JPH03103397A - High-strength diamond - Google Patents

Abstract

PURPOSE:To improve mechanical strength of diamond, comprising one or more element selected from metallic elements of group IVa to group VIIa and group VIII of the periodic table, metallic elements of group IIIb to group Vb and semimetallic elements by making a specific atom content. CONSTITUTION:A mixed gas raw material of organic compound and H2 is activated by a heater such as thermal filament to synthesize diamond in a vapor phase. In this production method, one or more elements selected from metallic elements such as Ti, V or W of group IVa to group VIIa and group VIII of the periodic table, metallic elements of group IIIb to group Vb and semimetallic elements are fed as an additive element (1) in the form of a compound such as mono chloride together with the raw material gas to a reactor, (2) the additive element of the solid compound thereof is put in an excitation zone of the raw material gas in the reactor and evaporated by heating or sputtered by plasma and (3) the additive element is used as a thermoelectron irradiating material or the additive element is previously added to the thermoelectron irradiating material and the thermoelectron irradiating material is heated to a high temperature to give high-strength diamond containing 0.001-2.0wt.% of the additive element and further 0.001-0.2wt.% one or more of La, Ce, Th and Re.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high-strength vapor-phase synthetic diamond that can be applied to cutting tools and drilling tools.

[Conventional technology]

Sintered diamond, which is produced by sintering fine diamond powder and a metal binder under ultra-high pressure, is used in non-ferrous metal cutting tools, drill bits, wire drawing dies, etc. In recent years, the application of vapor-phase synthetic diamonds synthesized in a gas phase under low pressure to cutting tools and drilling tools has been considered, but sufficient performance has not yet been achieved.

[Problem to be solved by the invention]

The commonly used sintered diamond has the disadvantage of poor heat resistance. This is considered to be due to graphitization of diamond occurring at the interface between the diamond particles and the metal binder, and thermal stress caused by the difference in thermal expansion coefficient between the two. In order to improve this drawback, it has been proposed to treat the sintered body with acid to remove the metal binder, but since the removed metal parts become voids, the heat resistance improves but the strength decreases. There was a drawback that Also, Si and/or SiC can be used as a bonding material.
A heat-resistant sintered diamond containing . On the other hand, vapor-phase synthetic diamond consists essentially only of diamond and does not contain any binder, so it has good heat resistance. However, the bond between the diamond particles is weak because atoms do not interdiffuse at the grain boundaries due to necking, unlike in sintered diamond sintered under ultra-high pressure, resulting in low strength.

[Means to solve the problem]

The present inventors improved the heat resistance, which is a drawback of sintered diamond,
As a result of intensive studies to improve the mechanical strength of gas-phase diamonds, the present invention was achieved. That is,
Among the diamonds that are certified by the vapor phase method, the periodic table groups IVa, VA, VIa, VIIa, and VIII
Group metallic elements and group mb of the periodic table. (2) Contains at least one element selected from metal elements and metalloid elements of Group B and Group Vb, and the content thereof is o. By setting ooi% or more and 2.0% or less,
It was discovered that diamonds with excellent heat resistance and mechanical strength can be obtained.

In addition, it contains at least one or more elements selected from La, Ce, Th, and Re, and the content is 0.0 at %. They have found that the above-mentioned performance can be further improved by setting the content to 0.001% or more and 0.2% or less.

[For production]

One of the reasons why vapor-phase akai diamond has poor mechanical strength is that, unlike sintered diamond, diamond particles do not neck to each other and cause interdiffusion of atoms at grain boundaries, so the bonds at grain boundaries are weak. It is thought that this is because of this. Furthermore, when attempting to produce bulk diamond using vapor phase synthesis,
Unless special treatment is taken, the crystal grains will become coarse and the structure will become columnar, which is also thought to be the cause of the decrease in the strength of vapor-phase synthesized diamond. However, in the high-strength diamond of the present invention, high strength is achieved because the metal elements or metalloid elements contained exist in the grain boundaries and increase the strength of the grain boundaries, and also exist within the grains to increase the strength of the matrix. It seems likely that it will be done. In addition, when producing a bulk, the high-strength diamond of the present invention suppresses coarsening of crystal grains and obtains a dense structure, which also contributes to high strength. It is thought that this is the case. In the high-strength diamond of the present invention, when the diamond is elongated to a thickness of about 100 μm, the crystal grain size of the diamond observed from the top surface of the elongated diamond is suppressed to 15 μm or less. If the content of the additive element is less than the lower limit specified in the claims, this suppressing effect will not be clearly recognized.

