JP5182582B2 - Method for synthesizing cubic boron nitride and method for producing sintered cubic boron nitride - Google Patents
Method for synthesizing cubic boron nitride and method for producing sintered cubic boron nitride Download PDFInfo
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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 cBN sintering using the synthesized cBN as a raw 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Ｌｉ３ＢＮ２）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-Al1 wt%, Ni39.2-Mn58.8-Al2wt%, Ni49-Cr49-Al2wt%, Fe8-Ni43-Cr47-Al2wt%, 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、ＮｉＡｌ３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。
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 coexisted 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.
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、Ｃｏ，Ｎｉ，Ｆｅ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 synthesizing cBN from hBN, conventionally, a metal catalyst comprising a transition metal such as Co, Ni, Fe and an alloy or a mixture of Al was used. 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, pressure conditions of 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、Ｃｏ，Ｎｉ，Ｆｅ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。
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Ｍｏを含有させると、液相状態において、Ｍｏ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。
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Ｍｏ成分と、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，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。
By the way, with regard to conventionally used metal catalysts, when the action of the catalyst component is viewed from the above viewpoint, transition metals such as Co, Ni, and Fe 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.
Therefore, the present inventors conducted research on a metal catalyst that has an excellent ability to dissolve N and at the same time promotes and promotes nucleation / growth of cBN even under low-pressure conditions. When contained, Mo 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.
That is, as a metal catalyst for synthesizing cBN from hBN, a Mo component having an action of dissolving N, an Al and Mg components having an action of promoting and promoting cBN nucleus generation / growth, and the remainder dissolves B. By using an alloy powder or mixed powder composed of Fe, Co, and Ni components having an action, the synthesis minimum pressure can be reduced to 4 GPa, and as a result, it has been found that cBN can be synthesized in a lower pressure range than in the past. It was.
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（ｈＢＮ）から立方晶窒化ホウ素（ｃＢＮ）を合成する立方晶窒化ホウ素（ｃＢＮ）の合成方法において、上記金属触媒は、１５ｗｔ％以上５０ｗｔ％未満のＭｏ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，Ｃｏ及びＮｉのうちから選ばれる１種又は２種以上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、４〜５ＧＰａ、１２００〜１９００℃で行うことを特徴とする立方晶窒化ホウ素（ｃＢＮ）の合成方法。
（２） 前記（１）に記載された立方晶窒化ホウ素の合成方法で合成された立方晶窒化ホウ素（ｃＢＮ）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（ｃＢＮ）焼結体の製造方法において、焼結助剤として、１５ｗｔ％以上５０ｗｔ％未満のＭｏ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，Ｃｏ及びＮｉのうちから選ばれる１種又は２種以上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（ｃＢＮ）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 (cBN) in which cubic boron nitride (cBN) is synthesized from hexagonal boron nitride (hBN) under ultrahigh pressure and high temperature conditions in the presence of a metal catalyst, the metal catalyst is 15 wt% or more and less than 50 wt% Mo, 1.5 to 8 wt% of any one or two of Al and Mg, and the balance is one or more components selected from Fe, Co and Ni A method for synthesizing cubic boron nitride (cBN), which is an alloy powder or a mixed powder having a composition, and further comprising performing the synthesis at 4 to 5 GPa and 1200 to 1900 ° C.
(2) Cubic boron nitride (cBN) synthesized by the method for synthesizing cubic boron nitride described in (1) above is used as a raw material powder, and a sintering aid is added to the raw material powder for sintering. In a method for producing a cubic boron nitride (cBN) sintered body comprising, as a sintering aid, Mo of 15 wt% or more and less than 50 wt%, and any one or two of Al and Mg of 1.5 to 8 wt% The seed and the balance are sintered by adding 5 to 10% by volume of an alloy powder or mixed powder composed of one or more components selected from Fe, Co and Ni to the raw material powder. A method for producing a cubic boron nitride (cBN) sintered body. ".
