JP2014083664A - Cutting tool and surface-coated cutting tool utilizing cubic crystal boron nitride based ultrahigh-pressure sintered body as tool base body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cutting tool and a coated cutting tool which utilizes a cBN based ultrahigh-pressure sintered body having excellent toughness as the tool base body and have excellent defect resistance.SOLUTION: A cubic boron nitride based ultra-high sintered body cutting tool utilizes a cBN based ultrahigh-pressure sintered body comprising cBN particles, a binder phase and TiBand WB phases as the tool base body. In a coated cutting tool, the average particle size of cBN particles is 0.5-3.5 μm and the content of the cBN particles is 40-75 vol.%. In the binder phase, fine TiBand WB phases of an average particle size of 50-500 nm are distributed in a dispersed form. The total amount of the TiBand WB phases produced in the sintered body is 5-15 vol.% in the binder phase. In the binder phase, 15-35 vol.% is one or both of Al nitride and oxide, and remaining components comprises at least one or more of Ti nitride, carbide, boride and carbonitride and unavoidable impurities. The binder phase meets the relationship: 0.5≤(amount of WB phase produced)/(amount of TiBphase produced)≤1.0.

Description

  The present invention relates to a cutting tool (hereinafter referred to as a cBN tool) made of a cubic boron nitride (hereinafter referred to as “cBN”)-based ultrahigh pressure sintered body (hereinafter referred to as a cBN sintered body) having excellent toughness.

  Conventionally, cBN sintered bodies have been known to have excellent durability, thermal stability, thermal conductivity, excellent impact resistance, and coefficient of friction, and have an affinity for iron-based materials. Since it is low, it is used as a cutting tool material for iron-based work materials such as steel and cast iron, taking advantage of these characteristics.

For example, as shown in Patent Document 1, as a cBN sintered body excellent in wear resistance, fracture resistance, and chipping resistance for high-speed continuous cutting of high hardness steel, chill cast iron, etc., a Ti-based compound is contained. The raw material powder is pulverized and mixed with a ball mill, and then blended and mixed with the cBN powder to produce a molded body. By sintering this, one kind of Ti carbide, nitride, carbonitride or Two or more kinds are used as a matrix, and in this matrix, cBN having an average particle size of 4 to 20 μm is less than 10 to 50% by volume, WC is 0.1 to 1.0% by volume of an average particle size of 0.2 μm or less, and the average particle size is 0.2 μm. CBN sintering in which _{3 to} 10% by volume of the following Al ₂ O _3, 3 to 7% by volume of AlN having an average particle size of 0.5 μm or less, and 1 to 5% by volume of TiB ₂ having an average particle size of 0.5 μm or less are uniformly dispersed. Proposed to get the body There.

Also, for example, as shown in Patent Document 2, after forming a compact from a raw material powder containing a Ti-based compound, crushing and pulverizing it, a mixture of cBN powder having a predetermined particle size and a predetermined amount is added to the slurry. The cBN-containing slurry is pulverized, mixed and dried to form a green compact, which is then sintered to obtain an XRD peak height of the (101) peak of TiB ₂ contained in the matrix phase of the sintered body. Has been proposed in which cBN is made to be smaller than 12% of the peak height of the (111) peak of cBN to improve fracture resistance and breakage resistance.

Further, for example, as shown in Patent Document 3, cBN having a volume average particle size of about 3 to 6 μm is about 60 to 80% by volume, the ceramic binder phase is about 40 to 20% by volume, and tungsten is about 3 to 15% by weight. In the cBN sintered body, about 20 to 60% by volume of the ceramic binder is composed of one or more of Group 4, Group 6 metal carbide, nitride or boride, and the remaining about 40 to 80 volume. % Is composed of one or more of aluminum carbide, nitride, boride or oxide, and the formation of the WB phase in the sintered body suppresses the formation of the TiB ₂ phase and lowers the fracture resistance. It has been proposed to improve the fracture resistance of the cBN sintered body by suppressing WB / TiB ₂ to less than 0.4 in terms of the XRD intensity ratio.

