JP5835307B2 - Cemented carbide and surface-coated cutting tool using the same - Google Patents

Description

  The present invention relates to a cemented carbide and a surface-coated cutting tool using the same.

  Various work materials are cut using a cutting tool made of a cemented carbide mainly composed of tungsten carbide particles (hereinafter also referred to as “WC particles”). For example, Japanese Patent Application Laid-Open No. 2008-133508 (Patent Document 1) discloses a WC that exhibits a round shape with a polygonal shape and a corner having a radius of curvature of 50 nm or more when a cross-sectional structure is observed as a cemented carbide used for a cutting tool. A cemented carbide containing particles is disclosed.

JP 2008-133508 A

  In general, a cemented carbide is composed of WC particles (crystal grains) and a binder phase containing an element such as cobalt, and is manufactured by a powder metallurgy method. And it can be set as a cutting tool by performing predetermined processes, such as a blade edge process, to the sintered compact obtained by the powder metallurgy method.

  In recent years, it has become difficult to cut a work material in cutting work, and the working condition of the cutting tool has become extremely severe due to the complicated shape of the work material. Conventionally, for example, as disclosed in Patent Document 1, attention has been paid to the shape of WC particles and the like, and improvement in wear resistance and the like has been attempted. However, the improvement effect based on such a method has almost reached a saturation state, and the current situation is that it does not satisfy the level required in recent cutting work. In particular, the wear resistance and fracture resistance of a tool are in a trade-off relationship, and it is extremely difficult to improve the wear resistance while maintaining the fracture resistance.

  The present invention has been made in view of the above problems, and an object thereof is to provide a cemented carbide having excellent wear resistance while maintaining fracture resistance.

  A cemented carbide according to an embodiment of the present invention includes tungsten carbide particles and a binder phase having at least one element selected from the group consisting of cobalt, nickel, and iron, and the binder phase is 4% by mass or more and 7%. The proportion of tungsten carbide particles that are contained in a range of less than mass% and that have a crystal grain orientation difference of 0.75 ° or less among the tungsten carbide particles is 80% or more with respect to the total number of tungsten carbide particles. .

  The cemented carbide according to the embodiment of the present invention is excellent in wear resistance.

It is a schematic diagram which shows an example of the EBSD analysis result in the cemented carbide which concerns on one Embodiment of this invention. It is a schematic diagram which shows an example of the EBSD analysis result in the cemented carbide which concerns on a reference example.

[Description of Embodiment of Present Invention]
First, an outline of an embodiment of the present invention (hereinafter also referred to as “this embodiment”) will be described in the following (1) to (6).

  The present inventor conducted intensive research to solve the above problems, and in a cemented carbide structure containing a binder phase within a specific range, controls strain (strain) that WC particles (crystal grains) have inside. As a result, the inventors have obtained the knowledge that the wear resistance can be improved without lowering the fracture resistance, and have further completed research based on the knowledge to complete the present invention. That is, the cemented carbide and the surface-coated cutting tool according to the present embodiment have the following configuration.

  (1) The cemented carbide according to the present embodiment includes tungsten carbide particles and a binder phase having at least one element selected from the group consisting of cobalt (Co), nickel (Ni), and iron (Fe). Including the binder phase in a range of 4% by mass or more and less than 7% by mass.

  In the tungsten carbide particles, the proportion of the tungsten carbide particles having a crystal grain orientation difference of 0.75 ° or less is 80% or more with respect to the total number of tungsten carbide particles.

  As described above, a cemented carbide containing a binder phase in a range of 4% by mass or more and less than 7% by mass is advantageous in terms of hardness and wear resistance, but on the other hand, it tends to cause defects. The cemented carbide of the present embodiment contains WC particles having a crystal grain orientation difference of 0.75 ° or less as described above at a ratio of 80% or more with respect to all WC particles. According to the inventor's research, such WC particles have little distortion in the crystal and high thermal conductivity. And, when such WC particles are present in the alloy structure at a ratio of 80% or more, the thermal conductivity of the entire alloy structure is remarkably increased, and an increase in the cutting edge temperature during processing can be suppressed. Therefore, the cemented carbide of the present embodiment can suppress a decrease in material strength due to a temperature rise during processing. Therefore, the wear resistance can be improved without reducing the fracture resistance.

  (2) The average particle diameter of the tungsten carbide particles is preferably 0.4 μm or more and 3.0 μm or less. Propagation of cracks during cutting is suppressed when the average particle size is 0.4 μm or more, and sufficient hardness can be ensured when the average particle size is 3.0 μm or less. This improves the fracture resistance of the cemented carbide.

  (3) The cemented carbide has at least one element selected from the group consisting of Group 4 elements, Group 5 elements and Group 6 elements of the periodic table, carbon (C), nitrogen (N), oxygen ( O) and at least one element selected from the group consisting of boron (B) and a compound phase or solid solution phase containing at least one compound selected from the group consisting of boron and (B), and 0.1 mass of the compound phase or solid solution phase. It is preferable to contain in the range of 50 to 50 mass%.

  That is, the cemented carbide comprises (i) tungsten carbide particles, (ii) at least one element selected from the group consisting of Group 4 elements, Group 5 elements and Group 6 elements of the periodic table, carbon, A compound phase or solid solution phase containing one or more compounds composed of at least one element selected from the group consisting of nitrogen, oxygen and boron, (iii) a binder phase, and (iv) inevitable impurities. In addition, the compound phase or the solid solution phase is preferably contained in the range of 0.1% by mass to 50% by mass.

