Hard alloy

Abstract

A cemented carbide provided with a binding phase and a plurality of tungsten carbide particles, the cemented carbide containing the tungsten carbide particles and the binding phase in a total amount of 89 vol% or more, the cemented carbide containing 1.8 vol% or more and 20.0 vol% or less of the binding phase, the binding phase containing cobalt, and the balance being cemented carbide. The cemented carbide contains 1.0 mass% or more of cobalt, and the hardness of the binder phase at 25 DEG C as measured by a nanoindentation method is 7.0 GPa or more.

Description

Technical Field

[0001] This disclosure relates to a cemented carbide. Background Technology

[0002] Previously, cemented carbide containing a bonding phase and multiple tungsten carbide particles was used as a raw material for cutting tools (Patent Document 1).

[0003] Existing technical documents Patent documents Patent document 1: Japanese Patent Application Publication No. 2004-131769. Summary of the Invention

[0004] The cemented carbide disclosed herein is a cemented carbide containing a bonding phase and multiple tungsten carbide particles, wherein, The cemented carbide contains a total of 89% by volume or more of the tungsten carbide particles and the bonding phase. The cemented carbide contains more than 1.8 vol% and less than 20.0 vol% of the bonding phase. The combined phase contains cobalt. This cemented carbide contains more than 1.0% by mass of cobalt. The hardness of this bonded phase, measured by nanoindentation at 25°C, is above 7.0 GPa. Attached Figure Description

[0005] Figure 1 This is a schematic diagram showing a cross-section of a cemented carbide according to one embodiment of the present disclosure. Detailed Implementation

[0006] [The problem this disclosure aims to solve] In recent years, the difficulty of machining materials has been continuously increasing, and the operating conditions of cutting tools have become more demanding. Therefore, there is a growing demand for improved properties in cemented carbide used as the base material for cutting tools. Especially in the case of cutting tools used for machining high-hardness materials, there is a need for cemented carbide materials that can achieve long tool life.

[0007] Therefore, the object of this disclosure is to provide a cemented carbide that can achieve a long tool life, especially when used as a material for cutting tools for machining high-hardness materials.

[0008] [The Effects of This Disclosure] According to this disclosure, a cemented carbide can be provided, especially when used as a material for cutting tools for machining high-hardness materials, to achieve a long tool life.

[0009] [Description of embodiments of this disclosure] First, embodiments of this disclosure will be described.

[0010] (1) The cemented carbide disclosed herein is a cemented carbide having a bonding phase and multiple tungsten carbide particles, wherein, The cemented carbide comprises a total of 89% by volume or more of the tungsten carbide particles and the bonding phase. The cemented carbide comprises 1.8 vol% or more and 20.0 vol% or less of the bonding phase. The bonding phase contains cobalt. The cemented carbide contains more than 1.0% by mass of cobalt. The hardness of the bonding phase, measured by nanoindentation at 25°C, is above 7.0 GPa.

[0011] According to this disclosure, a cemented carbide can be provided, especially when used as a material for cutting tools for machining high-hardness materials, to achieve a long tool life.

[0012] (2) Alternatively, in (1) above, the bonding phase may further include a first element. The first element is at least one element selected from the group consisting of silicon, phosphorus, germanium, tin, rhenium, ruthenium, osmium, iridium, and platinum. This provides a cemented carbide that can further extend the tool life of cutting tools, especially in the machining of high-hardness materials.

[0013] (3) Alternatively, in (2) above, the percentage of the mass M1 of the first element relative to the total mass M1+M2 of the first element and the mass M2 of cobalt in the combined phase is 1% or more and 6% or less. Therefore, a cemented carbide can be provided that further extends the tool life of cutting tools, especially in the machining of high-hardness materials.

[0014] [Details of the embodiments disclosed herein] Hereinafter, with reference to the accompanying drawings, a specific example of a cutting tool according to one embodiment of the present disclosure (hereinafter also referred to as "this embodiment") will be described. In the 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 the clarity and simplification of the drawings, and do not necessarily represent actual dimensional relationships.

[0015] In this disclosure, expressions in the form of "A~B" refer to the upper and lower limits of a range (i.e., above A and below B). When there is no unit recorded in A but only in B, the unit of A is the same as the unit of B.

