Cemented Carbide and Cutting Tools

Abstract

A cemented carbide comprising a first hard phase consisting 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 in the cemented carbide is 80.0% by volume or more, the content of the binder phase in 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 grain size D50 on an area basis of the binder phase is 0.10 μm or more and 0.30 μm or less, and the ratio D10 / D of the 10% cumulative grain size D10 on an area basis to the 90% cumulative grain size D90 of the binder phase is 90 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 {11-20} crystal faces and second tungsten carbide particles existing adjacent to the {11-20} crystal faces, and a maximum cobalt content A 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 {11-20} crystal faces and second tungsten carbide particles existing adjacent to the {11-20} crystal faces, and Co Maximum vanadium content A V 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 Maximum chromium content A Cr 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 {0001} crystal faces and fourth tungsten carbide particles adjacent to the {0001} crystal faces, and a maximum cobalt content B Co Maximum vanadium content B V 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 Maximum chromium content BCr Ratio B Cr / B Co is a cemented carbide alloy having a coefficient of friction of 0.01 or more and 2.0 or less.

Description

[Technical Field]

[0001] The present disclosure relates to cemented carbides and cutting tools. [Background technology]

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

[0003] [Patent Document 1] International Publication No. 2023 / 228328 Summary of the Invention

[0004] The cemented carbide of the present disclosure is a cemented carbide comprising a first hard phase consisting 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 in the cemented carbide is 80.0% by volume or more, the content of the binder phase in 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 grain size D50 on an area basis of the binder phase is 0.10 μm or more and 0.30 μm or less, and the ratio D of the 10% cumulative grain size D10 on an area basis to the 90% cumulative grain size D90 of the binder phase is a vanadium content of the cemented carbide is 0.01% by mass or more and 0.20% by mass or less, a 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 {11-20} crystal planes and second tungsten carbide particles adjacent to the {11-20} crystal planes, and a maximum cobalt content A in an interface region A between the {11-20} crystal planes of the first tungsten carbide particles and the second tungsten carbide particles is 0.26 or more and 0.40 or less, Co Maximum vanadium content A V Ratio A V / ACo 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 is 0.01 or more and 2.0 or less, the tungsten carbide particles include third tungsten carbide particles having {0001} crystal faces and fourth tungsten carbide particles adjacent to the {0001} crystal faces, and a maximum cobalt content B in an interface region C between the {0001} crystal faces of the third tungsten carbide particles and the fourth tungsten carbide particles Co Maximum vanadium content B V 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 Maximum chromium content B Cr Ratio B Cr / B Co is a cemented carbide alloy having a coefficient of friction of 0.01 or more and 2.0 or less. [Brief explanation of the drawings]

[0005] [Figure 1] FIG. 1 is a diagram for explaining a method for measuring AV / ACo and ACr / ACo in the interface region A. In FIG. [Figure 2] FIG. 2 is a schematic diagram of a cutting tool according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0006] [Problem to be solved by this disclosure] From the viewpoint of cost reduction, there is a demand for cemented carbide alloys and cutting tools including such alloys that enable the tool life to be extended, particularly when used as materials for cutting tools for rough machining of die steel.

[0007] [Effects of this disclosure] According to the present disclosure, it is possible to provide a cemented carbide alloy and a cutting tool including the same that enable a longer tool life, particularly when used as a material for cutting tools for rough machining of die steel.

[0008] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described. (1) The presently disclosed cemented carbide alloy is a cemented carbide alloy comprising a first hard phase consisting 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 in the cemented carbide alloy is 80.0% by volume or more, the content of the binder phase in the cemented carbide alloy 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 grain size D50 of the binder phase on an area basis is 0.10 μm or more and 0.30 μm or less, and the ratio D of the 10% cumulative grain size D10 to the 90% cumulative grain size D90 of the binder phase on an area basis is a vanadium content of the cemented carbide is 0.01% by mass or more and 0.20% by mass or less, a 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 {11-20} crystal planes and second tungsten carbide particles adjacent to the {11-20} crystal planes, and a maximum cobalt content A in an interface region A between the {11-20} crystal planes of the first tungsten carbide particles and the second tungsten carbide particles is 0.26 or more and 0.40 or less, Co Maximum vanadium content A V 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 Maximum chromium content A Cr Ratio A Cr / A Cois 0.01 or more and 2.0 or less, the tungsten carbide particles include third tungsten carbide particles having {0001} crystal faces and fourth tungsten carbide particles adjacent to the {0001} crystal faces, and a maximum cobalt content B in an interface region C between the {0001} crystal faces of the third tungsten carbide particles and the fourth tungsten carbide particles Co Maximum vanadium content B V 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 Maximum chromium content B Cr Ratio B Cr / B Co is a cemented carbide alloy having a coefficient of friction of 0.01 or more and 2.0 or less.

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

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

[0011] The cemented carbide of the present disclosure contains a first hard phase consisting of tungsten carbide particles and a binder phase containing cobalt, totaling 80.0% by volume or more, with the binder phase content being 5.0% by volume or more and 21.0% by volume or less, and the binder phase containing cobalt being 50% by mass or more, thereby providing the cemented carbide with hardness and toughness suitable for cutting tools.