  By including such a compound phase or solid solution phase, the bonding strength of the cemented carbide structure is increased, and both wear resistance and fracture resistance can be made highly compatible.

  (4) The cemented carbide is preferably used for a cutting tool. The above cemented carbide is particularly useful as a cutting tool because it has excellent wear resistance. Specifically, the cutting tool indicates any one of a drill, an end mill, a milling cutting edge replacement cutting tip, a turning cutting edge replacement cutting tip, a metal saw, a gear cutting tool, a reamer, or a tap.

  (5) The present embodiment further relates to a surface-coated cutting tool using the above-mentioned cemented carbide, and the surface-coated cutting tool includes a base material and a coating formed on the base material. Is made of the above cemented carbide. Cutting performance can be further improved by forming a film on the surface of the cemented carbide having excellent wear resistance.

  (6) In the surface-coated cutting tool of the present embodiment, the coating is preferably formed by at least one of physical vapor deposition and chemical vapor deposition. By using the physical vapor deposition method, a film can be formed without reducing the strength of the substrate. Further, the adhesion strength between the substrate and the coating can be increased by using chemical vapor deposition.

[Details of the embodiment of the present invention]
Hereinafter, the cemented carbide and the surface-coated cutting tool according to the present embodiment will be described in more detail, but the present embodiment is not limited to these.

<Cemented carbide>
The cemented carbide according to the present embodiment includes WC particles and a binder phase having at least one element selected from the group consisting of Co, Ni, and Fe, and the binder phase is 4% by mass or more and less than 7% by mass. In the range of.

  Of the WC particles, the proportion of WC particles having a crystal grain orientation difference of 0.75 ° or less is 80% or more with respect to the total number of WC particles.

(Inside grain difference)
Here, the difference in crystal grain orientation is an index indicating the degree of strain of a crystal grain measured by an electron backscatter diffraction (EBSD) method. EBSD is a kind of electron beam diffraction in a scanning electron microscope (SEM), and the crystal orientation can be analyzed from the diffraction pattern.

  According to the inventor's research, cemented carbides with a proportion of WC particles (crystal grains) having an orientation difference within a crystal grain of 0.75 ° or less being 80% or more of the total WC particles are excellent in wear resistance. Excellent. Although the details of this reason are not clear, the thermal conductivity is improved by linking WC particles having high crystallinity, and the heat generated at the time of cutting is easily dissipated to the outside. Can be thought of as Note that the proportion of WC particles having an in-crystal grain orientation difference of 0.75 ° or less is preferably 85% or more, and more preferably 90% or more. This is because wear resistance tends to improve as the proportion of such WC particles increases.

(Measurement method of crystal grain orientation difference)
The crystal grain orientation difference can be measured using a commercially available SEM and EBSD apparatus. Specifically, the crystal grain orientation difference is measured as follows.

(Measurement sample preparation method)
The measurement sample can be produced by mirror-finishing any surface or cross section of the cemented carbide. Here, examples of the mirror finishing method include a method of polishing with diamond paste, a method using a focused ion beam (FIB) device, a method using a cross section polisher (CP) device, and the like. The processing method etc. which combined these can be mentioned.

(Measurement data analysis method)
Measurement of crystal grain orientation difference and data analysis by the EBSD method are performed as follows.

  [1] The orientation of all measurement points (pixels) within the measurement area is measured, a boundary where the orientation difference between adjacent pixels is 15 ° or more is regarded as a crystal grain boundary, and a region surrounded by this is defined as a crystal grain. To do.

  [2] An average value of orientation data of all measurement points (pixels) in the crystal grain is obtained, and the value is set as an “average crystal grain orientation” of the crystal grain.

  [3] The difference between the “average crystal grain orientation” and the crystal orientation at the analysis point having the largest different orientation in the crystal grain is referred to as “crystal grain orientation difference”.

  [4] The ratio of the number of particles having an “inside crystal grain orientation difference” of 0.75 ° or less to the number of particles in the measurement area is calculated.

  The data analysis as described above can be performed by, for example, EBSP analysis software “OIM Analysis” manufactured by TSL Solutions. At this time, the SEM magnification and the number of fields of view are appropriately adjusted so that the total number of particles in the measurement area is 300 or more.

  With reference to FIG. 1 and FIG. 2, the cemented carbide structure of the present embodiment will be described. FIG. 1 is a schematic diagram showing an example of an EBSD analysis result in the cemented carbide structure of the present embodiment. FIG. 2 is a schematic diagram showing an example of an EBSD analysis result in the cemented carbide structure of the reference example. 1 and FIG. 2 show a WC particle 1 having a crystal grain orientation difference of 0.75 ° or less, a WC particle 2 having a crystal grain orientation difference of 0.75 ° to 1.0 °, and a crystal grain orientation. The WC particles 3 having a difference of 1.0 ° or more and the binder phase 4 are illustrated by being hatched.

