JP2010235369A - Method of synthesizing cubic boron nitride and method of manufacturing cubic boron nitride sintered compact - Google Patents

Method of synthesizing cubic boron nitride and method of manufacturing cubic boron nitride sintered compact Download PDF

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JP2010235369A
JP2010235369A JP2009084138A JP2009084138A JP2010235369A JP 2010235369 A JP2010235369 A JP 2010235369A JP 2009084138 A JP2009084138 A JP 2009084138A JP 2009084138 A JP2009084138 A JP 2009084138A JP 2010235369 A JP2010235369 A JP 2010235369A
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cbn
boron nitride
metal catalyst
cubic boron
gpa
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JP5045953B2 (en
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Itsuro Tajima
逸郎 田嶋
Eko Wardoyo Akhmadi
アフマディ・エコ・ワルドヨ
Osamu Fukunaga
脩 福長
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Mitsubishi Materials Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a low pressure synthetic method of synthesizing cBN from hBN under a low pressure condition, and to provide a method of manufacturing cBN sintered compact using cBN raw material powder. <P>SOLUTION: The cBN is synthesized from the hBN by using alloy powder or mixed powder comprising ≥15 wt.% and ≤55 wt.% Cr or ≥15 wt.% and ≤55 wt.% (Cr+Mo), 1.5-8 wt.% Al, Mg and the balance Fe and Co (and a trace of Ni) as a metallic catalyst under a low pressure (≥4 GPa) at 1,200-1,900°C. The cBN sintered compact is obtained by using cBN as raw material powder, incorporating the alloy powder or the mixed powder used as the metal catalyst as a sintering aid in the raw material powder, and sintering them. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

本発明は、六方晶窒化ホウ素(以下、hBNで示す)から立方晶窒化ホウ素(以下、cBNで示す)を合成するcBNの合成方法であって、かつ、合成したcBNを原料粉末とするcBN焼結体の製造方法に関する。   The present invention relates to a cBN synthesis method for synthesizing cubic boron nitride (hereinafter referred to as cBN) from hexagonal boron nitride (hereinafter referred to as hBN), and a cBN sintering process using the synthesized cBN as a raw material powder. The present invention relates to a method for producing a bonded body.

従来、hBNからcBNを合成する合成方法としては、アルカリあるいはアルカリ土類元素を含むホウチッ化物(代表的な例はLiBN)を触媒として用いる方法が一般的なものとして知られているが、Co,Ni,Feなどの遷移金属とAlの合金、混合物も有効な触媒であることも知られている。 Conventionally, as a synthesis method for synthesizing cBN from hBN, a method using a boride containing an alkali or alkaline earth element (typically Li 3 BN 2 ) as a catalyst is generally known. It is also known that alloys of Al, transition metals such as Co, Ni and Fe, and mixtures thereof are effective catalysts.

例えば、特許文献1には、NiAl、CoAl、FeNiAl、FeNiCoAlなどの各合金が、圧力およそ6〜8.5GPa、温度800〜1600℃の条件で触媒作用を有することが報告されている。   For example, Patent Document 1 reports that alloys such as NiAl, CoAl, FeNiAl, and FeNiCoAl have a catalytic action under conditions of a pressure of about 6 to 8.5 GPa and a temperature of 800 to 1600 ° C.

特許文献2には、Fe46−Ni32−Cr21−Al1wt%、Ni39.2−Mn58.8−Al2wt%、Ni49−Cr49−Al2wt%、Fe8−Ni43−Cr47−Al2wt%などの混合物が、圧力5〜5.5GPa、温度約1400〜1500℃の範囲で、原料hBNをcBNに転換する触媒として効果があることが報告されている。   In Patent Document 2, a mixture of Fe46-Ni32-Cr21-Al 1 wt%, Ni39.2-Mn 58.8-Al2 wt%, Ni49-Cr49-Al2 wt%, Fe8-Ni43-Cr47-Al2 wt%, etc. has a pressure of 5-5. It is reported that the catalyst is effective as a catalyst for converting the raw material hBN to cBN within a range of 0.5 GPa and a temperature of about 1400 to 1500 ° C.

非特許文献1には、あらかじめアーク溶解炉で合金化したFe90−Al10wt%の組成の合金が、約6GPa以上でcBN合成触媒として有効であると報告されている。   Non-Patent Document 1 reports that an alloy having a composition of Fe90-Al 10 wt% previously alloyed in an arc melting furnace is effective as a cBN synthesis catalyst at about 6 GPa or more.

また、触媒を用いてhBNからcBNを合成した後、これを焼結することによって、cBN焼結体を製造し得ることも知られている。
例えば、特許文献3には、Co−Al混合物、Ni87−Al13wt%混合物、WC−Co−Al、NiAl合金、Co67−W16.5−Al16.5wt%などを原料hBNと共存させ、圧力5.4GPa以上、温度範囲は約1500〜1550℃で合成することによってcBNを生成させると、合成されたcBNは構成粒子が強固に結合した焼結体となることが報告されている。
It is also known that a cBN sintered body can be produced by synthesizing cBN from hBN using a catalyst and then sintering it.
For example, in Patent Document 3, a Co—Al mixture, a Ni87—Al13 wt% mixture, a WC—Co—Al, a NiAl 3 alloy, Co67—W16.5—Al16.5 wt% and the like are coexistent with the raw material hBN, and a pressure of 5. It has been reported that when cBN is produced by synthesis at 4 GPa or more and at a temperature range of about 1500 to 1550 ° C., the synthesized cBN becomes a sintered body in which constituent particles are firmly bonded.

米国特許3768972号明細書US Pat. No. 3,768,972 米国特許3918931号明細書US Pat. No. 3,918,931 米国特許3918219号明細書US Pat. No. 3,918,219

「窯業協会誌」Vol.78,No.1(1970年)7−14頁“Ceramic Association Magazine” Vol. 78, no. 1 (1970) 7-14

cBNは、ダイヤモンドに匹敵する硬度を持つほか、熱的、化学的にも安定であることから、cBN焼結体は、例えば、高速度鋼、ダイス鋼、鋳鉄等の鉄系被削材の切削工具用硬質材料等として幅広い分野で利用されている。
ところで、hBNからcBNを合成する際には、前記従来技術にも示したように、通常超高圧(5GPa以上)高温条件での合成が行われるが、cBN材料の大型化、生産性の向上等を目的として、特に、合成装置の大型化を図ったような場合には、(5GPa以上の)超高圧が必要であるか否かによって、操業の難易度、装置構成に大きな違いがあり、また、例えば、金型装置の中心部材である大型超硬合金の寿命も操業圧力が超高圧(5GPa以上)であるか否かによって格段の違いが生じる。
したがって、合成装置を大型化し、生産性の向上を図ったような場合にも、より緩和された低圧条件下で簡易にcBNを合成することができるcBNの合成方法が望まれている。
一方、cBN焼結体についても、より緻密で高硬度のcBN焼結体を製造する方法が望まれている。
Since cBN has hardness comparable to diamond and is also thermally and chemically stable, cBN sintered bodies are used for cutting high-speed steel, die steel, cast iron and other iron-based work materials. It is used in a wide range of fields as a hard material for tools.
By the way, when synthesizing cBN from hBN, as shown in the prior art, synthesis is usually performed under ultra-high pressure (5 GPa or more) and high temperature conditions. In particular, when the size of the synthesizer is increased, there are significant differences in the operational difficulty and device configuration depending on whether or not an ultra-high pressure (over 5 GPa) is required. For example, the life of a large cemented carbide, which is the central member of a mold apparatus, varies greatly depending on whether or not the operating pressure is extremely high (5 GPa or more).
Therefore, there is a demand for a method for synthesizing cBN capable of easily synthesizing cBN under more relaxed low-pressure conditions even when the synthesis apparatus is enlarged and productivity is improved.
On the other hand, a method for producing a denser and harder cBN sintered body is desired for the cBN sintered body.