[0016] In this disclosure, when compounds are represented by chemical formulas, all previously known atomic ratios are included without specifically limiting the atomic ratios, and are not necessarily limited to atomic ratios within the stoichiometric range.

[0017] [Implementation Method 1: Hard Alloy] use Figure 1 The following describes a cemented carbide according to one embodiment of the present disclosure.

[0018] One embodiment of this disclosure (hereinafter also referred to as "this embodiment") is a cemented carbide 3 having a bonding phase 2 and a plurality of tungsten carbide particles 1, wherein, The cemented carbide 3 comprises tungsten carbide particles 1 in a total volume of more than 89% and the bonding phase 2. The cemented carbide 3 contains more than 1.8 vol% and less than 20.0 vol% of the bonding phase 2. This bound phase 2 contains cobalt. The cemented carbide 3 contains more than 1.0% by mass of cobalt. The hardness of this phase 2, measured by nanoindentation at 25°C, is above 7.0 GPa.

[0019] According to this disclosure, a cemented carbide 3 can be provided, particularly in the case of materials used in cutting tools for machining high-hardness materials, to achieve a long tool life. The reasons for this are speculated to be as follows.

[0020] The cemented carbide 3 of this embodiment includes a bonding phase 2 and a plurality of tungsten carbide particles 1 (hereinafter also referred to as "WC particles 1"), and the total content of WC particles 1 and bonding phase 2 in the cemented carbide 3 is 89% by volume or more. As a result, the cemented carbide 3 has high hardness and high strength, and cutting tools using this cemented carbide 3 can have excellent wear resistance and chipping resistance.

[0021] The cemented carbide 3 of Embodiment 1 contains a binding phase 2 of 1.8% by volume or more and 20.0% by volume or less, the binding phase 2 containing cobalt, and the cemented carbide 3 contains 1.0% by mass or more of cobalt. Furthermore, the hardness of the binding phase 2, measured by nanoindentation at 25°C, is 7.0 GPa or more, indicating that the binding phase 2 exhibits excellent hardness at 25°C (in other words, at room temperature). Therefore, the hardness of the cemented carbide 3 is improved, and cutting tools using this cemented carbide 3 exhibit excellent wear resistance, especially in the machining of high-hardness materials.

[0022] Composition of cemented carbide The cemented carbide 3 contains tungsten carbide particles 1 and a bonding phase 2 totaling 89% by volume or more. This increases the hardness of the cemented carbide 3. The cemented carbide 3 may also contain tungsten carbide particles 1 and bonding phase 2 totaling 90% by volume or more, 91% by volume or more, or 92% by volume or more. The upper limit of the total content of tungsten carbide particles 1 and bonding phase 2 in the cemented carbide 3 may be, for example, 100% by volume or less, 99% by volume or less, or 98% by volume or less. The cemented carbide 3 may contain tungsten carbide particles 1 and bonding phase 2 totaling 90% by volume or less and 100% by volume, 91% by volume or more and 100% by volume or less, or 92% by volume or more and 100% by volume or less.

[0023] The cemented carbide 3 contains 1.8% by volume and 20.0% by volume of the bonding phase 2. Therefore, the cemented carbide 3 can improve both hardness and toughness. The lower limit of the content of bonding phase 2 in the cemented carbide 3 can be 2.0% by volume or more, 3.0% by volume or more, or 4.0% by volume or more. The upper limit of the content of bonding phase 2 in the cemented carbide 3 can be 19.0% by volume or less, 18.0% by volume or less, or 17.0% by volume or less. The cemented carbide 3 can contain 2.0% by volume and 19.0% by volume, 3.0% by volume and 18.0% by volume, or 4.0% by volume and 17.0% by volume of bonding phase 2.

[0024] The cemented carbide 3 of Embodiment 1 can be composed of a bonding phase 2 and a plurality of tungsten carbide particles 1. In addition to including tungsten carbide particles 1 and a bonding phase 2, the cemented carbide 3 of this embodiment may also include other phases (not shown). Examples of other phases include carbides, nitrides, or carbonitrides containing at least one second element selected from the group consisting of titanium (Ti), tantalum (Ta), niobium (Nb), zirconium (Zr), hafnium (Hf), and molybdenum (Mo). Other phase compositions include, for example, TiCN, TaC, NbC, ZrC, HfC, and Mo2C.