  As identified by the hatching in the figure, in FIG. 1, many WC particles 1 having a crystal grain orientation difference of 0.75 ° or less are distributed. On the other hand, in FIG. 2, there are few WC particles 1, many WC particles 2 having a crystal grain orientation difference of 0.75 ° to 1.0 °, and many WC particles 3 having a crystal grain orientation difference of 1.0 ° or more. It can be seen that they are distributed. In the structure of the reference example shown in FIG. 2, the presence of the WC particles 2 and WC particles 3 having different crystallinity from the WC particles 1 impedes heat conduction and tends to increase the cutting edge temperature during processing. On the other hand, in the present embodiment shown in FIG. 1, the ratio of the WC particles 1 having a crystal grain orientation difference of 0.75 ° or less is 80% or more. It can be connected, and heat generated during cutting can be efficiently dissipated. As a result, the cutting edge temperature during processing can be kept low, and damage due to an increase in cutting edge temperature can be suppressed. Therefore, it is possible to realize a cemented carbide excellent in wear resistance while maintaining fracture resistance even in a high hardness structure having a binder phase content of 4 mass% or more and less than 7 mass%.

(WC particles)
The WC particles in the present embodiment preferably have an average particle size of 0.4 μm or more and 3.0 μm or less. When the average particle size is less than 0.4 μm, cracks tend to propagate when cracks occur in the alloy structure, and when the average particle size exceeds 3.0 μm, the hardness of the alloy structure tends to decrease. . Here, the “average particle diameter” is measured as follows. First, the equivalent circle diameter for the region (area) identified as one crystal grain is obtained by the method described in [1] of the above “analysis method of measurement data”, and this equivalent circle diameter is used as the particle diameter of the WC particles. . Then, the particle diameter (equivalent circle diameter) is obtained for each WC particle in the visual field image, and the arithmetic average value thereof is defined as “average particle diameter”.

(Binder phase)
The binder phase of the present embodiment bonds WC particles within the alloy structure. The binder phase has at least one element selected from the group consisting of Co, Ni, and Fe, and is contained in the cemented carbide in a range of 4 mass% to less than 7 mass%. If the content of the binder phase is less than 4% by mass, the sinterability may be reduced, and as a result, the toughness of the alloy structure may be reduced. On the other hand, if the binder phase is 7% by mass or more, the thickness of the binder phase is reduced. May increase in hardness and decrease in hardness. The content of the binder phase is preferably 4.5% by mass or more and 6.5% by mass or less, and more preferably 5% by mass or more and 6% by mass or less.

(Compound phase or solid solution phase)
The cemented carbide according to the present embodiment includes Group 4 elements (Ti, Zr, Hf, etc.), Group 5 elements (V, Nb, Ta, etc.) and Group 6 elements (Cr, Mo, W, etc.) of the periodic table. A compound phase or a solid solution phase comprising at least one compound selected from the group consisting of at least one element selected from the group consisting of and at least one element selected from the group consisting of carbon, nitrogen, oxygen and boron Can be included.

  Here, the “compound phase or solid solution phase” indicates that a compound constituting such a phase may form a solid solution or may exist as an individual compound without forming a solid solution. By including such a compound phase or solid solution phase, the bonding strength of the cemented carbide structure is improved, and both wear resistance and fracture resistance can be made highly compatible.

  The content of the compound phase or solid solution phase is preferably in the range of 0.1% by mass to 50% by mass. A cemented carbide containing a compound phase or a solid solution phase in such a range is particularly excellent in damage resistance. The content of the compound phase or solid solution phase is more preferably 0.5% by mass or more and 30% by mass or less, and further preferably 1.0% by mass or more and 15% by mass or less.

Specific compounds constituting the compound phase or solid solution phase include, for example, TiC, TiCN, TaC, TaN, TaCN, NbC, ZrC, ZrN, ZrCN, Cr ₃ C _{2 and the} like. These compounds are particularly preferable from the viewpoint of damage resistance.

  In the present specification, when a compound is represented by a chemical formula as described above, it is intended to include all conventionally known atomic ratios unless the atomic ratio is particularly limited, and is not necessarily limited to a stoichiometric range. . For example, when simply describing “TiCN”, the atomic ratio of “Ti”, “C”, and “N” is not limited to 50:25:25, and also when “TiN” is described, “Ti” and “N” Is not limited to the case of 50:50, and any conventionally known atomic ratio is included.

(Other)
The cemented carbide according to the present embodiment may include an abnormal phase locally called free carbon in the structure in addition to the configuration described above. In addition, the cemented carbide may have a de-β layer, a Co-enriched layer, or a surface hardened layer formed on the surface thereof.

(Applications of cemented carbide)
Since the cemented carbide of the present embodiment has excellent wear resistance, the applicability to a cutting tool that requires wear resistance is particularly high. Examples of such cutting tools include drills, end mills, milling cutting edge exchangeable cutting tips, turning cutting edge exchangeable cutting tips, metal saws, gear cutting tools, reamers, or taps.

<Manufacturing method of cemented carbide>
(Preparation of WC powder)
As the WC powder used as a starting material, those subjected to high-temperature carbonization treatment are preferable. Here, the high-temperature carbonization treatment specifically indicates a treatment for carbonizing tungsten by holding at a temperature of 1900 ° C. to 2150 ° C. for 2 hours to 8 hours. Furthermore, it is preferable that the cooling conditions from a high temperature carbonization process are what cools from the carbonization temperature (1900 degreeC-2150 degreeC) to 1200 degreeC-1500 degreeC at the speed | rate of 2 degreeC / min-8 degreeC / mim. As a result, the difference in orientation within the crystal grains of the primary particles can be minimized.

(Mixing of cemented carbide materials)
The mixing of the WC powder and the other raw materials constituting the cemented carbide is preferably performed in a state where a strong impact is not applied to the WC particles. This is because there is a case where strain is applied to the WC particles by a strong impact and the orientation difference in the crystal grains increases.

