Hard alloy

Abstract

A cemented carbide provided with a plurality of tungsten carbide particles and a binding phase, the cemented carbide containing a total of 89 vol% or more of the tungsten carbide particles and the binding phase, the cemented carbide containing 1.8 vol% or more and 20.0 vol% or less of the binding phase, the binding phase containing cobalt, the cemented carbide containing 1.0 mass% or more of cobalt, and the balance being cemented carbide. The percentage (Y2 / Y1) * 100 of the Young's modulus (Y2 GPa) at 600 DEG C of the binder phase measured by a nanoindentation method with respect to the Young's modulus (Y1 GPa) at 25 DEG C is 50% or more.

Description

Technical Field

[0001] The present disclosure relates to cemented carbides. Background Art

[0002] Conventionally, cemented carbide including a plurality of tungsten carbide particles and a binder phase has been used as a material for cutting tools (Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2004-131769 Summary of the Invention

[0006] The cemented carbide disclosed herein comprises a plurality of tungsten carbide particles and a binder phase, wherein:

[0007] The cemented carbide contains more than 89% by volume of the tungsten carbide particles and the binder phase.

[0008] The cemented carbide contains 1.8 volume % or more and 20.0 volume % or less of the binder phase,

[0009] The binding phase comprises cobalt,

[0010] The cemented carbide contains 1.0 mass % or more of cobalt,

[0011] The percentage (Y2 / Y1)×100 of the Young's modulus Y2 GPa at 600° C. to the Young's modulus Y1 GPa at 25° C. of the binder phase measured by nanoindentation is 50% or more. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a diagram schematically showing a cross section of a cemented carbide according to one embodiment of the present disclosure. DETAILED DESCRIPTION

[0013] [Problems to be Solved by the Present Disclosure]

[0014] In recent years, the difficulty of cutting materials has intensified, and the operating conditions of cutting tools have become increasingly demanding. Consequently, cemented carbides used as cutting tool substrates are also being demanded to have improved properties. In particular, cemented carbides are being sought that can extend tool life, even when used as materials for high-speed machining of difficult-to-cut materials with high tensile strength.

[0015] Therefore, an object of the present disclosure is to provide a cemented carbide that can extend the life of a tool, particularly when used as a material for a cutting tool for high-speed machining of difficult-to-cut materials having high tensile strength.

[0016] [Effects of the Present Disclosure]

[0017] According to the present disclosure, it is possible to provide a cemented carbide capable of extending the life of a tool, particularly when used as a material for a cutting tool for high-speed machining of difficult-to-cut materials having high tensile strength.

[0018] [Description of Embodiments of the Present Disclosure]

[0019] First, embodiments of the present disclosure will be listed and described.

[0020] (1) The cemented carbide disclosed herein comprises a plurality of tungsten carbide particles and a binder phase, wherein:

[0021] The cemented carbide contains 89% or more of the tungsten carbide particles and the binder phase in total,

[0022] The cemented carbide contains 1.8 volume % or more and 20.0 volume % or less of the binder phase,

[0023] The binding phase comprises cobalt,

[0024] The cemented carbide contains 1.0 mass % or more of cobalt,

[0025] The percentage (Y2 / Y1)×100 of the Young's modulus Y2 GPa of the binder phase at 600° C. to the Young's modulus Y1 GPa at 25° C. measured by nanoindentation is 50% or more.

[0026] According to the present disclosure, it is possible to provide a cemented carbide capable of extending the life of a tool, particularly when used as a material for a cutting tool for high-speed machining of difficult-to-cut materials having high tensile strength.

[0027] (2) In the above (1), the percentage (Y2 / Y1)×100 may be 70% or more. This provides a cemented carbide that can further extend the tool life of cutting tools, particularly in high-speed machining of difficult-to-cut materials with high tensile strength.

[0028] (3) In the above (1) or (2), the Young's modulus Y1 may be greater than 170 GPa. This provides a cemented carbide that can further extend the tool life of cutting tools, particularly in high-speed machining of difficult-to-cut materials with high tensile strength.

[0029] (4) In any one of the above (1) to (3), the binding phase may further contain a first element,

[0030] 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, particularly in high-speed machining of difficult-to-cut materials with high tensile strength.

[0031] (5) In the above (4), in the binder phase, the percentage of the mass M1 of the first element to the total M1+M2 of the mass M1 of the first element and the mass M2 of cobalt {M1 / (M1+M2)}×100 is 1% or more and 6% or less. Thus, a cemented carbide can be provided that can further extend the tool life of a cutting tool, particularly in high-speed machining of difficult-to-cut materials with high tensile strength.

[0032] [Details of the embodiments of the present disclosure]

[0033] A specific example of a cutting tool according to one embodiment of the present disclosure (hereinafter also referred to as "this embodiment") is described below with reference to the accompanying drawings. In the drawings of the present disclosure, identical reference numerals represent identical or equivalent parts. Furthermore, dimensional relationships such as length, width, thickness, and depth have been modified as appropriate for clarity and simplicity in the drawings and do not necessarily represent actual dimensional relationships.

