JP2022085252A - Cutting tool - Google Patents

Abstract

To provide a cutting tool that is improved in abrasion resistance and defect resistance.SOLUTION: A cutting tool 10 is constituted of a ceramic sintered body 1 including tungsten carbide, alumina and zirconia. The ceramic sintered body 1 contains complex carbide of tungsten and cobalt. The complex carbide has a crystal structure which can form a hexagonal crystal. An X-ray diffraction pattern that can be obtained by measuring the ceramic sintered body 1 by X-ray diffraction shows a diffraction pattern in a case where the crystal structure of the complex carbide in the ceramic sintered body 1 forms only the hexagonal crystal.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to cutting tools.

Alumina-tungsten carbide-zirconia-based ceramic compositions are known (see Patent Document 1). In the alumina-tungsten carbide-zirconia-based ceramic composition, zirconium is distributed at the first crystal grain boundary where the alumina crystal particles and the tungsten carbide crystal particles are adjacent to each other and the second crystal grain boundary where the two alumina crystal particles are adjacent to each other. However, the bonding force between the crystal particles at each crystal grain boundary is improved. Therefore, the alumina-tungsten carbide-zirconia-based ceramic composition has excellent mechanical properties, and can be used as a cutting tool for heat-resistant alloys that require high impact resistance and heat resistance.

International Publication No. 2015/01/391

In recent years, cutting tools are required to withstand further improvement in the efficiency of cutting. However, the cutting tool according to the prior art has room for improvement in terms of chipping resistance and fracture resistance, for example, in order to apply it to hardened steel machining in which the cutting speed is increased and a high load state is obtained.
The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a cutting tool having improved chipping resistance and fracture resistance. The present disclosure can be realized in the following forms.

[1] A cutting tool composed of a ceramic sintered body containing tungsten carbide, alumina, and zirconia.
The ceramic sintered body contains a composite carbide of tungsten and cobalt, and contains
The composite carbide has a hexagonal crystal structure and can form a hexagonal crystal.
The X-ray diffraction pattern obtained by measuring the ceramic sintered body by X-ray diffraction is
A cutting tool showing a diffraction pattern when the crystal structure of the composite carbide in the ceramic sintered body is only hexagonal.

[2] The cutting tool according to [1], wherein the composite carbide is present at a grain boundary where two tungsten carbide crystal particles are adjacent to each other.

[3] When the ceramic sintered body is measured by X-ray diffraction and the X-ray diffraction intensity of the (002) plane of tungsten carbide is 100, the X-ray diffraction intensity of the composite carbide of tungsten and cobalt is 9. The cutting tool according to [1] or [2], which is 0 or more and 24.5 or less.

[4] The pedestal made of cemented carbide and the ceramic sintered body according to any one of [1] to [3] bonded to the pedestal via a brazing material, and coated on the surface. A cutting tool with layers formed.

The X-ray diffraction pattern obtained by measuring the ceramic sintered body by X-ray diffraction shows the diffraction pattern when the crystal structure of the composite carbide in the ceramic sintered body is only hexagonal crystals, thereby showing the chipping resistance of the cutting tool. Improves resistance and fracture resistance.
When the composite carbide is present at the grain boundary where the two tungsten carbide crystal particles are adjacent to each other, the chipping resistance and the chipping resistance of the cutting tool are further improved.
When the ceramic sintered body is measured by X-ray diffraction and the X-ray diffraction intensity of the (002) plane of tungsten carbide is 100, the X-ray diffraction intensity of the composite carbide of tungsten and cobalt is 9.0 or more 24. When it is 5 or less, the chipping resistance and the chipping resistance of the cutting tool are further improved.
When a coating layer is formed on the surface, the wear resistance of the cutting tool is improved.

It is a perspective view of an example of a cutting tool. It is an X-ray diffraction pattern of one Example.