JP-A-8-81270 JP 2008-528413 A Japanese Patent Laid-Open No. 2004-160637

The cBN sintered bodies disclosed in Patent Documents 1 and 2 are intended to improve the wear resistance of the cBN sintered body by dispersing a high-hardness Ti boride (TiB ₂ ) phase in the binder phase. However, conventionally, since the generation size and generation form of the Ti boride phase dispersed and distributed in the binder phase cannot be controlled, a band-like film is formed at the interface between the cBN particles and the binder phase in the cBN sintered body. In some cases, a Ti boride phase is formed, or a Ti boride phase is formed as a large mass in the binder phase.
In such a case, due to a decrease in adhesion at the interface between the cBN particles and the binder phase, and due to the difference in the coefficient of thermal expansion, cracks are easily generated and propagated. It was a cause of lowering toughness.
In particular, when a cBN sintered body is used as a cutting tool, a high load, an impact, and the like act on the cBN sintered body during cutting, so that defects and breakage due to a decrease in toughness have been serious problems.
In addition, since the cBN sintered body shown in Patent Document 3 contains W in the sintered body, a Ti boride phase and a W boride phase are generated simultaneously during the sintering. The formation suppresses the formation of the Ti boride phase at the cBN particle-binding phase interface, and therefore the adhesion at the cBN particle-binding phase interface decreases, and this becomes the starting point of crack generation, thereby reducing the fracture resistance. There was a problem.
The present invention solves the above-mentioned problems. By dispersing fine Ti boride phase and W boride phase in a ceramic binder phase, the binder phase becomes tough and the toughness of the sintered body is improved. By improving the cBN tool made of this cBN sintered body, the cBN tool has excellent fracture resistance over a long period of use even when subjected to cutting conditions where high loads, impacts, etc. act. The purpose is to provide a tool.

In order to solve the above-mentioned problems, the present inventors have made a cBN tool made of a cBN sintered body with a Ti boride (hereinafter referred to as “TiB ₂ ”) phase and a W boride (hereinafter referred to as “boride”) contained in the binder phase. As a result of diligent research focusing on the generation amount of the phase (indicated by “WB”), the generation amount ratio, and the dispersion distribution form, the following knowledge was obtained.

Conventionally, when manufacturing a cBN sintered body, a raw material powder containing a Ti-based compound, a W-based compound and the like constituting an intermediate phase of the sintered body is pulverized, and then cBN powder is added and mixed and pulverized. A cBN sintered body was obtained by preparing a molded body and sintering it.
However, the present inventors, in the manufacturing process of the cBN sintered body, after mixing the raw material powder containing Ti-based compound and the like constituting the intermediate phase of the sintered body, prior to adding the cBN powder, Hexagonal boron nitride (hereinafter referred to as “hBN”) powder and W-based compound powder are added, mixed and pulverized, and then the obtained raw material powder and cBN powder are mixed and molded and sintered. When the, cBN sintered body obtained had a binding phase TiB ₂ phase massive during, no formation of WB phase, baked fine TiB ₂ phase is a hard material, WB phase is dispersed distributed in bond By forming a knot structure, the toughness of the cBN sintered body is improved. When a cBN sintered body having such a structure is used as a cBN tool, it is difficult for defects and breakage to occur, and for a long time. Exhibits excellent fracture resistance over the use of It is was found.

As a result of further investigation on the cause of such an improvement in toughness, the present inventors prior to adding the cBN powder to the mixed raw material powder containing the Ti-based compound constituting the intermediate phase of the sintered body. Then, by adding hexagonal boron nitride (hereinafter referred to as “hBN”) powder and W-based compound powder, mixing and grinding, fine hBN particles and fine W-based compound particles are present in the binder phase. Evenly distributed, and further mixed with cBN powder and sintered, fine hBN particles react with Ti metal component and fine W-based compound particles to become fine TiB ₂ phase and WB phase. As a result, it was found that a sintered structure in which fine TiB ₂ phase and WB phase are uniformly distributed is formed in the binder phase of the sintered cBN sintered body.
When a cBN sintered body having such a sintered structure is used as a cBN tool, even if a high load, impact, etc. are applied during cutting, cracks are generated and propagated by increasing the toughness of the binder phase. As a result, it was found that the fracture resistance is improved.