[0034] In the present disclosure, expressions in the form of "A to B" refer to the upper and lower limits of a range (i.e., greater than A and less than B). When there is no unit recorded in A and only the unit is recorded in B, the unit of A is the same as the unit of B.

[0035] In the present disclosure, when compounds and the like are represented by chemical formulae, unless there is a particular limitation on the atomic ratio, all conventionally known atomic ratios are encompassed and the atomic ratio is not necessarily limited to the atomic ratio within the stoichiometric range.

[0036] [Implementation method 1: cemented carbide]

[0037] use Figure 1 A cemented carbide according to an embodiment of the present disclosure will be described.

[0038] One embodiment of the present disclosure (hereinafter also referred to as "this embodiment") is a cemented carbide 3 including a plurality of tungsten carbide particles 1 and a binder phase 2, wherein:

[0039] The cemented carbide 3 contains the tungsten carbide particles 1 and the binder phase 2 in total of more than 89 volume %.

[0040] The cemented carbide 3 contains 1.8 volume % or more and 20.0 volume % or less of the binder phase 2,

[0041] The binding phase 2 comprises cobalt,

[0042] The cemented carbide 3 contains 1.0 mass % or more of cobalt.

[0043] The percentage (Y2 / Y1)×100 of the Young's modulus Y2 GPa at 600° C. to the Young's modulus Y1 GPa at 25° C. of the binder phase 2 measured by nanoindentation is 50% or more.

[0044] According to the present disclosure, it is possible to provide a cemented carbide 3 that can extend the life of a cutting tool, particularly when used as a material for high-speed machining of difficult-to-cut materials with high tensile strength. The reason for this is presumably as follows.

[0045] The cemented carbide 3 of this embodiment includes a plurality of tungsten carbide particles 1 (hereinafter also referred to as "WC particles 1") and a binder phase 2. The total content of the WC particles 1 and the binder phase 2 in the cemented carbide 3 is 89% by volume or more. As a result, the cemented carbide 3 has high hardness and strength, and a cutting tool using the cemented carbide 3 can have excellent wear resistance and defect resistance.

[0046] The cemented carbide 3 of the first embodiment includes a binder phase 2 of 1.8% by volume or more and 20.0% by volume or less, the binder phase 2 including cobalt, and the cemented carbide 3 includes cobalt of 1.0% by mass or more. Furthermore, the percentage (Y2 / Y1) × 100 of the Young's modulus Y2 GPa of the binder phase 2 at 600°C relative to the Young's modulus Y1 GPa at 25°C, measured by nanoindentation, is 50% or more, which can suppress the "decrease in the Young's modulus of the cemented carbide 3" that occurs when the condition changes from 25°C (in other words, room temperature) to 600°C (in other words, high temperature). As a result, the "decrease in the Young's modulus of the cemented carbide 3" is suppressed, and a cutting tool using the cemented carbide 3 can have excellent defect resistance, particularly in high-speed machining of difficult-to-cut materials with high tensile strength.

[0047] Composition of Cemented Carbide

[0048] The cemented carbide 3 contains tungsten carbide particles 1 and a binder phase 2 in a total amount of 89% by volume or more. Thus, the hardness of the cemented carbide 3 can be increased. The cemented carbide 3 may contain tungsten carbide particles 1 and a binder phase 2 in a total amount of 90% by volume or more, may contain tungsten carbide particles 1 and a binder phase 2 in a total amount of 91% by volume or more, or may contain tungsten carbide particles 1 and a binder phase 2 in a total amount of 92% by volume or more. In the cemented carbide 3, the upper limit of the total content of tungsten carbide particles 1 and a binder phase 2 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 a binder phase 2 in a total amount of 90% by volume or more and 100% by volume or less, may contain tungsten carbide particles 1 and a binder phase 2 in a total amount of 91% by volume or more and 100% by volume or less, or may contain tungsten carbide particles 1 and a binder phase 2 in a total amount of 92% by volume or more and 100% by volume or less.

[0049] Cemented carbide 3 comprises a binder phase 2 having a content of more than 1.8% by volume and less than 20.0% by volume. Thus, in cemented carbide 3, Young's modulus and toughness can be improved. The lower limit of the content of the binder phase 2 in cemented carbide 3 can be more than 2.0% by volume, can be more than 3.0% by volume, or can be more than 4.0% by volume. The upper limit of the content of the binder phase 2 in cemented carbide 3 can be less than 19.0% by volume, can be less than 18.0% by volume, or can be less than 17.0% by volume. Cemented carbide 3 can comprise a binder phase 2 having a content of more than 2.0% by volume and less than 19.0% by volume, can comprise a binder phase 2 having a content of more than 3.0% by volume and less than 18.0% by volume, or can comprise a binder phase 2 having a content of more than 4.0% by volume and less than 17.0% by volume.