Hereinafter, it will be described in more detail. In the present specification, the description using "-" for the numerical range includes the lower limit value and the upper limit value unless otherwise specified. For example, in the description of "10 to 20", both the lower limit value "10" and the upper limit value "20" are included. That is, "10 to 20" has the same meaning as "10 or more and 20 or less".

1. 1. Cutting tool The cutting tool is composed of a ceramic sintered body containing tungsten carbide (WC), alumina (Al ₂ O ₃ ), and zirconia (ZrO ₂ ). The ceramic sintered body contains a composite carbide ((W, Co) C) of tungsten (W) and cobalt (Co). The above-mentioned composite carbide can form a hexagonal crystal structure. The X-ray diffraction pattern obtained by measuring the ceramic sintered body by X-ray diffraction shows the diffraction pattern when the crystal structure of the above-mentioned composite carbide in the ceramic sintered body is only hexagonal crystals.
Hereinafter, the "composite carbide of tungsten and cobalt" is also simply referred to as "composite carbide".

(1) Ceramic sintered body The ceramic sintered body contains a composite carbide of tungsten and cobalt. The composite carbide can have a hexagonal crystal structure. Examples of such composite carbides include composite carbides represented by the composition formulas W ₉ Co ₃ C ₄ , W ₁₀ Co ₃ C ₄ , and W ₁₀ Co ₃ C _3.4 . The composite carbide may be one that can form a crystal structure other than hexagonal, or may be one that cannot form a crystal structure other than hexagonal.

The X-ray diffraction pattern obtained by measuring the ceramic sintered body by X-ray diffraction shows the diffraction pattern when the crystal structure of the composite carbide in the ceramic sintered body is only hexagonal.
Hexagonal composite carbides are tough and hard. Therefore, by containing the hexagonal composite carbide, the toughness of the ceramic sintered body is improved, and the chipping resistance and the chipping resistance of the cutting tool are improved. Further, the ceramic sintered body containing no composite carbide other than hexagonal crystals can maximize the ratio of hexagonal crystals to the total composite carbide, and the above effect can be obtained satisfactorily.

FIG. 2 shows X-rays obtained by measuring a ceramic sintered body containing a composite carbide represented by W ₉ Co ₃ C ₄ by X-ray diffraction of a 2θ / θ concentrated optical system using Cu—Kα rays. It is a diffraction pattern. The vertical axis represents the X-ray diffraction intensity, and the horizontal axis represents the diffraction angle 2θ (°).
When the composition formula of the composite carbide is W ₉ Co ₃ C ₄ , when both the following conditions 1 and 2 are satisfied, the crystal structure of the composite carbide in the ceramic sintered body is only hexagonal. It is judged that it shows the diffraction pattern of.
Condition 1: 2θ in the diffraction pattern has a diffraction peak in the range of 41.0 ° to 42.0 °.
Condition 2: 2θ in the diffraction pattern does not have a diffraction peak in the range of 45.0 ° to 46.0 °. Note that "having no diffraction peak" means that the peak intensity is below the detection limit.
Having a diffractive peak under Condition 1 means that at least one of a hexagonal composite carbide and a cubic composite carbide is present. When both the hexagonal composite carbide and the cubic composite carbide are present, the two peaks overlap, and the pattern is slightly broader than that of only one of them. The absence of the diffractive peak of Condition 2 means that there is no cubic composite carbide.
The diffraction pattern shown in FIG. 2 has a diffraction peak derived from a hexagonal composite carbide marked with a black circle in the range of 41.0 ° to 42.0 ° (see the lower left figure). That is, the condition 1 is satisfied. The diffraction pattern shown in FIG. 2 does not have a diffraction peak derived from a cubic composite carbide in the range of 45.0 ° to 46.0 ° (see the lower right figure). That is, the condition 2 is satisfied. This X-ray diffraction pattern satisfying the conditions 1 and 2 shows the diffraction pattern when the crystal structure of the composite carbide in the ceramic sintered body is only hexagonal.