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

[0013] The vanadium content of the cemented carbide of the present disclosure is 0.01% by mass or more and 0.20% by mass or less. Vanadium has the effect of inhibiting grain growth of tungsten carbide particles. When the vanadium content of the cemented carbide alloy is 0.01% by mass or more, the generation 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 and present in the interface region between WC particles is less likely to form, and a decrease in interface strength is more likely to be suppressed. Therefore, the hardness and strength of the cemented carbide are improved, and the wear resistance and breakage resistance of a cutting tool equipped with a cutting edge made of the cemented carbide are improved.

[0014] The chromium content of the cemented carbide of the present disclosure is 0.01% by mass or more and 1.00% by mass or less. Chromium has the effect of inhibiting grain growth of tungsten carbide particles. When the chromium content of the cemented carbide is 0.01% by mass or more, the generation of coarse grains in the cemented carbide can be effectively suppressed. When the chromium content of the cemented carbide is 1.00% by mass or less, a chromium-enriched layer, in which chromium is concentrated and present at the interface region between WC particles, is less likely to form, and a decrease in interface strength is more likely to be suppressed. Therefore, the hardness and strength of the cemented carbide are improved, and the wear resistance and breakage resistance of a cutting tool equipped with a cutting edge made of the cemented carbide are improved.

[0015] In the interface region A of the cemented carbide of the present disclosure, A V / A Co is between 0.01 and 0.5, and A Cr / A Co is 0.01 or more and 2.0 or less. Furthermore, in the interface region C of the cemented carbide of the present disclosure, B V / B Cois between 0.01 and 1.2, and B Cr / B Co is 0.01 or more and 2.0 or less. This suppresses the formation of a vanadium-enriched layer and a chromium-enriched layer in interface region A and interface region C. This suppresses the decrease in interface strength between WC particles caused by the vanadium-enriched layer and the chromium-enriched layer. Therefore, in this cemented carbide, WC particles are less likely to fall off due to a decrease in interface strength, and in a cutting tool equipped with a cutting edge made of this cemented carbide, the occurrence of wear initiated by chipping is suppressed.

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

[0017] A V / A Co and A Cr / A Co When the tungsten carbide alloy has a cutting edge made of the cemented carbide, the formation of a vanadium-enriched layer and a chromium-enriched layer is further suppressed in the interface region A. This further suppresses the decrease in the interface strength between WC particles caused by the vanadium-enriched layer and the chromium-enriched layer. This further suppresses the occurrence of wear caused by chipping in a cutting tool having a cutting edge made of the cemented carbide.

[0018] In the interface region C, V and Cr are usually more easily concentrated than in the interface region A. V / B Co and B Cr / B CoWhen the tungsten carbide alloy has a cutting edge made of the cemented carbide, the formation of a vanadium-enriched layer and a chromium-enriched layer is further suppressed in the interface region C. This further suppresses the decrease in the interface strength between WC particles caused by the vanadium-enriched layer and the chromium-enriched layer. As a result, the occurrence of wear originating from chipping is further suppressed in a cutting tool having a cutting edge made of the cemented carbide.

[0019] (3) In the above (1) or (2), the cemented carbide further comprises a second hard phase, the second hard phase comprising at least one first compound selected from the group consisting of TiNbC, TiNbN, and TiNbCN, and the second hard phase may have a 50% cumulative grain size D50 on an area basis of 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 the above (1) to (3), the mode in the area-based particle size distribution of the tungsten carbide particles 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 having a cutting edge made of the cemented carbide can have even better wear resistance.

[0021] (5) A cutting tool according to the present disclosure is a cutting tool having a cutting edge made of the cemented carbide according to any one of (1) to (4) above. The cutting tool according to the present disclosure can have a long life, especially when used for rough machining of die steel.

[0022] [Details of the embodiments of the present disclosure] Specific examples of the cemented carbide and cutting tool of the present disclosure will be described below with reference to the drawings. In the drawings of the present disclosure, the same reference numerals represent the same or corresponding parts. Furthermore, dimensional relationships such as length, width, thickness, and depth have been appropriately changed for clarity and simplification of the drawings, and do not necessarily represent actual dimensional relationships.

[0023] In the present disclosure, the notation in the form "A to B" means greater than or equal to A and less than or equal to B, and when no unit is specified for A and only a unit is specified for B, the unit of A and the unit of B are the same.

[0024] In the present disclosure, when a compound or the like is represented by a chemical formula, unless the atomic ratio is particularly limited, it is intended to include any conventionally known atomic ratio, and should not necessarily be limited to only those within the stoichiometric range.

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

[0026] In this disclosure, "comprises," "includes," "has," and variations thereof are open-ended terms. Open-ended terms may or may not include additional elements in addition to the required elements. The term "consisting of" is closed-ended. However, even a configuration expressed in closed terms may include additional elements that are normally incidental impurities or unrelated to the subject technology.