[0025] The cemented carbide 3 of Embodiment 1 may be composed of tungsten carbide particles 1, a bonding phase 2, and other phases. The content of the other phases in the cemented carbide 3 is permissible within a range that does not impair the effects of this disclosure. For example, the content of the other phases in the cemented carbide 3 may be greater than 0 vol% and less than 20 vol%, greater than 0 vol% and less than 18 vol%, or greater than 0 vol% and less than 16 vol%. In this case, the combined content of the tungsten carbide particles 1 and the bonding phase 2 in the cemented carbide 3 may be 80 vol% or more and less than 100 vol%, 82 vol% or more and less than 100 vol%, or 84 vol% or more and less than 100 vol%.

[0026] The cemented carbide 3 of Embodiment 1 may contain impurities. Examples of such impurities include, for instance, iron (Fe), calcium (Ca), oxygen (O), and sulfur (S). The impurity content of the cemented carbide 3 is permissible within a range that does not impair the effects of this disclosure. For example, the impurity content of the cemented carbide 3 may be 0% by mass or more and less than 0.1% by mass. The impurity content of the cemented carbide 3 is determined by ICP-based inductively coupled plasma emission spectroscopy (measurement device: Shimadzu Corporation "ICPS-8100" (trademark)).

[0027] The methods for determining the content [volume %] of tungsten carbide particles 1 in cemented carbide 3 and the content [volume %] of the bonding phase 2 in cemented carbide 3 are as follows.

[0028] (A1) Cut out any position of the cemented carbide 3 to expose the cross section. Use a cross section polishing machine (manufactured by Nippon Electronics Co., Ltd.) to perform mirror finishing on the cross section.

[0029] (B1) The mirror-finished surface of cemented carbide 3 was analyzed by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) (device: “Gemini450” (trademark) manufactured by Carl Zeiss) to determine the elements contained in cemented carbide 3.

[0030] (C1) A scanning electron microscope (SEM) was used to photograph the mirror-finished surface of cemented carbide 3 to obtain a reflected electron image. The image was taken in the central part of the cross-section of cemented carbide 3, excluding areas near the surface of cemented carbide 3 that have properties significantly different from the main body (the entire image area represents the main body of cemented carbide 3). The magnification was 5000x. The measurement conditions were an accelerating voltage of 3kV, a current of 2nA, and a working distance (WD) of 5mm.

[0031] (D1) For the imaging area described in (C1) above, an energy dispersive X-ray analyzer (SEM-EDX) attached to the SEM is used to analyze the distribution of the elements identified in (B1) above in the imaging area, and an element mapping image is obtained.

[0032] (E1) The reflected electron image obtained in (C1) above is read into the computer and binarized using image analysis software (OpenCV, SciPy). In the binarized image, tungsten carbide particles 1 are represented in white, and the bound phase 2 is represented in gray to black. Furthermore, the binarization threshold varies depending on the contrast, and is therefore set for each image.

[0033] (F1) By overlaying the elemental mapping image obtained in (D1) above with the binarized image obtained in (E1) above, the respective regions where tungsten carbide particles 1 and the binding phase 2 exist are determined on the binarized image. Specifically, the regions represented in white in the binarized image and containing tungsten (W) and carbon (C) in the elemental mapping image correspond to the regions where tungsten carbide particles 1 exist. The regions represented in gray to black in the binarized image and containing cobalt (Co) in the elemental mapping image correspond to the regions where the binding phase 2 exists.

[0034] (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 percentage of tungsten carbide particles 1 and the bound phase 2 is measured with the total area of ​​the field of view as the denominator.

[0035] (H1) The above (G1) determination is performed in five distinct measurement fields. In this specification, the average area percentage of tungsten carbide particles 1 in the five measurement fields corresponds to the content of tungsten carbide particles 1 in cemented carbide 2 [volume %], and the average area percentage of the bound phase 2 in the five measurement fields corresponds to the content of bound phase 2 in cemented carbide 3 [volume %].

[0036] In the case where cemented carbide 3 contains other phases in addition to tungsten carbide particles 1 and bonding phase 2, the content of other phases in cemented carbide 3 can be obtained by subtracting the content of tungsten carbide particles 1 [volume%] and the content of bonding phase 2 [volume%] as determined in the above steps from the total cemented carbide 3 (100 volume%).