本発明者らは、hBNからcBNを合成するに当たって、従来よりも低圧力条件(最低合成圧力が4GPa)で合成する方法について鋭意研究した結果、次のような知見を得た。   As a result of intensive studies on a method for synthesizing cBN from hBN under a lower pressure condition (minimum synthesis pressure is 4 GPa), the inventors have obtained the following knowledge.

hBNからcBNを合成するに当たって、従来は、Fe,Ni,Coなどの遷移金属とAlとの合金、混合物からなる金属触媒を用いていたが、その反応メカニズムは、まず、超高圧高温条件下で金属触媒が溶融して液相状態になり、該液相中にhBNの成分B(ホウ素)とN(窒素)が溶解し、その後cBNの核発生・成長が生じ、cBNの合成が進行すると考えられることから、B及びNの上記液相への溶解度が小さいような場合には、cBNが生成するに必要な条件が満足されず、また、仮に、上記液相中に十分なBとNが溶解したとしても、cBNの熱力学的平衡条件付近(例えば、従来の合成圧力よりも低い4〜5GPaという圧力条件)でcBNの核発生・成長を行わせcBNを合成するためには、cBNの核発生・成長を促進・助長する条件が必要となると考えられる。
したがって、金属触媒が液相状態でB溶解能力及びN溶解能力に優れ、同時に、cBNの核生成・成長を促進・助長する作用を有する場合には、従来よりも低圧力条件下でhBNからcBNを合成することができるといえる。
In the synthesis of cBN from hBN, conventionally, a metal catalyst comprising an alloy or mixture of transition metals such as Fe, Ni, Co and Al was used, but the reaction mechanism was first under ultra high pressure and high temperature conditions. It is thought that the metal catalyst melts into a liquid phase and the components B (boron) and N (nitrogen) of hBN dissolve in the liquid phase, and then nucleation and growth of cBN occurs and the synthesis of cBN proceeds. Therefore, in the case where the solubility of B and N in the liquid phase is small, the conditions necessary for forming cBN are not satisfied, and if sufficient B and N are present in the liquid phase, Even if dissolved, in order to synthesize cBN by nucleating and growing cBN near the thermodynamic equilibrium condition of cBN (for example, 4-5 GPa lower than the conventional synthesis pressure) Promote nucleation and growth It is considered a condition for promoting is required.
Therefore, when the metal catalyst has an excellent B-dissolving ability and N-dissolving ability in a liquid phase state, and at the same time has an action of promoting and promoting nucleation / growth of cBN, it is possible to convert cBN to cBN under a lower pressure condition than before. It can be said that can be synthesized.

ところで、従来用いられてきた金属触媒について、上記の観点から触媒成分の作用を見ると、Fe,Ni,Coなどの遷移金属は、それらが溶融して液相状態になっているときに数%程度のBを溶解する能力があり、ホウ素溶解成分の作用を有するが、その一方、Nを溶解する能力はきわめて小さいために、特に、低圧条件下で合成を行おうとした場合には、結果として、cBNへの転換反応が極めて不満足なものとなる。   By the way, regarding the conventionally used metal catalysts, when the action of the catalyst component is seen from the above viewpoint, transition metals such as Fe, Ni, Co and the like are several percent when they are melted and in a liquid phase state. It has the ability to dissolve a certain amount of B, and has the effect of a boron-dissolving component, while the ability to dissolve N is extremely small. , The conversion reaction to cBN becomes extremely unsatisfactory.

そこで、本発明者等は、N溶解能力に優れ、同時に、低圧条件下でもcBNの核生成・成長を促進・助長する作用を有する金属触媒について研究を進めたところ、金属触媒の成分としてCrを含有させると、液相状態において、CrがNを溶解する能力が大であり、また、同じく金属触媒の成分としてAl及びMgのいずれか1種又は両者を含有させると、cBNの核発生・成長が促進・助長され、4〜5GPaという従来の合成圧力よりも低い圧力条件においてもcBNが合成されることを見出した。   Therefore, the present inventors conducted research on a metal catalyst that has an excellent ability to dissolve N and at the same time promotes / promotes cBN nucleation / growth even under low pressure conditions. As a result, Cr was used as a component of the metal catalyst. When contained, Cr has a large ability to dissolve N in the liquid phase state. Similarly, when one or both of Al and Mg are contained as a component of the metal catalyst, nucleation / growth of cBN It was found that cBN was synthesized even under pressure conditions lower than the conventional synthesis pressure of 4-5 GPa.

また、遷移金属のうちのNiは、Fe,Coと同様に、ホウ素溶解成分の作用を有するものの、その反面、cBNの合成最低圧力を高くする傾向を有することから、金属触媒の成分としてNiを用いる場合には、その含有割合は少量に留めることが必要であることを見出した。
また、CrとMoが共存する場合、Cr単独よりも生成するcBN粒子径が増大する。これは、Crに対して、Mo添加によってチッ素の溶解度が増加するためと考えられる。
Ni in the transition metal, like Fe and Co, has the action of a boron-dissolving component, but on the other hand, it tends to increase the minimum synthesis pressure of cBN, so Ni is used as a component of the metal catalyst. When using, it discovered that the content rate needed to be kept small.
Moreover, when Cr and Mo coexist, the cBN particle diameter produced | generated increases rather than Cr alone. This is presumably because the solubility of nitrogen increases with the addition of Mo to Cr.

つまり、hBNからcBNを合成する際の金属触媒として、Nを溶解する作用を有するCr単独、あるいは、CrとMoの両者と、cBN核発生・成長を促進・助長する作用を有するAl、Mg成分と、残部はBを溶解する作用を有するFe,Co成分(及び更に少量のNi成分)からなる合金粉末あるいは混合粉末を用いることによって、合成最低圧力を4GPaにまで低下させることができ、その結果、従来よりも低圧力範囲でcBNを合成できることを見出したのである。   That is, as a metal catalyst for synthesizing cBN from hBN, Cr alone having the action of dissolving N, or both Cr and Mo, and Al and Mg components having the action of promoting and promoting the generation and growth of cBN nuclei The balance can be reduced to 4 GPa by using an alloy powder or mixed powder composed of Fe and Co components (and a small amount of Ni component) having an action of dissolving B, and as a result. The inventors have found that cBN can be synthesized in a lower pressure range than before.

さらに、本発明者らは、cBNを原料粉末とし、上記金属触媒を焼結助剤として用い、原料粉末と焼結助剤との混合粉に対して焼結を行ったところ、cBN粒子間で強固な直接結合を有する緻密かつ高硬度のcBN焼結体が得られることをも見出した。   Furthermore, the present inventors used cBN as a raw material powder, the above metal catalyst as a sintering aid, and sintered to a mixed powder of the raw material powder and the sintering aid. It has also been found that a dense and highly hard cBN sintered body having a strong direct bond can be obtained.

