JPWO2018198719A1 - Cutting tools - Google Patents

Abstract

The cutting tool includes a sintered body including a first hard phase, a binder phase, and Al2O3. The first hard phase consists of WC. The binder phase includes, as main components, a first metal composed of at least one selected from Co and Ni, and further includes a second metal composed of at least one selected from Al and W, and C. Al2O3 is dispersed in the sintered body.

Description

  The present invention relates to a cutting tool. This application claims priority based on Japanese Patent Application No. 2017-086857 filed on April 26, 2017 and International Patent Application No. PCT / JP2017 / 042850 filed on November 29, 2017. The entire contents described in the patent application are incorporated herein by reference.

  Products requiring high hardness include, for example, cutting tools. As hard materials (sintered bodies) used for such products, cemented carbides, cermets and the like are known.

  Here, cutting tools and the like are often exposed to high temperatures. At high temperatures, wear of the sintered body is promoted, and it may not be possible to achieve a desired life of a product. Therefore, a sintered body used for a cutting tool or the like is required to have wear resistance at a high temperature.

In order to impart high-temperature wear resistance to a cemented carbide, for example, Patent Document 1 (Japanese Patent Application Laid-Open No. Hei 9-125229) discloses that a film having excellent wear resistance at high temperatures is formed on a cemented carbide. Techniques are disclosed. Patent Document 2 (Japanese Patent Application Laid-Open No. 2014-208889) discloses a sintered body containing hard particles composed of WC and a metal phase represented by (Co, Ni) ₃ (Al, W, V, Ti). It has been disclosed.

JP-A-9-125229 JP 2014-208889 A

A cutting tool according to an aspect of the present disclosure includes a sintered body including a first hard phase, a binder phase, and Al ₂ O ₃ . The first hard phase consists of WC. The binder phase includes, as main components, a first metal composed of at least one selected from Co and Ni, and further includes a second metal composed of at least one selected from Al and W, and C. Al ₂ O ₃ is dispersed in the sintered body.

FIG. 1 is a reference diagram relating to evaluation of a cutting tool.

[Problems to be solved by the present disclosure]
However, recently, there has been a growing need for processing difficult-to-cut materials such as heat-resistant alloys, and an improvement in cutting speed is also required. For this reason, cutting tools are required to have higher wear resistance at higher temperatures. In the technique of Patent Document 1, when the coating is peeled off, the wear resistance is rapidly reduced due to, for example, softening of a binder phase (metal cobalt or the like) in the sintered body, and the cemented carbide immediately reaches the end of its life. Therefore, the technique of Patent Document 1 is not sufficient for such needs. For this reason, it is desired to further improve the wear resistance of the base material of the sintered body itself at high temperatures.

  Accordingly, an object of the present disclosure is to provide a cutting tool having improved wear resistance at high temperatures.

[Effects of the present disclosure]
According to the above, a cutting tool with improved wear resistance at high temperatures can be provided.

[Description of Embodiment of the Present Disclosure]
First, embodiments of the present disclosure are listed and described.

  In this specification, the notation in the form of “A to B” means the upper and lower limits of the range (that is, A or more and B or less), where no unit is described in A, and only the unit is described in B , A and B are the same.

[1] A cutting tool according to an aspect of the present disclosure includes a sintered body including a first hard phase, a binder phase, and Al ₂ O ₃ . The first hard phase consists of WC. The binder phase includes, as main components, a first metal composed of at least one selected from Co and Ni, and further includes a second metal composed of at least one selected from Al and W, and C. Al ₂ O ₃ is dispersed in the sintered body. The sintered body has improved wear resistance at high temperatures. By improving the wear resistance of the sintered body at a high temperature, the life of the cutting tool can be extended.

[2] The binder phase preferably contains a compound phase represented by the following formula.
_{(Co, Ni) x (Al} , W) y C z
[Wherein (Co, Ni) is at least one selected from Co and Ni, (Al, W) is at least one selected from Al and W, and x, y and z are atomic weight ratios. It is. This allows the sintered body to maintain high hardness particularly at high temperatures.

  [3] x is preferably 0.73 or more and 0.95 or less, y is 0.04 or more and 0.25 or less, and z is preferably 0.003 or more and 0.15 or less. This is because an improvement in the wear resistance of the sintered body at high temperatures is expected.

  [4] x is preferably 0.75 or more and 0.93 or less, y is 0.05 or more and 0.2 or less, and z is preferably 0.005 or more and 0.1 or less. This is because an improvement in the wear resistance of the sintered body at high temperatures is expected.

  [5] It is preferable that x is 0.8 or more and 0.9 or less, y is 0.06 or more and 0.15 or less, and z is 0.01 or more and 0.05 or less. This is because an improvement in the wear resistance of the sintered body at high temperatures is expected.