[0027] [Embodiment 1: Cemented Carbide] A cemented carbide according to one embodiment of the present disclosure (hereinafter also referred to as "Embodiment 1") is a cemented carbide 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 binder phase in the cemented carbide is 80.0% by volume or more. The content of the binder phase in 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 grain size D50 of the binder phase on an area basis is 0.10 μm or more and 0.30 μm or less. The ratio D10 / D90 of the 10% cumulative grain size D10 and the 90% cumulative grain size D90 of the binder phase on an area basis 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 {11-20} crystal planes and second tungsten carbide particles adjacent to the {11-20} crystal planes. The maximum cobalt content A is 0.01% by mass or more and 1.00% by mass or less in an interface region A between the {11-20} crystal planes of the first tungsten carbide particles and the second tungsten carbide particles. Co Maximum vanadium content A V Ratio A V / A Co is 0.01 or more and 0.5 or less. In the interface region A, the maximum cobalt content A Co Maximum chromium content A Cr 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 {0001} crystal faces and fourth tungsten carbide particles adjacent to the {0001} crystal faces. In an interface region C between the {0001} crystal faces of the third tungsten carbide particles and the fourth tungsten carbide particles, the maximum cobalt content B Co Maximum vanadium content B V Ratio B V / B Co is 0.01 or more and 1.2 or less. In the interface region C, the maximum cobalt content B Co Maximum chromium content B Cr Ratio BCr / B Co is between 0.01 and 2.0.

[0028] <Composition of 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 binder phase in the cemented carbide is 80.0 vol% or more, and may be 81.3 vol% to 100 vol%, 92 vol% to 100 vol%, 90 vol% to 99 vol%, 92 vol% to 98 vol%, or 94 vol% to 97 vol%.

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

[0030] The cemented carbide of embodiment 1 may include a second hard phase in addition to the first hard phase and binder phase. The second hard phase is composed 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 more than 0% by volume and not more than 20% by volume, more than 0% by volume and not more than 18.7% by volume, more than 0% by volume and not more than 10% by volume, or 1% by volume and not more than 5% by volume.

[0031] The cemented carbide of embodiment 1 may be composed of a first hard phase and a binder phase. The cemented carbide of embodiment 1 may be composed of a first hard phase, a binder phase, and impurities, provided that the effects of the present disclosure are not impaired. The cemented carbide of embodiment 1 may be composed of a first hard phase, a binder phase, and a second hard phase. The cemented carbide of embodiment 1 may be composed of a first hard phase, a binder phase, a second hard phase, and impurities, provided that the effects of the present disclosure are not impaired.

[0032] Examples of the impurities 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 the present 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 optical emission spectroscopy (Inductively Coupled Plasma Emission Spectroscopy). The measuring device that can be used is Shimadzu Corporation's "ICPS-8100" (trademark).

[0033] The methods for measuring the content of the first hard phase, the content of the binder phase, and the content of the second hard phase in the cemented carbide are as follows. (A1) A cemented carbide alloy is cut out at an arbitrary position to expose a cross section, which is then polished 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 photographed area is set to the center of the cemented carbide cross section, that is, a position that does not include areas with properties that are clearly different from the bulk part, such as near the surface of the cemented carbide (a position where the photographed area is entirely the bulk part of the cemented carbide). The observation magnification is 5000x. The measurement conditions are an accelerating voltage of 3 kV, a current value of 2 nA, and a working distance (WD) of 5 mm.

[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 binarized image, the first region consisting of the first hard phase and the second region consisting of the binder phase and the second hard phase can be distinguished by the shade of color. For example, in the binarized image, the first hard phase is shown as a black region, and the binder phase and the second hard phase are shown as white regions.

[0036] (D1) The photographed area in (B1) above is analyzed using an energy dispersive X-ray spectrometer (SEM-EDX) attached to a scanning electron microscope (apparatus: Carl Zeiss Gemini450 (trademark)) to obtain an elemental mapping image.

[0037] (E1) By superimposing the binarized image obtained in (C1) above on the element mapping image obtained in (D1) above, the regions where the first hard phase, binder phase, and second hard phase exist are identified on the binarized image. The regions shown in black in the binarized image and where tungsten (W) and carbon (C) exist in the element mapping image correspond to the regions where the first hard phase exists. The regions shown in white in the binarized image and where cobalt (Co) exists in the element mapping image correspond to the regions where the binder phase exists. The regions shown in white in the binarized image and where titanium (Ti) or niobium (Nb) exist in the element 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 image after binarization processing. Using the image analysis software, the area percentages of the first hard phase, binder phase, and second hard phase are measured using the area of ​​the entire measurement field as the denominator.

[0039] (G1) The measurement of (F1) above is carried out in five different non-overlapping measurement fields. In the present disclosure, the average of the area percentages 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 of the area percentages of the binder phase in the five measurement fields corresponds to the content (volume %) of the binder phase in the cemented carbide. The average of the area percentages 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] As long as measurements are made on the same sample, it has been confirmed that there is almost no variation in the measurement results even if the above measurement is performed multiple times by changing the selected location of the measurement field.

