JP3885293B2

JP3885293B2 - Diamond indenter

Info

Publication number: JP3885293B2
Application number: JP16891697A
Authority: JP
Inventors: 均角谷
Original assignee: Sumitomo Electric Industries Ltd
Current assignee: Sumitomo Electric Industries Ltd
Priority date: 1997-06-25
Filing date: 1997-06-25
Publication date: 2007-02-21
Anticipated expiration: 2017-06-25
Also published as: JPH1114524A

Description

【０００１】
【発明の属する技術分野】
本発明は、ダイヤモンド圧子に関するもので、特に高硬度で、寿命が長く、品質のバラツキの小さいダイヤモンド圧子を提供するものである。
【０００２】
【従来の技術】
従来の硬度測定用圧子は、天然ダイヤモンド結晶の中から適当な原石を選択し、製作されていたが、天然ダイヤモンドには結晶欠陥や不純物が多いため充分なヌープ強度を有する圧子を得ることが難しく、原石による寿命のバラツキが大きいという欠点があった。
【０００３】
【発明が解決しようとする課題】
このように、天然ダイヤモンドは結晶欠陥や不純物が多く、これらは圧縮による破壊の起点となる。そのため、従来の天然ダイヤモンド製圧子は、品質が安定せず、寿命が大きくバラつくという問題があり、特にダイヤモンド焼結体や、ｃＢＮ焼結体などの超硬質材料の硬度測定時にこれが大きな問題となった。
本発明者は上記の問題点を解決するため鋭意研究の結果、高圧下温度差法により合成された不純物量が３ｐｐｍ以下の合成ダイヤモンド結晶を用いることで天然ダイヤモンド製圧子のもつ欠点を解消することができることを発見して本発明に到達した。すなわち、本発明は高圧下の温度差法により合成されるダイヤモンドからなる、高硬度で寿命が長く品質のバラツキの小さいダイヤモンド圧子を提供することを目的とする。
【０００４】
【課題を解決するための手段】
上記の目的は、本発明の下記の態様により達成することができる。
（１）高圧下の温度差法により合成された不純物量３ｐｐｍ以下の合成ダイヤモンド単結晶から作成されたヌープ圧子であって、その圧子の押し込み方向が前記合成ダイヤモンド結晶の＜００１＞方向と平行であり、かつ圧子先端の長い方の陵の方向が前記合成ダイヤモンド結晶の＜１１０＞方向と平行であることを特徴とするダイヤモンド圧子。
（２）高圧下の温度差法により合成された不純物量３ｐｐｍ以下の合成ダイヤモンド単結晶から作成されたヴィッカース圧子であって、その圧子の押し込み方向が前記合成ダイヤモンド結晶の＜００１＞方向と平行であり、かつ圧子先端の陵の方向が前記合成ダイヤモンド結晶の＜１１０＞方向と平行であることを特徴とするダイヤモンド圧子。
【０００５】
【発明の実施の形態】
天然ダイヤモンドは、多くの窒素不純物を含み、地球内部の複雑な成長履歴を反映して、全ての天然ダイヤモンドは結晶内に多くの歪や結晶欠陥をもち、結晶によるバラツキも大きい。天然ダイヤモンドからは、不純物や結晶欠陥を含まない高い品質の結晶を安定入手することはほとんど不可能である。
これに対し、ダイヤモンドが熱力学的に安定な高圧高温条件で育成される合成ダイヤモンド単結晶は、天然ダイヤモンドよりはるかに結晶性に優れ、品質も安定している。しかし、通常の合成ダイヤモンドは、窒素を孤立置換型不純物として数十ｐｐｍ〜数百ｐｐｍ含み（Ｉｂ型）、各種の特性に影響を及ぼす。この窒素不純物は、窒素ゲッターを溶媒に添加することで除去できるが、インクルージョンを含み易くなり良質な結晶が得られなくなる。しかし、本発明者らにより、窒素ゲッターを添加しても良質な結晶が得られる方法が提案された（Sumiya et al., Diamond and Related Materials, 5, 1359(1996) ）。このようにして、窒素不純物を３ｐｐｍ以下に制御した高純度合成ダイヤモンド結晶（IIａ型）は、不純物による結晶欠陥や歪がない。このため、硬度、強度などの機械的特性が向上し、品質のバラツキも小さくなると考えられる。
【０００６】
上記の窒素不純物を３ｐｐｍ以下に制御した高純度合成ダイヤモンド結晶（IIａ型）は、例えば、次のような方法により得ることができる。すなわち、炭素源として高純度黒鉛、溶媒金属としてＦｅ−Ｃｏ等を用い、窒素ゲッターとしてＴｉを１．０〜２．０重量％の割合で溶媒に添加する。得られた原料系は、種結晶と共に超高圧発生装置内に配置し、圧力約５．５ＧＰａ、温度約１３５０℃に数時間〜数十時間、炭素源と種結晶部間の温度差２０〜５０℃として種結晶上にダイヤモンドを生長させる。
【０００７】