  [6] The sintered body preferably further contains a second hard phase. The second hard phase is at least one metal selected from the group consisting of Ti, Zr, Hf, Nb, Ta, Cr, Mo and W, and at least one metal selected from the group consisting of nitrogen, carbon, boron and oxygen. And a solid solution of the compound (excluding WC). Here, the first hard phase has a larger volume ratio than the second hard phase. This is because an improvement in the wear resistance of the sintered body at high temperatures is expected.

[7] Al ₂ O ₃ is preferably contained in the sintered body in an amount of 1% by volume to 15% by volume. In this case, the effect of improving the wear resistance at a high temperature can be more reliably obtained, and the effect of suppressing a decrease in the strength of the sintered body is expected.

[8] Al ₂ O ₃ preferably has an average circle equivalent diameter of 0.1 μm or more and 2 μm or less, and a standard deviation of 0.05 μm or more and 0.25 μm or less. In this case, the effect of improving the hardness of the sintered body is expected. Further, an effect of suppressing a decrease in toughness of the sintered body is expected.

[9] It is preferable that Al ₂ O ₃ has an average circle equivalent diameter of 0.2 μm or more and 1 μm or less and a standard deviation of 0.05 μm or more and 0.15 μm or less. In this case, the effect of further improving the hardness of the sintered body is expected. Further, an effect of suppressing a decrease in toughness of the sintered body is expected.

[10] It is preferable that Al ₂ O ₃ has an average circle equivalent diameter of 0.3 μm or more and 0.5 μm or less and a standard deviation of 0.05 μm or more and 0.1 μm or less. In this case, the effect of further improving the hardness of the sintered body is expected. Further, an effect of suppressing a decrease in toughness of the sintered body is expected.

[11] Al ₂ O ₃ preferably has an average value of the inter-particle distance of 1 μm or more and 3 μm or less, and a standard deviation of 0.5 μm or more and 1.5 μm or less. In this case, the effect of maintaining the balance of hardness and toughness is expected.

  [12] The ratio of the mass of O to the mass of C contained in the sintered body (O / C ratio) is preferably 0.015 or more and 0.061 or less. In this case, it is expected that [8] and [11] are satisfied.

  [13] The content of oxygen in the sintered body is preferably from 0.1% by mass to 0.4% by mass. In this case, the effect of improving the hardness of the sintered body and the effect of suppressing defects are expected.

  [14] The binder phase preferably has a lattice constant of 3.65 ° or more and 4.0 ° or less. In this case, the effect of maintaining the high hardness of the sintered body at a higher temperature and the effect of suppressing the loss of the sintered body are expected.

  [15] The WC preferably has an average particle diameter of 0.1 μm or more and 3 μm or less. In this case, the effect of suppressing the loss of the sintered body is expected.

  [16] The content of the binder phase in the sintered body is preferably 2% by mass or more and less than 10% by mass. In this case, an effect of suppressing the loss of the sintered body and an effect of suppressing a decrease in the high-temperature hardness of the sintered body are expected.

[Details of Embodiment of the Present Disclosure]
Hereinafter, an embodiment of the present disclosure (hereinafter, referred to as “the present embodiment”) will be described. However, the following description does not limit the present disclosure. Further, in the present specification, when a compound or the like is represented by a chemical formula, unless otherwise specified, the atomic ratio includes all conventionally known atomic ratios, and is not necessarily limited to a stoichiometric range.

<Cutting tools>
The cutting tool according to the present embodiment includes the following sintered body. Cutting tools include drills, end mills, replaceable cutting tips for drills, replaceable cutting tips for end mills, replaceable cutting tips for milling, replaceable cutting tips for turning, metal saws, and gear cutting tools. , Reamer, tap, and the like.

  Further, a coating may be provided on the surface of the sintered body. This makes it possible to impart the characteristics of the coating to the cutting tool.

As the coating, it is preferable to use a coating having a coefficient of thermal expansion of 7 × 10 ⁻⁶ / K or more and 9 × 10 ⁻⁶ / K or less. Ti, Al, Cr, Si, Hf, Zr, Mo, Nb, Ta , V and W are more preferably made of a nitride or carbonitride of one or more metals selected from the group consisting of:

  Further, the coating preferably has an oxidation resistance of 1000 ° C. or higher. Here, “having an oxidation resistance of 1000 ° C. or more” means that the coating layer is evaluated in the atmosphere by a thermal analysis-simultaneous differential thermal / thermogravimetric (TG / DTA) apparatus. Means that the temperature at which the weight increase occurs is 1000 ° C. or higher. Preferable examples of the composition constituting such a coating layer having oxidation resistance include AlTiSiN, AlCrN, TiZrSiN, CrTaN, HfWSiN, CrAlN, and the like.

