Cemented carbide and cutting tool

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 vol% or less of the binding phase, the binding phase containing 80 mass% or more of cobalt, the cemented carbide includes an inner region at a distance of 300 [mu] m or more from the surface, and in the binder phase in the inner region, the percentage {S (hcp) / (S (hcp) + S (fcc))} * 100 of the area S (hcp) with respect to the total of the area S (hcp) of cobalt having an hcp structure and the area S (fcc) of cobalt having an fcc structure is 45% or more.

Description

Technical Field

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

[0002] For a long time, cemented carbide containing multiple tungsten carbide particles and bonding phases has been 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 disclosed cemented carbide comprises multiple tungsten carbide particles and a bonding phase. 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 vol% or less of the bonding phase. The bonding phase contains more than 80% by mass of cobalt. The cemented carbide includes an internal region at a distance of more than 300 μm from the surface. In the bound phase of the internal region, the area S relative to cobalt having an hcp structure (hcp) And the area S of cobalt with an fcc structure (fcc) The total area S (hcp) percentage {S (hcp) / (S (hcp) +S (fcc) )}×100 is more than 45%. Attached Figure Description

[0005] Figure 1 This is a schematic cross-sectional view of the cemented carbide involved in Embodiment 1.

[0006] Figure 2 This is a schematic diagram of the cutting tool involved in Embodiment 2. Detailed Implementation

[0007] [The problem this disclosure aims to solve] In recent years, the difficulty in machining materials has become increasingly apparent, and the operating conditions of cutting tools have become more demanding. Therefore, there is a need to improve the various properties of cemented carbide used as the base material for cutting tools. In particular, there is a demand for cemented carbide and cutting tools incorporating such carbide, even when used as materials for cutting tools requiring intermittent machining of high-strength materials.

[0008] [Effects of the Invention] According to the present disclosure, it is possible to provide a cemented carbide and a cutting tool including the same, which can achieve long tool life even when a material of a cutting tool for intermittent machining, which is a high-strength material, is used.

[0009] [Explanation of Embodiments of the Present Disclosure] First, an embodiment of the present disclosure will be explained.

[0010] (1) The cemented carbide of the present disclosure includes a plurality of tungsten carbide particles and a binder phase, The cemented carbide contains 89% by volume or more of the tungsten carbide particles and the binder phase in total, The cemented carbide contains 1.8% by volume or more and 20% by volume or less of the binder phase, The binder phase contains 80% by mass or more of cobalt, The cemented carbide includes an internal region having a distance of 300 μm or more from a surface, In the binder phase in the internal region, a percentage of the area S (hcp) of cobalt having an fcc structure to a total of the areas S (fcc) of cobalt having an hcp structure and cobalt having an fcc structure is 45% or more. (hcp) (hcp) (hcp) (fcc)

[0011] According to the present disclosure, it is possible to provide a cemented carbide and a cutting tool including the same, which can achieve long tool life even when a material of a cutting tool for intermittent machining, which is a high-strength material, is used.

[0012] (2) In the above (1), the percentage {S (hcp) / (S (hcp) +S (fcc) )} × 100 can be 50% or more and 70% or less. Thus, the deformation resistance of the binder phase is improved, and the cutting tool including the cemented carbide can have a longer tool life.

[0013] (3) In the above (1) or (2), the binder phase can further contain at least one first element selected from the group consisting of silicon, phosphorus, germanium, tin, rhenium, ruthenium, osmium, iridium, and platinum. Thus, the deformation resistance of the binder phase is improved, and the cutting tool including the cemented carbide can have a longer tool life.

[0014] ​​​​(4) In the above (3), the percentage of the mass Ml of the first element with respect to the total Ml+M2 of the mass Ml of the first element and the mass M2 of cobalt {Ml / (Ml+M2)}x100 can also be 1% or more and 6% or less. Thus, the combination phase can have both more excellent hardness and more excellent toughness, and therefore a cutting tool including the cemented carbide having the combination phase can have a longer tool life.

[0015] (5) The cutting tool of the present disclosure is a cutting tool having a cutting edge composed of the cemented carbide described in any one of the above (1) to (4).

[0016] According to the present disclosure, it is possible to provide a cutting tool having a long tool life, particularly in the case of intermittent machining of high-strength materials.

[0017] [Details of the Embodiments of the Present Disclosure] Hereinafter, specific examples of the cemented carbide and the cutting tool of the present disclosure will be described with reference to the accompanying drawings. In the drawings of the present disclosure, the same reference numerals denote the same parts or equivalent parts. In addition, the dimensional relationships of length, width, thickness, depth, and the like are appropriately changed for the sake of simplification of the drawings, and do not necessarily represent actual dimensional relationships.

[0018] In the present disclosure, the expression of the form "A~B" means the upper limit and the lower limit of the range (i.e., A or more and B or less), and in the case where the unit is not described in A but only described in B, the unit of A is the same as the unit of B.

[0019] In the present disclosure, in the case where a compound or the like is expressed by a chemical formula, all atomic ratios conventionally known are included without particular limitation, and are not necessarily limited only to the stoichiometric range.