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：
金属触媒は、１５ｗｔ％以上５０ｗｔ％未満のＭｏ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，Ｃｏ及びＮｉのうちから選ばれる１種又は２種以上からなる合金粉末あるいは混合粉末として形成される。
Ｍｏ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、Ｍｏ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、Ｍｏ成分の含有割合が５０ｗｔ％以上になると、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Ｍｏ成分の含有割合は１５ｗｔ％以上５０ｗｔ％未満、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，Ｃｏ及びＮｉのうちから選ばれる１種又は２種以上の成分は、Ｆｅ，Ｃｏ及びＮｉ夫々単独でも、また、これらを２種以上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:
The metal catalyst is 15 wt% or more and less than 50 wt% Mo, 1.5 to 8 wt% of any one or two of Al and Mg, and the balance is one or two selected from Fe, Co and Ni It is formed as an alloy powder or mixed powder composed of more than seeds.
Mo 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 Mo component content is less than 15 wt%, the amount of dissolved N is small, so that sufficient cBN is generated. On the other hand, when the content ratio of the Mo component is 50 wt% or more, 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 Mo component having an action of dissolving the water was determined to be 15 wt% or more and less than 50 wt%, 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.
One or two or more components selected from Fe, Co and Ni can be used to melt the B of raw material hBN even when each of Fe, Co and Ni is used alone or in combination of two or more of them. It has the action of dissolving in a state (liquid phase) metal catalyst.
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).
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℃以上は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):
The synthesis from hBN to cBN is performed, for example, by placing hBN, which is a raw material for synthesis, and the above-mentioned metal catalyst powder in the synthesis apparatus shown in FIG. 1, at a pressure of 4 GPa or more and at a temperature of 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 cBN synthesis reaction 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 reversely converted 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、ＮｉＡｌ３、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、Ｃｏ５７．６−Ｍｏ３８．４−Ａｌ４ｗｔ％の成分組成のＣｏ−Ｍｏ−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−Ｍｏ−Ａｌ系合金を焼結助剤として用い、焼結助剤の含有割合が、６．９体積％となるように配合し、これを図２に示す焼結装置で、５．０ＧＰａ×１９００℃の条件で焼結することによってｃＢＮ焼結体を製造した。得られたｃＢＮ焼結体の走査型電子顕微鏡写真による組織及びこのｃＢＮ焼結体について測定したヴィッカース硬さ（Ｈｖ）を図３に示す。
図３から、本発明の製造法で製造されたｃＢＮ焼結体は、非常に緻密な組織を有し、かつ、極めて高い硬度（Ｈｖ：４０００）を有することが分かる。
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, synthesis was performed by the synthesis method of the present invention using the synthesis apparatus shown in FIG. 1 (using a Co-Mo-Al-based metal catalyst having a component composition of Co57.6-Mo38.4-Al4 wt% as the metal catalyst). Using cBN powder as a raw material powder, using a Co—Mo—Al alloy having the same composition as the metal catalyst as a sintering aid, the content of the sintering aid is 6.9% by volume. Then, this was sintered by a sintering apparatus shown in FIG. 2 under the condition of 5.0 GPa × 1900 ° C. to produce a cBN sintered body. FIG. 3 shows the structure of the obtained cBN sintered body according to a scanning electron micrograph and the Vickers hardness (Hv) measured for the cBN sintered body.
FIG. 3 shows that the cBN sintered body produced by the production method of the present invention has a very dense structure and extremely high hardness (Hv: 4000).
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.
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.
図１に示すように、金属触媒として、Ｃｏ５７．６−Ｍｏ３８．４−Ａｌ４ｗｔ％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４．４ＧＰａ、１３００℃で２時間反応させた試料には、約５０%のｃＢＮ粒子が含まれており、ｈＢＮ板の中間に配置したＣｏ５７．６−Ｍｏ３８．４−Ａｌ４ｗｔ％の成分組成の合金粉末は完全に溶解した形跡があり、大部分は原料ｈＢＮを配置した層内に吸収されていた。
次いで、合成された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合金粉末（Ｃｏ５７．６−Ｍｏ３８．４−Ａｌ４ｗｔ％）を用い、焼結助剤の含有割合が６．９体積％となるよう配合した混合粉末（１２）を作製し、図２に示すように、内面にＭｏ箔（１３）を配置した容器内に、作製された混合粉末と超硬合金成形体（１４）とを、食塩（ジルコニア粉末を１０ｗｔ％含む）成形体（１５）間にサンドイッチされるように充填し、圧力５．０ＧＰａ、１９００℃で０．５時間焼結した。なお、グラファイト管状ヒーター（１１）で囲まれている。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、ｃＢＮ焼結体は、各ｃＢＮ粒子間に強固な直接結合を有し、図３に示すように、緻密な焼結組織であって高硬度（Ｈｖ：４０００）を有していた。
As shown in FIG. 1, as a metal catalyst, an alloy powder having a component composition of Co57.6-Mo38.4-Al4 wt% is prepared in advance, and 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 device (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.
