Cemented carbide and cutting tool

Abstract

Provided is a cemented carbide comprising: a first hard phase composed of a plurality of tungsten carbide particles, at 65.0 vol% to 95.0 vol%; a second hard phase composed of at least one first compound selected from the group consisting of TiNbC, TiNbN, TiNbCN, TiTaC, TiTaN, TiTaCN, TiTaNbC, TiTaNbN, and TiTaNbCN, at 0.1 vol% to 5.0 vol%; and a binder phase containing 50 mass% or more cobalt at 4.0 vol% to 25.0 vol%. The total content of the first hard phase, the second hard phase, and the binder phase in the cemented carbide is 94 vol% or more. The standard deviation sd in a particle size distribution of the tungsten carbide particles, in terms of the volume-based Heywood diameter, is 0.25 μm to 0.50 μm. The percentage of second hard phase particles having a diameter of 0.2 μm or less, relative to the total number of the second hard phase particles, is 1% to 10%. The percentage of second hard phase particles having a diameter of 0.8 μm or more, relative to the total number of the second hard phase particles, is 1% to 10%.

Description

Carbide alloys and cutting tools

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

[0002] Conventionally, cemented carbide alloys comprising a phase mainly composed of tungsten carbide (WC), a phase consisting of carbides, nitrides, and carbonitrides containing metal elements other than tungsten, and a bonding phase mainly composed of iron group elements have been used as materials for cutting tools (Patent Document 1).

[0003] International Publication No. 2024 / 105882

[0004] The cemented carbide alloy of the present disclosure comprises a first hard phase, a second hard phase, and a binder phase, wherein the first hard phase consists of a plurality of tungsten carbide particles, the second hard phase consists of at least one first compound selected from the group consisting of TiNbC, TiNbN, TiNbCN, TiTaC, TiTaN, TiTaCN, TiTaNbC, TiTaNbN, and TiTaNbCN, the binder phase contains 50% by mass or more of cobalt, the total content of the first hard phase, the second hard phase, and the binder phase of the cemented carbide alloy is 94% by volume or more, and the content of the first hard phase of the cemented carbide alloy is 65.0% by volume or more. The cemented carbide alloy has a content of 5.0 volume% or less, the content of the second hard phase of the cemented carbide alloy is 0.1 volume% to 5.0 volume%, the content of the binder phase of the cemented carbide alloy is 4.0 volume% to 25.0 volume%, the standard deviation sd of the volume-based particle size distribution of the Heywood diameter of the tungsten carbide particles is 0.25 μm to 0.50 μm, the percentage of the number of second hard phases with a diameter of 0.2 μm or less relative to the total number of second hard phases is 1% to 10%, and the percentage of the number of second hard phases with a diameter of 0.8 μm or more relative to the total number of second hard phases is 1% to 10%.

[0005] Figure 1 is a schematic diagram of a cutting tool (end mill) according to Embodiment 2. Figure 2 is a schematic diagram of a cutting tool (exchangeable cutting tip) according to Embodiment 2.

[0006] [Problems this disclosure aims to solve] From the perspective of cost reduction, there is a need for cemented carbide and cutting tools made therefrom that enable longer tool life, even when used as materials for cutting tools for finishing Inconel and precision machining of stainless steel.

[0007] [Effects of this disclosure] According to this disclosure, it is possible to provide cemented carbide and cutting tools equipped therewith that enable longer tool life, even when used as a material for cutting tools for finishing Inconel and precision machining of stainless steel.

[0008] [Description of Embodiments of the Disclosure] Embodiments of the Disclosure will be described first by listing them. (1) The cemented carbide of the Disclosure is a cemented carbide comprising a first hard phase, a second hard phase, and a binder phase, wherein the first hard phase consists of a plurality of tungsten carbide particles, the second hard phase consists of at least one first compound selected from the group consisting of TiNbC, TiNbN, TiNbCN, TiTaC, TiTaN, TiTaCN, TiTaNbC, TiTaNbN, and TiTaNbCN, the binder phase contains 50% by mass or more of cobalt, the total content of the first hard phase, the second hard phase, and the binder phase of the cemented carbide is 94% by volume or more, and the content of the first hard phase of the cemented carbide is 65.0% by volume or less. The cemented carbide alloy has a composition of 95.0% by volume or less, a content of the second hard phase of the cemented carbide alloy of 0.1% by volume or more and 5.0% by volume or less, a content of the binder phase of the cemented carbide alloy of 4.0% by volume or more and 25.0% by volume or less, a standard deviation (sd) in the volume-based particle size distribution of the Heywood diameter of the tungsten carbide particles of 0.25 μm or more and 0.50 μm or less, a percentage of the number of second hard phases with a diameter of 0.2 μm or less relative to the total number of second hard phases of the

[0009] According to this disclosure, it is possible to provide cemented carbide and cutting tools equipped therewith that enable extended tool life, even when used as materials for cutting tools for finishing Inconel and precision machining of stainless steel. The reason for this is presumed to be as follows.

