JP2011212832A - Cutting tool made of cubic boron nitride group ultrahigh pressure sintered material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cutting tool made of a cubic boron nitride group ultrahigh pressure sintered material with an excellent chipping resistance and excellent wear resistance.SOLUTION: This cutting tool is made of a cubic boron nitride group ultrahigh pressure sintered material with a cBN grain formed by mixing a raw material powder for forming a hard phase, in which a surface of a cBN grain is constantly and continuously covered with composite nitride of Ti and Al with an average membrane thickness of 100-700 nm, with a raw material powder for forming a bonding phase and sintering them as a hard phase, and TiN as a main bonding phase. An intermediate adhesion layer made of a mixed composition of TiBand AlN is constantly and continuously formed on the interface between the hard phase including the cBN grains and the bonding phase. Preferably, complex nitride of Ti and Al covered on the surface of the cBN grain has a gradient composition structure.

Description

  The present invention relates to a cubic boron nitride (hereinafter referred to as cBN) -based super high pressure sintered material cutting tool (hereinafter referred to as a cBN tool) having excellent chipping resistance and wear resistance.

  Conventionally, cBN based ultra-high pressure sintered material (hereinafter referred to as a cBN sintered body) is used as a tool material having a low affinity with the work material for cutting of steel-based work materials such as steel and cast iron. A tool is known. For example, as shown in Patent Document 1, 20 to 80% by volume of cBN as a hard phase is contained, and the balance is carbides, nitrides, nitrides of 4a, 5a, and 6a in the periodic table. A cBN tool using a chemical compound or the like as a binder phase is known.

  Moreover, in what is shown by patent document 2, while forming the binder phase in a cBN sintered material two-dimensionally continuously, the average value of binder phase thickness shall be 1.5 micrometers or less, and the standard deviation is 0.9 or less. It has been proposed to improve both the hardness and strength of cBN tools and improve the wear resistance and fracture resistance by improving the variation of the binder phase thickness. As one measure for this, prior to pulverizing and mixing the raw material powder in a ball mill, titanium nitride (hereinafter referred to as TiN), which is the main binder phase component, is coated on the cBN particles in advance by RF sputtering. It has been proposed.

JP-A-53-77811 JP 2008-208028 A

  Conventionally, in order to achieve both hardness and strength for cBN tools, various proposals have been made on heat treatment of binder phase, powder pulverization method, mixing method, etc. For example, conventional cBN tools are made of high-hardness steel. When used in the above cutting process, there is a problem that the chipping resistance and the wear resistance are still insufficient and the tool life is short.

  Therefore, the present invention provides a cBN tool which has both hardness and strength, exhibits excellent chipping resistance and wear resistance even in the cutting of high hardness steel, and exhibits excellent cutting performance over a long period of use. For the purpose.

  In order to solve the above-mentioned problems, the present inventors have paid attention to the cBN particles that are the hard phase components of the cBN tool and conducted intensive research. As a result, the following knowledge was obtained.

  In conventional cBN tools, it is known that TiN, which is a binder phase (binder) forming component, is coated on the cBN particle surface in advance by RF sputtering, and then mixed with a ball mill (for example, Patent Document 2). However, in such a method, the cBN particles are likely to be aggregated, and therefore, the hard phase in the cBN sintered body is non-uniformly dispersed and uniform tool characteristics cannot be obtained. When used for cutting, the occurrence of chipping was inevitable.

  Therefore, the present inventors apply TiN coating on the surface of cBN particles to ALD (Atomic Layer Deposition) by reacting the molecules of the raw material compound one layer at a time with the substrate in the vacuum chamber, and repeatedly purging with Ar or nitrogen. As a result, it was found that the surface of the cBN particles was uniformly covered with the TiN film without any breaks, and the agglomeration of the cBN particles did not occur.

  Accordingly, the cBN particles uniformly coated with TiN are used as the raw material powder for forming the hard phase, and the TiN powder is used as the raw material powder for forming the binder phase, and these raw material powders are mixed and sintered, thereby cBN sintering. When the body was produced, it was found that the problem of dispersibility of cBN particles was almost solved.

  However, when a cutting tool was prepared from the cBN sintered body and subjected to cutting of high-hardness steel, the interfacial adhesion strength between cBN particles, which are a hard phase, and TiN, which forms the main binder phase, is not sufficient. In use, it was still found to be short-lived due to chipping.

