase, and the composition of the second hard phase is determined.

[0065] It has been confirmed that, as long as the measurement is performed on the same sample, there is almost no variation in the measurement results even if the above measurement is performed multiple times by changing the selected area of ​​the measurement field.

[0066] ≪50% cumulative particle size D50 based on area of ​​the second hard phase≫ In the cross-section of the cemented carbide of Embodiment 1, the 50% cumulative particle size D50 based on the area of ​​the second hard phase may be 0.003 μm or more and 0.05 μm or less, or 0.008 μm or more and 0.02 μm or less.

[0067] In this disclosure, the 50% cumulative grain size D50 of the second hard phase of the cemented carbide alloy, based on area (hereinafter also referred to as "D50 of the second hard phase"), is measured using the same method as the measurement method for the D50 of the bonding phase of the cemented carbide alloy, except that the region where the second hard phase exists is identified in place of the bonding phase in the image after binarization. It has been confirmed that, as long as the measurement is performed on the same sample, there is almost no variation in the measurement results even if the above measurement is performed multiple times by changing the selected area of ​​the measurement field.

[0068] <Vanadium content> The vanadium content of the cemented carbide of Embodiment 1 is 0.01% by mass or more and 0.20% by mass or less, may be 0.02% by mass or more and 0.19% by mass or less, or may be 0.05% by mass or more and 0.15% by mass or less. The vanadium content of the cemented carbide is measured by ICP emission spectrometry.

[0069] <Chromium content> The chromium content of the cemented carbide of Embodiment 1 is 0.01% by mass or more and 1.00% by mass or less, may be 0.02% by mass or more and 0.99% by mass or less, or may be 0.05% by mass or more and 0.95% by mass or less. The chromium content of the cemented carbide is measured by ICP emission spectrometry.

[0070] <In the interface region A, A Ｖ / A Ｃｏ and A Ｃｒ / A Ｃｏ > The tungsten carbide particles of the cemented carbide of Embodiment 1 include first tungsten carbide particles having a {11 - 20} crystal plane and second tungsten carbide particles existing adjacent to the {11 - 20} crystal plane. In the interface region A between the {11 - 20} crystal plane of the first tungsten carbide particles and the second tungsten carbide particles, the ratio A Ｃｏ of the maximum value A Ｖ of the vanadium content to the maximum value A Ｖ of the cobalt content is 0.01 or more and 0.5 or less, may be 0.01 or more and 0.45 or less, may be 0.01 or more and 0.3 or less, or may be 0.01 or more and 0.2 or less.

[0071] In the interface region A, the ratio A Ｃｏ of the maximum value A Ｃｒ of the chromium content to the maximum value A Ｃｒ of the cobalt content is 0.01 or more and 2.0 or less, may be 0.01 or more and 1.7 or less, may be 0.01 or more and 1.5 or less, or may be 0.01 or more and 0.9 or less. The above A Ｖ / A Ｃｏ and A Ｃｒ / A Ｃｏ can be combined as appropriate. <00003j9>​​​​

[0072] A in interface region A Ｖ / A Ｃｏ and A Ｃｒ / A Ｃｏ The measurement method is as follows: (A5) A thin sample with a thickness of 50 nm or less is cut from the cemented carbide using an ion slicer or the like. The surface of the thin sample is polished to a mirror finish. Examples of methods for mirror polishing include polishing with diamond paste, using a focused ion beam (FIB) device, using a cross-section polisher (CP) device, and methods combining these.

[0073] (B5) The mirror-finished surface of the thin section sample is observed with a scanning transmission electron microscope (STEM) (JFM-ARM300F™ manufactured by JEOL Ltd.) to obtain an electron diffraction pattern of WC particles. The observation magnification is 2 million times, and the pixel size is 256 × 256.

[0074] (C5) In the electron diffraction pattern, the {11-20} crystal plane of the WC particle is identified. The first WC particle, whose {11-20} crystal plane has been identified, is observed from the {11-20} orientation, and a second WC particle adjacent to the {11-20} crystal plane of the first WC particle is identified.

[0075] The crystal plane of the second WC particle adjacent to the {11-20} crystal plane of the first WC particle is not particularly limited as long as it is a crystal plane of the WC particle, for example it may be the {01-12} plane, the {0001} plane, the {11-20} plane, or the {10-10} plane.