本発明は、上記知見に基づいてなされたものであって、
「(1) 金属触媒の存在下、超高圧高温条件で六方晶窒化ホウ素から立方晶窒化ホウ素を合成する立方晶窒化ホウ素の合成方法において、上記金属触媒は、15wt%以上55wt%以下のCrと、1.5〜8wt%のAl及びMgのいずれか1種又は2種と、残部はFe及びCoのいずれか1種又は2種の成分組成からなる合金粉末あるいは混合粉末であって、さらに、上記合成を、4GPa以上、1200〜1900℃で行うことを特徴とする立方晶窒化ホウ素の合成方法。
(2) 上記金属触媒が、22wt%以下のNiを更に含有することを特徴とする前記(1)に記載の立方晶窒化ホウ素の合成方法。
(3) 上記金属触媒が、15wt%≦(Cr+Mo)≦55wt%を満足するMoを更に含有することを特徴とする前記(1)または(2)に記載の立方晶窒化ホウ素の合成方法。
(4) 立方晶窒化ホウ素を原料粉末とし、該原料粉末に焼結助剤を添加して焼結することからなる立方晶窒化ホウ素焼結体の製造方法において、上記焼結助剤として、15wt%以上55wt%以下のCrと、1.5〜8wt%のAl及びMgのいずれか1種又は2種と、残部はFe及びCoのいずれか1種又は2種の成分組成からなる合金粉末あるいは混合粉末を、原料粉末に5〜10体積%添加して焼結することを特徴とする立方晶窒化ホウ素焼結体の製造方法。
(5) 上記焼結助剤が、22wt%以下のNiを更に含有することを特徴とする前記(4)に記載の立方晶窒化ホウ素焼結体の製造方法。
(6) 上記焼結助剤が、15wt%≦(Cr+Mo)≦55wt%を満足するMoを更に含有することを特徴とする前記(4)または(5)に記載の立方晶窒化ホウ素焼結体の製造方法。」
を特徴とするものである。
The present invention has been made based on the above findings,
“(1) In the method of synthesizing cubic boron nitride in which cubic boron nitride is synthesized from hexagonal boron nitride under ultrahigh pressure and high temperature in the presence of a metal catalyst, the metal catalyst contains 15 wt% or more and 55 wt% or less of Cr. Any one or two of Al and Mg of 1.5 to 8 wt%, and the balance is an alloy powder or mixed powder composed of any one or two of Fe and Co, A method for synthesizing cubic boron nitride, wherein the synthesis is performed at 4 GPa or more and 1200 to 1900 ° C.
(2) The method for synthesizing cubic boron nitride according to (1) above, wherein the metal catalyst further contains 22 wt% or less of Ni.
(3) The method for synthesizing cubic boron nitride according to (1) or (2), wherein the metal catalyst further contains Mo satisfying 15 wt% ≦ (Cr + Mo) ≦ 55 wt%.
(4) In a method for producing a cubic boron nitride sintered body comprising cubic boron nitride as a raw material powder, adding a sintering aid to the raw material powder and sintering, 15 wt. % Or more and 55 wt% or less of Cr, 1.5 to 8 wt% of any one or two of Al and Mg, and the balance is an alloy powder consisting of one or two of Fe and Co. A method for producing a cubic boron nitride sintered body, wherein the mixed powder is added to a raw material powder in an amount of 5 to 10% by volume and sintered.
(5) The method for producing a cubic boron nitride sintered body according to (4), wherein the sintering aid further contains 22 wt% or less of Ni.
(6) The cubic boron nitride sintered body according to (4) or (5), wherein the sintering aid further contains Mo satisfying 15 wt% ≦ (Cr + Mo) ≦ 55 wt%. Manufacturing method. "
It is characterized by.

本発明について、以下に詳細に説明する。   The present invention will be described in detail below.

金属触媒の成分・組成:
請求項1記載の発明では、金属触媒は、15wt%以上55wt%以下のCrと、1.5〜8wt%のAl及びMgのいずれか1種又は2種と、残部はFe及びCoのいずれか1種又は2種からなる合金粉末あるいは混合粉末として形成される。
Cr成分は、原材料であるhBNのNを溶融状態(液相)の金属触媒に溶解する作用を有するが、Cr成分の含有割合が15wt%未満では、Nの溶解量が少ないためcBNが十分生成されず、一方、Cr成分の含有割合が55wt%を超えると、金属触媒の溶融温度が高くなりすぎるために4〜5GPaという低圧力条件ではNの溶解度が低下しcBNが十分生成されないため、Nを溶解する作用を有するCr成分の含有割合は15wt%以上55wt%以下、好ましくは、20〜40wt%、と定めた。
Al成分、Mg成分は、いずれも、cBNの核発生・成長を促進・助長する作用を有し、金属触媒に少量添加含有させることで、cBN合成時の必要圧力を大きく低下させ、4〜5GPaの低圧条件でのcBNの合成を可能とするが、Al成分、Mg成分あるいは両者の合計含有割合が1.5wt%未満では、cBNの核発生・成長の促進・助長作用が少ないためcBNの形成が不十分となり、一方、Al成分が多すぎると窒化アルミニウムが生成してcBN生成の阻害要因となることがあり、また、Mg成分が多すぎるとホウ窒化マグネシウムが生成する可能性があり、焼結体を形成する上で望ましくないので、Al成分及びMg成分のいずれか1種又は2種の含有割合(但し、Al成分とMg成分の合計含有割合)を、1.5〜8wt%と定めた。
Fe及びCoのいずれか1種又は2種の成分は、夫々単独でも、また、これらを2種を組み合わせた場合でも、原材料であるhBNのBを、溶融状態(液相)の金属触媒に溶解する作用を有する。
なお、本発明の金属触媒は、所定の組成となるように各成分を混合した後、予めアーク溶解法、アトマイズ法等で合金化した合金粉末の形態で使用できるほか、各成分の粉末を所定の組成(配合)となるように配合しこれを混合した混合粉末の形態で使用することができる。
Components and composition of metal catalyst:
In the first aspect of the present invention, the metal catalyst is 15 wt% or more and 55 wt% or less of Cr, 1.5 to 8 wt% of any one or two of Al and Mg, and the balance is either Fe or Co. It is formed as an alloy powder or mixed powder composed of one or two kinds.
The Cr component has the effect of dissolving N of hBN, which is a raw material, in a metal catalyst in a molten state (liquid phase). However, if the Cr component content is less than 15 wt%, the amount of dissolved N is small, so that sufficient cBN is generated. On the other hand, if the content ratio of the Cr component exceeds 55 wt%, the melting temperature of the metal catalyst becomes too high, so that the solubility of N is reduced under low pressure conditions of 4 to 5 GPa and cBN is not sufficiently generated. The content ratio of the Cr component having an action of dissolving the selenium was 15 wt% or more and 55 wt% or less, preferably 20 to 40 wt%.
Both the Al component and the Mg component have the effect of promoting and promoting cBN nucleation / growth, and by adding a small amount to the metal catalyst, the required pressure at the time of cBN synthesis is greatly reduced to 4-5 GPa. CBN can be synthesized under low pressure conditions, but if the total content of the Al component, the Mg component, or both is less than 1.5 wt%, cBN nucleation, growth promotion, and promoting effect are small, and cBN formation On the other hand, if there is too much Al component, aluminum nitride may be generated and hinder the generation of cBN, and if there is too much Mg component, magnesium boronitride may be generated. Since it is not desirable for forming a bonded body, the content ratio of one or two of the Al component and the Mg component (however, the total content ratio of the Al component and the Mg component) is 1.5 to 8 wt%. It determined.
Either one or two components of Fe and Co can be used alone or in combination of two of them, and B of raw material hBN can be dissolved in a molten (liquid phase) metal catalyst. Has the effect of
The metal catalyst of the present invention can be used in the form of an alloy powder that is previously alloyed by an arc melting method, an atomizing method, etc. after mixing each component so as to have a predetermined composition. It can be used in the form of a mixed powder obtained by mixing and mixing so as to have the composition (mixing).

