JP2007126329A - Diamond sintered body and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diamond sintered body having strength higher than that of a conventional one and excellent in wear resistance, and to provide a method for production of the same. <P>SOLUTION: The diamond sintered body includes diamond particles of ≥80 vol% but <98 vol%, a bonding material and vacancies. The bonding material comprises a solid solution including at least one element selected from the group consisting of titanium, zirconium, vanadium, niobium and chromium, carbon, and tungsten and further iron group elements. The diamond sintered body is characterized in that adjacent diamond particles are mutually bonded to each other. The method for production thereof is also provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a diamond sintered body that has high strength and wear resistance and is suitably used for a drawing die tool or the like.

  A diamond sintered body obtained by sintering diamond particles with a binder has excellent strength and wear resistance, and is therefore used for a drawing die or the like. In particular, a die made of a fine-grained diamond sintered body can provide a good line skin in wire drawing, and can have a much longer life than a die made of natural diamond.

  As a binder of the diamond sintered body, an iron group metal such as cobalt having catalytic ability to bond diamond particles is used, and these are contained in voids between the diamond particles. However, these have low hardness, and the iron group metal has a function of promoting graphitization and causes a problem of forming a deteriorated layer. Therefore, a method in which an iron group metal is removed by acid treatment after formation of a diamond sintered body is described in JP-A No. 53-114589 (Patent Document 1).

  However, in these diamond sintered bodies, the binder (iron group metal) is removed, and voids are generated in the sintered body, so that the strength is lowered. Accordingly, various diamond sintered bodies for tools (dies) have been proposed in which the problem of reduced die life due to the removal of iron group metals and the generation of vacancies has been proposed. For example, Japanese Patent Publication No. 1-27141 (Patent Document) For 2), sintering using a binder added with carbide, solid solution or mixed crystal of group 4a, 5a, 6a of the periodic table (groups 4, 5, 6 of the current periodic table) metal A body is disclosed (claim 1). In addition, as carbides of Group 4a, 5a, and 6a metals of the periodic table, tungsten carbide, molybdenum, tungsten, and a solid solution of carbon ((Mo, W) C) are disclosed (Claim 2).

Japanese Patent Application Laid-Open No. 11-245103 (Patent Document 3) discloses a method in which the iron group metal on the surface portion of the sintered body is removed more than the inside by acid treatment, and the decrease in the internal strength is suppressed. Yes. However, this sintered body has a problem that its surface portion has low strength.
JP-A-53-114589 Japanese Patent Publication No. 1-27141 (Claims 1 and 2) JP 11-245103 A

  An object of the present invention is to provide a diamond sintered body having higher strength and superior wear resistance than the conventional diamond sintered body as described above.

  As a result of intensive studies, the inventor contains, as a binder, a solid solution containing at least one element selected from the group consisting of titanium, zirconium, vanadium, niobium, and chromium, as well as an iron group element, carbon, and tungsten. When the content of diamond particles is within a predetermined range, a diamond sintered body having high strength and excellent wear resistance can be obtained even if iron group elements are removed from the sintered body by acid treatment or the like. As a result, the present invention has been completed.

The present invention according to claim 1,
A diamond sintered body containing diamond particles, a binder and pores,
The content of the diamond particles is 80% by volume or more and less than 98% by volume,
The binder includes at least one element selected from the group consisting of titanium, zirconium, vanadium, niobium, and chromium, a solid solution containing carbon and tungsten, and an iron group element.
A diamond sintered body characterized in that adjacent diamond particles are bonded to each other.

  The content of the diamond particles with respect to the total weight of the diamond particles and the binder is 80% by volume or more and less than 98% by volume. Here, the volume% refers to the ratio of the total volume of diamond particles to the total volume of the diamond sintered body including pores (hereinafter, volume% represents the same meaning). Since the binder has a hardness lower than that of diamond, by setting the content of diamond particles to 80% by volume or more, a decrease in hardness is prevented, and strength such as impact resistance and wear resistance are excellent. On the other hand, when the content of diamond particles is 98% by volume or more, the content of the iron group element at the time of sintering must be reduced, the catalytic ability cannot be sufficiently obtained, and neck growth does not progress. As a result, the strength tends to decrease.

