JPH0967164A - Diamond sintered compact and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a diamond sintered compact having chipping, heat and acid resistances under conditions capable of industrial production. SOLUTION: This diamond sintered compact consists of 0.1-30vol.% material made of a compd. contg. Si, Ti and O and the balance diamond, and a silicon oxide-titanium oxide mixture is used as a sintering aid. This powder is mixed with diamond powder, non-diamond powder or a mixture of them and the resultant mixture is sintered by holding under conditions of pressure and temp. in a region in which diamond is thermodynamically stable.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a diamond sintered body and a method for producing the same. INDUSTRIAL APPLICABILITY The diamond sintered body of the present invention can be effectively used as a material for cutting non-ferrous metals, ceramics and the like, as a material for grinding tools and as a blade edge material for drill bits for petroleum excavation applications.

[0002]

2. Description of the Related Art As a conventional diamond sintered body, one using an iron group metal such as Co, Ni or Fe as a sintering aid or a binder and one using a ceramic such as SiC is known. And is industrially used for non-ferrous metal cutting tools and excavation bits. In addition, there is known one using a carbonate as a sintering aid (Japanese Patent Laid-Open No. Hei 4-
No. 74766, JP-A-4-114966).
In addition, there is a natural diamond sintered body (carbonate), but it is rarely used industrially because of the large variation in the material and the extremely small production amount.

[0003]

A diamond sintered body using an iron group metal such as Co as a sintering aid has poor heat resistance because the iron group metal such as Co acts as a catalyst for promoting the graphitization of diamond. . That is, in an inert gas atmosphere,
It is graphitized at about 700 ° C. Further, since a metal such as Co exists as a continuous phase in the grain boundary of the diamond grain, the strength of the sintered body is not so high and chipping easily occurs. There is also a problem that thermal deterioration easily occurs due to the difference in thermal expansion between the metal and diamond. It is also known that the above-mentioned metal at the grain boundary is removed by an acid treatment in order to increase heat resistance. As a result, the heat-resistant temperature is improved to about 1200 ° C., but the sintered body becomes porous, so that the strength is further significantly reduced (about 30%). The diamond sintered body using SiC as a binder has excellent heat resistance, but the diamond grains do not bond to each other and thus have low strength. On the other hand, a diamond sintered body using carbonate as a sintering aid is superior in heat resistance to a sintered body using a Co binder, but 1
From around 000 ° C., decomposition of carbonate starts and the strength of the sintered body decreases. In addition, since carbonate dissolves in acid, it cannot be used for applications such as excavating bits. The present invention intends to solve the above problems and provide a diamond sintered body having fracture resistance, heat resistance and acid resistance, and a method for producing the same.

[0004]

As a means for solving the above problems, the present invention is a diamond in which 0.1 to 30% by volume of a substance consisting of a compound containing silicon, titanium and oxygen and the balance is diamond. Provide a sintered body.
Further, there is provided a diamond sintered body, wherein the compound containing silicon, titanium and oxygen is a complex oxide or a solid solution composed of an oxide of silicon and an oxide of titanium.

Further, the present invention uses a mixture of silicon oxide and titanium oxide as a sintering aid in the method for producing this diamond sintered body, and this powder, diamond powder or non-diamond carbon powder, or diamond and non-diamond. Provided is a method of mixing a mixed powder of carbon, holding the mixed powder under the pressure and temperature conditions in the thermodynamically stable region of diamond, and sintering the mixture. As another method for producing this diamond sintered body, a mixture of silicon oxide and titanium oxide is used as a sintering aid, and a compact of this powder, a compact of diamond powder or a compact of non-diamond carbon powder, or diamond. Provided is a method of laminating a compact of a mixed powder of non-diamond carbon, holding it under the pressure and temperature conditions of the thermodynamically stable region of diamond, and sintering it. Further, as a sintering aid, the proportion of titanium oxide in the mixture of silicon oxide and titanium oxide is 0.1 to 5% by volume.
A method using a mixture that is 0 is provided. Furthermore, a method of using silicic acid or a hydrate of silicon oxide instead of the above-mentioned silicon oxide as a sintering aid is provided.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Heretofore, there has been no example in which a mixture of silicon oxide or silicic acid and titanium oxide is used as an effective sintering aid for a diamond sintered body. Now, the inventors of the present invention, by using a mixture of silicon oxide or silicic acid and titanium oxide as a sintering aid, have diamond sintering with unprecedented high strength and excellent in fracture resistance, heat resistance, and corrosion resistance. It has been found that a body can be obtained, which led to the present invention. That is,
A feature of the present invention is that a mixture of silicon oxide (SiO ₂ ) and titanium oxide (TiO ₂ ) is used as a sintering aid for a diamond sintered body. H ₄ Si instead of silicon oxide
Silicic acid such as O ₄ , H ₂ SiO ₃ , and H ₂ Si ₂ O ₂ ;
A hydrate such as SiO ₂ or nH ₂ O may be used.