  Therefore, the present inventors have further researched on the improvement of the interfacial adhesion strength between the hard phase composed of cBN particles and the binder phase composed mainly of TiN, and as a result, the surface of the cBN particles was made of titanium and aluminum. Cover uniformly with a composite nitride (hereinafter referred to as TiAlN), more preferably, the Al content ratio is high near the surface of the cBN particles, and the Ti content ratio increases as the distance from the cBN particle surface increases. In order to form a gradient composition structure, the surface of cBN particles is uniformly coated with TiAlN, and this is used as a raw material powder for forming a hard phase, which is used for forming a binder phase using TiN as a main binder phase. When mixed with raw material powder and sintered to prepare a cBN sintered body and further a cBN tool, cBN particles were uniformly dispersed and distributed in the sintered body. Result, became homogeneous tool characteristics across the cBN tool is obtained.

In addition, TiAlN coated on the surface of cBN particles causes interdiffusion and interfacial reaction with cBN of the hard phase and TiN of the binder phase due to high heat during sintering. As a result, the cBN hard phase and TiN bonds are bonded. An intermediate adhesion layer (interface reaction layer) composed of a mixed structure of titanium boride (hereinafter referred to as TiB ₂ ) and aluminum nitride (hereinafter referred to as AlN) is formed at the interface with the phase. Has high adhesion strength with both hard phase cBN and binder phase TiN, and as a result, the interfacial adhesion strength between cBN hard phase and TiN binder phase in cBN tools is significantly improved, and excellent chipping resistance, They found out that they would exhibit wear resistance.

The present invention has been made based on the above findings,
“(1) A raw material powder for forming a hard phase, in which the surface of cubic boron nitride particles is uniformly and seamlessly coated with a composite nitride of titanium and aluminum having an average film thickness of 100 to 700 nm, is used. A cutting tool comprising a cubic boron nitride-based ultrahigh pressure sintered material having cubic boron nitride particles formed by mixing and sintering with powder as a hard phase and titanium nitride as the main binder phase,
A cubic contact layer comprising a mixed structure of titanium boride and aluminum nitride is uniformly and seamlessly formed at the interface between the hard phase comprising the cubic boron nitride particles and the binder phase. Cutting tool made of crystal boron nitride based ultra-high pressure sintered material.

  (2) The above-mentioned composite nitride of titanium and aluminum that uniformly covers the surface of cubic boron nitride particles has a high aluminum content in the vicinity of the surface of cubic boron nitride particles, and cubic boron nitride. The cutting tool made of a cubic boron nitride-based ultrahigh pressure sintered material according to (1), wherein the cutting composition is provided with a gradient composition structure in which the content ratio of titanium is high in a region far from the particle surface.

(3) The composite nitride of titanium and aluminum that uniformly covers the surface of cubic boron nitride particles uniformly has a composition gradient structure in the range of an average film thickness of 100 to 500 nm. The cubic boron nitride-based ultrahigh pressure sintered material-made cutting tool according to (2) above.
(4) The content ratio of cubic boron nitride in the cubic boron nitride-based ultrahigh pressure sintered material is 75 to 85% by volume, as described in (1) to (3) above Cutting tool made of cubic boron nitride based ultra high pressure sintered material. "
It is characterized by.

  The present invention will be described below.

  As the cBN raw material powder for producing the cBN tool of the present invention, cBN particles whose surface is coated with TiAlN are used. However, as a film forming method for uniformly coating cBN particles with TiAlN, For example, an ALD (Atomic Layer Deposition) method is suitable. According to the ALD method, TiAlN can be deposited on the surface of the cBN particles one by one, so that the pinhole-free (uniformly uninterrupted) TiAlN with a uniform thickness without causing aggregation of the cBN particles. Can be coated.

For example, when TiAlN is coated on the surface of cBN particles by the ALD method, the cBN particles are charged into a fluidized bed furnace and heated to about 200 ° C. under a reduced pressure of 2 Torr, for example, as a Ti precursor. As a precursor of TDMAT tetrakisdimethylaminotitanium and Al, DMAH-EPP dimethylaluminum hydride-ethylpiperidine and as a reaction gas, NH ₃ ammonia gas is introduced, Ar gas purge step, NH ₃ gas inflow step, Ar gas purge step By repeating this cycle as one cycle, for example, by forming a film over 50 cycles (10 hours), a TiAlN film with a film thickness of 100 nm can be formed on the surface of the cBN particle. Type electron microscope), according to the observation It can be said that by the absence, uniform rift not coated is formed.

  In addition, when the surface of the cBN particle is coated with TiAlN having a gradient composition structure in which the Al content is high near the surface of the cBN particle and the Ti content increases as the distance from the cBN particle surface increases, As for the composition of DMAH-EPP as a precursor of TDMAT and Al as a body, it is possible to form TiAlN having a gradient composition structure by gradually increasing the blending ratio of TDMAT every film formation time or cycle. it can.