[0050] The cemented carbide 3 of the first embodiment can be composed of a plurality of tungsten carbide particles 1 and a binder phase 2. The cemented carbide 3 of this embodiment can contain other phases (not shown) in addition to the tungsten carbide particles 1 and the binder phase 2. 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). Examples of other phases include TiCN, TaC, NbC, ZrC, HfC, and Mo2C.

[0051] The cemented carbide 3 of embodiment one can be made of tungsten carbide particles 1, binding phase 2, other phases. The containing ratio of other phases of cemented carbide 3 is allowed in the scope of not damaging the effect of the present disclosure. For example, the containing ratio of other phases of cemented carbide 3 can be to exceed 0 volume % and be below 20 volume %, can be to exceed 0 volume % and be below 18 volume %, can also be to exceed 0 volume % and be below 16 volume %. In this case, the total containing ratio of the tungsten carbide particles 1 of cemented carbide 3 and binding phase 2 can be more than 80 volume % and be less than 100 volume %, can be more than 82 volume % and be less than 100 volume %, can also be more than 84 volume % and be less than 100 volume %.

[0052] The cemented carbide 3 of the first embodiment can contain impurities. Examples of such impurities include iron (Fe), calcium (Ca), oxygen (O), and sulfur (S). The impurity content of the cemented carbide 3 is permitted within a range that does not impair the effects of the present 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 measured by ICP emission analysis (Inductively Coupled Plasma Emission Spectroscopy (measurement device: Shimadzu Corporation "ICPS-8100" (trademark)).

[0053] The content rate (volume %) of the tungsten carbide particles 1 in the cemented carbide 3 and the content rate (volume %) of the binder phase 2 in the cemented carbide 3 are measured as follows.

[0054] (A1) A cemented carbide 3 is cut at an arbitrary position to expose a cross section, and the cross section is mirror-finished using a cross section polisher (manufactured by JEOL Ltd.).

[0055] (B1) The mirror-finished surface of the cemented carbide 3 was analyzed by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) (apparatus: "Gemini 450" (trademark) manufactured by Carl Zeiss) to determine the elements contained in the cemented carbide 3.

[0056] (C1) A reflected electron image was obtained by photographing the mirror-finished surface of the cemented carbide 3 using a scanning electron microscope (SEM). The photographing area of the photographed image was set to exclude the central portion of the cross section of the cemented carbide 3, i.e., the portion having properties significantly different from the bulk portion, such as the vicinity of the surface of the cemented carbide 3 (the photographing area was entirely the bulk portion of the cemented carbide 3). The observation magnification was 5000 times. The measurement conditions were an accelerating voltage of 3 kV, a current of 2 nA, and a working distance (WD) of 5 mm.

[0057] (D1) The imaging area of (C1) is analyzed using an energy dispersive X-ray analyzer (SEM-EDX) attached to the SEM to determine the distribution of the elements determined by (B1) in the imaging area and obtain an element mapping image.

[0058] (E1) The reflected electron image obtained in (C1) above was loaded into a computer and binarized using image analysis software (OpenCV, SciPy). In the binarized image, the tungsten carbide particles 1 are represented by white, and the binder phase 2 is represented by gray to black. The binarization threshold varies depending on the contrast, so it is set for each image.

[0059] (F1) The elemental mapping image obtained in (D1) is superimposed on the binarized image obtained in (E1), thereby identifying the regions where the tungsten carbide particles 1 and the binder phase 2 are present. Specifically, regions represented by white in the binarized image and containing tungsten (W) and carbon (C) correspond to regions where the tungsten carbide particles 1 are present. Regions represented by gray to black in the binarized image and containing cobalt (Co) correspond to regions where the binder phase 2 is present.

[0060] (G1) In the binarized image, a rectangular measurement field of 24.9 μm × 18.8 μm was set, and the area percentages of the tungsten carbide particles 1 and the binder phase 2 were measured using the image analysis software, with the area of the entire measurement field as the denominator.

[0061] (H1) The measurement of (G1) above is performed in five different measurement fields that do not overlap. In this specification, the average of the area percentages of the tungsten carbide particles 1 in the five measurement fields corresponds to the content [volume %] of the tungsten carbide particles 1 in the cemented carbide 2, and the average of the area percentages of the binder phase 2 in the five measurement fields corresponds to the content [volume %] of the binder phase 2 in the cemented carbide 3.

[0062] In the case where the cemented carbide 3 contains other phases in addition to the tungsten carbide particles 1 and the binder phase 2, the content of the other phases in the cemented carbide 3 can be obtained by subtracting the content [volume %] of the tungsten carbide particles 1 and the content [volume %] of the binder phase 2 measured by the above steps from the entire cemented carbide 3 (100 volume %).

