Cemented carbide and tool comprising the same

Abstract

A cemented carbide comprising a first hard phase, a second hard phase, and a bonding phase, wherein the first hard phase is composed of tungsten carbide particles, the second hard phase is composed of at least one first compound selected from the group consisting of TiNbC, TiNbN, and TiNbCN, the average particle size of the second hard phase is less than 0.1 μm, the dispersion of the second hard phase is less than 0.7, and the content of the second hard phase is more than 0.1 vol% and less than 15 vol%, the bonding phase comprising at least one first element selected from the group consisting of iron, cobalt, and nickel, and the content of the bonding phase is more than 0.1 vol% and less than 20 vol%.

Description

Technical Field

[0001] This disclosure relates to cemented carbide and tools comprising the cemented carbide. Background Technology

[0002] Previously, cemented carbide, which has a phase mainly composed of tungsten carbide (WC), a phase composed of carbides, nitrides and carbonitrides containing metal elements other than tungsten, and a combined phase mainly composed of iron group elements, has been used as raw material for cutting tools (Patent Documents 1 to 5).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: International Publication No. 2017 / 191744

[0006] Patent Document 2: Japanese Patent Application Publication No. 2012-251242

[0007] Patent Document 3: International Publication No. 2018 / 194018

[0008] Patent Document 4: Japanese Patent Application Publication No. 2016-98393

[0009] Patent Document 5: Japanese Patent Application Publication No. 2021-110010 Summary of the Invention

[0010] The cemented carbide disclosed herein is a cemented carbide composed of a first hard phase, a second hard phase, and a bonding phase, wherein,

[0011] The first hard phase is composed of tungsten carbide particles.

[0012] The second hard phase is composed of at least one first compound selected from the group consisting of TiNbC, TiNbN, and TiNbCN.

[0013] The average particle size of the second hard phase is less than 0.1 μm.

[0014] The dispersion of the second hard phase is below 0.7.

[0015] The content of the second hard phase is 0.1% by volume or more and 15% by volume or less.

[0016] The bonding phase comprises at least one first element selected from the group consisting of iron, cobalt, and nickel.

[0017] The content of the bound phase is more than 0.1% by volume and less than 20% by volume.

[0018] The cemented carbide disclosed herein is a cemented carbide composed of a first hard phase, a third hard phase, and a bonding phase, wherein,

[0019] The first hard phase is composed of tungsten carbide particles.

[0020] The third hard phase is composed of at least one second compound selected from the group consisting of TiTaC, TiTaN, and TiTaCN.

[0021] The average particle size of the third hard phase is less than 0.1 μm.

[0022] The dispersion of the third hard phase is below 0.7.

[0023] The content of the third hard phase is more than 0.1% by volume and less than 15% by volume.

[0024] The bonding phase comprises at least one first element selected from the group consisting of iron, cobalt, and nickel.

[0025] The content of the bound phase is more than 0.1% by volume and less than 20% by volume.

[0026] The tools disclosed herein are tools comprising the aforementioned cemented carbide. Attached Figure Description

[0027] Figure 1 This is an example of a reflected electron image of a cemented carbide according to Embodiment 1.

[0028] Figure 2 This is an example of a STEM-HAADF image of a cemented carbide according to Embodiment 1.

[0029] Figure 3 This is an elemental mapping image of the cemented carbide according to Embodiment 1.

[0030] Figure 4 Based on Figure 1 The Vinno diagram is created from the reflected electron image shown.

[0031] Figure 5 This is an example of a STEM-HAADF image of a cemented carbide according to Embodiment 2.

[0032] Figure 6 This is an elemental mapping image of the cemented carbide according to Embodiment 2.

[0033] Figure 7 This is a photographic representation of an adhesion substance on a cemented carbide surface. Detailed Implementation

[0034] [The problem this disclosure aims to solve]

[0035] In recent years, the requirements for cost reduction have become increasingly stringent. For example, in the high-efficiency machining of difficult-to-machine materials such as titanium alloys and nickel alloys, tools with long service life are also required. Therefore, the object of this disclosure is to provide a cemented carbide that enables long tool life when used as a tool material, and a tool comprising the cemented carbide.

[0036] [The Effects of This Disclosure]

[0037] Tools incorporating the cemented carbide disclosed herein can have a longer tool life.

[0038] [Description of embodiments of this disclosure]

[0039] First, embodiments of this disclosure will be described.

[0040] (1) The cemented carbide disclosed herein is a cemented carbide composed of a first hard phase, a second hard phase, and a bonding phase, wherein,

[0041] The first hard phase is composed of tungsten carbide particles.

[0042] The second hard phase is composed of at least one first compound selected from the group consisting of TiNbC, TiNbN, and TiNbCN.

[0043] The average particle size of the second hard phase is less than 0.1 μm.

[0044] The dispersion of the second hard phase is below 0.7.

[0045] The content of the second hard phase is 0.1% by volume or more and 15% by volume or less.

[0046] The bonding phase comprises at least one first element selected from the group consisting of iron, cobalt, and nickel.

[0047] The content of the bound phase is more than 0.1% by volume and less than 20% by volume.

[0048] Tools incorporating the cemented carbide disclosed herein can have a longer tool life.

[0049] (2) Preferably, in a rectangular field of view of 24.9 μm × 18.8 μm set in the binarized image of the reflected electron image obtained by taking a cross-section of the cemented carbide using a scanning electron microscope, the number of the second hard phase is 30 or more. This improves the cemented carbide's resistance to caulking.

[0050] (3) Preferably, the average particle size of the second hard phase is 0.01 μm or more and 0.08 μm or less. As a result, the cemented carbide's resistance to caulking is improved.

[0051] (4) Preferably, the dispersion of the second hard phase is 0.4 or less. As a result, the cemented carbide's resistance to caulking is improved.

[0052] (5) Preferably, the dispersion is the standard deviation of the area of ​​each Vino region in the Vino diagram obtained by dividing the Vino map using the centroid of the second hard phase as the parent point.

[0053] The Vino map is obtained as follows: the second hard phase is extracted from the reflected electron image obtained by taking a cross-section of the cemented carbide using a scanning electron microscope; a rectangular measurement field of 24.9 μm × 18.8 μm is set in the binarized image of the reflected electron image; the centroid of the extracted second hard phase is used as the mother point for Vino segmentation in the measurement field; and the Vino region of all the mother points is calculated.

[0054] (6) The cemented carbide of this disclosure is a cemented carbide composed of a first hard phase, a third hard phase, and a bonding phase, wherein,

[0055] The first hard phase is composed of tungsten carbide particles.

[0056] The third hard phase is composed of at least one second compound selected from the group consisting of TiTaC, TiTaN, and TiTaCN.

[0057] The average particle size of the third hard phase is less than 0.1 μm.

[0058] The dispersion of the third hard phase is below 0.7.

[0059] The content of the third hard phase is more than 0.1% by volume and less than 15% by volume.

[0060] The bonding phase comprises at least one first element selected from the group consisting of iron, cobalt, and nickel.

[0061] The content of the bound phase is more than 0.1% by volume and less than 20% by volume.

[0062] Tools incorporating the cemented carbide disclosed herein can have a longer tool life.

[0063] (7) The tool disclosed herein is a tool comprising the above-mentioned cemented carbide. The tool disclosed herein is capable of having a long tool life.

[0064] [Details of the embodiments disclosed herein]

[0065] In this specification, expressions such as "A~B" refer to the upper and lower limits of a range (i.e., above A and below B). If no unit is recorded in A but only in B, the unit of A is the same as the unit of B.