  The above film can be formed by any of the PVD method and the CVD method, but is preferably formed by the PVD method. In this case, it is possible to form a denser film that is less likely to crack. In particular, it is preferable to use the cathode arc ion plating method in that the adhesion between the coating and the sintered body is significantly improved.

<Sintered body>
The sintered body according to the present embodiment includes a first hard phase, a binder phase, and Al ₂ O ₃ . The sintered body may contain components other than these as long as it contains them. The first hard phase consists of WC. Al ₂ O ₃ is dispersed in the sintered body.

  The binder phase includes, as main components, a first metal composed of at least one selected from Co and Ni, and further includes a second metal composed of at least one selected from Al and W, and C. The “main component” means a component having the largest blending ratio (% by mass) among the components constituting the binder phase. Thus, the sintered body contains C in the binder phase. For this reason, the high-temperature hardness of the binder phase is improved by solid solution strengthening, and the wear resistance of the sintered body at high temperatures is improved.

Further, in a cemented carbide comprising a hard phase and a binder phase, the binder phase is made of a heat-resistant alloy (such as a Co-based superalloy or a Ni-based superalloy) instead of metal Co. Heat-resistant alloys are materials used for components used at high temperatures, such as jet engines and gas turbines, and have excellent heat resistance at high temperatures. Further, the sintered body contains Al ₂ O ₃ having a higher hardness than WC. As a result, the hardness of the sintered body itself is improved.

  It is preferable that the first hard phase and the binder phase are contained in a state of being dispersed in the sintered body. Thereby, the wear resistance of the sintered body at a high temperature is improved. Here, the dispersed state means that the first hard phase and the binder phase are in contact with each other, and the phase of the same kind is present in the sintered body in a state of relatively little contact between the phases.

The binding phase preferably contains a compound phase represented by the following formula.
_{(Co, Ni) x (Al} , W) y C z
[Wherein (Co, Ni) is at least one selected from Co and Ni, (Al, W) is at least one selected from Al and W, and x, y and z are atomic weight ratios. It is. ]
Note that oxygen may be contained (solid-solved) in the binder phase.

Such a sintered body contains (Co, Ni) _x (Al, W) in the binder phase [in the matrix phase (γ phase) composed of the first metal (Co, Ni) and the second metal (Al, W)]. W) by including a compound phase represented by _y C _z, the sintered body, it is possible to particularly maintaining high hardness at elevated temperatures.

  It is preferable that x is 0.73 or more and 0.95 or less, y is 0.04 or more and 0.25 or less, and z is 0.003 or more and 0.15 or less. This is because an improvement in the wear resistance of the sintered body at high temperatures is expected.

  It is preferable that x is 0.75 or more and 0.93 or less, y is 0.05 or more and 0.2 or less, and z is 0.005 or more and 0.1 or less. This is because an improvement in the wear resistance of the sintered body at high temperatures is expected.

  It is preferable that x is 0.8 or more and 0.9 or less, y is 0.06 or more and 0.15 or less, and z is 0.01 or more and 0.05 or less. This is because an improvement in the wear resistance of the sintered body at high temperatures is expected.

  It is preferable that the sintered body further includes a second hard phase. The second hard phase is at least one metal selected from the group consisting of Ti, Zr, Hf, Nb, Ta, Cr, Mo and W, and at least one metal selected from the group consisting of nitrogen, carbon, boron and oxygen. And a solid solution of the compound (excluding WC). Here, the first hard phase has a larger volume ratio than the second hard phase.

  Since the binder phase has higher affinity with the first hard phase than with the second hard phase, the volume ratio of the first hard phase is larger than that of the second hard phase, so that the abrasion resistance and the like of the sintered body are improved. It is expected that the sintered body will have improved wear resistance at high temperatures.

Preferably, Al ₂ O ₃ is contained in the sintered body in an amount of 1% by volume or more and 15% by volume or less. If the amount of Al ₂ O ₃ is too small, the effect of improving wear resistance at high temperatures may not be obtained. On the other hand, if the amount of Al ₂ O ₃ is too large, the strength of the sintered body is reduced and defects are likely to occur. For this reason, when the content of Al ₂ O ₃ is in the above range, the effect of improving the wear resistance at high temperatures is more reliably obtained, and the effect of suppressing the decrease in the strength of the sintered body is expected. .

Al ₂ O ₃ preferably has an average circle equivalent diameter of 0.1 μm or more and 2 μm or less, and a standard deviation of 0.05 μm or more and 0.25 μm or less. When Al ₂ O ₃ is fine, an effect of further improving the hardness of the sintered body is expected. On the other hand, if Al ₂ O ₃ is too fine, the toughness of the sintered body is reduced and defects are liable to occur, so that the effect of suppressing the decrease in toughness of the sintered body in the above range is expected.