請求項2、3記載の発明では、金属触媒は、22wt%以下のNiを更に含有し、あるいは、15wt%≦(Cr+Mo)≦55wt%を満足するMoを更に含有する。
Ni成分は、Fe、Coと同様に、hBNのBを、溶融状態(液相)の金属触媒に溶解する作用を有するが、その反面、Ni成分の含有割合が、22wt%を超えると、cBN合成に際しての合成最低圧力を5Ga以上に高くすることから、より低圧条件下でcBNを合成するという本発明の観点からは、金属触媒の成分としてNiを用いる場合のNi成分の含有割合は22wt%以下に制限することが必要である。
また、Mo成分はCr成分と同様、溶融状態の金属の成分として存在している場合、それぞれ、Nの溶解度を向上させる。単独でも効果があるが、適当なCrとMoの組成比を選択すると、相乗的にNの溶解度が向上する。
ただし、Cr+Mo添加において、Cr成分とMo成分の合計含有割合が15wt%未満となる場合には、cBNの合成に際し、金属触媒の成分として、Cr、Moを含有させたことによる溶融状態(液相)の金属触媒にNを溶解する作用が低減し、低圧条件でcBNの合成を行うことが困難となり、一方、Cr成分とMo成分の合計含有割合が55wt%を超えると、必然的に、ホウ素溶解成分であるFe,Co,Niなどの組成比が減少するから、融点上昇やホウ素の溶解度の低下によって、cBNの合成圧力が上昇する。また、cBN焼結体を製造する場合、cBN粒子間に存在せしめる金属の融点が上昇して好ましくない。
それ故、Cr成分とMo成分の合計含有割合は、15wt%以上55wt%以下を満足することが必要である。
In the second and third aspects of the invention, the metal catalyst further contains 22 wt% or less of Ni, or further contains Mo satisfying 15 wt% ≦ (Cr + Mo) ≦ 55 wt%.
The Ni component has an action of dissolving B of hBN in a molten (liquid phase) metal catalyst, similarly to Fe and Co. On the other hand, when the content ratio of the Ni component exceeds 22 wt%, cBN From the viewpoint of the present invention of synthesizing cBN under a lower pressure condition since the minimum synthesis pressure at the time of synthesis is increased to 5 Ga or more, the content ratio of the Ni component when using Ni as the metal catalyst component is 22 wt%. It is necessary to limit to:
Further, like the Cr component, the Mo component improves the solubility of N when present as a molten metal component. Although it is effective by itself, the solubility of N is synergistically improved when an appropriate composition ratio of Cr and Mo is selected.
However, in the case of adding Cr + Mo, when the total content ratio of the Cr component and the Mo component is less than 15 wt%, in the synthesis of cBN, the molten state (liquid phase) by containing Cr and Mo as components of the metal catalyst ), The effect of dissolving N in the metal catalyst is reduced, and it is difficult to synthesize cBN under low pressure conditions. On the other hand, if the total content of Cr component and Mo component exceeds 55 wt%, boron is inevitably produced. Since the composition ratio of Fe, Co, Ni, etc., which are dissolved components, decreases, the synthesis pressure of cBN increases due to an increase in melting point and a decrease in boron solubility. Moreover, when manufacturing a cBN sintered compact, the melting | fusing point of the metal which exists between cBN particle | grains raises, and is not preferable.
Therefore, the total content ratio of the Cr component and the Mo component needs to satisfy 15 wt% or more and 55 wt% or less.

合成条件(圧力、温度):
hBNからcBNへの合成は、例えば、図1に示す合成装置内に、合成用原材料であるhBNと上記金属触媒の粉末を共存させた状態で配置し、圧力4GPa以上、温度1200〜1900℃で合成することによって行うことができる。
この発明では、上記金属触媒を用いることにより、cBNの最低合成圧力を4GPaにまで低減することができ、従来の合成法に比し、はるかに低圧力範囲(好ましくは、4.4GPa以上)でcBNの合成を行うことができる(勿論、従来法における合成圧力、例えば、5〜8.5GPaという高圧で合成を行うことも可能であるが)ため、設備の大型化が不要になり、装置構成部材の耐用寿命も延びる等のメリットがある。
合成温度が1200℃未満では、金属触媒の溶解が生じないためcBNの合成反応が進行せず、一方、1900℃を超えると、hBN⇔cBNの圧力・温度平衡状態により4〜5GPa圧力領域においては1900℃以上がhBNの安定領域のため、合成したcBNがhBNに逆変換する恐れがあることから、反応合成温度を1200〜1900℃(好ましくは、1300〜1750℃)と定めた。
Synthesis conditions (pressure, temperature):
In the synthesis from hBN to cBN, for example, in the synthesis apparatus shown in FIG. 1, hBN, which is a raw material for synthesis, and the above metal catalyst powder are coexisted, and the pressure is 4 GPa or more and the temperature is 1200 to 1900 ° C. This can be done by synthesis.
In this invention, by using the above metal catalyst, the minimum synthesis pressure of cBN can be reduced to 4 GPa, and in a much lower pressure range (preferably 4.4 GPa or more) compared to the conventional synthesis method. Since it is possible to synthesize cBN (of course, it is possible to synthesize at a synthesis pressure in the conventional method, for example, a high pressure of 5 to 8.5 GPa), it is not necessary to increase the size of the equipment, and the device configuration There are advantages such as extending the useful life of the member.
When the synthesis temperature is less than 1200 ° C., the metal catalyst does not dissolve, so the synthesis reaction of cBN does not proceed. On the other hand, when the synthesis temperature exceeds 1900 ° C., in the pressure range of 4-5 GPa due to the pressure / temperature equilibrium state of hBN⇔cBN. Since 1900 ° C. or higher is a stable region of hBN, the synthesized cBN may be converted back to hBN. Therefore, the reaction synthesis temperature was set to 1200 to 1900 ° C. (preferably 1300 to 1750 ° C.).

cBN焼結体:
従来、例えば、特許文献3に記載されたように、WC−Co−Al、NiAl、Co67−W16.5−Al16.5wt%などを焼結助剤とし、cBN粒子が強固に結合した焼結体を作製するためには、圧力5.4GPa以上、温度1500℃以上で行わなければならなかったが、本発明によれば、cBNを原料粉末とし、cBNの合成に用いた前記特定の成分組成の合金粉末あるいは混合粉末からなる金属触媒を焼結助剤として用い、焼結助剤の配合割合が5〜10体積%となるように原料粉末に配合し、例えば、図2に示す焼結装置内にこの混合粉末を配置し、例えば、4.0〜6.0GPaで加圧しながら、1200〜2000℃の温度範囲で焼結すると、cBN粒子間に強固な直接結合を有する緻密かつ高硬度のcBN焼結体を得ることができる。つまり、cBN合成時に用いる上記金属触媒は、cBN焼結体を製造する際の焼結助剤としての機能も備えるといえる。
例えば、図1に示す合成装置により、本発明の合成法で合成(金属触媒としては、Co58.2−Cr38.8−Al3wt%の成分組成のCo−Cr−Al系の金属触媒を使用)したcBN粉末を原料粉末とし、上記金属触媒と同一成分組成のCo−Cr−Al系合金を焼結助剤として用い、焼結助剤の含有割合が、10体積%となるように配合し、これを図2に示す焼結装置で、4.7GPa×1480〜1490℃の条件で焼結することによってcBN焼結体を製造した。本発明により得られたcBN焼結体の走査型電子顕微鏡写真による組織の一例を図4に示す。
すなわち、本発明の製造法で得られたcBN焼結体は、低温度での焼結であっても、非常に緻密な組織を有すると同時に、極めて高い硬度を有することが分かる。
たとえば、本発明例8においては、低温度(1600℃)の焼結であるにもかかわらず、緻密な組織を有する(図4参照)と同時に、Hv:3400という極めて高い硬度が得られている。
cBN sintered body:
Conventionally, for example, as described in Patent Document 3, WC-Co-Al, NiAl 3 , Co67-W16.5-Al16.5 wt% or the like is used as a sintering aid, and cBN particles are firmly bonded. In order to produce a body, it had to be performed at a pressure of 5.4 GPa or higher and a temperature of 1500 ° C. or higher. According to the present invention, the specific component composition used for the synthesis of cBN using cBN as a raw material powder 2 is used as a sintering aid, and is blended into the raw material powder so that the blending ratio of the sintering aid is 5 to 10% by volume. For example, the sintering apparatus shown in FIG. When this mixed powder is placed inside and sintered at a temperature range of 1200 to 2000 ° C. while being pressurized at 4.0 to 6.0 GPa, for example, a dense and high hardness having a strong direct bond between cBN particles cBN sintered body It is possible to obtain. That is, it can be said that the metal catalyst used at the time of cBN synthesis also has a function as a sintering aid when producing a cBN sintered body.
For example, the synthesis was performed by the synthesis method of the present invention using the synthesis apparatus shown in FIG. 1 (as the metal catalyst, a Co—Cr—Al-based metal catalyst having a component composition of Co 58.2-Cr 38.8-Al 3 wt%) was used. Using cBN powder as a raw material powder, using a Co—Cr—Al alloy having the same composition as that of the above metal catalyst as a sintering aid, blended so that the content of the sintering aid is 10% by volume. Was sintered under the conditions of 4.7 GPa × 1480 to 1490 ° C. using the sintering apparatus shown in FIG. 2 to produce a cBN sintered body. An example of the structure | tissue by the scanning electron micrograph of the cBN sintered compact obtained by this invention is shown in FIG.
That is, it can be seen that the cBN sintered body obtained by the production method of the present invention has a very dense structure and at the same time has an extremely high hardness even when sintered at a low temperature.
For example, in Example 8 of the present invention, despite having a low temperature (1600 ° C.) sintering, it has a dense structure (see FIG. 4) and at the same time has an extremely high hardness of Hv: 3400. .