[0063] It was confirmed that as long as it is within the range measured by the applicant and as long as the measurement is performed on the same sample, even if the cutting position of the cross section of the cemented carbide 3 is arbitrarily set and the shooting area described in the above (C1) is arbitrarily set on the cross section, the content of the tungsten carbide particles 1 and the content of the binder phase 2 of the 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.

[0064] Combination Phase

[0065] The binder phase 2 contains cobalt, and the cemented carbide 3 contains 1.0% by mass or more of cobalt. Thus, it is possible to impart excellent toughness to the cemented carbide 3. In addition, the binder phase 2 may contain 50% by mass or more of cobalt, 60% by mass or more of cobalt, 70% by mass or more of cobalt, 80% by mass or more of cobalt, 90% by mass or more of cobalt, or 95% by mass or more of cobalt. The binder phase 2 may also be composed of cobalt. In addition, the binder phase 2 may also be composed of cobalt and the first element described later. In addition, the cobalt in the cemented carbide 3 may also be present only in the binder phase 2. The lower limit of the cobalt content in the cemented carbide 3 may be 2.0% by mass or more, 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, 15% by mass or less, 12% by mass or less, or 10% by mass or less. The cemented carbide 3 may contain 1.0 mass % to 20 mass % of cobalt, 2.0 mass % to 15 mass % to no greater than 15 mass % of cobalt, or 3.0 mass % to 12 mass % to no greater than 12 mass % of cobalt.

[0066] The method for determining the cobalt content in cemented carbide 3 is as follows. First, the imaging area is set by the same method as (A1) to (C1) of the above-mentioned method for determining the content of tungsten carbide particles 1 and the content of binder phase 2 in cemented carbide 3. Next, the imaging area is analyzed using SEM-EDX to determine the distribution of the elements determined by (B1) in the imaging area, and an element mapping image is obtained, while determining the cobalt content in cemented carbide 3. In addition, the method for determining the "cobalt content in binder phase 2" is as follows. First, the area where binder phase 2 exists is determined on the image after binarization processing by the same method as (A1) to (F1) of the above-mentioned method for determining the content of tungsten carbide particles 1 and the content of binder phase 2 in cemented carbide 3. Next, the area where binder phase 2 exists is analyzed using SEM-EDX to determine the "cobalt content in binder phase 2". In addition, the method for determining "the case where cobalt in cemented carbide 3 exists only in binder phase 2" is as follows. First, the areas where the tungsten carbide particles 1 and the binder phase 2 are present are determined on the binarized image using the same method as (A1) to (F1) of the aforementioned method for measuring the content of the tungsten carbide particles 1 and the content of the binder phase 2 in the cemented carbide 3. Next, based on the elemental mapping image, the areas where the tungsten carbide particles 1 and the binder phase 2 are present, it is determined that "the cobalt in the cemented carbide 3 is present only in the binder phase 2."

[0067] It was confirmed that as long as the measurement is within the range determined by the applicant and the measurement is performed on the same sample, even if the cutting position of the cross section of the cemented carbide 3 and the shooting area described in (C1) above are arbitrarily set, and the above-mentioned measurement is performed multiple times in accordance with the above-mentioned steps, the deviation of the measurement results is small and will not change arbitrarily.

[0068] The binder phase 2 further includes 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. This provides a cemented carbide 3 that can further extend the tool life of cutting tools, particularly during high-speed machining of difficult-to-cut materials with high tensile strength.

[0069] The content of the first element in the cemented carbide 3 can be 0.01% by mass or more and 1.0% by mass or less. Thus, the bonding phase 2 can have both a more excellent Young's modulus and a more excellent toughness. In addition, the content of the first element in the bonding phase 2 can be 50% by mass or less, 40% by mass or less, 30% by mass or less, 20% by mass or less, 10% by mass or less, or 5% by mass or less. The first element in the cemented carbide 3 can also only be present in the bonding phase 2. The lower limit of the content of the first element in the cemented carbide 3 can be 0.01% by mass or more, 0.04% by mass or more, or 0.1% by mass or more. The upper limit of the content of the first element in the cemented carbide 3 can be 1.0% by mass or less, 0.8% by mass or less, or 0.6% by mass or less. The content of the first element in the 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.

[0070] The method for determining the content of the first element in the cemented carbide 3 is as follows. Except for the point where "cobalt" is replaced by "first element", the method is the same as the method for determining the content of cobalt in the cemented carbide 3. In addition, the method for determining the "content of the first element in the bonding phase 2" is as follows. Except for the point where "Next, ... determine the 'content of 'cobalt' in the bonding phase 2'." is replaced by "Next, ... determine the 'content of 'first element' in the bonding phase 2'.", the method is the same as the method for determining the "case where the first element in the cemented carbide 3 exists only in the bonding phase 2". In addition, the method for determining the "case where the first element in the cemented carbide 3 exists only in the bonding phase 2" is as follows. Except for the point where "Next, ... determine the 'case where 'cobalt' in the cemented carbide 3 exists only in the bonding phase 2'." is replaced by "Next, ... determine the 'case where 'first element' in the cemented carbide 3 exists only in the bonding phase 2'.", the method is the same as the method for determining the "case where cobalt in the cemented carbide 3 exists only in the bonding phase 2".