  Here, as a mixing method in which a strong impact is not applied, for example, the following method can be exemplified. That is, a method in which the raw material powder mixture is stirred for a long time in a ball mill containing no grinding balls or a method in which the raw material powder mixture is stirred for a long time with a V-type mixer is preferred. Here, the stirring method is not particularly limited, and any method may be employed as long as it does not apply a strong impact. For example, a method using an impeller, a method using only a water flow, a method using these in combination, and the like can be exemplified.

  The cemented carbide of this embodiment is manufactured according to the following procedure, for example. First, WC powder that has undergone high-temperature carbonization treatment and other raw materials are put into a mixer (stirrer) together with a solvent such as water, ethanol, acetone, isopropyl alcohol, and stirred for a long time at a low speed. Next, the obtained mixture is dried and then formed into a predetermined shape. Then, by sintering this formed body, a cemented carbide having WC particles having a desired in-crystal grain orientation difference can be produced.

(Sintering)
In addition, it is preferable that sintering of the said molded object is performed at the temperature as low as possible to 1390 degreeC-1490 degreeC. This is because if the sintering is performed at a high temperature, crystal grain growth is promoted by the solid solution reprecipitation phenomenon, and the hardness of the cemented carbide is lowered and the intended performance may not be obtained.

Hereinafter, the surface-coated cutting tool using the cemented carbide described above will be described.
<Surface coated cutting tool>
The surface-coated cutting tool of this embodiment includes a base material and a coating film formed on the base material, and the base material is constituted by the cemented carbide of the present embodiment described above. By using the cemented carbide of this embodiment as a base material, a surface-coated cutting tool having excellent wear resistance can be obtained.

(Coating)
The coating of the present embodiment may be formed so as to cover the entire surface of the base material, or may be formed so as to cover only a part of the base material. Since it is in improving the characteristics (that is, improving the cutting performance), it is preferable to cover at least a part of the portion that contributes to the improvement of the cutting performance even when the whole surface is covered or a part thereof is covered. The configuration of the coating may be partially different.

  By covering the base material with the coating, various characteristics such as wear resistance, oxidation resistance, toughness of the cutting tool, and coloring property for identifying the used blade edge portion are improved.

  Such coatings include Group 4 elements (Ti, Zr, Hf, etc.), Group 5 elements (V, Nb, Ta, etc.), Group 6 elements (Cr, Mo, W, etc.), Al, and Si of the periodic table. It is preferable to include at least one layer selected from the group consisting of at least one element selected from the group consisting of or a compound of the element and at least one element selected from the group consisting of carbon, nitrogen, oxygen, and boron. .

Examples of such elements or compounds include TiCN, TiN, TiCNO, TiO ₂ , TiNO, TiB ₂ , TiBN, TiSiN, TiSiCN, TiAlN, TiAlCrN, TiAlSiN, TiAlSiCrN, AlCrN, AlCrCN, AlCrVN, TiAlBN, TiBCN, TiAlBCN , TiSiBCN, AlN, AlCN, Al 2 O 3, ZrN, ZrCN, ZrN, ZrO 2, HfC, HfN, HfCN, NbC, NbCN, NbN, Mo 2 C, WC, W 2 C, Cr, Al, Ti, Si , V and the like. These elements or compounds may be doped with a small amount of other elements. The Al ₂ O ₃ includes α-Al ₂ O ₃ , κ-Al ₂ O ₃ , γ-Al ₂ O _{3, and} amorphous ones.

(Method for forming film)
The coating film of this embodiment is preferably formed by at least one of a PVD method and a CVD method.

  As the PVD method, a conventionally known vacuum deposition method, sputtering method, or the like can be employed. Specific examples include magnetron sputtering, arc ion plating, holocathode, ion beam, electron beam, balanced magnetron sputtering, unbalanced magnetron sputtering, and dual magnetron sputtering. Can do. By forming the film by the PVD method, the film can be formed without reducing the strength of the substrate.

  As the CVD method, for example, a conventionally known plasma CVD method can be employed. By forming the film by the CVD method, the adhesion strength between the film and the substrate can be improved.

  When a plurality of layers are stacked by the CVD method, it is preferable that at least one of the plurality of layers is formed using an MT-CVD (Medium Temperature-CVD) method. The normal CVD method forms a film at about 1020 ° C. to 1030 ° C., whereas the MT-CVD method can be performed at a relatively low temperature of about 850 ° C. to 950 ° C. It is possible to reduce the damage to the substrate due to the above. Therefore, the layer formed by the MT-CVD method is preferably formed close to the substrate.

  The thickness of the coating (when formed with two or more layers, the total thickness) is preferably 1 μm or more and 30 μm or less, more preferably 2 μm or more and 20 μm or less, and further preferably 4 μm or more and 15 μm or less. is there. If the thickness is less than 1 μm, the effect of improving the wear resistance is not sufficiently exhibited. On the other hand, if the thickness exceeds 30 μm, no further improvement in various properties is observed, which is not economically advantageous. However, as long as economic efficiency is ignored, the thickness may be 30 μm or more. As a method for measuring the thickness of the coating, for example, the blade-tip-exchangeable cutting tip on which the coating is formed is cut, and the cross section is measured by SEM. The composition of the film is measured by an energy dispersive x-ray spectrometer (EDS).

<Method for manufacturing surface-coated cutting tool>
The surface-coated cutting tool of the present embodiment is manufactured by obtaining a base material made of a cemented carbide as described above, and performing various cutting edge processing such as honing treatment, and then forming a film on the base material. can do.