[0066] In this specification, when compounds are represented by chemical formulas, all conventionally known atomic ratios are included unless otherwise specified, and are not necessarily limited to atomic ratios within the stoichiometric range. For example, when referred to as "TiNbC", the ratio of the number of atoms constituting TiNbC includes all conventionally known atomic ratios.

[0067] In this specification, when referring to pressure, unless otherwise specified, it refers to pressure based on atmospheric pressure.

[0068] In developing tools with long tool life even in high-efficiency machining of difficult-to-cut materials, the inventors of this invention manufactured conventional cemented carbide tools for high-efficiency machining of such materials. They discovered that in conventional cemented carbide tools, tool life was reached due to the melting of the workpiece material into the tool. This was presumably due to reduced resistance to chipping and decreased dimensional accuracy caused by the melting process. Therefore, the inventors of this invention focused specifically on developing cemented carbide with resistance to melting, resulting in the cemented carbide disclosed herein and tools comprising this cemented carbide.

[0069] Hereinafter, specific examples of the cemented carbide of this disclosure and tools comprising the cemented carbide will be described with reference to the accompanying drawings. In the accompanying drawings of this disclosure, the same reference numerals denote the same or equivalent parts. In addition, dimensional relationships such as length, width, thickness, and depth have been appropriately modified for clarity and simplification of the drawings, and do not necessarily represent actual dimensional relationships.

[0070] [Implementation Method 1: Hard Alloy (1)]

[0071] One embodiment of this disclosure (hereinafter also referred to as "Embodiment 1") is a cemented carbide composed of a first hard phase, a second hard phase, and a bonding phase.

[0072] The first hard phase is composed of tungsten carbide particles.

[0073] The second hard phase is composed of at least one first compound selected from the group consisting of TiNbC, TiNbN, and TiNbCN.

[0074] The average particle size of this second hard phase is less than 0.1 μm.

[0075] The dispersion of the second hard phase is below 0.7.

[0076] The content of the second hard phase is more than 0.1% by volume and less than 15% by volume.

[0077] The bonded phase contains at least one first element selected from the group consisting of iron, cobalt, and nickel.

[0078] The content of this bound phase is above 0.1 vol% and below 20 vol%.

[0079] Tools incorporating the cemented carbide disclosed herein can have a longer tool life. This is presumably due to the excellent deposition resistance of cemented carbide.

[0080] <Composition of cemented carbide>

[0081] The cemented carbide of Embodiment 1 is composed of a first hard phase, a second hard phase, and a bonding phase. The cemented carbide may also contain impurities, provided it does not impair the effects of this disclosure. That is, the cemented carbide may be composed of a first hard phase, a second hard phase, a bonding phase, and impurities. Examples of such impurities include iron (Fe), molybdenum (Mo), calcium (Ca), silicon (Si), and sulfur (S). The impurity content of the cemented carbide (the total content of two or more impurities) is preferably 0% by mass or more and less than 0.1% by mass. The impurity content of the cemented carbide is determined by ICP-based light emission analysis (Inductively Coupled Plasma Emission Spectroscopy (measuring device: Shimadzu Corporation "ICPS-8100" (trademark)).

[0082] In Embodiment 1, the lower limit of the content of the first hard phase of the cemented carbide can be set to 65% or more by volume, 70% or more by volume, 75% or more by volume, or 80% or more by volume. The upper limit of the content of the first hard phase of the cemented carbide can be set to 99.8% or less by volume, 99% or less by volume, 98% or less by volume, or 97% or less by volume. The content of the first hard phase in cemented carbide can be set to 65% or more and 99.8% or less, 70% or more and 99.8% or less, 75% or more and 99.8% or less, 80% or more and 99.8% or less, 65% or more and 99% or less, 70% or more and 99% or less, 75% or more and 99% or less, 80% or more and 99% or less, 65% or more and 98% or less, 70% or more and 98% or less, 75% or more and 98% or less, 80% or more and 98% or less, 65% or more and 97% or less, 70% or more and 97% or less, 75% or more and 97% or less, and 80% or more and 97% or less.

[0083] In Embodiment 1, the content of the second hard phase in the cemented carbide is 0.1 vol% or more and 15 vol% or less. This improves the deposition resistance of the cemented carbide. The lower limit of the content of the second hard phase in the cemented carbide can be set to 0.10 vol% or more, 0.2 vol% or more, 0.5 vol% or more, or 1 vol% or more. The upper limit of the content of the second hard phase in the cemented carbide can be set to 15 vol% or less, 14 vol% or less, 12 vol% or less, or 10 vol% or less. The content of the second hard phase in cemented carbide can be set to 0.10 vol% or more and 15 vol% or less, 0.2 vol% or more and 15 vol% or less, 0.5 vol% or more and 15 vol% or less, 1 vol% or more and 15 vol% or less, 0.10 vol% or more and 14 vol% or less, 0.2 vol% or more and 14 vol% or less, 0.5 vol% or more and 14 vol% or less, 1 vol% or more and 14 vol% or less, 0.10 vol% or more and 12 vol% or less, 0.2 vol% or more and 12 vol% or less, 0.5 vol% or more and 1 vol% or more and 1 vol% or less, 0.10 vol% or more and 10 vol% or less, 0.2 vol% or more and 10 vol% or less, 0.5 vol% or more and 1 vol% or more and 1 vol% or more and 10 vol% or less.

[0084] In Embodiment 1, the content of the bonding phase in the cemented carbide is 0.1 vol% or more and 20 vol% or less. This increases the strength of the cemented carbide. The lower limit of the content of the bonding phase in the cemented carbide can be set to 0.10 vol% or more, 0.3 vol% or more, 0.5 vol% or more, or 1 vol% or more. The upper limit of the content of the bonding phase in the cemented carbide can be 20 vol% or less, 18 vol% or less, 16 vol% or less, or 14 vol% or less. The content of the bonding phase in the cemented carbide can be set to 0.10 vol% or more and 20 vol% or less, 0.3 vol% or more and 20 vol% or less, 0.5 vol% or more and 20 vol% or less, 1 vol% or more and 20 vol% or less, 0.10 vol% or more and 18 vol% or less, 0.3 vol% or more and 18 vol% or less, 0.5 vol% or more and 18 vol% or less, 1 vol% or more and 18 vol% or less, 0.10 vol% or more and 16 vol% or less, 0.3 vol% or more and 16 vol% or less, 0.5 vol% or more and 16 vol% or less, 1 vol% or more and 16 vol% or less, 0.10 vol% or more and 14 vol% or less, 0.3 vol% or more and 14 vol% or less, 0.5 vol% or more and 14 vol% or less, and 1 vol% or more and 14 vol% or less.

[0085] The methods for determining the content of the first hard phase, the second hard phase, and the binding phase in cemented carbide are as follows.

[0086] (A1) Cut out any position of the cemented carbide to expose the cross-section. Perform mirror finishing on the cross-section using a cross-section polishing machine (manufactured by Nippon Electronics Co., Ltd.).

[0087] (B1) The mirror-finished surface of cemented carbide was analyzed using scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) (device: Carl Zeiss Gemini 450 (trademark)) to determine the elements contained in the cemented carbide.

[0088] (C1) The mirror-finished surface of cemented carbide was photographed using a scanning electron microscope (SEM) to obtain reflected electron images. The image capture area was set in the central part of the cemented carbide cross-section, i.e., excluding areas near the surface of the cemented carbide that have significantly different properties from the bulk portion (the entire image capture area consisted of the bulk portion of the cemented carbide). The magnification was 5000x. The measurement conditions were an accelerating voltage of 3kV, a current of 2nA, and a working distance (WD) of 5mm.