[0076] Line analysis is performed on the interface region A between the {11-20} crystal plane of the first WC particle and the second WC particle using EDX (energy-dispersive X-ray spectroscopy) with a TEM. In the line analysis, the percentages of W (Tungsten), Cobalt (Co), Chromium (Cr), and Vanadium (V) are measured, with the total number of atoms of each element being set to 100 atomic percent.

[0077] The specific procedure of line analysis will be described with reference to FIG. 1. FIG. 1 schematically shows an electron diffraction image obtained by observing a thin-film sample with a TEM. In FIG. 1, the measurement region R of the line analysis is a rectangular region indicated by the symbol R.

[0078] As shown in FIG. 1, among the interfaces between the {11-20} crystal plane of the first WC particle 1 and the second WC particle 2 existing adjacent to the {11-20} crystal plane of the first WC particle 1, a substantially straight line portion that is substantially straight and has a length of 25 nm or more is selected. The line analysis is performed in a direction perpendicular to the substantially straight line portion (the direction of arrow B in FIG. 1). The distance of the line analysis is 20 nm on each of the first WC particle 1 side and the second WC particle 2 side with the substantially straight line portion as the center. The width of the line analysis is 25 nm, and the step interval is 0.4 nm. As shown in FIG. 1, the measurement region R of the line analysis is set so as not to include the binder phase 3.

[0079] Based on the line analysis results, the maximum value A of the cobalt content rate, Ｃｏ the maximum value A of the vanadium content rate, Ｖ and the maximum value A of the chromium content rate Ｃｒ in the measurement region R are specified, and A Ｖ / A Ｃｏ and A Ｃｒ / A Ｃｏ are calculated.

[0080] (D5) The measurement in (C5) above is performed in the interface region A between the {11-20} crystal plane of five different first WC particles and the second WC particle. The average value of A Ｖ / A Ｃｏ in the five interface regions A is calculated. This average value corresponds to A Ｖ / A Ｃｏ in the interface region A of the cemented carbide of the present disclosure. The average value of A Ｃｒ / A Ｃｏ in the five interface regions is calculated. This average value corresponds to A Ｃｒ / A Ｃｏ in the interface region A of the cemented carbide of the present disclosure.

[0081] It has been confirmed that, as long as the measurements are performed on the same sample, there is almost no variation in the measurement results even when the above measurement is performed multiple times by changing the selected measurement area and the interface area of ​​the object being measured.

[0082] Ｖ / B Ｃｏ and B Ｃｒ / B Ｃｏ > The tungsten carbide particles of the cemented carbide of Embodiment 1 include a third tungsten carbide particle having a {0001} crystal plane and a fourth tungsten carbide particle adjacent to the {0001} crystal plane. In the interface region C between the {0001} crystal plane of the third tungsten carbide particle and the fourth tungsten carbide particle, the maximum value B of the cobalt content is Ｃｏ The maximum vanadium content B Ｖ Ratio B Ｖ / B Ｃｏ It is between 0.01 and 1.2, and may also be between 0.35 and 1.2, between 0.4 and 1.2, or between 0.4 and 1.1.

[0083] In interface region C, the maximum value B of the cobalt content Ｃｏ The maximum value of chromium content B Ｃｒ Ratio B Ｃｒ / B Ｃｏ is 0.01 or more and 2.0 or less, and may be 0.5 or more and 2.0 or less, or 0.5 or more and 1.98 or less, or 1.32 or more and 1.98 or less. B above Ｖ / B Ｃｏ and B Ｃｒ / B Ｃｏ These can be combined as appropriate.

[0084] B in interface region C Ｖ / B Ｃｏ and B Ｃｒ / B Ｃｏ The measurement method is as follows: A in the above interface region A Ｖ / A Ｃｏ and A Ｃｒ / A ＣｏAn electron diffraction pattern of the WC particle is obtained using the same method as (A5) and (B5) of the measurement method. The {0001} crystal plane of the WC particle is identified in the electron diffraction pattern. The {0001} crystal plane of the third WC particle and the fourth WC particle adjacent to the {0001} crystal plane of the third WC particle are identified when observed from the {0001} orientation.

[0085] The crystal plane of the fourth WC particle adjacent to the {0001} crystal plane of the third WC particle is not particularly limited as long as it is a crystal plane of the WC particle, and may be, for example, the {01-12} plane, the {11-20} plane, the {0001} plane, or the {10-10} plane.