[0037] It has been confirmed that 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 cross section of the cemented carbide 3 is arbitrarily set, and the shooting area described in (C1) is arbitrarily set on the cross section, and the content of tungsten carbide particles 1 and the content of bonding phase 2 of cemented carbide 3 are measured multiple times according to the above steps, the deviation of the measurement results is small and will not change arbitrarily.

[0038] "Combination Phase" The bonding phase 2 contains cobalt, and the cemented carbide 3 contains 1.0% by mass or more of cobalt. This imparts excellent toughness to the cemented carbide 3. Furthermore, the bonding phase 2 may contain 50% by mass or more of cobalt, or 60% by mass or more, or 70% by mass or more, or 80% by mass or more, or 90% by mass or more, or 95% by mass or more. The bonding phase 2 may consist entirely of cobalt. Alternatively, the bonding phase 2 may consist of cobalt and the first element described later. Additionally, the cobalt in the cemented carbide 3 may exist solely in the bonding phase 2. The lower limit of the cobalt content in the cemented carbide 3 may be 2.0% by mass or more, or 3.0% by mass or more, or 4.0% by mass or more. The upper limit of the cobalt content in the cemented carbide 3 may be 20% by mass or less, or 15% by mass or less, or 12% by mass or less, or 10% by mass or less. The cemented carbide 3 may contain more than 1.0% by mass and less than 20% by mass of cobalt, or more than 2.0% by mass and less than 15% by mass of cobalt, or more than 3.0% by mass and less than 12% by mass of cobalt.

[0039] The method for determining the cobalt content in cemented carbide 3 is as follows. First, an imaging area is set using the same method (A1) to (C1) as the method for determining the content of tungsten carbide particles 1 and the content of the binding phase 2 in cemented carbide 3 described above. Next, the imaging area is analyzed using SEM-EDX to determine the distribution of the elements determined in (B1) above, and an elemental mapping image is obtained, while simultaneously determining the cobalt content in cemented carbide 3. Furthermore, the method for determining the "cobalt content in the binding phase 2" is as follows. First, the area where the binding phase 2 exists is determined on the binarized image using the same method (A1) to (F1) as the method for determining the content of tungsten carbide particles 1 and the content of the binding phase 2 in cemented carbide 3 described above. Next, the area where the binding phase 2 exists is analyzed using SEM-EDX to determine the "cobalt content in the binding phase 2". Additionally, the method for determining that "cobalt in cemented carbide 3 exists only in the binding phase 2" is as follows. First, using the same method (A1) to (F1) as the method for determining the content of tungsten carbide particles 1 and the content of the binding phase 2 in the cemented carbide 3 described above, the regions where tungsten carbide particles 1 and the regions where the binding phase 2 are present are determined on the binarized image. Next, based on the elemental mapping image and the regions where tungsten carbide particles 1 and the regions where the binding phase 2 are present, it is determined that "cobalt in cemented carbide 3 exists only in the binding phase 2".

[0040] It has been confirmed that 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 cross section of the cemented carbide 3 is arbitrarily set, the shooting area described in (C1) above is recorded, and the above measurement is performed multiple times according to the above steps, the deviation of the measurement results is small and will not change arbitrarily.

[0041] Phase 2 further comprises a first element, which may be at least one element selected from the group consisting of silicon, phosphorus, germanium, tin, rhenium, ruthenium, osmium, iridium, and platinum. Thus, a cemented carbide 3 can be provided, particularly in the machining of high-hardness materials, to further extend the tool life of cutting tools.

[0042] The content of the first element in cemented carbide 3 can be 0.01% by mass or more and 1.0% by mass or less. Therefore, the bonding phase 2 can possess both superior hardness and superior toughness. Furthermore, the content of the first element in bonding phase 2 can be 50% by mass or less, or 40% by mass or less, or 30% by mass or less, or 20% by mass or less, or 10% by mass or less, or 5% by mass or less. The first element in cemented carbide 3 can exist only in bonding phase 2. The lower limit of the content of the first element in cemented carbide 3 can be 0.01% by mass or more, or 0.04% by mass or more, or 0.1% by mass or more. The upper limit of the content of the first element in cemented carbide 3 can be 1.0% by mass or less, or 0.8% by mass or less, or 0.6% by mass or less. The content of the first element in cemented carbide 3 can be 0.04% by mass or more and 0.8% by mass or less, or 0.1% by mass or more and 0.6% by mass or less.