上記のとおり、本発明は、特定の成分組成の金属触媒を用いてhBNからcBNを合成することにより、最低合成圧力を低下させることができるため従来に比し低圧力範囲(4GPa以上)で合成を行うことができ、cBN合成装置の大型化を必要とせず、設備費の低減を図ることができ、さらに、cBN合成装置構造部材の長寿命化を図ることができる。
また、cBNを原料粉末とし、上記金属触媒と同一成分組成の合金粉末、混合粉末を焼結助剤として用いて焼結を行うと、他の焼結所剤を用いることなしに、cBN粒子間に強固な直接結合を有すると同時に、緻密な組織な組織を有し、かつ、高硬度のcBN焼結体を製造することができ、cBN焼結体製造の低コスト化を図ることもできる。
As described above, the present invention can synthesize cBN from hBN using a metal catalyst having a specific component composition, so that the lowest synthesis pressure can be reduced. Therefore, the synthesis is performed in a lower pressure range (4 GPa or more) than in the past. Therefore, it is not necessary to increase the size of the cBN synthesizer, the equipment cost can be reduced, and the life of the structural member of the cBN synthesizer can be extended.
In addition, when cBN is used as a raw material powder and sintering is performed using an alloy powder having the same composition as the metal catalyst and a mixed powder as a sintering aid, the inter-cBN particles can be formed without using other sintering agents. It is possible to produce a cBN sintered body having a dense structure and a dense structure and a high hardness, and to reduce the cost of producing the cBN sintered body.

hBNからcBNを合成するcBN合成装置の試料配置概略図を示す。A sample arrangement schematic diagram of a cBN synthesizer that synthesizes cBN from hBN is shown. 合成したcBNを原料粉末としてcBN焼結体を製造するためのcBN焼結体製造装置の試料配置概略図を示す。The sample arrangement | positioning schematic of the cBN sintered compact manufacturing apparatus for manufacturing a cBN sintered compact using synthesized cBN as a raw material powder is shown. 本発明例8(圧力:4.2GPa、温度:1300℃、反応時間;1時間)により合成したcBNのX線回折チャート(cBNピークが存在する)を示す。The X-ray-diffraction chart (the cBN peak exists) of cBN synthesize | combined by this invention example 8 (pressure: 4.2 GPa, temperature: 1300 degreeC, reaction time; 1 hour) is shown. 本発明例8の金属触媒(Co46.6−Cr31−Mo20−Al2.4wt%)を用いて合成したcBN粉末を原料粉末とし、Co46.6−Cr31−Mo20−Al2.4wt%の金属触媒の含有割合が、10体積%となるように配合し、これを図2に示す焼結装置で、5.5GPa、かつ、1600℃の条件で焼結することによって得たcBN焼結体の走査型電子顕微鏡写真による組織を示す。The cBN powder synthesized using the metal catalyst of Example 8 of the present invention (Co46.6-Cr31-Mo20-Al2.4 wt%) is used as a raw material powder, and the content of the metal catalyst is Co46.6-Cr31-Mo20-Al2.4 wt%. The scanning electron of the cBN sintered body obtained by blending the ratio so as to be 10% by volume and sintering this with the sintering apparatus shown in FIG. 2 under the conditions of 5.5 GPa and 1600 ° C. The structure by a micrograph is shown.

以下に、本発明のcBN合成方法、cBN焼結体の製造方法について、実施例に基づいて具体的に説明する。   Hereinafter, the cBN synthesis method and the cBN sintered body manufacturing method of the present invention will be specifically described based on examples.

本発明例1:
図1に示すように、金属触媒として、Co58.2−Cr38.8−Al3wt%からなる成分組成の合金粉末をあらかじめ作り、約7mm径で3mm厚さの2枚のhBN成形板(4)間に約1.6mm厚さのサンドイッチされた金属触媒(合金粉末)層(3)が形成されるように、外径10mm,内径7mm,高さ7.6mmの食塩(ジルコニア粉末を10wt%含む)成形体(5)の試料容器中に充填した。
これらの試料を、外径12mm,内径10mm,高さ17.6mmのグラファイト管状ヒーター(1)で囲み、内面にはMo箔(2)を配置し、ベルト型超高圧装置(アンビル先端径21mm,シリンダー内径25mm)で加圧し、その後ヒーターに電力を投入して加熱して、一定時間保持後、急速に温度を下げ、その後除圧して試料を取り出し、光学顕微鏡、X線回折などの手法で試料を同定した。
圧力4.7GPa、1436℃で1時間反応させた試料を解析した結果、全体が黄色の0.2mm程度のcBN粒子と金属相との混合物であり、cBNの合成が起こったことがわかった。
また、上記と同じ成分組成の混合粉末を金属触媒として、圧力4.2GPa、1370℃で1時間反応させたところ、約1.5mmの原料層が、cBN粒子と金属相との混合物に転換し、やはりcBNの合成が行われたことがわかる。
ここで、X線回折は、ブルカー製AXSMXP18VAHFにより測定を行った。
Invention Example 1:
As shown in FIG. 1, an alloy powder having a composition of Co58.2-Cr38.8-Al3 wt% is prepared in advance as a metal catalyst, and is formed between two hBN molded plates (4) having a diameter of about 7 mm and a thickness of 3 mm. So that a sandwiched metal catalyst (alloy powder) layer (3) having a thickness of about 1.6 mm is formed on the outer surface of sodium chloride (including 10 wt% of zirconia powder) having an outer diameter of 10 mm, an inner diameter of 7 mm, and a height of 7.6 mm. It filled in the sample container of the molded object (5).
These samples were surrounded by a graphite tubular heater (1) having an outer diameter of 12 mm, an inner diameter of 10 mm, and a height of 17.6 mm, Mo foil (2) was disposed on the inner surface, and a belt type ultrahigh pressure apparatus (anvil tip diameter of 21 mm, Pressurize with a cylinder inner diameter of 25 mm), and then apply power to the heater to heat it, hold it for a certain period of time, then rapidly lower the temperature, then remove the pressure and take out the sample, and use a method such as optical microscopy or X-ray diffraction Was identified.
As a result of analyzing the sample reacted for 1 hour at a pressure of 4.7 GPa and 1436 ° C., it was found that the whole was a mixture of yellow cBN particles of about 0.2 mm and a metal phase, and cBN synthesis occurred.
Moreover, when a mixed powder having the same composition as described above was used as a metal catalyst and reacted at a pressure of 4.2 GPa and 1370 ° C. for 1 hour, the raw material layer of about 1.5 mm was converted into a mixture of cBN particles and a metal phase. It can also be seen that cBN was synthesized.
Here, X-ray diffraction was measured by Bruker AXSMXP18VAHF.