[0041] <1st hard phase> <Composition of the first hard phase> In the cemented carbide of the first embodiment, the first hard phase is composed of a plurality of tungsten carbide particles (hereinafter also referred to as "WC particles"). The tungsten carbide particles include not only "pure WC particles (including WC containing no impurity elements and WC with impurity elements below the detection limit)" but also "WC particles containing impurities therein, as long as the effects of the present disclosure are not impaired." Examples of impurities include iron (Fe), molybdenum (Mo), and sulfur (S).

[0042] <Modulus in particle size distribution based on area of ​​tungsten carbide particles> In the cemented carbide of embodiment 1, the mode in the particle size distribution on an area basis of the 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 the present disclosure, the method for measuring the mode in the area-based particle size distribution of tungsten carbide particles in a 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 content of the binder phase, and the content of the second hard phase in the cemented carbide, the region where the first hard phase exists is identified in the image after the binarization process.

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

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

[0047] As long as measurements are made on the same sample, it has been confirmed that there is almost no variation in the measurement results even if the above measurement is performed multiple times by changing the selected location of the measurement field.

[0048] <Binded phase> <Composition of binder phase> In the cemented carbide of embodiment 1, the cobalt content of the binder phase is 50% by mass or more. This allows the cemented carbide to have excellent toughness. The cobalt content of the binder 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 element mapping image and a binarized image are obtained by the same methods as (A1) to (E1) of the method for measuring the first hard phase content, binder phase content, and second hard phase content of the cemented carbide described above. The element mapping image and the binarized image are superimposed to identify the binder phase region in the element mapping image. A rectangular measurement field of view of 24.9 μm × 18.8 μm is set in the element mapping image. The cobalt content is measured in the binder phase region in the measurement field of view. The above measurement is performed in five different, non-overlapping measurement fields of view. In the present disclosure, the average of the cobalt contents in the binder phase region in the five measurement fields of view corresponds to the binder phase cobalt content.

[0050] As long as measurements are made on the same sample, it has been confirmed that there is almost no variation in the measurement results even if the above measurement is performed multiple times by changing the selected location 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 may consist of cobalt and the first element.

[0052] In the cemented carbide of embodiment 1, the binder phase may contain, 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 bonded phase> In the cemented carbide of embodiment 1, the 50% cumulative grain size D50 of the binder phase on an area basis (hereinafter also referred to as "D50 of the binder phase") is 0.10 μm or more and 0.30 μm or less, or may be 0.11 μm or more and 0.28 μm or less, or may be 0.12 μm or more and 0.20 μm or less.

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

[0055] In the present disclosure, the method for measuring D50 and D10 / D90 of the binder phase in a cemented carbide is 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, the region where the binder phase exists is identified in the image after the binarization process.

[0057] (B3) Prepare five binarized images in which the areas of the bonded phase were identified, and set a rectangular measurement field of view of 40.3 μm long x 30.2 μm wide in each image. Using image analysis software (ImageJ ver. 1.51J8), identify the outer edge of each bonded phase in the measurement field, and measure the area of ​​each bonded phase.

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

[0059] As long as measurements are made on the same sample, it has been confirmed that there is almost no variation in the measurement results even if the above measurement is performed multiple times by changing the selected location of the measurement field.

[0060] <Second hard phase> ≪Composition≫ In embodiment 1, the second hard phase is composed of at least one first compound selected from the group consisting of TiNbC, TiNbN, and TiNbCN. In the present disclosure, each of TiNbC, TiNbN, and TiNbCN is not limited to a 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 any conventionally known ratio as long as it does not impair the effects of the present disclosure.

[0061] The second hard phase may contain metal elements such as tungsten (W), chromium (Cr), and cobalt (Co) within a range that 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 contents of W, Cr, and Co in the second hard phase are measured by STEM-EDX.

[0062] The composition of the second hard phase was measured as follows. (A4) An arbitrary position of the cemented carbide is thinned using an ion slicer (device: IB09060CIS (trademark) manufactured by JEOL Ltd.) to prepare a sample with a thickness of 30 nm to 100 nm. The acceleration voltage of the ion slicer is 6 kV for thinning and 2 kV for finish processing.

[0063] (B4) The above sample is observed at 50,000x magnification using a scanning transmission electron microscope (STEM) (JFM-ARM300F (trademark) manufactured by JEOL Ltd.) to obtain a STEM-HAADF (HAADF: high-angle annular dark field) image. The imaging area for the STEM-HAADF image is set to the center of the sample, i.e., a position that does not include areas with properties clearly different from the bulk part, such as the vicinity of the surface of the cemented carbide (a position where the entire imaging area is the bulk part 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 EDX attached to the STEM to obtain an elemental mapping image. In the elemental mapping image, regions where titanium (Ti) and niobium (Nb) and one or both of carbon (C) and nitrogen (N) exist are identified as the second hard phase, and the composition of the second hard phase is identified.

[0065] As long as measurements are made on the same sample, it has been confirmed that there is almost no variation in the measurement results even if the above measurement is performed multiple times by changing the selected location of the measurement field.