The present invention has been made based on the above findings,
“(1) Cubic boron nitride-based ultrahigh pressure using a cubic boron nitride-based ultrahigh pressure sintered body containing cubic boron nitride particles, a binder phase, a Ti boride phase, and a W boride phase as a tool substrate In the sintered body cutting tool, the cubic boron nitride particles have an average particle diameter of 0.5 to 3.5 μm, the content thereof is 40 to 75% by volume, and the average particle diameter is in the binder phase. A fine Ti boride phase of 50 to 500 nm and a fine W boride phase having an average particle size of 50 to 500 nm are dispersed and distributed, and the sum of the amount of Ti boride phase and W boride phase produced is the binding phase. 5 to 15% by volume in the binder phase, and 15 to 35% by volume in the binder phase is at least one of Al nitride and oxide, and the other is Ti nitride, carbide, boride, Or at least one of carbonitrides and inevitable impurities, and
0.5 ≦ (production amount of W boride phase) / (production amount of Ti boride phase) ≦ 1.0
A cubic boron nitride-based ultrahigh-pressure sintered body cutting tool characterized by using a cubic boron nitride-based ultrahigh-pressure sintered body satisfying the above relationship as a tool base.
(2) The surface-coated cubic boron nitride according to (1), wherein a hard coating layer is formed by vapor deposition on the surface of the tool base. Super high pressure sintered body cutting tool. "
It is characterized by.

  The present invention will be described below.

<CBN particles>
In this invention, the average particle diameter of cBN particles in the cBN sintered body is 0.5 to 3.5 μm, and the content thereof is 40 to 75% by volume.
When the average particle size of the cBN particles is less than 0.5 μm, for example, when subjected to high-speed cutting such as high-hardness steel, sufficient fracture resistance cannot be exhibited over a long period of use. If the average particle size of the particles exceeds 3.5 μm, the accuracy of the finished surface may be lowered. Therefore, the average particle size of the cBN particles is determined to be 0.5 to 3.5 μm.
In addition, when the content ratio of cBN is less than 40% by volume, the hardness as a cBN tool is not sufficient, and the progress of wear increases in high-speed cutting such as high-hardness steel, while the content ratio of cBN is When it exceeds 75% by volume, the content ratio of the binder phase is relatively reduced, and at the same time, the amount of TiB ₂ phase and WB phase dispersed and distributed in the binder phase is also reduced, and the effect of improving the toughness of the cBN sintered body is reduced. Therefore, the content ratio of the cBN particles in the cBN sintered body was determined to be 40 to 75% by volume.

<Al nitride and oxide>
In the present invention, at least one of AlN and Al ₂ O ₃ contained in the cBN sintered body is 15 to 35% by volume in the binder phase. The capacity% in the binder phase at this time represents a capacity ratio with the sum of AlN and Al ₂ O ₃ when the total capacity of the components excluding the cBN particles in the cBN sintered body is defined as 100.
If one or more of AlN and Al ₂ O ₃ is less than 15% by volume in the binder phase, the sinterability deteriorates, so that the binder phase cannot hold cBN particles, and the strength of the cBN sintered body is high. descend. On the other hand, when one or more of AlN and Al ₂ O ₃ exceeds 35% by volume in the binder phase, the amount of AlN and Al ₂ O ₃ generated in the interface between the cBN particles and the binder phase and in the binder phase increases. Since the toughness of the sintered body is reduced and cracks occur at an early stage starting from low hardness AlN and Al ₂ O ₃ during high-speed cutting of high hardness steel, one or more of AlN and Al ₂ O ₃ The content ratio in the binder phase was determined to be 15 to 35% by volume.