The sample reacted at a pressure of 4.4 GPa and 1300 ° C. for 2 hours contains about 50% cBN particles, and has a component composition of Co57.6-Mo38.4-Al4 wt% disposed in the middle of the hBN plate. The alloy powder had a trace of complete dissolution, and most of the alloy powder was absorbed in the layer in which the raw material hBN was arranged.
Next, the synthesized cBN is used as a raw material powder, and an alloy powder (Co57.6-Mo38.4-Al4 wt%) having the same composition as the metal catalyst is used as a sintering aid, and the content ratio of the sintering aid There was prepared a mixed powder obtained by blending so as to be 6.9 vol% (12), as shown in Figure 2, the vessel was placed Mo foil (13) on the inner surface, carbide and fabricated mixed powder The alloy compact (14) was filled so as to be sandwiched between sodium chloride (containing 10 wt% zirconia powder) compact (15), and sintered at a pressure of 5.0 GPa and 1900 ° C. for 0.5 hour. It is surrounded by a graphite tubular heater (11). When the obtained cBN sintered body was observed with a scanning electron microscope, the cBN sintered body had a strong direct bond between each cBN particle and had a dense sintered structure as shown in FIG. And had a high hardness (Hv: 4000).
実施例１と同じ試料を用いて、圧力４．５ＧＰａ、温度１４１０℃で９０分間反応させた後、試料を回収した。
原料ｈＢＮの約７０％以上がｃＢＮに変化しており、実施例1と同じく、ｈＢＮ板の中間に配置したＣｏ５７．６−Ｍｏ３８．４−Ａｌ４ｗｔ％の成分組成の合金粉末は完全に溶解した形跡があり、大部分は原料ｈＢＮを配置した層内に吸収されていた。溶解した金属成分はｈＢＮ層を完全に通り抜けて、ｈＢＮ原料層全体に約０．３ｍｍ程度のｃＢＮ粒子が詰まり、その間隙にわずかに未反応のｈＢＮが観察された。
Using the same sample as in Example 1, the sample was recovered after reacting at a pressure of 4.5 GPa and a temperature of 1410 ° C. for 90 minutes.
About 70% or more of the raw material hBN is changed to cBN, and the alloy powder of the component composition of Co57.6-Mo38.4-Al4 wt% disposed in the middle of the hBN plate is completely dissolved as in Example 1. Most of them were absorbed in the layer in which the raw material hBN was arranged. The dissolved metal component completely passed through the hBN layer, cBN particles of about 0.3 mm were clogged in the entire hBN raw material layer, and slightly unreacted hBN was observed in the gap.
また、実施例１と同じ試料を用い、圧力を５ＧＰａ、温度を１３００℃とした同様の実験を行い、Ｘ線回折により、ｃＢＮが合成されていることを確認した。
Ｘ線回折を行って得たＸ線回折チャートを図４として示すが、ｃＢＮピークの存在から、ｃＢＮが合成されていることは明らかである。
さらに、実施例１と同じ試料を用いて、種々の圧力、温度でｃＢＮ焼結体を製造した。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、ｃＢＮ焼結体は、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していた。また、各ｃＢＮ焼結体について測定したヴィッカース硬さ（Ｈｖ）を表１に示す。
ここで、Ｘ線回折は、ブルカー製ＡＸＳＭＸＰ１８ＶＡＨＦにより測定し、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）を測定した。
Further, using the same sample as in Example 1, a similar experiment was performed at a pressure of 5 GPa and a temperature of 1300 ° C., and it was confirmed that cBN was synthesized by X-ray diffraction.