[0089] (D1) For the area captured in (C1) above, an energy dispersive X-ray analyzer (SEM-EDX) with SEM attached is used to analyze the area to determine the distribution of the elements identified in (B1) above, and an element mapping image is obtained.

[0090] (E1) Import the reflected electron image obtained in (C1) above into a computer and perform binarization processing using image analysis software (OpenCV, SciPy). The binarization processing is performed by extracting only the first hard phase, the second hard phase, and the second hard phase in the binding phase from the reflected electron image. The binarization threshold varies according to the contrast, and therefore is set for each image.

[0091] Figure 1 An example of a reflected electron image of the cemented carbide according to this embodiment. Figure 1 In the image, the white areas correspond to the first hard phase, the gray areas to the bound phase, and the black areas to the second hard phase. In this reflected electron image, a binarization threshold is set to extract only the black areas.

[0092] (F1) By overlaying the elemental mapping image obtained in (D1) above with the binarized image obtained in (E1) above, the respective regions of existence of the first hard phase, the second hard phase, and the bonding phase are determined on the binarized image. Specifically, regions represented in white in the binarized image and containing tungsten (W) and carbon (C) in the elemental mapping image correspond to the regions of existence of the first hard phase. Regions represented in black in the binarized image and containing one or both of carbon (C) and nitrogen (N), as well as titanium (Ti) and niobium (Nb) in the elemental mapping image correspond to the regions of existence of the second hard phase. Regions represented in white in the binarized image and containing at least one element selected from the group consisting of iron, cobalt, and nickel correspond to the regions of existence of the bonding phase.

[0093] (G1) In the image after binarization, a rectangular field of view of 24.9 μm × 18.8 μm is defined. Using the image analysis software described above, the area percentages of the first hard phase, the second hard phase, and the binding phase are measured, with the total area of ​​the field of view as the denominator.

[0094] (H1) The above (G1) determination is performed in five distinct measurement fields. In this specification, the average area percentage of the first hard phase in the five measurement fields corresponds to the content (volume %) of the first hard phase of 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 of the cemented carbide, and the average area percentage of the binding phase in the five measurement fields corresponds to the content (volume %) of the binding phase of the cemented carbide.

[0095] The following conditions have been confirmed: as long as the measurement is within the scope of the applicant's measurement and is performed on the same sample, even if the cut-out part of the cemented carbide profile is arbitrarily set, the imaging area described in (C1) is arbitrarily set on the profile, and the five measurement fields described in (H1) are arbitrarily set, and the content of the first hard phase, the content of the second hard phase, and the content of the bonding phase of the cemented carbide are measured multiple times according to the above steps, the deviation of the measurement results is very small. Even if the cut-out part of the cemented carbide profile is arbitrarily set, the imaging area of ​​the reflected electron image is arbitrarily set, and the measurement field is arbitrarily set, the results will not change arbitrarily.

[0096] <First Hard Phase>

[0097] "composition"

[0098] In Embodiment 1, the first hard phase is composed of tungsten carbide particles (hereinafter also referred to as "WC particles"). These tungsten carbide particles (hereinafter also referred to as "WC particles") are particles composed of tungsten carbide. Without impairing the effects of this disclosure, the first hard phase may contain iron (Fe), molybdenum (Mo), calcium (Ca), silicon (Si), sulfur (S), etc., either within or together with the WC particles. The content of iron (Fe), molybdenum (Mo), calcium (Ca), silicon (Si), and sulfur (S) in the first hard phase (in the case of two or more, the total content of these elements) is preferably 0% by mass or more and less than 0.1% by mass. The content of iron (Fe), molybdenum (Mo), calcium (Ca), silicon (Si), and sulfur (S) in the first hard phase is determined by ICP-N PLC analysis.

[0099] Average particle size

[0100] In Embodiment 1, the lower limit of the average particle size of the tungsten carbide particles is preferably 0.2 μm or more and 0.4 μm or more. The upper limit of the average particle size of the tungsten carbide particles is preferably 3.0 μm or less and 2.5 μm or less. The average particle size of the tungsten carbide particles is preferably 0.2 μm or more and 3.0 μm or less, 0.4 μm or more and 3.0 μm or less, 0.2 μm or more and 2.5 μm or less, or 0.4 μm or more and 2.5 μm or less. Therefore, the cemented carbide has high hardness, and the wear resistance of tools containing this cemented carbide is improved. Furthermore, the tool can exhibit excellent resistance to breakage.

[0101] In this specification, the average particle size of tungsten carbide particles refers to the D50 of the equivalent circle diameter (Heywood diameter) of the tungsten carbide particles (the median particle size D50 is the equivalent circle diameter with a cumulative frequency of 50% based on the number of particles). The method for determining the average particle size of tungsten carbide particles is described below.

[0102] (A2) Using the same method as (A1) to (F1) used to determine the content of the first hard phase, the content of the second hard phase, and the content of the bonding phase in the above-mentioned cemented carbide, the region where the first hard phase (equivalent to tungsten carbide particles) exists is determined on the binarized image.

[0103] (B2) In the image after binarization, a rectangular field of view of 24.9 μm × 18.8 μm is defined. Using the image analysis software described above, the outer edge of each tungsten carbide particle in the field of view is determined, and the equivalent circle diameter (Heywood diameter: equivalent circle diameter with equal area) of each tungsten carbide particle is calculated.

[0104] (C2) Based on all tungsten carbide particles in the above-mentioned field of view, calculate the D50 of the equivalent circle diameter of the tungsten carbide particles.

[0105] The following conditions have been confirmed: as long as the measurement is within the range of the applicant's measurement and is performed on the same sample, even if the cut-out part of the cemented carbide section is arbitrarily set, the shooting area described in (C1) is arbitrarily set on the section, and the measurement field of view described in (B2) is arbitrarily set, and the average particle size of tungsten carbide particles is measured multiple times according to the above steps, the deviation of the measurement results is very small. Even if the cut-out part of the cemented carbide section is arbitrarily set, the shooting area of ​​the image is arbitrarily set, and the measurement field of view is arbitrarily set, the results will not change arbitrarily.

[0106] <Second Hard Phase>

[0107] "composition"

[0108] 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. This improves the cemented carbide's resistance to melting.

[0109] The second hard phase is not limited to pure TiNbC, TiNbN, and TiNbCN, and may contain metallic elements such as tungsten (W), chromium (Cr), and cobalt (Co) without impairing the effects of this disclosure. The combined content of W, Cr, and Co in the second hard phase is preferably 0% by mass or more and less than 0.1% by mass. The content of W, Cr, and Co in the second hard phase is determined by ICP-luminescence analysis.

[0110] The second hard phase is preferably composed of multiple grains. Examples of grains contained in the second hard phase include TiNbC particles, TiNbN particles, TiNbCN particles, and particles composed of two or more first compounds selected from the group consisting of TiNbC, TiNbN, and TiNbCN.

[0111] The second hard phase can consist entirely of grains with the same composition. For example, the second hard phase can consist of TiNbC particles. The second hard phase can consist of TiNbN particles. The second hard phase can consist of TiNbCN particles. The second hard phase can consist of particles composed of two or more of the first compounds selected from the group consisting of TiNbC, TiNbN, and TiNbCN.

[0112] The second hard phase can be composed of two or more grains with different compositions. For example, the second hard phase can be composed of two or more grains selected from the group consisting of: TiNbC particles, TiNbN particles, TiNbCN particles, and particles composed of two or more first compounds selected from the group consisting of TiNbC, TiNbN, and TiNbCN. The second hard phase can be composed of TiNbC particles, TiNbN particles, and TiNbCN particles.

[0113] The method for determining the composition of the second hard phase is as follows.