Even when the composition formula of the composite carbide is W ₁₀ Co ₃ C ₄ or W ₁₀ Co ₃ C _3.4 , the diffraction pattern when the crystal structure of the composite carbide in the ceramic sintered body is only hexagonal is composite. The composition formula of the carbide is almost the same as that expressed by W ₉ Co ₃ C ₄ . Therefore, when both conditions 1 and 2 are satisfied, it is determined that the diffraction pattern is shown when the crystal structure of the composite carbide in the ceramic sintered body is only hexagonal.
Although the mechanism by which the complex carbide having a hexagonal crystal structure is formed is not clear, the temperature is kept substantially constant in a specific temperature range during the temperature rise to a predetermined firing temperature, which is generally performed. By retaining, only hexagonal composite carbides can be formed.

(2) Presence of grain boundaries of composite carbide The composite carbide is preferably present at the grain boundaries where at least two tungsten carbide crystal grains are adjacent interfaces. The presence of the composite carbide at the grain boundaries improves the bonding force between the tungsten carbide crystal particles, and further improves the chipping resistance and chipping resistance of the cutting tool.

It can be confirmed as follows that the composite carbide exists at the grain boundary where the two tungsten carbide crystal particles are adjacent to each other. Any surface of the ceramic sintered body is observed by STEM (Scanning Transmission Electron Microscopy), and the grain boundaries, which are the interfaces where the two tungsten carbide crystal particles are adjacent to each other, are measured by EDS (Energy Dispersive X-ray Spectroscopy) line analysis. .. When such crystal grain boundaries are arbitrarily selected at five locations and the above measurement is performed and composite carbides are observed at any of the locations, the crystal grains at which the two tungsten carbide crystal grains are adjacent interfaces. It is judged that the composite carbide exists in the field.
The presence or absence of the composite carbide at the grain boundary where the two tungsten carbide crystal particles are adjacent to each other can be controlled by adjusting the amount of the composite carbide with respect to the tungsten carbide.

(3) X-ray diffraction intensity ratio of composite carbide When the ceramic sintered body is measured by X-ray diffraction and the X-ray diffraction intensity IA of the (002) plane of tungsten carbide is 100, the composite carbide of tungsten and cobalt The X-ray diffraction intensity IB is preferably 9.0 or more and 24.5 or less.
For the X-ray diffraction intensity IA of the (002) plane of tungsten carbide, for example, a peak height in the vicinity of 2θ = 65.0 ° to 66.0 ° is preferably used.
When the composition formula is W ₉ Co ₃ C ₄ , the X-ray diffraction intensity IB of the composite carbide has a peak in the vicinity of 2θ = 41.0 ° to 42.0 ° and a peak in the vicinity of 2θ = 42.1 ° to 43.0 °. The higher peak height of the peaks is preferably used.

That is, the X-ray diffraction intensity IB of the composite carbide of tungsten and cobalt when the X-ray diffraction intensity IA of the (002) plane of tungsten carbide is 100 is expressed by the peak intensity ratio of the following formula (1). .. This peak intensity ratio is an index showing the content of the composite carbide.
Peak intensity ratio = IB / IA × 100 ... Equation (1)

The peak intensity ratio is preferably 9.0 or more, more preferably 10.5 or more. In this way, the content of the composite carbide becomes sufficient. On the other hand, the peak intensity ratio is preferably 24.5 or less, more preferably 21.0 or less. This is because if the content of the composite carbide is too large, the composite carbide exists in the form of particles, and a starting point for softening at a high temperature is likely to occur. When the value of the peak intensity ratio is within the above range, the effect obtained by the composite carbide can be obtained to the maximum, and the chipping resistance and the chipping resistance of the cutting tool are further improved.