  In addition, you may give a compressive residual stress to this film after film formation. This is because the toughness of the coating is improved by applying compressive residual stress to the coating. The application of compressive residual stress is particularly effective for a film formed by the PVD method. The compressive residual stress can be introduced by, for example, a blast method, a brush method, a barrel method, an ion implantation method, or the like.

  Hereinafter, the present embodiment will be described in more detail using examples, but the present embodiment is not limited thereto.

<Example 1>
In the following manner, a surface-coated cutting tool (blade-replaceable cutting tip) No. 1 having a base material made of cemented carbide and a coating on the base material is prepared. 1-14 were produced.

  First, tungsten powder and carbon powder were carbonized by holding at 1950 ° C. for 5 hours, and then cooled to 1300 ° C. at a rate of 7 ° C./min to obtain WC powder. The average particle diameter (hereinafter also referred to as “FSSS (Fisher Sub Sieve Sizer value)”) of this WC powder by the Fisher method was 2.2 μm.

Cemented carbide containing WC powder, Co powder and Cr ₃ C ₂ powder so as to be Co (3.5% by mass), Cr ₃ C ₂ (1.0% by mass), and WC powder (remainder). Raw material powder was obtained. Let this cemented carbide raw material powder be raw material 1-A. The contents of the raw material 1-A are shown in Table 1.

  Subsequently, this raw material 1-A, liquid paraffin (2% by mass), and an ethanol solvent were stirred for 24 hours in a ball mill without a grinding ball to obtain a mixture. And this mixture was spray-dried and granulated powder was obtained.

Subsequently, the granulated powder was press-molded to obtain a sintered body by 1 hour sintered under 1 46 0 ° C. a vacuum atmosphere of 10Pa or less. This process of mixing / granulating / sintering is referred to as production method 1-1. The contents of production method 1-1 are shown in Table 2.

  Subsequently, SiC brush honing treatment is performed on the edge of the blade edge of the sintered body, and further, flat polishing is performed on the bottom surface of the blade tip replaceable tip to obtain a blade tip replaceable cutting tip shape (“CNMG120212N-EX”, Sumitomo Electric Hardmetal A base material of a surface-coated cutting tool having a product of Co., Ltd. was obtained.

  A film made of a TiAlN layer having a thickness of 4.0 μm was formed on the surface of the base material by an ion plating method which is a kind of PVD method. As described above, the surface-coated cutting tool No. 1 was obtained.

(Evaluation of WC particles)
This surface-coated cutting tool No. In the base material of 1, the ratio of WC particles having an in-crystal grain orientation difference of 0.75 ° or less and the average particle size (according to the EBSD method) were measured according to the method described above. The results are shown in Table 3.

  The surface-coated cutting tool No. 1 was changed in the same manner as described above except that the raw material and the method for producing the sintered body were changed as shown in Table 1 and Table 2 and were combined as shown in Table 3. 2-14 were obtained. Then, in the same manner as described above, the in-crystal grain orientation difference and the average grain size were evaluated. The results are shown in Table 3. In Table 3, tool no. Those marked with “*” correspond to the surface-coated cutting tool according to the example, and the others correspond to the comparative example.

<Evaluation>
Surface coated cutting tool No. The cutting performance of 1-14 was evaluated as follows.

(Evaluation of wear resistance and fracture resistance by turning Ni-base heat-resistant alloy)
The cutting edge replaceable cutting tip was set in a holder (model number “DCLNR2525”, manufactured by Sumitomo Electric Hardmetal Co., Ltd.), and the difficult-to-cut material was turned under the following cutting conditions. Then, when the flank wear amount (Vb) was 0.15 mm or more, or when the boundary portion defect was 0.30 mm or more, it was determined as the life, and the cutting time until reaching the life was evaluated. The results are shown in Table 3.

(Cutting conditions)
Work material: Ni-base heat-resistant alloy (Inconel 718 equivalent) φ200 round bar Cutting speed (Vc): 50 m / min
Feed (f): 0.15 mm / rev
Incision (ap): 0.35 mm
Coolant: Yes (wet cutting).

(Results and discussion)
(I) Example: Tool No. 2, 6, 7 and 11-13
Tool No. 2, 6, 7 and 11 to 13 were good because the cutting time until the service life was remarkably long as compared with other tools. The reason can be considered as follows. In the alloy structure, the proportion of WC particles having an in-crystal grain orientation difference of 0.75 ° or less is 80% or more, so that WC particles having high crystallinity can be connected to each other, and heat can be efficiently applied during cutting. Dissipates and keeps the cutting edge temperature low. Thereby, it is thought that the strength reduction of the tool material during processing is suppressed. Since the cutting edge temperature during processing is low, it can be considered that the progress of flank wear is suppressed and the tool life is improved.

(Ii) Comparative example: Tool No. 1
Tool No. No. 1 has a boundary defect of 0.30 mm or more after a cutting time of 2 minutes, even though the proportion of WC particles having a crystal grain orientation difference of 0.75 ° or less was as high as 91.2%. It was determined that it was a lifetime. This is because the tool no. In No. 1, since the amount of Co blended was as small as 3.5% by mass (less than 4.0% by mass), the sinterability was poor and the strength of the tool material was considered insufficient. Therefore, the content of the binder phase in the cemented carbide needs to be 4% by mass or more.