The mixture of silicon oxide or silicic acid and titanium oxide has a strong catalytic action on diamond, and when these are used as a sintering aid, a matrix in which diamond particles are extremely strongly bonded is formed. Further, abnormal grain growth is unlikely to occur, and a sintered body having a uniform structure can be obtained. As a result, it is possible to obtain a diamond sintered body having a high strength, which is unprecedented, and excellent in fracture resistance and abrasion resistance.

The diamond sintered body thus obtained is
It is characterized in that it includes a substance composed of a compound containing silicon, titanium and oxygen, and examples of such a substance include a complex oxide or a solid solution of silicon oxide and titanium oxide. Such a substance is stable even at a high temperature of about 1500 ° C., and is also stable to acids and alkalis. Therefore, the diamond sintered body of the present invention has excellent heat resistance and corrosion resistance.

In the diamond sintered body of the present invention, the content of the substance composed of the compound containing silicon, titanium and oxygen is preferably 0.1 to 30% by volume, and the reason is that if the content is less than 0.1% by volume, diamond is contained. Connectivity between particles,
That is, the sinterability decreases, and if it exceeds 30% by volume, the strength and the wear resistance decrease due to the influence of the excess compound. As the raw material, synthetic diamond powder, natural diamond powder, polycrystalline diamond powder and the like can be used. The particle size of the powder is 0.01 to 200 μm, and a particle having a uniform particle size or a coarse particle or a mixture of fine particles and coarse particles is used depending on the application. Further, instead of these diamonds, non-diamond such as graphite, glassy carbon, and pyrolytic graphite can be used as a raw material. Also, a mixture of diamond and these non-diamond graphites can be used. The particle size of the silicon oxide or titanium oxide powder used as a sintering aid is 0.01 to 30 μm, and when the sintering aid and the diamond powder of the raw material are mixed and sintered, compared with the diamond powder used as the raw material. However, it is preferable that these particle sizes are small.

As a method for producing a diamond sintered body of the present invention, diamond powder or non-diamond powder and a mixture of silicon oxide and titanium oxide are held under a pressure and temperature condition at which diamond is thermodynamically stable. There is a method and a method of holding a molded body of diamond powder or non-diamond graphite and a molded body of a mixture of silicon oxide and titanium oxide as a raw material, and holding the material under the above-mentioned pressure and temperature conditions. Here, as the mixture of silicon oxide and titanium oxide, the proportion of titanium oxide is preferably 0.1 to 50% by volume. If the proportion of titanium oxide is less than 0.1% or more than 50%, sintering will be insufficient, and in order to obtain a strong sintered body, 2500 ° C. or higher, 8
Very high sintering temperature and pressure conditions of GPa or higher are required,
Industrial production is difficult. When silicon oxide simple substance or titanium oxide simple substance is used as a sintering aid, more severe pressure temperature conditions are required. Further, silicic acid or a hydrate of silicon oxide can be used instead of silicon oxide. In this case, a strong sintered body can be obtained even if the sintering temperature is slightly low.
In the method of mixing the raw material and the sintering aid, the raw material and the sintering aid are subjected to high-pressure high-temperature sintering by mechanically dry- or wet-mixing powder compression-molded or filled in a capsule such as Mo. To do. Even if the raw material powder is fine, the sintering aid can be uniformly dispersed, and a thick diamond sintered body can be manufactured. For example, it is suitable for manufacturing a cutting tool (fine-grained sintered body) that requires a good finished surface and a sintered body that requires a thick shape such as a die. However, when a coarse-grain raw material is used, it is difficult to uniformly mix the sintering aid. On the other hand, in the method of stacking and placing the raw material and the sintering aid, plate-shaped compacts of the raw material and the sintering aid are prepared, and these are stacked and brought into contact with each other, and subjected to high-pressure and high-temperature treatment. At this time, the raw material layer is diffused and impregnated with the sintering aid, and the diamond particles are sintered. With this method, even if a coarse-grained raw material is used, the sintering aid can be added uniformly, so that a diamond sintered body with higher strength and wear resistance can be stably obtained. Suitable for manufacturing sintered bodies such as bits.