[0066] <50% cumulative grain size D50 based on the area of ​​the second hard phase> In the cross section of the cemented carbide of the first embodiment, the 50% cumulative grain size D50 on an area basis 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 the present disclosure, the 50% cumulative grain size D50 on an area basis of the second hard phase of a cemented carbide (hereinafter also referred to as "D50 of the second hard phase") is measured in the same manner as in the above-mentioned method for measuring D50 of the binder phase of a cemented carbide, except that the region where the second hard phase exists is identified in the image after binarization processing, instead of the binder phase. As long as the measurement is performed on the same sample, it has been confirmed that there is almost no variation in the measurement results even if the above measurement is performed multiple times by changing the selected location of the measurement field of view.

[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, or 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 atomic 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, and may be 0.02% by mass or more and 0.99% by mass or less, or alternatively, 0.05% by mass or more and 0.95% by mass or less. The chromium content of the cemented carbide is measured by ICP atomic emission spectroscopy.

[0070] <A in the interfacial region 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 {11-20} crystal planes and second tungsten carbide particles adjacent to the {11-20} crystal planes. The maximum cobalt content A is 0.015% at an interface region A between the {11-20} crystal planes of the first tungsten carbide particles and the second tungsten carbide particles. Co Maximum vanadium content A V Ratio A V / A Cois 0.01 or more and 0.5 or less, and may be 0.01 or more and 0.45 or less, 0.01 or more and 0.3 or less, or 0.01 or more and 0.2 or less.

[0071] In the interfacial region A, the maximum cobalt content A Co Maximum chromium content A Cr Ratio A Cr / A Co is 0.01 or more and 2.0 or less, and may be 0.01 or more and 1.7 or less, 0.01 or more and 1.5 or less, or 0.01 or more and 0.9 or less. V / A Co and A Cr / A Co can be combined as appropriate.

[0072] A in the interfacial region A V / A Co and A Cr / A Co The measurement method is as follows. (A5) A thin sample having 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 mirror-finished. Examples of mirror-finishing methods include polishing with diamond paste, using a focused ion beam (FIB) device, using a cross-section polisher (CP) device, and combinations of these methods.

[0073] (B5) The mirror-finished surface of the thin sample is observed with a scanning transmission electron microscope (STEM) (JFM-ARM300F (trademark) manufactured by JEOL Ltd.) to obtain an electron diffraction image of the WC particles. The observation magnification is 2,000,000 times and the pixel resolution is 256 × 256.

[0074] (C5) Identifying the {11-20} crystal plane of a WC particle in an electron diffraction image. Observing the first WC particle, whose {11-20} crystal plane has been identified, from the {11-20} orientation, identifying the second WC particle that exists adjacent to the {11-20} crystal plane of the first WC particle.

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

[0076] A 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 TEM-attached EDX (energy dispersive X-ray spectroscopy). In the line analysis, the percentages of W, Co, chromium (Cr), and vanadium (V) are measured, with the total number of atoms of tungsten (W), cobalt (Co), chromium (Cr), and vanadium (V) taken as 100 atomic %.

[0077] The specific procedure for line analysis will be explained using Figure 1. Figure 1 shows a schematic electron diffraction image obtained by observing a thin section sample with a TEM. In Figure 1, the measurement region R for line analysis is a rectangular region indicated by the symbol R.

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

[0079] Based on the line analysis results, the maximum cobalt content A within the measurement area R Co , maximum vanadium content A V , and the maximum chromium content A Cr Identify and A V / A Co and A Cr / A Co Calculate.

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

[0081] As long as measurements are made on the same sample, it has been confirmed that there is almost no variation in the measurement results even if the above measurement is performed multiple times by changing the selected location of the measurement region and the interface region to be measured.

[0082] <B in the interfacial region C V / B Co and B Cr / B Co > The tungsten carbide particles of the cemented carbide of embodiment 1 include third tungsten carbide particles having {0001} crystal faces and fourth tungsten carbide particles adjacent to the {0001} crystal faces. The maximum cobalt content B is 0.05 at an interface region C between the {0001} crystal faces of the third tungsten carbide particles and the fourth tungsten carbide particles. Co Maximum vanadium content B V Ratio B V / B Co is 0.01 or more and 1.2 or less, may be 0.35 or more and 1.2 or less, may be 0.4 or more and 1.2 or less, or may be 0.4 or more and 1.1 or less.

[0083] In the interfacial region C, the maximum cobalt content B Co Maximum chromium content B Cr Ratio B Cr / B Cois 0.01 or more and 2.0 or less, may be 0.5 or more and 2.0 or less, may be 0.5 or more and 1.98 or less, or may be 1.32 or more and 1.98 or less. V / B Co and B Cr / B Co can be combined as appropriate.

[0084] B in the interfacial region C V / B Co and B Cr / B Co The measurement method for A in the interfacial region A is as follows. V / A Co and A Cr / A Co An electron diffraction image of the WC particles is obtained using the same methods as those in (A5) and (B5) of the measurement method 1. In the electron diffraction image, the {0001} crystal plane of the WC particles is identified. When observed from the {0001} direction, the {0001} crystal plane of the third WC particle and the fourth WC particle present adjacent to the {0001} crystal plane of the third WC particle are identified.