Note that the uniformity of the coating of the TiAlN film on the surface of the cBN particles can be confirmed by TEM (transmission electron microscope) observation.
FIG. 1 is a schematic diagram showing a mixed state of cBN particles in which the surface of cBN particles is uniformly coated with TiAlN.

  Here, if there is a gap in the TiAlN film coated on the surface of the cBN particles, cBN will be in direct contact with the binder phase mainly composed of TiN, so that a sufficient sintering reaction will not proceed. The film needs to be formed uniformly and without gaps. From this point of view, the ALD method is suitable as the film forming method for coating the surface of cBN particles with TiAlN.

Moreover, the average film thickness of TiAlN formed on the surface of the cBN particles can generally be set to 100 to 700 nm. If the average film thickness of TiAlN is less than 100 nm, uniform film formation is difficult even if film formation is performed by the ALD method, and pinhole formation or cBN particle aggregation may occur. On the other hand, when the average film thickness of TiAlN exceeds 700 nm, the Al component concentration around the cBN particles inevitably increases, but the reaction with cBN is promoted by the presence of a large amount of Al during sintering. Further, reaction products such as TiB ₂ and AlN are generated excessively, so that the intermediate adhesion layer becomes brittle, and as a result, the strength of the cBN sintered body is reduced.

  Therefore, the average film thickness of TiAlN formed on the cBN particle surface can be 100 to 700 nm.

However, when TiAlN having a gradient composition structure is formed on the surface of cBN particles, the average film thickness is preferably in the range of 100 to 500 nm. This is because when the average film thickness exceeds 500 nm, the Al component becomes excessive as a result, the reaction with cBN is promoted, reaction products such as TiB ₂ and AlN are generated excessively, and the intermediate adhesion layer is formed. This is because the strength of the cBN sintered body is lowered by embrittlement.

Note that TiAlN having a gradient composition structure is represented by the composition formula: (Ti _1-X Al _X ) N (where X is an atomic ratio).
In the region near the surface of the cBN particle (within 100 (nm) from the cBN particle surface), the Al content ratio X is preferably X = 0.6 to 0.8, while the cBN particle X in a region away from the surface of the material (region where the average film thickness is d (nm), a region exceeding 100 nm from the cBN particle surface and away to d (nm)) is X = 0.2-0. .4 is preferred.

  Therefore, when TiAlN having a gradient composition structure is formed on the cBN particle surface, the average film thickness is preferably in the range of 100 to 500 nm.

  Moreover, in this invention, the content ratio of cBN in the cBN sintered body is 75 to 85% by volume. However, when the content ratio of cBN is less than 75% by volume, when the cBN tool is used as a cBN tool, a desired fracture resistance is obtained. On the other hand, if the content ratio of cBN exceeds 85% by volume, the content ratio of the binder phase is relatively reduced, and the sinterability is lowered. The content ratio of cBN in the body is defined as 75 to 85% by volume.

  In producing a cBN tool, the cBN particles coated with the TiAlN film produced above are used as raw material powder for forming a hard phase, and at least TiN powder, which is a component mainly constituting a binder phase (binder), is used for forming a binder phase. Used as raw material powder, both raw material powders are blended so as to have a predetermined composition, and sintered under normal ultra-high pressure and high temperature conditions to produce a cBN sintered body, but the cBN particle surface is coated with a TiAlN film As a result, aggregation of the cBN particles can be prevented, so that a cBN sintered body in which cBN is uniformly dispersed over the entire cBN sintered body can be produced.

  In addition, as other constituents in the cBN sintered body, components normally contained in the cBN sintered body, that is, nitrides, carbides, borides, oxides of the periodic table 4a, 5a, and 6a group elements, and It does not prevent at least one or more selected from the group consisting of these solid solutions from being contained.

FIG. 2 shows the structure of the cBN particles existing in the cBN sintered body, the intermediate adhesion layer (mixed structure of TiB ₂ and AlN) formed on the surface of the cBN particles, and the structure of the binder phase mainly composed of TiN around these. It is a schematic diagram which shows a structure.

TiAlN (see FIG. 1) that has been coated on the surface of the cBN particles prior to sintering diffuses and reacts with cBN (hard phase) and TiN (binding phase) through the sintering process, and TiB ₂ And a mixed structure of AlN (see FIG. 2).

The intermediate adhesion layer composed of the mixed structure of TiB ₂ and AlN formed is uniformly and continuously formed around the surface of the cBN hard phase in the same manner as TiAlN coated on the surface of the cBN particles.

