Polycrystalline diamond

Abstract

An object is to provide polycrystalline diamond applicable to diverse applications; and a water jet orifice, a stylus for gravure printing, a scriber, a diamond cutting tool, and a scribing wheel that include such polycrystalline diamond. This object is achieved by polycrystalline diamond obtained by converting and sintering non-diamond carbon under an ultrahigh pressure and at a high temperature without addition of a sintering aid or a catalyst, wherein sintered diamond grains constituting the polycrystalline diamond have an average grain diameter of more than 50 nm and less than 2500 nm and a purity of 99% or more, and the diamond has a D90 grain diameter of (average grain diameter+average grain diameter×0.9) or less.

Description

TECHNICAL FIELD [0001]The present invention relates to polycrystalline diamond obtained by converting and sintering non-diamond carbon without addition of a sintering aid or a catalyst.BACKGROUND ART [0002]Natural and artificial monocrystalline diamonds have been used for various applications because of their excellent properties. A tool including monocrystalline diamond is, for example, a water jet orifice (Patent Document 1), a stylus for gravure printing (Patent Documents 2 and 3), a scriber (Patent Document 4), a diamond cutting tool (Patent Documents 5 and 6), or a scribing wheel (Patent Document 7).[0003]However, such monocrystalline diamond also has a property that abrasion losses vary (uneven wear) depending on crystal orientations of the diamond. For example, abrasion loss considerably varies between the (111) plane and the (100) plane. For this reason, monocrystalline diamond applied to such tools described above is worn away only in a specific plane in a short time as the...

AI Technical Summary

Benefits of technology

[0207]Polycrystalline diamond used in the present invention is less prone to wear unevenly and allows stable working for a long period of time compared with conventional monocrystalline diamonds and sintered diamond compacts containing metal binders. Therefore, such polycrystalline diamond can be suitably applied to water jet orifices, styluses for gravure printing, scribers, cutting tools, and scribing wheels.

[0208]A water jet orifice according to the present invention can provide a cutting width with stability for a long period of time compared with conventional orifices and hence can be suitably used as an orifice for a water jet configured to expel fluid containing rigid particles (alumina or the like) at a high pressure to thereby cut or work workpieces.

Problems solved by technology

However, such monocrystalline diamond also has a property that abrasion losses vary (uneven wear) depending on crystal orientations of the diamond.

For this reason, monocrystalline diamond applied to such tools described above is worn away only in a specific plane in a short time as the tools are used, and predetermined effects are not provided, which has been a problem.

For this reason, when monocrystalline diamond is applied to a tool subjected to a stress during use, the tool breaks or cracks, which also has been a problem.

As the amount of the binder decreases, the diamond grains come off and the effects are not provided with stability for a long period of time.

There is also a problem in that adhesive wear occurs between the metal binder region and a metal material being worked and working for a long period of time cannot be performed.

However, removal of a metal binder reduces the binding power of diamond grains, which most likely increases abrasion loss.

However, this polycrystalline diamond has a small binding strength among grains and hence suffers from large abrasion loss, which has been a problem.

A water jet orifice including monocrystalline diamond has a problem in that a target cutting width is no longer achieved after the lapse of usage time.

The orifice having the shape of a cylinder at the initial stage of use suffers from abrasion in a plane susceptible to abrasion in a short time.

Thus, a cutting width is not provided with stability for a long period of time, which is a problem.

As a result, a metal binder region, which is softer than diamond grains, wears away in a short time and a cutting width is not provided with stability for a long period of time, which is a problem.

However, such a diamond thin film has a short wear life, and has a small binding strength among grains and hence has a short wear life, which has been a problem.

However, possibly because such diamond has a property of cleaving, such a tool breaks or cracks by a stress during use, which is a problem.

Due to the property of uneven wear, such diamond is worn away only in a specific plane in a short time as the tool is used, and hence working for a long period of time cannot be performed, which has also been a problem.

However, possibly because monocrystalline diamond has a property of cleaving along the (111) plane as described above, scribers composed of monocrystalline diamond crack or wear unevenly when a plane used for scribing only slightly deviates from the (111) plane, which has been a problem.

However, because of the problems of the cleaving property and the property of uneven wear of monocrystalline diamond as described above, such a tool composed of monocrystalline diamond has a problem in that the tool breaks or cracks due to a stress during use, is worn away only in a specific plane in a short time as the tool is used, and working for a long period of time cannot be performed.

However, as with other tools, such a scribing wheel breaks or cracks due to a stress during use because of the problem of the cleaving property of monocrystalline diamond, which has been a problem.

Due to the property of uneven wear, such a tool is worn away only in a specific plane in a short time as the tool is used, and use of the tool for a long period of time is not possible, which has been a problem.

As a result, the wheel becomes no longer able to roll, which has been a problem.

However, even though sintered diamond is used, the following problems are likely to occur: a metal binder region containing cobalt or the like is softer than diamond grains and hence wears away in a short time, and adhesive wear occurs between the metal binder region and a metal material being worked such as copper and working for a long period of time cannot be performed.

However, this reduces the binding power of diamond grains, which most likely increases abrasion loss.

Polycrystalline diamond that is produced by CVD and is free from a metal binder has a small binding strength among grains and hence probably has a problem in that such diamond has a short wear life.