Tungsten carbide powder and tungsten carbide mixed powder

Abstract

The purpose of the present disclosure is to provide a tungsten carbide powder and a tungsten carbide mixed powder, each of which makes it possible for a cutting tool that is provided with a cemented carbide to have a long tool life if the tungsten carbide powder or the tungsten carbide mixed powder is used as a starting material for the cemented carbide.　The present disclosure relates to a tungsten carbide powder which is composed of first tungsten carbide particles each having an oxide of a first element on the surface thereof, wherein the first element is at least one element that is selected from the group consisting of titanium, zirconium, niobium, tantalum, molybdenum, cerium, and yttrium. In a first graph which shows the result, obtained by performing a line analysis using an energy dispersive X-ray spectrometer attached to a transmission electron microscope from a position X1 located inside the first tungsten carbide particles and having a distance from the outer edges of the first tungsten carbide particles of 10 nm or more toward a position X2 located outside the first tungsten carbide particles and having a distance from the outer edges of the first tungsten carbide particles of 10 nm or more, in a coordinate system in which the X-axis shows the distance from the position X1 and the Y-axis shows the content based on the number of atoms of an element, a distance P2 at which the content based on the number of atoms of the first element is maximum and a distance P3 at which the content based on the number of atoms of oxygen is maximum are present at distances farther from the origin than a distance P1 at which the content based on the number of atoms of tungsten is 0.5 times the maximum value of the content based on the number of atoms of tungsten, and the absolute value of the difference between the distance P2 and the distance P3 is 0 nm to 0.5 nm inclusive.

Description

Tungsten carbide powder and tungsten carbide mixed powder

[0001] This disclosure relates to tungsten carbide powder and tungsten carbide mixed powder.

[0002] Conventionally, cemented carbide alloys obtained by firing a mixed powder of tungsten carbide powder and cobalt powder have been used as materials for cutting tools (Patent Document 1).

[0003] International Publication No. 2024 / 005017

[0004] The tungsten carbide powder of this disclosure is a tungsten carbide powder comprising first tungsten carbide particles having an oxide of a first element on its surface, wherein the first element is at least one selected from the group consisting of titanium, zirconium, niobium, tantalum, molybdenum, cerium, and yttrium, and is subjected to a transmission electron microscope from a position X1 located inside the first tungsten carbide particle and at a distance of 10 nm or more from the outer edge of the first tungsten carbide particle toward a position X2 located outside the first tungsten carbide particle and at a distance of 10 nm or more from the outer edge of the first tungsten carbide particle. The first graph, which shows the results obtained by line analysis using the attached energy-dispersive X-ray spectrometer in a coordinate system where the X axis is the distance from position X1 and the Y axis is the content of elements based on the number of atoms, is a tungsten carbide powder in which the distance P2 where the content of the first element based on the number of atoms is maximum and the distance P3 where the content of oxygen based on the number of atoms is maximum exist at a distance P1 where the content of tungsten based on the number of atoms is 0.5 times the maximum value of the content of tungsten based on the number of atoms, and the absolute value of the difference between distance P2 and distance P3 is 0 nm or more and 0.5 nm or less.

[0005] Figure 1 is an example of a first graph obtained by performing line analysis on the first tungsten carbide particles of Embodiment 1.

[0006] [Problems this disclosure aims to solve] In recent years, the difficulty of machining workpieces has increased, and the operating conditions for cutting tools have become more severe. For this reason, there is a need for cutting tools with long tool life even when machining difficult-to-machine materials.

[0007] Therefore, the present disclosure aims to provide tungsten carbide powder and tungsten carbide mixed powder that, when used as raw materials for cemented carbide, enable cutting tools made of cemented carbide to have a long tool life.

[0008] [Effects of this disclosure] According to this disclosure, it is possible to provide tungsten carbide powder and tungsten carbide mixed powder that, when used as a raw material for cemented carbide, enable cutting tools made of cemented carbide to have a long tool life.