[0071] It was confirmed that as long as the measurement is within the range determined by the applicant and the measurement is performed on the same sample, even if the cutting position of the cross section of the cemented carbide 3 and the shooting area described in (C1) above are arbitrarily set, and the above-mentioned measurement is performed multiple times in accordance with the above-mentioned steps, the deviation of the measurement results is small and will not change arbitrarily.

[0072] In the bonding phase 2, the percentage of the mass M1 of the first element to the total M1+M2 of the mass M1 of the first element and the mass M2 of cobalt {M1 / (M1+M2)}×100 can be greater than 1% and less than 6%. As a result, the bonding phase 2 can have both a better Young's modulus and better toughness, thereby being able to provide a cemented carbide 3 that can further extend the tool life of the cutting tool, especially in high-speed processing of difficult-to-cut materials with high tensile strength. Here, in the case where 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 the percentage {M1 / (M1+M2)}×100 can be greater than 1%, greater than 2%, or greater than 3%. The upper limit of the percentage {M1 / (M1+M2)}×100 can be less than 6%, less than 5%, or less than 4%. The percentage {M1 / (M1+M2)}×100 may be 2% or more and 5% or less, or 3% or more and 4% or less.

[0073] The method for determining the above-mentioned percentage {M1 / (M1+M2)}×100 is as follows. The area where the binding phase 2 exists is determined on the image after binarization by the same method as (A1) to (F1) of the method for determining the content of tungsten carbide particles 1 and the content of the binding phase 2 in the above-mentioned cemented carbide 3. The area where the binding phase 2 exists is analyzed using SEM-EDX, and the cobalt content and the first element content in the binding phase 2 are measured. Based on this, the percentage {M1 / (M1+M2)}×100 is calculated. The above-mentioned measurement is performed in five different measurement fields that do not overlap with each other. In this specification, the average of the percentages {M1 / (M1+M2)}×100 in the five measurement fields is equivalent to the "percentage {M1 / (M1+M2)}×100" in the binding phase 2.

[0074] It was confirmed that as long as it is within the range measured by the applicant and as long as the measurement is performed on the same sample, even if the cutting position of the cross section of the cemented carbide 3 and the shooting area described in (C1) above are arbitrarily set, and the percentage {M1 / (M1+M2)}×100 is measured multiple times in accordance with the above steps, the deviation of the measurement results is small and will not change arbitrarily.

[0075] Young's modulus of the binder phase

[0076] The percentage (Y2 / Y1)×100 of the Young's modulus Y2GPa of the bonding phase 2 at 600°C relative to the Young's modulus Y1GPa at 25°C measured by the nanoindentation method is 50% or more. Thus, it is possible to suppress the "reduction in the Young's modulus of the cemented carbide 3" that occurs when the condition changes from 25°C (in other words, under room temperature) to 600°C (in other words, under high temperature). The lower limit of the percentage (Y2 / Y1)×100 can be 55% or more, 60% or more, or 70% or more. The upper limit of the percentage (Y2 / Y1)×100 can be 85% or less, 80% or less, or 75% or less. The percentage (Y2 / Y1)×100 can be 50% or more and 85% or less, 55% or more and 80% or less, or 60% or more and 75% or less.

[0077] Young's modulus Y1 can be more than 170GPa.Thus, cemented carbide 3 can have more excellent defect resistance.The lower limit of Young's modulus Y1 can be more than 170GPa, can be more than 175GPa, also can be more than 180GPa.The upper limit of Young's modulus Y1 can be less than 200GPa, can be less than 195GPa, also can be less than 193GPa.Young's modulus Y1 can be more than 170GPa and less than 200GPa, can be more than 175GPa and less than 195GPa, also can be more than 180GPa and less than 193GPa.

[0078] Young's modulus Y2 can be more than 85GPa.Thus, cemented carbide 3 can have more excellent defect resistance.The lower limit of Young's modulus Y2 can be more than 85GPa, can be more than 90GPa, also can be more than 95GPa.The upper limit of Young's modulus Y2 can be less than 140GPa, can be less than 137GPa, also can be less than 134GPa.Young's modulus Y2 can be more than 85GPa and less than 140GPa, can be more than 90GPa and less than 137GPa, also can be more than 95GPa and less than 134GPa.