  The average layer thickness of the intermediate adhesion layer is affected by the average film thickness of TiAlN coated on the cBN particles, the presence or absence of the gradient composition structure, the sintering conditions, etc., but the average film of TiAlN formed on the cBN particle surface When the thickness is in the range of 100 to 700 nm, an intermediate adhesion layer having an average layer thickness of about 40 to 300 nm is formed, and when TiAlN having a gradient composition structure is formed, the average of TiAlN is formed. An intermediate adhesion layer having a thickness in the range of 100 to 500 nm and an average layer thickness of about 30 to 150 nm is formed.

  As already described, if the average film thickness of TiAlN on the surface of cBN particles is less than 100 nm (corresponding to the average film thickness of the intermediate adhesion layer is less than 40 nm), pinhole formation and cBN particle adhesion may occur. As a result, as the cBN sintered body, the sintering reaction rate is reduced and the cBN hard phase is non-uniformly distributed and distributed, so that uniform sintered body characteristics cannot be obtained. When this is used as a cBN tool, The chipping resistance is inferior.

On the other hand, when the average film thickness of TiAlN exceeds 700 nm (corresponding to the film thickness of the intermediate adhesion layer exceeding 300 nm), since the Al component concentration around the cBN particles is high, excessive TiB ₂ , AlN during sintering And the intermediate adhesion layer becomes brittle, which leads to a decrease in strength of the cBN sintered body.

  In particular, when TiAlN having a gradient composition structure is formed and the average film thickness exceeds 500 nm (corresponding to the film thickness of the intermediate adhesion layer exceeding 180 nm), the strength of the cBN sintered body is reduced as described above. It will be.

  Therefore, it is desirable that the average layer thickness of the intermediate adhesion layer be in the range of 40 to 300 nm. In particular, when TiAlN having a gradient composition structure is formed, the average layer thickness of the intermediate adhesion layer is 30 to 150 nm. It is desirable to be within the range.

In addition, TiAlN decomposes and reacts during sintering between the cBN hard phase and the TiN bonded phase of the cBN sintered body, and as a result, an intermediate adhesion layer composed of a mixed structure of TiB ₂ and AlN is formed. After cutting the sintered body by wire cutting, the surface is smoothed using ion polishing, and the cross section is observed using SEM (scanning electron microscope) and EPMA (electron beam microanalyzer). It can also be confirmed by AES (Auger electron spectroscopy).

  The observed tissue state is as shown in the schematic schematic diagram of FIG.

As described above, in the cBN tool of the present invention, the surface of cBN particles uniformly coated with TiAlN is used as a raw material powder for forming a hard phase, and this is used for forming a bonded phase having TiN as a main bonded phase. By mixing and sintering with the raw material powder, an intermediate adhesion layer composed of a mixed structure of TiB ₂ and AlN is formed at the interface between the cBN hard phase and the TiN bonded phase, so that the cBN hard phase is in the sintered body. In addition to being uniformly distributed and obtaining uniform tool characteristics, the intermediate adhesion layer exhibits excellent chipping resistance and wear resistance by improving the interfacial adhesion strength between the cBN hard phase and the TiN bonded phase.

It is a schematic diagram which shows the mixed state of the cBN particle | grains of this invention before sintering by which the surface of cBN particle | grains was uniformly coat | covered with TiAlN, without sintering. The cBN particles present in the sintered cBN body of the present invention after sintering, the intermediate adhesion layer (mixed structure of TiB ₂ and AlN) formed on the surface of the cBN particles, and the binder phase mainly composed of TiN present around these It is a schematic diagram showing the organization and structure.

  Below, the cBN tool of this invention is demonstrated based on an Example.

Preparation of cBN particles coated with TiAlN:
A cBN particle having an average particle diameter of 3 μm is used as a base material, and a TiAlN film having a film thickness shown in Table 1 is uniformly and continuously formed thereon by an ALD (Atomic Layer Deposition) method under the conditions shown in Table 1.

  When the cBN particles coated with TiAlN obtained above were observed using a TEM (transmission electron microscope), it was confirmed that the cBN particles were uniformly and continuously coated on the surface.