[0043] The method for determining the content of the first element in cemented carbide 3 is as follows. Except for replacing "cobalt" with "first element," the method is performed in the same manner as the method for determining the content of cobalt in cemented carbide 3. Furthermore, the method for determining the "content of the first element in the bonding phase 2" is as follows. Except for replacing "Next, ... determine the 'cobalt content' in the bonding phase 2" with "Next, ... determine the 'first element content' in the bonding phase 2," the method is performed in the same manner as the method for determining the cobalt content in the bonding phase 2. Additionally, the method for determining that "the first element in cemented carbide 3 exists only in the bonding phase 2" is as follows. Except for replacing "Next, ... determine that 'cobalt' in cemented carbide 3 exists only in the bonding phase 2" with "Next, ... determine that 'the first element' in cemented carbide 3 exists only in the bonding phase 2," the method is performed in the same manner as the method for determining that "cobalt in cemented carbide 3 exists only in the bonding phase 2."

[0044] It has been confirmed that 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 cross section of the cemented carbide 3 is arbitrarily set, the shooting area described in (C1) above is recorded, and the above measurement is performed multiple times according to the above steps, the deviation of the measurement results is small and will not change arbitrarily.

[0045] In the bonding phase 2, the percentage of the mass M1 of the first element relative to the total mass M1+M2 of the first element and the mass M2 of cobalt, {M1 / (M1+M2)}×100, can be 1% or more and 6% or less. Therefore, the bonding phase 2 can possess both superior hardness and superior toughness, thus providing a cemented carbide 3 that can further extend the tool life of cutting tools, especially in the machining of high-hardness materials. Here, when the bonding phase contains two or more first elements, the mass M1 of the first element refers to the total mass of all types of first elements. The lower limit of this percentage {M1 / (M1+M2)}×100 can be 1% or more, 2% or more, or 3% or more. The upper limit of this percentage {M1 / (M1+M2)}×100 can be 6% or less, 5% or less, or 4% or less. The percentage {M1 / (M1+M2)}×100 can be above 2% and below 5%, or above 3% and below 4%.

[0046] The method for determining the percentage {M1 / (M1+M2)}×100 is as follows. Using the same method (A1) to (F1) as described above for determining the content of tungsten carbide particles 1 and the content of the bound phase 2 in the cemented carbide 3, the region where the bound phase 2 exists is determined on the binarized image. The region where the bound phase 2 exists is analyzed using SEM-EDX, and the cobalt content and the first element content in the bound phase 2 are determined. Based on these, the percentage {M1 / (M1+M2)}×100 is calculated. The above determination is performed in five distinct measurement fields. In this specification, the average of the percentage {M1 / (M1+M2)}×100 in the five measurement fields corresponds to the percentage {M1 / (M1+M2)}×100 in the bound phase 2.

[0047] 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 cross section of the cemented carbide 3 is arbitrarily set, or the shooting area described in (C1) above, and multiple percentage measurements of {M1 / (M1+M2)}×100 are performed according to the above steps, the deviation of the measurement results will be small and will not change arbitrarily.

[0048] <Hardness of the bonding phase> The hardness of phase 2, measured using nanoindentation at 25°C, is 7.0 GPa or higher. Therefore, phase 2 exhibits excellent hardness at 25°C (in other words, at room temperature). The lower limit of this hardness can be 7.1 GPa or higher, 7.2 GPa or higher, or 7.4 GPa or higher. The upper limit of this hardness can be 9 GPa or lower, 8.5 GPa or lower, or 8 GPa or lower. The hardness can be 7.0 GPa or higher and 9 GPa or lower, 7.1 GPa or higher and 8.5 GPa or lower, or 7.2 GPa or higher and 8 GPa or lower.

[0049] The hardness of bonding phase 2 at 25°C was determined using nanoindentation (Bruker's "Hysitron TI 980 Triboindenter"). This nanoindentation method was performed according to ISO 14577, under the conditions of a test load of 0.5 mN, a load duration of 0.1 seconds, a load holding time of 0.1 seconds, and an unloading time of 0.1 seconds. The test subjects were any ten bonding phases 2 exposed by grinding the surface of cemented carbide 3 using a cross-section polishing (CP) processing apparatus (JEOL Ltd.'s "IB-19500CP Cross-Section Sample Preparation Apparatus" (trademark)). The average hardness of each of the ten bonding phases 2 was taken as the aforementioned "hardness of bonding phase 2".