An X-ray diffraction chart obtained by performing X-ray diffraction is shown in FIG. 4, and it is clear that cBN is synthesized from the presence of the cBN peak.
Further, cBN sintered bodies were produced using the same sample as in Example 1 at various pressures and temperatures. When the obtained cBN sintered body was observed with a scanning electron microscope, the cBN sintered body had a strong direct bond between the cBN particles and had a dense sintered structure. In addition, Table 1 shows the Vickers hardness (Hv) measured for each cBN sintered body.
Here, X-ray diffraction is measured by Bruker AXSMXP18VAHF, and the hardness of the cBN sintered body is measured by polishing the surface of the sintered body using diamond paste as an abrasive and then measuring the Vickers hardness (Hv) of the surface. did.
実施例１と同じ試料を用いて、圧力４．７ＧＰａ、温度１４３６℃で１時間反応させた後、試料を回収した。原料ｈＢＮのほぼ１００%がｃＢＮに変化していた。 Using the same sample as in Example 1, the sample was recovered after reacting at a pressure of 4.7 GPa and a temperature of 1436 ° C. for 1 hour. Almost 100% of the raw material hBN was changed to cBN.
Ｃｏ６０−Ｍｏ４０ｗｔ％の成分組成の合金粉末をまず調整して、それに対して４ｗｔ％の含有割合になるようにＡｌを添加したＣｏ５７．６−Ｍｏ３８．４−Ａｌ４ｗｔ％組成の混合粉末からなる金属触媒を用いて、６ＧＰａ、１７５０℃で２０分間反応させたところ、試料中のｈＢＮはほぼ１００％ｃＢＮに変化していた。 A metal catalyst comprising a mixed powder of Co57.6-Mo38.4-Al4 wt% composition in which an alloy powder having a component composition of Co60-Mo40 wt% was first prepared and Al was added so as to have a content ratio of 4 wt% with respect to the alloy powder. When the reaction was performed at 6 GPa and 1750 ° C. for 20 minutes, hBN in the sample was changed to almost 100% cBN.
実施例４と同じＣｏ６０−Ｍｏ４０ｗｔ％の成分組成の合金粉末に対して、１．５ｗｔ％の含有割合になるようにＡｌを添加した混合粉末からなる金属触媒を用いて、実施例４と同じ６ＧＰａ、１７５０℃で２５分間反応させた試料の状況を調べたところ、金属触媒層は収縮が大きくかなりの部分が原料ｈＢＮに吸収されていて、ｃＢＮの収率は約７０％であった。 The same 6 GPa as in Example 4 by using a metal catalyst made of a mixed powder in which Al was added so as to have a content ratio of 1.5 wt% with respect to the alloy powder having the same composition as Co60-Mo 40 wt% as in Example 4. When the condition of the sample reacted at 1750 ° C. for 25 minutes was examined, the metal catalyst layer was greatly contracted and a considerable portion was absorbed by the raw material hBN, and the yield of cBN was about 70%.
一方、実施例４と同じＣｏ６０−Ｍｏ４０ｗｔ％の成分組成の合金粉末に対して、０．５ｗｔ％の含有割合になるようにＡｌを添加した混合粉末からなる金属触媒を用いて、実施例４と同じ６ＧＰａ、１７５０℃で３０分間反応させたところ、試料の金属触媒層は原料ｈＢＮ層と固着しておらず、金属触媒層の変形もわずかであった。
また、Ｘ線回折を行ったところ、図５のＸ線回折チャートに示されるように、ｈＢＮの回折ピークが存在するもののｃＢＮの回折ピークはみられず、ｃＢＮへの転換が生じていないことがわかる。
On the other hand, Example 4 and Example 4 were performed using a metal catalyst made of a mixed powder obtained by adding Al so that the content ratio was 0.5 wt% with respect to the alloy powder having the same Co60-Mo 40 wt% composition as in Example 4. When the same reaction was performed at 6 GPa and 1750 ° C. for 30 minutes, the sample metal catalyst layer was not fixed to the raw material hBN layer, and the deformation of the metal catalyst layer was slight.