Al ₂ O ₃ preferably has an average circle equivalent diameter of 0.2 μm or more and 1 μm or less, and a standard deviation of 0.05 μm or more and 0.15 μm or less. When Al ₂ O ₃ is fine, an effect of further improving the hardness of the sintered body is expected. On the other hand, if Al ₂ O ₃ is too fine, the toughness of the sintered body is reduced and defects are liable to occur, so that the effect of suppressing the decrease in toughness of the sintered body in the above range is expected.

It is preferable that Al ₂ O ₃ has an average circle equivalent diameter of 0.3 μm or more and 0.5 μm or less, and a standard deviation of 0.05 μm or more and 0.1 μm or less. When Al ₂ O ₃ is fine, an effect of further improving the hardness of the sintered body is expected. On the other hand, if Al ₂ O ₃ is too fine, the toughness of the sintered body is reduced and defects are liable to occur, so that the effect of suppressing the decrease in toughness of the sintered body in the above range is expected.

Al ₂ O ₃ preferably has an average value of the interparticle distance of 1 μm or more and 3 μm or less, and a standard deviation of 0.5 μm or more and 1.5 μm or less. By uniformly dispersing the binder phase, the effect of maintaining the balance of hardness and toughness is expected. When the distance between the particles is out of the range of 1 to 3 μm, the degree of dispersion of the binder phase is biased, so that defects tend to occur. The inter-particle distance is set for each of the Al ₂ O ₃ particles. "Interparticle distance" in any one of Al ₂ O ₃ particles, the distance between the center of gravity of the Al ₂ O ₃ particles, and other Al ₂ O ₃ particles having a center of gravity to the position nearest the heavy center point It is. The “average value of the distance between particles” is the average value of all the “distances between particles”.

The ratio of the mass of O to the mass of C contained in the sintered body (O / C ratio) is preferably 0.015 or more and 0.061 or less. In this range, Al ₂ O ₃ is expected to be uniformly dispersed and precipitated, and satisfy [8] and [11].

It is preferable that the content of oxygen in the sintered body is 0.1% by mass or more and 0.4% by mass or less. If the oxygen content is 0.1% by mass or less, Al ₂ O ₃ may not precipitate and the hardness may not be improved. If the oxygen content is 0.4% by mass or more, Al ₂ O ₃ may aggregate to easily cause defects. For this reason, when the oxygen content is in the above range, an effect of improving the hardness of the sintered body and an effect of suppressing defects are expected.

  The binder phase preferably has a lattice constant of 3.65 ° or more and 4.0 ° or less. When the lattice constant of the binder phase is 3.65 ° or more, C forms a solid solution and generates strain, so that high hardness can be maintained at a higher temperature. If the lattice constant of the binder phase is greater than 4.0 °, the strain will increase, and cracks may occur in the binder phase, resulting in loss. For this reason, when the lattice constant of the binder phase is in the above range, an effect of maintaining the high hardness of the sintered body at a higher temperature and an effect of suppressing the loss of the sintered body are expected.

  The WC preferably has an average particle diameter of 0.1 μm or more and 3 μm or less. When the average particle size is 0.1 μm or less, the toughness of the sintered body is reduced, and there is a possibility that defects may occur. On the other hand, when the average particle diameter is 5 μm or more, the strength of the sintered body is reduced, and there is a possibility that defects are easily generated. For this reason, when the average particle diameter of WC is in the above range, the effect of suppressing the loss of the sintered body is expected.

  It is preferable that the content of the binder phase in the sintered body is 2% by mass or more and less than 10% by mass. When the content of the binder phase is less than 2% by mass, the toughness of the sintered body is reduced, and there is a possibility that defects are easily generated. When the content of the binder phase is more than 10% by mass, the high-temperature hardness of the sintered body may be easily reduced. Therefore, when the content of the binder phase is in the above range, an effect of suppressing the loss of the sintered body and an effect of suppressing a decrease in the high-temperature hardness of the sintered body are expected.

The sintered body contains a hard phase (first hard phase and second hard phase), a binder phase (alloy powder) and Al ₂ O ₃ , and a hard phase (first hard phase and second hard phase). ), The volume content of the binder phase or Al ₂ O ₃ , the average particle diameter of WC (first hard phase), the equivalent circle diameter of Al ₂ O ₃ or the distance between the particles, and the composition of the binder phase are as follows. Can be confirmed as follows.

  First, a sample including an arbitrary cross section of the sintered body is prepared. For producing the cross section, a focused ion beam device, a cross section polisher device, or the like can be used. Next, the processed cross section is imaged at a magnification of 10000 by SEM (Scanning Electron Microscope) to obtain an electronic image for 10 fields of view. Next, element mapping is performed on a predetermined area (12 μm × 9 μm) in each electronic image using an attached EPMA (Electron Probe Micro-Analysis) or EDX (Energy Dispersive X-ray spectrum).