[0020] In the present disclosure, in the case where one or more values are described as the lower limit and the upper limit of the numerical range, combinations of any one value described as the lower limit and any one value described as the upper limit are also disclosed. For example, in the case where a1 or more, b1 or more, and c1 or more are described as the lower limit, and a2 or less, b2 or less, and c2 or less are described as the upper limit, a1 or more and a2 or less, a1 or more and b2 or less, a1 or more and c2 or less, b1 or more and a2 or less, b1 or more and b2 or less, b1 or more and c2 or less, c1 or more and a2 or less, c1 or more and b2 or less, and c1 or more and c2 or less are disclosed.

[0021] [Embodiment 1: Cemented Carbide] Use Figure 1 A cemented carbide according to one embodiment of the present disclosure will be described.

[0022] In one embodiment of this disclosure (hereinafter also referred to as "Embodiment 1"), the cemented carbide 3 is a cemented carbide 3 having a plurality of tungsten carbide particles 1 and a bonding phase 2. The cemented carbide 3 contains a total of more than 89% by volume tungsten carbide particles 1 and a bonding phase 2. The cemented carbide 3 contains more than 1.8 vol% and less than 20 vol% of the bonding phase 2. Phase 2 contains more than 80% by mass of cobalt. The cemented carbide 3 includes an internal region at a distance of more than 300 μm from the surface. In the bound phase of the internal region, the area S relative to cobalt with the hcp structure (hcp) And the area S of cobalt with an fcc structure (fcc) The total area S (hcp) percentage {S (hcp) / (S (hcp) +S (fcc) )}×100 is more than 45%.

[0023] The cemented carbide of Embodiment 1 provides a cemented carbide, particularly in the case of materials used in cutting tools for intermittent machining of high-strength materials, that enables long tool life, as well as a cutting tool incorporating the cemented carbide. The reason for this is not yet clear, but it is speculated as follows.

[0024] The cemented carbide of Embodiment 1 has multiple tungsten carbide particles (hereinafter also referred to as "WC particles") and a bonding phase, and the total content of the WC particles and the bonding phase in the cemented carbide is 89% by volume or more. As a result, the cemented carbide has high hardness and strength, and cutting tools made of this cemented carbide can have excellent wear resistance and chipping resistance.

[0025] The cemented carbide of Embodiment 1 contains 1.8% by volume and 20% by volume of a binding phase, wherein the binding phase contains 80% by mass and 80% by mass of cobalt. Therefore, the cemented carbide has high hardness and strength, and cutting tools incorporating this cemented carbide exhibit excellent wear resistance and chip resistance.

[0026] In the bonding phase of the internal region of the cemented carbide in Embodiment 1, relative to the area S of cobalt having an hcp structure (hcp) And the area S of cobalt with an fcc structure (fcc) The total area S (hcp) percentage {S (hcp) / (S (hcp) +S (fcc) The content of )}×100 is over 45%. Therefore, the deformation resistance of the bonded phase is improved, and the deformation resistance of the cemented carbide is also improved.

[0027] <Composition of Cemented Carbide> The cemented carbide of Embodiment 1 contains tungsten carbide particles in total of 89% by volume or more and a binder phase. Thereby, it is possible to increase the hardness of the cemented carbide. The cemented carbide can contain the tungsten carbide particles in total of 89% by volume or more and the binder phase of 100% by volume or less, can contain 90% by volume or more and 100% by volume or less, can contain 91% by volume or more and 100% by volume or less, or can contain 92% by volume or more and 100% by volume or less.

[0028] The cemented carbide of Embodiment 1 contains the binder phase in an amount of 1.8% by volume or more and 20% by volume or less. Thereby, it is possible to increase the hardness and toughness of the cemented carbide. The binder phase of the cemented carbide can be contained in an amount of 2.0% by volume or more and 19.0% by volume or less, can be contained in an amount of 3.0% by volume or more and 18.0% by volume or less, or can be contained in an amount of 4.0% by volume or more and 17.0% by volume or less.

[0029] The cemented carbide of Embodiment 1 can be composed of a plurality of tungsten carbide particles and a binder phase. In this case, the cemented carbide can contain impurities within a range that does not impair the effects of the present disclosure.

[0030] The cemented carbide can contain other phases (not illustrated) in addition to the tungsten carbide particles and the binder phase. As the other phases, a carbide, a nitride, or a carbonitride containing at least one element selected from the group consisting of titanium (Ti), tantalum (Ta), niobium (Nb), zirconium (Zr), hafnium (Hf), and molybdenum (Mo) can be exemplified. The component of the other phases can be, for example, at least one selected from the group consisting of TiCN, TaC, NbC, ZrC, HfC, Cr3C2, and Mo2C.

[0031] The cemented carbide of Embodiment 1 can be composed of tungsten carbide particles, a binder phase, and other phases. In this case, the cemented carbide can contain impurities within a range that does not impair the effects of the present disclosure.