Further, when X-ray diffraction was performed, as shown in the X-ray diffraction chart of FIG. 5, although there was a diffraction peak of hBN, no diffraction peak of cBN was observed, and conversion to cBN did not occur. Recognize.
上記実施例５と比較例１の結果からみると、Ｃｏ６０−Ｍｏ４０ｗｔ％の成分組成の合金粉末に対して、Ａｌの含有割合が１．５ｗｔ%以上になるように添加含有させたＣｏ−Ｍｏ−Ａｌ系金属触媒を用いることによって、効果的な触媒効果が出現することを確認できた。
したがって、金属触媒におけるＡｌ含有割合は、少なくとも１．５ｗｔ％以上必要であることがわかる。
From the results of Example 5 and Comparative Example 1, Co—Mo— was added and contained so that the Al content ratio was 1.5 wt% or more with respect to the alloy powder having a component composition of Co 60 —Mo 40 wt%. It was confirmed that an effective catalytic effect appeared by using an Al-based metal catalyst.
Therefore, it can be seen that the Al content in the metal catalyst needs to be at least 1.5 wt% or more.
Ｃｏ８１．６−Ｍｏ１４．４−Ａｌ４ｗｔ％の成分組成の混合粉末を金属触媒として用いて、４．７ＧＰａ、１４８０℃で１時間反応させた試料を調べたところ、一部に微細なｃＢＮ粒子が析出していたが、その収率は約２０%以下にすぎなかった。 Using a mixed powder having a component composition of Co81.6-Mo14.4-Al4 wt% as a metal catalyst, a sample reacted at 4.7 GPa and 1480 ° C. for 1 hour was examined, and fine cBN particles were partially precipitated. However, the yield was only about 20% or less.
上記実施例１〜５の結果と、比較例２の結果の比較から、金属触媒におけるＭｏ含有割合が少ない場合には、ｃＢＮへの変換反応の触媒効果は低下することがわかる。
したがって、金属触媒においては、少なくとも１５ｗｔ％以上のＭｏが含有されていることが必要である。
From the comparison of the results of Examples 1 to 5 and the result of Comparative Example 2, it can be seen that when the Mo content in the metal catalyst is small, the catalytic effect of the conversion reaction to cBN is reduced.
Therefore, the metal catalyst needs to contain at least 15 wt% of Mo.
Ｃｏ９６−Ａｌ４ｗｔ％の成分組成（すなわち、実施例１〜７と異なり、Ｍｏ成分を全く含まない）の金属触媒を用いて、実施例１と同様な方法で、４．８ＧＰａ、１４３６℃で１時間反応させたところ、試料からはｃＢＮが全く検出されなかった。
同様に、上記の金属触媒（すなわち、Ｍｏ成分を全く含まないＣｏ９６−Ａｌ４ｗｔ％の成分組成）を用いて、実施例１と同様な方法で、５．５ＧＰａ、１４４０℃で１時間反応させた場合にも、試料からはｃＢＮが全く検出されなかった。
そこで、合成圧力及び合成温度を高め、６．２ＧＰａ、１６００℃で４０分間反応させた反応物、及び、６ＧＰａ、１６５０℃で５０分間反応させた反応物についてｃＢＮ生成の有無を調べたところ、多量のｃＢＮが検出された。
Using a metal catalyst having a component composition of Co 96-Al 4 wt% (that is, unlike the examples 1 to 7 and containing no Mo component), the same method as in the example 1 was performed at 4.8 GPa and 1436 ° C. for 1 hour. When reacted, no cBN was detected from the sample.
Similarly, when the above metal catalyst (that is, a component composition of Co96-Al4 wt% containing no Mo component) is used and reacted at 5.5 GPa and 1440 ° C. for 1 hour in the same manner as in Example 1. In addition, no cBN was detected from the sample.
Therefore, when the synthesis pressure and the synthesis temperature were increased and the reaction product reacted at 6.2 GPa and 1600 ° C. for 40 minutes and the reaction product reacted at 6 GPa and 1650 ° C. for 50 minutes were examined for the presence or absence of cBN formation. Of cBN was detected.