[0009] [Description of Embodiments of the Disclosure] First, embodiments of the Disclosure will be listed and described. (1) The tungsten carbide powder of the Disclosure is a tungsten carbide powder comprising first tungsten carbide particles having an oxide of a first element on its surface, wherein the first element is at least one selected from the group consisting of titanium, zirconium, niobium, tantalum, molybdenum, cerium, and yttrium, and a transmission electron microscope is provided from a position X1 located inside the first tungsten carbide particle and at a distance of 10 nm or more from the outer edge of the first tungsten carbide particle toward a position X2 located outside the first tungsten carbide particle and at a distance of 10 nm or more from the outer edge of the first tungsten carbide particle. In a first graph showing the results obtained by line analysis using an energy-dispersive X-ray spectrometer attached to a mirror, in a coordinate system where the X axis is the distance from position X1 and the Y axis is the content of elements based on the number of atoms, the tungsten carbide powder is such that the distance P2 where the content of the first element based on the number of atoms is maximum and the distance P3 where the content of oxygen based on the number of atoms is maximum exist at a distance P1 where the content of tungsten based on the number of atoms is 0.5 times the maximum value of the content of tungsten based on the number of atoms, and the absolute value of the difference between distance P2 and distance P3 is 0 nm or more and 0.5 nm or less.

[0010] According to this disclosure, it is possible to provide tungsten carbide powder that, when used as a raw material for cemented carbide, enables cutting tools made of the cemented carbide to have a long tool life. The reason for this is presumed to be as follows.

[0011] In the first graph of the first tungsten carbide particles of the tungsten carbide powder of this disclosure, there are distances P2 where the content of the first element is maximum and distances P3 where the content of oxygen is maximum, at distances further from the origin than distance P1 where the tungsten content is 0.5 times the maximum tungsten content. This indicates that the first element and oxygen are present on the surface of the first tungsten carbide particles.

[0012] Furthermore, in the first graph, the absolute difference between the distance P2 at the maximum atomic-number-based content of the first element and the distance P3 at the maximum atomic-number-based content of oxygen is between 0 nm and 0.5 nm. This indicates that on the surface of the first tungsten carbide particles, the first element and oxygen form an oxide of the first element.

[0013] The presence of an oxide of the first element on the surface of the first tungsten carbide particles improves the oxidation resistance of the first tungsten carbide particles. Furthermore, decarburization of the first tungsten carbide particles is suppressed, and the decrease in strength of the first tungsten carbide particles is suppressed. As a result, the oxidation resistance and strength of cemented carbide made using the tungsten carbide powder of this disclosure are improved. Moreover, the resistance to welding of the cemented carbide is also improved. Therefore, cutting tools equipped with cemented carbide made from the tungsten carbide powder of this disclosure have improved oxidation resistance, resistance to welding, and strength, and can have a long tool life even when machining difficult-to-cut materials.

[0014] (2) In (1) above, the content of the first element in the tungsten carbide powder may be 0.01% by mass or more and 2% by mass or less. If the content of the first element in the tungsten carbide powder is 0.01% by mass or more, the oxidation resistance, welding resistance, and strength of the cemented carbide made using the tungsten carbide powder as a raw material are further improved. If the content of the first element in the tungsten carbide powder is 2% by mass or less, the cemented carbide has excellent oxidation resistance, welding resistance, and strength, and the decrease in alloy strength due to the precipitation of the first element in the cemented carbide is suppressed.

[0015] (3) In (1) or (2) above, the oxygen content of the tungsten carbide powder may be 0.1% by mass or more and 3% by mass or less. If the oxygen content of the tungsten carbide powder is 0.1% by mass or more, the oxidation resistance, welding resistance, and strength of the cemented carbide made from the tungsten carbide powder as a raw material are further improved. If the oxygen content of the tungsten carbide powder is 3% by mass or less, the cemented carbide has excellent oxidation resistance, welding resistance, and strength, and the deterioration of alloy properties due to pore formation of the cemented carbide is suppressed.

[0016] (4) In any of (1) to (3) above, the ratio D10 / D90 of the 10% cumulative particle size D10 to the 90% cumulative particle size D90 based on the number of first tungsten carbide particles may be 0.05 or more and 0.7 or less.

[0017] When the D10 / D90 ratio is 0.05 or higher, the balance between fine primary tungsten carbide particles and coarse primary tungsten carbide particles in the tungsten carbide powder is good, resulting in a dense cemented carbide structure. When the D10 / D90 ratio is 0.7 or lower, the particle size of the cemented carbide produced using the tungsten carbide powder as a raw material becomes more uniform, improving the flexural strength of the cemented carbide.

[0018] (5) In any of (1) to (4) above, the 50% cumulative particle size D50 based on the number of first tungsten carbide particles may be 0.2 μm or more and 3.0 μm or less. When D50 is 0.2 μm or more, the cemented carbide made from the tungsten carbide powder tends to have toughness suitable for cutting tools. When D50 is 3.0 μm or less, the cemented carbide tends to have hardness suitable for cutting tools.