[0114] (A3) Using an ion slicer (device: IB09060CIS (trademark) manufactured by Nippon Electronics Co., Ltd.), cemented carbide is sliced ​​at arbitrary locations to produce samples with a thickness of 30–100 nm. The accelerating voltage of the ion slicer is 6 kV during slicing and 2 kV during finishing.

[0115] (B3) The above sample was observed at 50,000x magnification using a scanning transmission electron microscope (STEM) (device: JFM-ARM300F (trademark) manufactured by Nippon Electron Ltd.), thereby obtaining STEM-HAADF (high-angle annular darkfield scanning transmission electron microscope) images. The STEM-HAADF image was taken in the central part of the sample, i.e., in areas where the properties are significantly different from the bulk parts, excluding the surface near the cemented carbide (the entire image area is the bulk part of the cemented carbide). The measurement condition was an accelerating voltage of 200 kV. Figure 2 This is an example of a STEM-HAADF image of a cemented carbide according to Embodiment 1.

[0116] (C3) Next, elemental mapping analysis is performed on the STEM-HAADF image using EDX attached to the STEM to obtain an elemental mapping image. Regions in the elemental mapping image containing one or both of carbon (C) and nitrogen (N), as well as titanium (Ti) and niobium (Nb), are identified as the second hard phase, and the composition of this second hard phase is determined. If the second hard phase consists of multiple grains, the composition is determined for each grain. Figure 3 Is with Figure 1 Elemental mapping images of the cemented carbide of Embodiment 1 within the same measurement field of view. Figure 3 At the lower left position, two second hard phases (grains) composed of TiNbN were identified. In comparison... Figure 3 A second hard phase (grain) composed of TiNbN and TiNbC was identified in the upper right corner of the center. Figure 3 A second hard phase (grain) composed of TiNbCN was identified at a position slightly below the center.

[0117] The following conditions have been confirmed: as long as the measurement is within the range of the applicant's measurement and is performed on the same sample, even if the cut-out part of the cemented carbide section is arbitrarily set and the STEM-HAADF image shooting area is arbitrarily set on the sample, and the composition of the second hard phase is measured multiple times according to the above steps, the deviation of the measurement results is very small. Even if the cut-out part of the cemented carbide section is arbitrarily set and the STEM-HAADF image shooting area is arbitrarily set, the results will not change arbitrarily.

[0118] In the second hard phase, the lower limit of the ratio of niobium to the total atomic number of titanium and niobium (hereinafter also referred to as the "Nb ratio") can be set to 0.03 or higher, 0.04 or higher, or 0.05 or higher. The upper limit of this Nb ratio can be set to 0.48 or lower, 0.46 or lower, 0.44 or lower, or 0.42 or lower. Specifically, the Nb ratio can be set to 0.03 or higher and 0.48 or lower, 0.04 or higher and 0.48 or lower, 0.05 or higher and 0.48 or lower, 0.03 or higher and 0.46 or lower, 0.04 or higher and 0.46 or lower, 0.05 or higher and 0.46 or lower, 0.03 or higher and 0.44 or lower, 0.04 or higher and 0.44 or lower, 0.05 or higher and 0.44 or lower, 0.03 or higher and 0.42 or lower, 0.04 or higher and 0.42 or lower, or 0.05 or higher and 0.42 or lower. This allows the second hard phase to be finely dispersed in the cemented carbide, thereby improving the cemented carbide's resistance to caulking.

[0119] In this specification, the ratio of niobium in the second hard phase to the total atomic number of titanium and niobium refers to the average ratio (Nb ratio) of niobium in the overall second hard phase contained in the cemented carbide to the total atomic number of titanium and niobium. This Nb ratio is determined by the following steps: A rectangular measurement field of 24.9 μm × 18.8 μm is set in the elemental mapping image described above (C3). Based on all the second hard phases observed in this measurement field, the composition of the overall second hard phase is measured, and the ratio (Nb ratio) of niobium to the total atomic number of titanium and niobium is calculated. The Nb ratio is determined in five distinct measurement fields. In this specification, the average composition of the overall second hard phase in the five measurement fields corresponds to the overall composition of the second hard phase in the cemented carbide. In this specification, the average Nb ratio in the five measurement fields corresponds to the Nb ratio in the cemented carbide.

[0120] The following conditions have been confirmed: as long as the measurement is within the range of the applicant's measurement and is performed on the same sample, even if the cut-out part of the cemented carbide section is arbitrarily set and the STEM-HAADF image shooting area is arbitrarily set on the sample, and the average Nb ratio in the second cemented phase is measured multiple times according to the above steps, the deviation of the measurement results is very small. Even if the cut-out part of the cemented carbide section is arbitrarily set and the STEM-HAADF image shooting area is arbitrarily set, the results will not change arbitrarily.

[0121] Average particle size

[0122] In Embodiment 1, the average particle size of the second hard phase is 0.1 μm or less. This improves the cemented carbide's resistance to melting and welding. Furthermore, the second hard phase is less likely to become a starting point for damage, thus improving the breakage resistance of tools containing this cemented carbide. The lower limit of the average particle size of the second hard phase is preferably 0.002 μm or more, 0.01 μm or more, 0.02 μm or more, or 0.03 μm or more. The upper limit of the average particle size of the second hard phase is 0.1 μm or less, preferably 0.09 μm or less, 0.08 μm or less, 0.07 μm or less, or 0.06 μm or less. The average particle size of the second hard phase is preferably 0.01 μm or more and 0.1 μm or less, 0.02 μm or more and 0.1 μm or less, 0.03 μm or more and 0.1 μm or less, 0.01 μm or more and 0.09 μm or less, 0.02 μm or more and 0.09 μm or less, 0.03 μm or more and 0.09 μm or less, 0.01 μm or more and 0.08 μm or less, 0.02 μm or more and 0.08 μm or less, 0.03 μm or more and 0.08 μm or less, 0.01 μm or more and 0.07 μm or less, 0.02 μm or more and 0.07 μm or less, 0.03 μm or more and 0.07 μm or less, 0.01 μm or more and 0.06 μm or less, 0.02 μm or more and 0.06 μm or less, or 0.03 μm or more and 0.06 μm or less. As a result, the tool's lifespan is further extended.

[0123] In this specification, the average grain size of the second hard phase refers to the D50 of the equivalent circle diameter (Heywood diameter) of the multiple grains contained in the second hard phase (the median grain size D50 is the equivalent circle diameter whose cumulative frequency based on the number of grains is 50%). The method for determining the average grain size of the second hard phase is as follows.

[0124] (A3) Using the same method as (A1) to (F1) for determining the content of the first hard phase, the content of the second hard phase, and the content of the bonding phase in the above-mentioned cemented carbide, the region where the second hard phase exists is determined on the image after binarization.

[0125] (B3) In the image after binarization, a rectangular field of view of 24.9 μm × 18.8 μm is defined. Using the image analysis software described above, the outer edge of each second hard phase in the field of view is determined, and the equivalent circle diameter of each second hard phase (Heywood diameter: equivalent circle diameter with equal area) is calculated.

[0126] (C3) Based on all the second hard phases in the above-mentioned field of view, calculate the D50 of the equivalent circle diameter of the second hard phase.

[0127] The following conditions have been confirmed: as long as the measurement is within the range of the applicant's measurement and is performed on the same sample, even if the cut-out part of the cemented carbide section is arbitrarily set, the shooting area described in (C1) is arbitrarily set on the section, and the measurement field of view described in (B3) is arbitrarily set, and the average particle size of tungsten carbide particles is measured multiple times according to the above steps, the deviation of the measurement results is very small. Even if the cut-out part of the cemented carbide section is arbitrarily set, the shooting area of ​​the image is arbitrarily set, and the measurement field of view is arbitrarily set, the results will not change arbitrarily.