(4) Ratio of components constituting the ceramic sintered body Tungsten carbide (WC), alumina (Al ₂ O ₃ ), zirconia (ZrO ₂ ), tungsten (W) and cobalt (Co) constituting the ceramic sintered body The content of the composite carbide ((W, Co) C) is not particularly limited, but the content of tungsten carbide is 21% by volume or more and 39% by volume or less, and the content of zirconia is 0.50% by volume or more. It is preferable that the content is 0.90% by volume or less, the cobalt content is 0.01% by volume or more and 0.15% by volume or less, and alumina occupies the balance.
The above content is the amount when the total volume of the ceramic sintered body is 100% by volume. The content of each component in the ceramic sintered body can be calculated by obtaining the mass% of each element by a fluorescent X-ray analysis method or the like and converting this into a volume%. Tungsten carbide, alumina, and zirconia are calculated in terms of compounds. Cobalt is calculated assuming that it exists alone. The cobalt content is a numerical value expressed up to the second decimal place by rounding off the third decimal place.

The ceramic sintered body may contain impurities. Impurities are substances that are unintentionally mixed in the manufacturing process, and examples thereof include at least one of iron (Fe), chromium (Cr), and nickel (Ni). The amount of impurities may be an amount (for example, 0.1% by mass or less) that hardly deteriorates the characteristics (bending strength, thermal conductivity, etc.) of tungsten carbide.

By keeping the content of each component within a preferable range, chipping resistance and chipping resistance can be further improved. The reason for this is presumed as follows. By keeping the content of each component within a preferable range, the balance between tungsten carbide having excellent hardness and alumina having excellent reactivity with the work material becomes suitable. In addition, the effect that the two tungsten carbide crystal particles are firmly bonded to each other by the composite carbide and the effect that the alumina crystal particles and the tungsten carbide crystal particles and the two alumina crystal particles are firmly bonded to each other by zirconium are maximized. can get. It is considered that this improves the chipping resistance and the chipping resistance of the cutting tool.

The method of adding cobalt is not particularly limited. For cobalt, cobalt powder may be added directly to the raw material. As cobalt, for example, abrasion powder obtained by air-rubbing only with cobalt-containing super hard ball stone and ethanol may be used. Although the exact reason is not known, the use of wear debris is expected to have a high effect on chipping resistance and chipping resistance.

(5) Manufacturing method of cutting tool The manufacturing method of the cutting tool is not particularly limited. An example of a cutting tool manufacturing method is shown below. Here, an example of the case where cobalt is contained will be described.

(5.1) Raw materials The following raw material powders are used as raw materials.
-Alumina powder (Al ₂ O ₃ powder)
・ Tungsten carbide powder (WC powder)
・ Zirconia powder (ZrO ₂ powder)
・ Cobalt powder (Co powder)

(5.2) Preparation of mixed dry powder Prepare alumina powder, tungsten carbide powder, zirconia powder, and cobalt powder. Each raw material powder is weighed so as to have a predetermined ratio, put into a ball mill together with a solvent and a dispersant, and mixed and pulverized to obtain a slurry. The solvent is removed from the slurry by degassing the obtained slurry while boiling it in hot water. Then, the mixed powder is prepared by passing the powder through a sieve.

(5.3) Firing The obtained mixed dry powder is put into a carbon jig and fired by hot pressing at a predetermined temperature. Conventionally, when manufacturing a ceramic sintered body, a firing process (referred to here as the main firing process here for convenience) of firing at a predetermined firing temperature at a predetermined press pressure has been adopted. On the other hand, prior to this main firing process, the crystal structure of the composite carbide is controlled by providing a preliminary firing process in which the temperature is kept substantially constant in a specific temperature range during the temperature rise to a predetermined firing temperature. Will be done. For the pre-baking process, for example, a pressurizing time of 10 to 60 minutes in a temperature range of 1000 ° C to 1200 ° C is preferably adopted. The pressure in the pre-baking process may be the same as in the main firing process.