[0032] The content of the other phases of the cemented carbide is allowed within a range that does not impair the effects of the present disclosure. For example, the content of the other phases of the cemented carbide can be 0% by volume or more and 11% by volume or less, can be more than 0% by volume and 11% by volume or less, can be more than 0% by volume and 7% by volume or less, or can be more than 0% by volume and 4% by volume or less.

[0033] The cemented carbide of Embodiment 1 can contain impurities. As the impurities, for example, iron (Fe), calcium (Ca), silicon (Si), and sulfur (S) can be listed. The content of the impurities of the cemented carbide is allowed within a range that does not impair the effects of the present disclosure. For example, the content of the impurities of the cemented carbide can be 0 mass% or more and less than 0.1 mass%. The content of the impurities of the cemented carbide is determined by ICP emission spectroscopy (Inductively Coupled Plasma Emission Spectroscopy). As the measuring device, "ICPS-8100" (trademark) manufactured by Shimadzu Corporation can be used.

[0034] The content of the tungsten carbide particles of the cemented carbide of Embodiment 1 can be 67 vol% or more and 98.2 vol% or less, can be 70 vol% or more and 97 vol% or less, or can also be 75 vol% or more and 96 vol% or less.

[0035] The method for measuring the content of the tungsten carbide particles of the cemented carbide (vol%) and the content of the binder phase of the cemented carbide (vol%) is described below.

[0036] (A1) A cross section of the cemented carbide is exposed by cutting the cemented carbide at an arbitrary position. The cross section is mirror finished using a cross section polisher (manufactured by JEOL Ltd.).

[0037] (B1) The mirror finished surface of the cemented carbide is analyzed using an energy dispersive X-ray spectrometer attached to a scanning electron microscope (SEM-EDX) (device: "Gemini 450" (trademark) manufactured by Carl Zeiss AG) to determine the elements contained in the cemented carbide.

[0038] (C1) The mirror finished surface of the cemented carbide is imaged using a scanning electron microscope (SEM) to obtain a reflected electron image. The imaging area is set at a position in the central portion of the cross section of the cemented carbide, i.e., in the vicinity of the surface of the cemented carbide, and the like, which does not include a portion having a significantly different appearance from the bulk portion (the imaging area is entirely a position of the bulk portion of the cemented carbide). The observation magnification is 5000 times. The measurement conditions are an acceleration voltage of 3 kV, a current value of 2 nA, and a working distance (WD) of 5 mm.

[0039] (D1) The imaging area of (C1) above is analyzed using SEM-EDX to determine the distribution of the elements determined in (B1) above in the imaging area, and an element mapping image is obtained.

[0040] (E1) The reflection electron image obtained in the above (C1) is taken into a computer, and binarization processing is performed using an image analysis software (OpenCV, SciPy). In the image after the binarization processing, the tungsten carbide particles are represented in white, and the binder phase is represented in gray to black. In addition, the threshold value for the binarization changes depending on the contrast, and thus is set for each image.

[0041] (F1) By superimposing the element mapping image obtained in the above (D1) and the image after the binarization processing obtained in the above (E1), the respective existence regions of the tungsten carbide particles and the binder phase are determined on the image after the binarization processing. Specifically, in the image after the binarization processing, the regions in which tungsten (W) and carbon (C) exist in the element mapping image correspond to the existence regions of the tungsten carbide particles. In the image after the binarization processing, the regions in which cobalt (Co) exists in the element mapping image correspond to the existence regions of the binder phase.

[0042] (G1) A rectangular measurement field of 24.9 pm x 18.8 pm is set in the image after the binarization processing. Using the above image analysis software, the area percentages of the tungsten carbide particles and the binder phase are measured with the area of the entire measurement field as the denominator.

[0043] (H1) The measurement of the above (G1) is performed in five different measurement fields that do not overlap with each other. In the present disclosure, the average of the area percentages of the tungsten carbide particles in the five measurement fields corresponds to the content rate (vol%) of the tungsten carbide particles of the cemented carbide, and the average of the area percentages of the binder phase in the five measurement fields corresponds to the content rate (vol%) of the binder phase of the cemented carbide.

[0044] In the case where the cemented carbide contains other phases in addition to the WC particles and the binder phase, the content rate of the other phases of the cemented carbide can be obtained by subtracting the content rate (vol%) of the tungsten carbide particles and the content rate (vol%) of the binder phase, which are measured according to the above steps, from the entire cemented carbide (100 vol%).

[0045] As long as the measurement is performed in the same test sample, it is confirmed that the measurement of the content rate of the tungsten carbide particles and the content rate of the binder phase of the cemented carbide is hardly deviated even if the measurement is performed multiple times, as long as the position at which the cross section of the cemented carbide is taken, the imaging region described in the above (C1), and the measurement field described in the above (G1) are arbitrarily set.

[0046] The cemented carbide of the embodiment 1 can also contain cobalt of 1 mass% or more. The content rate of cobalt of the cemented carbide can be 1.0 mass% or more and 20 mass% or less, can be 2.0 mass% or more and 15 mass% or less, or can be 3.0 mass% or more and 12 mass% or less.