[0019] (6) The tungsten carbide mixed powder of the present disclosure is a tungsten carbide mixed powder comprising two or more types of tungsten carbide particles, wherein at least one of the two or more types of tungsten carbide particles is the first tungsten carbide particle described in any of (1) to (5) above.

[0020] For the same reasons as in (1) above, the present disclosure makes it possible to provide a tungsten carbide mixed powder that, when used as a raw material for a cemented carbide, enables cutting tools comprising the cemented carbide to have a long tool life.

[0021] (7) In (6) above, the tungsten carbide mixed powder may contain 20% by mass or more of the first tungsten carbide particles. This further improves the tool life of a cutting tool made of cemented carbide manufactured using the tungsten carbide mixed powder as a raw material.

[0022] [Details of Embodiments of the Disclosure] Specific examples of the tungsten carbide powder and tungsten carbide mixed powder of the Disclosure will be described below with reference to the drawings. In the drawings of the Disclosure, the same reference numerals indicate the same or corresponding parts. In addition, dimensional relationships such as length, width, thickness, and depth have been appropriately modified for clarity and simplification of the drawings and do not necessarily represent actual dimensional relationships.

[0023] In this disclosure, the notation "A to B" means A or greater and B or less. If no unit is specified for A, and only a unit is specified for B, then the unit for A and the unit for B are the same.

[0024] In this disclosure, when compounds and the like are represented by chemical formulas, unless otherwise specified, the atomic ratios should include all conventionally known atomic ratios and should not necessarily be limited to those within the stoichiometric range.

[0025] In this disclosure, if one or more numerical values ​​are listed as the lower limit and upper limit of a numerical range, any combination of any one numerical value listed as the lower limit and any one numerical value listed as the upper limit shall also be disclosed.

[0026] In this disclosure, “equipment,” “includes,” “possesses,” and variations thereof are open-ended terms. Open-ended terms may or may not include additional elements in addition to the essential elements. The statement “consists of” is a closed term. However, even a configuration expressed in closed terms may include additional elements that are usually incidental or irrelevant to the subject technology.

[0027] [Embodiment 1: Tungsten Carbide Powder] The tungsten carbide powder according to one embodiment of the present disclosure (hereinafter also referred to as "Embodiment 1") is a tungsten carbide powder comprising first tungsten carbide particles having an oxide of a first element on its surface, wherein the first element is at least one selected from the group consisting of titanium, zirconium, niobium, tantalum, molybdenum, cerium, and yttrium, and is provided from position X1 located inside the first tungsten carbide particles and at a distance of 10 nm or more from the outer edge of the first tungsten carbide particles to position X located outside the first tungsten carbide particles and at a distance of 10 nm or more from the outer edge of the first tungsten carbide particles The first graph, which shows the results obtained by line analysis using an energy-dispersive X-ray spectrometer attached to a transmission electron microscope, with the X axis representing the distance from position X1 and the Y axis representing the content of elements based on the number of atoms, shows that the tungsten content based on the number of atoms is greater from the origin than distance P1, where the tungsten content based on the number of atoms is 0.5 times the maximum value of the tungsten content based on the number of atoms. At this distance, there are distances P2 where the content of the first element based on the number of atoms is maximum, and distances P3 where the oxygen content based on the number of atoms is maximum. The absolute value of the difference between distances P2 and P3 is between 0 nm and 0.5 nm. This is tungsten carbide powder.

[0028] The tungsten carbide powder of Embodiment 1 consists of primary tungsten carbide particles having an oxide of a primary element on its surface. The tungsten carbide powder of Embodiment 1 may consist of one primary tungsten carbide particle or a plurality of primary tungsten carbide particles. The tungsten carbide powder of Embodiment 1 may contain unavoidable impurities as long as the effects of this disclosure are not impaired. Examples of unavoidable impurities include Al, Ca, Cr, V, Cu, Fe, Mg, Mn, Mo, Ni, Si, Sn, etc.

[0029] <First Tungsten Carbide Particles> <First Graph> First tungsten carbide particles are tungsten particles on which an oxide of the first element is present on the surface. The first element is at least one selected from the group consisting of titanium, zirconium, niobium, tantalum, molybdenum, cerium, and yttrium.

