JPH1114524A - Diamond indenter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a diamond indenter which is made of diamond synthesized by a temperature difference method under high pressure and has high hardness, long life, and small variance in quality. SOLUTION: The diamond indenter is made of the synthetic diamond monocrystal which is synthesized by the temperature difference method under high pressure and <=3 ppm in impurity amount. For example, the diamond indenter is a Knoop indenter; and the pressing-in direction of the indenter is parallel to the <001> direction of the synthetic diamond crystal and the direction of the long ridge of the indenter tip is parallel to the <110> direction of the synthetic diamond crystal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diamond indenter, and more particularly to a diamond indenter having a high hardness, a long life and a small variation in quality.

[0002]

2. Description of the Related Art A conventional indenter for measuring hardness has been manufactured by selecting an appropriate rough from natural diamond crystals. However, indenters having sufficient Knoop strength because natural diamond has many crystal defects and impurities. However, there is a disadvantage in that it is difficult to obtain such a material, and there is a large variation in the life due to the rough.

[0003]

As described above, natural diamond has many crystal defects and impurities, and these become starting points of destruction by compression. Therefore, the conventional natural diamond indenter has a problem that the quality is not stable and the life is greatly varied. This is a serious problem particularly when measuring the hardness of ultra-hard materials such as a diamond sintered body and a cBN sintered body. became. The inventor of the present invention has conducted intensive studies to solve the above-mentioned problems, and as a result, has solved the drawbacks of the natural diamond indenter by using a synthetic diamond crystal having an impurity amount of 3 ppm or less synthesized by a high-pressure temperature difference method. The inventors have found that the present invention can be performed, and arrived at the present invention. That is, an object of the present invention is to provide a diamond indenter made of diamond synthesized by a temperature difference method under high pressure and having high hardness, long life and small quality variation.

[0004]

The above objects can be achieved by the following aspects of the present invention. (1) Impurity amount 3p synthesized by temperature difference method under high pressure
A diamond indenter made of a synthetic diamond single crystal of pm or less, preferably 1 ppm or less. (2) The <100> direction of the synthetic diamond crystal is
The diamond indenter according to the above (1), which is parallel to the direction in which the diamond indenter is pushed. (3) The diamond indenter is a Knoop indenter, and the indentation direction of the indenter is <0 of the synthetic diamond crystal.
The diamond indenter according to the above (1), wherein the direction of the longer ridge at the tip of the indenter is parallel to the <110> direction of the synthetic diamond crystal. (4) The diamond indenter is a Vickers indenter, the indentation direction of the indenter is parallel to the <001> direction of the synthetic diamond crystal, and the direction of the tip of the indenter is parallel to the <110> direction of the synthetic diamond crystal. The diamond indenter according to the above (1), wherein:

[0005]

DETAILED DESCRIPTION OF THE INVENTION Natural diamond contains many nitrogen impurities and reflects the complex growth history inside the earth.
All natural diamonds have many strains and crystal defects in the crystal, and there is great variation due to the crystal. From natural diamond, it is almost impossible to stably obtain high-quality crystals free of impurities and crystal defects. On the other hand, a synthetic diamond single crystal in which diamond is grown under high pressure and high temperature conditions that are thermodynamically stable has much better crystallinity than natural diamond and stable quality. However, ordinary synthetic diamond contains several tens ppm to several hundred ppm of nitrogen as an isolated substitutional impurity (Ib type), and affects various characteristics. This nitrogen impurity can be removed by adding a nitrogen getter to the solvent, but inclusions are likely to be included and a good-quality crystal cannot be obtained. However, the present inventors have proposed a method of obtaining a high-quality crystal even when a nitrogen getter is added (Sumiya et al., Di.
amond and Related Materials, 5, 1359 (1996)). Thus, the high-purity synthetic diamond crystal (IIa type) in which the nitrogen impurity is controlled to 3 ppm or less has no crystal defects or distortion due to the impurity. For this reason, it is considered that mechanical properties such as hardness and strength are improved, and variations in quality are reduced.

A high-purity synthetic diamond crystal (IIa type) in which the nitrogen impurity is controlled to 3 ppm or less is, for example,
It can be obtained by the following method. That is, high-purity graphite is used as a carbon source, Fe-Co or the like is used as a solvent metal, and 1.0 to 2.0% by weight of Ti is used as a nitrogen getter.
To the solvent. The obtained raw material system was placed in an ultra-high pressure generator together with a seed crystal, and the pressure was about 5.5 GPa.
The diamond is grown on the seed crystal at a temperature of about 1350 ° C. for several hours to several tens of hours with a temperature difference of 20 to 50 ° C. between the carbon source and the seed crystal part.

A Knoop indenter and a Vickers indenter are produced from the IIa type diamond crystal thus obtained as follows. In the case of a Knoop indenter, the pushing direction (Z-axis direction) of the Knoop indenter is set in the <001> direction of the diamond, and the long axis direction of the Knoop indenter (the direction of the longer ridge at the tip of the indenter) is set in the <110> direction of the diamond. And finished in the shape of a Knoop indenter (see FIG. 3A). In the case of a Vickers indenter, the pushing direction (Z-axis direction) of the Vickers indenter is set to <001> of diamond.
The diamond is polished so that the direction and the diagonal direction of the Vickers indenter (the direction of the tip of the indenter) are the <110> direction of the diamond, and the diamond is finished in the shape of a Vickers indenter (see FIG. 3B).

