JP2007230807A - Method of producing diamond product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing a diamond product less in surface defects even if a diamond shape is complicated when the diamond product having the single crystal diamond is produced. <P>SOLUTION: When a diamond is polished, the diamond is mechanically polished, and thereafter, microcracks in the surface of the diamond is removed by bringing a copper plate, on which copper oxide is formed by heating in atmosphere, into static contact with the diamond, and keeping the contact state for a prescribed time to wear the diamond. Thereby, a high quality diamond product can be produced. The surface roughness of the copper plate is preferably not larger than the surface roughness of the mechanically polished diamond. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a diamond product having high shape accuracy and few surface defects.

  When using a diamond tool, which is one of the diamond products, to form a cutting edge on diamond, it can be processed by using a diamond grindstone or polishing by supplying loose abrasive grains between the Skyf machine and diamond. Do.

  However, in the method using a diamond grindstone, since a large force acts during processing, problems such as CVD diamond are likely to cause the diamond to peel from the substrate, and chipping and chipping are also likely to occur, making it easy to perform high-precision processing. is not. In addition, the method of supplying loose abrasive grains can be processed with high accuracy, but has a problem of low processing efficiency.

  As a method for solving this, there has been proposed a method in which polishing is performed by making a metal and diamond continuously contact each other and making a relative motion by utilizing thermochemical wear of diamond. (For example, see Patent Document 1)

JP 2003-73190 A

In the processing of single crystal diamond, processing with a diamond grindstone or skyf machine is performed in the same manner as described above, but this method causes micro cracks on the diamond surface. The occurrence of microcracks reduces the strength of the tool cutting edge, and therefore tends to cause chipping, resulting in a problem of shortening the tool life. Further, in the method of relative movement of the metal and diamond described in Patent Document 1, the shape of the diamond product to be created is limited by the relative motion, special measures are required for holding the diamond, and vibration For example, the problem is that it is difficult to mass-produce diamond products with high shape accuracy.
For this reason, the present invention proposes a method for producing a diamond product having a complicated shape and few surface defects.

A feature of the method for producing a diamond product of the present invention is a method for producing a diamond product having single crystal diamond,
Mechanically polishing the diamond;
A step of statically contacting a copper plate on which copper oxide is formed by heating the diamond in the atmosphere, and maintaining the state for a predetermined time to wear the diamond.

  The surface roughness of the copper plate is preferably equal to or less than the surface roughness of mechanically polished diamond.

  According to the method for manufacturing a diamond product of the present invention, when polishing single crystal diamond, it is easy to polish even if it has a complicated shape, and a large number of diamond products can be polished at one time. High efficiency. In addition, since microcracks generated by mechanical polishing can be removed, a highly reliable diamond product can be manufactured. Particularly in diamond products such as tools, since microcracks are greatly removed, a tool having a long life and excellent chipping resistance is produced.

  The polishing of diamond in the present invention is performed in a post-mechanical polishing step, and a large number of diamonds are simultaneously thermochemically polished for the purpose of removing microcracks and improving the reliability of the diamond product. Thereby, the thermochemical polishing time per product can be shortened. Also, when performing thermochemical polishing, the diamond is worn only by the thermochemical action of copper and diamond without giving relative motion between the diamond and the copper plate, so the required shape accuracy is easily achieved. Is done.

The thermochemical polishing performed in the present invention is based on the following principle. FIG. 1 is an Ellingham diagram showing the standard free energy change ΔG ° per mole of oxygen in the oxidation reaction of copper and carbon as a function of temperature. In the temperature range of the figure, ΔG ° of all Ellingham lines is negative, so in copper,
2Cu + O ₂ = 2CuO or 4Cu + O ₂ = 2CuO ₂
In carbon,
2C + O ₂ = 2CO or C + O ₂ = CO ₂
Oxidation reaction occurs. Further, since ΔG ° of the carbon oxide is smaller than ΔG ° of the copper oxide, the carbon oxide is more stable than the copper oxide. Therefore, when non-oxidized carbon comes into contact with copper oxide, it deprives oxygen and oxidizes the carbon, reducing the partner. That is, if there is oxygen near the interface between copper and diamond, the diamond tool is polished based on the principle of oxidation-reduction reaction in which copper is oxidized and diamond is reduced.

  Here, in order to clarify the thermochemical polishing performance based on the above-described principle, the diamond sample is pressed against a copper plate heated at a temperature in the range of 323 to 523 K with a load of 1 N, and held for a certain period of time to perform thermochemistry. Polishing was performed. At this time, the polishing amount was obtained from a difference in the depth of the ring crack before and after polishing by previously generating a ring crack in the diamond sample with a micro compression tester equipped with a diamond ball indenter having a tip radius of 5 μm. In addition, in order to confirm that microcracks on the diamond surface were removed by thermochemical polishing, the Hertz strength of the diamond sample was examined using the above tester.