[0050] 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 ten binding phases 2 are arbitrarily set and the hardness of binding phase 2 is measured multiple times, the deviation of the measurement results will be small and will not change arbitrarily.

[0051] Tungsten carbide particles In Embodiment 1, the tungsten carbide particles 1 include at least one of "pure WC particles (WC completely free of impurity elements, including WC with impurity element content below the detection limit)" and "WC particles that intentionally or unavoidably contain impurity elements within them without impairing the effects of this disclosure." The impurity content of the tungsten carbide particles (the total content of the elements constituting the impurities if there are two or more) is less than 0.1% by mass. The impurity element content of the tungsten carbide particles is determined by ICP luminescence analysis (Inductively Coupled Plasma Emission Spectroscopy, measuring device: "ICPS-8100" (trademark) manufactured by Shimadzu Corporation).

[0052] In Embodiment 1, the average particle size of the tungsten carbide particles 1 is not particularly limited. For example, the average particle size of the tungsten carbide particles 1 can be set to 0.5 μm or more and 3 μm or less. It has been confirmed that the cemented carbide 3 of Embodiment 1 can have a long tool life regardless of the average particle size of the tungsten carbide particles 1.

[0053] Applications of cemented carbide The cemented carbide 3 of this embodiment can be used in cutting tools. Examples of such cutting tools include general-purpose machining tools. More specifically, examples include drills, end mills, indexable cutting inserts for drills, indexable cutting inserts for end mills, indexable cutting inserts for milling, indexable cutting inserts for turning, metalworking saws, gear cutting tools, reamers, taps, and other cutting tools.

[0054] [Implementation Method 2: Method for Manufacturing Hard Alloy] The cemented carbide of this embodiment can be manufactured by sequentially performing the following steps: raw material powder preparation, mixing, molding, sintering, cooling, and HIP (Hot Isostatic Pressing). Each step will be described below.

[0055] <Preparation Process> The preparation process involves preparing the raw material powders that constitute the cemented carbide material. Examples of raw material powders include tungsten carbide powder (hereinafter also referred to as "WC powder") and cobalt (Co) powder. Based on these raw material powders, other powders such as first element powder, niobium carbide (NbC) powder, tungsten carbide (TaC) powder, titanium carbonitride (TiCN) powder, and zirconium carbide (ZrC) powder can also be prepared. These raw material powders can be commercially available. There are no particular limitations on the average particle size of these raw material powders; for example, it can be 0.5 to 2 μm. 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.

[0056] <Mixed Processes> The mixing process is a process of mixing the respective raw material powders prepared in the preparation process in a predetermined ratio. Through the mixing process, a mixed powder formed by mixing the respective raw material powders is obtained. The mixing ratio of the respective raw material powders is appropriately adjusted according to the composition of the target cemented carbide. As the raw material powder, the first element powder can be used. Thus, due to the relationship that the first element is sufficiently dissolved in the binder phase, it is easier for the cemented carbide to have the desired "hardness at 25°C measured by nanoindentation of the binder phase". From the viewpoint of making the total of the content rate of tungsten carbide particles and the content rate of the binder phase within the desired range, in the mixed powder, the total content rate of powders other than WC powder, Co powder, and the first element powder can be less than 5% by mass. By appropriately adjusting the input amounts of the respective raw material powders, the content rate of the binder phase and the content rate of WC particles can be made within the desired ranges respectively.

[0057] The mixing of the respective raw material powders can use conventionally known mixing methods such as a grinder, a ball mill, and a bead mill. The mixing conditions can also use conventionally known conditions. The mixing time can be set, for example, to 2 hours or more and 20 hours or less.

[0058] After the mixing process, granulation of the mixed powder can be performed as needed. By granulating the mixed powder, it is easy to fill the mixed powder into a die head or a mold in the subsequent forming process. Granulation can apply a known granulation method, and for example, a commercially available granulator such as a spray dryer can be used.