原料粉末として、上記で作製したＴｉＡｌＮを被覆形成したｃＢＮ粒子粉末と、いずれも０．３〜０．９μｍの範囲内の平均粒径を有するＴｉＮ粉末、ＴｉＣ粉末、ＴｉＣＮ粉末、ＴｉＡｌ_３粉末、Ａｌ_２Ｏ_３粉末、ＷＣ粉末を用意し、これら原料粉末を表２に示される配合組成に配合し、ボールミルで４８時間アセトンを用いて湿式混合し、乾燥した後、油圧プレスにて成形圧１ＭＰａで直径：５０ｍｍ×厚さ：１．５ｍｍの寸法にプレス成形し、ついでこの成形体を、圧力：１Ｐａの真空雰囲気中、１０００〜１３００℃の範囲内の所定温度に３０〜６０分間保持して熱処理し、揮発成分および粉末表面への吸着成分を除去して切刃片用予備焼結体とし、この予備焼結体を、別途用意した、Ｃｏ：８質量％、ＷＣ：残りの組成、並びに直径：５０ｍｍ×厚さ：２ｍｍの寸法をもったＷＣ基超硬合金製支持片と重ね合わせた状態で、通常の超高圧焼結装置に装入し、通常の条件である圧力：５ＧＰａ、温度：１５００℃、保持時間：３０分間の条件で超高圧高温焼結し、ｃＢＮ焼結材を得る。ｃＢＮ焼結材円板を、ワイヤー放電加工機で所定寸法に切断し、Ｃｏ：５質量％、ＴａＣ：５質量％、ＷＣ：残りの組成およびＩＳＯ規格ＣＮＧＡ１２０４０８のインサート形状をもったＷＣ基超硬合金製インサート本体のろう付け部（コーナー部）に、質量％で、Ｃｕ：２６％、Ｔｉ：５％、Ａｇ：残りからなる組成を有するＡｇ合金のろう材を用いてろう付けし、上下面および外周研磨、ホーニング処理を施すことによりＩＳＯ規格ＣＮＧＡ１２０４０８のインサート形状をもつ表２に示す配合組成の本発明ｃＢＮ工具１〜１０を製造した。

As the raw material powder, cBN particle powder formed by coating TiAlN prepared above, and TiN powder, TiC powder, TiCN powder, TiAl ₃ powder, Al having an average particle diameter in the range of 0.3 to 0.9 μm. ₂ O ₃ powder and WC powder are prepared, these raw material powders are blended in the blending composition shown in Table 2, and are wet-mixed with acetone for 48 hours in a ball mill, dried, and then molded at a pressure of 1 MPa with a hydraulic press. Diameter: 50 mm × thickness: 1.5 mm, press-molded, and then the molded body is heat-treated by holding it at a predetermined temperature in the range of 1000-1300 ° C. for 30-60 minutes in a vacuum atmosphere at a pressure of 1 Pa. Then, volatile components and components adsorbed on the powder surface were removed to obtain a pre-sintered body for cutting edge pieces, and this pre-sintered body was prepared separately, Co: 8% by mass, WC: remaining composition, and In a state of being overlapped with a WC-based cemented carbide support piece having a diameter: 50 mm × thickness: 2 mm, the WC-based cemented carbide support piece is placed in a normal ultra-high pressure sintering apparatus, and pressure: 5 GPa, temperature which is a normal condition. Super high pressure and high temperature sintering under conditions of 1500 ° C. and holding time: 30 minutes to obtain a cBN sintered material. cBN sintered material disc was cut to a predetermined size with a wire electric discharge machine, Co: 5 mass%, TaC: 5 mass%, WC: remaining composition and WC-based carbide with ISO CNCN120408 insert shape The brazing part (corner part) of the alloy insert body is brazed using a brazing material of an Ag alloy having a composition of Cu: 26%, Ti: 5%, and Ag: the rest, and the upper and lower surfaces. Further, the present invention cBN tools 1 to 10 having the composition shown in Table 2 having the insert shape of ISO standard CNGA120408 were manufactured by performing peripheral polishing and honing treatment.

In addition, about the cBN sintered material of this invention cBN tool 1-10, after cut | disconnecting by a wire cut, the surface is smooth | blunted using ion polishing, The cross section is SEM (scanning electron microscope) and EPMA (electron beam microanalyzer). 2), as shown in the schematic diagram of FIG. 2, the intermediate adhesion layer composed of a mixed structure of TiB ₂ and AlN is uniformly and seamlessly formed at the interface between the cBN hard phase and the TiN bonded phase. It was confirmed that it was generated.

For comparison, as the raw material powder, cBN particle powder having an average particle diameter of 3 μm not coated with TiAlN, and TiN powder, TiC powder, and TiCN each having an average particle diameter in the range of 0.3 to 0.9 μm. Powder, TiAl ₃ powder, Al ₂ O ₃ powder, and WC powder are prepared, and these raw material powders are blended in the blending composition shown in Table 3, and in the same manner as the above-described cBN tool 1-10 of the present invention, ISO standard CNGA120408 Comparative example cBN tools 11-15 shown in Table 3 having an insert shape were manufactured.