Based on the obtained elemental mapping, a region containing WC is a first hard phase, a region not containing WC, and containing a first metal (Ni, Co), a second metal (Al, W) and C. The region is a binder phase, and the region containing Al and O is Al ₂ O ₃ . This confirms that the sintered body contains the hard phase (the first hard phase and the second hard phase), the binder phase, and Al ₂ O ₃ . The composition of the binder phase and the ratio (volume%) of the binder phase in the sintered body are determined from the element mapping. Note that, depending on the sintering conditions, pores may be present in addition to the hard phase and the binder phase.

Further, using image analysis software (“Mac-View I”, manufactured by Mountech Co., Ltd.), the equivalent circle diameter of Al ₂ O ₃ scattered in the sintered body (diameter of a virtual circle having the same area as the particle area) And its standard deviation, and the average particle diameter of WC are calculated. In addition, each value is an average value of the results analyzed in 10 visual fields.

  The composition of the compounds constituting the hard phase (the first hard phase and the second hard phase), and the respective proportions (% by mass) of the WC (the first hard phase) and the compound are determined by pulverizing the sintered body, and illuminating the ICP. The content ratio of each element in the pulverized material can be determined by spectroscopic analysis, and the composition ratio of each component can be confirmed by trial calculation based on this.

  The content ratio of WC in the sintered body is relatively high, and therefore, there are many regions where WCs are adjacent to each other. Adjacent WCs can be distinguished from each other by the result of element mapping and the backscattered electron image obtained from the SEM image. This is because in the backscattered electron image, a color difference (shade) due to a difference in crystal orientation of each WC is observed.

<Manufacture of sintered body>
In one embodiment of the present disclosure, first, a bonding phase is prepared by using a first metal (Co, Ni) and a second metal (Al, W) as raw materials, by atomizing, arc melting, plasma processing, or the like.

  When preparing the binder phase powder, V, Ti, Nb, Ta, B, C, etc. may be added in addition to the first metal (Co, Ni) and the second metal (Al, W). .

The obtained binder phase is pulverized by, for example, a bead mill, a ball mill, a jet mill, or the like to obtain a binder phase powder. The average particle size of the binder phase powder is preferably 0.3 to 3 μm. Examples of the beads / balls used in the bead mill / ball mill include alumina / silicon nitride / hard metal alloy beads / balls having a particle size of 0.1 to 3 mm. Examples of the dispersion medium include ethanol, acetone, and liquid nitrogen. Is mentioned. The processing time by the bead mill / ball mill is, for example, 30 minutes to 200 hours. The slurry obtained by the bead mill / ball mill is dried, for example, in the atmosphere. By pulverizing over time and drying in the air, oxygen in the air is adsorbed, and at the time of sintering, the adsorbed oxygen reacts with Al in the binder phase to precipitate Al ₂ O ₃ . As another method, when pulverizing with a jet mill, a binder phase powder in which oxygen is adsorbed can also be obtained by using air as a pulverizing gas source and lengthening the pulverizing time. As described later, a sintered body in which Al ₂ O ₃ is dispersed can be obtained by directly adding Al ₂ O ₃ powder, but it is more preferable to precipitate Al ₂ O ₃ as in the present method. The particle diameter of Al ₂ O ₃ can be reduced, which is preferable.

  Next, the obtained binder phase powder is mixed with a separately prepared WC powder and, if necessary, a second hard phase powder using an attritor, a ball mill, a mortar or the like. At this time, appropriate C is added in consideration of the amount of C contained in the binder phase.

Mixing is performed in a state open to the atmosphere. Thereby, oxygen is taken into the mixture. The mixing time is preferably 6 to 20 hours so that oxygen is sufficiently and uniformly incorporated into the mixture for the purpose of uniformly dispersing alumina (Al ₂ O ₃ ) in the sintered body (hard material). .

Examples of the ball used in the ball mill include a ball made of alumina, silicon nitride, or a cemented carbide having a diameter of 3 mm. Examples of the dispersion medium include ethanol, acetone, and liquid nitrogen. The processing time is, for example, 3 to 20 hours. The mixed powder is obtained by, for example, drying the slurry obtained by mixing in the atmosphere. Upon mixing, the _Al 2 _{O 3} dispersed in the sintered body _Al 2 _{O 3} may be added to the fine powder (0.01 to 0.5 [mu] m).