[0086] Line analysis is performed on the interface region C between the {0001} crystal plane of the third WC particle and the fourth WC particle using TEM-equipped EDX. The specific procedure for line analysis is as follows: A in the above interface region A Ｖ / A Ｃｏ and A Ｃｒ / A Ｃｏ Referring to (C5) of the measurement method, the {0001} crystal plane of the WC particle is identified in the electron diffraction pattern. With the third WC particle, whose {0001} crystal plane has been identified, observed from the {0001} orientation, the fourth WC particle adjacent to the {0001} crystal plane of the third WC particle is identified. Within the measurement region R, a substantially straight portion of the interface between the {0001} crystal plane of the third WC particle and the fourth WC particle, which is substantially straight and has a length of 25 nm or more, is selected. Line analysis is performed perpendicular to the substantially straight portion.

[0087] Based on the line analysis results, the maximum value B of the cobalt content within the measurement area R is determined. Ｃｏ , Maximum vanadium content B Ｖ , and the maximum value of chromium content B Ｃｒ Identify, B Ｖ / B Ｃｏ and B Ｃｒ / B Ｃｏ Calculate.

[0088] The above measurements are performed in the interface region C between the {0001} crystal plane of five different third WC particles and the fourth WC particle. B in the five interface region C Ｖ / B Ｃｏ The average value is calculated. The average value is B in the interface region C of the cemented carbide of this disclosure. Ｖ / B Ｃｏ This corresponds to B in the five interface regions. Ｃｒ / B Ｃｏ The average value is calculated. The average value is B in the interface region C of the cemented carbide of this disclosure. Ｃｒ / B Ｃｏ This applies.

[0089] It has been confirmed that, as long as the measurements are performed on the same sample, there is almost no variation in the measurement results even when the above measurement is performed multiple times by changing the selected measurement area and the interface area of ​​the object being measured.

[0090] <Method for Manufacturing Carbide Alloys> The carbide alloy of Embodiment 1 can be manufactured by performing the following steps in the order described above: preparation of raw material powder, mixing, molding, sintering, and HIP (Hot Isostatic Pressing). Each step will be described below.

[0091] <Preparation Process> The preparation process involves preparing the raw material powders for the cemented carbide. Examples of raw material powders include tungsten carbide powder containing grain growth inhibitors such as chromium (Cr) and vanadium (V) (hereinafter also referred to as "WC powder with grain growth inhibitor"), Co powder, VC powder, and Cr ３ C ２ Powder is one example. The average particle size of WC powder containing a grain growth inhibitor is 0.2 μm.

[0092] The average particle size of the Co powder is 0.5 μm. The Co powder is strongly ground using an attritor to prepare a Co slurry. The attritor settings are 200 rpm for 2 hours.

[0093] The WC powder containing a grain growth inhibitor is added to the Co slurry and strongly ground using a bead mill to obtain the first mixture.

[0094] VC powder and Cr ３ C ２Commercially available powders can be used. The average particle size of these raw material powders is not particularly limited and can be, for example, 0.5 μm to 2 μm.

[0095] Further raw material powders such as TiC powder, TiN powder, NbC powder, and Ni powder can be prepared. Commercially available raw material powders can be used. The average particle size of these raw material powders is not particularly limited and can be, for example, 0.5 μm to 2 μm.

[0096] The average particle size of the raw material powder refers to the average particle size measured by the FSSS (Fisher Sub-Sieve Sizer) method. This average particle size is measured using the "Sub-Sieve Sizer Model 95" (trademark) manufactured by Fisher Scientific.

[0097] <Mixing Process> The mixing process involves mixing the raw material powders (including the first mixture) prepared in the preparation process in predetermined proportions to obtain a mixed powder. The mixing ratio of each raw material powder is adjusted as appropriate according to the desired composition of the cemented carbide.

[0098] A bead mill is used to mix the raw material powders. The mixing conditions are a rotation speed of 3000 rpm, a ball diameter of φ1 mm, and a mixing time of 6 hours.

[0099] After the mixing process, the mixed powder may be granulated as needed. Granulating the mixed powder makes it easier to fill the die or mold with the mixed powder during the molding process described later. Known granulation methods can be applied to granulation, and commercially available granulators such as spray dryers can be used.

[0100] <Molding Process> The molding process is a process in which the mixed powder obtained in the mixing process is molded into the shape of a cutting tool to obtain a molded body. The molding method and molding conditions in the molding process can be general methods and conditions and are not particularly limited.