このようにして得られたIIａ型ダイヤモンド結晶からヌープ圧子及びヴィッカース圧子は次のようにして作製する。ヌープ圧子の場合はヌープ圧子の押し込み方向（Ｚ軸方向）を、ダイヤモンドの＜００１＞方向、かつ、ヌープ圧子の長軸方向（圧子先端の長い方の陵の方向）をダイヤモンドの＜１１０＞方向となるように研磨してヌープ圧子の形状に仕上げる〔図３（ａ）参照〕。ヴィッカース圧子の場合はヴィッカース圧子の押し込み方向（Ｚ軸方向）を、ダイヤモンドの＜００１＞方向、かつ、ヴィッカース圧子の対角方向（圧子先端の陵の方向）をダイヤモンドの＜１１０＞方向となるように、ダイヤモンドを研磨し、ヴィッカース圧子の形状に仕上げる〔図３（ｂ）参照〕。
【０００８】
本発明者等は、この高純度合成ダイヤモンドの機械的特性を詳細に調べたところ、天然ダイヤモンドや従来の合成ダイヤモンドに見られない特徴を有することを見いだした。
表１に、窒素量の異なる合成ダイヤモンド結晶の（１００）面の＜１００＞方向及び＜１１０＞方向のヌープ硬度を測定した結果を示す。（１００）面＜１００＞方向のヌープ硬度は、図１に示すように、窒素量の減少とともに向上する。窒素量１ｐｐｍ以下のものは、硬度１００００ｋｇ／ｍｍ²以上と高硬度である。
また、窒素が３ｐｐｍ以下の合成ダイヤモンド結晶においては、（１００）面＜１１０＞方向は正常なヌープ圧痕が形成されず、非常に硬いことを示す。図２に、窒素量０．１ｐｐｍの合成IIａ型ダイヤモンド結晶と、６０〜２４０ｐｐｍの窒素を含むＩｂ型ダイヤモンド結晶、及び天然のＩａ型ダイヤモンド結晶（凝集型窒素不純物を約１０００ｐｐｍ含む）の（１００）面上の各方位のヌープ硬度の測定結果を示す。
【０００９】
天然Ｉａ型ダイヤモンドや通常の合成Ｉｂ型ダイヤモンドは（１００）面上では＜１００＞方向が＜１１０＞方向より硬いが、不純物量３ｐｐｍ以下のIIａ型ダイヤモンドはこれとは逆の傾向を示し、特に＜１１０＞方向は、ヌープ圧子による圧痕が形成されず、極めて硬い。これは、合成IIａ型ダイヤモンド結晶は圧子押し込みによる変形の起点となる不純物、欠陥が極めて少ないためと考えられる。なお、不純物３ｐｐｍを越えるとこの傾向は見られなくなり、天然Ｉａ型ダイヤモンド結晶や合成Ｉｂ型ダイヤモンド結晶と同様の傾向を示すようになる。以上の知見から、不純物３ｐｐｍ以下の合成ダイヤモンドをダイヤモンド圧子として用い、また、圧子の結晶方位を図３のように定めた。その結果、従来のダイヤモンド圧子よりはるかに高い強度、長い寿命の圧子が得られることがわかった。
【００１０】
【実施例】
（実施例１）
高圧下の温度差法によるダイヤモンド結晶の合成において、原料に高純度黒鉛、溶媒にＦｅ−Ｃｏ溶媒を用い、窒素ゲッターとしてＴｉを１．５重量％溶媒に添加し、圧力５．５ＧＰａ、温度１３５０℃、合成時間２０時間で、約０．２カラットの高純度IIａ型ダイヤモンド単結晶を合成した。得られたダイヤモンド結晶は、無色透明で、紫外可視スペクトル、赤外線スペクトルとも、窒素などの不純物による吸収がほとんど認められず、不純物０．１ｐｐｍ以下の高純度IIａ型結晶であることを確認した。このダイヤモンド結晶から、ヌープ圧子を以下のように作製した。ヌープ圧子の押し込み方向（Ｚ軸方向）を、ダイヤモンドの＜００１＞方向、かつ、ヌープ圧子の長軸方向（圧子先端の長い方の陵の方向）をダイヤモンドの＜１１０＞方向となるように、ダイヤモンドを研磨し、ヌープ圧子の形状に仕上げた。こうして作製したヌープ圧子で、ダイヤモンド焼結体の硬度を、荷重１０ｋｇ重で測定し、その寿命を従来の天然ダイヤモンド製ヌープ圧子の場合と比較した。高純度合成IIａ型ダイヤモンド製ヌープ圧子は従来のヌープ圧子の１０倍以上の寿命であった。また、原石による寿命のバラツキも極めて小さかった。
【００１１】
（実施例２）
実施例１と同様に合成した不純物０．１ｐｐｍ以下のダイヤモンド結晶から、ヴィッカース圧子を次のように作製した。ヴィッカース圧子の押し込み方向（Ｚ軸方向）を、ダイヤモンドの＜００１＞方向、かつ、ヴィッカース圧子の対角方向（圧子先端の陵の方向）をダイヤモンドの＜１１０＞方向となるように、ダイヤモンドを研磨し、ヴィッカース圧子の形状に仕上げた。こうして作製したヴィッカース圧子で、ダイヤモンド焼結体の硬度を、荷重１０ｋｇ重で測定し、その寿命を従来の天然ダイヤモンド製ヴィッカース圧子の場合と比較した。高純度合成IIａ型ダイヤモンド製ヴィッカース圧子は従来のヴィッカース圧子の１０倍以上の寿命であった。また、原石による寿命のバラツキも極めて小さかった。
【００１２】
【比較例】
窒素ゲッターを用いずに、他は実施例１と同様にしてダイヤモンドを合成した。得られたダイヤモンドは、約０．３カラットの窒素不純物を含んだＩｂ型結晶で、黄色を呈していた。赤外吸収スペクトルより見積もった窒素量は約６０ｐｐｍであった。この合成Ｉｂ型ダイヤモンド結晶より、実施例１と同様にしてヌープ圧子を作製した。ダイヤモンド焼結体の硬度測定テストでは、寿命のバラツキは小さいものの、数回〜数十回の使用で破壊した。
【００１３】
【表１】