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

[0086] A 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 EDX attached to a TEM. The specific procedure for the line analysis is as follows. V / A Co and A Cr / A CoReferring to (C5) of the measurement method, the {0001} crystal plane of the WC particle is identified in the electron diffraction image. The third WC particle, whose {0001} crystal plane has been identified, is observed from the {0001} direction, and the fourth WC particle present adjacent to the {0001} crystal plane of the third WC particle is identified. Within the measurement region R, a substantially straight line portion with a length of 25 nm or more is selected from the interface between the {0001} crystal plane of the third WC particle and the fourth WC particle. Line analysis is performed in a direction perpendicular to the substantially straight line portion.

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

[0088] The above measurement is carried out at the interface region C between the {0001} crystal plane of five different third WC particles and the fourth WC particle. V / B Co The average value of B in the interface region C of the cemented carbide of the present disclosure is calculated. V / B Co B in the five interfacial regions Cr / B Co The average value of B in the interface region C of the cemented carbide of the present disclosure is calculated. Cr / B Co This applies to:

[0089] As long as measurements are made on the same sample, it has been confirmed that there is almost no variation in the measurement results even if the above measurement is performed multiple times by changing the selected location of the measurement region and the interface region to be measured.

[0090] <Method of manufacturing cemented carbide> The cemented carbide of embodiment 1 can be manufactured by carrying out the steps of preparing raw material powder, mixing, molding, sintering, and HIP (Hot Isostatic Pressing) in the above order. Each step will be described below.

[0091] <Preparation process> The preparation step is a step of preparing raw material powders of materials constituting 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 containing grain growth inhibitors"), Co powder, VC powder, and Cr3C2 powder. The WC powder containing grain growth inhibitors has an average particle size of 0.2 μm.

[0092] The average particle size of the Co powder was 0.5 μm. The Co powder was pulverized in an attritor to prepare a Co slurry. The attritor conditions were a rotation speed of 200 rpm for 2 hours.

[0093] The WC powder containing the grain growth inhibitor is added to the Co slurry, and the mixture is pulverized intensively in a bead mill to obtain a first mixture.

[0094] Commercially available VC powder and Cr3C2 powder 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, TiC powder, TiN powder, NbC powder, Ni powder, etc. can be prepared as raw material powder. These raw material powders can be commercially available. 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, using a Fisher Scientific "Sub-Sieve Sizer Model 95" (trademark).

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

[0098] For the mixing of the raw material powders, 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.

[0099] After the mixing process, the mixed powder may be granulated as necessary. By granulating the mixed powder, it is easier to fill the mixed powder into the die or mold during the subsequent molding process. For granulation, known granulation methods can be applied, for example, a commercially available granulator such as a spray dryer can be used.

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

[0101] <Sintering Process> The sintering process is a process of sintering the molded body obtained in the molding process to obtain a cemented carbide intermediate. The molded body is placed in an S-HIP device, heated to 1350°C at a heating rate of 20°C / min under an argon atmosphere and a pressure of 7 MPa, 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, HIP is performed on the cemented carbide intermediate. The HIP conditions are holding at 1300°C for 2 hours under an Ar atmosphere and a pressure of 10 MPa. Then it is cooled to obtain the cemented carbide of Embodiment 1. The cooling conditions can use conventionally known conditions.

[0103] <Features of the Manufacturing Method of the Cemented Carbide of Embodiment 1> In the method for producing a cemented carbide according to the first embodiment, 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 methods for producing cemented carbide, WC powder containing a grain growth inhibitor is not used, and therefore the suppression of the formation of a vanadium-enriched layer is insufficient.

[0104] In the method for producing a cemented carbide according to the first embodiment, a fine Co slurry is used, which is prepared by strongly pulverizing a fine Co powder having an average particle size of 0.5 μm in an attritor. Furthermore, a first mixture is prepared by adding a WC powder containing a grain growth inhibitor to the Co slurry and strongly pulverizing the mixture in a bead mill. This allows the fine cobalt particles to be uniformly dispersed in the cemented carbide without localized aggregation, making the cemented carbide structure more homogeneous. Conventional methods for producing cemented carbide do not include the step of performing the above-described refining treatment on the fine Co powder having an average particle size of 0.5 μm, resulting in insufficient uniform dispersion of cobalt in the cemented carbide.

[0105] In the mixing step of the cemented carbide manufacturing method of embodiment 1, raw material powders are mixed at high speed using ultrafine balls. This facilitates the refinement of the raw material powders, improves the dispersibility of the raw materials in the cemented carbide, and makes the cemented carbide structure more homogeneous. In conventional methods for manufacturing cemented carbide, high-speed mixing using ultrafine balls is not performed, and therefore the raw material powders are not sufficiently refined.

[0106] In the sintering step of the method for producing a cemented carbide according to the first embodiment, the compact is placed in an S-HIP apparatus, and heated to 1350°C at a heating rate of 20°C / min under an argon atmosphere at a pressure of 7 MPa, and then held at 1350°C for 4 hours. This makes it possible to densify the cemented carbide structure even at low temperatures, improves the dispersion of raw materials in the cemented carbide, and tends to make the cemented carbide structure more homogenous. In conventional methods for producing cemented carbide, S-HIP is not performed at low temperatures, and therefore the densification and homogenization of the cemented carbide structure are insufficient.