The obtained mixed powder is put into, for example, a mold (Ta capsule or the like) made of cemented carbide and pressed to obtain a press-formed body. The pressure of the press is preferably 10 MPa to 16 GPa, for example, 100 MPa. Next, the compact is sintered in a vacuum. The sintering temperature is preferably 1000-1800 ° C. The sintering time is, for example, about one hour. Here, for example, by keeping the sintering time at 400 ° C. for 30 minutes to 5 hours, C contained in the compact is desorbed, and finally the mass of C contained in the sintered body Is controlled so that the ratio of the mass of O to (C / O ratio) becomes a desired value. As a result, the first hard phase (WC) and the binder phase are densely sintered, and fine Al ₂ O ₃ is precipitated in the sintered body, thereby improving the wear resistance at high temperatures. Can be formed.

Further, the cooling rate after sintering is, for example, 2 to 20 ° C./min. Thereby, a compound phase represented by the following formula is precipitated.
_{(Co, Ni) x (Al} , W) y C z
[Wherein (Co, Ni) is the first metal, (Al, W) is the second metal, and x, y and z are atomic weight ratios. ]
Thereafter, a sintered body (alloy) can be obtained by performing hot isostatic pressing (HIP) processing at 1400 ° C. and 1000 atm for 1 hour, for example.

  The average particle diameter of WC is preferably 0.1 to 10 μm, and the content of WC in the sintered body (hard material) is preferably 50 to 99% by volume. This is because if the particle size and the composition are in such ranges, the hardness of the obtained sintered body is expected to be higher. The average particle diameter of WC can be measured by the above-described method using element mapping and image analysis software.

  Further, the sintered body of the present embodiment may include unavoidable impurities (B, N, O, etc.) as long as the effects of the present disclosure are not impaired. Further, the sintered body of the present embodiment may include an abnormal layer called free carbon or η phase in its structure.

  Hereinafter, the present disclosure will be described in more detail with reference to examples, but the present disclosure is not limited thereto.

<Examples 1 to 50>
A metal powder having a composition of 42.5Co-40Ni-10W-7.5Al (atomic%) was mixed, and a bonding phase was produced by an atomizing method. (All the metal powders used in Examples 1 to 50 are the same.)
The obtained binder phase was pulverized by a bead mill using a carbide ball having a particle diameter of 1 μm. The obtained slurry was dried in the air to obtain a binder phase powder.

  The obtained binder phase powder, hard particles (first hard phase and second hard phase) having the compositions shown in Tables 1 and 2, and carbon powder were mixed with a cemented carbide ball having a diameter of 3.5 mm. Along with ethanol, the mixture was charged into an open-air attritor and mixed. The mixing time of the attritor is as shown in Tables 1 and 2. The obtained slurry was dried in the air to obtain a mixed powder.

  The mixed powder was filled in a cemented carbide mold and pressed at a pressure of 100 MPa to obtain a pressed compact.

The compact was sintered at 1450 ° C. for 1 hour under the sintering conditions shown in Tables 1 and 2. At this time, by setting the keeping time at 400 ° C. in a hydrogen atmosphere as shown in Tables 1 and 2, C contained in the compact was desorbed, and finally the C / O ratio contained in the sintered compact was reduced. It controlled so that it might become Table 3 and Table 4. Further, the cooling rate was adjusted as described in Tables 1 and 2. _{Thereby, (Co, Ni) x (} Al, W) y compound phase represented by _{C z} precipitated.

  Thereafter, a sintered body (hard material) was obtained by performing hot isostatic pressing (HIP) at 1400 ° C. and 1000 atm for 1 hour.

<Comparative Example 1>
At the time of mixing by the attritor, the oxidation of the mixture was suppressed by using a closed attritor. The slurry obtained after the mixing was dried in a nitrogen atmosphere. The sintering was performed at 1450 ° C. for 1 hour under vacuum. The mixing ratio of the binder phase and the conditions for preparation were as shown in Table 2. Except for this, a sintered body was obtained in the same manner as in the example.

<Comparative Examples 2-3>
The sintering was performed at 1450 ° C. for 1 hour in a vacuum. The mixing ratio of the binder phase and the conditions for preparation were as shown in Table 2. Except for this, a sintered body was obtained in the same manner as in the example.

<Comparative Example 4>
Instead of the metal powder of 42.5Co-40Ni-10W-7.5Al (atomic%), a metal Co powder having a particle diameter of 1.2 μm was used. The mixing ratio of the binder phase and the conditions for preparation were as shown in Table 2. Otherwise, a sintered body was obtained in the same manner as in Comparative Example 1.

(Production of cutting tools)
The sintered body (hard material) obtained in each of the above Examples and Comparative Examples was cut by wire electric discharge machining and finished to produce a cutting tool having a tip nose R of 0.8 mm.