[0030] In the above first graph, at a distance farther from the origin than the distance P1 where the content ratio based on the number of tungsten atoms (hereinafter also referred to as the "content ratio") is 0.5 times the maximum value of the tungsten content ratio, there are a distance P2 where the content ratio based on the number of atoms of the first element is the maximum and a distance P3 where the content ratio based on the number of oxygen atoms is the maximum, and the absolute value of the difference between the distance P2 and the distance P3 is 0 nm or more and 0.5 nm or less, which indicates that an oxide of the first element is present on the surface of the tungsten carbide particles.

[0031] In the present disclosure, the first graph is created by the following procedure. The tungsten carbide powder is embedded in a resin, and using an argon ion slicer ("Cryo Ion Slicer IB-09060BCIS" (trademark) manufactured by JEOL Ltd.), a measurement sample is prepared by slicing it into a thickness of 30 to 100 nm under the conditions of an acceleration voltage of 6 kV and a finish voltage of 2 kV. As the resin, a general resin used for alloy observation can be used.

[0032] Next, the measurement sample is observed at 200,000 times magnification under the condition of an acceleration voltage of 200 V using a transmission electron microscope (TEM) ("JEM-ARM300F2" (trademark) manufactured by JEOL Ltd.) to obtain a dark field image (hereinafter also referred to as the "first image"). In the first image, the tungsten carbide particles are observed as white to gray regions, and the resin is observed as a black region. In the first image, an interface between the tungsten carbide particles and the resin is arbitrarily selected. The interface corresponds to the outer edge of the tungsten carbide particles.

[0033] Next, position the selected interface so that it passes near the center of the image, and adjust the observation magnification so that the field of view size is 30 nm × 30 nm and observe to obtain a second image. In the second image, set a position X1 inside the tungsten carbide particle where the distance along the direction perpendicular to the elongation direction of the interface from the interface is 10 nm or more. Here, the direction perpendicular to the elongation direction of the interface means the direction along a straight line that intersects the tangent of the elongation direction at an angle of 90° ± 5°. Further, in the second image, set a position X2 on the line along the direction perpendicular to the elongation direction of the interface passing through the position X1 and outside the tungsten carbide particle and located within the resin. The distance between the interface and the position X2 is 10 nm or more.

[0034] Perform line analysis using an energy-dispersive X-ray spectrometer (TEM-EDX) attached to a transmission electron microscope along the first direction from the position X1 toward the position X2, and measure the distributions of tungsten and the first element. The conditions during EDX implementation are an acceleration voltage of 200 kV, a camera length of 10 cm, a pixel number of 128 × 128 pixels, and a dwell time of 0.02 to 3 s / pixel.

[0035] Obtain a first graph by showing the line analysis results in a coordinate system where the X-axis is the distance from the position X1 and the Y-axis is the content rate based on the number of atoms of the element. When the first tungsten carbide particle contains two or more types of first elements, the content rate based on the number of atoms of the first element in the first graph is the sum of the content rates based on the number of atoms of all the first elements.

[0036] FIG. 1 is an example of a first graph obtained by performing line analysis on the first tungsten carbide particle of Embodiment 1. In FIG. 1, the horizontal axis (X-axis) indicates the distance [nm] from the position X1, and the vertical axis (Y-axis) indicates the content rate [at%] based on the number of atoms of the element. In FIG. 1, the first element is titanium (Ti).

[0037] In the first graph of FIG. 1, specify the maximum value W of the content rate of tungsten (W). In the first graph, the content rate W of tungsten at 0.5 times the maximum value W max is specified. In the first graph, tungsten at 0.5 times the maximum value W max has a content rate W 0.5maxWe identify the distance P1 that indicates this. In Figure 1, at distances further from the origin than distance P1, there are distances P2 where the titanium (first element) content is maximum, and distance P3 where the oxygen (O) content is maximum.

[0038] In the first graph of Figure 1, the absolute value of the difference between distance P2 and distance P3 is approximately 0 nm.

[0039] As long as the same tungsten primary carbide particles are measured using the procedure described above, it has been confirmed that there is almost no variation in the line analysis results even when the measurement location is changed during line analysis.

[0040] <<Particle Size of First Tungsten Carbide Particles>> In the case where the tungsten carbide powder of Embodiment 1 consists of a plurality of first tungsten carbide particles, the ratio D10 / D90 of the 10% cumulative particle size D10 to the 90% cumulative particle size D90 based on the number of first tungsten carbide particles is 0.05 or more and 0.7 or less, and may also be 0.10 or more and 0.5 or less, 0.15 or more and 0.45 or less, or 0.2 or more and 0.4 or less.