  For reference, cBN particles having an average particle diameter of 3 μm are used as a base material, and the cBN particle surface is coated with TiN having an average film thickness of 50 nm by an ALD (Atomic Layer Deposition) method under the conditions shown in Table 1. Reference examples cBN tools 16 and 17 shown in Table 3 having an ISO standard CNGA120408 insert shape were produced by using the cBN particle powder as a raw material powder for forming a hard phase in the same manner as the cBN tools 1 to 10 of the present invention.

  The ALD conditions for forming TiN on the cBN particle surface are shown in (Note) in Table 3.

上記で得た本発明ｃＢＮ工具１〜１０、比較例ｃＢＮ工具１１〜１５および参考例ｃＢＮ工具１６，１７について、ビッカース硬度測定、三点曲げによる抗折力測定を行い、その機械的特性を評価した。
表４に、測定結果を示す。

With respect to the present invention cBN tools 1 to 10, comparative example cBN tools 11 to 15 and reference example cBN tools 16 and 17, the Vickers hardness measurement and the bending strength measurement by three-point bending are performed, and the mechanical properties are evaluated. did.
Table 4 shows the measurement results.

Moreover, about the said cBN tool 1-10 of this invention and the reference example cBN tools 16 and 17, after cut | disconnecting a sintered compact by a wire cut, the surface is smooth | blunted using ion polishing and the cross section is SEM (scanning-type electron). The structure formed at the interface between the cBN hard phase and the TiN bonded phase was confirmed by observing with a microscope) and EPMA (electron beam microanalyzer).
Table 4 shows the observation results of the tissue.

In addition, the above cBN tools 1 to 10 of the present invention, the comparative examples cBN tools 11 to 15 and the reference examples cBN tools 16 and 17 are subjected to a cutting test under the following cutting conditions, and the tool leads to the flank wear amount or chipping. Lifespan was measured.
<Cutting conditions>
Work material: Round bar with 6 V grooves (opening angle: 60 degrees) in the longitudinal direction of JIS / SCr420 (hardness: HRC58-62),
Cutting speed: 180 m / min,
Feed: 0.15 mm / rev,
Cutting depth: 0.25 mm,
Cutting time: Dry cutting test of chromium steel under the condition of 30 minutes.

  Table 4 shows the measurement results of the cutting test.

表２〜４に示される結果から、本発明ｃＢＮ工具１〜１０は、ｃＢＮ硬質相とＴｉＮ結合相との界面にＴｉＢ_２とＡｌＮの混合組織からなる中間密着層が形成されていることによって、硬度、抗折力が高く機械特性にすぐれるばかりか、耐チッピング性、耐摩耗性にもすぐれている。

From the results shown in Table 2-4, the present invention cBN tools 1 to 10 by an intermediate adhesive layer comprising a interface TiB ₂ and AlN mixed structure of the cBN hard phase and a TiN binder phase is formed, Not only has high hardness and bending strength, but also excellent mechanical properties, it also has excellent chipping resistance and wear resistance.

  On the other hand, since the comparative example cBN tools 11 to 15 are not formed with an intermediate adhesion layer, they are inferior in hardness, bending strength, chipping resistance, and wear resistance. Although the cBN tools 16 and 17 have an effect of suppressing chipping as compared with the comparative example cBN tool, the cBN tools 16 and 17 are compared with the cBN tool of the present invention in terms of hardness, bending strength, chipping resistance, and wear resistance. It was inferior to the invention.

Preparation of cBN particles coated with TiAlN:
Using a cBN particle having an average particle size of 3 μm as a base material, a TiAlN film having a graded composition structure and a film thickness shown in Table 5 is uniformly and slitted by an ALD (Atomic Layer Deposition) method under the conditions shown in Table 5. Form without.

  The graded composition structure has a composition ratio of TDMAT as a Ti precursor and a composition ratio of DMAH-EPP as an Al precursor by gradually increasing the composition ratio of TDMAT as the film formation time elapses or every cycle. TiAlN having a gradient composition structure was formed by coating.

Regarding the composition gradient structure,
The average composition of the TiAlN film in the region near the surface of the cBN particles (within a range of 100 (nm) from the surface of the cBN particles)
Composition formula: (Ti _1-α Al _α ) N (where α is an atomic ratio)
The value of α in the case of
The average composition of the TiAlN film in a region away from the surface of the cBN particle (in the case where the average film thickness is d, a region exceeding 100 (nm) and away from the cBN particle surface to d (nm)),
Composition formula: (Ti _1-β Al _β ) N (where β is an atomic ratio)
Value of β in the case of
This is shown in Table 5.

  Since α> 0.5> β with respect to the α value and β value shown in Table 5, the raw material powder for forming a hard phase produced under the conditions shown in Table 5 has the composition gradient structure shown in Table 5. It is clear.