<Evaluation of cutting tools>
For each of the cutting tools of each of the examples and comparative examples prepared above, a cutting test was performed on an NC lathe using Inconel (registered trademark) 718 (trade name, manufactured by Inconel) under the following cutting conditions. The wear amount (μm) and the boundary wear amount (μm) of the flank of the cutting tool after 0.2 km cutting were measured (see FIG. 1).
Cutting speed: 50m / min Cutting depth: 0.2mm
Feed amount: 0.1mm / rev
Cutting oil: Yes

<Evaluation of physical properties of sintered body>
The sintered body contains a hard phase (first hard phase and second hard phase), a binder phase (alloy powder) and Al ₂ O ₃ , and a hard phase (first hard phase and second hard phase); The volume content of the binder phase or Al ₂ O ₃ , the composition of the binder phase, and the like were measured in the same manner as in the method described in the above embodiment.

  The amount of oxygen and the amount of C in the sintered body were measured by crushing the sintered body and ICP emission spectroscopy.

  The lattice constant of the binder phase was specified by EDS analysis and an electron diffraction image in a restricted area of TEM observation. Note that JEM-2100F / Cs (manufactured by JEOL Ltd.) was used as the TEM. CESCOR (manufactured by CEOS) was used as a Cs collector. As an EDS machine, a JED2300 Series dry SD60GV detector (manufactured by JEOL Ltd.) was used. The TEM observation conditions were as follows: acceleration voltage: 200 kV, probe size: 0.13 nm.

  * 1 Boundary wear is a part where the wear increases due to a decrease in strength, chipping, or falling off of particles.

* 2 Cannot be measured because the cutting edge is missing.
* 3 Measurement is not possible because the cutting edge is missing.
* 4 Cannot be measured because the cutting edge is missing.
* 5 The test was stopped because the cutting edge was defective at the time of cutting 0.1 km.

  From the results shown in Tables 3 and 4, it can be seen that the cutting tools of Examples 1 to 50 of the present disclosure have improved wear resistance at high temperatures.

From the results of Examples 1 to 10, the binder phase is represented by the formula:
_{(Co, Ni) x (Al} , W) y C z
[Wherein (Co, Ni) is the first metal, (Al, W) is the second metal, and x, y and z are atomic weight ratios. ]
In the case of containing the compound phase represented by the formula, x is 73 atom% to 95 atom%, y is 4 atom% to 25 atom%, and z is 0.3 atom% to 15 atom%. It can be seen that the abrasion resistance at a high temperature is further improved when: When x is 75 atomic% or more and 93 atomic% or less, y is 5 atomic% or more and 20 atomic% or less, and z is 0.5 atomic% or more and 10 atomic% or less, the wear resistance at a high temperature is high. It can be seen that the properties are further improved. Further, when x is 80 atomic% or more and 90 atomic% or less, y is 6 atomic% or more and 15 atomic% or less, and z is 1 atomic% or more and 5 atomic% or less, the wear resistance at a high temperature is most improved. You can see that there is.

  From the results of Examples 11 and 12, even when the sintered body contains the second hard phase, when the first hard phase has a larger volume ratio than the second hard phase, the wear resistance at high temperatures is improved. You can see that From the results of Example 50, it can be seen that the case where the second hard phase is included has higher wear resistance at high temperatures than the case where the second hard phase is not included.

From the results of Examples 13 and 14, it is considered that if the content of Al ₂ O _{3 in} the sintered body is too small, the effect of improving the wear resistance at high temperatures may not be obtained. On the other hand, from the results of Examples 48 and 49, it is considered that if the content of Al ₂ O _{3 in} the sintered body is too large, the strength of the sintered body is reduced and defects are likely to occur.

From the results of Examples 15 to 17, by _Al 2 _{O 3} is fine, the effect to further improve the hardness of the sintered body is expected, on the other hand, when the _Al 2 _{O 3} is too fine, sintered It is considered that the toughness of the body is reduced and defects are likely to occur. On the other hand, from the results of Examples 43 to 47, it is considered that if the diameter of Al ₂ O ₃ is too large, the strength of the sintered body is reduced and defects are likely to occur.

From the results of Examples 18 and 19, it is considered that if the interparticle distance of Al ₂ O ₃ contained in the sintered body is too small, the degree of dispersion of the binder phase is biased and defects are likely to occur. On the other hand, from the results of Examples 41 and 42, it is considered that if the distance between the particles of Al ₂ O ₃ contained in the sintered body is too large, the strength of the sintered body is reduced and defects are likely to occur.

From the results of Examples 20 and 21 and the results of Examples 22 and 23, when the ratio of the mass of O to the mass of C contained in the sintered body (O / C ratio) is too small, If the oxygen content (alloy oxygen content) of the alloy is too small, it is considered that the wear resistance at high temperatures is reduced due to the small amount of Al ₂ O ₃ . On the other hand, from the results of Examples 37 and 38, and the results of Examples 39 and 40, when the oxygen content (alloy oxygen content) in the sintered body is too large, When the ratio of the mass of O to the mass of O (O / C ratio) is too large, it is considered that Al ₂ O ₃ aggregates and defects are likely to occur.