[0107] In the sintering step of the method for producing a cemented carbide according to the first embodiment, the compact is cooled from 1350°C to 25°C at a temperature drop rate of -50°C / min. This prevents reprecipitation of V and Cr dissolved in Co, thereby preventing the formation of a vanadium-enriched layer and a chromium-enriched layer. In conventional methods for producing cemented carbide, rapid cooling at a temperature drop rate of -50°C / min is not performed, and therefore the formation of a vanadium-enriched layer and a chromium-enriched layer is not sufficiently prevented.

[0108] In the HIP step of the method for producing a cemented carbide according to embodiment 1, low-temperature HIP is performed. This densifies the cemented carbide structure and suppresses the grain growth of WC. In conventional methods for producing cemented carbide, HIP is often not performed to reduce costs, or even when HIP is performed, the temperature is high (e.g., 1350°C), so the densification of the cemented carbide and the suppression of the grain growth of WC are insufficient.

[0109] The inventors have found, as a result of extensive research, that the cemented carbide of the present disclosure can be realized by employing the above manufacturing process.

[0110] [Embodiment 2: Cutting Tool] A cutting tool according to one embodiment of the present disclosure (hereinafter also referred to as "Embodiment 2") includes a cutting edge made of the cemented carbide of Embodiment 1. In this disclosure, the cutting edge refers to the portion involved in cutting. More specifically, the cutting edge refers to the region surrounded by the cutting edge ridge and an imaginary plane that is 0.5 mm or 2 mm away from the cutting edge ridge toward the cemented carbide.

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

[0112] In the cutting tool of Embodiment 2, the cemented carbide of Embodiment 1 may constitute the entire tool or may constitute a part of the tool. Here, "constitute a part" refers to a mode in which the cemented carbide of Embodiment 1 is brazed to a predetermined position of any substrate to form a cutting edge, etc.

[0113] The cutting tool of the second embodiment may further include a hard film that covers at least a part of the surface of the substrate made of cemented carbide. The hard film may be made of, for example, diamond-like carbon or diamond.

[0114] The cutting tool of the second embodiment can be obtained by forming the cemented carbide of the first embodiment into a desired shape. [Example]

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

[0116] <Preparation process> The raw powders were prepared in the proportions shown in Table 1: WC powder with grain growth inhibitor ("WC02NP" manufactured by A.L.M.T. Co., Ltd., average particle size 0.2 μm, referred to as "WC with 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, Cr3C2 powder, TiC powder, TiN powder, NbC powder, Ni powder, Si powder, Ge powder, Re powder, and Ru powder. The average particle size of the raw powders other than the WC powder with grain growth inhibitor and the Co powder was 1 μm. The proportion (mass %) of each raw powder listed in Table 1 is the proportion relative to the total raw powder as 100 mass %. The "remainder" in Table 1 indicates that the proportion of the WC powder with grain growth inhibitor or the WC powder is the value obtained by subtracting the total proportion of the other raw powders from the total raw powder as 100 mass %.

[0117] Co powder (average particle size: 0.5 μm or 2.5 μm) was pulverized in an attritor at a rotation speed of 200 rpm for 2 hours to prepare a fine Co slurry.

[0118] [Table 1]

[0119] <Mixing process> In the mixing process, each raw material powder was mixed under the following conditions A or B. The conditions used for each sample are shown in Table 2. Condition B is a 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 was used. The mixing conditions were a rotation speed of 100 rpm, a ball diameter of 6 mm, and a mixing time of 6 hours.

[0120] <Forming process> The mixed powder was pressed to obtain a round bar-shaped compact.

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

[0122]

Table 2

[0123] <HIP Process> The cemented carbide intermediate was subjected to HIP under the conditions described in the "HIP" column of Table 3. Then it was cooled to obtain a cemented carbide.

[0124]

Table 3

[0125] ≪Sample 111≫ The cemented carbide of Sample 111 was produced in the following process based on the production method of Patent Document 1. <Preparation Process> As raw material powders, powders having the composition shown in the "Powder" column of Table 1 were prepared. raw material Each raw material powder was mixed in the blending amount shown in "Mass%" of "Powder" in Table 1 to produce a mixed powder. The mixing was carried out using a ball mill for 15 hours.

[0126] Each raw material powder was raw material powder was mixed in the blending amount shown in "Mass%" of "Powder" to produce a mixed powder. The mixing was carried out using a ball mill for 15 hours.

[0127] <Forming Process> The mixed powder was pressed to obtain a formed body in the shape of a round bar.

[0128] <Sintering Process> The compact was subjected to a pre-sintering process. In the pre-sintering process, the compact was placed in a sintering furnace and held in a vacuum at 100°C for 2 hours (pre-sintering). Subsequently, a main sintering process was carried out. The compact after the pre-sintering process was heated at 1420°C in an Ar atmosphere. ℃ The mixture was held at this temperature for 1 hour to obtain a cemented carbide.