[0128] Dispersion

[0129] In Embodiment 1, the dispersion of the second hard phase is 0.7 or less. This results in a homogeneous cemented carbide microstructure and excellent weld resistance. The upper limit of the dispersion of this second hard phase is 0.7 or less, preferably 0.70 or less, 0.69 or less, 0.68 or less, 0.65 or less, 0.60 or less, 0.55 or less, or 0.40 or less. The lower limit of the dispersion of this second hard phase is not particularly limited, but is preferably 0 or more, or 0.1 or more. The dispersion of the second hard phase is preferably 0 or more and 0.7 or less, 0 or more and 0.70 or less, 0 or more and 0.69 or less, 0 or more and 0.68 or less, 0 or more and 0.65 or less, 0 or more and 0.60 or less, 0 or more and 0.55 or less, 0 or more and 0.40 or less, 0.1 or more and 0.7 or less, 0.1 or more and 0.70 or less, 0.1 or more and 0.69 or less, 0.1 or more and 0.68 or less, 0.1 or more and 0.65 or less, 0.1 or more and 0.60 or less, 0.1 or more and 0.55 or less, or 0.1 or more and 0.40 or less.

[0130] In this specification, the dispersion of the second hard phase is determined using a Vinylon diagram. The specific determination method is described below.

[0131] (A4) Using the same methods as (A1), (C1), and (E1) used in the above-mentioned methods for determining the content of the first hard phase, the content of the second hard phase, and the content of the bonding phase of the cemented carbide, the reflected electron image of the mirror-finished surface of the cemented carbide is binarized to obtain a binarized image in which only the second hard phase is extracted.

[0132] (B4) In the binarized image described above, a rectangular measurement region of 24.9 μm × 18.8 μm is defined. Within this measurement region, the centroid positions of each second hard phase are derived using the image processing software described above. The calculated centroid coordinates are considered as generatrices, and Vino segmentation is performed to calculate the Vino regions of all generatrices, thus creating a Vino map. A Vino region is a region surrounded by a Vino boundary, which is formed by dividing two adjacent generatrices using perpendicular bisectors when multiple generatrices are arranged on the same plane.

[0133] Figure 4 Indicates based on Figure 1 The Vinno diagram is created from the reflected electron image shown. Figure 4 In the diagram, the small black circle represents the centroid of the second hard phase, the line segment represents the perpendicular bisector between two adjacent generatrices, and the region enclosed by the perpendicular bisector represents the Vino region.

[0134] (C4) Using the image processing software described above, calculate the respective Vino area (μm) for all Vino regions within the measurement area. 2 Here, the Vino region within the aforementioned measurement area refers to the entire Vino region existing within the Vino region within the measurement area. Therefore, if a portion of the Vino region exists outside the aforementioned measurement area, that Vino region is not included within the Vino region within the aforementioned measurement area.

[0135] Calculate the standard deviation σ of the entire Vino area within the above-mentioned measurement region. This standard deviation σ is calculated in this specification.

[0136] (D4) The standard deviation σ described above is calculated in five distinct measurement regions. In this specification, the average standard deviation σ in the five measurement regions corresponds to the dispersion of the second hard phase of the cemented carbide.

[0137] The following conditions have been confirmed: as long as the measurement is within the range of the applicant's measurement and is performed on the same sample, even if the cut-out part of the cemented carbide section is arbitrarily set and the measurement area described in (B4) above is arbitrarily set, and the dispersion of the second hard phase is measured multiple times according to the above steps, the deviation of the measurement results is very small. Even if the cut-out part of the cemented carbide section is arbitrarily set and the shooting area of ​​the image is arbitrarily set, the results will not change arbitrarily.

[0138] <Binding Phase>

[0139] "composition"

[0140] In Embodiment 1, the binding phase comprises at least one first element selected from the group consisting of iron, cobalt, and nickel. The content of the first element in the binding phase (when the first element is composed of two or more elements, it is the sum of their contents) is preferably 90% by mass or more and 100% by mass or less, 95% by mass or more and 100% by mass or less, 98% by mass or more and 100% by mass or less, or 100% by mass. The content of the first element in the binding phase is determined by ICP-luminescence analysis.

[0141] In addition to the first element, the combined phase may also include tungsten (W), chromium (Cr), vanadium (V), titanium (Ti), niobium (Nb), tantalum (Ta), etc.

[0142] <Manufacturing Method>

[0143] The cemented carbide of Embodiment 1 can be manufactured, for example, by the following method. Raw material powders are prepared. Tungsten carbide (WC) powder, tungsten trioxide (WO3) powder, titanium dioxide (TiO2) powder, and niobium oxide (Nb2O5) powder are prepared as raw materials for the first and second hard phases. By using tungsten trioxide (WO3) powder, the WC particles in the cemented carbide can be micronized. Examples of raw materials for the bonding phase include iron (Fe) powder, cobalt (Co) powder, and nickel (Ni) powder. Examples of grain growth inhibitors include chromium carbide (Cr3C2) powder and vanadium carbide (VC) powder.

[0144] The average particle size of tungsten carbide (WC) powder can be set to be greater than 0.1 μm and less than 3.5 μm. The average particle size of WC powder is determined by the Fischer method or the BET method.

[0145] The average particle size of tungsten trioxide (WO3) powder can be set to be ≥0.1 μm and ≤3 μm. The average particle size of titanium oxide (TiO2) powder can be set to be ≥0.001 μm and ≤1 μm. The average particle size of niobium oxide (Nb2O5) powder can be set to be ≥0.001 μm and ≤1 μm. The average particle size of iron (Fe) powder can be set to be ≥0.1 μm and ≤5 μm. The average particle size of cobalt (Co) powder can be set to be ≥0.1 μm and ≤5 μm. The average particle size of nickel (Ni) powder can be set to be ≥0.1 μm and ≤5 μm. The average particle size of the above raw material powders refers to the median particle size d50 based on the number of equivalent sphere diameters of the raw material powder. The average particle size of the raw material powders was measured using a particle size distribution measuring device (trade name: MT3300EX) manufactured by Microtrac.

[0146] Next, the raw material powders are mixed to obtain a mixed powder. Mixing can be done using a mill or a ball mill. The mixing time in a mill can be set to 3 hours or more but less than 20 hours. The mixing time in a ball mill can be set to 3 hours or more but less than 72 hours.

[0147] Next, the mixed powder is shaped into the desired form to obtain a molded body. The molding method and conditions can be any general method and condition, without particular limitations.

[0148] Next, the shaped body is placed in a sintering furnace and heated to 1200°C under vacuum. Then, under an N2 atmosphere and a pressure of 8–40 kPa, the temperature is increased from 1200°C to 1350°C. Next, under an N2 atmosphere and a pressure of 12–40 kPa, the shaped body is sintered at 1350°C for 30–60 minutes to obtain a sintered body.

[0149] Next, the sintered body is subjected to s-HIP treatment (sinter hot isostatic pressing). For example, for the sintered body, Ar gas is used as the pressure medium and applied at a temperature of 1330–1365°C and a pressure of 3–10 MPa for 60 minutes.

[0150] Next, the s-HIP treated sintered body was rapidly cooled to room temperature in Ar gas at a pressure of 400 kPaG to obtain cemented carbide.

[0151] [Implementation Method 2: Hard Alloy (2)]

[0152] One embodiment of this disclosure (hereinafter also referred to as "Embodiment 2") is a cemented carbide composed of a first hard phase, a third hard phase, and a bonding phase.

[0153] The first hard phase is composed of tungsten carbide particles.