本発明例2:
2〜4μmの粒度のcBNを原料粉末とし、焼結助剤として、上記金属触媒と同一成分組成からなる混合粉末(Co58.2−Cr38.8−Al3wt%)を用い、焼結助剤の含有割合が10体積%となるよう配合した混合粉末(2)を、図2に示すように0.02mm厚さのMo箔で内側を囲んだ外径10mm、内径7mm、高さ7.6mmの食塩(ジルコニア粉末を10wt%含む)成形体(5)間にサンドイッチされるように充填し、圧力4.7GPa、1480〜1490℃で0.5時間焼結した。
得られたcBN焼結体を走査型電子顕微鏡で観察したところ、各cBN粒子間に強固な直接結合を有し、緻密な焼結組織を有するとともに、得られたcBN焼結体は、高硬度を有していた。
Invention Example 2:
CBN having a particle size of 2 to 4 μm is used as a raw material powder, and a mixed powder (Co58.2-Cr38.8-Al3 wt%) having the same composition as the metal catalyst is used as a sintering aid, The mixed powder (2) blended so as to have a ratio of 10% by volume is salted with an outer diameter of 10 mm, an inner diameter of 7 mm, and a height of 7.6 mm surrounded by a 0.02 mm-thick Mo foil as shown in FIG. It was filled so as to be sandwiched between shaped bodies (5) (containing 10 wt% of zirconia powder), and sintered at a pressure of 4.7 GPa and 1480 to 1490 ° C. for 0.5 hour.
When the obtained cBN sintered body was observed with a scanning electron microscope, each cBN particle had a strong direct bond, had a dense sintered structure, and the obtained cBN sintered body had a high hardness. Had.

本発明例3:
本発明例1において、Alに替えてMgを含有させた金属触媒、即ち、Co58.2−Cr38.8−Mg3wt%組成の金属触媒、を用いて、圧力4.2GPa、1370℃で1時間反応させたところ、金属触媒層付近に非常に微細なcBN粒子が析出していたことから、MgはAlと同様な作用を有する成分であることがわかる。
Invention Example 3:
In Example 1 of the present invention, a metal catalyst containing Mg instead of Al, that is, a metal catalyst having a composition of Co 58.2-Cr 38.8-Mg 3 wt%, was reacted at a pressure of 4.2 GPa at 1370 ° C. for 1 hour. As a result, very fine cBN particles were precipitated in the vicinity of the metal catalyst layer, and it can be seen that Mg is a component having the same action as Al.

本発明例4:
Fe52.38−Cr38.8−Ni5.82−Al3wt%からなる成分組成の混合粉末を金属触媒として用い、本発明例1と同様な方法で、圧力を4.2GPa、温度は1280℃、1380℃、1435℃の三種類、反応時間1時間で反応させたところ、いずれの場合も、cBNが合成されていることをX線回折により確認した。
Invention Example 4:
Using a mixed powder having a component composition of Fe52.38-Cr38.8-Ni5.82-Al3 wt% as a metal catalyst, the pressure was 4.2 GPa, the temperatures were 1280 ° C. and 1380 ° C. in the same manner as in Example 1 of the present invention. When the reaction was carried out at 1435 ° C. for 3 hours at a reaction time of 1 hour, it was confirmed by X-ray diffraction that cBN was synthesized in all cases.

比較例1:
本発明例4とFe,Cr,Niの含有割合が類似するが、Al成分を全く含有しない成分組成の混合物(Fe54−Cr40−Ni6wt%)を金属触媒として用い、本発明例1と同様な方法で、圧力を5GPa、温度は1400℃、反応時間1時間で反応させたところ、金属は溶解していた痕跡は認められるものの、X線回折によるcBNの存在は全く検出されなかった。
Comparative Example 1:
The same method as in Example 1 of the present invention, using a mixture (Fe54-Cr40-Ni6 wt%) having a composition similar to that of Example 4 of the present invention, but containing no Al component at all, similar in content ratio of Fe, Cr, Ni Then, when the reaction was performed at a pressure of 5 GPa, a temperature of 1400 ° C., and a reaction time of 1 hour, traces of the metal being dissolved were observed, but the presence of cBN was not detected at all by X-ray diffraction.

本発明例3、本発明例4と比較例1の結果から、金属触媒中のAl成分、Mg成分が、cBNの低圧合成において、cBNの核発生・成長を促進・助長する作用を有することがわかる。   From the results of Invention Example 3, Invention Example 4 and Comparative Example 1, it can be seen that the Al component and Mg component in the metal catalyst have the effect of promoting and promoting cBN nucleation / growth in low-pressure synthesis of cBN. Recognize.

本発明例5:
本発明例4と同様に、Fe52.38−Cr38.8−Ni5.82−Al3wt%からなる成分組成の混合粉末を金属触媒として用い、圧力を4.1GPaに変更し、また、温度は1325℃、1340℃、1350℃、1470℃の四種類、反応時間1時間で反応させたところ、いずれの場合も、金属皮膜に包まれた約0.3〜0.4mmのcBN結晶が多量に合成析出していることを確認した。
さらに、上記金属触媒を用い、圧力を4.0GPaに変更し、温度は1300℃、1380℃の二種類、反応時間1時間で反応させたところ、いずれの場合も、金属皮膜に包まれた約0.3〜0.4mmのcBN結晶がやはり多量に合成析出していた。
Invention Example 5:
Similar to Example 4 of the present invention, a mixed powder having a component composition of Fe 52.38-Cr 38.8-Ni 5.82-Al 3 wt% was used as a metal catalyst, the pressure was changed to 4.1 GPa, and the temperature was 1325 ° C. , 1340 ° C, 1350 ° C, 1470 ° C, and reaction time of 1 hour. In each case, a large amount of cBN crystals of about 0.3 to 0.4 mm wrapped in a metal film were synthesized and precipitated. I confirmed that
Furthermore, when the metal catalyst was used, the pressure was changed to 4.0 GPa, and the reaction was carried out in two kinds of temperatures, 1300 ° C. and 1380 ° C., with a reaction time of 1 hour. A large amount of 0.3 to 0.4 mm of cBN crystals was also synthesized and precipitated.

本発明例5からもわかるように、本発明の成分組成の金属触媒を使用したときのcBN最低合成圧力は、4.0GPaであることがわかる。   As can be seen from Example 5 of the present invention, it can be seen that the minimum cBN synthesis pressure when using the metal catalyst having the component composition of the present invention is 4.0 GPa.

本発明例6:
2〜4μmの粒度のcBNを原料粉末とし、焼結助剤として、Fe52.38−Cr38.8−Ni5.82−Al3wt%の成分組成の混合粉末を用い、焼結助剤の含有割合が10体積%となるよう配合した混合粉末(2)を、図2に示すように0.02mm厚さのMo箔で内側を囲んだ外径10mm、内径7mm、高さ7.6mmの食塩(ジルコニア粉末を10wt%含む)成形体(5)間にサンドイッチされるように充填し、圧力4.7GPa、1470℃で0.5時間焼結した。
得られたcBN焼結体は、各cBN粒子間に強固な直接結合を有し、図4に示されると同様な緻密な焼結組織を有しており、かつ、高硬度であった。
Invention Example 6:
CBN having a particle size of 2 to 4 μm is used as a raw material powder, and a mixed powder having a component composition of Fe52.38-Cr38.8-Ni5.82-Al3 wt% is used as a sintering aid, and the content ratio of the sintering aid is 10 As shown in FIG. 2, the mixed powder (2) blended so as to have a volume% is surrounded by 0.02 mm-thick Mo foil, and the outer diameter is 10 mm, the inner diameter is 7 mm, and the height is 7.6 mm. Sodium chloride (zirconia powder) Was packed so as to be sandwiched between the molded bodies (5), and sintered at a pressure of 4.7 GPa and 1470 ° C. for 0.5 hours.
The obtained cBN sintered body had a strong direct bond between the respective cBN particles, had a dense sintered structure similar to that shown in FIG. 4, and had high hardness.