[0079] The Young's modulus Y1GPa and the Young's modulus Y2GPa are measured by nanoindentation ("Hysitron TI 980TriboIndenter" manufactured by Bruker). The nanoindentation method is a method that complies with ISO14577 and is performed under the conditions of a measuring load of 0.5mN, a loading time of 0.1 seconds, a load holding time of 0.1 seconds, and an unloading time of 0.1 seconds. The measurement object is each of 10 arbitrary binder phases 2 exposed by grinding the surface of the cemented carbide 3 using a CROSS SECTION POLISHER (CP) processing device ("IB-19500CP cross-section sample preparation device" (trademark) manufactured by JEOL Ltd.). The average value of the Young's modulus of each of the 10 binder phases 2 measured at 25°C is the Young's modulus Y1GPa. In addition, the average value of the Young's modulus of each of the 10 binder phases 2 measured at 600°C is the Young's modulus Y2GPa.

[0080] It was confirmed that, within the measurement range of the applicant and as long as the measurement was performed on the same sample, even if arbitrarily 10 binder phases 2 were used and the Young's modulus of the binder phase 2 was measured multiple times, the measurement results had little deviation and did not change arbitrarily.

[0081] Tungsten Carbide Particles

[0082] In the first embodiment, the tungsten carbide particles 1 include at least one of "pure WC particles (including WC free of all impurity elements and WC with an impurity element content below the detection limit)" and "WC particles that intentionally or inevitably contain impurity elements, as long as the effects of the present disclosure are not impaired." The impurity content of the tungsten carbide particles (when the impurities are composed of two or more elements, the total content of these elements) is less than 0.1% by mass. The impurity element content of the tungsten carbide particles is measured by ICP emission spectrometry (measurement apparatus: "ICPS-8100" (trademark) manufactured by Shimadzu Corporation)

[0083] In the first embodiment, there is no particular limitation on the average particle size of the tungsten carbide particles 1. 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 the first embodiment can have a long tool life regardless of the average particle size of the tungsten carbide particles 1.

[0084] Uses of Cemented Carbide

[0085] The cemented carbide 3 of this embodiment can be used in cutting tools. Examples of such cutting tools include general-purpose cutting tools. More specifically, cutting tools 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, and taps.

[0086] [Implementation Method 2: Method for Manufacturing Cemented Carbide]

[0087] The cemented carbide of this embodiment can be produced by performing the raw material powder preparation step, mixing step, forming step, sintering step, first cooling step, heating step, HIP (Hot Isostatic Pressing) step, and second cooling step in the above order. Each step is described below.

[0088] <Preparation process>

[0089] The preparation process is a process of preparing raw material powders of materials constituting cemented carbide. Examples of raw material powders include tungsten carbide powder (hereinafter also referred to as "WC powder") and cobalt (Co) powder. On the basis of these raw material powders, first element powder, niobium carbide (NbC) powder, tungsten carbide (TaC) powder, titanium carbonitride (TiCN) powder, and zirconium carbide (ZrC) powder can be prepared. Commercially available raw material powders can be used for these raw material powders. There is no particular limitation on the average particle size of these raw material powders, and for example, it can be set to 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: Fisher Particle Size Analyzer) method. The average particle size is measured using "Sub-Sieve Sizer Model 95" (trademark) manufactured by Fisher Scientific.

[0090] <Mixing process>

[0091] The mixing step is a step of mixing the raw material powders prepared in the preparation step in a predetermined ratio. Through the mixing step, a mixed powder of the raw material powders is obtained. The mixing ratio of the raw material powders is appropriately adjusted according to the composition of the target cemented carbide. The first element powder can also be used as the raw material powder. As a result, it is easier to make the cemented carbide have the desired "percentage (Y2 / Y1) × 100" because it is easy to make the orientation of the crystals of the binder phase consistent. By appropriately adjusting the amount of each raw material powder added, the content of the binder phase and the content of the WC particles can be made within the desired range.

[0092] The raw material powders can be mixed using a conventional mixing method such as an attritor, a ball mill, or a bead mill. Conventional mixing conditions can also be used. The mixing time can be set to, for example, 2 hours to 20 hours.

[0093] After the mixing step, the mixed powder may be granulated as needed. Granulating the mixed powder makes it easier to fill the die or mold with the mixed powder during the forming step described later. For granulation, a known granulation method can be applied, for example, a commercially available granulator such as a spray dryer can be used.

[0094] <Forming process>

[0095] The forming step is a step of forming the mixed powder obtained in the mixing step into a shape for a cutting tool to obtain a formed body. The forming method and forming conditions in the forming step can be general methods and conditions and are not particularly limited.

[0096] <Sintering process>

[0097] The sintering step is a step of sintering the compact obtained in the forming step to obtain a cemented carbide intermediate. The sintering conditions in this embodiment are as follows: The compact is heated to 1340°C and maintained at 1340°C for 2 hours.

[0098] <First Cooling Step>

[0099] The first cooling step is a step of cooling the cemented carbide intermediate body. More specifically, the cemented carbide intermediate body is cooled to 1000° C. The cooling rate is not particularly limited, and can be, for example, 20° C. / minute.

[0100] <Heating process>

[0101] The heating step is a step of heating the cemented carbide intermediate body. More specifically, the heating temperature is 1200° C. and the holding time at this temperature is 0.25 hours.