(6) Coating layer A coating layer may be formed on the surface of the cutting tool. When the coating layer is formed, the surface hardness of the cutting tool is increased, and the progress of wear due to reaction and welding with the workpiece is suppressed. As a result, the wear resistance of the cutting tool is improved.
The components of the coating layer are not particularly limited. The coating layer is formed from at least one compound selected from carbides of titanium, zirconium, chromium and aluminum, nitrides, oxides, carbonitrides, carbonitrides, oxynitrides, and carbonitride oxides. Is preferable. The at least one compound selected from the carbides, nitrides, oxides, carbonitrides, carbonitrides, oxynitrides, and carbonitride oxides of titanium, zirconium, chromium, and aluminum is not particularly limited, but is not limited to TiN. , TiAlN, TiAlVN are preferred examples.
The coating layer may be a single layer or a plurality of layers. Further, the thickness thereof is not particularly limited. The thickness of the coating layer is preferably 0.02 μm or more and 30 μm or less from the viewpoint of wear resistance.

(7) Applications of cutting tools Cutting tools can be applied to various conventionally known cutting tools. As the cutting tool, a tip exchange type tip (cutting insert, throw away tip) for turning or milling, and an end mill can be preferably exemplified. A cutting tool is a cutting tool in a broad sense, and refers to all tools for turning, milling, and the like.

2. 2. Cutting tool 10
As illustrated in FIG. 1, the cutting tool 10 includes a pedestal 11 made of cemented carbide and a ceramic sintered body 1 bonded to the pedestal 11 via a brazing material. A coating layer is formed on the surface of the cutting tool 10. The coating layer is preferably formed on at least the surface of the ceramic sintered body 1.
The composition of the cemented carbide is not particularly limited. As the cemented carbide, for example, a cemented carbide containing tungsten carbide crystal particles (hereinafter, also referred to as “tungsten carbide (WC) -based cemented carbide”) can be preferably mentioned. Examples of the tungsten carbide-based cemented carbide include WC-Ni—Cr-based cemented carbide, WC-Co-based cemented carbide, and WC-Co-Cr-based cemented carbide.
The components of the brazing material are not particularly limited. The brazing material contains, for example, an active metal and one or more kinds of metals having ductility. Examples of the active metal include titanium (Ti), zirconium (Zr), hafnium (Hf) and the like. Examples of the metal having ductility include gold (Au), silver (Ag), copper (Cu), nickel (Ni) and the like. Examples of the brazing material include Au—Ni—Ti alloy and the like.

The cutting tool 10 can be applied to various conventionally known cutting tools. As such a cutting tool, a cutting tool for turning or milling, an end mill, and a reamer can be preferably exemplified. The cutting tool 10 is a cutting tool in a broad sense, and refers to all tools for turning, milling, and the like.

In the following experiments, the ceramic sintered bodies of Examples 1 to 10 and Comparative Examples 1 to 4 were prepared, and each of these ceramic sintered bodies was processed to form Examples 1 to 10 and Comparative Examples 1 to 4. Each cutting tool was used.

1. 1. Preparation of ceramic sintered body (1) Raw material The following raw material powder was used as a raw material.
-Alumina powder (Al ₂ O ₃ powder): Average particle size 0.5 μm
-Tungsten carbide powder (WC powder): Average particle size 0.5 μm
-Zirconia powder (ZrO ₂ powder): Average particle size 0.5 μm
-Cobalt powder (Co powder): Average particle size 0.5 μm

(2) Preparation of mixed dry powder Alumina powder, tungsten carbide powder, zirconia powder, and cobalt powder were prepared. Each raw material powder was weighed according to the ratio shown in Table 1, put into a ball mill together with a solvent and a dispersant, and mixed and pulverized to obtain a slurry. As the solvent, ethanol or the like was used. As the dispersant, Floren G-700 (manufactured by Kyoeisha Chemical Co., Ltd.), SN Dispersant 9228 (manufactured by San Nopco Ltd.), Marialim AKM-0531 (manufactured by NOF Corporation) and the like were used. The solvent was removed from the slurry by degassing the obtained slurry while boiling it in hot water. Then, the mixed powder was prepared by passing the powder through a sieve.
The steps (1) and (2) up to this point are common to all the ceramic sintered bodies of Examples and Comparative Examples.