[0041] In the case where the tungsten carbide powder of Embodiment 1 consists of a plurality of primary tungsten carbide particles, the 50% cumulative particle size D50 based on the number of primary tungsten carbide particles may be 0.2 μm or more and 3.0 μm or less, 0.3 μm or more and 2.0 μm or less, 0.4 μm or more and 1.0 μm or less, or 0.5 μm or more and 0.8 μm or less.

[0042] In this disclosure, the cumulative particle size distribution based on the number of primary tungsten carbide particles is measured using a laser diffraction / scattering particle size distribution analyzer, the "MT3000EXII" (trademark) manufactured by MicrotracBEL. The number of primary tungsten carbide particles to be measured is approximately 0.05 g to 2 g, or 30 million or more.

[0043] <Tungsten Carbide Powder>≪Content Ratio of the First Element≫ The content ratio of the first element in the first tungsten carbide powder of Embodiment 1 may be 0.01% by mass or more and 2% by mass or less, 0.1% by mass or more and 1.4% by mass or less, 0.3% by mass or more and 1.2% by mass or less, 0.4% by mass or more and 1.1% by mass or less, or 0.5% by mass or more and 1.0% by mass or less.

[0044] The content ratio of the first element in the first tungsten carbide powder is measured by ICP (Inductively Coupled Plasma) emission analysis (measurement device: "ICPS-8100" (trademark) manufactured by Shimadzu Corporation).

[0045] ≪Content Ratio of Oxygen≫ The content ratio of oxygen in the first tungsten carbide powder of Embodiment 1 may be 0.1% by mass or more and 3% by mass or less, 0.4% by mass or more and 2% by mass or less, 0.6% by mass or more and 1.7% by mass or less, or 0.8% by mass or more and 1.3% by mass or less.

[0046] The content ratio of oxygen in the first tungsten carbide powder is measured by the inert gas fusion-non-dispersive infrared absorption method.

[0047] <Method for Producing Tungsten Carbide Powder>The method for producing the tungsten carbide powder of Embodiment 1 may include a raw material preparation step, a mixing step, a carbonization step, and a pulverization step.

[0048] ≪Raw Material Preparation Step≫ In the raw material preparation step, metal tungsten powder (hereinafter also referred to as "W powder"), carbon powder (hereinafter also referred to as "C powder"), and an oxide powder of the first element are prepared. As the oxide powder of the first element, TiO ２ powder, ZrO ２ powder, Nb ２ O ５ powder, Ta ２ O ５ powder, MoO ２ powder, CeO ２ powder, and Y ２ O ３ powder, at least one selected from the group consisting of is prepared.

[0049] ≪Mixing Process≫ In the mixing process, W powder, C powder, and the oxide powder of the first element are mixed at high speed and then at low speed twice in a Henschel mixer, and then weakly mixed using a wet ball mill to obtain a mixed powder. The high-speed mixing conditions for the Henschel mixer are a rotation speed of 600 rpm. The low-speed mixing conditions for the Henschel mixer are a rotation speed of 200 rpm. The mixing conditions for the wet ball mill are a media diameter of 6 mm, a rotation speed of 60 rpm, and a mixing time of 4 hours.

[0050] ≪Carbonization Process≫ In the carbonization process, the mixed powder is fed into a pressure furnace and subjected to a hydrogen atmosphere (flow rate 10 m³). ３ Heat at 850°C to 1000°C for 4 hours.

[0051] <<Crushing Process>> In the crushing process, the mixed powder after the carbonization process is weakly crushed in an atomizer to obtain the tungsten carbide powder of Embodiment 1. The conditions for the atomizer are: motor inverter frequency: 30 Hz, screen hole diameter: 2.0 mm.

[0052] ≪Features of the Method for Producing Tungsten Carbide Powder in Embodiment 1≫ In the mixing step of the method for producing tungsten carbide powder in Embodiment 1, W powder, C powder, and the oxide powder of the first element are mixed at high speed and then at low speed twice in this order using a Henschel mixer, and then weakly mixed using a wet ball mill, thereby uniformly adhering the oxide powder of the first element to the surface of the W powder. Conventional mixing steps were generally carried out using a mixer, so it was not possible to uniformly adhering the oxide powder of the first element to the surface of the W powder.