上記比較例３の結果から、Ｍｏを全く含まない金属触媒（Ｃｏ−Ａｌ合金）を用いた場合には、ｃＢＮの最低合成圧力は約６ＧＰａであって、ｃＢＮを合成するためには超高圧が必要とされることがわかる。
しかし、実施例１〜５からも明らかなように、Ｍｏを１５ｗｔ％以上５０ｗｔ％未満の範囲内で含有する本発明の金属触媒を用いた場合（実施例１〜５）には、ｃＢＮの最低合成圧力を４ＧＰａにまで低減することができ、本発明によれば、低圧力範囲でｃＢＮを合成できることが確認された。
From the results of Comparative Example 3, when a metal catalyst containing no Mo (Co—Al alloy) is used, the minimum synthesis pressure of cBN is about 6 GPa, and an ultrahigh pressure is required to synthesize cBN. You can see that it is needed.
However, as is clear from Examples 1 to 5, when the metal catalyst of the present invention containing Mo in a range of 15 wt% or more and less than 50 wt% is used (Examples 1 to 5), the minimum of cBN The synthesis pressure can be reduced to 4 GPa, and according to the present invention, it was confirmed that cBN can be synthesized in a low pressure range.
ｃＢＮ核発生・成長の促進・助長成分であるＭｇ成分を含有する金属触媒として、Ｃｏ５８．２−Ｍｏ３８．８−Ｍｇ３ｗｔ％の成分組成の混合粉末を用いて（即ち、実施例１〜５におけるｃＢＮ核発生促進・助長作用を有するＡｌ成分に代えてＭｇを用いる）、実施例１と同様な試料構成によって、４．２ＧＰａ、１３７０℃で１時間反応させたところ、金属触媒層付近の一部分に非常に微細なｃＢＮ粒子の析出が観察された。
このことから、ＭｇはＡｌと同様に、ｃＢＮの核発生・成長を促進・助長する作用を有し、金属触媒におけるＭｇの含有割合が１．５〜８ｗｔ％の範囲内であれば、ｃＢＮの核発生・成長を促進・助長する作用は効果的に発揮されることがわかる。
さらに、ｃＢＮ核発生・成長の促進・助長成分として、ＡｌとＭｇを併用した場合にも、両者の含有割合の合計量が１．５〜８ｗｔ％の範囲内であれば、ｃＢＮの核発生・成長を促進・助長する作用は十分に発揮されることを確認した。
As a metal catalyst containing the Mg component which is a component for promoting and promoting the generation of cBN nuclei, a mixed powder having a component composition of Co 58.2-Mo 38.8-Mg 3 wt% was used (that is, the cBN in Examples 1 to 5). (Mg is used in place of the Al component that promotes and promotes nucleation), and the sample was reacted at 4.2 GPa and 1370 ° C. for 1 hour using the same sample configuration as in Example 1. Precipitation of fine cBN particles was observed.
From this, Mg, like Al, has the effect of promoting / promoting cBN nucleation / growth, and if the Mg content in the metal catalyst is in the range of 1.5 to 8 wt%, It can be seen that the action of promoting and promoting nucleation and growth is effectively exhibited.
Furthermore, even when Al and Mg are used together as components for promoting and promoting cBN nucleation / growth, if the total content of both is within the range of 1.5 to 8 wt%, It was confirmed that the effect of promoting and promoting growth was fully demonstrated.