(3) Firing (3-1) Ceramic sintered bodies of Examples 1 to 10 and Comparative Example 1 Ceramic sintered bodies of Examples 1 to 10 and Comparative Example 1 are hot-press fired by the following method to fire ceramics. I got a unity.
That is, the obtained mixed dry powder was put into a carbon jig and hot-press fired at the firing temperatures shown in Table 1 to prepare a ceramic sintered body. The firing time was 45 minutes to 1.5 hours, the pressure was 20 MPa to 40 MPa, and the atmosphere gas was argon (Ar). The mixed dry powder was held at the holding temperature shown in Table 1, the pressure was 20 MPa to 40 MPa, and the atmospheric gas was argon (Ar) for 10 to 60 minutes when the temperature was raised before reaching the firing temperature. As described above, the ceramic sintered bodies of Examples 1 to 10 and Comparative Example 1 were obtained.
(3-2) Ceramic sintered body of Comparative Examples 2 to 4 The ceramic sintered body of Comparative Examples 2 to 4 does not hold in a specific temperature range when the temperature rises before reaching the firing temperature, and is a conventional hot. Press firing was adopted. In addition, "no holding" in the column of "holding temperature" in Table 1 means "not holding in a specific temperature range at the time of raising the temperature before reaching the firing temperature". As described above, the ceramic sintered bodies of Comparative Examples 2 to 4 were obtained.

2. 2. XRD analysis (X-ray diffraction analysis)
(1) Measurement method The ceramic sintered body was measured by X-ray diffraction of a 2θ / θ concentrated optical system using Cu—Kα rays to obtain an X-ray diffraction pattern. The measurement conditions were as follows.
・ X-ray diffractometer Rigaku Co., Ltd. X-ray diffractometer RINT-TTR III
・ X-ray diffraction condition Output: 45 kV, 200 mA
Scan speed: 2 ° / min Step width: 0.02 °
2θ measurement range: 20 ° to 80 °

(2) X-ray diffraction pattern When the X-ray diffraction pattern of the ceramic sintered body of Examples 1 to 10 was analyzed, the conditions 1 and 2 described in the embodiment were satisfied. That is, the ceramic sintered bodies of Examples 1 to 10 showed a diffraction pattern when the crystal structure of the composite carbide in the ceramic sintered body was only hexagonal.
The ceramic sintered body of Comparative Example 1 is a ceramics sintered body that does not contain cobalt as a raw material, that is, does not form a composite carbide. In the ceramic sintered body of Comparative Example 1, no diffraction peak derived from the composite carbide in the ceramic sintered body was confirmed.
The ceramic sintered bodies of Comparative Examples 2 to 4 are ceramic sintered bodies that are not held in a specific temperature range when the temperature is raised before reaching the firing temperature. When the X-ray diffraction patterns of the ceramic sintered bodies of Comparative Examples 2 to 4 were analyzed, the condition 1 described in the embodiment was satisfied, but the condition 2 was not satisfied. That is, in the ceramic sintered bodies of Comparative Examples 2 to 4, the diffraction pattern when the crystal structure of the composite carbide in the ceramic sintered body is only cubic crystals is shown.
In the column of "crystal structure" in Table 1, "hexagonal crystal" indicates a diffraction pattern when the crystal structure of the composite carbide in the ceramic sintered body is only hexagonal crystal, and is "cubic crystal". Indicates a diffraction pattern when the crystal structure of the composite carbide in the ceramic sintered body is only cubic crystals. In Comparative Example 1, the diffraction peak derived from the composite carbide was not detected, and it was designated as "-".