[0101] <Sintering Process> The sintering process involves sintering the molded body obtained in the molding process to obtain a cemented carbide intermediate. The molded body is placed in an S-HIP apparatus and heated to 1350°C in an argon atmosphere at a pressure of 7 MPa at a heating rate of 20°C / min, and held at 1350°C for 4 hours. Subsequently, the molded body is cooled to 25°C at a cooling rate of -50°C / min to obtain a cemented carbide intermediate.

[0102] <HIP Process> In the HIP process, the cemented carbide intermediate is subjected to HIP. The HIP conditions are an Ar atmosphere, 10 MPa, and holding at 1300°C for 2 hours. After that, it is cooled to obtain the cemented carbide of Embodiment 1. Conventional known cooling conditions can be used.

[0103] <Features of the cemented carbide manufacturing method of Embodiment 1> In the cemented carbide manufacturing method of Embodiment 1, WC powder containing a grain growth inhibitor is used. This improves the dispersibility of VC powder in the mixed powder, and suppresses the formation of a vanadium-enriched layer in the cemented carbide structure. In conventional general cemented carbide manufacturing methods, WC powder containing a grain growth inhibitor is not used, so the suppression of vanadium-enriched layer formation was insufficient.

[0104] In the manufacturing method of cemented carbide according to Embodiment 1, a fine Co slurry is used, which is obtained by strongly grinding fine Co powder with an average particle size of 0.5 μm using an attritor. Furthermore, a first mixture is used, which is obtained by adding WC powder containing a grain growth inhibitor to the Co slurry and strongly grinding it with a bead mill. As a result, in cemented carbide, fine cobalt particles are uniformly dispersed without localizing aggregation, and the cemented carbide structure tends to become homogeneous. In conventional general cemented carbide manufacturing methods, the above-mentioned fine grinding treatment is not performed on fine Co powder with an average particle size of 0.5 μm, resulting in insufficient uniform dispersion of cobalt in cemented carbide.

[0105] In the mixing step of the cemented carbide manufacturing method of Embodiment 1, the raw material powder is mixed at high speed using ultrafine balls. This promotes the refinement of the raw material powder, improves the dispersibility of the raw materials in the cemented carbide, and makes it easier to achieve a homogeneous cemented carbide structure. In conventional general cemented carbide manufacturing methods, high-speed mixing using ultrafine balls was not performed, resulting in insufficient refinement of the raw material powder.

[0106] In the sintering step of the cemented carbide manufacturing method of Embodiment 1, the molded body is placed in an S-HIP apparatus and heated to 1350°C at a pressure of 7 MPa under an argon atmosphere and a heating rate of 20°C / min, and then held at 1350°C for 4 hours. This allows for densification of the cemented carbide structure even at low temperatures, improves the dispersibility of the raw materials in the cemented carbide, and makes it easier to achieve a homogeneous cemented carbide structure. Conventional general cemented carbide manufacturing methods did not perform S-HIP at low temperatures, resulting in insufficient densification and homogenization of the cemented carbide structure.

[0107] In the sintering step of the cemented carbide manufacturing method of Embodiment 1, the molded body is cooled from 1350°C to 25°C at a cooling rate of -50°C / min. This suppresses the reprecipitation of V and Cr dissolved in Co, and inhibits the formation of vanadium-enriched and chromium-enriched layers. In conventional general cemented carbide manufacturing methods, rapid cooling at a cooling rate of -50°C / min is not performed, resulting in insufficient suppression of the formation of vanadium-enriched and chromium-enriched layers.

[0108] In the HIP process of the cemented carbide manufacturing method of Embodiment 1, low-temperature HIP is performed. This densifies the cemented carbide structure and suppresses grain growth of WC. In conventional general cemented carbide manufacturing methods, HIP is often omitted from the perspective of cost reduction, or even when HIP is performed, it is at a high temperature (e.g., 1350°C), resulting in insufficient densification of the cemented carbide and suppression of WC grain growth.

[0109] The inventors have discovered, through diligent research, that the cemented carbide described herein can be realized by adopting the manufacturing process described above.