[0059] <Forming Process> The forming process is a process of forming the mixed powder obtained in the mixing process into a shape for a cutting tool to obtain a formed body. The forming method and forming conditions in the forming process can be general methods and conditions without particular limitation.

[0060] <Sintering Process> The sintering process is a process of sintering the formed body obtained in the forming process to obtain a cemented carbide intermediate. The sintering conditions in this embodiment are as described below. The formed body is heated to 1360°C and held at 1360°C for 1 hour.

[0061] <Cooling Process> The cooling process is a process of cooling the cemented carbide intermediate after the sintering process. More specifically, the cemented carbide intermediate is cooled to 800°C (hereinafter, also referred to as "the first cooling"). The cooling rate of the first cooling is, for example, 20°C / minute.

[0062] <HIP Process> The HIP process is a process of HIP treatment on the cemented carbide intermediate after the cooling process. The conditions for the HIP process in this embodiment are as follows: The cemented carbide intermediate is held at a pressure of 100 MPa for 2 hours. Thus, the cemented carbide of Embodiment 1 can be obtained.

[0063] <Features of the cemented carbide manufacturing method of this embodiment> In this embodiment, the sintering process is performed by heating the formed body to 1360°C and holding it at 1360°C for 1 hour. Further, the cooling process is performed by setting a cooling rate of 20°C / minute up to 800°C. Further, the HIP process is performed under conditions of 100 MPa pressure and 2 hours. Through these processes, a cemented carbide with a hardness of 7.0 GPa or higher at 25°C, as measured by nanoindentation, can be manufactured. The cemented carbide of this disclosure, achieved through such sintering conditions, cooling process, and HIP process, is a new discovery resulting from in-depth research by the inventors of this invention.

[0064] [Postscript 1] In the cemented carbide of Embodiment 1, the nanoindentation method is based on the method of ISO 14577 and can be performed under the conditions of a load of 0.5 mN, a load time of 0.1 seconds, a load holding time of 0.1 seconds, and an unloading time of 0.1 seconds.

[0065] Example The embodiments are described in more detail below. However, the embodiments are not limited to these embodiments.

[0066] The Making of Hard Alloy The cemented carbide involved in making specimens 1 to 19 and specimens 101 to 114 is as follows.

[0067] <Preparation Process> As raw material powders, WC powder (average particle size: 1 μm), Co powder (average particle size: 1 μm), first element powder, and TiCN powder (average particle size: 1 μm) were prepared. As first element powders, Si powder (average particle size: 1 μm), Ge powder (average particle size: 1 μm), Sn powder (average particle size: 1 μm), Os powder (average particle size: 1 μm), Ir powder (average particle size: 1 μm), Pt powder (average particle size: 1 μm), P powder (average particle size: 1 μm), Re powder (average particle size: 1 μm), and Ru powder (average particle size: 1 μm) were prepared.

[0068] <Mixed Processes> Mix the raw material powders in the proportions shown in Table 1 and Table 2 using a grinder for 10 hours to obtain a mixed powder.

[0069] <Forming process> By stamping or extruding the mixed powder, a formed body in the shape of a round bar is obtained.

[0070] <Sintering process> Heat the formed body to the temperatures shown in Table 1 and Table 2 and hold it at that temperature for the holding times shown in Table 1 and Table 2 to obtain a cemented carbide intermediate.

[0071] <Cooling process> Cool the cemented carbide intermediate to 800 °C at the cooling rates shown in Table 1 and Table 2.

[0072] <HIP process> Perform HIP treatment on the cemented carbide intermediate after the cooling process under the conditions shown in Table 1 and Table 2 to obtain a cemented carbide.

[0073] Through the above steps, cemented carbides related to Specimens 1 to 19 and Specimens 101 to 114 are produced.

[0074] [Table 1]

[0075] [Table 2]

[0076] [Table 3]

[0077] [Table 4]

[0078] 《Evaluation of the properties of cemented carbides》 <Content rate of tungsten carbide particles> For the cemented carbides related to each specimen, the content rate of tungsten carbide particles is determined by the method described in Embodiment 1. The obtained results are shown in the column of "Content rate of WC particles [vol.%]" in Table 3 and Table 4. In addition, when it is described as "balance" in the column of "Content rate of WC particles [vol.%]" in Table 3 and Table 4, it means that the content rate of tungsten carbide particles is a value equal to the value obtained by subtracting the value described in the column of "Content rate of the binder phase [vol.%]" in Table 3 and Table 4 from the value described in the column of "Total [vol.%]" in Table 3 and Table 4.