[0047] The cobalt content of the cemented carbide is measured as follows. Using the same method as (A1) to (D1) of the measurement method of the tungsten carbide particle content and the binder phase content of the cemented carbide described above, analysis is performed using SEM-EDX to obtain an elemental mapping image. Based on the elemental mapping image, the cobalt region in the cemented carbide is determined, and the cobalt content is measured. This measurement is performed in five different photographing regions that do not overlap with each other. In the present disclosure, the average of the cobalt contents in the five photographing regions corresponds to the cobalt content of the cemented carbide.

[0048] As long as the measurement is performed in the same test sample, it is confirmed that the measurement of the cobalt content of the cemented carbide is hardly deviated even if the measurement is performed multiple times, as long as the cutting position of the cross section of the cemented carbide and the photographing region described in (C1) above are arbitrarily set according to the above procedure.

[0049] < tungsten carbide particle > In the cemented carbide of Embodiment 1, the tungsten carbide particle is at least one of “pure WC particles (including WC in which no impurity element is contained at all, and WC in which the content of the impurity element is less than the detection limit)” and “WC particles in which an impurity element is intentionally or unavoidably contained in the inside thereof within a range that does not impair the effects of the present disclosure.” The content of the impurity of the tungsten carbide particle (the total concentration of the elements constituting the impurity in the case where the elements constituting the impurity are two or more) is preferably less than 0.1% by mass. The content of the impurity element of the tungsten carbide particle is measured by ICP emission analysis.

[0050] In Embodiment 1, the average particle diameter of the tungsten carbide particle is not particularly limited. The average particle diameter of the tungsten carbide particle can be set to, for example, 0.1 μm or more and 3.5 μm or less. It is confirmed that the cemented carbide of Embodiment 1 can achieve long tool life when used as a material for cutting tools, regardless of the average particle diameter of the tungsten carbide particle.

[0051] < binder phase > In the cemented carbide of Embodiment 1, the binder phase contains 80% by mass or more of cobalt. Thereby, the cemented carbide can have excellent toughness. The cobalt content of the binder phase can be 80% by mass or more and 100% by mass or less, can be 80% by mass or more and less than 100% by mass, or can be 90% by mass or more and less than 100% by mass.

[0052] The method for measuring the cobalt content of the binder phase is described below. The element mapping image and the image after the binarization process are obtained by the same method as (A1) to (E1) of the method for measuring the tungsten carbide particle content and the binder phase content of the cemented carbide described above. The presence area of the binder phase is determined in the element mapping image by superimposing the element mapping image and the image after the binarization process. One measurement field of 24.9 μm x 18.8 μm is set in the image of the element mapping image. The cobalt content is measured in the presence area of the binder phase in the measurement field. The measurement described above is performed in five different measurement fields that do not overlap with each other. In the present disclosure, the average of the cobalt content in the presence area of the binder phase in the five measurement fields corresponds to the cobalt content of the binder phase.

[0053] As long as the measurement is performed in the same sample, it is confirmed that the measurement of the cobalt content of the binder phase is hardly deviated even if the measurement is performed several times, by arbitrarily setting the cutting position of the cross section of the cemented carbide, the photographing area described in (C1) above, and the measurement field, according to the steps described above.

[0054] In the cemented carbide of Embodiment 1, the binder phase can further contain at least one first element selected from the group consisting of silicon, phosphorus, germanium, tin, rhenium, ruthenium, osmium, iridium, and platinum. Thereby, the deformation resistance of the binder phase is improved.

[0055] The case where the binder phase contains the first element is confirmed by the following steps. The element mapping image and the image after the binarization process are obtained by the same method as (A1) to (E1) of the method for measuring the tungsten carbide particle content and the binder phase content of the cemented carbide described above. The presence area of the binder phase is determined in the element mapping image by superimposing the element mapping image and the image after the binarization process. In the element mapping, in the case where the first element is present in the presence area of the binder phase, it is confirmed that the binder phase contains the first element.

[0056] In the binder phase of the cemented carbide of Embodiment 1, the percentage of the mass M1 of the first element with respect to the total M1+M2 of the mass M1 of the first element and the mass M2 of cobalt {M1 / (M1+M2)}x 100 can be 1% or more and 6% or less. Here, the units of M1 and M2 are the same. Thereby, the binder phase can have both more excellent hardness and more excellent toughness, and thus a cutting tool having the cemented carbide containing the binder phase can have a longer tool life. Here, in the case where the binder phase contains two or more kinds of first elements, the mass M1 of the first element refers to the total mass of all kinds of first elements. The percentage {M1 / (M1+M2)}x 100 can be 2% or more and 5% or less, or 3% or more and 4% or less.