[0053] In the carbonization step of the method for producing tungsten carbide powder according to Embodiment 1, the mixed powder is heated in a mixture of hydrogen and argon gas at 850°C to 1000°C for 4 hours. This makes it easier for carbon to carburize the tungsten powder, and thus easier to form WC particles. At this time, because heating at a low temperature of 850°C to 1000°C is used, the decomposition of the first element oxide powder is suppressed, and the first element oxide is more likely to be present on the surface of the WC particles. Conventional carbonization steps were generally carried out at about 1300°C to 1400°C. At about 1300°C to 1400°C, the first element oxide powder reacts with the C powder to form CO and CO ２ This process is prone to occurring, and the oxide powder of the first element is easily decomposed.

[0054] The crushing step in the method for producing tungsten carbide powder of Embodiment 1 includes weak crushing of the mixed powder after the carbonization step using an atomizer. The crushing step allows the mixed powder to be crushed to a desired particle size while suppressing the peeling of oxides of the first element from the surface of the first WC particles.

[0055] [Embodiment 2: Tungsten Carbide Mixed Powder] The tungsten carbide mixed powder according to one embodiment of the present disclosure (hereinafter also referred to as "Embodiment 2") is a tungsten carbide mixed powder comprising two or more types of tungsten carbide particles, wherein at least one of the two or more types of tungsten carbide particles is the first tungsten carbide particle described in Embodiment 1.

[0056] The tungsten carbide mixed powder of Embodiment 2 consists of the first tungsten carbide particles described in Embodiment 1 and a different type of tungsten carbide particles. The different type of tungsten carbide particles is not particularly limited as long as it does not impair the effects of the present disclosure. The different type of tungsten carbide particles may be, for example, tungsten carbide particles consisting only of tungsten carbide, or conventionally known tungsten carbide particles containing additive elements (such as Ti, Nb, Hf, Mo, Ta, Zr). In conventionally known tungsten carbide particles containing additive elements, the form of the additive element is different from the form of the first element in the first tungsten carbide particles.

[0057] The content of primary tungsten carbide particles in the tungsten carbide mixed powder of Embodiment 2 may be 20% by mass or more, 20% by mass or more but less than 100% by mass, 22% by mass or more but less than 100% by mass, 40% by mass or more but less than 100% by mass, 60% by mass or more but less than 100% by mass, or 80% by mass or more but less than 100% by mass.

[0058] The content of primary tungsten carbide particles in the above-mentioned tungsten carbide mixed powder is measured by the following procedure. The tungsten carbide mixed powder is embedded in resin and thinned to obtain a sample for measurement in the same manner as when creating the first graph in Embodiment 1. The sample for measurement is observed using a TEM at an acceleration voltage of 200 V and magnification of 200,000 to obtain a dark-field image (first image). Line analysis is performed on any 10 tungsten carbide particles in the acquired first image in the same manner as when creating the first graph in Embodiment 1 to confirm whether each tungsten carbide particle corresponds to a primary tungsten carbide particle. The equivalent diameter of a circle is calculated from the cross-sectional area of ​​each tungsten carbide particle in the first image. Each tungsten carbide particle is considered a sphere, and the volume ratio of the 10 tungsten particles is calculated based on the equivalent diameter. The ratio of the total volume of primary tungsten carbide particles to the total volume of the 10 tungsten carbide particles is calculated. In this disclosure, the ratio corresponds to the content of primary tungsten carbide particles in the tungsten carbide mixed powder. In the above measurement, primary tungsten carbide particles and other tungsten carbide particles can be considered to have the same density.

[0059] This embodiment will be described in more detail by reference to examples. However, this embodiment is not limited by these examples.

[0060] [Preparation of Tungsten Carbide Powder] Tungsten carbide powder was prepared for each sample using the following procedure. <<Raw Material Preparation Process>> Metallic tungsten powder (W powder), carbon powder (C powder), and oxide powder of the first element were prepared. The oxide powder of the first element was TiO ２ Powder, ZrO ２ powder, Nb ２ O ５ Powder, Ta２ O ５ Powder, MoO ２ powder, CeO ２ Powder, and Y ２ O ３ At least one sample was prepared from the group consisting of powders. The specific surface area of ​​the W powder used in each sample, measured by the BET method, is shown in Tables 1 to 3. The mass ratios of the W powder, C powder, and the first element oxide powder are shown in Tables 1 to 3.