[0010] The cemented carbide alloy of this disclosure contains a first hard phase consisting of multiple tungsten carbide particles (hereinafter also referred to as "WC particles"), a second hard phase consisting of TiNbC or the like, and a binder phase, totaling 94 volume% or more. The content of the first hard phase is 65.0 volume% to 95.0 volume%, the content of the second hard phase is 0.1 volume% to 5.0 volume%, and the content of the binder phase is 4.0 volume% to 25.0 volume%. As a result, the cemented carbide alloy can have hardness and toughness suitable for cutting tools.

[0011] In the cemented carbide alloy of this disclosure, the standard deviation (sd) of the particle size distribution of tungsten carbide particles based on volume of Heywood diameter is 0.25 μm or more and 0.50 μm or less, and the particle size distribution of tungsten carbide particles is broad. In this cemented carbide alloy, gaps between tungsten carbide particles are easily filled by other tungsten carbide particles, and the tungsten carbide particles are closely packed together. As a result, when using a cutting tool made of this cemented carbide alloy, the shedding of tungsten carbide particles is suppressed. Therefore, when using this cutting tool for finishing Inconel and precision machining of stainless steel, surface deterioration is suppressed and tool life is improved.

[0012] In the cemented carbide alloy of this disclosure, the percentage of second hard phases with a diameter of 0.2 μm or less relative to the total number of second hard phases is 1% to 10%, and the percentage of second hard phases with a diameter of 0.8 μm or more relative to the total number of second hard phases is 1% to 10%, and the grain size distribution of the second hard phase is narrow and sharp. In this cemented carbide alloy, the second hard phase easily fills the gaps between tungsten carbide particles, and the retention force of the tungsten carbide particles is improved by the second hard phase. As a result, when using a cutting tool made of this cemented carbide alloy, the shedding of tungsten carbide particles is suppressed. Therefore, when using this cutting tool for finishing Inconel and precision machining of stainless steel, surface deterioration is suppressed and tool life is improved. In this disclosure, the diameter of the second hard phase means the Heywood diameter of the multiple crystal grains constituting the second hard phase in the cross-section of the cemented carbide.

[0013] (2) In (1) above, the volume average diameter mv of the tungsten carbide particles may be 0.2 μm or more and 0.65 μm or less. This further suppresses the shedding of tungsten carbide particles when using cutting tools made of cemented carbide. Also, if the volume average diameter mv of the tungsten carbide particles is 0.2 μm or more, the toughness of the cemented carbide is improved. If the volume average diameter mv of the tungsten carbide particles is 0.65 μm or less, the hardness of the cemented carbide is improved.

[0014] (3) In (1) or (2) above, the cemented carbide further comprises a third hard phase, the third hard phase consisting of at least one second compound selected from the group consisting of TiWNbC, TiWNbN, TiWNbCN, TiWTaC, TiWTaN, TiWTaCN, TiTaWNbC, TiTaWNbN, and TiTaWNbCN, and the content of the third hard phase in the cemented carbide may be 0.1 volume% or more and 5 volume% or less. When the content of the third hard phase in the cemented carbide is 0.1 volume% or more, the fracture toughness is improved. When the content of the third hard phase in the cemented carbide is 5 volume% or less, the strength is improved.

[0015] (4) In (3) above, the 50% cumulative particle size D50 of the third hard phase based on area (hereinafter also referred to as "D50 of the third hard phase") may be 0.1 μm or more and 3.0 μm or less. When the D50 of the third hard phase is 0.1 μm or more, fracture toughness is improved. When the D50 of the third hard phase is 3.0 μm or less, strength is improved.

[0016] (5) The cutting tool of this disclosure is a cutting tool having an cutting edge made of any of the cemented carbide alloys described in (1) to (4) above. The cutting tool of this disclosure can have a long service life even when used for finishing Inconel and precision machining of stainless steel.

[0017] [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.

[0018] 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.

[0019] 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.

[0020] In this disclosure, if one or more numerical values ​​are listed as the lower limit and upper limit 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.

[0021] 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.

[0022] [Embodiment 1: Carbide Alloy] A carbide alloy according to one embodiment of the present disclosure (hereinafter also referred to as "Embodiment 1") is a carbide alloy comprising a first hard phase, a second hard phase, and a binder phase, wherein the first hard phase consists of a plurality of tungsten carbide particles, the second hard phase consists of at least one first compound selected from the group consisting of TiNbC, TiNbN, TiNbCN, TiTaC, TiTaN, TiTaCN, TiTaNbC, TiTaNbN, and TiTaNbCN, the binder phase contains 50% by mass or more of cobalt, the total content of the first hard phase, the second hard phase, and the binder phase of the carbide alloy is 94% by volume or more, and the content of the first hard phase of the carbide alloy is The cemented carbide alloy has a composition of 65.0% to 95.0% by volume, a content of the second hard phase of the cemented carbide alloy of 0.1% to 5.0% by volume, a content of the binder phase of the cemented carbide alloy of 4.0% to 25.0% by volume, a standard deviation (sd) of the volume-based particle size distribution of tungsten carbide particles with Heywood diameter of 0.25 μm to 0.50 μm, a percentage of the number of second hard phases with a diameter of 0.2 μm or less relative to the total number of second hard phases of 0.2 μm or less of 1% to 10%, and a percentage of the number of second hard phases with a diameter of 0.8 μm or more relative to the total number of second hard phases of 0.8 μm or more of 1% to 10%.