[0057] The method for determining the percentage {M1 / (M1+M2)}×100 is as follows. Using the same method (A1) to (E1) as the method for determining the content of tungsten carbide particles and the content of the bound phase in the aforementioned cemented carbide, an elemental mapping image and a binarized image are obtained. The region where the bound phase exists is determined in the elemental mapping image by superimposing the elemental mapping image and the binarized image. A measurement field of view of a rectangle of 24.9 μm × 18.8 μm is set in the elemental mapping image. In the region where the bound phase exists in the measurement field of view, the percentage of the mass m1 of the first element relative to the total m1+m2 of the mass m1 of the first element and the mass m2 of cobalt is calculated as {m1 / (m1+m2)}×100. The above determination is performed in five different, non-overlapping measurement fields. In this disclosure, the average of the percentages {m1 / (m1+m2)}×100 in the five measurement fields corresponds to the percentages {M1 / (M1+M2)}×100 in the bonding phase of the cemented carbide.

[0058] As long as the measurement is performed on the same sample, the section of the cemented carbide can be arbitrarily set, the shooting area described in (C1) above, and the measurement field of view described above. Following the above steps, even if multiple percentage measurements of {M1 / (M1+M2)}×100 are performed, there is almost no deviation in the measurement results.

[0059] In the cemented carbide of Embodiment 1, the bonding phase, in addition to cobalt and the first element, may also contain at least one second element selected from the group consisting of iron, nickel, and chromium. This bonding phase may consist of cobalt, the first element, and the second element. This bonding phase may also consist of cobalt, the first element, the second element, and unavoidable impurities. Examples of unavoidable impurities include, for instance, iron, nickel, and sulfur.

[0060] Percentage of bound phase in the internal region {S (hcp) / (S (hcp) +S (fcc) )}×100> The cemented carbide of Embodiment 1 includes an internal region at a distance of 300 μm or more from the surface, wherein the area S of the bonding phase in the internal region relative to cobalt having an hcp (hexagonal densest) structure. (hcp) And the area S of cobalt with an fcc (face-centered cubic) structure (fcc) The total area S (hcp) percentage {S (hcp) / (S (hcp) +S (fcc) The percentage {S} × 100 is above 45%. (hcp) / (S (hcp) +S (fcc)The percentage {S (S + S )} x 100 can be 45% or more and 80% or less, or can be 50% or more and 70% or less.

[0061] In the present disclosure, the percentage {S (S + S )} x 100 in the binder phase of the inner region of the cemented carbide is determined in the following steps. (hcp) (hcp) (fcc) The percentage {S (S + S )} x 100 is determined in the following steps.

[0062] (A2) The cemented carbide is cut along the normal line of the main face to expose the cross section. In the case where the surface of the cemented carbide does not have a planar region, the cemented carbide is cut from an arbitrary point on the surface in the direction toward the center of gravity of the cemented carbide to expose the cross section. The cross section is mirror finished using a cross section polisher (manufactured by Nakanishi Electronic Corporation).

[0063] (B2) The mirror finished surface of the cemented carbide is observed using a scanning electron microscope (SEM device: "Gemini 450" (trademark) manufactured by Carl Zeiss Corporation) equipped with an electron backscatter diffraction device (EBSD (Electron Backscatter Diffraction Pattern) device: "Symmetry" (trademark) manufactured by Oxford Corporation). The obtained observation image is subjected to EBSD analysis. The observation image is acquired in such a manner that an inner region having a distance of 300 μm or more from the surface of the cemented carbide is included. A rectangular measurement field of 11.5 μm x 8.5 μm is set in the inner region of the observation image. The observation magnification is 10,000 times. The measurement conditions are set to an acceleration voltage of 15 kV, a current value of 20 nA, 0.02 μm / step, an exposure time of 1.5 ms ~ 3 ms, and a measurement time of 10 minutes ~ 20 minutes.

[0064] (C2) The above EBSD analysis result is analyzed using a commercially available software ("AZtec Crystal" (trademark) manufactured by Oxford Corporation), and the crystal structure of cobalt contained in the binder phase is determined in the above measurement field to obtain a color map. The crystal structure of cobalt determined here is a crystal structure observed when the mirror finished surface of the cemented carbide is viewed from the normal line direction of the mirror finished surface.

[0065] (D2) The above software is used to determine the percentage {S (S + S )} x 100 of the area S (hcp) of the cobalt having an fcc structure in the binder phase of the measurement field. (fcc) (hcp) (hcp) (hcp) (fcc) ​​​​​​is determined. For example, based on a color image, an image A in which tungsten carbide particles are represented in white and cobalt having an hcp structure is represented in black, and an image B in which tungsten carbide particles are represented in white and cobalt having an fcc structure is represented in black, can be output, and based on the image A and the image B, the percentage {S (hcp) / (S (hcp) +S (fcc) ) x 100 is determined.

[0066] The percentage {S (hcp) / (S (hcp) +S (fcc) ) x 100 described above is determined in three different measurement fields that do not overlap with each other. In the present disclosure, the average of the percentages {S (hcp) / (S (hcp) +S (fcc) ) x 100 in the three measurement fields corresponds to the percentage {S (hcp) / (S (hcp) +S (fcc) ) x 100 in the binding phase of the internal region of the cemented carbide.