[0011]

EXAMPLES The present invention will be described in more detail below, but the present invention is not limited thereto. (Example 1) SiO _{2 having a} particle size of 1 to ₂ μm as a sintering aid
And a mixture of TiO ₂ was used. A mixture of SiO ₂ and TiO ₂ was used in a volume ratio of 3: 2 (TiO ₂ , 40% by volume). A synthetic diamond powder having an average particle size of 3.5 μm and powder of the above mixture were sufficiently mixed at a ratio of 95% by volume and 5% by volume, respectively, and the mixture was put into a Mo capsule, and a belt type ultrahigh pressure and high temperature generator was installed. Use 7.
The pressure and temperature conditions of 5 GPa and 2000 ° C. were maintained for 15 minutes for sintering. When the composition of the obtained diamond sintered body was identified by X-ray diffraction, about 5% by volume of a composite oxide of silicon oxide and titanium oxide was detected in addition to diamond. When the hardness of this sintered body was evaluated by a Knoop indenter, it was 6800 kg / mm ² , which was a high hardness. Further, when the fracture toughness was compared with the conventional commercially available Co binder sintered body by the indentation method, the relative toughness was about 1.3 times that of the conventional sintered body. Further, the obtained sintered body was heat-treated at 1200 ° C. in vacuum and then the hardness and toughness were measured, but there was almost no change from that before the treatment. No deterioration of the sintered body due to the acid treatment was observed.

(Example 2) SiO ₂ and Ti as sintering aids
A diamond sintered body was produced in the same manner as in Example 1 except that the volume ratio of O ₂ was 5: 1. The obtained sintered body contained a composite oxide of silicon oxide and titanium oxide, and had the same hardness, toughness, and heat resistance as in Example 1.

(Example 3) Diamond sintering was carried out in the same manner as in Example 1 except that a mixture of silicic acid anhydride (H ₃ SiO ₃ ) and TiO _{2 in} a volume ratio of 2: 1 was used as a sintering aid. The body was made. The obtained sintered body contained a composite oxide of silicon oxide and titanium oxide, and had the same hardness, toughness, and heat resistance as in Example 1.

Example 4 A diamond sintered body was prepared in the same manner as in Example 1 except that a mixture of orthosilicic acid (H ₄ SiO ₄ ) and TiO _{2 in} a volume ratio of 3: 1 was used as a sintering aid. Was produced. The obtained sintered body contained a composite oxide of silicon oxide and titanium oxide, and had the same hardness, toughness, and heat resistance as in Example 1.

(Example 5) Particle size of 1 to 2 μm as a sintering aid
A mixture of SiO ₂ and TiO ₂ of m in a volume ratio of 3: 2 was used. A synthetic diamond powder having an average particle diameter of 15 μm and a mixture of the above-mentioned mixed powders each having a thickness of 2 mm and 1 mm were alternately laminated and placed in a Mo capsule. 2000 ° C
The pressure and temperature conditions were maintained for 15 minutes for sintering. When the composition of the obtained diamond sintered body was identified by X-ray diffraction, about 2% by volume of a composite oxide of silicon oxide and titanium oxide was detected in addition to diamond. When the hardness of this sintered body was evaluated with a Knoop indenter, it was about 7200 kg.
The hardness was as high as / mm ² . Further, when the fracture toughness was compared with the conventional commercially available Co binder sintered body by the indentation method, the relative toughness was about 1.4 times that of the conventional sintered body. In addition, the obtained sintered body is
After heat treatment at 200 ° C, the hardness and toughness were measured.
There was almost no change from before treatment. No deterioration of the sintered body due to the acid treatment was observed.

Example 6 A diamond sintered body was prepared in the same manner as in Example 5 except that a mixture of silicic acid anhydride (H ₃ SiO ₃ ) and TiO _{2 in} a volume ratio of 2: 1 was used as a sintering aid. Was produced. The obtained sintered body contained a composite oxide of silicon oxide and titanium oxide, and had the same hardness, toughness, and heat resistance as in Example 5.