[0023] <Composition of the cemented carbide> The cemented carbide of Embodiment 1 comprises a first hard phase, a second hard phase, and a binder phase. The total content of the first hard phase, the second hard phase, and the binder phase of the cemented carbide is 94 volume% or more, and may be 94 volume% to 100 volume%, 94.5 volume% to 99.4 volume%, 96.0 volume% to 99.0 volume%, or 97.0 volume% to 98.5 volume%.

[0024] The content fraction of the first hard phase of the cemented carbide of Embodiment 1 is 65.0% by volume or more and 95.0% by volume or less, may be 66.0% by volume or more and 94.5% by volume or less, may be 70.0% by volume or more and 92.0% by volume or less, or may be 80.0% by volume or more and 90.0% by volume or less.

[0025] The content fraction of the second hard phase of the cemented carbide of Embodiment 1 is 0.1% by volume or more and 5.0% by volume or less, may be 0.2% by volume or more and 4.8% by volume or less, may be 0.5% by volume or more and 4.0% by volume or less, or may be 0.7% by volume or more and 3.0% by volume or less.

[0026] The content fraction of the binder phase of the cemented carbide of Embodiment 1 is 4.0% by volume or more and 25.0% by volume or less, may be 7.0% by volume or more and 20.0% by volume or less, or may be 10.0% by volume or more and 18.0% by volume or less.

[0027] In addition to the first hard phase, the second hard phase, and the binder phase, the cemented carbide of Embodiment 1 may further include a third hard phase. The third hard phase is composed of at least one second compound selected from the group consisting of TiWNbC, TiWNbN, TiWNbCN, TiWTaC, TiWTaN, TiWTaCN, TiTaWNbC, TiTaWNbN, and TiTaWNbCN.

[0028] The content fraction of the third hard phase of the cemented carbide of Embodiment 1 may be 0.1% by volume or more and 5% by volume or less, may be 0.2% by volume or more and 4.9% by volume or less, may be 0.4% by volume or more and 4.0% by volume or less, or may be 0.5% by volume or more and 3.5% by volume or less.

[0029] The cemented carbide of Embodiment 1 may be composed of the first hard phase, the second hard phase, and the binder phase. Within a range that does not impair the effects of the present disclosure, the cemented carbide of Embodiment 1 may be composed of the first hard phase, the second hard phase, the binder phase, and impurities. The cemented carbide of Embodiment 1 may be composed of the first hard phase, the second hard phase, the binder phase, and the third hard phase. Within a range that does not impair the effects of the present disclosure, the cemented carbide of Embodiment 1 may be composed of the first hard phase, the second hard phase, the binder phase, the third hard phase, and impurities.

[0030] 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.

[0031] The methods for measuring the content of the first hard phase, the second hard phase, the binder phase, and the third hard phase of cemented carbide are as follows: (A1) Cut out a section of cemented carbide at an arbitrary position to expose the cross-section. Polish the cross-section to a mirror finish using a cross-section polisher (manufactured by JEOL Ltd.).

[0032] (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.

[0033] (C1) The backscattered electron image obtained in (B1) above is imported into a computer and binarized using image analysis software (ImageJ ver. 1.51J8). In the image after binarization, the first region consisting of the first hard phase and the second region consisting of the bonded phase, second hard phase, and third hard phase can be distinguished by the intensity of the colors. For example, in the image after binarization, the first region (first hard phase) is shown in black, and the second region (bonded phase, second hard phase, and third hard phase) is shown in white.

[0034] (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.

[0035] (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, second hard phase, bonding phase, and third hard phase exist are identified on the binarized image.

[0036] In the binarized image, the regions shown in black, and the regions where tungsten (W) and carbon (C) are present in the elemental mapping image, correspond to the regions where the first hard phase is present.

[0037] In the binarized image, the region shown in white, where cobalt (Co) is present in the elemental mapping image, corresponds to the region where the bonding phase is present.

[0038] In the image after binarization, the region shown in white, where at least one first compound selected from the group consisting of TiNbC, TiNbN, TiNbCN, TiTaC, TiTaN, TiTaCN, TiTaNbC, TiTaNbN, and TiTaNbCN is present in the elemental mapping image, corresponds to the region where the second hard phase exists.

[0039] In the binarized image, the region shown in white, where at least one second compound selected from the group consisting of TiWNbC, TiWNbN, TiWNbCN, TiWTaC, TiWTaN, TiWTaCN, TiTaWNbC, TiTaWNbN, and TiTaWNbCN is present, corresponds to the region where the third hard phase is present.

[0040] (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, the second hard phase, and the third hard phase are measured, with the total area of ​​the measurement field of view as the denominator.

[0041] (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 second hard phase in the five measurement fields corresponds to the content (volume %) of the second 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 third hard phase in the five measurement fields corresponds to the content (volume %) of the third hard phase in the cemented carbide.

[0042] 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.

[0043] <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. The tungsten carbide particles include not only "pure WC particles (WC that does 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).