(Iii) Comparative example: Tool No. 3 and 4
Tool No. In both 3 and 4, the cutting time to the end of the life was short, and the life factor was due to the defect of the boundary. The reason for this result can be attributed to the fact that the proportion of WC particles having a crystal grain orientation difference of 0.75 ° or less is particularly low (less than 70%). That is, WC particles having low crystallinity are relatively increased in the alloy structure, and it is difficult for these WC particles to diffuse heat. Therefore, it is considered that the cutting edge temperature is increased at the time of cutting, and the material strength is decreased to cause defects. .

(Iv) Comparative example: Tool No. 5 and 8-10
Tool No. 5 and 8 to 10 all had a short life due to flank wear. In these tools, since the ratio of WC particles having an in-crystal grain orientation difference of 0.75 ° or less is low (both less than 80%), it is difficult for heat to escape, so the cutting edge temperature rises and the progress of flank wear is promoted. It is thought that.

(V) Comparative example: Tool No. 14
Tool No. No. 14 had a flank wear of 0.15 mm after 3 minutes of cutting despite the fact that the proportion of WC particles with a crystal grain orientation difference of 0.75 ° or less was 91.5%. The life was determined as above. This is because the tool no. In No. 14, the amount of Co blended was as large as 7.5% by mass (exceeding 7.0% by mass). Therefore, in the cutting where the tool temperature is likely to be high during cutting as in this cutting condition, the hardness of the base material is likely to decrease and escapes. It is thought that the progress of surface wear was accelerated.

<Example 2>
A cutting tool (blade-replaceable cutting tip) No. 1 made of cemented carbide as follows. 15-21 were produced.

  First, as shown in Table 4, a raw material 2-A was obtained in the same manner as in Example 1 except that the production conditions were changed.

  Next, according to the manufacturing method 2-1 shown in Table 5, each operation of mixing / granulation / sintering was performed to obtain a sintered body.

  Subsequently, SiC brush honing treatment is performed on the edge of the blade edge of the sintered body, and further, flat polishing is performed on the bottom surface of the blade tip replaceable tip to obtain a blade tip replaceable cutting tip shape (“CNMG120212N-EX”, Sumitomo Electric Hardmetal Cutting tool no. 15 was obtained.

(Evaluation of WC particles)
This cutting tool No. 15, the proportion of WC particles having a crystal grain orientation difference of 0.75 ° or less, and the average particle size (according to the EBSD method) were measured according to the method described above. The results are shown in Table 6.

  As shown in Tables 4 and 5, the cutting tool No. was changed in the same manner as above except that the raw material and the manufacturing method of the sintered body were changed and combined as shown in Table 6. 16-21 were obtained. Then, in the same manner as described above, the in-crystal grain orientation difference and the average grain size were evaluated. The results are shown in Table 6. In Table 6, the tool No. Those marked with “*” correspond to the cutting tool according to the example, and the others correspond to the comparative example.

<Evaluation>
Cutting tool No. The cutting performance of 15-21 was evaluated as follows.

(Evaluation of wear resistance and fracture resistance by turning Ti alloy)
The cutting edge replaceable cutting tip was set in a holder (model number “DCLNR2525”, manufactured by Sumitomo Electric Hardmetal Co., Ltd.), and the difficult-to-cut material was turned under the following cutting conditions. Then, the amount of flank wear and the amount of defects were measured using a comparator, and the cutting time until the amount of flank wear or the amount of defects was 0.30 mm or more was measured. The results are shown in Table 6.

(Cutting conditions)
Work material: Ti alloy (Ti-6Al-4V) φ250 round bar Cutting speed (Vc): 95 m / min
Feed (f): 0.22 mm / rev
Cutting depth (ap): 0.60 mm
Coolant: Yes (wet cutting).

(Results and discussion)
(I) Example: Tool No. 15
Tool No. No. 15 had a ratio of WC particles having an in-crystal grain orientation difference of 0.75 ° or less in the alloy structure of 80% or more, and was excellent in wear resistance. However, in the same way, in the alloy structure, a tool No. in which the proportion of WC particles having an in-crystal grain orientation difference of 0.75 ° or less is 80% or more is used. Compared to 16, 17, 19 and 20, the life was somewhat shorter. This is because the average particle size of the WC particles is as small as less than 0.4 μm, and it can be considered that cracks generated at the time of cutting easily propagate and cause defects early.

(Ii) Example: Tool No. 21
Tool No. In No. 21, the proportion of WC particles having an in-crystal grain orientation difference of 0.75 ° or less in the alloy structure was 80% or more, and the fracture resistance was excellent. However, in the same way, in the alloy structure, a tool No. in which the proportion of WC particles having an in-crystal grain orientation difference of 0.75 ° or less is 80% or more is used. Compared to 16, 17, 19 and 20, the life was somewhat shorter. The reason can be considered that since the average particle diameter of the WC particles is as large as 3.5 μm, the hardness is lowered and the flank wear easily proceeds.

(Iii) Example: Tool No. 16
Tool No. In No. 16, the proportion of WC particles having an in-crystal grain orientation difference of 0.75 ° or less in the alloy structure was 80% or more, and the wear resistance was excellent. However, in the same way, in the alloy structure, a tool No. in which the proportion of WC particles having an in-crystal grain orientation difference of 0.75 ° or less is 80% or more is used. Compared to 17, 19 and 20, the life was somewhat shorter. This is because the tool no. No. 16 has an average particle diameter of WC particles of 0.4 μm or more, and the hardness is high and the flank wear hardly progresses. Compared with 17, 19 and 20, it is presumed that the average particle diameter of WC particles is small and inferior to these from the viewpoint of suppressing the propagation of cracks, and easily lost.