(3) X-ray diffraction intensity ratio of the composite carbide The X-ray diffraction intensity IA of the (002) plane of the tungsten carbide and the X-ray diffraction intensity IB of the composite carbide were measured. The X-ray diffraction intensities IA and IB were defined as peak heights at the following 2θ values.
X-ray diffraction intensity IA: Peak height near 2θ = 65.0 ° to 66.0 ° X-ray diffraction intensity IB: Peak near 2θ = 41.0 ° to 42.0 ° and 2θ = 42.1 ° to Peak height of the higher of the peaks near 43.0 ° For each ceramic sintered body, the X-ray diffraction intensities IA and IB were obtained, and the value of the peak intensity ratio (IB / IA × 100) was calculated. did.

The calculated peak intensity ratio is shown in Table 1. In Comparative Example 1, the diffraction peak derived from the composite carbide was not detected, and the peak intensity ratio was not calculated.
Among the ceramic sintered bodies of Examples 1 to 10, the ceramic sintered bodies of Examples 2, 4 to 7, 9 had an IB / IA × 100 value of 9.0 or more and 24.5 or less.

3. 3. Presence of grain boundaries of composite carbide (1) Measurement method The surface of the ceramic sintered body was observed by STEM, and the crystal grain boundaries, which are the interfaces where the two tungsten carbide crystal grains are adjacent to each other, were measured by EDS line analysis. Five such grain boundaries were arbitrarily selected, and it was confirmed whether or not composite carbides were observed. When composite carbides are observed at any of the five selected crystal grain boundaries, it is determined that "composite carbides are present at the grain boundaries at the interface where the two tungsten carbide crystal grains are adjacent to each other" and selected. When no composite carbide was observed at at least one of the five grain boundaries, it was determined that "the complex carbide does not exist at the crystal grain boundary where the two tungsten carbide crystal grains are adjacent to each other".

(2) Measurement results The measurement results are shown in the column of "Presence of grain boundaries of composite carbide" in Table 1. In the column of "presence of grain boundaries of composite carbide", "yes" means "composite carbide exists at the crystal grain boundary where two tungsten carbide crystal grains are adjacent to each other", and "no" means "absence". There is no composite carbide at the grain boundaries, which is the interface where the two tungsten carbide crystal grains are adjacent to each other. "
Of the ceramic sintered bodies of Examples 1 to 10, in the ceramic sintered bodies of Examples 1 to 4, 6, 7, and 9, composite carbides are present at the grain boundaries, which are the interfaces where the two tungsten carbide crystal particles are adjacent to each other. It was observed to do.

4. Cutting test (1) Test method A cutting tool composed of the ceramic sintered bodies of Examples 1 to 10 and Comparative Examples 1 to 4 was produced. A cutting test was performed using each cutting tool to evaluate chipping resistance and chipping resistance. The test conditions are as follows.
-Tool shape: TNGA160408Z01225
-Work material: High hardness material (SCM415)
・ Cutting speed: 300m / min
・ Cut amount: 0.1 mm
-Feed amount: 0.2 mm / rev.
・ Cutting environment: DRY

(2) Test results The test results are also shown in Table 1 and examined.
The cutting tools of Examples 1 to 10 satisfy the following first requirement. On the other hand, the cutting tools of Comparative Examples 1 to 4 do not satisfy the first requirement. In the cutting tools of Examples 1 to 10, chipping did not occur at the cutting edge even after machining 2 km. Further, the cutting tools of Examples 1 to 10 did not have any defects even after machining for 3 km. In the cutting tools of Comparative Examples 1 to 4, chipping occurred at the cutting edge after machining at most 1.5 km. Further, the cutting tools of Comparative Examples 1 to 4 had a defect and could not be machined for 3 km. As described above, the cutting tools of Examples 1 to 10 had higher chipping resistance and chipping resistance than the cutting tools of Comparative Examples 1 to 4.
[First requirement]: The X-ray diffraction pattern obtained by measuring the ceramic sintered body by X-ray diffraction shows a diffraction pattern when the crystal structure of the composite carbide in the ceramic sintered body is only hexagonal crystals.