Furthermore, among the elements added to the diamond of the present invention, those that easily bond with carbon (for example, 7i, Ta, Mo, W
etc.), when diamond is precipitated from the gas phase, it is thought that it combines with amorphous carbon and graphite that are precipitated at the same time to form carbides, which may prevent the precipitation of amorphous carbon and graphite. expected to have a deterrent effect. This also seems to contribute to higher strength.

In the present invention, the elements and contents contained in diamond are limited for the following reasons.

This is because it is difficult to add metal elements in Groups Ia and IIa of the periodic table to diamond, and it is also difficult to control their content. Regarding the metal elements of the ma group, La, C
This is because no clear effect was observed with elements other than e, Th, and Re.

Also, groups IVa, Va, VIa, and VIIa of the periodic table
Metallic elements of group VIII, group mb of the periodic table, group I
Containing at least one element selected from metal elements and metalloid elements of the Vb group and Vb group, and the content of which is 0.001% or more and 2.0% or less in atomic %, o. If it is less than ooi%, the improvement effect of increasing the strength of diamond will be insufficient, and if it is more than 2.0%, the strength will decrease. Among these elements, Ti, V, Nb, Ta, Cr,
Mo, W, Ni. B, Ag. Si,
N and P exhibit more favorable effects.

On the other hand, in addition to the above elements, La, Ce, Th, Re
Further increase in strength can be achieved by adding a small amount of , but the reason why the amount added is set to 0.001% or more and 0.2% or less in atomic % is because 0. If it is less than 0.001%, the effect of increasing the strength will be insufficient, and if it exceeds 0.2%, the strength will decrease.

The method for producing high-strength diamond of the present invention can use a commonly used diamond vapor phase synthesis method.

As a method for adding metals and metalloid elements, (1) A compound of the added element (chloride, fluoride, organometallic compound, etc.) is introduced into the reaction vessel as a gas source.

■Place the element or solid compound to be added into the excitation zone of the raw material gas inside the reaction vessel, or bring it close to it.
This is done by evaporating by heating or by sputtering with plasma.

(2) This is carried out by using an element added to the thermionic emitting material, or by adding the element to the thermionic emitting material in advance and heating the thermionic emitting material at a high temperature.

etc. are considered to be examples, but the method is not limited to these as long as the diamond of the present invention can be manufactured.

〔Example〕

Example 1 Hot filament using high-temperature heated thermionic emissive material for decomposition and activation of raw material gas}CVD method and JP-A-64-5
The thermionic emitting material disclosed in Publication No. 2699 is connected to the cathode and the base material or base material support is connected to the positive electrode to form a DC plasma, and thermal activation and plasma activation by the thermionic emitting material heated at high temperature are performed. A combination method was used. The thermionic emissive material has a diameter of 0.25mlB. 5lQ of length 120 arm
Fifteen pieces were strung at II+ intervals, and the distance from the base material was set to 5 mm. MO was used for the base material and the base material support, and a cooling support was further provided below, and the cooling capacity was adjusted to control the base material surface temperature at 980°C. The surface of the base material was previously scratched with No. 3000 diamond powder before synthesis.

Using the manufacturing conditions shown in Table 1, diamond was synthesized by adjusting the coalescence time so that the film thickness was approximately 100 μm.

Table 1 also shows the results of analyzing impurities in the diamond produced using an ion microanalyzer. Further, the crystal grain size of the top surface of the synthesized diamond was 25 μm for sample 8 and 20 μm for sample B, whereas it was 15 μm or less for all the other samples.

This sample was immersed in hot aqua regia, the Mo base material was dissolved and removed, and high-strength diamond was collected. In order to evaluate the performance of this high-strength diamond when used as a cutting tool, it was brazed to a cemented carbide alloy to create a cutting tip. As a comparison material, ultra-high pressure sintered diamond with an average particle size of 1 µm and containing 10% by volume of Co as a binder was used.
A cutting tip was prepared in the same manner. Aβ-12%Si alloy (AC
8A-T6), a cutting test was conducted under the conditions shown in Table 2. The results after cutting for 60 minutes are summarized in Table 3.

Table 3 Sample C using high strength diamond of the present invention. D,E
．． F and G exhibited good cutting properties and exhibited better performance than the sintered diamond used as a comparison material. On the other hand, Samples A, B, and H, which fall outside the scope of the present invention, develop defects in a short period of time and are judged to have lower strength than the products of the present invention and sintered diamond.