[0044] ≪Standard deviation sd in the particle size distribution of tungsten carbide particles based on volume of Heywood diameter≫ In the cemented carbide of Embodiment 1, the standard deviation sd in the particle size distribution of tungsten carbide particles based on volume of Heywood diameter is 0.25 μm or more and 0.50 μm or less, and may also be 0.26 μm or more and 0.48 μm or less, 0.30 μm or more and 0.45 μm or less, or 0.33 μm or more and 0.43 μm or less.

[0045] <Volume average diameter mv of tungsten carbide particles> In the cemented carbide of Embodiment 1, the volume average diameter mv of the tungsten carbide particles may be 0.2 μm or more and 0.65 μm or less, 0.21 μm or more and 0.64 μm or less, 0.30 μm or more and 0.50 μm or less, or 0.30 μm or more and 0.40 μm or less.

[0046] In this disclosure, the standard deviation (sd) of the volume-based particle size distribution of tungsten carbide particles in cemented carbide, and the method for measuring the volume-average diameter (mv) of tungsten carbide particles are as follows.

[0047] (A2) Using the same method as (A1) to (E1) for measuring the content of the first hard phase of the cemented carbide described above, the region where the first hard phase exists is identified in the binarized image.

[0048] (B2) Five binarized images in which the region of the first hard phase is identified are prepared, and a rectangular measurement field of view of 40.3 μm vertically × 30.2 μm horizontally is set in each image. Using image analysis software ("Mac-View Version 5" (trademark) from Mounttech), the Heywood diameter (equivalent diameter of the projected area circle) of tungsten carbide particles in the measurement field of view is measured, and based on this, the standard deviation sd of the volume-based particle size distribution of the Heywood diameter of tungsten carbide particles and the volume-average diameter mv of tungsten carbide particles in the measurement field of view are calculated. The Mac-View settings are non-spherical, detection sensitivity 20, and detection accuracy 0.7.

[0049] (C2) The average of the standard deviations (sd) in the volume-based particle size distribution of tungsten carbide particles by Heywood diameter in the five measurement fields is calculated. In this disclosure, the average corresponds to the standard deviation (sd) in the volume-based particle size distribution of tungsten carbide particles by Heywood diameter.

[0050] The average of the volume-average diameter mv of tungsten carbide particles in five measurement fields is calculated. In this disclosure, this average corresponds to the volume-average diameter mv of the tungsten carbide particles.

[0051] 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.

[0052] <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, TiNbCN, TiTaC, TiTaN, TiTaCN, TiTaNbC, TiTaNbN, and TiTaNbCN. In the first compound, the ratio of the total number of Ti, Nb, and Ta atoms to the total number of C and N atoms is not limited to 1:1, and may include conventionally known ratios as long as they do not impair the effects of the present disclosure.

[0053] The second hard phase may contain metallic elements such as chromium (Cr), vanadium (V), and cobalt (Co) to the extent that it does not impair the effects of the present disclosure. The total content of 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 Cr and Co in the second hard phase is measured by STEM-EDX.

[0054] <<Grain Size Distribution of the Second Hard Phase>> In the cemented carbide of Embodiment 1, the percentage of the number of second hard phases with a diameter of 0.2 μm or less relative to the total number of second hard phases is 1% or more and 10% or less, and the percentage of the number of second hard phases with a diameter of 0.8 μm or more relative to the total number of second hard phases is 1% or more and 10% or less.

[0055] In the cemented carbide of Embodiment 1, the percentage of the number of second hard phases with a diameter of 0.2 μm or less relative to the total number of second hard phases may be 2% or more and 8% or 3% or more and 7% or less. In the cemented carbide of Embodiment 1, the percentage of the number of second hard phases with a diameter of 0.8 μm or more relative to the total number of second hard phases may be 3% or more and 8% or 4% or more and 7% or less. The percentage of the number of second hard phases with a diameter of 0.2 μm or less and the percentage of the number of second hard phases with a diameter of 0.8 μm or more can be combined as appropriate.

[0056] In this disclosure, the method for measuring the grain size distribution of the second hard phase in cemented carbide is as follows.

[0057] (A3) Cut out a section of the 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.).

[0058] (B3) The mirror-finished surface of the cemented carbide is analyzed using SEM-EDX (instrument: Carl Zeiss Gemini 450™) to obtain an elemental mapping image. In the elemental mapping image, a second hard phase consisting of at least one first compound selected from the group consisting of TiNbC, TiNbN, TiNbCN, TiTaC, TiTaN, TiTaCN, TiTaNbC, TiTaNbN, and TiTaNbCN is identified.

[0059] (C3) In the elemental mapping image, an area of ​​20,000 μm² ２ Furthermore, set the measurement field of view such that the number of second hard phases is 500 or more.

[0060] (D3) The elemental mapping image is imported into a computer, and the measurement field is analyzed using microscope imaging software (LEICA Microsystems' "LAS X 2D Analysis" trademark) to measure the particle size distribution of the second hard phase based on the number of Heywood diameter particles. In the analysis, threshold adjustment is performed by a filter processing process pre-installed in the microscope imaging software. The filter processing conditions may be, for example, a color range of H0-357, S90-255, and I0-110.