  From the results of Examples 24 and 25, it is considered that when the lattice constant of the binder phase is small, the abrasion resistance at high temperatures is reduced. On the other hand, from the results of Examples 35 and 36, it is considered that if the lattice constant of the binder phase is too large, the strain due to the solid solution of C increases, and cracks are generated in the binder phase to easily cause defects.

  From the results of Examples 26 and 27, it is considered that, when the average particle diameter of WC is small, the toughness of the sintered body is reduced, and defects are likely to occur. On the other hand, from the results of Examples 33 and 34, it is considered that if the average particle diameter of WC is too large, the strength of the sintered body is reduced and defects are likely to occur.

  From the results of Examples 28 to 32, if the content of the binder phase is too small, the toughness of the sintered body is reduced and defects are easily caused. On the other hand, if the content of the binder phase is too large, It is considered that the high-temperature hardness of the body tends to decrease.

  The embodiments and examples disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present disclosure is defined by the terms of the claims, rather than the embodiments described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

Claims (16)

A cutting tool including a sintered body including a first hard phase, a binder phase, and Al ₂ O ₃ ,
The first hard phase comprises WC;
The binder phase includes, as main components, a first metal composed of at least one selected from Co and Ni, and further includes a second metal composed of at least one selected from Al and W, and C. ,
The cutting tool, wherein the Al ₂ O ₃ is dispersed in the sintered body. The cutting tool according to claim 1, wherein the binder phase includes a compound phase represented by the following formula.
_{(Co, Ni) x (Al} , W) y C z
[Wherein (Co, Ni) is at least one selected from Co and Ni, (Al, W) is at least one selected from Al and W, and x, y and z are atomic weight ratios. It is. ]   The cutting tool according to claim 2, wherein the x is 0.73 or more and 0.95 or less, the y is 0.04 or more and 0.25 or less, and the z is 0.003 or more and 0.15 or less. .   The cutting tool according to claim 3, wherein the x is 0.75 or more and 0.93 or less, the y is 0.05 or more and 0.2 or less, and the z is 0.005 or more and 0.1 or less. .   The cutting tool according to claim 4, wherein the x is 0.8 or more and 0.9 or less, the y is 0.06 or more and 0.15 or less, and the z is 0.01 or more and 0.05 or less. The sintered body further includes a second hard phase,
The second hard phase is at least one metal selected from the group consisting of Ti, Zr, Hf, Nb, Ta, Cr, Mo and W, and at least one metal selected from the group consisting of nitrogen, carbon, boron and oxygen. A compound consisting of the above elements and a solid solution of the compound (excluding WC),
The cutting tool according to any one of claims 1 to 5, wherein the first hard phase has a larger volume ratio than the second hard phase. The cutting tool according to claim 1, wherein the Al ₂ O ₃ is contained in the sintered body in an amount of 1% by volume or more and 15% by volume or less. 8. The method according to claim 1, wherein the Al ₂ O ₃ has an average circle equivalent diameter of 0.1 μm or more and 2 μm or less and a standard deviation of 0.05 μm or more and 0.25 μm or less. 9. Cutting tool according to the item. The cutting tool according to claim 8, wherein the Al ₂ O ₃ has an average circle equivalent diameter of 0.2 μm or more and 1 μm or less, and a standard deviation of 0.05 μm or more and 0.15 μm or less. The cutting tool according to claim 9, wherein the Al ₂ O ₃ has an average circle equivalent diameter of 0.3 μm or more and 0.5 μm or less and a standard deviation of 0.05 μm or more and 0.1 μm or less. . 11. The Al ₂ O _{3 according} to claim 1, wherein an average value of a distance between particles is 1 μm or more and 3 μm or less, and a standard deviation thereof is 0.5 μm or more and 1.5 μm or less. 12. The cutting tool according to 1.   The cutting tool according to any one of claims 1 to 11, wherein a ratio of a mass of O to a mass of C contained in the sintered body is 0.015 or more and 0.061 or less.   The cutting tool according to any one of claims 1 to 12, wherein the content of oxygen in the sintered body is 0.1% by mass or more and 0.4% by mass or less.   The cutting tool according to any one of claims 1 to 13, wherein the bonding phase has a lattice constant of 3.65 ° or more and 4.0 ° or less.   The cutting tool according to any one of claims 1 to 14, wherein the WC has an average particle size of 0.1 µm or more and 3 µm or less.   The cutting tool according to any one of claims 1 to 15, wherein the content of the binder phase in the sintered body is 2% by mass or more and less than 10% by mass.

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