<TiB ₂ phase, WB phase>
The TiB ₂ phase and WB phase dispersed and distributed in the binder phase of the cBN sintered body are included in the raw material powder for forming the binder phase as described in the method for producing a cBN sintered body of the present invention (described later). In order to increase the reactivity of Ti compound (for example, TiAl, TiAl ₃ , Ti ₃ Al, TiN, TiCN, etc.) powder, W compound (for example, WC, etc.) powder and fine hBN powder. For this, it is desirable that the Ti compound powder, the W compound powder and the hBN powder are all finely divided by mixing and pulverization.
However, when the average particle size of the TiB ₂ phase and the WB phase in the binder phase is micronized to be less than 50 nm, contamination of impurities such as oxygen and moisture from the hBN powder increases. On the other hand, there is a possibility that the toughness is lowered. On the other hand, if the average particle size of the TiB ₂ phase and the WB phase in the binder phase is more than 500 nm without much pulverization, the coarse TiB ₂ phase As a result, a coarse WB phase is formed. Further, unreacted hBN remains in the central portion of the TiB ₂ phase, and unreacted W compound remains in the central portion of the WB phase. In addition to causing cracks, the average particle diameters of the TiB ₂ phase and the WB phase dispersed and distributed in the binder phase of the cBN sintered body must be 50 to 500 nm, respectively.

In the present invention, a preferred ratio of the ratio of the TiB ₂ phase generation amount and the WB phase generation amount (= (WB phase generation amount) / (TiB ₂ phase generation amount)) is 0.5 to 1.0. A more preferable ratio is 0.8 to 1.0. This is because when the ratio of the amount of TiB ₂ phase produced and the amount of WB phase produced is less than 0.5, the amount of TiB ₂ phase produced is increased, and a massive TiB ₂ phase is produced. When the crack is likely to occur as a starting point, the expected tool life may not be obtained. On the other hand, when the ratio of the TiB ₂ phase generation amount and the WB phase generation amount exceeds 1.0, Since the brittleness of the binder phase increases due to an increase in the hard WB phase in the binder phase, the toughness of the cBN sintered body decreases, so the ratio of the amount of TiB ₂ phase produced and the amount of WB phase produced is It was determined to be 0.5 to 1.0.

FIG. 1 shows the dispersion distribution of TiB ₂ phase and WB phase in a conventional cBN sintered body.
1A is a secondary electron image, FIG. 1B is a mapping image of B, FIG. 1C is a mapping image of Ti, and FIG. 1D is a mapping image of W. The overlapping portion of (b) and (c) of 1 is a TiB ₂ phase generation region, and the overlapping portion of (b) and (d) is a WB phase generation region.

FIG. 2 shows the dispersion distribution of the TiB ₂ phase and the WB phase in the cBN sintered body of the present invention.
2A is a secondary electron image, FIG. 2B is a B mapping image, FIG. 2C is a Ti mapping image, and FIG. 2D is a W mapping image. 2B, the generation region of TiB ₂ phase that is an overlapping portion of (b) and (c) in FIG. 2, and the generation region of WB phase that is an overlapping portion of (b) and (d), In the cBN sintered body of the present invention shown in FIG. 2, it can be seen that the TiB ₂ phase and the WB phase are dispersed and distributed in the binder phase.

FIG. 3 schematically shows the sintered structure of the cBN sintered body of the present invention.
In FIG. 3, the TiB ₂ phase and the WB phase are dispersed and distributed as a fine structure (average particle diameter is 50 to 500 nm) in the binder phase of the cBN sintered body.
In the present invention, such TiB ₂ phase, by defining the state of dispersion of the WB-phase, hard TiB ₂ phase, improving the toughness of the binder phase by dispersion of the WB phase, further, fine dispersion phase (TiB ₂ Toughness can be improved by suppressing grain growth of other binder phase components (for example, TiN, TiC, TiCN, etc.) due to the presence of the phase.

Moreover, in this invention, the sum of the production amount of the TiB ₂ phase and the WB phase needs to be 5 to 15% by volume in the binder phase. The volume% in the binder phase at this time represents the volume ratio with respect to the sum of the amounts of TiB ₂ phase and WB phase generated when the total capacity of the components excluding cBN particles in the cBN sintered body is defined as 100. ing.
When the sum of the amount of TiB ₂ phase and WB phase generated is less than 5% by volume in the binder phase, the amount of TiB ₂ phase and WB phase dispersed and distributed in the binder phase is small. On the other hand, when the sum of the generation amounts of TiB ₂ phase and WB phase exceeds 15% by volume in the binder phase, hard TiB ₂ phase and WB phase increase in the binder phase. As a result, the brittleness of the binder phase is increased, so that the toughness of the cBN sintered body is lowered.
Therefore, according to the present invention, the sum of the amount of TiB ₂ phase and WB phase generated needs to be 5 to 15% by volume in the binder phase. In such a case, the toughness of the cBN sintered body is not improved. Thus, when this cBN sintered body is used as a cBN tool, it is possible to provide a cBN tool that has excellent fracture resistance and exhibits excellent cutting performance over a long period of use.