  The diamond particles constituting the diamond sintered body of the present invention preferably have an average particle size of 2 μm or less. By reducing the average particle size to 2 μm or less, it is possible to suppress a decrease in strength of the diamond sintered body due to cleavage of the diamond particles. By using the above-mentioned binder and controlling the binder to be discontinuous to produce a diamond sintered body, a diamond sintered body having an average particle diameter in the above range can be obtained. A method and conditions for controlling the binder to be discontinuous are disclosed in JP-A-2005-239472.

  The diamond particles contained in the diamond sintered body of the present invention are characterized in that adjacent ones are bonded to each other. As a result of the adjacent diamond particles being bonded to each other, excellent strength is obtained. Such a bond is a process of dissolving and re-depositing raw diamond powder to form diamond crystals, and a direct bond called neck growth is formed between the diamond powders by a binder having catalytic ability such as an iron group element. Can be obtained.

  The binder constituting the diamond sintered body of the present invention is composed of an iron group element having catalytic ability to precipitate diamond crystals and form neck growth between diamond particles, and titanium, zirconium, vanadium, niobium, and chromium. A solid solution of at least one element selected from the group (hereinafter referred to as element Z), carbon and tungsten.

  The solid solution is not easily dissolved or removed by the acid treatment described later, and has a higher hardness than iron group elements. Therefore, the binder containing the solid solution has a high hardness, and further, the hardness of the diamond sintered body is high. improves. In addition, since chemical reaction resistance such as heat resistance and oxidation resistance is increased, wear resistance is increased. Furthermore, since strength is increased by solid solution strengthening, fracture resistance (bending strength) and impact resistance are increased. As a result, it exhibits excellent performance in wire drawing die applications.

  The solid solution includes a carbide of the element Z. When the solid solution contains the carbide of the element Z, it is difficult to be dissolved or removed by the acid treatment, and the strength and wear resistance of the diamond sintered body are improved. Even when elements of Group 4, 5, or 6 of the periodic table contain elements other than element Z, for example, molybdenum carbide, they are dissolved by acid treatment as compared with the case of containing element Z carbide. Since it is easy, strength and abrasion resistance are insufficient.

  The solid solution includes a carbide of tungsten together with a carbide of element Z. By including both the carbide of element Z and the carbide of tungsten, the strength and wear resistance are further improved, and the strength is superior to the prior art diamond sintered body containing only one of carbide of element Z and carbide of tungsten. And wear resistance.

  The element Z, tungsten and carbon contained in the binder form a solid solution. By forming a solid solution, it is possible to obtain further superior strength and wear resistance than the conventional diamond sintered body. If the carbide of the element Z and the carbide of tungsten are mixed without forming a solid solution, excellent strength cannot be obtained.

  The solid solution may further contain oxygen, nitrogen, and the like. These elements, particularly nitrogen, are often taken into the binder in the process of forming the diamond sintered body.

  The diamond sintered body of the present invention has pores in the gap between the particles together with the binder contained in the gap between the diamond particles. These vacancies are added as a catalyst for the growth of diamond particles and the bonding between the particles, and unavoidable when the iron group elements contained in the binder are removed by acid treatment after sintering. It happens.

  Since the voids reduce the strength of the diamond sintered body and reduce the life of the wire drawing, it is desired that the content be small, and preferably less than 10% by volume. However, in order to reduce the vacancy content, it is necessary to reduce the iron group element content during sintering. In this case, there is a problem such as insufficient neck growth and reduced strength. Since it tends to occur, the pores are contained at least 0.1% by volume or more. Claim 2 corresponds to this preferable mode.

  The present invention further provides the following configuration as a preferred embodiment of the diamond sintered body.

  The diamond sintered body, wherein the content of the solid solution containing at least one element selected from the group consisting of titanium, zirconium, vanadium, niobium, and chromium, carbon, and tungsten is 0.1% by volume or more. The diamond sintered body is characterized by being less than 15 volume% and having an iron group element content of not less than 0.1 volume% and less than 3 volume% (Claim 3).