[0061]

[0062]

[0063]

[0064] ≪Mixing Process≫ W powder, C powder, and the oxide powder of the first element were mixed using the method described in A or B below to obtain a mixed powder. A: W powder, C powder, and the oxide powder of the first element were mixed at high speed and then at low speed twice in this order using a Henschel mixer, and then weakly mixed using a wet ball mill to obtain a mixed powder. The high-speed mixing conditions for the Henschel mixer were a rotation speed of 600 rpm. The low-speed mixing conditions for the Henschel mixer were a rotation speed of 200 rpm. The mixing conditions for the wet ball mill were a media diameter of 6 mm, a rotation speed of 60 rpm, and a mixing time of 4 hours. B: W powder, C powder, and the oxide powder of the first element were weakly mixed using a mixer. The mixing conditions for the mixer were a mixing speed of 20 m / s.

[0065] ≪Carbonization Process≫ The mixed powder is placed in a pressure furnace and exposed to a hydrogen atmosphere (flow rate 10 m³). ３ During the interval ( / h), heating was performed at the temperatures and times listed in Tables 1 to 3.

[0066] <<Disintegration Process>> The mixed powder after the carbonization process was gently disintegrated in an atomizer to obtain tungsten carbide powder for each sample. The atomizer conditions were: motor inverter frequency: 30 Hz, screen hole diameter: 2.0 mm.

[0067] [Measurement of Tungsten Carbide Powder] Line analysis was performed on the tungsten carbide particles of each tungsten carbide powder sample to identify the type of primary element contained in the tungsten carbide particles, and a first graph was created. In the first graph, distance P1 is the point where the tungsten content (based on the number of atoms) is 0.5 times the maximum value of the tungsten content (based on the number of atoms), distance P2 is the point where the primary element's content (based on the number of atoms) is at its maximum value, and distance P3 is the point where the oxygen content (based on the number of atoms) is at its maximum value. If a value is written in parentheses in the "P2" column, it indicates that the distance P2 is closer to the origin than the distance P1. If "None" is written in the "P2" column, it indicates that there is no clear peak indicating the maximum value of the primary element in the first graph, and that the primary element is not present on the surface of the tungsten carbide particles. Furthermore, the absolute value of the difference between distance P2 and distance P3, |P2-P3|, is shown in Tables 4 to 6. In all samples, all tungsten carbide particles in the measurement sample showed the results described in Tables 4 to 6. This means that in all samples, all tungsten carbide particles in the tungsten carbide powder showed the results described in Tables 4 to 6.

[0068] The D50, D10 / D90 of tungsten carbide particles, the first element content of tungsten carbide powder, and the oxygen content of tungsten carbide powder were measured using the method described in Embodiment 1. The specific surface area of ​​tungsten carbide particles was measured by the BET method. The results are shown in Tables 4 to 6.

[0069]

[0070]

[0071]

[0072] In samples 1 to 50, the tungsten carbide particles contain the first element, and in the first graph, distances P2 and P3 exist at distances further from the origin than distance P1, with the absolute value of the difference between distances P2 and P3 being between 0 nm and 5 nm. In other words, the tungsten carbide powders of samples 1 to 50 consist of first tungsten carbide particles and correspond to the examples.

[0073] In samples 101, 104, and 106-108, the tungsten carbide particles contained the first element, but in the first graph, distance P2 was located closer to the origin than distance P1. Therefore, the tungsten carbide powders in these samples are comparable to the comparative example.

[0074] In samples 102 and 103, the absolute value of the difference between distance P2 and distance P3 in the first graph was greater than 0.5 nm. Therefore, the tungsten carbide powders in these samples are considered comparative examples.

[0075] In samples 105, 109, and 110, the tungsten carbide particles contained the first element, but since there was no clear peak indicating the maximum value of the first element in the first graph, the distance P2 was "none." Therefore, the tungsten carbide powders in these samples belong to the comparative examples.

[0076] [Preparation of cemented carbide] Using the tungsten carbide powder from each sample, cemented carbide was prepared according to the following procedure. The WC powder prepared from each sample (referred to as "First WC Powder" in Tables 7 to 9), commercially available tungsten carbide powder (Allied Material Co., Ltd. "WC04NR"), and Co powder (average particle size 0.5 μm) were mixed in a ball mill in the mass ratios shown in Tables 7 to 9 to obtain a mixed powder. The mixing conditions in the ball mill were: media diameter: 6 mm, rotation speed: 80 rpm, mixing time: 30 hours.