<Method for producing cBN sintered body>
An example of a procedure for producing a cBN sintered body having excellent toughness according to the present invention will be described below.
(A) First, raw material powders for components constituting the binder phase are prepared.
As the raw material powder, Ti compound powder (for example, TiN powder, TiC powder, TiCN powder, TiAl powder, TiAl ₃ powder, Ti ₂ AlN powder, Ti ₃ Al powder, Ti ₄ Al ₂ C ₂ powder, etc.) is prepared, Alternatively, in addition to this, conventionally known binder phase forming raw material powders (Al powder, Al ₂ O ₃ powder, AlN powder, etc.) can be further added and contained.
(B) These raw material powders are filled together with, for example, a WC cemented carbide ball and acetone in a ball mill lined with cemented carbide, capped and mixed by a rotating ball mill.
(C) Next, hBN powder having an average particle diameter of 1 to 5 μm was added so as to be about 0.8 to about 7.0 wt% with respect to the total powder, and an average particle diameter of 0.5 to 3 μm was added. Add about 1.5 to about 18.0% by weight of WC powder to the total powder, grind and mix in the same ball mill for 24 to 72 hours, and grind the hBN powder into fine hBN particles of 500 nm or less In addition, the WC powder is pulverized into fine WC of 500 nm or less and uniformly dispersed in the binder phase.
(D) Next, to the pulverized and mixed hBN powder and raw material powder for forming the binder phase, cBN powder having an average particle size of 0.5 to 3.5 μm is added, and further, for 24 hours in a ball mill. Mix.
(E) Next, the obtained sintered body raw material powder is molded at a predetermined pressure to produce a molded body, and this is temporarily sintered at 900 to 1300 ° C. in a vacuum atmosphere at a pressure of 10 ⁻⁴ Pa or less. Thereafter, the cBN sintered body of the present invention is prepared by charging in an ultrahigh pressure sintering apparatus and sintering at a predetermined temperature within a range of pressure: 5 GPa and temperature: 1200 to 1400 ° C.

In particular, the present invention is characterized by the above-mentioned step (c). By providing this step (c) to produce a cBN sintered body, a fine TiB ₂ phase and a WB phase are formed in the binder phase. It can be distributed and distributed, thereby improving the toughness of the cBN sintered body.
Incidentally, TiB ₂ phase, the average particle size of the WB phase (50 to 500 nm), TiB ₂ phase, the total generation amount of WB phase (volume%), and the ratio of the amount of the amount and WB phase of TiB ₂ phase ( = (Production amount of WB phase) / (Production amount of TiB ₂ phase)) can be adjusted mainly by the addition amount of hBN, the addition amount of W-based compound powder, and pulverization / mixing conditions in the above step (c). it can.

<CBN tool>
The cBN-based ultrahigh-pressure sintered body cutting tool using a cBN sintered body with excellent toughness as a tool base according to the present invention has excellent fracture resistance even in high-speed cutting of high-hardness steel, for example, for long-term use. Excellent cutting performance over time.
Further, the cBN sintered body of the present invention is used as a tool base, and on this, for example, one or two of a TiN layer and a composite nitride layer of Ti and Al, or even these layers are alternately arranged. The surface-coated cBN-based ultra-high pressure sintered cutting tool formed by depositing a hard coating layer consisting of multiple layers laminated on the surface by physical vapor deposition, for example, has excellent fracture resistance even in high-speed cutting of high-hardness steel. Demonstrate.