  When the content of the solid solution containing the element Z, carbon and tungsten is less than 0.1% by volume, it becomes difficult to obtain excellent strength and wear resistance. On the other hand, when the content exceeds 15% by volume, In this case, the content of the iron group element has to be reduced, and in this case, neck growth does not easily progress and the strength tends to decrease.

  On the other hand, when the content of the iron group element exceeds 3% by volume, problems such as acceleration of graphitization and reduction in strength tend to occur. On the other hand, in order to reduce the content of iron group elements to less than 0.1% by volume, it is necessary to increase the acid treatment conditions such as increasing the acid treatment time and using a strong acid for the acid treatment In this case, the solid solution is easily dissolved. Further, even if an iron group element of about 0.1% by volume is contained, excellent strength and wear resistance can be obtained. Therefore, the content of the iron group element is preferably 0.1% by volume or more.

  In the diamond sintered body, the component ratio of at least one element selected from the group consisting of titanium, zirconium, vanadium, niobium, and chromium in the solid solution to tungsten is 0.00. A diamond sintered body characterized by being in the range of 4 or more and 15.0 or less (Claim 4). In the solid solution, the component ratio of element Z to tungsten is atomic ratio, and in the range of 0.4 ≦ element Z / tungsten ≦ 15.0, more excellent strength and wear resistance can be obtained. A drawing life is achieved. Among these ranges, the range of 0.4 ≦ element Z / tungsten ≦ 3.0 is particularly preferable, and a longer wire drawing life is achieved.

  The diamond sintered body, wherein the element Z, that is, at least one element selected from the group consisting of titanium, zirconium, vanadium, niobium, and chromium is titanium. (Claim 5). Among the elements Z, when titanium is used, the solid solution is difficult to be dissolved by the acid treatment, the strength and wear resistance of the sintered body are more excellent, and the wire drawing life is increased.

  The diamond sintered body according to claim 6, wherein the iron group element is cobalt. Examples of the iron group element include iron, nickel, and cobalt. Among them, cobalt is preferable because of its high catalytic ability.

The diamond sintered body of the present invention is
A step of mixing at least one element selected from the group consisting of titanium, zirconium, vanadium, niobium, and chromium (element Z), carbon and tungsten, an iron group element, and diamond particles;
The obtained mixture is sintered under high temperature and high pressure where diamond is thermodynamically stable, and the solid solution of the element Z, carbon and tungsten, the binder containing the iron group element, and adjacent particles are mutually bonded. It can be manufactured by a method characterized by having a step of forming a sintered body X containing bonded diamond particles and a step of eluting the iron group element by acid treatment of the sintered body X. The present invention also provides this manufacturing method (claim 7).

  The step of mixing the element Z, carbon and tungsten, the iron group element, and the diamond particles is performed by, for example, dry-mixing the powder of the solid solution of the element Z, carbon, and tungsten, the powder of the iron group element, and the diamond particles. be able to. Thus, if it sinters after dry-mixing, what contains the solid solution of the element Z, carbon, and tungsten as a binder of the sintered compact X is obtained. The solid solution mixed with the iron group element and the diamond particles is prepared by mixing the carbide powder of the element Z and the carbide powder of tungsten separately from the diamond particles, and then heating and heating to 1300 ° C. and 3 GPa or more at which these solid solutions. It can be obtained by pressing. The obtained solid solution is pulverized and mixed using a ball mill or the like.

  The solid solution powder is preferably added as particles having an average particle diameter of 0.8 μm or less so as to be discontinuous with each other. By controlling so as not to be continuous, the diamond particles are likely to neck-grow with each other, a strong skeleton is formed, and the strength is improved.

  The iron group element powder may be a metal powder, or a ceramic powder made of a carbide of these elements. However, a stronger diamond bond is often obtained when metal powder is used.