[0110] [Embodiment 2: Cutting Tool] The cutting tool of one embodiment of the present disclosure (hereinafter also referred to as "Embodiment 2") includes a cutting edge made of cemented carbide as in Embodiment 1. In the present disclosure, the cutting edge means the part that is involved in cutting. More specifically, the cutting edge means the region enclosed by the cutting edge ridge and a hypothetical plane whose distance from the cutting edge ridge to the cemented carbide side is 0.5 mm or 2 mm.

[0111] Examples of cutting tools include cutting tools, drills, end mills, replaceable cutting tips for milling, replaceable cutting tips for turning, metal saws, gear cutting tools, reamers, or taps. As shown in Figure 1, the cutting tool 10 of Embodiment 2 can exhibit particularly excellent effects in the case of an end mill. The cutting edge 11 of the cutting tool 10 shown in Figure 1 is made of the cemented carbide alloy of Embodiment 1.

[0112] In the cutting tool of Embodiment 2, the cemented carbide of Embodiment 1 may constitute the entire tool or a part of it. Here, "constituting a part" refers to a configuration in which the cemented carbide of Embodiment 1 is brazed to a predetermined position on any base material to form the cutting edge.

[0113] The cutting tool of Embodiment 2 may further include a hard coating that covers at least a portion of the surface of a substrate made of cemented carbide. For example, diamond-like carbon or diamond can be used as the hard coating.

[0114] The cutting tool of Embodiment 2 can be obtained by shaping the cemented carbide of Embodiment 1 into a desired shape.

[0115] This embodiment will be described in more detail by reference to examples. However, this embodiment is not limited by these examples. [Preparation of cemented carbide] <<Samples 1 to 16 and Samples 101 to 110>> The cemented carbide of Samples 1 to 16 and Samples 101 to 110 were prepared by the following process.

[0116] <Preparation Process> As raw material powders, WC powder containing grain growth inhibitor (Allied Material's "WC02NP", average particle size 0.2 μm, referred to as "WC containing grain growth inhibitor" in Table 1), WC powder (average particle size 0.2 μm, no V added, referred to as "WC" in Table 1), Co powder (average particle size 0.5 μm or 2.5 μm), VC powder, Cr ３ C ２ Powders, TiC powder, TiN powder, NbC powder, Ni powder, Si powder, Ge powder, Re powder, and Ru powder were prepared in the proportions shown in Table 1. The average particle size of the raw material powders, excluding the WC powder with grain growth inhibitor and Co powder, was 1 μm. The proportions (mass%) of each raw material powder listed in Table 1 are the proportions when the total raw material powder is considered to be 100% by mass. "Remainder" in Table 1 indicates that the proportion of WC powder with grain growth inhibitor or WC powder is the value obtained by subtracting the total proportion of other raw material powders from 100% by mass of the total raw material powder.

[0117] A fine Co slurry was prepared by vigorously grinding Co powder (average particle size 0.5 μm or 2.5 μm) using an attritor. The attritor conditions were 200 rpm for 2 hours.

[0118]

[0119] <Mixing Process> In the mixing process, each raw material powder was mixed under either condition A or B below. The conditions used for each sample are shown in Table 2. Condition B is the conventional general mixing condition. A: A bead mill is used. The mixing conditions are a rotation speed of 3000 rpm, a ball diameter of φ1 mm, and a mixing time of 6 hours. B: An attritor is used. The mixing conditions are a rotation speed of 100 rpm, a ball diameter of φ6 mm, and a mixing time of 6 hours.

[0120] <Molding Process> A round bar-shaped molded body was obtained by pressing the mixed powder.

[0121] <Sintering Process> The molded body was placed in an S-HIP apparatus and heated to the temperature indicated in the "Temperature" column of Table 2 at a heating rate of 20°C / min under the conditions described in the "Atmosphere / Pressure" column of "Sintering" in Table 2 (where "vac" means vacuum and "Ar / 7MPa" means argon atmosphere and pressure of 7MPa). The body was then held at that temperature for the time indicated in the "Time" column. Subsequently, the molded body was cooled to 25°C at the cooling rate indicated in the "Cooling Rate" column of Table 2 to obtain a cemented carbide intermediate.

[0122]

[0123] <HIP Process> The cemented carbide intermediate was subjected to HIP under the conditions described in the "HIP" column of Table 3. After cooling, the cemented carbide was obtained.

[0124]

[0125] <Sample 111> The cemented carbide of sample 111 was manufactured according to the manufacturing method described in Patent Document 1, using the following steps. <Preparation Step> As raw material powder, powders with the composition shown in the "Mixed Powder" column of Table 1 were prepared.