Ｂを溶解する作用を有する成分であるＦｅ成分を含有する金属触媒として、Ｆｅ６０．１４−Ｍｏ３６．８６−Ａｌ３ｗｔ％の成分組成を持つ混合粉末を用意し、実施例１に述べたと同じ方法で、４．４ＧＰａ、１３００℃で１時間反応させて、生成物を調べたところ、およそ０．３〜０．５ｍｍの比較的大きなサイズのｃＢＮ粒子が生成していた。
上記金属触媒を用い、合成条件を変更し、５．８ＧＰａ、１４５０℃で1時間反応させたところ、合成されたｃＢＮは上記の場合よりもはるかに細かいｃＢＮ粒子から構成されていた。
また、４．４ＧＰａ、１４５０℃で１時間反応させてｃＢＮの析出状況を調べたところ、金属触媒との界面付近に少量のｃＢＮ粒子が析出していることから、４．４ＧＰａがこの金属触媒を使用したときのｃＢＮ合成の最低圧力条件であることが確認された。
さらに、上記で合成されたｃＢＮを原料粉末とし、上記金属触媒と同一成分組成の混合粉末を焼結助剤として用い、種々の圧力（４．０〜６．０ＧＰａ）、温度（１２００〜２０００℃）でｃＢＮ焼結体を製造し、得られたｃＢＮ焼結体の組織を観察し、また、焼結体のヴィッカース硬さ（Ｈｖ）を測定した。
得られたｃＢＮ焼結体の組織は、実施例２の場合と同様であり、ｃＢＮ焼結体は、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していた。
また、各ｃＢＮ焼結体について測定したヴィッカース硬さ（Ｈｖ）を表２に示す。
As a metal catalyst containing an Fe component which is a component having an action of dissolving B, a mixed powder having a component composition of Fe60.14-Mo36.86-Al3 wt% was prepared, and in the same manner as described in Example 1, When the product was examined by reacting at 4.4 GPa and 1300 ° C. for 1 hour, cBN particles having a relatively large size of approximately 0.3 to 0.5 mm were formed.
When the synthesis conditions were changed using the metal catalyst and reacted at 5.8 GPa and 1450 ° C. for 1 hour, the synthesized cBN was composed of much finer cBN particles than the above case.
Moreover, when the precipitation state of cBN was investigated by reacting at 4.4 GPa and 1450 ° C. for 1 hour, a small amount of cBN particles were deposited near the interface with the metal catalyst, so that 4.4 GPa It was confirmed that this was the minimum pressure condition for cBN synthesis when used.
Furthermore, cBN synthesized above is used as a raw material powder, and a mixed powder having the same component composition as that of the metal catalyst is used as a sintering aid, and various pressures (4.0 to 6.0 GPa) and temperatures (1200 to 2000 ° C.). CBN sintered body was manufactured, the structure of the obtained cBN sintered body was observed, and the Vickers hardness (Hv) of the sintered body was measured.
The structure of the obtained cBN sintered body was the same as that in Example 2, and the cBN sintered body had a strong direct bond between each cBN particle and had a dense sintered structure. .
In addition, Table 2 shows the Vickers hardness (Hv) measured for each cBN sintered body.
Ｂを溶解する作用を有する成分であるＮｉ成分を含有する金属触媒として、Ｎｉ７６−Ｍｏ２０−Ａｌ４ｗｔ％の成分組成を持つ混合粉末を用意し、実施例１に述べたと同じ方法で、４．８ＧＰａ、１５４４０℃において１時間反応させたところ、約６０％のｈＢＮ原料が微粒ｃＢＮ結晶に変換していた。 As a metal catalyst containing a Ni component, which is a component having an action of dissolving B, a mixed powder having a component composition of Ni76-Mo20-Al4 wt% is prepared, and 4.8 GPa in the same manner as described in Example 1; When the reaction was carried out at 15440 ° C. for 1 hour, about 60% of the hBN raw material was converted to fine cBN crystals.
上記のとおり、本発明のｃＢＮ合成方法および合成したｃＢＮを原料粉末とした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Ｍｏ１５ｗｔ％以上５０ｗｔ％未満と、ｃＢＮ核発生・成長の促進・助長作用を有するＡｌ及びＭｇのいずれか１種又は２種１．５〜８ｗｔ％と、残部はＢを溶解する作用を有するＦｅ，Ｃｏ及びＮｉのうちから選ばれる１種又は２種以上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 the synthesized cBN as a raw material powder, Mo15 wt% or more and less than 50 wt% having an action of dissolving N as a metal catalyst, cBN One or two of 1.5 and 8 wt% of Al and Mg having nucleation / growth promotion / promoting action, and the balance is selected from Fe, Co and Ni having the action of dissolving B CBN can be synthesized in a lower pressure range (minimum pressure 4 GPa) than before by using an alloy powder or mixed powder of seeds or two or more, and sintering aids having the same component composition as the above metal catalyst. By sintering using an agent, a BN sintered body having a strong direct bond between cBN particles, a dense structure, and high hardness can be produced.
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％ＺｒＯ２
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
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