  Instead of dry mixing the solid solution powder, the iron group element powder, and the diamond powder, the surface of the diamond powder is made by using a PVD (Physical Vapor Deposition) method or the like, and the element Z, the carbide of the element Z, and the element One or more selected from a solid solution of Z carbide and tungsten carbide may be discontinuously coated on 20 to 80% of the surface area of the diamond powder. Even if only element Z or carbide of element Z is coated by the PVD method and other components are mixed with powder, a solid solution of element Z, tungsten and carbon is produced in the sintering process, and strength, wear resistance, etc. It is thought that a diamond sintered body excellent in the above can be obtained. However, when tungsten carbide is coated by the PVD method and other components are mixed with powder, a solid solution of element Z, tungsten and carbon is not generated in the sintering process.

  Sintering is performed by holding the mixture in a mold of an ultrahigh pressure generator for about 10 minutes, preferably at a pressure of 5.0 GPa or more and 8.0 GPa or less and a temperature of 1500 ° C. or more and 1900 ° C. or less. be able to. Considering the durability of the mold, a pressure greater than 8.0 GPa is less practical. If the temperature is higher than 1900 ° C., the diamond-graphite is easily graphitized because it exceeds the equilibrium line of diamond-graphite and enters the stable region of graphite. Considering the durability of the die of the ultrahigh pressure generator and the performance of the diamond sintered body, the pressure should be maintained for about 10 minutes under the conditions of 5.7 GPa or more and 7.7 GPa or less and the temperature of 1500 ° C. or more and 1900 ° C. or less. Is more preferable.

  The content of the solid solution in the binder after sintering and before acid treatment is preferably 1% by weight or more and less than 50% by weight. When the solid solution content is smaller than the above range, it is difficult to obtain excellent strength and wear resistance. On the other hand, when the solid solution content is larger than the above range, the ratio of the iron group element is small. Further, it is difficult to obtain sufficient catalytic ability to promote neck growth of diamond particles, and as a result, problems such as a decrease in strength tend to occur.

  After sintering, the diamond sintered body is subjected to acid treatment, and iron group elements in the binder are eluted. However, some iron group elements remain in the binder even after acid treatment. As a result of elution of the iron group element from the binder, voids are formed in the diamond sintered body.

  The acid treatment can be performed by a method of immersing the diamond sintered body in an acid solution in which an iron group element is dissolved. As the acid solution, a solution containing at least one selected from the group consisting of nitric acid and hydrochloric acid is preferably exemplified because it sufficiently dissolves an iron group element and hardly dissolves a solid solution. Claim 8 corresponds to this aspect. In particular, aqua regia, which is a mixture of nitric acid and hydrochloric acid, is preferably used.

  The diamond sintered body obtained as described above is further superior in strength and wear resistance to conventional diamond sintered bodies, and is suitably used for a drawing die tool and the like. The drawing die tool can be manufactured by making a hole in the diamond sintered body with a laser and lapping the hole.

  The diamond sintered body of the present invention is a sintered body having pores formed by removing an iron group element contained as a binder in the sintered body by an acid treatment. It has higher strength and superior wear resistance than a diamond sintered body having pores. Therefore, it is suitably used for a drawing die tool that requires excellent strength and wear resistance. When wire drawing is performed with a wire drawing die tool using this diamond sintered body, a good surface state of wire drawing and a long wire drawing life can be obtained.

  This diamond sintered body can be easily obtained by the method for producing a diamond sintered body of the present invention.

  Next, the present invention will be described more specifically with reference to examples. The examples are not intended to limit the scope of the invention.

  Diamond sintered compacts A to I of the binder components shown in Table 1 were manufactured, saw wire (brass plated steel wire) was drawn, and the drawing life was measured. Here, the wire drawing life is one of the following: the wire drawing is linearly thickened and the wire diameter and roundness are out of specification, or the color tone decreases when the color tone of the wire drawing is measured visually or with a color difference meter. Expressed by the weight of the wire drawn until it occurs. Sintered bodies C, D, and F to I are examples of the present invention, and sintered bodies A, B, and E are comparative examples.