[0061] Based on the obtained particle size distribution of the second hard phase, the percentage of the second hard phase with a diameter of 0.2 μm or less relative to the total number of second hard phases, and the percentage of the second hard phase with a diameter of 0.8 μm or more relative to the total number of second hard phases are calculated.

[0062] 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.

[0063] In the cemented carbide of Embodiment 1, the second hard phase consists of a plurality of crystal grains. Examples of crystal grains include first compound particles made of one first compound selected from the group consisting of TiNbC, TiNbN, TiNbCN, TiTaC, TiTaN, TiTaCN, TiTaNbC, TiTaNbN, and TiTaNbCN, and first compound particles made of two or more first compounds. The second hard phase can also be described as consisting of a plurality of first compound particles. In this disclosure, the grain size distribution of the second hard phase is synonymous with the grain size distribution of the plurality of crystal grains constituting the second hard phase and the grain size distribution of the first compound particles.

[0064] <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.

[0065] The method for measuring the cobalt content of the binder phase is as follows: An elemental mapping image and a binarized image are acquired using the same method as (A1) to (E1) of the method for measuring the content of the first hard phase of the cemented carbide described above. 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.

[0066] 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.

[0067] In the cemented carbide of Embodiment 1, the bonding phase may further include a first element selected from the group consisting of iron (Fe), nickel (Ni), chromium (Cr), vanadium (V), titanium (Ti), niobium (Nb), and tantalum (Ta), to the extent that it does not impair the effects of the present disclosure. The bonding phase may consist of cobalt and the first element.

[0068] <Third Hard Phase> <Composition> In Embodiment 1, the third hard phase consists of at least one second compound selected from the group consisting of TiWNbC, TiWNbN, TiWNbCN, TiWTaC, TiWTaN, TiWTaCN, TiTaWNbC, TiTaWNbN, and TiTaWNbCN. In the second compound, the ratio of the total number of atoms of Ti, W, Nb, and Ta to the total number of atoms of C and N is not limited to 1:1, and may include conventionally known ratios as long as they do not impair the effects of the present disclosure.

[0069] The third hard phase may contain metallic elements such as chromium (Cr), vanadium (V), and cobalt (Co) to the extent that it does not impair the effects of the present disclosure. The total content of Cr and Co in the third hard phase may be 0% by mass or more and less than 0.1% by mass. The content of Cr and Co in the third hard phase is measured by STEM-EDX.

[0070] ≪50% cumulative particle size D50 based on area of ​​the third hard phase≫ In the cemented carbide of Embodiment 1, the 50% cumulative particle size D50 based on area of ​​the third hard phase is 0.1 μm or more and 3.0 μm or less, and may be 0.2 μm or more and 2.9 μm or less, 0.4 μm or more and 2.2 μm or less, or 0.5 μm or more and 2.0 μm or less.

[0071] In this disclosure, the method for measuring the 50% cumulative particle size D50 of the third hard phase in cemented carbide based on area is as follows:

[0072] (A4) Cut out a section of the 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.).

[0073] (B4) The mirror-finished surface of the cemented carbide is analyzed using SEM-EDX (instrument: Carl Zeiss Gemini 450™) to obtain an elemental mapping image. In the elemental mapping image, a third hard phase consisting of at least one second compound selected from the group consisting of TiWNbC, TiWNbN, TiWNbCN, TiWTaC, TiWTaN, TiWTaCN, TiTaWNbC, TiTaWNbN, and TiTaWNbCN is identified.

[0074] (C4) Prepare 10 elemental mapping images in which the third hard phase has been identified, and set a rectangular measurement field of view of 4.0 μm in height × 3.0 μm in width within each elemental mapping image.

[0075] (D4) The elemental mapping image is imported into a computer, and the measurement field is analyzed using microscope imaging software (LEICA Microsystems' "LAS X 2D Analysis" trademark) to measure the Heywood diameter (equivalent diameter of projected area circle) of the third hard phase in the measurement field.

[0076] (E4) Based on all of the third hard phase in the measurement field of view of 10, the 50% cumulative particle size D50 of the third hard phase on an area basis of the Heywood diameter is calculated.

[0077] 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.

[0078] In the cemented carbide of Embodiment 1, the third hard phase is composed of a plurality of crystal grains. Examples of the crystal grains include second compound particles composed of one type of second compound selected from the group consisting of TiWNbC, TiWNbN, TiWNbCN, TiWTaC, TiWTaN, TiWTaCN, TiTaWNbC, TiTaWNbN, and TiTaWNbCN, and second compound particles composed of two or more types of second compounds. The third hard phase can also be expressed as being composed of a plurality of second compound particles. In the present disclosure, the 50% cumulative particle size D50 based on the area of the Heywood diameter of the third hard phase is synonymous with the 50% cumulative particle size D50 based on the area of the Heywood diameter of the plurality of crystal grains constituting the third hard phase and the 50% cumulative particle size D50 based on the area of the Heywood diameter of the second compound particles.