Example 7 SiO ₂ and T as sintering aids
A mixture of iO _{2 in} a volume ratio of 3: 2 was used. Average particle size 3μ
A plate-shaped compact of high-purity isotropic graphite having a thickness of 2 mm and a mixture of the above-mentioned mixed powders having a thickness of 1 mm and embossed were alternately laminated and put in a Mo capsule, and a belt-type ultrahigh-pressure high-temperature generator was prepared. It was used for 15 minutes under a pressure temperature condition of 7.5 GPa and 2000 ° C. to be sintered. When the composition of the obtained diamond sintered body was identified by X-ray diffraction, about 3% by volume of a composite oxide of silicon oxide and titanium oxide was detected in addition to diamond. When the hardness of this sintered body was evaluated by a Knoop indenter, it was about 7,000 kg / m.
It had a high hardness of m ² . Further, when the fracture toughness was compared with that of the conventional commercially available Co binder sintered body by the indentation method, the relative toughness was about 1.2 times that of the conventional sintered body. In addition, the obtained sintered body is vacuumed to 120
After heat treatment at 0 ° C., hardness and toughness were measured, but there was almost no change from that before treatment. No deterioration of the sintered body due to the acid treatment was observed.

(Comparative Example 1) SiO ₂ and T as sintering aids
A mixture of iO _{2 in} a volume ratio of 3: 2 was used. Average particle size 3.
A diamond sintered body was manufactured in the same manner as in Example 1 except that a small amount of the above-mentioned mixture powder (about 0.05% by volume) was added to 5 μm synthetic diamond powder and the mixture was sufficiently mixed. I tried. However, many unsintered parts remained in the obtained sintered body.

(Comparative Example 2) SiO ₂ and T as sintering aids
A mixture of iO _{2 in} a volume ratio of 3: 2 was used. Average particle size 3.
An attempt was made to manufacture a diamond sintered body in the same manner as in Example 1, except that 60% by volume of 5 μm synthetic diamond powder and 40% by volume of the powder of the above mixture were added and sufficiently mixed. However, in the obtained sintered body, the particles were not sufficiently bonded to each other, and the hardness was as low as 3500 kg / mm ² .

(Comparative Example 3) An attempt was made to manufacture a diamond sintered body in the same manner as in Example 1 except that only SiO ₂ was used as a sintering aid. However, many unsintered parts remained in the obtained sintered body.

(Comparative Example 4) An attempt was made to manufacture a diamond sintered body in the same manner as in Example 1 except that only TiO ₂ was used as a sintering aid. However, many unsintered parts remained in the obtained sintered body.

Comparative Example 5 An attempt was made to manufacture a diamond sintered body in the same manner as in Example 1 except that only silicic acid anhydride was used as a sintering aid. However, many unsintered parts remained in the obtained sintered body.

[0023]

As described above, since the diamond sintered body of the present invention has unprecedented high strength, heat resistance, fracture resistance and corrosion resistance, it can be used for cutting and grinding tools such as non-ferrous metals and ceramics. In addition to the material, it can be effectively used as a blade edge material for drill bits for oil excavation.

Claims (6)

[Claims] 1. A diamond sintered body characterized by containing 0.1 to 30% by volume of a substance consisting of a compound containing silicon, titanium and oxygen, and the balance being diamond. 2. The diamond sintered body according to claim 1, wherein the compound containing silicon, titanium and oxygen is a complex oxide or a solid solution containing an oxide of silicon and an oxide of titanium. 3. A mixture of silicon oxide and titanium oxide is used as a sintering aid, and this powder is mixed with a diamond powder or a non-diamond carbon powder or a mixed powder of diamond and non-diamond carbon, which is then subjected to thermodynamics of diamond. The method for producing a diamond sintered body according to claim 1 or 2, characterized in that the diamond sintered body is held under the pressure and temperature conditions of a mechanically stable region and then sintered. 4. A mixture of silicon oxide and titanium oxide is used as a sintering aid, and a compact of this powder, a compact of diamond powder or a compact of non-diamond carbon powder, or a mixed powder of diamond and non-diamond carbon. The method for producing a diamond sintered body according to claim 1 or 2, which comprises laminating a compact with a compact, holding the compact under a pressure and temperature conditions in a thermodynamically stable region of diamond, and sintering the compact. 5. The proportion of titanium oxide in the mixture of silicon oxide and titanium oxide as a sintering aid is 0.1 to 50% by volume.
%, The method for producing a diamond sintered body according to claim 3 or 4, wherein 6. The method for producing a diamond sintered body according to claim 3, wherein the sintering aid silicon oxide is silicic acid or a hydrate of silicon oxide.