【００１４】
【発明の効果】
本発明のダイヤモンド圧子は、ヌープ圧子又はヴィッカース圧子のいずれも硬度が非常に高く、寿命も従来の圧子と比べて１０倍以上に達する。原石による寿命のバラツキも極めて小さい。勿論、ヌープ圧子やヴィッカース圧子以外のダイヤモンド圧子やインデンターに適用することができる。
【図面の簡単な説明】
【図１】図１は本発明による合成ダイヤモンド結晶の（１００）＜１００＞のヌープ硬度と窒素不純物量との関係を示すグラフである。
【図２】図２は本発明による合成ダイヤモンド結晶を含む各種ダイヤモンド結晶の（１００）面上のヌープ硬度の異方性を示すグラフである。
【図３】図３（ａ）及び（ｂ）は本発明に係るダイヤモンド圧子の先端部の形状示す概念図である〔（ａ）はヌープ圧子、（ｂ）はヴィッカース圧子で、それぞれ上の図が横面図、下の図が正面図である〕。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a diamond indenter, and particularly provides a diamond indenter having high hardness, a long life, and a small quality variation.
[0002]
[Prior art]
Conventional indenters for hardness measurement have been manufactured by selecting appropriate rough stones from natural diamond crystals, but it is difficult to obtain indenters with sufficient Knoop strength because natural diamond has many crystal defects and impurities. However, there was a drawback that there was a large variation in life due to the rough.
[0003]
[Problems to be solved by the invention]
As described above, natural diamond has many crystal defects and impurities, which are the starting points of fracture due to compression. Therefore, the conventional indenter made of natural diamond has the problem that the quality is not stable and the life is greatly varied. Especially, this is a big problem when measuring the hardness of a super hard material such as a diamond sintered body or a cBN sintered body. became.
As a result of intensive studies to solve the above problems, the present inventor has solved the disadvantages of a natural diamond indenter by using a synthetic diamond crystal having an amount of impurities of 3 ppm or less synthesized by a high pressure difference method. The present invention has been achieved by discovering that That is, an object of the present invention is to provide a diamond indenter composed of diamond synthesized by a temperature difference method under high pressure, having a high hardness, a long life and a small quality variation.
[0004]
[Means for Solving the Problems]
The above object can be achieved by the following aspects of the present invention.
(1) A Knoop indenter made from a synthetic diamond single crystal having an impurity amount of 3 ppm or less synthesized by a temperature difference method under high pressure, the indentation direction of the indenter being parallel to the <001> direction of the synthetic diamond crystal The diamond indenter is characterized in that the direction of the longer end of the indenter tip is parallel to the <110> direction of the synthetic diamond crystal.
(2) A Vickers indenter prepared from a synthetic diamond single crystal having an impurity amount of 3 ppm or less synthesized by a temperature difference method under high pressure, and the indentation direction of the indenter is parallel to the <001> direction of the synthetic diamond crystal. The diamond indenter is characterized in that the direction of the crest of the indenter tip is parallel to the <110> direction of the synthetic diamond crystal.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
Natural diamond contains a lot of nitrogen impurities and reflects the complicated growth history inside the earth. All natural diamonds have many strains and crystal defects in the crystal and have large variations due to the crystal. It is almost impossible to stably obtain high quality crystals free from impurities and crystal defects from natural diamond.
On the other hand, a synthetic diamond single crystal grown under high pressure and high temperature conditions in which diamond is thermodynamically stable has far superior crystallinity and quality as compared with natural diamond. However, ordinary synthetic diamond contains several tens of ppm to several hundred ppm of nitrogen as an isolated substitutional impurity (type Ib) and affects various properties. Although this nitrogen impurity can be removed by adding a nitrogen getter to the solvent, it tends to contain inclusions and a good quality crystal cannot be obtained. However, the present inventors have proposed a method in which high-quality crystals can be obtained even when nitrogen getter is added (Sumiya et al., Diamond and Related Materials, 5, 1359 (1996)). In this way, the high-purity synthetic diamond crystal (IIa type) in which the nitrogen impurity is controlled to 3 ppm or less is free from crystal defects and distortion due to the impurity. For this reason, it is considered that mechanical properties such as hardness and strength are improved, and variation in quality is also reduced.
[0006]
The high-purity synthetic diamond crystal (type IIa) in which the nitrogen impurity is controlled to 3 ppm or less can be obtained, for example, by the following method. That is, high-purity graphite is used as the carbon source, Fe—Co or the like is used as the solvent metal, and Ti is added to the solvent at a ratio of 1.0 to 2.0% by weight as the nitrogen getter. The obtained raw material system is placed in an ultra-high pressure generator together with the seed crystal, the pressure is about 5.5 GPa, the temperature is about 1350 ° C. for several hours to several tens of hours, and the temperature difference between the carbon source and the seed crystal part is 20 to 50. Grow diamonds on seed crystals at ℃.
[0007]