[0079] <Method for manufacturing cemented carbide> The cemented carbide of Embodiment 1 can be manufactured by performing the steps of preparing raw material powder, mixing, molding, sintering, and HIP in this order. Each step will be described below.

[0080] <Preparation step> The preparation step is a step of preparing raw materials for the materials constituting the cemented carbide. Examples of the raw materials include tungsten metal powder (hereinafter also referred to as "W powder"), carbon powder (hereinafter also referred to as "C powder"), Co powder (average particle size 1 μm), TaC powder (average particle size 1 μm), TiO ２ powder, and Nb ２ O ５ powder.

[0081] First, tungsten carbide powder is produced by the following procedure. The W powder, C powder, and TiO ２ powder are strongly mixed using a dry attritor, and then weakly mixed using a wet ball mill to obtain a mixed powder. When using Nb ２ O ５ powder as a raw material, the Nb ２ O ５ powder is also mixed simultaneously. The mixing conditions of the dry attritor are: super hard media diameter: 3 mm, rotation speed: 40 rpm, mixing time: 1 hour. The mixing conditions of the wet ball mill are: super hard media diameter: 6 mm, rotation speed 30 rpm, mixing time: 6 hours.

[0082] The mixed powder is placed in a batch furnace and heated at 1500°C for 2 hours under a vacuum atmosphere. After heating, the mixed powder is crushed in a dry ball mill to obtain tungsten carbide powder. The conditions for the dry ball mill are: carbide media diameter: 6 mm, rotation speed: 5 rpm, crushing time: 2 hours.

[0083] TiO ２ Using powder, Nb ２ O ５ If no powder is used, the resulting tungsten carbide powder is Ti-added tungsten carbide powder. The raw material is TiO ２ Powder and Nb ２ O ５ When powder is used, the resulting tungsten carbide powder is TiNb-added tungsten carbide powder, in which Ti and Nb are added.

[0084] As raw material powders, further Ni powder, VC powder, and Cr ３ C ２ Powders and other materials 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.

[0085] 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.

[0086] <Mixing Process> The mixing process involves mixing the raw materials (including WC powder) prepared in the preparation process in predetermined proportions to obtain a mixture. The mixing ratio of the raw materials is adjusted as appropriate according to the desired composition of the cemented carbide.

[0087] An attritor is used to mix the raw materials. The mixing conditions are a rotation speed of 200 rpm, a ball diameter of φ6 mm, and a mixing time of 12 hours.

[0088] After the mixing process, the mixture may be granulated if necessary. Granulating the mixture makes it easier to fill the die or mold during the molding process described later. Known granulation methods can be applied, and commercially available granulators such as spray dryers can be used.

[0089] <Molding Process> The molding process is the process of molding the mixture obtained in the mixing process into a shape for 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.

[0090] <Sintering Process> The sintering process is a process in which the molded body obtained in the molding process is sintered to obtain a cemented carbide intermediate. The molded body is placed in a furnace and sintered in an Ar atmosphere and at a pressure of 6.7 kPa, or N ２ The material is heated to 1250°C in an atmosphere and under a pressure of 30 kPa or 6.7 kPa, at a heating rate of 5°C / min, and held at 1250°C for 2 hours. Subsequently, it is heated to 1500°C at a heating rate of 5°C / min and held at 1500°C for 2 hours. Then, the molded body is cooled to 25°C at a cooling rate of -50°C / min to obtain a cemented carbide intermediate.

[0091] <HIP Process> In the HIP process, the cemented carbide intermediate is subjected to HIP. The HIP conditions are an Ar atmosphere, 200 MPa, and holding at 1100°C for 2 hours. After that, it is cooled to obtain the cemented carbide of Embodiment 1. Conventional known cooling conditions can be used.

[0092] <Characteristics of the Method for Manufacturing Carbide of Embodiment 1> In the method for manufacturing carbide of Embodiment 1, Ti-added tungsten carbide powder or TiNb-added tungsten carbide powder is used. With this, during the manufacturing of carbide, Ti, or Ti and Nb react uniformly, and the second hard phase containing Ti, or the second hard phase containing Ti and Nb, tends to grow uniformly, resulting in a sharp grain size distribution of the second hard phase. In conventional general methods for manufacturing carbide, Ti-added tungsten carbide powder or TiNb-added tungsten carbide powder is not used, so it is not possible to achieve a grain size distribution of the second hard phase such that the percentage of the second hard phase with a diameter of 0.2 μm or less relative to the total number of second hard phases is 1% or more and 10% or less, and the percentage of the second hard phase with a diameter of 0.8 μm or more relative to the total number of second hard phases is 1% or more and 10% or less.

[0093] In the mixing step of the cemented carbide manufacturing method of Embodiment 1, the raw materials are mixed using a high-speed attritor. This tends to result in a broad particle size distribution of WC particles.

[0094] In the sintering step of the cemented carbide manufacturing method of Embodiment 1, the material is heated to 1250°C at a heating rate of 5°C / min and held at 1250°C for 2 hours. Subsequently, it is heated to 1500°C at a heating rate of 5°C / min and held at 1500°C for 2 hours. By performing sintering in two stages, grain growth of the second hard phase is suppressed, and the grain size distribution of the second hard phase containing Ti and Nb tends to become sharper. Furthermore, by holding at 1500°C for 2 hours, WC particles grow, and the grain size distribution of WC particles tends to become broader.