Next, the cutting tools of Examples 1 to 10 will be compared and examined.
All of the cutting tools of Examples 2, 4, 6 and 9 satisfy the following second, third and fourth requirements in addition to the first requirement. The cutting tools of Examples 2, 4, 6 and 9 did not cause chipping even after machining 3 km, and showed the best chipping resistance. Therefore, it was confirmed that the chipping resistance is further improved by satisfying the second, third, and fourth requirements in addition to the first requirement.
The cutting tool of Example 1 satisfying the first requirement and the second requirement showed superior chipping resistance than the cutting tool of Example 10 satisfying only the first requirement.
The cutting tool of Example 5 satisfying the first requirement and the third requirement showed superior chipping resistance than the cutting tool of Example 10 satisfying only the first requirement.
The cutting tool of Example 8 satisfying the first requirement and the fourth requirement showed superior chipping resistance than the cutting tool of Example 10 satisfying only the first requirement.
[Second requirement]: The composite carbide is present at the grain boundary where the two tungsten carbide crystal particles are adjacent to each other.
[Third requirement]: When the ceramic sintered body is measured by X-ray diffraction and the X-ray diffraction intensity of the (002) plane of tungsten carbide is 100, the X-ray diffraction intensity of the composite carbide of tungsten and cobalt is It is 9.0 or more and 24.5 or less.
[Fourth requirement]: In the ceramic sintered body, tungsten carbide is 21% by volume or more and 39% by volume or less, cobalt is 0.01% by volume or more and 0.15% by volume or less, and zirconia is 0.50% by volume. It is 0.90% by volume or less, and alumina occupies the balance. As described in the embodiment, each volume% is expressed in terms of compounds for tungsten carbide, alumina, and zirconia, and is calculated assuming that cobalt exists as a simple substance. Table 1 shows the composition (blending) of the raw material powder of the ceramic sintered body as described above, and this composition is equivalent to the composition of each ceramic sintered body converted into a compound.

The cutting tool of Comparative Example 1 containing no composite carbide was chipped at the cutting edge during machining and was chipped.
The cutting tool of Comparative Example 2 satisfied the second and third requirements, but chipped at the cutting edge during machining and was damaged.
The cutting tool of Comparative Example 3 satisfied the fourth requirement, but chipping occurred at the cutting edge during machining and the cutting tool was damaged.
The cutting tool of Comparative Example 4 satisfied the third and fourth requirements, but chipping occurred at the cutting edge during machining and the cutting tool was damaged.

From the above results, it was confirmed that the cutting tool satisfying the first requirement has good chipping resistance and chipping resistance.

The present invention is not limited to the embodiments detailed above, and various modifications or modifications can be made within the scope of the claims of the present invention.

1 ... Ceramic sintered body 10 ... Cutting tool 11 ... Pedestal

Claims (4)

A cutting tool composed of a ceramic sintered body containing tungsten carbide, alumina, and zirconia.
The ceramic sintered body contains a composite carbide of tungsten and cobalt, and contains
The composite carbide has a hexagonal crystal structure and can form a hexagonal crystal.
The X-ray diffraction pattern obtained by measuring the ceramic sintered body by X-ray diffraction is
A cutting tool showing a diffraction pattern when the crystal structure of the composite carbide in the ceramic sintered body is only hexagonal. The cutting tool according to claim 1, wherein the composite carbide is present at a grain boundary where two tungsten carbide crystal particles are adjacent to each other. When the ceramic sintered body is measured by X-ray diffraction and the X-ray diffraction intensity of the (002) plane of tungsten carbide is 100, the X-ray diffraction intensity of the composite carbide of tungsten and cobalt is 9.0 or more and 24. 5. The cutting tool according to claim 1 or claim 2, which is 5 or less. A pedestal made of cemented carbide and a ceramic sintered body according to any one of claims 1 to 3 bonded to the pedestal via a brazing material, and a coating layer is formed on the surface thereof. Cutting tool.

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