[0079] <Content rate of the binder phase> For each sample of cemented carbide, the content of the bonding phase was determined using the method described in Example 1. The results are recorded in the "Content of Bonding Phase [volume %]" column of Tables 3 and 4.

[0080] <Hardness of the bonding phase> For each sample of cemented carbide, the hardness of the bonding phase was determined using the method described in Example 1. The results are recorded in the "Hardness of Bonding Phase [GPa]" column of Tables 3 and 4.

[0081] <Cobalt content in cemented carbide> For each cemented carbide sample, the cobalt content in the cemented carbide was determined using the method described in Example 1. The results are recorded in the "Co content [mass %]" column of Tables 3 and 4. Furthermore, regarding the cemented carbide samples, it was confirmed using the method described in Example 1 that "cobalt in cemented carbide 3 exists only in the bonding phase 2".

[0082] <Content of the first element in cemented carbide> For each sample of cemented carbide, the content of the first element in the cemented carbide was determined by the method described in Embodiment 1. The results were recorded in the "First Element Content [mass%]" column of Tables 3 and 4. Furthermore, for each sample of cemented carbide, when the "First Element Content [mass%]" was not 0 mass%, the method described in Embodiment 1 confirmed that "the first element in cemented carbide 3 exists only in the bonding phase 2".

[0083] <{M1 / (M1+M2)}×100> For each sample of cemented carbide, {M1 / (M1+M2)}×100 was calculated using the method described in Example 1. The results were recorded in the "{M1 / (M1+M2)}×100[%]" column of Tables 3 and 4.

[0084] Cutting Test First, three end mills (GSXB20000 type) with a cutting diameter of φ6mm were fabricated for each specimen by machining the carbide round bars involved in the specimens. Next, using the end mills of each specimen, cutting was performed under the following cutting conditions, and the cutting distance until the end mill showed wear of 0.05mm was measured. For each specimen, the average cutting distance of the three end mills was calculated to obtain the cutting length. The results are recorded in the "Cutting Length [m]" column of Tables 3 and 4, respectively. Furthermore, a longer cutting length indicates a longer tool life.

[0085] <Cutting Conditions> Material to be cut: SKD51 (high hardness material) Cutting speed Vc: 180m / min Feed rate Fz per blade: 0.15mm / t Cutting depth Ap: 0.5mm Cutting fluid: Available (wet type) The cutting conditions described above are equivalent to the cutting of high-hardness materials.

[0086] The cemented carbide used in samples 1 to 19 corresponds to the examples. The cemented carbide used in samples 101 to 114 corresponds to the comparative examples. As can be seen from the results in Tables 3 and 4, the cemented carbide used in samples 1 to 19, compared with the cemented carbide used in samples 101 to 114, can achieve a longer tool life even when used as the material for cutting tools for machining high-hardness materials.

[0087] As can be seen from the above, the cemented carbide involved in samples 1 to 19 can achieve a long tool life even when used as a material for cutting tools for machining high-hardness materials.

[0088] 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.

[0089] 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.

[0090] Explanation of reference numerals in the attached figures 1: Tungsten carbide particles; 2: Binding phase; 3: Hard alloy.

Claims

1. A cemented carbide comprising a bonding phase and a plurality of tungsten carbide particles, wherein, The cemented carbide comprises a total of 89% by volume or more of the tungsten carbide particles and the bonding phase. The cemented carbide comprises 1.8 vol% or more and 20.0 vol% or less of the bonding phase. The bonding phase contains cobalt. The cemented carbide contains more than 1.0% by mass of cobalt. The hardness of the bonding phase, measured by nanoindentation at 25°C, is above 7.0 GPa.

2. The cemented carbide according to claim 1, wherein, The bonding phase further comprises a first element. The first element is at least one element selected from the group consisting of silicon, phosphorus, germanium, tin, rhenium, ruthenium, osmium, iridium and platinum.

3. The cemented carbide according to claim 2, wherein, In the combined phase, the percentage of the mass M1 of the first element relative to the total mass M1+M2 of the first element and the mass M2 of cobalt, {M1 / (M1+M2)}×100, is 1% or more and 6% or less.

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