[0095] The inventors have discovered, through diligent research, that the cemented carbide described herein can be realized by adopting the manufacturing process described above.

[0096] [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.

[0097] 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. The cutting tool 10 of Embodiment 2 can exhibit excellent effects in particular in the case of an end mill as shown in Figure 1 and a replaceable cutting tip as shown in Figure 2. The cutting edge 11 of the cutting tool 10 shown in Figures 1 and 2 is made of the cemented carbide of Embodiment 1.

[0098] 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.

[0099] 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.

[0100] The cutting tool of Embodiment 2 can be obtained by shaping the cemented carbide of Embodiment 1 into a desired shape.

[0101] This embodiment will be described in more detail by reference to examples. However, this embodiment is not limited by these examples.

[0102] <Preparation Process> As raw materials, metal tungsten powder (hereinafter also referred to as "W powder"), carbon powder (hereinafter also referred to as "C powder"), Co powder (average particle size 1 μm), TaC powder, TiO ２ powder, Nb ２ O ５ Powder, Ni powder, VC powder, and Cr ３ C ２ I prepared the powders: TaC powder, TiO ２ powder, Nb ２ O ５ Powder, Ni powder, VC powder, and Cr ３ C ２ The average particle size of the powder is 1 μm.

[0103] First, tungsten carbide powder was prepared using the following procedure: W powder, C powder, and TiO ２ The powder was strongly mixed using a dry attritor, and then weakly mixed using a wet ball mill to obtain a mixed powder. Nb was used as the raw material. ２ O ５ When using powder, Nb ２ O ５ The powder was also mixed at the same time. TiO in the mixed powder ２ Powder, and Nb ２ O ５ The amount of powder was adjusted to the proportions shown in Table 1. Samples 1-6 consisted of a mixture of only W powder and C powder. The amounts of W powder and C powder in the mixed powder were adjusted to a ratio of W powder:C powder = 14:1 (mass ratio). The mixing conditions for the dry attritor were: carbide media diameter: 3 mm, rotation speed: 40 rpm, mixing time: 1 hour. The mixing conditions for the wet ball mill were: carbide media diameter: 6 mm, rotation speed: 30 rpm, mixing time: 6 hours.

[0104] The mixed powder was placed in a batch furnace and heated at 1500°C for 2 hours under a vacuum atmosphere. After heating, the mixed powder was crushed in a dry ball mill to obtain tungsten carbide powder. The conditions for the dry ball mill were: carbide media diameter: 6 mm, rotation speed: 5 rpm, crushing time: 2 hours.

[0105] <Mixing Process> The raw materials were mixed in the proportions listed in "Raw Materials (mass%)" in Table 1. The proportion (mass%) of each raw material listed in Table 1 is the proportion when the total raw materials are considered to be 100 mass%. "Remainder" in Table 1 indicates that the proportion of WC powder is the value obtained by subtracting the total proportion of other raw materials from 100 mass% of the total raw materials. "-" in Table 1 indicates that the corresponding raw material was not used. The mixing conditions are as follows: B or C. Condition B is the conventional general mixing condition. 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. C: An attritor is used. The mixing conditions are a rotation speed of 200 rpm, a ball diameter of φ6 mm, and a mixing time of 12 hours.

[0106]

[0107] <Molding Process> By pressing the mixed powder, a round bar-shaped molded body and a molded body in the shape of an interchangeable cutting tip (model number: DCGT11T302MN-FC) were obtained.

[0108] <Sintering Process> The molded body is placed in the furnace and sintered under the conditions described in the "Atmosphere / Pressure" column of "Sintering" in Table 2 ("Ar-6.7kPa" means argon atmosphere and pressure of 6.7kPa). ２ -30kPa is N ２ This refers to an atmosphere with a pressure of 30 kPa. ２ -6.7 kPa is N ２ The atmosphere and pressure are 6.7 kPa. The material was heated to the temperature indicated in the "First Stage Temperature / Time" column of Table 2 at the heating rate indicated in the "Heating Rate" column of Table 2, and held at that temperature for the time indicated in the "First Stage Temperature / Time" column. The material was then heated to the temperature indicated in the "Second Stage Temperature / Time" column of Table 2 at the heating rate indicated in the "Heating Rate" column of Table 2, and held at that temperature for the time indicated in the "Second Stage Temperature / Time" column. For samples where "-" is indicated in the "First Stage Temperature / Time" column, sintering under the conditions of the first stage was not performed, and only sintering under the conditions of the second stage was performed. 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.

[0109]

[0110] <HIP Process> The cemented carbide intermediate was subjected to HIP under the conditions described in the "HIP" column of Table 3. After that, it was cooled to obtain the cemented carbide.

[0111]

[0112] [Evaluation of cemented carbide] <Content of first hard phase, content of binder phase, content of second hard phase, and content of third hard phase 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 %), and the content of the third hard phase (volume %) of cemented carbide for each sample was measured using the method described in Embodiment 1. The results are shown in Table 4.