  In addition, the value of (alpha) and the value of (beta) were measured by the quantitative analysis by EPMA (JEOLJXA-8800RL).

  Further, when the cBN particles coated with TiAlN having the composition gradient structure obtained above were observed using a TEM (transmission electron microscope), the surface of the cBN particles was uniformly and seamlessly coated with TiAlN having the composition gradient structure. Confirmed that it has been.

原料粉末として、上記で作製した組成傾斜構造のＴｉＡｌＮを被覆形成した表５に示すｃＢＮ粒子粉末と、いずれも０．３〜０．９μｍの範囲内の平均粒径を有するＴｉＮ粉末、ＴｉＣ粉末、ＴｉＣＮ粉末、ＴｉＡｌ_３粉末、Ａｌ_２Ｏ_３粉末、ＷＣ粉末を用意し、これら原料粉末を表６に示される配合組成に配合し、ボールミルで４８時間アセトンを用いて湿式混合し、乾燥した後、油圧プレスにて成形圧１ＭＰａで直径：５０ｍｍ×厚さ：１．５ｍｍの寸法にプレス成形し、ついでこの成形体を、圧力：１Ｐａの真空雰囲気中、１０００〜１３００℃の範囲内の所定温度に３０〜６０分間保持して熱処理し、揮発成分および粉末表面への吸着成分を除去して切刃片用予備焼結体とし、この予備焼結体を、別途用意した、Ｃｏ：８質量％、ＷＣ：残りの組成、並びに直径：５０ｍｍ×厚さ：２ｍｍの寸法をもったＷＣ基超硬合金製支持片と重ね合わせた状態で、通常の超高圧焼結装置に装入し、通常の条件である圧力：５ＧＰａ、温度：１５００℃、保持時間：３０分間の条件で超高圧高温焼結し、ｃＢＮ焼結材を得る。ｃＢＮ焼結材円板を、ワイヤー放電加工機で所定寸法に切断し、Ｃｏ：５質量％、ＴａＣ：５質量％、ＷＣ：残りの組成およびＩＳＯ規格ＣＮＧＡ１２０４０８のインサート形状をもったＷＣ基超硬合金製インサート本体のろう付け部（コーナー部）に、質量％で、Ｃｕ：２６％、Ｔｉ：５％、Ａｇ：残りからなる組成を有するＡｇ合金のろう材を用いてろう付けし、上下面および外周研磨、ホーニング処理を施すことによりＩＳＯ規格ＣＮＧＡ１２０４０８のインサート形状をもつ表６に示す配合組成の本発明ｃＢＮ工具１１〜２０を製造した。

As the raw material powder, cBN particle powder shown in Table 5 coated with TiAlN having the composition gradient structure prepared above, and TiN powder, TiC powder each having an average particle diameter in the range of 0.3 to 0.9 μm, TiCN powder, TiAl ₃ powder, Al ₂ O ₃ powder, WC powder are prepared, these raw material powders are blended in the blending composition shown in Table 6, wet mixed with acetone for 48 hours in a ball mill, and dried. It was press-molded into a size of diameter: 50 mm × thickness: 1.5 mm at a molding pressure of 1 MPa with a hydraulic press, and this molded body was then brought to a predetermined temperature within a range of 1000 to 1300 ° C. in a vacuum atmosphere of pressure: 1 Pa. Holding for 30 to 60 minutes for heat treatment, removing volatile components and components adsorbed on the powder surface to obtain a pre-sintered body for cutting edge pieces, and this pre-sintered body was prepared separately, Co: 8% by mass, C: Remaining composition and diameter: 50 mm × thickness: 2 mm, and superposed on a WC-based cemented carbide support piece, loaded into a normal ultra high pressure sintering apparatus, under normal conditions The pressure is 5 GPa, the temperature is 1500 ° C., and the holding time is 30 minutes under high pressure and high temperature sintering to obtain a cBN sintered material. cBN sintered material disc was cut to a predetermined size with a wire electric discharge machine, Co: 5 mass%, TaC: 5 mass%, WC: remaining composition and WC-based carbide with ISO CNCN120408 insert shape The brazing part (corner part) of the alloy insert body is brazed using a brazing material of an Ag alloy having a composition of Cu: 26%, Ti: 5%, and Ag: the rest, and the upper and lower surfaces. Further, the present invention cBN tools 11 to 20 having the composition shown in Table 6 and having an insert shape of ISO standard CNGA120408 were manufactured by performing peripheral polishing and honing treatment.