Example 2 Diamond was synthesized on a Si base material under the conditions shown in Table 4 using the microwave plasma CVD method generally used for vapor phase synthesis of diamond. As a method for incorporating the metal element or metalloid element of the present invention into diamond,
A method was adopted in which solid powders of oxides or chlorides of these elements were placed near the base material, exposed to plasma, heated at high temperature, and added into the diamond by evaporation or sputtering. At this time, the amount added to the diamond was adjusted by changing the size, amount, and location of the powder. An MO disk with a thickness of 31 mm was placed on a transparent quartz disk to serve as a substrate support. The pressure inside the reaction vessel was set at 100 Torr, and the substrate surface temperature was controlled at 1000° C. by adjusting the microwave output. The surface of the base material was previously scratched with No. 5000 diamond powder before synthesis. Diamond with a film thickness of about 120 μm was synthesized under each condition by adjusting the synthesis time. Table 4 also shows the results of analyzing impurities in the diamond produced using an ion microanalyzer. In addition, the crystal grain size on the top surface of the amalgamated diamond was 30 μm for sample (2), whereas it was 1 μm for all other samples.
It was less than 5μ.

Table 4 *: vo1% is volume % with respect to H2 This sample was immersed in a mixed solution of hydrofluoric acid and nitric acid, the Si base material was dissolved and removed, and high-strength diamond was collected. In order to evaluate the performance of this high-strength diamond when used as a cutting tool, it was brazed to a cemented carbide alloy to create a cutting tip. As a comparison material, a cutting tip was similarly produced using ultra-high pressure sintered diamond with an average grain i of 10 μm and containing 10% by volume of Co as a binder. A 7-rice cutting test was conducted under the conditions shown in Table J5 using an M-17% Si alloy (A390-T6) with a width of 100 mm and a length of 400 mm as a work material. The results after 20-pass cutting are summarized in Table 6.

Table 6 Sample J using high strength diamond of the present invention. K. M
and N exhibited good cutting properties, and showed better performance than sintered diamond used as a comparative material. On the other hand, the W of the present invention? Samples I, L, O, and P, which fall outside of the L range, were damaged in a short period of time and were judged to have lower strength than the products of the present invention and sintered diamond.

Example 3 Diamond was synthesized on a Mo base material under the conditions shown in Table 7 using the microwave plasma CVD method generally used for vapor phase synthesis of diamond. As a method for adding the metal element or metalloid element of the present invention to diamond, a method was adopted in which a compound of the added element was mixed in the form of a gas into a raw material gas, and the compound was incorporated into the diamond to be synthesized.

VOl% in the table means volume % with respect to C H 4 in the raw material gas, and WF. and N.H. First, a bomb was prepared in advance in which the solution was diluted with 80% to a predetermined concentration, and the solution was added.

T+Cj! n was added to a predetermined concentration using H2 as a carrier gas. A(l cl s is generated through H c(l and H2) to a generator containing an M chip, and H
The flow rate of C1 was adjusted to a predetermined concentration at tA. A Mo disk with a thickness of 3 ml Tl was placed on the quartz disk to serve as a base material support.

The pressure inside the reaction vessel was 80 Torr, and the substrate surface temperature was controlled at 950° C. by adjusting the microwave output. The surface of the base material was previously scratched with No. 3000 diamond powder before synthesis. Diamond having a film thickness of about 100μ was synthesized under each condition by adjusting the coalescence time. Table 8 also shows the results of analyzing impurities in the diamond produced using an ion microanalyzer. Note that the SIMS method was used for the analysis of N.

Table 8*: vo1% is CH. This sample was immersed in hot aqua regia, the old base material was dissolved and removed, and high-strength diamond was collected. In order to evaluate the performance of this high-strength diamond when used as a cutting tool, it was brazed to a cemented carbide alloy to create a cutting tip. As a comparative material, a cutting tip was similarly produced using ultra-high pressure sintered diamond with an average particle diameter of 10 μm and containing IO volume % of CO as a binder. Width 100mm as work material
A milling test was conducted using an ADC12 with a length of 400 mm under the conditions shown in Table 9. 30pass
The results after cutting are summarized in Table 10.

〔Effect of the invention〕

As explained above, the vapor phase synthesized diamond according to the present invention has higher strength than the conventional vapor phase synthesized diamond,
In addition, it has better wear resistance than sintered diamond, which is produced by sintering fine diamond powder and a metal binder under ultra-high pressure, so it is effective when used in fields such as wear-resistant tools, cutting tools, and drilling tools.

Claims (2)

[Claims] (1) In diamonds synthesized by vapor phase synthesis method,
The diamond belongs to Group IVa, Group Va, Group VIa of the periodic table,
Metal elements of group VIIa, group VIII and group IIIb of the periodic table,
It is characterized by containing at least one or more elements selected from metal elements and metalloid elements of group IVb and group Vb, and the content thereof is 0.001% or more and 2.0% or less in atomic %. High strength diamond. (2) Contains at least one element selected from La, Ce, Th, and Re, and the content is atomic%
A high-strength diamond characterized by having a content of 0.001 or more and 0.2%.