[0077] A round bar-shaped molded body was obtained by pressing the mixed powder. The molded body was heated at 1400°C for 1 hour, and then rapidly cooled to obtain a cemented carbide intermediate.

[0078] Next, the cemented carbide intermediates were subjected to HIP treatment. Specifically, the cemented carbide intermediates were subjected to 1350°C and a pressure of 30 MPa for 60 minutes using Ar gas as the pressure medium. After that, they were slowly cooled to obtain the cemented carbide alloys for each sample.

[0079]

[0080]

[0081]

[0082] [Cutting Test] Round bars made of cemented carbide for each sample were machined to create radius end mills with a cutting diameter of φ6 mm. Side milling of aged Inconel 718 material was performed using the radius end mills. The machining conditions were: cutting speed Vc 60 m / min, feed per tooth fz 0.05 mm / tooth, depth of cut (axial) ap 2.0 mm, depth of cut (radial) ae 0.2 mm, and wet machining. The cutting length until the tool edge damage reached 100 μm was measured. A longer cutting length indicates a longer tool life. The results are shown in the "Cutting Length" column of "Cutting Test" in Tables 7 to 9. Note that the above machining conditions correspond to high-speed cutting of difficult-to-machine materials.

[0083] [Discussion] The tungsten carbide powders of Samples 1 to 50 correspond to the Examples. The tungsten carbide powders of Samples 101 to 110 correspond to the Comparative Examples. It was confirmed that cutting tools made with cemented carbide alloys manufactured using the tungsten carbide powders of Samples 1 to 50 as raw materials have a longer tool life than cutting tools made with cemented carbide alloys manufactured using the tungsten carbide powders of Samples 101 to 110 as raw materials.

[0084] While embodiments and examples of this disclosure have been described above, it is intended from the outset that the configurations of each of the embodiments and examples described above may be combined or modified in various ways as appropriate. The embodiments and examples disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than the embodiments and examples described above, and all modifications within the scope of the claims are intended to be included in the meaning of equivalences.

Claims

1. A tungsten carbide powder comprising first tungsten carbide particles having an oxide of the first element on its surface, wherein the first element is at least one selected from the group consisting of titanium, zirconium, niobium, tantalum, molybdenum, cerium, and yttrium, and the results obtained by line analysis using an energy-dispersive X-ray spectrometer attached to a transmission electron microscope, from position X1 located inside the first tungsten carbide particles and at a distance of 10 nm or more from the outer edge of the first tungsten carbide particles toward position X2 located outside the first tungsten carbide particles and at a distance of 10 nm or more from the outer edge of the first tungsten carbide particles, are shown in the first graph, which is a coordinate system in which the X axis is the distance from position X1 and the Y axis is the content rate of the element based on the number of atoms, Tungsten carbide powder, wherein the atomic content of tungsten is 0.5 times the maximum atomic content of tungsten, and the distances P2 and P3 where the atomic content of oxygen is maximal are located at a distance P1 from the origin that is greater than the distance P1 where the atomic content of tungsten is 0.5 times the maximum atomic content of tungsten, and the absolute value of the difference between distance P2 and distance P3 is 0 nm or more and 0.5 nm or less.

2. The tungsten carbide powder according to claim 1, wherein the content of the first element in the tungsten carbide powder is 0.01% by mass or more and 2% by mass or less.

3. The tungsten carbide powder according to claim 1 or claim 2, wherein the oxygen content of the tungsten carbide powder is 0.1% by mass or more and 3% by mass or less.

4. The tungsten carbide powder according to any one of claims 1 to 3, wherein the ratio D10 / D90 of the 10% cumulative particle size D10 to the 90% cumulative particle size D90 based on the number of first tungsten carbide particles is 0.05 or more and 0.7 or less.

5. The tungsten carbide powder according to any one of claims 1 to 4, wherein the 50% cumulative particle size D50 based on the number of the first tungsten carbide particles is 0.2 μm or more and 3.0 μm or less.

6. A tungsten carbide mixed powder comprising two or more types of tungsten carbide particles, wherein at least one of the two or more types of tungsten carbide particles is the first tungsten carbide particle described in any one of claims 1 to 5.

7. The tungsten carbide mixed powder according to claim 6, wherein the tungsten carbide mixed powder contains 20% by mass or more of the first tungsten carbide particles.

Images