本発明例7:
Co49.28−Cr27.14−Ni20.71−Al2.6wt%からなる成分組成の混合粉末を金属触媒として用い、本発明例1と同様な方法で、4.4GPa、1400℃で1時間反応させたところ、全体に多量の微粒子cBN結晶が生成していた。
Invention Example 7:
Using a mixed powder having a component composition of Co49.28-Cr27.14-Ni20.71-Al2.6 wt% as a metal catalyst, the mixture was reacted at 4.4 GPa and 1400 ° C. for 1 hour in the same manner as in Example 1 of the present invention. As a result, a large amount of fine particle cBN crystals was formed on the whole.

比較例2,比較例3:
本発明例7の上記金属触媒において、Ni含有割合を増加させたCo47.1−Cr26.1−Ni23.6−Al2.8wt%の金属触媒(比較例2)、Co43.8−Cr22.3−Ni28.8−Al3.2wt%の金属触媒(比較例3)を作製し、これを用いて、本発明例1と同様な方法で、5GPa、1400℃で1時間反応させたところ、X線回折によるcBNの存在は全く検出されなかった。
Comparative Example 2 and Comparative Example 3:
Co 47.1-Cr 26.1-Ni 23.6-Al 2.8 wt% metal catalyst (Comparative Example 2), Co 43.8-Cr 22.3- 3 with increased Ni content in the above metal catalyst of Invention Example 7. An Ni28.8-Al3.2 wt% metal catalyst (Comparative Example 3) was prepared and reacted at 5 GPa and 1400 ° C. for 1 hour in the same manner as in Example 1 of the present invention. The presence of cBN due to was not detected at all.

以上のことから、Niを金属触媒の成分として用いた場合には、Ni含有割合は、22wt%以下としなければならないことがわかる。   From the above, it can be seen that when Ni is used as a component of the metal catalyst, the Ni content must be 22 wt% or less.

本発明例8:
Co46.6−Cr31−Mo20−Al2.4wt%らなる成分組成の混合物を金属触媒として用いて、本発明例1と同様な方法で4.2GPa,1300℃で1時間反応させたところ、全体に多量のcBN粒子が生成した。粒子径は約0.5〜0.9mmの比較的大きなcBN粒子であった。
cBNが合成されていることをX線回折により確認した。
図3に、得られたcBNのX線回折チャート(cBNピークが存在する)を示す。
さらに、上記により得られたcBNを原料粉末とし、焼結助剤として、上記金属触媒と同一成分組成からなる混合粉末(Co46.6−Cr31−Mo20−Al2.4wt%)を用い、焼結助剤の含有割合が10体積%となるよう配合した混合粉末(2)を、図2に示すように0.02mm厚さのMo箔で内側を囲んだ外径10mm、内径7mm、高さ7.6mmの食塩(ジルコニア粉末を10wt%含む)成形体(5)間にサンドイッチされるように充填し、圧力5.5GPa、1600℃で1時間焼結した。
得られたcBN焼結体を走査型電子顕微鏡で観察したところ、各cBN粒子間に強固な直接結合を有し、図4に示すように、緻密な焼結組織を有していた。
また、得られたcBN焼結体は、高硬度(Hv:3400)を有していた。
なお、本発明では、cBN焼結体の硬さは、ダイヤモンドペーストを研摩剤として焼結体表面を研摩した後、その表面のヴィッカース硬さ(Hv)を測定することによって求めた。
Invention Example 8:
When a mixture having a component composition of Co46.6-Cr31-Mo20-Al2.4 wt% was used as a metal catalyst, the mixture was reacted at 4.2 GPa and 1300 ° C. for 1 hour in the same manner as in Invention Example 1. A large amount of cBN particles was produced. The particle size was relatively large cBN particles of about 0.5 to 0.9 mm.
It was confirmed by X-ray diffraction that cBN was synthesized.
FIG. 3 shows an X-ray diffraction chart (there is a cBN peak) of the obtained cBN.
Further, the cBN obtained as described above was used as a raw material powder, and a mixed powder (Co46.6-Cr31-Mo20-Al2.4 wt%) having the same composition as that of the metal catalyst was used as a sintering aid. The mixed powder (2) blended so that the content ratio of the agent is 10% by volume is surrounded by a 0.02 mm-thick Mo foil as shown in FIG. 2, and the outer diameter is 10 mm, the inner diameter is 7 mm, and the height is 7. It was filled so as to be sandwiched between 6 mm sodium chloride (containing 10 wt% zirconia powder) compacts (5), and sintered at a pressure of 5.5 GPa and 1600 ° C. for 1 hour.
When the obtained cBN sintered body was observed with a scanning electron microscope, it had a strong direct bond between the cBN particles and had a dense sintered structure as shown in FIG.
Moreover, the obtained cBN sintered body had high hardness (Hv: 3400).
In the present invention, the hardness of the cBN sintered body was obtained by polishing the surface of the sintered body using diamond paste as an abrasive and then measuring the Vickers hardness (Hv) of the surface.

本発明例9:
Fe47.1−Cr34.9−Ni5.24−Mo10−Al2.7wt%からなる成分組成の混合物を金属触媒として用いて、本発明例1と同様な方法で4.2GPa,1300℃で1時間反応させたところ、全体に多量のcBN粒子が生成した。平均粒子径は約0.5mmのcBN粒子であった。
Invention Example 9:
Using a mixture of component composition consisting of Fe47.1-Cr34.9-Ni5.24-Mo10-Al2.7 wt% as a metal catalyst, reaction was conducted at 4.2 GPa and 1300 ° C. for 1 hour in the same manner as in Example 1 of the present invention. As a result, a large amount of cBN particles was generated as a whole. The average particle size was cBN particles of about 0.5 mm.

本発明例10:
Fe34−Co17−Cr32.4−Mo14.2−Al2.4wt%からなる成分組成の混合物を金属触媒として用いて、本発明例1と同様な方法で4.2GPa,1300℃で1時間反応させたところ、全体に多量のcBN粒子が生成した。平均粒子径は約0.3mmのcBN粒子であった。
Invention Example 10:
Using a mixture of component composition consisting of Fe34-Co17-Cr32.4-Mo14.2-Al2.4 wt% as a metal catalyst, the mixture was reacted at 4.2 GPa at 1300 ° C. for 1 hour in the same manner as in Example 1 of the present invention. However, a large amount of cBN particles was generated overall. The average particle diameter was cBN particles of about 0.3 mm.

本発明例11:
Co48.7−Cr16.2−Mo32.4−Al12.7wt%からなる成分組成の混合物を金属触媒として用いて、本発明例1と同様な方法で4.2GPa,1300℃で1時間反応させたところ、全体に多量のcBN粒子が生成した。平均粒子径は約0.3mmのcBN粒子であった。本実施例は特にCrに対して、Moが過剰な成分を選択したために、Crが過剰な成分を有する触媒に比べて、若干cBNの収率が低下していた。
Invention Example 11:
Co 48.7-Cr16.2-Mo32.4-Al 12.7 wt% of the composition of the component composition was used as a metal catalyst, and reacted at 4.2 GPa and 1300 ° C. for 1 hour in the same manner as in Example 1 of the present invention. However, a large amount of cBN particles was generated overall. The average particle diameter was cBN particles of about 0.3 mm. In this example, since a component having an excessive amount of Mo with respect to Cr was selected, the yield of cBN was slightly reduced as compared with a catalyst having an excessive component of Cr.

本発明例12:
Co38.5−Fe19.2−Cr28.8−Mo9.61−Al3.85wt%からなる成分組成の混合粉末を金属触媒として用い、本発明例1と同様な方法で、4.4GPa、1413℃で1時間反応させたところ、80%以上のhBNが均質な約0.1〜0.2mmのcBN粒子に転換していた。
Invention Example 12:
Co 38.5-Fe 19.2-Cr 28.8-Mo 9.61-Al 3.85 wt% mixed powder having a component composition was used as a metal catalyst in the same manner as in Example 1 of the present invention at 4.4 GPa at 1413 ° C. When reacted for 1 hour, 80% or more of hBN was converted into homogeneous cBN particles of about 0.1 to 0.2 mm.