(Iv) Comparative example: Tool No. 18
Tool No. No. 18 had a cutting time of 4 minutes until its lifetime, and its lifetime was particularly short compared to the others. This reason can be considered to be caused by a low ratio (less than 80%) of WC particles having an in-crystal grain orientation difference of 0.75 ° or less in the alloy structure. As described above, since such an alloy structure hardly dissipates heat, it can be considered that the cutting edge temperature is increased during cutting and the progress of flank wear is promoted.

  From the viewpoint of achieving both wear resistance and fracture resistance, the average particle size of the WC particles is preferably 0.4 μm or more and 3.0 μm or less, and 0.5 μm or more and 2.7 μm or less. It can be said that it is more preferable.

<Example 3>
In the following manner, a surface-coated cutting tool (blade-replaceable cutting tip) No. 1 having a base material made of cemented carbide and a coating on the base material is prepared. 22-28 were produced.

  First, as shown in Table 7, a raw material 3-A was obtained in the same manner as in Example 1 except that the production conditions were changed.

  Next, according to the manufacturing method 3-1 shown in Table 8, each operation of mixing / granulation / sintering was performed to obtain a sintered body.

  Subsequently, SiC brush honing treatment is performed on the edge of the blade edge of the sintered body, and further flat polishing is performed on the bottom surface of the blade tip replaceable tip to obtain a blade tip replaceable cutting tip shape (“CNMG120408N-GU”, Sumitomo Electric Hardmetal A base material of a surface-coated cutting tool having a product of Co., Ltd. was obtained.

A TiN layer (0.2 μm), an MT-TiCN layer (5.0 μm), a TiBN layer (0.4 μm), and an α-Al ₂ O ₃ layer (5.2 μm) are formed on the surface of the base material by CVD. And a TiN layer (0.2 μm) were laminated in this order (the value in parentheses indicates the thickness). Here, the MT-TiCN layer indicates a TiCN layer formed by the MT-CVD method. As described above, the surface-coated cutting tool No. 22 was obtained.

(Evaluation of WC particles)
This surface-coated cutting tool No. In 22 substrates, the proportion of WC particles having an in-crystal grain orientation difference of 0.75 ° or less and the average particle size (according to the EBSD method) were measured according to the method described above. The results are shown in Table 9.

  As shown in Table 7 and Table 8, the surface-coated cutting tool No. 1 was changed in the same manner as above except that the raw material and the method for producing the sintered body were changed and combined as shown in Table 9. 23-28 were obtained. Then, in the same manner as described above, the in-crystal grain orientation difference and the average grain size were evaluated. The results are shown in Table 9. In Table 9, the tool No. Those marked with “*” correspond to the surface-coated cutting tool according to the example, and the others correspond to the comparative example.

<Evaluation>
Surface coated cutting tool No. The cutting performance of 22-28 was evaluated as follows.

(Evaluation of wear resistance by turning of steel)
Set the cutting edge exchangeable cutting tip in the holder (model number “DCLNR2525”, manufactured by Sumitomo Electric Hardmetal Co., Ltd.) and turn the steel under the following cutting conditions, and the flank wear amount (Vb) is 0.20 mm or more. The cutting time (tool life) was measured. In addition, what was missing before the flank wear amount became 0.20 mm or more was determined to be the life at that time. The results are shown in Table 9.

(Cutting conditions)
Work Material: SCM435 φ350mm Round Bar Cutting Speed (Vc): 330m / min
Feed (f): 0.40 mm / rev
Incision (ap): 1.8mm
Coolant: Yes (wet cutting).

(Results and discussion)
(I) Example: Tool No. 25 and 26
Tool No. 25 and 26 are tool nos. The tool life was long compared with 22-24, and it was excellent in abrasion resistance. This is because the tool no. Nos. 25 and 26 have a large proportion of WC particles having an in-grain orientation difference of 0.75 ° or less in the alloy structure, so that heat is dissipated during cutting and the cutting edge temperature becomes low, and the progress of crater wear is suppressed. Can be considered.

(Ii) Comparative example: Tool No. 22-24
Tool No. Nos. 22 to 24 had a short life due to crater loss. The reason for this is that the ratio of WC particles having an in-crystal grain orientation difference of 0.75 ° or less in the alloy structure is low (both are less than 80%). It is thought that crater wear progressed with the rise, leading to defects.

(Iii) Comparative example: Tool No. 28
Tool No. In No. 28, Vb became 0.2 mm or more in a short time, and the defect was earliest. The reason for this is that the amount of Co blended is as large as 8% by mass (7% by mass or more). Therefore, in cutting where the tool temperature is likely to rise as in this cutting condition, the hardness tends to decrease and the flank wear progresses quickly. Conceivable.

(Iv) Example: Tool No. 27
Tool No. In the case of No. 27, Vb finally reached 0.2 mm and was determined to be a life, but the tool life was as long as 22 minutes. This result indicates that the tool No. manufactured under almost the same conditions. This is in contrast to 28. The reason why such a difference occurs is considered to be the difference in the amount of Co blended. That is, the tool No. In No. 28, the amount of Co blended was 8% by mass (7% by mass or more). In No. 27, it can be considered that the amount of Co is as small as 6% by mass (less than 7% by mass), the hardness is increased, and the progress of flank wear is suppressed.