[0126] Each raw material powder was mixed in the proportions indicated in "Mass %" under "Mixed Powder" in Table 1 to prepare a mixed powder. Mixing was carried out in a ball mill for 15 hours.

[0127] <Molding Process> A round bar-shaped molded body was obtained by pressing the mixed powder.

[0128] <Sintering Process> A pre-sintering process was performed on the molded body. In the pre-sintering process, the molded body was placed in a sintering furnace and held at 100°C in a vacuum for 2 hours (pre-sintering). Subsequently, the main sintering process was performed. The molded body after the pre-sintering process was held at 1420°C in an Ar atmosphere for 1 hour to obtain cemented carbide.

[0129] <Repeated Heat Treatment Process> Next, the cemented carbide obtained in the sintering process was subjected to a rapid cooling process and a heat treatment process twice each, alternately. In the rapid cooling process, the cemented carbide was rapidly cooled to 1100°C at a cooling rate of -60°C / min or more, and held at 1100°C for 30 minutes. In the heat treatment process, the cemented carbide was heated to 1250°C and held at 1250°C for 20 minutes.

[0130] <Cooling Process> Next, the cemented carbide after repeated heat treatment was slowly cooled in an argon (Ar) gas atmosphere to obtain the cemented carbide sample 111.

[0131] ≪Sample 112≫ The cemented carbide of sample 112 was manufactured using the following process based on the manufacturing method described in Reference 1 (Masaru Kawakami, Osamu Terada and Koji Hayashi, Effect of Sintering Cooling Rate on V Segmentation Amount at WC / Co Interface in VC-doped WC-Co Fine-Grained Hardmetal, J. Jpn. Soc. Powder Powder Metallurgy, Vol. 51, No. 8, 2004, pp. 576-585). <Preparation Process> As raw material powders, powders with the composition shown in the "Mixed Powder" column of Table 1 were prepared.

[0132] Each raw material powder was mixed in the proportions indicated in "Mass %" under "Mixed Powder" in Table 1 to prepare a mixed powder. Mixing was performed in a ball mill for 432 ks.

[0133] <Molding Process> A round bar-shaped molded body was obtained by pressing the mixed powder.

[0134] <Sintering Process> The molded body was held in a vacuum at 1380°C for 1.5 hours, and then cooled at -0.67°C / s to obtain a cemented carbide.

[0135] [Evaluation of cemented carbide] <Content of first hard phase, content of binder phase, content of second hard phase, vanadium content, and chromium content of cemented carbide> The content of the first hard phase (volume %), the content of the binder phase (volume %), the content of the second hard phase (volume %), the vanadium content (mass %), and the chromium content (mass %) of the cemented carbide of each sample were measured using the method described in Embodiment 1. The results are shown in Table 4.

[0136]

[0137] <Mode of particle size distribution based on area of ​​tungsten carbide particles, cobalt content of the binder phase, D50 of the binder phase, D10 / D90 of the binder phase, composition of the second hard phase, and D50 of the second hard phase> For each cemented carbide sample, the mode of particle size distribution based on area of ​​tungsten carbide particles, cobalt content of the binder phase, D50 of the binder phase, D10 / D90 of the binder phase, composition of the second hard phase, and D50 of the second hard phase were measured using the method described in Embodiment 1. The results are shown in Table 5.

[0138]

[0139] Ｖ / A Ｃｏ and A Ｃｒ / A Ｃｏ B in interface region C Ｖ / B Ｃｏ and B Ｃｒ / B Ｃｏ > In each cemented carbide sample, A in interface region A Ｖ / A Ｃｏ and A Ｃｒ / A Ｃｏ , and also, B in interface region C Ｖ / B Ｃｏ and B Ｃｒ / B Ｃｏ The values ​​were measured using the method described in Embodiment 1. The results are shown in Table 6.

[0140]

[0141] [Cutting Test] Round bars made of cemented carbide for each sample were machined to create a four-flute ball end mill with a cutting diameter of φ6 mm. Shoulder milling was performed on a workpiece made of hardened steel (58-62 HRC) using the ball end mill. The machining conditions were: rotational speed n 6500 / min, feed rate Vf 1500 mm / min, depth of cut (axial) ap 0.12 mm, depth of cut (radial) ae 0.12 mm, and air blow. The cutting length until the flank wear of the cutting tool reached 100 μm was measured. A cutting length of 35 m or more is considered to indicate a long tool life. A longer cutting length indicates a longer tool life. The results are shown in the "Cutting Length" column of "Cutting Test" in Table 6. Note that the above machining conditions correspond to rough machining of die steel.