As described above, in the cBN tool of the present invention, in particular, by defining the TiB ₂ phase and the average particle size of the WB phase, the generation amount, and the generation ratio in the binder phase of the cBN sintered body, cBN excellent in toughness A sintered body can be obtained, and this cBN tool (cBN-based ultra-high-pressure sintered body cutting tool, surface-coated cBN-based ultra-high-pressure sintered body cutting tool) has excellent fracture resistance even in high-speed cutting of high-hardness steel. Show excellent cutting performance over a long period of use.

The dispersion distribution situation of the TiB ₂ phase in the conventional cBN sintered body is shown, (a) is a secondary electron image, (b) is a mapping image of B element by Auger electron spectroscopy analysis, (c) Is a mapping image of Ti element by Auger electron spectroscopy, and (d) is a mapping image of W element by Auger electron spectroscopy. The dispersion distribution situation of the TiB ₂ phase in the cBN sintered body of the present invention is shown, (a) is a secondary electron image, (b) is a mapping image of B element by Auger electron spectroscopy analysis, (c ) Is a mapping image of Ti element by Auger electron spectroscopy, and (d) is a mapping image of W element by Auger electron spectroscopy. The sintered structure of the cBN sintered body of the present invention is shown as a schematic diagram.

  Hereinafter, the present invention will be described based on examples.

(A) First, as shown in Table 1, raw material powders comprising predetermined components and blending ratios constituting the binder phase of the sintered body were prepared.
(B) Next, the raw material powder was filled in a ball mill lined with cemented carbide together with cemented carbide balls and acetone, capped, and then ground and mixed by a rotating ball mill.
(C) Next, the hBN powder and WC powder having the average particle diameter shown in Table 2 were added and contained so as to have the addition ratio shown in Table 2 with respect to the total powder weight. Grinding and mixing were performed for the time indicated in 2.
(D) Next, with respect to the hBN powder and the binder phase forming raw material powder that were pulverized and mixed, the cBN powder having the average particle diameter shown in Table 2 was also added in the ratio shown in Table 2 with respect to the total powder weight. In the same manner, the mixture was mixed for 24 hours in a ball mill.
(E) Next, the obtained sintered body raw material powder was press-molded at a molding pressure of 100 MPa to a size of diameter: 50 mm × thickness: 1.5 mm, and then this molded body was ^subjected to pressure: 10 ⁻⁴ Pa or less. In a vacuum atmosphere, it is preliminarily sintered while being held at a predetermined temperature in the range of 900 to 1300 ° C., and then charged into an ultra-high pressure sintering apparatus, pressure: 5 GPa, temperature: in the range of 1200 to 1400 ° C. By sintering at a predetermined temperature, cBN sintered bodies 1 to 12 of the present invention (referred to as inventive products 1 to 12) were produced.

  For comparison, the cBN sintered bodies 1 to 12 (comparative examples) are the same as the products 1 to 12 of the present invention or the method in which the hBN powder or WC powder having a predetermined average particle diameter is not added in the step (c). Comparative products 1 to 12) were prepared.

About the present invention products 1-12 and the comparative products 1-12 obtained above, the average particle size and production amount of the TiB ₂ phase in the binder phase, and the average particle size and production amount of the WB phase in the binder phase, The ratio value of (WB phase generation amount in the binder phase) / (TiB _two phase generation amount in the binder phase) was determined.
For the cBN particles, the average particle size and the content ratio were also measured. The content ratios of Al nitrides and oxides were also measured.

A method for measuring the average particle size of the TiB _two- phase is shown below.
In order to measure the average particle diameter of the TiB ₂ phase, the observation field of only the binding phase of the cBN sintered body was analyzed by Auger electron spectroscopy. Thereafter, the contrast intensity of the Ti element mapping image by Auger electron spectroscopy is converted to RGB Blue, the contrast intensity of the B element mapping image is converted to RGB Red, and they are synthesized by image processing. By analyzing the composite image and setting the RGB threshold values to R: 30-255, G: 0, B: 30-255 (threshold range: 0-255) and binarizing, all TiB in the screen Extract _two phases. The longest diameter of the extracted TiB ₂ phase particles was defined as the particle size of the particles, and the average value thereof was defined as the average particle size of TiB ₂ .
The method for measuring the amount of TiB ₂ phase produced is shown below.
After extracting the TiB ₂ phase, the total area is calculated by image analysis, the area ratio is calculated by dividing by the total area of the image, the area ratio is regarded as volume%, and the TiB ₂ phase in the binder phase The production amount of was measured.
With respect to the above three items, the average value of the values obtained by processing the five fields of view of each 100,000-magnification image of Auger electron spectroscopic analysis by the above method was used as the measurement result.