  FIG. 2 shows the relationship between the polishing amount and the heating time. From this figure, it can be seen that polishing can be performed on the order of several tens of nanometers simply by bringing diamond into contact with heated copper oxide. FIG. 3 shows the relationship between the polishing rate (polishing amount per unit time) and the heating temperature. The Arrhenius relationship is established between the two, and the activation energy of diamond wear based on the thermochemical action with copper is calculated as 218 kJ / mol from the gradient of the linear relationship. From the difference between the free energy change of the carbon oxidation reaction and the free energy change of the copper oxidation reaction at 523 K, the free energy change of the reduction reaction of copper oxide by diamond is obtained as 133 kJ / mol. Since this free energy change and the activation energy of diamond wear are in order, it is considered that diamond wear is due to the above-mentioned thermochemical action.

  FIG. 4 shows changes in the Hertz intensity of the diamond when the diamond sample is heated while being brought into contact with the copper powder, and when the diamond sample and the heated copper plate are brought into contact with each other and thermochemical polishing is performed. When diamond is heated in copper powder, if the heating time is increased, microcracks pre-existing on the surface of the diamond develop and the microfracture strength of the diamond decreases. On the other hand, when the diamond is brought into contact with a heated copper plate, the microfracture strength of the diamond once decreases due to the progress of cracks in a period in which the heating time is short. However, after a certain heating time or more, microcracks existing on the diamond surface are removed along with wear of the diamond surface, so that the microfracture strength increases.

  From the above, it can be said that microcracks existing on the surface of diamond can be removed by performing thermal chemical polishing for a certain period of time or longer. However, since the polishing rate of thermochemical polishing is low, it is necessary to perform efficient polishing in combination with mechanical polishing.

  In order to confirm the performance of diamond products processed based on the above principle, a diamond cutting tool was manufactured and ultra-precision cutting was performed. FIG. 5 shows an outline when performing thermochemical polishing. As a diamond tool according to the manufacturing method of the present invention, a rake face (100) surface of a diamond tool mechanically polished with a diamond grindstone and a Skyf machine is pressed against a copper plate heated to a temperature of 523 K with a load F of 1 N. Time thermal chemical polishing was performed. For comparison, except that the above-mentioned thermochemical polishing is not performed, ultra-precision cutting is performed using the same diamond tool as above (hereinafter referred to as a comparative example), and the wear resistance and life of both are compared. did.

  Using the diamond tool manufactured as described above, an oxygen-free copper disk was subjected to front cutting by a dry method under conditions of a cutting speed of 15.6 m / s, a cutting depth of 6.7 μm, and a feed of 3 μm / rev.

Judgment of the life of a diamond tool was performed by the method described in Japanese Patent Application Laid-Open No. 2005-125480 proposed by the applicant. That is, according to the following method. Cutting resistance and AE are measured in the cutting process, and power spectrum analysis and amplitude distribution analysis are performed respectively. For the cutting resistance, the spectral index β of the spectral density S (f) ∝1 / f ^β with power law distribution with respect to the frequency f, and with respect to AE, the AE event rate N with power law distribution with respect to the amplitude a. It evaluates the scaling exponent m of .alpha.a ^-m, using spectral exponent beta> 1 and scaling exponent m <2 becomes a reference, to determine the tool life.

  FIG. 6 shows the change of the spectral index β with respect to the cutting distance. It can be seen that as the crater wear and boundary wear of the rake face progress, the spectral index β gradually increases and eventually exceeds 1. This indicates that the variation in cutting force has changed from random to self-similar, suggesting that the tool life is close. FIG. 7 shows the change of the scaling index m with respect to the cutting distance. In this figure, it can be seen that the scaling index m is smaller than 2. This suggests that chipping has occurred. Further, in the same figure, it can be seen that the diamond tool of the present invention generates less chipping than the diamond tool of the comparative example. From this, it can be seen that microcracks near the cutting edge are removed by thermochemical polishing and chipping resistance is improved. Further, when the tool life is compared according to the above-mentioned tool life criteria, the life distance of the diamond tool finished by the thermochemical polishing method of the present invention is 485 km, and the life distance of the diamond tool finished by the mechanical polishing method of the comparative example. Is 345 km, so the life span is extended by about 40%. Therefore, it is clear that the occurrence of chipping can be suppressed and the tool life can be greatly extended by performing the thermal chemical polishing after the mechanical polishing.

The figure which shows the variation | change_quantity of the standard free energy in the oxidation reaction of copper and carbon. The figure which shows the relationship between grinding | polishing amount and heating time. The figure which shows the relationship between polishing rate and heating temperature. The figure which shows the relationship between the Hertz intensity | strength of a diamond, and heating time. The figure which shows the outline | summary of a thermochemical polishing apparatus. The figure which shows the change with respect to the cutting distance of the spectrum index | exponent (beta). The figure which shows the change with respect to the cutting distance of the scaling index | exponent m.

Explanation of symbols

1 Diamond tool 2 Copper plate 3 Heater

Claims (2)

A method for producing a diamond product having single crystal diamond,
Mechanically polishing the diamond;
A step of statically contacting the diamond with a copper plate formed with copper oxide heated in the atmosphere, and maintaining the state for a predetermined time to wear the diamond;
A method for producing a diamond product, comprising:   The method for producing a diamond product according to claim 1, wherein the copper plate has a surface roughness equal to or less than a surface roughness of the mechanically polished diamond.

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