[0154] The third hard phase is composed of at least one second compound selected from the group consisting of TiTaC, TiTaN, and TiTaCN.

[0155] The average particle size of this third hard phase is less than 0.1 μm.

[0156] The dispersion of this third hard phase is below 0.7.

[0157] The content of this third hard phase is more than 0.1% by volume and less than 15% by volume.

[0158] The bonded phase contains at least one first element selected from the group consisting of iron, cobalt, and nickel.

[0159] The content of this bound phase is above 0.1 vol% and below 20 vol%.

[0160] The cemented carbide of Embodiment 2 can be configured to have the same structure as the cemented carbide of Embodiment 1, except that the second hard phase is replaced with a third hard phase. The third hard phase and its manufacturing method will be described below.

[0161] <Third hard phase>

[0162] "composition"

[0163] In embodiment 2, the third hard phase is composed of at least one second compound selected from the group consisting of TiTaC, TiTaN, and TiTaCN. This improves the cemented carbide's resistance to melting.

[0164] The third hard phase is not limited to pure TiTaC, TiTaN, and TiTaCN, and may also contain metallic elements such as tungsten (W), chromium (Cr), and cobalt (Co) without impairing the effects of this disclosure. The combined content of W, Cr, and Co in the third hard phase is preferably 0% by mass or more and less than 0.1% by mass. The content of W, Cr, and Co in the third hard phase is determined by ICP-luminescence analysis.

[0165] The third hard phase is preferably composed of multiple grains. Examples of grains contained in the third hard phase include TiTaC particles, TiTaN particles, TiTaCN particles, and particles composed of two or more second compounds selected from the group consisting of TiTaC, TiTaN, and TiTaCN.

[0166] The third hard phase can consist entirely of grains with the same composition. For example, the third hard phase can consist of TiTaC grains. The third hard phase can consist of TiTaN grains. The third hard phase can consist of TiTaCN grains. The third hard phase can also consist of grains composed of two or more second compounds selected from the group consisting of TiTaC, TiTaN, and TiTaCN.

[0167] The third hard phase can be composed of two or more grains with different compositions. For example, the third hard phase can be composed of two or more grains selected from the group consisting of: TiTaC grains, TiTaN grains, TiTaCN grains, and grains composed of two or more second compounds selected from the group consisting of TiTaC, TiTaN, and TiTaCN. The third hard phase can be composed of TiTaC grains, TiTaN grains, and TiTaCN grains.

[0168] The method for determining the composition of the third hard phase can be performed according to the method for determining the composition of the second hard phase described in Embodiment 1, therefore, its description will not be repeated.

[0169] Figure 5 This is an example of a STEM-HAADF image of a cemented carbide according to Embodiment 2. Figure 6 Is with Figure 5 Elemental mapping images of the cemented carbide of Embodiment 2 within the same measurement field of view. Figure 6 Slightly to the right of the center, a third hard phase (grain) composed of TiTaC and TiTaCN was identified. Figure 6 In the lower part, a third hard phase (grain) composed of TiTaN was identified.

[0170] The following conditions have been confirmed: as long as the measurement is within the range of the applicant's measurement and is performed on the same sample, even if the cut-out portion of the cemented carbide profile is arbitrarily set and the STEM-HAADF image shooting area is arbitrarily set on the sample, and the measurement of the composition of the third hard phase is performed multiple times according to the steps of the method for measuring the composition of the second hard phase described in Embodiment 1, the deviation of the measurement results is very small. Even if the cut-out portion of the cemented carbide profile is arbitrarily set and the STEM-HAADF image shooting area is arbitrarily set, the results will not change arbitrarily.

[0171] In the third hard phase, the lower limit of the ratio of tantalum to the total atomic number of titanium and tantalum (hereinafter also referred to as the "Ta ratio") can be set to 0.03 or higher, 0.04 or higher, or 0.05 or higher. The upper limit of this Ta ratio can be set to 0.48 or lower, 0.46 or lower, 0.44 or lower, or 0.42 or lower. Specifically, the Ta ratio can be set to 0.03 or higher and 0.48 or lower, 0.04 or higher and 0.48 or lower, 0.05 or higher and 0.48 or lower, 0.03 or higher and 0.46 or lower, 0.04 or higher and 0.46 or lower, 0.05 or higher and 0.46 or lower, 0.03 or higher and 0.44 or lower, 0.04 or higher and 0.44 or lower, 0.05 or higher and 0.44 or lower, 0.03 or higher and 0.42 or lower, 0.04 or higher and 0.42 or lower, or 0.05 or higher and 0.42 or lower. This allows the third hard phase to be finely dispersed in the cemented carbide, thereby improving the cemented carbide's resistance to caulking.

[0172] In this specification, the ratio of tantalum in the third hard phase to the total atomic number of titanium and tantalum refers to the average ratio (Ta ratio) of tantalum in the overall third hard phase contained in the cemented carbide to the total atomic number of titanium and tantalum. This Ta ratio is determined through the following steps: A rectangular measurement field of 24.9 μm × 18.8 μm is set in the elemental mapping image of (C3) described above. Based on all the third hard phase observed in this measurement field, the composition of the overall third hard phase is measured, and the ratio of tantalum to the total atomic number of titanium and tantalum (Ta ratio) is calculated. The Ta ratio is determined in five distinct measurement fields. In this specification, the average composition of the overall third hard phase in the five measurement fields corresponds to the overall composition of the third hard phase in the cemented carbide. In this specification, the average Ta ratio in the five measurement fields corresponds to the Ta ratio in the cemented carbide.

[0173] The following conditions have been confirmed: as long as the measurement is within the range of the applicant's measurement and is performed on the same sample, even if the cut-out part of the cemented carbide section is arbitrarily set and the STEM-HAADF image shooting area is arbitrarily set on the sample, and the average Ta ratio in the third cemented phase is measured multiple times according to the above steps, the deviation of the measurement results is very small. Even if the cut-out part of the cemented carbide section is arbitrarily set and the STEM-HAADF image shooting area is arbitrarily set, the results will not change arbitrarily.

[0174] <Manufacturing Method>

[0175] As a method for manufacturing cemented carbide in Embodiment 2, in the method for manufacturing cemented carbide in Embodiment 1, the niobium oxide (Nb2O5) powder is replaced with tantalum oxide (Ta2O5) powder as the raw material powder. Otherwise, it can be the same as the method for manufacturing cemented carbide in Embodiment 1.

[0176] [Implementation Method 3: Tools]

[0177] One embodiment of this disclosure (hereinafter also referred to as "Embodiment 3") is a cutting tool comprising the cemented carbide described in Embodiment 1 or Embodiment 2. This tool possesses not only the excellent mechanical strength inherent in cemented carbide but also excellent resistance to weld penetration. Preferably, at least the portion of the tool involved in cutting comprises the cemented carbide of Embodiment 1 or Embodiment 2. The portion involved in cutting refers to the area at a distance of μm or less from the tool tip.

[0178] Examples of such tools include drill bits, micro drill bits, end mills, indexable cutting inserts for drill bits, indexable cutting inserts for end mills, non-regrinding inserts for milling, non-regrinding inserts for turning, metalworking saws, gear cutting tools, reamers, taps, cutting tools, wear-resistant tools, and friction stirring tools.

[0179] [Postscript 1]

[0180] In the cemented carbide of Embodiment 2, the number of third hard phases is preferably 30 or more within a rectangular field of view of 24.9 μm × 18.8 μm in the binarized image of the reflected electron image obtained by taking a cross-section of the cemented carbide using a scanning electron microscope. This improves the cemented carbide's resistance to caulking.