[0129] <Repeated heat treatment process> The cemented carbide obtained in the sintering process was then subjected to a rapid cooling process and a heat treatment process, each performed twice. In the rapid cooling process, the cemented carbide was rapidly cooled to 1100°C at a cooling rate of -60°C / min or faster 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> Subsequently, the cemented carbide after the repeated heat treatment steps 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 produced by the following steps based on the manufacturing method described in Reference 1 (Masaru Kawakami, Osamu Terada and Koji Hayashi, Effect of Sintering Cooling Rate on V Segregation 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 powder, " raw material Powders having the compositions shown in the "Powder" column were prepared.

[0132] Each raw material powder is listed in Table 1. raw material The powders were mixed in the amounts shown in "% by mass" in the "Powder" column to prepare mixed powders. Mixing was carried out in a ball mill for 432ks.

[0133] <Forming process> The mixed powder was pressed to obtain a round bar-shaped compact.

[0134] <Sintering process> The compact 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 the first hard phase, binder phase, second hard phase, vanadium, and chromium of the cemented carbide> The content (vol %) of the first hard phase, the content (vol %) of the binder phase, the content (vol %) of the second hard phase, the vanadium content (mass %), and the chromium content (mass %) of the cemented carbide of each sample were measured by the method described in embodiment 1. The results are shown in Table 4.

[0136] [Table 4]

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

[0138] [Table 5]

[0139] <A in the interfacial region A V / A Co and A Cr / A Co , B in the interfacial region C V / B Co and B Cr / BCo > For each cemented carbide sample, A in the interface region A V / A Co and A Cr / A Co , and B in the interface region C V / B Co and B Cr / B Co was measured by the method described in embodiment 1. The results are shown in Table 6.

[0140] [Table 6]

[0141] [Cutting test] Each cemented carbide alloy round bar was machined to fabricate a four-flute ball end mill with a cutting diameter of 6 mm. The ball end mill was used to perform shoulder milling on a workpiece made of hardened steel (58-62 HRC). The machining conditions were a rotational speed of n 6500 / min, a feed rate of Vf 1500 mm / min, an axial depth of cut of ap 0.12 mm, a radial depth of cut of ae 0.12 mm, and air blow. The cutting length was measured until the flank wear of the cutting tool reached 100 μm. A cutting length of 35 m or greater was considered to be a long tool life. Longer cutting lengths indicate longer tool life. The results are shown in the "Cutting Length" column of the "Cutting Test" section in Table 6. The above machining conditions apply to rough machining of die steel.

[0142] [Consideration] The cemented carbide alloys and cutting tools of Samples 1 to 16 correspond to Examples. It was confirmed that these cutting tools have a long tool life.

[0143] The cemented carbide alloys and cutting tools of Samples 101 to 112 correspond to comparative examples. These cutting tools had insufficient tool life.

[0144] Although the embodiments and examples of the present disclosure have been described above, it is originally intended that the configurations of the above-described embodiments and examples may be appropriately combined or modified in various ways. The embodiments and examples disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims, not by the embodiments and examples described above, and is intended to include meanings equivalent to the claims and all modifications within the scope of the claims. [Explanation of symbols]

[0145] 1 first tungsten carbide particle, 2 second tungsten carbide particle, 3 binder phase, R measurement area, 10 cutting tool, 11 cutting edge.

Claims

1. A cemented carbide 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 in the cemented carbide is 80.0% by volume or more, The content of the binder phase in the cemented carbide is 5.0 vol% or more and 21.0 vol% or less, the cobalt content of the binder phase is 50% by mass or more; The binder phase has an area-based 50% cumulative particle diameter D50 of 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 on an area basis 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 {11-20} crystal planes and second tungsten carbide particles adjacent to the {11-20} crystal planes; In an interface region A between the {11-20} crystal plane of the first tungsten carbide particle and the second tungsten carbide particle, a maximum value A of the cobalt content Ｃｏ Maximum vanadium content A Ｖ Ratio A Ｖ / A Ｃｏ is equal to or greater than 0.01 and equal to or less than 0.5, In the interface region A, the maximum value A of the cobalt content Ｃｏ The maximum chromium content A Ｃｒ Ratio A Ｃｒ / A Ｃｏ is equal to or greater than 0.01 and equal to or less than 2.0, the tungsten carbide particles include third tungsten carbide particles having {0001} crystal faces and fourth tungsten carbide particles adjacent to the {0001} crystal faces; 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 Maximum vanadium content B Ｖ Ratio B Ｖ / B Ｃｏ is equal to or greater than 0.01 and equal to or less than 1.2, In the interface region C, the maximum value B of the cobalt content Ｃｏ Maximum chromium content B Ｃｒ Ratio B Ｃｒ / B Ｃｏ is 0.01 or more and 2.0 or less.

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

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

4. 3. The cemented carbide according to claim 1, wherein the mode in the area-based particle size distribution of the tungsten carbide particles is 0.2 μm or more and 0.8 μm or less.

5. A cutting tool having a cutting edge made of the cemented carbide according to claim 1 or 2.

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