[0067] As long as the measurement is performed in the same sample, the measurement site of the cross section of the cemented carbide, the acquisition region of the observation image described in (B2) above, and the measurement field are arbitrarily set, and the percentage {S (hcp) / (S (hcp) +S (fcc) ) x 100 in the binding phase of the internal region of the cemented carbide is measured according to the above-described procedure, and even if the measurement is performed a plurality of times, there is almost no deviation in the measurement results.

[0068] The cemented carbide of Embodiment 1 can include a surface region having a distance from the surface of less than 300 μm. The percentage {S (hcp) / (S (hcp) +S (fcc) ) x 100 in the binding phase of the surface region of the cemented carbide of Embodiment 1 is not particularly limited. The reason for this is that the surface region of the cemented carbide is affected by stress at the time of grinding when a cutting tool composed of the cemented carbide is shaped by grinding, and thus is not an essential part of the cemented carbide that directly affects the life of the cutting tool. On the other hand, the internal region having a distance from the surface of the cemented carbide of 300 μm or more is not easily affected by stress when a cutting tool is formed by grinding, and thus is an essential part of the cemented carbide that affects the life of the cutting tool. Therefore, in the cemented carbide of the present disclosure, the percentage {S (hcp) / (S (hcp) +S (fcc)) x 100. The percentage {S (hcp) / (S (hcp) +S (fcc) ) x 100 can be less than 45%, for example.

[0069] <Method for manufacturing cemented carbide> The cemented carbide of Embodiment 1 can be manufactured by sequentially performing a raw material powder preparation step, a mixing step, a molding step, and a sintering step. Hereinafter, each step will be described.

[0070] <Preparation step> The preparation step is a step of preparing raw material powders of the cemented carbide. As the raw material powders, for example, tungsten carbide powder (hereinafter also referred to as "WC powder"), cobalt (Co) powder, first element powder, and alloy powder of the first element and cobalt can be listed. As the first element powder, silicon (Si) powder, phosphorus (P) powder, germanium (Ge) powder, tin (Sn) powder, rhenium (Re) powder, ruthenium (Ru) powder, osmium (Os) powder, iridium (Ir) powder, and platinum (Pt) powder can be listed. As the raw material powders, nickel (Ni) powder, niobium carbide (NbC) powder, tantalum carbide (TaC) powder, titanium carbonitride (TiCN) powder, chromium carbide (Cr3C2) powder, and the like can also be prepared. These raw material powders can use commercially available products. The average particle diameter of these raw material powders is not particularly limited, and can be set to 0.5 μm to 2 μm, for example. The average particle diameter of the raw material powders refers to the average particle diameter measured by the FSSS (Fisher Sub-Sieve Sizer) method. This average particle diameter is measured using "Sub-Sieve Sizer Model 95" (trademark) manufactured by Fisher Scientific.

[0071] <Mixing step> The mixing step is a step of mixing each of the raw material powders prepared in the preparation step at a predetermined ratio. Through the mixing step, a mixed powder in which each of the raw material powders is mixed is obtained. The mixing ratio of each of the raw material powders is appropriately adjusted according to the composition of the target cemented carbide.

[0072] The mixing of each of the raw material powders can use a publicly known mixing method such as a mortar, a ball mill, and a bead mill. The mixing conditions can also use publicly known conditions. The mixing time can be set to 2 hours or more and 20 hours or less, for example.

[0073] After the mixing step, the mixed powder can be granulated as needed. By granulating the mixed powder, it is easy to fill the mixed powder into a mold or a die at the molding step described later. The granulation can apply a publicly known granulation method, and a commercially available granulator such as a spray dryer can be used, for example.

[0074] <shaping step> The shaping step is a step of shaping the mixed powder obtained in the mixing step into a shape for a cutting tool to obtain a shaped body. The shaping method and the shaping conditions in the shaping step are not particularly limited as long as a general method and conditions are adopted.

[0075] <annealing step> The annealing step is a step of annealing the shaped body obtained in the shaping step to obtain a cemented carbide intermediate. Specifically, the shaped body is held at 7 MPa and 1360°C for 2 hours.

[0076] <cooling step> The cooling step is a step of cooling the cemented carbide intermediate after the annealing step. Specifically, the cemented carbide intermediate is cooled to 1200°C in a vacuum, and held for 30 minutes. Next, the cemented carbide intermediate is slowly cooled to 1000°C at a temperature decrease rate of -0.5°C / minute in a vacuum. Next, the cemented carbide intermediate is rapidly cooled to room temperature (23°C) at a temperature decrease rate of -20°C / minute in a vacuum to obtain the cemented carbide of Embodiment 1.