[0142] [Discussion] The cemented carbide alloys and cutting tools of Samples 1 to 16 correspond to the examples. These cutting tools were confirmed to have a long tool life.

[0143] The cemented carbide alloys and cutting tools of samples 101 to 112 are comparative examples. These cutting tools exhibited insufficient tool life.

[0144] While embodiments and examples of this disclosure have been described above, it is intended from the outset that the configurations of each of the embodiments and examples described above may be combined or modified in various ways as appropriate. The embodiments and examples disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than the embodiments and examples described above, and all modifications within the meaning and scope of the claims are intended to be included.

[0145] 1. First tungsten carbide particle, 2. Second tungsten carbide particle, 3. Bonding phase, R: Measurement area, 10. Cutting tool, 11. Cutting edge.

Claims

1. A cemented carbide comprising a first hard phase composed of a plurality of tungsten carbide particles and a binder phase containing cobalt, wherein the total content of the first hard phase and the binder phase of the cemented carbide is 80.0% by volume or more, the content of the binder phase of the cemented carbide is 5.0% by volume or more and 21.0% by volume or less, the cobalt content of the binder phase is 50% by mass or more, the 50% cumulative particle size D50 based on the area of the binder phase is 0.10 μm or more and 0.30 μm or less, the ratio D10 / D90 of the 10% cumulative particle size D10 to the 90% cumulative particle size D90 based on the area of the binder phase is 0.26 or more and 0.40 or less, the vanadium content of the cemented carbide is 0.01% by mass or more and 0.20% by mass or less, the chromium content of the cemented carbide is 0.01% by mass or more and 1.00% by mass or less, the tungsten carbide particles include first tungsten carbide particles having a {11-20} crystal plane and second tungsten carbide particles existing adjacent to the {11-20} crystal plane, and in an interface region A between the {11-20} crystal plane of the first tungsten carbide particles and the second tungsten carbide particles, the maximum value A of the cobalt content Ｃｏ to the maximum value A of the vanadium content Ｖ of the ratio A Ｖ / A Ｃｏ is 0.01 or more and 0.5 or less, and in the interface region A, the maximum value A of the cobalt content Ｃｏ to the maximum value A of the chromium content Ｃｒ of the ratio A Ｃｒ / A Ｃｏ is 0.01 or more and 2.0 or less, the tungsten carbide particles include third tungsten carbide particles having a {0001} crystal plane and fourth tungsten carbide particles existing adjacent to the {0001} crystal plane, and in an interface region C between the {0001} crystal plane of the third tungsten carbide particles and the fourth tungsten carbide particles, the maximum value B of the cobalt content Ｃｏ to the maximum value B of the vanadium content Ｖ of the ratio B Ｖ / B Ｃｏ is 0.01 or more and 1.2 or less, and in the interface region C, the maximum value B of the cobalt content Ｃｏ The maximum value of chromium content B Ｃｒ Ratio B Ｃｒ / B Ｃｏ This refers to a cemented carbide alloy with a coefficient of 0.01 or higher and a coefficient of 2.0 or lower.

2. A Ｖ / A Ｃｏ is 0.01 or more and 0.3 or less, and A Ｃｒ / A Ｃｏ is 0.01 or more and 1.5 or less, and the above B Ｖ / B Ｃｏ is 0.4 or more and 1.2 or less, and the above B Ｃｒ / B Ｃｏ The cemented carbide according to claim 1, wherein the coefficient is 0.5 or more and 2.0 or less.

3. The cemented carbide according to claim 1 or claim 2, further comprising a second hard phase, wherein the second hard phase consists of at least one first compound selected from the group consisting of TiNbC, TiNbN, and TiNbCN, and the 50% cumulative particle size D50 of the second hard phase on an area basis is 0.003 μm or more and 0.05 μm or less.

4. The cemented carbide according to any one of claims 1 to 3, wherein the mode of the particle size distribution of the tungsten carbide particles on an area basis is 0.2 μm or more and 0.8 μm or less.

5. A cutting tool comprising a cutting edge made of cemented carbide as described in any one of claims 1 to 4.

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