<Example 4>
In the following manner, a surface-coated cutting tool (blade-replaceable cutting tip) No. 1 having a base material made of cemented carbide and a coating on the base material is prepared. 29-34 were produced.

  First, as shown in Table 10, a raw material 4-A was obtained in the same manner as in Example 1 except that the production conditions were changed.

  Next, according to the manufacturing method 4-1 shown in Table 11, each operation of mixing / granulation / sintering was performed to obtain a sintered body.

  Subsequently, SiC brush honing treatment is performed on the edge of the blade edge of the sintered body, and further flat polishing is performed on the bottom surface of the blade tip replaceable tip to obtain a blade tip replaceable cutting tip shape (“CNMG120408N-GU”, Sumitomo Electric Hardmetal A base material of a surface-coated cutting tool having a product of Co., Ltd. was obtained.

A TiN layer (0.2 μm), an MT-TiCN layer (5.0 μm), a TiBN layer (0.4 μm), and an α-Al ₂ O ₃ layer (5.2 μm) are formed on the surface of the base material by CVD. And a TiN layer (0.2 μm) were laminated in this order. As described above, the surface-coated cutting tool No. 29 was obtained.

(Evaluation of WC particles)
This surface-coated cutting tool No. In 29 substrates, the proportion of WC particles having an in-crystal grain orientation difference of 0.75 ° or less and the average particle size (according to the EBSD method) were measured according to the above-described method. The results are shown in Table 12.

  As shown in Table 10 and Table 11, the surface-coated cutting tool No. 1 was changed in the same manner as above except that the raw material and the manufacturing method of the sintered body were changed and combined as shown in Table 12. 30-34 were obtained. Then, in the same manner as described above, the in-crystal grain orientation difference and the average grain size were evaluated. The results are shown in Table 12. Tool No. 29 to 34 all correspond to the examples (in Table 12, “*” is attached to the tool No.).

<Evaluation>
Surface coated cutting tool No. The cutting performance of 29 to 34 was evaluated as follows.

(Evaluation of fracture resistance by intermittent cutting of steel)
The cutting edge replaceable cutting tip was set in a holder (model number “DCLNR2525”, manufactured by Sumitomo Electric Hardmetal Co., Ltd.), and intermittent cutting of steel was performed under the following cutting conditions. Then, assuming that N = 4, the average number of impacts by the slit portion of the work material up to the defect was measured. The results are shown in Table 12.

(Cutting conditions)
Work material: SCM435 round bar (with 4 slits on the round bar)
Cutting speed (Vc): 310 m / min
Feed (f): 0.21 mm / rev
Incision (ap): 1.7 mm
Coolant: Yes (wet cutting).

(Results and discussion)
(I) Example: Tool No. 29
Tool No. 29 is a tool no. Compared with 30-33, the average number of impacts was small. This is presumably because the average particle size of the WC particles was as small as 0.3 μm (less than 0.4 μm), and cracks generated during cutting were easy to propagate.

(Ii) Example: Tool No. 34
Tool No. 34 is also a tool no. Compared with 30-33, the average number of impacts was small. This is presumably because the average particle diameter of the WC particles was as large as 3.4 μm (exceeding 3.0 μm), the hardness was low, and the base material was deformed due to impact during intermittent cutting, leading to defects.

  From the above results, considering the fracture resistance, it can be said that the average particle diameter of the WC particles is preferably 0.4 μm or more and 3.0 μm or less.

  As mentioned above, it contains WC particles and a binder phase having at least one element selected from the group consisting of Co, Ni and Fe, the binder phase is contained in a range of 4 mass% to less than 7 mass%, and WC Of the particles, the proportion of WC particles having a crystal grain orientation difference of 0.75 ° or less is 80% or more based on the total number of WC particles. It was confirmed that it was superior in wear resistance compared to cemented carbide.

  Although the present embodiment and examples have been described as described above, it is also planned from the beginning to appropriately combine the configurations of the above-described embodiments and examples.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 WC particles having an orientation difference within the crystal grain of 0.75 ° or less 2 WC particles having an orientation difference within the crystal grain of 0.75 ° to 1.0 ° 3 An orientation difference within the crystal grain of 1.0 ° or more WC particles 4 bonded phase

Claims (5)

Tungsten carbide particles,
A binder phase having at least one element selected from the group consisting of cobalt, nickel and iron,
Containing the binder phase in a range of 4 mass% or more and less than 7 mass%,
Among the tungsten carbide particles, the proportion of tungsten carbide particles having a crystal grain orientation difference of 0.75 ° or less is 80% or more with respect to the total number of particles of the tungsten carbide particles.   The cemented carbide according to claim 1, wherein the tungsten carbide particles have an average particle size of 0.4 μm or more and 3.0 μm or less. The cemented carbide is at least one element selected from the group consisting of Group 4 elements, Group 5 elements and Group 6 elements in the periodic table, and at least selected from the group consisting of carbon, nitrogen, oxygen and boron. And further comprising a compound phase or a solid solution phase containing one or more compounds composed of one element.
The cemented carbide according to claim 1 or 2, wherein the compound phase or the solid solution phase is contained in a range of 0.1 mass% or more and 50 mass% or less.   The cemented carbide according to any one of claims 1 to 3, wherein the cemented carbide is used for a cutting tool. A substrate and a coating formed on the substrate;
The said base material is a surface coating cutting tool comprised with the cemented carbide alloy of any one of Claims 1-3.

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