[0077] <Features of the method for manufacturing the cemented carbide of Embodiment 1> In the method for manufacturing the cemented carbide of Embodiment 1, the annealing step is performed by holding the cemented carbide intermediate at 7 MPa and 1360°C for 2 hours. In the cooling step, the cemented carbide intermediate is cooled to 1200°C in a vacuum, and held for 30 minutes, next, the cemented carbide intermediate is slowly cooled to 1000°C at a temperature decrease rate of -0.5°C / minute in a vacuum, next, the cemented carbide intermediate is rapidly cooled to room temperature (23°C) at a temperature decrease rate of -20°C / minute in a vacuum. By these conditions, the cemented carbide of Embodiment 1 in which the percentage of {S (hcp) / (S (hcp) +S (fcc)} x 100 in the binding phase in the inner region of the cemented carbide is 45% or more can be manufactured. The present inventors have conducted intensive studies, and as a result, it has been found that by adopting such an annealing step and a cooling step, the cemented carbide of the present disclosure can be achieved.

[0078] [Embodiment 2: Cutting tool] One embodiment of the present disclosure (hereinafter also referred to as “Embodiment 2”) is a cutting tool including a cutting edge composed of the cemented carbide of Embodiment 1. In the present disclosure, the cutting edge refers to a portion that participates in cutting. More specifically, the cutting edge refers to a region surrounded by a virtual face of 0.5 mm or 2 mm from a cutting edge ridge line to the cemented carbide side.

[0079] As the cutting tool, for example, a cutting tool, a drill, an end mill, an indexable cutting insert for milling, an indexable cutting insert for turning, a bench saw, a gear cutting tool, a reamer, or a tap can be exemplified. As shown in Figure 2 The cutting tool 10 of Embodiment 2 can exert an excellent effect, particularly in the case of an end mill. Figure 2 The cutting edge 11 of the cutting tool 10 shown is composed of the cemented carbide of Embodiment 1.

[0080] In the cutting tool of Embodiment 2, the cemented carbide of Embodiment 1 can compose the entirety of the tool or a part thereof. Here, "compose a part thereof" indicates a manner of brazing the cemented carbide of Embodiment 1 at a predetermined position of an arbitrary base material to form a cutting edge portion, or the like.

[0081] The cutting tool of Embodiment 2 can further be provided with a hard film that covers at least a part of the surface of the base material composed of the cemented carbide. As the hard film, for example, diamond-like carbon or diamond can be used.

[0082] The cutting tool of Embodiment 2 can be obtained by shaping the cemented carbide of Embodiment 1 into a desired shape.

[0083] Examples The present embodiment will be further specifically described by way of examples. However, the present embodiment is not limited to these examples.

[0084] [Production of Cemented Carbide] The cemented carbide of each sample was produced in accordance with the following steps.

[0085] <Preparation Step> As the raw material powder, WC powder (average particle diameter: 1 μm), Co powder (average particle diameter: 1 μm), first element powder, TiCN powder (average particle diameter: 1 μm), Cr3C2 powder (average particle diameter: 1 μm), and Ni powder (average particle diameter: 1 μm) were prepared. As the first element powder, silicon (Si) powder (average particle diameter: 1 μm), phosphorus (P) powder (average particle diameter: 1 μm), germanium (Ge) powder (average particle diameter: 1 μm), tin (Sn) powder (average particle diameter: 1 μm), rhenium (Re) powder (average particle diameter: 1 μm), ruthenium (Ru) powder (average particle diameter: 1 μm), osmium (Os) powder (average particle diameter: 1 μm), iridium (Ir) powder (average particle diameter: 1 μm), and platinum (Pt) powder (average particle diameter: 1 μm) were prepared.

[0086] <Mixing Step> Each of the raw material powders was mixed for 10 hours using a mortar in the proportions described in Table 1, thereby obtaining a mixed powder. The proportions (mass %) of each of the raw material powders described in Table 1 are proportions when the entire mixed powder is taken as 100 mass %.

[0087] [Table 1]

[0088] <Shaping Step> A shaped body in the shape of a round bar was obtained by subjecting the mixed powder to pressing.

[0089] <Sintering Step> The shaped body was held at the pressure described in the "Pressure to be held" column and the temperature described in the "Temperature to be held" column of Table 2 for the time described in the "Holding time" column. Thereby, a cemented carbide intermediate was obtained.

[0090] <Cooling Step> Test samples 1 to 16 and test samples 101 to 105 were cooled by the following procedure to obtain a cemented carbide from the cemented carbide intermediate after the sintering step. The cemented carbide intermediate was cooled in a vacuum to 1200°C (described in the "First cooling temperature" column of Table 2) and held for 30 minutes (described in the "First holding time" column of Table 2). Next, the cemented carbide intermediate was slowly cooled in a vacuum to 1000°C at a temperature decrease rate of -0.5°C / minute (described in the "~1000°C temperature decrease rate" column of Table 2). Next, the cemented carbide intermediate was quenched in a vacuum to room temperature (23°C) at a temperature decrease rate of -20°C / minute (described in the "~23°C temperature decrease rate" column of Table 2), thereby obtaining a cemented carbide of each test sample.

[0091] Test samples 106 and 107 were quenched in a vacuum to room temperature (23°C) at a temperature decrease rate of -20°C / minute (described in the "~23°C temperature decrease rate" column of Table 2) from the cemented carbide intermediate after the sintering step, thereby obtaining a cemented carbide of each test sample.