[0113]

[0114] <Standard deviation (sd) of the volume-based particle size distribution of tungsten carbide particles by Heywood diameter, volume-average diameter (mv) of tungsten carbide particles, composition of the second hard phase, and particle size distribution of the second hard phase> For each cemented carbide sample, the standard deviation (sd) of the volume-based particle size distribution of tungsten carbide particles by Heywood diameter, volume-average diameter (mv) of tungsten carbide particles, composition of the second hard phase, and particle size distribution of the second hard phase were measured using the method described in Embodiment 1. The results are shown in Table 5. In Table 5, the column "Diameter 0.2 μm or less" shows the percentage of the number of second hard phase particles with a diameter of 0.2 μm or less relative to the total number of second hard phase particles. In Table 5, the column "Diameter 0.8 μm or more" shows the percentage of the number of second hard phase particles with a diameter of 0.8 μm or more relative to the total number of second hard phase particles.

[0115]

[0116] <Cobalt content of the binder phase, composition of the third hard phase, and 50% cumulative particle size D50 of the third hard phase based on area> For each cemented carbide sample, the cobalt content of the binder phase, the composition of the third hard phase, and the 50% cumulative particle size D50 of the third hard phase based on area were measured using the method described in Embodiment 1. The results are shown in Table 6.

[0117]

[0118] [Cutting Test 1] Round bars made of cemented carbide for each sample were machined to create ball end mills with a cutting diameter of φ6 mm. Inconel 718 was finished using the ball end mills. The machining conditions were: cutting speed Vc 50 m / min, feed per tooth fz 0.05 mm / tooth, depth of cut (axial) ap 0.2 mm, depth of cut (radial) ae 0.1 mm, and wet machining. The cutting length until surface deterioration occurred was measured. The results are shown in the "Cutting Length" column of "Cutting Test 1" in Table 7. If the cutting length is 30 m or more, it is judged that the tool life is long. Note that the above machining conditions correspond to the finishing of Inconel.

[0119] [Cutting Test 2] SUS304 was finished using replaceable cutting tips (model number: DCGT11T302MN-FC) made of cemented carbide for each sample. The machining conditions were: cutting speed Vc 150 m / min, feed rate f 0.05 mm / tooth, depth of cut ap 0.05 mm, and wet cutting. The cutting length until surface deterioration occurred was measured. The results are shown in the "Cutting Length" column of "Cutting Test 2" in Table 7. If the cutting length is 100 m or more, the tool life is considered to be long. Note that the above machining conditions are applicable to precision machining of stainless steel.

[0120]

[0121] The cemented carbide alloys and cutting tools of Samples 1 to 10 correspond to the examples. These cutting tools were confirmed to have long tool life in cutting tests 1 and 2.

[0122] The cemented carbide alloys and cutting tools of Samples 1-1 to 1-7 are comparative examples. These cutting tools exhibited insufficient tool life in cutting tests 1 and 2.

[0123] 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 scope of the claims are intended to be included in the meaning of equivalences.

[0124] 10 Cutting tool, 11 Cutting edge.

Claims

A cemented carbide comprising a first hard phase, a second hard phase, and a binder phase, The first hard phase consists of a plurality of tungsten carbide particles. The second hard phase consists of at least one first compound selected from the group consisting of TiNbC, TiNbN, TiNbCN, TiTaC, TiTaN, TiTaCN, TiTaNbC, TiTaNbN, and TiTaNbCN. The aforementioned bonding phase contains 50% by mass or more of cobalt, The total content of the first hard phase, the second hard phase, and the binder phase of the cemented carbide is 94% by volume or more. The content of the first hard phase in the cemented carbide is 65.0% by volume or more and 95.0% by volume or less. The content of the second hard phase in the cemented carbide is 0.1% by volume or more and 5.0% by volume or less. The content of the binder phase in the cemented carbide is 4.0% by volume or more and 25.0% by volume or less. The standard deviation (sd) of the particle size distribution based on volume of the Heywood diameter of the tungsten carbide particles is 0.25 μm or more and 0.50 μm or less. The percentage of the number of second hard phases with a diameter of 0.2 μm or less relative to the total number of second hard phases is 1% or more and 10% or less. A cemented carbide alloy in which the percentage of the number of second hard phases with a diameter of 0.8 μm or more relative to the total number of the second hard phases is 1% or more and 10% or less. 　 The cemented carbide according to claim 1, wherein the volume-average diameter mv of the tungsten carbide particles is 0.2 μm or more and 0.65 μm or less. 　 The cemented carbide further comprises a third hard phase, The third hard phase consists of at least one second compound selected from the group consisting of TiWNbC, TiWNbN, TiWNbCN, TiWTaC, TiWTaN, TiWTaCN, TiTaWNbC, TiTaWNbN, and TiTaWNbCN. The cemented carbide alloy according to claim 1 or claim 2, wherein the content of the third hard phase in the cemented carbide alloy is 0.1 volume% or more and 5 volume% or less. 　 The cemented carbide according to claim 3, wherein the 50% cumulative particle size D50 of the third hard phase, based on area, is 0.1 μm or more and 3.0 μm or less. 　 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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