The measurement of the average particle size of the WB phase and the measurement of the production amount were also performed by the same method as the measurement related to the TiB ₂ phase.
That is, the observation field only of the binder phase of the cBN sintered body is analyzed by Auger electron spectroscopy, the contrast intensity of the W element mapping image is converted to RGB Blue, and the contrast intensity of the B element mapping image is converted to RGB Red. And synthesized by image processing. By analyzing the composite image and setting the RGB threshold values to R: 30 to 255, G: 0, B: 30 to 255 (threshold range: 0 to 255), and binarizing, all WB in the screen Extract the phase. The longest diameter of the extracted WB phase particles was defined as the particle diameter of the particles, and the average value thereof was defined as the average particle diameter of WB.
The measurement of the amount of WB phase generated is that after extracting the WB phase, the total area is calculated by image analysis, and the area ratio is calculated by dividing the total area by the image area. The amount of WB phase produced in the binder phase was measured.
With respect to the above three items, the average value of the values obtained by processing the five fields of view of each 100,000-magnification image of Auger electron spectroscopic analysis by the above method was used as the measurement result.
Incidentally, the value of WB phase above bonding phase ₂ phase product weight and the binder phase of TiB in obtained in (WB phase generation amount of binder phase) / (TiB ₂ phase production of binder phase) Calculated from the amount produced.

Next, the measuring method of the average particle diameter of cBN particles is shown below.
From the secondary electron image observed with a scanning electron microscope, cBN particles were extracted by image processing, the longest diameter of the cBN particles was defined as the particle diameter of the particles, and the average value thereof was defined as the average particle diameter of the cBN particles.
The measuring method of the content rate of cBN particle | grains is shown below.
After extracting the cBN particles, the area ratio is calculated by dividing the value of the total area calculated by image analysis by the total area of the image, so that the area ratio is regarded as volume%, and the content ratio of the cBN particles is It was measured.
With respect to the above two items, the average value of the values obtained by processing each of the three fields of view of the 5,000 times and 10,000 times images of the scanning electron microscope by the above method was used as the measurement result.
Table 3 shows each measurement result.

A method for measuring the content of Al nitride and oxide is shown below.
First, the cBN sintered body was analyzed using an X-ray diffractometer. A CuKα radiation source having an X-ray wavelength of 1.54 nm was used as the X-ray source. As a result of X-ray diffraction, it was confirmed that there were only AlN and Al ₂ O ₃ peaks as Al compounds, and then bonding of cBN sintered bodies was performed in order to measure the content of Al nitride and oxide. Analyzing the phase-only observation field by Auger electron spectroscopy, and from the mapping image of Al element, the total area of the area where Al element is detected by image analysis is divided by the total area of the area and the area ratio The area ratio was regarded as volume%, and the content ratio of Al nitride and oxide was measured.
The average value of the values obtained by processing the five fields of view of the 20,000-fold image of the 1 Auger electron spectroscopic analysis by the above method was used as the measurement result.

Next, the inventive products 1 to 12 and comparative products 1 to 12 produced above were cut into predetermined dimensions with a wire electric discharge machine, Co: 5 mass%, TaC: 5 mass%, WC: remaining composition and Ag having a composition consisting of Cu: 26%, Ti: 5%, and Ag: remaining in the brazed part (corner part) of the insert body made of WC-base cemented carbide having an ISO standard CNGA120408 insert shape. A cBN-based ultrahigh-pressure sintered cutting tool (referred to as a chip of the present invention) of the present invention having an insert shape conforming to ISO standard CNGA120408 by brazing using an alloy brazing material, polishing upper and lower surfaces and outer periphery, and honing treatment. ˜12, cBN-based ultra-high pressure sintered body cutting tools (referred to as comparative tips) 1 to 12 of Comparative Examples were produced.
In addition, about this invention chip | tip 1,5,7,9 and comparative chip | tip 1,5,7,9, the hard coating layer shown in Table 4 is further shown by Table 4 by physical vapor deposition. By forming the coating with a thickness, the surface-coated cBN-based ultrahigh-pressure sintered body cutting tool (referred to as the present-coated chip) 1, 5, 7, 9 of the present invention, and the surface-coated cBN-based ultrahigh-pressure sintered body of the comparative example are cut. Tools (referred to as comparative coated tips) 1, 5, 7, 9 were manufactured.