A Knoop indenter and a Vickers indenter are produced from the type IIa diamond crystal thus obtained as follows. In the case of a Knoop indenter, the pushing direction (Z-axis direction) of the Knoop indenter is the <001> direction of the diamond, and the long axis direction of the Knoop indenter (the direction of the ridge of the longer indenter tip) is the <110> direction of the diamond. Is finished to a shape of a Knoop indenter (see FIG. 3A). In the case of a Vickers indenter, the pushing direction of the Vickers indenter (Z-axis direction) is the <001> direction of the diamond, and the diagonal direction of the Vickers indenter (the direction of the indentation tip) is the <110> direction of the diamond. Next, the diamond is polished and finished in the shape of a Vickers indenter (see FIG. 3B).
[0008]
The present inventors have examined the mechanical properties of this high-purity synthetic diamond in detail, and found that it has characteristics not found in natural diamond and conventional synthetic diamond.
Table 1 shows the results of measurement of Knoop hardness in the <100> direction and <110> direction of the (100) plane of synthetic diamond crystals having different amounts of nitrogen. As shown in FIG. 1, the Knoop hardness in the (100) plane <100> direction improves as the amount of nitrogen decreases. Those having a nitrogen content of 1 ppm or less have a hardness as high as 10,000 kg / mm ² or more.
Further, in a synthetic diamond crystal having nitrogen of 3 ppm or less, the (100) plane <110> direction indicates that a normal Knoop indentation is not formed and it is very hard. FIG. 2 shows (100) of a synthetic type IIa diamond crystal having a nitrogen content of 0.1 ppm, an Ib type diamond crystal containing 60 to 240 ppm of nitrogen, and a natural type Ia diamond crystal (containing about 1000 ppm of aggregated nitrogen impurities). The measurement result of Knoop hardness of each azimuth | direction on a surface is shown.
[0009]
Natural Ia type diamonds and normal synthetic type Ib type diamonds have a <100> direction harder than the <110> direction on the (100) plane, but IIa type diamonds with an impurity amount of 3 ppm or less show the opposite tendency. The <110> direction is extremely hard with no indentation formed by the Knoop indenter. This is presumably because the synthetic IIa type diamond crystal has very few impurities and defects that are the starting points of deformation due to indentation. When the impurity exceeds 3 ppm, this tendency is not observed, and the same tendency as that of the natural Ia type diamond crystal or the synthetic Ib type diamond crystal is exhibited. From the above knowledge, synthetic diamond having an impurity of 3 ppm or less was used as a diamond indenter, and the crystal orientation of the indenter was determined as shown in FIG. As a result, it was found that an indenter with much higher strength and longer life than the conventional diamond indenter can be obtained.
[0010]
【Example】
Example 1
In the synthesis of diamond crystals by a temperature difference method under high pressure, high-purity graphite is used as a raw material, Fe—Co solvent is used as a solvent, Ti is added as a nitrogen getter to a 1.5 wt% solvent, pressure is 5.5 GPa, temperature is 1350. About 0.2 carat high-purity type IIa diamond single crystal was synthesized at 20 ° C. for 20 hours. The obtained diamond crystal was colorless and transparent, and absorption by impurities such as nitrogen was hardly observed in both the ultraviolet-visible spectrum and the infrared spectrum, and it was confirmed that it was a high-purity type IIa crystal having an impurity of 0.1 ppm or less. A Knoop indenter was produced from this diamond crystal as follows. The pushing direction of the Knoop indenter (Z-axis direction) is the <001> direction of the diamond, and the long-axis direction of the Knoop indenter (the direction of the long edge of the indenter tip) is the <110> direction of the diamond. Diamond was polished and finished in the shape of a Knoop indenter. With the Knoop indenter thus produced, the hardness of the diamond sintered body was measured at a load of 10 kg and its life was compared with that of a conventional natural diamond Knoop indenter. The high-purity synthetic type IIa diamond Knoop indenter has a life of more than 10 times that of a conventional Knoop indenter. In addition, the variation in life due to the rough was extremely small.
[0011]
(Example 2)
A Vickers indenter was produced as follows from a diamond crystal having an impurity content of 0.1 ppm or less synthesized in the same manner as in Example 1. Polish the diamond so that the indentation direction of the Vickers indenter (Z-axis direction) is the <001> direction of the diamond, and the diagonal direction of the Vickers indenter (the direction of the indentation tip) is the <110> direction of the diamond. And finished in the shape of a Vickers indenter. With the Vickers indenter thus produced, the hardness of the diamond sintered body was measured at a load of 10 kg, and the lifetime was compared with the case of the conventional Vickers indenter made of natural diamond. The high-purity synthetic type IIa diamond Vickers indenter has a lifespan more than 10 times that of the conventional Vickers indenter. In addition, the variation in life due to the rough was extremely small.
[0012]
[Comparative example]
Diamond was synthesized in the same manner as in Example 1 except that no nitrogen getter was used. The obtained diamond was a type Ib crystal containing nitrogen impurities of about 0.3 carat and had a yellow color. The amount of nitrogen estimated from the infrared absorption spectrum was about 60 ppm. A Knoop indenter was produced from this synthetic type Ib diamond crystal in the same manner as in Example 1. In the hardness measurement test of the diamond sintered body, although the variation in the life was small, it was destroyed after being used several times to several tens of times.
[0013]
[Table 1]