The present inventors have examined the mechanical properties of the high-purity synthetic diamond in detail and found that the high-purity synthetic diamond has characteristics not found in natural diamond and conventional synthetic diamond. Table 1 shows the <100> direction and <11> of the (100) plane of synthetic diamond crystals having different nitrogen contents.
The result of measuring the Knoop hardness in the 0> direction is shown. (10
0) The Knoop hardness in the <100> plane increases as the amount of nitrogen decreases, as shown in FIG. Those having a nitrogen content of 1 ppm or less have high hardness of 10,000 kg / mm ² or more. In the case of a synthetic diamond crystal containing 3 ppm or less of nitrogen, a normal Knoop indentation is not formed in the (100) plane <110> direction, indicating that the crystal is very hard. FIG.
On the (100) plane of a synthetic IIa diamond crystal having a nitrogen amount of 0.1 ppm, an Ib type diamond crystal containing 60 to 240 ppm of nitrogen, and a natural Ia type diamond crystal (containing about 1000 ppm of aggregated nitrogen impurities) 3 shows the measurement results of the Knoop hardness in each direction.

[0009] Natural Ia type diamond and ordinary synthetic Ib
In the type diamond, the <100> direction is harder than the <110> direction on the (100) plane, but II
The a-type diamond shows the opposite tendency, especially <1.
In the 10> direction, no indentation is formed by the Knoop indenter, and the direction is extremely hard. This is presumably because the synthetic IIa type diamond crystal has very few impurities and defects which 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 and the synthetic Ib type diamond crystal is obtained. From the above findings, 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 conventional diamond indenters could be obtained.

[0010]

EXAMPLES Example 1 In the synthesis of diamond crystals by the temperature difference method under high pressure, high-purity graphite was used as a raw material and Fe—Co was used as a solvent.
Using a solvent, Ti was added as a nitrogen getter to a 1.5% by weight solvent, and a pressure of 5.5 GPa, a temperature of 1350 ° C., and a synthesis time of 20 hours were used to synthesize a high-purity type IIa diamond single crystal of about 0.2 carats. . The obtained diamond crystal was colorless and transparent, and almost no absorption due to impurities such as nitrogen was recognized in both the ultraviolet visible spectrum and the infrared spectrum, and it was confirmed that the diamond crystal was a high-purity type IIa crystal having an impurity of 0.1 ppm or less. From this diamond crystal, a Knoop indenter was produced as follows. The push 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 longer ridge at the tip of the indenter) is the <110> direction of the diamond. The diamond was polished to a Knoop indenter shape. The hardness of the diamond sintered body was measured with a load of 10 kg weight using the Knoop indenter thus manufactured, 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 service life that is at least 10 times that of the conventional Knoop indenter. Also, the variation in the life due to the rough stone was extremely small.

(Example 2) A Vickers indenter was produced as follows from a diamond crystal having an impurity of 0.1 ppm or less synthesized in the same manner as in Example 1. The Vickers indenter indentation direction (Z-axis direction) is
The diamond was polished so that the> direction and the diagonal direction of the Vickers indenter (the direction of the ridge at the tip of the indenter) became the <110> direction of the diamond, and finished in the shape of a Vickers indenter. With the Vickers indenter thus manufactured, the hardness of the diamond sintered body was measured under a load of 10 kg,
Its life was compared with that of a conventional natural diamond Vickers indenter. The Vickers indenter made of a high-purity synthetic type IIa diamond has a life ten times or more that of a conventional Vickers indenter. Also, the variation in the life due to the rough stone was extremely small.

[0012]

Comparative Example A diamond was synthesized in the same manner as in Example 1 except that no nitrogen getter was used. The resulting diamond was an Ib type crystal containing about 0.3 carats of nitrogen impurities and was yellow. The amount of nitrogen estimated from the infrared absorption spectrum was about 60 ppm. A Knoop indenter was produced from this synthetic Ib type 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, the diamond was broken after several to several tens of uses.

[0013]

[Table 1] * Measurement is not possible because no indentation is formed

[0014]

EFFECT OF THE INVENTION The diamond indenter of the present invention has a very high hardness of either a Knoop indenter or a Vickers indenter,
The service life also reaches 10 times or more as compared with the conventional indenter. The variation in life due to rough stones is extremely small. Of course, the present invention 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 the (100) <100> Knoop hardness and the amount of nitrogen impurities of a synthetic diamond crystal according to the present invention.

FIG. 2 is a graph showing the anisotropy of Knoop hardness 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, (b) is a Vickers indenter, and each of the above figures is an upper diagram. Is a side view, and the lower figure is a front view].

Claims (4)

[Claims] 1. A diamond indenter manufactured from a synthetic diamond single crystal having an impurity amount of 3 ppm or less synthesized by a temperature difference method under high pressure. 2. The synthetic diamond crystal <100>
The diamond indenter according to claim 1, wherein the direction is parallel to the direction in which the diamond indenter is pushed. 3. The diamond indenter is a Knoop indenter, the indentation direction of the indenter is parallel to the <001> direction of the synthetic diamond crystal, and the direction of the longer ridge at the tip of the indenter is the direction of the synthetic diamond crystal. <110>
The diamond indenter according to claim 1, wherein the indenter is parallel to the direction. 4. The diamond indenter is a Vickers indenter, the indentation direction of the indenter is parallel to the <001> direction of the synthetic diamond crystal, and the direction of the ridge of the indenter tip is the <110> direction of the synthetic diamond crystal. The diamond indenter according to claim 1, wherein the indenter is parallel.