Next, a cutting test is performed under the following cutting conditions on the above-described chips 1 to 6 of the present invention, the chips 1 and 5 of the present invention, the comparative chips 1 to 6 and the chips 1 and 5 of comparison, The tool life (sec) was measured.
<Cutting conditions>
Work material: Carburized and hardened steel (JIS / SCM415, hardness: HRC62) in the longitudinal direction with one equally spaced round bar,
Cutting speed: 170 m / min,
Cutting depth: 0.2mm,
Feed: 0.1mm / rev
Dry high-speed cutting test of high hardness steel under the conditions of
The time (sec) when the cutting edge of each chip was lost was defined as the tool life.
Table 5 shows the measurement results of the cutting test.

  From the results shown in Table 5, the tool life of the present invention chip and the present invention coated chip was prolonged as compared with the comparative chip and the comparative coated chip without causing sudden chipping of the cutting edge. It can be seen that the inventive chip and the inventive coated chip have improved toughness compared to the comparative chip and the comparative coated chip.

Next, a cutting test is carried out under the following cutting conditions for the above-described inventive chips 7 to 12, inventive coated chips 7 and 9 comparative chips 7 to 12, and comparative coated chips 7 and 9. The lifetime (sec) was measured.
<Cutting conditions>
Work material: Eight longitudinally spaced round bars of carburized and hardened steel (JIS SCM415, hardness: HRC62) in the longitudinal direction,
Cutting speed: 150 m / min,
Cutting depth: 0.2mm,
Feed: 0.2mm / rev
Dry high-speed cutting test of high hardness steel under the conditions of
The time (sec) when the cutting edge of each chip was lost was defined as the tool life.
Table 6 shows the measurement results of the cutting test.

  From the results shown in Table 6, since the chip of the present invention and the coated chip of the present invention were not damaged as compared with the comparative chip and the comparative coated chip, the tool life was extended. It can be seen that the toughness of the coated chip of the present invention is improved as compared with the comparative chip and the comparative coated chip.

  The cBN tool using the cBN sintered body having excellent toughness according to the present invention as a tool base exhibits excellent fracture resistance over a long period of use without causing any fracture or breakage, thereby extending the tool life. Therefore, it is possible to satisfactorily meet the demand for higher performance of the cutting apparatus, labor saving and energy saving of cutting, and cost reduction.

Claims (2)

Cubic boron nitride-based ultra-high-pressure sintered body cutting using cubic boron nitride-based ultra-high-pressure sintered body containing cubic boron nitride particles, binder phase, Ti boride phase, and W boride phase as a tool base In the tool, the average particle size of cubic boron nitride particles is 0.5 to 3.5 μm, the content thereof is 40 to 75% by volume, and the average particle size is 50 to 500 nm in the binder phase. A fine Ti boride phase and a fine W boride phase having an average particle diameter of 50 to 500 nm are dispersed and distributed. The sum of the fine Ti boride phase and the W boride phase produced is 5 to 15% by volume, and 15 to 35% by volume in the binder phase is at least one of Al nitride and oxide, and the other is Ti nitride, carbide, boride, or At least one of carbonitrides and inevitable impurities, and
0.5 ≦ (production amount of W boride phase) / (production amount of Ti boride phase) ≦ 1.0
A cubic boron nitride-based ultrahigh-pressure sintered body cutting tool characterized by using a cubic boron nitride-based ultrahigh-pressure sintered body satisfying the above relationship as a tool base. The cubic boron nitride-based ultrahigh-pressure sintered cutting tool according to claim 1, wherein a hard coating layer is formed on the surface of the tool base by vapor deposition. Combined cutting tool.