[0181] [Postscript 2]

[0182] The average particle size of the third hard phase is preferably 0.01 μm or more and 0.08 μm or less. This improves the cemented carbide's resistance to caulking.

[0183] [Postscript 3]

[0184] The dispersion of the third hard phase is preferably below 0.4. This improves the cemented carbide's resistance to caulking.

[0185] Example

[0186] The present embodiment will be further described in detail through the examples. However, the present embodiment is not limited to these examples.

[0187] [Making of cemented carbide]

[0188] <Sample 1 to Sample 37, Sample 1-1 to Sample 1-15>

[0189] As raw material powders, prepare tungsten carbide (WC) powder, tungsten trioxide (WO3) powder, chromium carbide (Cr3C2) powder, titanium oxide (TiO2) powder, niobium oxide (Nb2O5) powder, tantalum oxide (Ta2O5) powder, cobalt (Co) powder, and nickel (Ni) powder.

[0190] As WC powders, tungsten carbide powders manufactured by Allied Material, namely “WC02NR” (average particle size 0.10–0.14 μm, converted particle size based on BET method), “WC04NR” (average particle size 0.45–0.49 μm, average particle size based on Fischer method), and “WC25S” (average particle size 2.4–3.2 μm, measured using a particle size distribution measuring device (trade name: MT3300EX) manufactured by Microtrac, were used.

[0191] The average particle size of WO3 powder is 1.5 μm, the average particle size of Cr3C2 powder is 1.5 μm, the average particle size of TiO2 powder is 0.01 μm, the average particle size of Nb2O5 powder is 0.05 μm, the average particle size of Ta2O5 powder is 0.05 μm, the average particle size of Co powder is 1 μm, and the average particle size of Ni powder is 1 μm. The average particle size of the raw material powders was measured using a particle size distribution measuring device (trade name: MT3300EX) manufactured by Microtrac.

[0192] The raw material powders were mixed at the ratios listed in the "Raw Material Powder" column of Tables 1-3 to obtain a mixed powder. For example, in Sample 1, the mixed powder comprised 52.0% by mass of WC powder (WC04NR), 34.7% by mass of WO3 powder, 1.0% by mass of Cr3C2 powder, 0.27% by mass of TiO2 powder, 0.07% by mass of Nb2O5 powder, and 12.0% by mass of Co powder in 100% by mass. The mixing was performed using a grinding mill. The mixing time in the grinding mill was 10 hours.

[0193] The obtained mixed powder is pressed into shape to obtain A cylindrical, rod-shaped molded body.

[0194] Except for sample 1-1, a sintered body was obtained by the following method. The above-described molded body was placed in a sintering furnace and heated to 1200°C in a vacuum. The heating rate was set to 10°C / min. Then, under a N2 atmosphere, the temperature was increased from 1200°C to 1350°C at the pressure recorded in the "Pressure" column of "Step 1" in Tables 1-3. Next, under a N2 atmosphere, the molded body was sintered at the pressure recorded in the "Pressure" column of "Step 2" in Tables 1-3 and at a temperature of 1350°C, for the time recorded in the "Time" column of "Step 2", to obtain a sintered body. For example, in sample 1, the temperature was increased to 1200°C in a vacuum. Then, under a N2 atmosphere, the temperature was increased from 1200°C to 1350°C at a pressure of 40 kPa. Next, the shaped body was sintered under a nitrogen atmosphere at a pressure of 12 kPa and a temperature of 1350°C for 30 minutes to obtain a sintered body.

[0195] Sample 1-1 was sintered using the following method. The formed body was placed in a sintering furnace and heated to 1200°C in a vacuum. The heating rate was set to 10°C / min. Then, in a vacuum, the temperature was increased from 1200°C to 1350°C (referred to as "vac sintering" in Table 3). Next, the formed body was sintered (referred to as "vac sintering" in Table 3) in a vacuum at a temperature of 1350°C for the time specified in the "Time" column of "Step 2") to obtain the sintered body.

[0196] The obtained sintered body was subjected to s-HIP treatment. Specifically, for the sintered body, Ar gas was used as the pressure medium, and the temperature and pressure listed in the "Temperature" and "Pressure" columns of the "s-HIP" process in Tables 1 to 3 were applied for 60 minutes. For example, in Sample 1, Ar gas was used as the pressure medium, and the treatment was applied at 1350°C and 7 MPaG for 60 minutes. Then, the s-HIP treated sintered body was rapidly cooled to room temperature in Ar gas at a pressure of 400 kPaG to obtain cemented carbide.

[0197] <Sample 1-13>

[0198] Hard alloy was produced using the same method as sample number 5 of the embodiment in Patent Document 2 (Japanese Patent Application Publication No. 2012-251242).

[0199] <Sample 1-14>

[0200] Hard alloy was produced using the same method as in Example 1 of Patent Document 4 (Japanese Patent Application Publication No. 2016-98393).

[0201] [Tool Making]

[0202] The obtained carbide round bar is machined to produce a diameter of... End mill.

[0203]

[0204]

[0205]

[0206] [evaluate]

[0207] <Hard alloy>

[0208] Composition of cemented carbide

[0209] For each cemented carbide sample, the content (volume %) of the first hard phase, the second hard phase or the third hard phase, and the bonding phase was determined. The specific determination method is as described in Embodiment 1. The results are shown in Tables 4 to 6 in the "volume %" column for "first hard phase", the "volume %" column for "second hard phase / third hard phase", and the "volume %" column for "bonding phase".

[0210] Average particle size of tungsten carbide particles

[0211] For each cemented carbide sample, the average particle size of the tungsten carbide particles in the first hard phase was measured. The specific measurement method is as described in Embodiment 1. The results are shown in the "Average Particle Size (μm)" column of "First Hard Phase" in Tables 4 to 6.

[0212] Composition of the second or third hard phase

[0213] For each cemented carbide sample, the composition of the second or third hard phase was determined. The specific determination method is as described in Embodiment 1. The results are shown in the "Composition" column of "Second Hard Phase / Third Hard Phase" in Tables 4 to 6.

[0214] When the "Composition" column is listed as "TiNbC, TiNbN, TiNbCN", it indicates that the cemented carbide contains a second hard phase, which comprises TiNbC particles, TiNbN particles, TiNbCN particles, and particles composed of two or more first compounds selected from the group consisting of TiNbC, TiNbN, and TiNbCN. When the "Composition" column is listed as "TiNbC", it indicates that the second hard phase is composed of TiNbC particles.

[0215] When the "Composition" column lists "TiTaC, TiTaN, TiTaCN", it indicates that the cemented carbide contains a third hard phase, which comprises TiTaC particles, TiTaN particles, TiTaCN particles, and particles composed of two or more second compounds selected from the group consisting of TiTaC, TiTaN, and TiTaCN. When the "Composition" column lists "TiTaC", it indicates that the third hard phase is composed of TiTaC particles.

[0216] The "-" in the "Composition" column indicates that neither the second nor the third hard phase exists.

[0217] Nb ratio, Ta ratio

[0218] For each cemented carbide sample, based on the composition determined above, the ratio of niobium in the second hard phase to the total atomic number of titanium and niobium (Nb ratio), or the ratio of tantalum in the third hard phase to the total atomic number of titanium and tantalum (Ta ratio), was calculated. The results are shown in the "Nb ratio / Ta ratio" column of "Second hard phase / Third hard phase" in Tables 4 to 6.

[0219] Average particle size of the second or third hard phase

[0220] For each sample of cemented carbide, the average particle size of the second or third hard phase was measured. The specific measurement method is as described in Example 1. The results are shown in the "Average Particle Size (μm)" column of "Second Hard Phase / Third Hard Phase" in Tables 4 to 6.