[0102] HIP process

[0103] The HIP process is a process of performing HIP treatment on the cemented carbide intermediate. The conditions of the HIP process in this embodiment are as follows: The cemented carbide intermediate is maintained at a pressure of 10 MPa for 4 hours.

[0104] <Second Cooling Step>

[0105] The second cooling step is a step of cooling the cemented carbide intermediate body. More specifically, the cemented carbide intermediate body is cooled to 800° C. The cooling rate is 2° C. / minute. In this way, the cemented carbide of the first embodiment can be obtained.

[0106] <Features of the Cemented Carbide Manufacturing Method of the Present Embodiment>

[0107] In this embodiment, the sintering process is performed by heating the formed body to 1340°C and holding it at 1340°C for 2 hours. Furthermore, the first cooling process is performed by cooling the cemented carbide intermediate to 1000°C. Furthermore, the heating process is performed under the conditions of a temperature of 1200°C and a holding time of 0.25 hours. Furthermore, the HIP process is performed under the conditions of a pressure of 10 MPa and a time of 4 hours. Furthermore, the second cooling process is performed by setting the cooling rate until reaching 800°C to 2°C / minute. Through these processes, a cemented carbide can be produced in which the percentage (Y2 / Y1)×100 of the Young's modulus Y2GPa of the binder phase at 600°C relative to the Young's modulus Y1GPa at 25°C measured by nanoindentation is 50% or more. The fact that the cemented carbide disclosed herein can be achieved through such sintering conditions, the first cooling process, the heating process, the HIP process, and the second cooling process is a new discovery made by the inventors as a result of their in-depth research.

[0108] [Note 1]

[0109] In the cemented carbide of the first embodiment, the nanoindentation method can be performed according to ISO 14577 under the conditions of a measurement load of 0.5 mN, a loading time of 0.1 second, a load holding time of 0.1 second, and an unloading time of 0.1 second.

[0110] Example

[0111] This embodiment will be described in more detail with reference to examples, but this embodiment is not limited to these examples.

[0112] Production of Cemented Carbide

[0113] By executing the following steps in the following order, cemented carbides according to Samples 1 to 21 and Samples 101 to 114 were produced.

[0114] <Preparation process>

[0115] 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.

[0116] <Mixing process>

[0117] The raw material powders were mixed for 10 hours using an attritor at the ratios listed in Tables 1 and 2 to obtain a mixed powder.

[0118] <Forming process>

[0119] The mixed powder is press-formed or extruded to obtain a round rod-shaped compact.

[0120] <Sintering process>

[0121] The formed body was heated to the temperature listed in Tables 1 and 2 and maintained at that temperature for the holding time listed in Tables 1 and 2 to obtain a cemented carbide intermediate body.

[0122] <First Cooling Step>

[0123] The cemented carbide intermediate body was cooled to the temperature listed in Tables 3 and 4. In the "First Cooling Step" column, when "-" is listed in the "Temperature [°C]" column, it means that the "first cooling step" was not performed.

[0124] <Heating process>

[0125] The cemented carbide intermediate was heated under the conditions listed in Tables 3 and 4. In the "Heating step" column, if "-" is listed in the "Temperature [°C]" column and the "Holding time [hours]" column, it means that the "heating step" was not performed.

[0126] HIP process

[0127] The cemented carbide intermediate products were subjected to HIP treatment under the conditions described in Tables 3 and 4.

[0128] <Second Cooling Step>

[0129] The cemented carbide intermediate body after the HIP process was cooled to 800° C. at the cooling rates listed in Tables 3 and 4 to obtain cemented carbide.

[0130] Through the above-described steps, cemented carbides according to Samples 1 to 21 and Samples 101 to 114 were produced.

[0131] [Table 1]

[0132]

[0133] [Table 2]

[0134]

[0135] [Table 3]

[0136]

[0137] [Table 4]

[0138]

[0139] [Table 5]

[0140]

[0141] [Table 6]

[0142]

[0143] 《Characteristics Evaluation of Cemented Carbide》

[0144] <Tungsten carbide particle content>

[0145] The tungsten carbide particle content of each sample was determined using the method described in Embodiment 1. The results are reported in the "WC Particle Content [Volume %]" column of Tables 5 and 6. The term "residual" in the "WC Particle Content [Volume %]" column of Tables 5 and 6 indicates that the tungsten carbide particle content is equal to the value obtained by subtracting the value listed in the "Binder Phase Content [Volume %]" column of Tables 5 and 6 from the value listed in the "Total [Volume %]" column of Tables 5 and 6.

[0146] <Content ratio of binder phase>

[0147] The binder phase content of the cemented carbide of each sample was determined by the method described in Embodiment 1. The obtained results are shown in the "Binder Phase Content [Volume %]" column of Tables 5 and 6.