比較例4:
本発明例12の上記金属触媒において、MoとCrの含有割合を増加し、Co18.2−Fe19.2−Cr28.3−Mo31.2−Al3.1wt%からなる成分組成の混合粉末からなる金属触媒を作製し、本発明例12と同様に、4.4GPa、1413℃で1時間反応させたところ、cBNは生成しなかった。CrとMoの合計含有割合が55wt%以上であるため、金属触媒の融点が高くなったことによるものと考えられる。ちなみに、この処理条件はcBNが安定な領域内と考えられる。
よって、CrとMoの合計含有割合を55wt%以下にすることが必要である。
Comparative Example 4:
In the above metal catalyst of Invention Example 12, the content of Mo and Cr is increased, and the metal is composed of a mixed powder having a component composition of Co18.2—Fe19.2—Cr28.3—Mo31.2—Al3.1 wt%. When a catalyst was prepared and reacted at 4.4 GPa and 1413 ° C. for 1 hour as in Inventive Example 12, cBN was not produced. Since the total content ratio of Cr and Mo is 55 wt% or more, it is considered that the melting point of the metal catalyst is increased. Incidentally, this processing condition is considered to be in a region where cBN is stable.
Therefore, it is necessary to make the total content ratio of Cr and Mo 55% by weight or less.

本発明例13:
Co20−Fe40−Cr38−Al2wt%からなる成分組成の混合粉末を金属触媒として用い、本発明例1と同様な方法で、4.4GPa、1400℃で1時間、また、4.2GPa、1340℃で1時間反応させたところ、70%以上のhBNがcBN粒子に転換していた。
Invention Example 13:
Using a mixed powder having a component composition of Co20-Fe40-Cr38-Al2 wt% as a metal catalyst, in the same manner as in Example 1 of the present invention, at 4.4 GPa and 1400 ° C. for 1 hour, and at 4.2 GPa and 1340 ° C. When reacted for 1 hour, 70% or more of hBN was converted to cBN particles.

上記本発明例1〜13及び比較例1〜4を表にまとめると、表1の通りとなる。   The invention examples 1 to 13 and comparative examples 1 to 4 are summarized in the table as shown in Table 1.

Figure 2010235369
Figure 2010235369

上記のとおり、本発明のcBN合成方法およびcBNを原料粉末とするcBN焼結体の製造方法によれば、金属触媒として、Nを溶解する作用を有する15wt%以上55wt%以下のCr,Mo(但し、Moは、15wt%≦(Cr+Mo)≦55wt%、かつ、Mo≦10wt%を満足する)と、cBN核発生・成長の促進・助長作用を有する1.5〜8wt%のAl,Mgと、残部はBを溶解する作用を有するFe,Co,Ni(但し、Niは、22wt%以下)からなる合金粉末あるいは混合粉末を用いることによって、従来よりも低圧力範囲(最低圧力4GPa)でcBNを合成することができ、また、上記金属触媒と同一成分組成の焼結助剤を用いた焼結により、cBN粒子間で強固な直接結合を有し、緻密な組織を備え高硬度を有するBN焼結体を製造することができる。   As described above, according to the cBN synthesis method of the present invention and the cBN sintered body production method using cBN as a raw material powder, 15 wt% or more and 55 wt% or less of Cr, Mo (having an action of dissolving N as a metal catalyst ( However, Mo satisfies 15 wt% ≦ (Cr + Mo) ≦ 55 wt% and Mo ≦ 10 wt%), and 1.5 to 8 wt% Al, Mg having cBN nucleation / growth promotion / promotion effect The balance is cBN in a lower pressure range (minimum pressure 4 GPa) by using an alloy powder or mixed powder made of Fe, Co, Ni (where Ni is 22 wt% or less) having an action of dissolving B. In addition, sintering using a sintering aid having the same composition as that of the metal catalyst has a strong direct bond between the cBN particles, and has a dense structure and high hardness. It is possible to produce a BN sintered body having.

1,11 :グラファイトヒーター
2 :Mo箔
3 :金属触媒
4 :hBN
5,15 :NaCl−10wt%ZrO
12 :cBN+焼結助剤(=金属触媒)
13 :Mo箔
14 :WC/Co
1, 11: Graphite heater 2: Mo foil 3: Metal catalyst 4: hBN
5,15: NaCl-10 wt% ZrO 2
12: cBN + sintering aid (= metal catalyst)
13: Mo foil 14: WC / Co

Claims (6)

金属触媒の存在下、超高圧高温条件で六方晶窒化ホウ素から立方晶窒化ホウ素を合成する立方晶窒化ホウ素の合成方法において、上記金属触媒は、15wt%以上55wt%以下のCrと、1.5〜8wt%のAl及びMgのいずれか1種又は2種と、残部はFe及びCoのいずれか1種又は2種の成分組成からなる合金粉末あるいは混合粉末であって、さらに、上記合成を、4GPa以上、1200〜1900℃で行うことを特徴とする立方晶窒化ホウ素の合成方法。   In the method of synthesizing cubic boron nitride in which cubic boron nitride is synthesized from hexagonal boron nitride under ultrahigh pressure and high temperature conditions in the presence of a metal catalyst, the metal catalyst contains 15 wt% or more and 55 wt% or less of Cr, 1.5 -8 wt% of any one or two of Al and Mg, and the balance is an alloy powder or mixed powder composed of any one or two component compositions of Fe and Co. A method for synthesizing cubic boron nitride, which is performed at 4 GPa or more and 1200 to 1900 ° C. 上記金属触媒が、22wt%以下のNiを更に含有することを特徴とする請求項1に記載の立方晶窒化ホウ素の合成方法。   The method for synthesizing cubic boron nitride according to claim 1, wherein the metal catalyst further contains 22 wt% or less of Ni. 上記金属触媒が、15wt%≦(Cr+Mo)≦55wt%を満足するMoを更に含有することを特徴とする請求項1または2に記載の立方晶窒化ホウ素の合成方法。   3. The method for synthesizing cubic boron nitride according to claim 1, wherein the metal catalyst further contains Mo satisfying 15 wt% ≦ (Cr + Mo) ≦ 55 wt%. 立方晶窒化ホウ素を原料粉末とし、該原料粉末に焼結助剤を添加して焼結することからなる立方晶窒化ホウ素焼結体の製造方法において、上記焼結助剤として、15wt%以上55wt%以下のCrと、1.5〜8wt%のAl及びMgのいずれか1種又は2種と、残部はFe及びCoのいずれか1種又は2種の成分組成からなる合金粉末あるいは混合粉末を、原料粉末に5〜10体積%添加して焼結することを特徴とする立方晶窒化ホウ素焼結体の製造方法。   In the method for producing a cubic boron nitride sintered body, comprising cubic boron nitride as a raw material powder, adding a sintering aid to the raw material powder and sintering, the sintering aid is 15 wt% or more and 55 wt% % Or less of Cr, 1.5-8 wt% of any one or two of Al and Mg, and the balance is an alloy powder or mixed powder composed of one or two of Fe and Co. A method for producing a cubic boron nitride sintered body, comprising adding 5 to 10% by volume to a raw material powder and sintering. 上記焼結助剤が、22wt%以下のNiを更に含有することを特徴とする請求項4に記載の立方晶窒化ホウ素焼結体の製造方法。   The method for producing a cubic boron nitride sintered body according to claim 4, wherein the sintering aid further contains 22 wt% or less of Ni. 上記焼結助剤が、15wt%≦(Cr+Mo)≦55wt%を満足するMoを更に含有することを特徴とする請求項4または5に記載の立方晶窒化ホウ素焼結体の製造方法。   6. The method for producing a cubic boron nitride sintered body according to claim 4, wherein the sintering aid further contains Mo satisfying 15 wt% ≦ (Cr + Mo) ≦ 55 wt%.
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