[0221] Dispersion of the second or third hard phase

[0222] For each cemented carbide sample, the dispersion of the second or third hard phase was measured. The specific measurement method is as described in Embodiment 1. The results are shown in the "Dispersion" column of "Second Hard Phase / Third Hard Phase" in Tables 4 to 6.

[0223] The quantity of the second or third hard phase

[0224] For each sample of cemented carbide, the quantity of the second or third hard phase within a rectangular measurement field of view measuring 24.9 μm × 18.8 μm was determined. The specific measurement method is as described in Embodiment 1. The results are shown in the "Quantity" column of "Second Hard Phase / Third Hard Phase" in Tables 4 to 6.

[0225] <Tools>

[0226] Melt adhesion resistance test

[0227] The side surfaces of 64 titanium alloy (Ti-6Al-4V) were machined using end mills for each sample. Machining conditions were set as follows: cutting speed Vc = 150 m / min, table feed F = 0.1 mm / min, depth of cut (axial) ap = 2.0 mm, and depth of cut (radial) ae = 0.5 mm. Machining was performed using three end mills. These machining conditions are equivalent to high-efficiency machining of difficult-to-machine materials.

[0228] At the point when the cutting length reaches 180m, the tip of the end mill is observed using a scanning electron microscope, and the area of ​​the tip with deposited material is measured through image analysis. Specifically, the measurement is performed according to the following steps.

[0229] A reflected electron image of the end mill tip was obtained by photographing it from the rake face direction using a scanning electron microscope (SEM). The magnification was 5000x. The measurement conditions were an accelerating voltage of 3kV, a current of 2nA, and a working distance (WD) of 5mm. Figure 7 An example of this reflected electron image is shown in the image. Figure 7 In the figure, the dark gray area attached to the tip 3, as indicated by reference numeral 5, is the fused material.

[0230] For the areas captured by the SEM, SEM-EDX was used for analysis. Titanium mapping was performed in these areas to identify the composition of the weld deposit. Image analysis software (OpenCV, SciPy) was used to analyze the area (mm²) of the blade tip with the weld deposit. 2 ) to be measured.

[0231] The average area of ​​the tool tips with deposited material from the three end mills is shown in the "Deposit Resistance" column of "Tools" in Tables 4-6. The smaller the area, the better the deposit resistance. The record "30m, Defect" in the "Deposit Resistance" column indicates that the tool was damaged at the cutting time point of 30m.

[0232] Abrasion Resistance Test

[0233] Using the end mills of each specimen, cutting tests were conducted under the same conditions as the above-described corrosion resistance test. The cutting length at the point when the flank wear reached 0.2 mm was measured. The average cutting length of the three end mills is shown in the "Tool Life" column of "Tools" in Tables 4-6. The longer the cutting length, the longer the tool life.

[0234]

[0235]

[0236]

[0237] <Inspection>

[0238] The cemented carbide and tools of Specimens 1 to 37 correspond to the Examples. The cemented carbide and tools of Specimens 1-1 to 1-15 correspond to the Comparative Examples. It was confirmed that the tools of Specimens 1 to 37 (Examples) have superior resistance to deposition and longer tool life in high-efficiency machining of difficult-to-cut materials compared with the tools of Specimens 1-1 to 1-15 (Comparative Examples).

[0239] The embodiments and examples of this disclosure have been described above, but it is also intended from the outset that the above-described embodiments and examples may be appropriately combined or modified.

[0240] The embodiments and examples disclosed herein should be considered exemplary in all respects, and not restrictive. The scope of the invention is defined not by the foregoing embodiments and examples, but by the claims, and is intended to include all modifications equivalent to and within the scope of the claims.

[0241] Explanation of reference numerals in the attached figures

[0242] 3: Blade tip; 5: Molded material.

Claims

1. A cemented carbide comprising a first hard phase, a second hard phase, and a bonding phase, wherein, The first hard phase is composed of tungsten carbide particles. The second hard phase is composed of at least one first compound selected from the group consisting of TiNbC, TiNbN, and TiNbCN. The average particle size of the second hard phase is less than 0.1 μm. The dispersion of the second hard phase is below 0.

7. The content of the second hard phase is 0.1% by volume or more and 15% by volume or less. The bonding phase comprises at least one first element selected from the group consisting of iron, cobalt, and nickel. The content of the bound phase is 0.1% by volume or more and 20% by volume or less. The dispersion is the standard deviation of the area of ​​each Vino region in the Vino diagram obtained by dividing the Vino map using the centroid of the second hard phase as the parent point. The Vino map is obtained as follows: the second hard phase is extracted from the reflected electron image obtained by taking a cross-section of the cemented carbide using a scanning electron microscope; a rectangular measurement field of 24.9 μm × 18.8 μm is set in the binarized image of the reflected electron image; the centroid of the extracted second hard phase is used as the mother point for Vino segmentation in the measurement field; and the Vino region of all the mother points is calculated.

2. The cemented carbide according to claim 1, wherein, In the binarized image of the reflected electron image obtained by taking a cross-section of the cemented carbide using a scanning electron microscope, within a rectangular field of view of measurement of 24.9 μm × 18.8 μm, the number of the second hard phase is 30 or more.

3. The cemented carbide according to claim 1 or 2, wherein, The average particle size of the second hard phase is greater than 0.01 μm and less than 0.08 μm.

4. The cemented carbide according to claim 1 or 2, wherein, The dispersion of the second hard phase is less than 0.

60.

5. The cemented carbide according to claim 1 or 2, wherein, The dispersion of the second hard phase is less than 0.

4.

6. The cemented carbide according to claim 1 or 2, wherein, In the second hard phase, the ratio of niobium to the total atomic number of titanium and niobium is 0.03 or more and 0.48 or less.

7. A cemented carbide comprising a first hard phase, a third hard phase, and a bonding phase, wherein, The first hard phase is composed of tungsten carbide particles. The third hard phase is composed of at least one second compound selected from the group consisting of TiTaC, TiTaN, and TiTaCN. The average particle size of the third hard phase is less than 0.1 μm. The dispersion of the third hard phase is below 0.

7. The content of the third hard phase is more than 0.1% by volume and less than 15% by volume. The bonding phase comprises at least one first element selected from the group consisting of iron, cobalt, and nickel. The content of the bound phase is 0.1% by volume or more and 20% by volume or less. The dispersion is the standard deviation of the area of ​​each Vino region in the Vino diagram obtained by dividing the Vino map using the centroid of the third hard phase as the parent point. The Vino map is obtained as follows: the third hard phase is extracted from the reflected electron image obtained by taking a cross-section of the cemented carbide using a scanning electron microscope; a rectangular measurement field of 24.9 μm × 18.8 μm is set in the binarized image of the reflected electron image; the centroid of the extracted third hard phase is used as the mother point for Vino segmentation in the measurement field; and the Vino region of all the mother points is calculated.

8. The cemented carbide according to claim 7, wherein, In the binarized image of the reflected electron image obtained by taking a cross-section of the cemented carbide using a scanning electron microscope, the number of the third hard phase is more than 30 within a rectangular field of view of 24.9 μm × 18.8 μm.

9. The cemented carbide according to claim 7 or 8, wherein, The average particle size of the third hard phase is greater than 0.01 μm and less than 0.08 μm.

10. The cemented carbide according to claim 7 or 8, wherein, The dispersion of the third hard phase is less than 0.

4.

11. The cemented carbide according to claim 7 or 8, wherein, In the third hard phase, the ratio of tantalum to the total atomic number of titanium and tantalum is 0.03 or more and 0.48 or less.

12. A tool, wherein, The tool is a tool comprising any one of the cemented carbide claims 1 to 11.

Images