[0014]
【The invention's effect】
The diamond indenter of the present invention has a very high hardness both in the Knoop indenter and the Vickers indenter, and the service life reaches 10 times or more as compared with the conventional indenter. The variation in life due to the rough is very small. Of course, it can be applied to diamond indenters and indenters other than Knoop indenters and Vickers indenters.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between (100) <100> Knoop hardness and nitrogen impurity content of a synthetic diamond crystal according to the present invention.
FIG. 2 is a graph showing the Knoop hardness anisotropy on the (100) plane of various diamond crystals including a synthetic diamond crystal according to the present invention.
FIGS. 3 (a) and 3 (b) are conceptual diagrams showing the shape of the tip of a diamond indenter according to the present invention [(a) is a Knoop indenter, and (b) is a Vickers indenter, respectively. Is a side view, and the lower figure is a front view].

Claims

A Knoop indenter produced from a synthetic diamond single crystal having an impurity amount of 3 ppm or less synthesized by a temperature difference method under high pressure , the indentation direction of the indenter being parallel to the <001> direction of the synthetic diamond crystal, and A diamond indenter characterized in that the direction of the longer end of the indenter tip is parallel to the <110> direction of the synthetic diamond crystal .

A Vickers indenter produced from a synthetic diamond single crystal having an impurity amount of 3 ppm or less synthesized by a temperature difference method under high pressure, the indentation direction of the indenter being parallel to the <001> direction of the synthetic diamond crystal, and A diamond indenter characterized in that the direction of the crest of the indenter tip is parallel to the <110> direction of the synthetic diamond crystal.