[0148] Young's modulus of the binder phase

[0149] For the cemented carbide involved in each sample, the Young's modulus Y1 of the binder phase was calculated by the method described in the first embodiment. The obtained results are recorded in the "Young's modulus Y1 [GPa] of the binder phase" column of Tables 5 and 6. In addition, for the cemented carbide involved in each sample, the Young's modulus Y2 of the binder phase was calculated by the method described in the first embodiment. The obtained results are recorded in the "Young's modulus Y2 [GPa] of the binder phase" column of Tables 5 and 6. In addition, for the cemented carbide involved in each sample, the method described in the first embodiment confirmed that "the cobalt in the cemented carbide 3 is present only in the binder phase 2."

[0150] <Cobalt Content in Cemented Carbide>

[0151] The cobalt content in the cemented carbide for each sample was determined using the method described in Embodiment 1. The results are reported in the "Co content [mass %]" column in Tables 5 and 6. Furthermore, for each sample, the method described in Embodiment 1 was used to confirm that the cobalt in cemented carbide 3 was present only in binder phase 2.

[0152] <Content ratio of the first element in cemented carbide>

[0153] For each sample of cemented carbide, the content of the first element in the cemented carbide was determined using the method described in Embodiment 1. The results are recorded in the "First Element Content [Mass %]" column of Tables 5 and 6. Furthermore, for each sample of cemented carbide where the "First Element Content [Mass %]" was not 0 mass %, the method described in Embodiment 1 was used to confirm that "the first element in cemented carbide 3 was present only in binder phase 2."

[0154] <{M1 / (M1+M2)}×100>

[0155] For each sample of cemented carbide, {M1 / (M1+M2)}×100 was determined by the method described in Embodiment 1. The obtained results are shown in the "{M1 / (M1+M2)}×100[%]" column in Tables 5 and 6.

[0156] Cutting Test

[0157] First, a round bar made of cemented carbide related to each sample was processed to produce a cutting tool with a blade diameter of Next, each sample end mill was used to perform cutting under the following cutting conditions, and the cutting length until the end mill chipped was measured. The results are reported in the "Cutting Length [m]" column in Tables 5 and 6. A longer cutting length indicates a longer tool life.

[0158] Cutting conditions

[0159] Work material: "waspaloy" (trademark) manufactured by Hanshin Metalics Co., Ltd. (difficult-to-cut material with high tensile strength)

[0160] Cutting speed Vc: 60m / min

[0161] Feed rate per blade Fz: 0.1mm / t

[0162] Axial penetration ap: 1mm

[0163] Radial cutting depth ae: 0.3mm

[0164] Cutting fluid: MQL (Minimum Quantity Lubrication)

[0165] The above cutting conditions are equivalent to high-speed machining of difficult-to-cut materials with high tensile strength.

[0166] The cemented carbides of Samples 1 to 21 correspond to Examples. The cemented carbides of Samples 101 to 114 correspond to Comparative Examples. The results in Tables 5 and 6 show that the cemented carbides of Samples 1 to 21, compared to the cemented carbides of Samples 101 to 114, can achieve longer tool life even when used as cutting tools for high-speed machining of difficult-to-cut materials with high tensile strength.

[0167] As described above, it is understood that the cemented carbides according to Samples 1 to 21 can achieve a longer tool life even when used as materials for cutting tools for high-speed machining of difficult-to-cut materials having high tensile strength.

[0168] As described above, the embodiments and examples of the present disclosure have been described. However, it is anticipated from the outset that the configurations of the above-described embodiments and examples may be appropriately combined or modified in various ways.

[0169] The embodiments and examples disclosed herein are to be considered in all respects as illustrative and non-restrictive. The scope of the present invention is indicated not by the embodiments and examples described above but by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0170] Description of reference numerals:

[0171] 1: Tungsten carbide particles; 2: Binding phase; 3: Cemented carbide.

Claims

1. A cemented carbide comprising a plurality of tungsten carbide particles and a binder phase, wherein: The cemented carbide contains 89% or more of the tungsten carbide particles and the binder phase in total, The cemented carbide contains 1.8 volume % or more and 20.0 volume % or less of the binder phase, The binding phase comprises cobalt, The cemented carbide contains 1.0 mass % or more of cobalt, The percentage (Y2 / Y1)×100 of the Young's modulus Y2 GPa of the binder phase at 600° C. to the Young's modulus Y1 GPa at 25° C. measured by nanoindentation is 50% or more.

2. The cemented carbide according to claim 1, wherein The percentage (Y2 / Y1)×100 is 70% or more.

3. The cemented carbide according to claim 1 or 2, wherein: The Young's modulus Y1 is 170 GPa or more.

4. The cemented carbide according to any one of claims 1 to 3, wherein The binding 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.

5. The cemented carbide according to claim 4, wherein In the binder phase, a percentage {M1 / (M1+M2)}×100 of the mass M1 of the first element to the total M1+M2 of the mass M1 of the first element and the mass M2 of cobalt is 1% or more and 6% or less.

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