[0092] [Table 2]

[0093] [Assessment of Cemented Carbide] <Volume % of Tungsten Carbide Particles and Volume % of Binder Phase in Cemented Carbide> The content ratio (vol%) of tungsten carbide particles and the content ratio (vol%) of the binder phase of each of the cemented carbides were measured. The measurement method was as described in Embodiment 1. The results are shown in the "WC particle content ratio" and the "binder phase content ratio" columns of "Cemented carbide" in Table 3. Further, the total of the content ratio of tungsten carbide particles and the content ratio of the binder phase of the cemented carbide is shown in the "WC particle + binder phase content ratio" column of "Cemented carbide" in Table 3. In Table 3, it was confirmed that the cemented carbide in which the "WC particle + binder phase content ratio" column was lower than 100 vol% further contained TiCN or Cr3C2.

[0094] [Table 3]

[0095] <Co content ratio of the binder phase> The cobalt content ratio of the binder phase in each of the cemented carbides was measured. The measurement method was as described in Embodiment 1. The results are shown in the "Co content ratio" column of "Binder phase" in Table 4.

[0096] <Kind of the first element and {M1 / (M1+M2)}x100> In the binder phase of each of the cemented carbides, the kind of the first element, and the percentage of the mass M1 of the first element with respect to the total M1+M2 of the mass M1 of the first element and the mass M2 of cobalt, {M1 / (M1+M2)}x100, was measured. The measurement method was as described in Embodiment 1. The results are shown in the "first element" column and the "{M1 / (M1+M2)}x100" column of "Binder phase" in Table 4. The sample in which "-" is written in the "first element" column indicates that the sample does not contain the first element.

[0097] <{S (hcp) / (S (hcp) +S (fcc) )}x100> In the binder phase in the internal region at a distance of 300 μm or more from the surface of each of the cemented carbides, the percentage {S (hcp) / (S (fcc) +S (hcp) )}x100 of the area S (hcp) with respect to the total of the area S (hcp) of cobalt having an hcp structure and the area S (fcc) of cobalt having an fcc structure was measured. The measurement method was as described in Embodiment 1. The results are shown in the "{S (hcp) / (S (hcp) +S (fcc) )}x100" column of "Binder phase" in Table 4.

[0098] [Cutting test] A round bar composed of the cemented carbide of each sample was processed to produce a round nose end mill with a blade diameter of φ 6 mm. Using the round nose end mill, intermittent machining of the side surface of Inconel 718 aged material (having holes of φ 2 mm opened at equal intervals) was performed. The machining conditions were set to a cutting speed Vc of 30 m / min, a single blade feed fz of 0.1 mm / blade, a cut-in amount (axial direction) ap of 3.0 mm, a cut-in amount (radial direction) ae of 1.0 mm, and wet. The cutting length until the occurrence of tool tip chipping was measured. The longer the cutting length, the longer the tool life. The results are shown in the "cutting length" column of the "cutting test" of Table 4. In addition, the above machining conditions correspond to intermittent machining of high-strength materials.

[0099] [Table 4]

[0100] [Investigation] The cemented carbide and cutting tool of Samples 1 to 16 correspond to the embodiments. The cemented carbide and cutting tool of Samples 101 to 107 correspond to the comparative examples. It was confirmed that the tool life of the cutting tool of Samples 1 to 16 was longer than that of the cutting tool of Samples 101 to 107.

[0101] The embodiments and examples of the present disclosure have been described as above, but it is also intended to appropriately combine the structures of each of the above embodiments and examples, or to make various modifications.

[0102] It should be considered that the embodiments and examples of the present disclosure are illustrative in all respects and are not restrictive. The scope of the present invention is not shown by the above embodiments and examples but by the claims, and is intended to include the meaning equivalent to the claims and all modifications within the scope.

[0103] Explanation of Reference Signs 1: tungsten carbide particle; 2: binder phase; 3: cemented carbide; 10: cutting tool; 11: tool tip.

Claims

1. A cemented carbide comprising multiple tungsten carbide particles and a bonding phase, 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 vol% or less of the bonding phase. The bonding phase contains more than 80% by mass of cobalt. The cemented carbide includes an internal region at a distance of more than 300 μm from the surface. In the bound phase of the internal region, the area S relative to cobalt having an hcp structure (hcp) and the area S of cobalt with an fcc structure (fcc) The total area S (hcp) percentage {S (hcp) / (S (hcp) +S (fcc) )}×100 is over 45%.

2. The cemented carbide according to claim 1, wherein, The percentage {S (hcp) / (S (hcp) +S (fcc) )}×100 is between 50% and 70%.

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

4. The cemented carbide according to claim 3, wherein, In the combined phase, the percentage of the mass M1 of the first element relative to the total mass M1 of the first element and the mass M2 of cobalt, M1+M2, is 1% or more and 6% or less.

5. A cutting tool having a cutting tip made of cemented carbide as described in any one of claims 1 to 4.

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