In addition, about the cBN sintered material of this invention cBN tool 11-20, after cut | disconnecting by a wire cut, the surface is smooth | blunted using ion polishing, The cross section is SEM (scanning electron microscope) and EPMA (electron beam microanalyzer). 2), as shown in the schematic diagram of FIG. 2, the intermediate adhesion layer composed of a mixed structure of TiB ₂ and AlN is uniformly and seamlessly formed at the interface between the cBN hard phase and the TiN bonded phase. It was confirmed that it was generated.

上記で得た本発明ｃＢＮ工具１１〜２０について、ビッカース硬度測定、三点曲げによる抗折力測定を行い、その機械的特性を評価した。
表７に、測定結果を示す。

About this invention cBN tool 11-20 obtained above, the bending strength measurement by a Vickers hardness measurement and three-point bending was performed, and the mechanical characteristic was evaluated.
Table 7 shows the measurement results.

Moreover, about the said cBN tools 11-20 of this invention, after cut | disconnecting a sintered compact by wire cut, the surface is smooth | blunted using ion polishing, The cross section is SEM (scanning electron microscope) and EPMA (electron beam micro). The structure formed at the interface between the cBN hard phase and the TiN bonded phase was confirmed by observing using an analyzer.
Table 7 shows the observation results of the tissue.

Moreover, about said cBN tool 11-20 of this invention, the cutting test was implemented on the following cutting conditions, and the tool life which leads to a flank wear amount or a defect | deletion was measured.
<Cutting conditions>
Work material: Round bar with 6 V grooves (opening angle: 60 degrees) in the longitudinal direction of JIS / SCr420 (hardness: HRC58-62),
Cutting speed: 180 m / min,
Feed: 0.2 mm / rev,
Cutting depth: 0.2 mm,
Cutting time: Dry cutting test of chromium steel under the condition of 30 minutes.

  Table 7 shows the measurement results of the cutting test.

表７に示される結果から、本発明ｃＢＮ工具１１〜２０は、ｃＢＮ硬質相とＴｉＮ結合相との界面に、ｃＢＮ粒子表面に均一にかつ切れ間なく被覆され組成傾斜構造のＴｉＡｌＮに由来するＴｉＢ_２とＡｌＮの混合組織からなる中間密着層が形成されていることによって、硬度、抗折力が高く機械特性にすぐれるばかりか、耐チッピング性、耐摩耗性にも一段とすぐれていることが分かる。

From the results shown in Table 7, the cBN tools 11 to 20 of the present invention have TiB ₂ derived from TiAlN having a composition gradient structure that is uniformly and seamlessly coated on the cBN particle surface at the interface between the cBN hard phase and the TiN binder phase. It can be seen that the formation of an intermediate adhesion layer composed of a mixed structure of AlN and AlN not only has high hardness and bending strength but also excellent mechanical properties, and also has excellent chipping resistance and wear resistance.

  As described above, since the cBN tool of the present invention is excellent in chipping resistance and wear resistance, it is sufficiently satisfied with high performance of the cutting machine, labor saving and energy saving of cutting, and cost reduction. In addition to being able to cope with it, it has excellent mechanical properties, so it can be expected to be widely applied to other fields such as wear-resistant members and sliding members.

Claims (4)

A raw material powder for forming a hard phase in which the surface of cubic boron nitride particles is uniformly and seamlessly coated with a composite nitride of titanium and aluminum having an average film thickness of 100 to 700 nm is mixed with the raw material powder for forming a binder phase. A cutting tool made of cubic boron nitride-based ultrahigh pressure sintered material having cubic boron nitride particles formed by sintering as a hard phase and titanium nitride as a main binder phase,
A cubic contact layer comprising a mixed structure of titanium boride and aluminum nitride is uniformly and seamlessly formed at the interface between the hard phase comprising the cubic boron nitride particles and the binder phase. Cutting tool made of crystal boron nitride based ultra-high pressure sintered material.   The titanium and aluminum composite nitride that uniformly covers the surface of cubic boron nitride particles uniformly has a high aluminum content in the vicinity of the surface of cubic boron nitride particles. The cutting tool made of cubic boron nitride-based ultra-high pressure sintered material according to claim 1, wherein the cutting tool is provided with a gradient composition structure in which the content ratio of titanium is high in a region farther away.   The composite nitride of titanium and aluminum that uniformly covers the surface of cubic boron nitride particles uniformly has a composition gradient structure in a range of an average film thickness of 100 to 500 nm. Item 3. A cutting tool made of cubic boron nitride-based ultrahigh pressure sintered material according to Item 2.   4. The cubic according to claim 1, wherein a content ratio of cubic boron nitride in the cubic boron nitride-based ultrahigh pressure sintered material is 75 to 85% by volume. 5. Cutting tool made of crystal boron nitride based ultra-high pressure sintered material.

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