(Manufacture of diamond sintered body)
Using diamond powder with an average particle diameter of 1 μm, cobalt powder as a binder, and carbides (solid solution) shown in Table 1, dry mixing at the mixing ratio shown in Table 1 (volume% of each component with respect to the total capacity of diamond, carbide, and cobalt) Mixing was performed. The carbide used in the manufacture of the sintered bodies A and B is tungsten carbide. The carbide used in the production of the sintered bodies C to I is a mixture of carbide of each element shown in Table 1 (titanium, chromium or molybdenum) and tungsten carbide powder in the atomic ratio shown in Table 1, pressure: 5 .5 GPa, temperature: produced by pulverizing a solid solution obtained by holding for 5 minutes under the conditions of 1400 ° C.

  The mixture thus obtained is filled in a tantalum container in contact with a substrate (disk) formed of a cemented carbide, and using a belt type ultra-high pressure device, pressure: 5.8 GPa, Sintering was performed for 10 minutes at a temperature of 1500 ° C. to obtain a diamond sintered body. The obtained diamond sintered body was acid-treated by immersing the nitric acid having a concentration of 60% or more and less than 65% twice in an airtight container for 100 hours at 80 ° C. or more and less than 100 ° C.

(Measurement of cobalt and carbide content)
Cobalt and carbide contained in each of the diamond sintered bodies obtained above were measured by XRD (X-ray diffraction), TEM (transmission electron microscope), and AES (Auger electron spectroscopy). Was detected. Each element was quantitatively measured by a high frequency induction plasma emission analysis method (ICP method), and each content (volume% with respect to the total capacity of the diamond sintered body) was calculated. Further, the void volume% was calculated by the following method. These calculated values are shown in Table 1.

  Method for calculating the volume% of vacancies: Calculate the volume% of cobalt and carbide before and after acid treatment, and assume that the volume% of diamond particles does not change. Was defined as the void volume%.

  After acid treatment, a pilot hole was drilled by laser processing and lapped to produce a die having a hole diameter of 0.175. Using this die, a saw wire (brass-plated steel wire) was drawn by a wet method at a wire speed of 850 m / min. The results are shown in Table 2.

  Sintered bodies A and B have a high ratio of cobalt in the raw material powder and contain only tungsten carbide as a carbide. Most of cobalt is dissolved by acid treatment, and part of tungsten carbide is also dissolved, resulting in a high void ratio. It has become. As a result, the surface condition of the wire after wire drawing is poor and the wire drawing life is short. On the other hand, in the sintered bodies C, D, and F to I in which tungsten forms a solid solution with the elements Z and carbon, cobalt is dissolved by the acid treatment, but the dissolution of the solid solution is small, so the void ratio is low. As a result, the surface condition of the wire after drawing is good and the drawing life is long.

  Among them, in the case of sintered bodies C and F to I using titanium as the element Z, the dissolution of the solid solution is particularly small, and there is also an action as a binder of the solid solution, and the longest wire drawing life was obtained. . However, in the sintered body E using molybdenum instead of titanium or chromium as the element Z, the solid solution dissolves more than in the case of the sintered bodies C, D and F to I, and as a result, the wire drawing life is also reduced. Shorter than in cases of Conjugates C, D and FI. Among the sintered bodies C and F to I using titanium as the element Z, the sintered bodies I, F, G have a long wire drawing life and the titanium / tungsten is less than 0.4. In the sintered body H having more than 15 titanium / tungsten, the wire drawing life tends to be shortened.

  Using the sintered bodies A to I manufactured in Example 1, the stainless steel wire (SUS304) was drawn to measure the drawing life. In the same manner as in Example 1, the sintered bodies A to I were acid-treated with hydrofluoric acid, then a pilot hole was drilled by laser processing and lapped to produce a die having a hole diameter of φ0.4. Using this die, a stainless steel wire (SUS304) was drawn by a wet method at a drawing speed of 400 m / min. The results are shown in Table 3.

As Table 3 shows, the same results as in Example 1 were obtained when a stainless steel wire was used instead of the saw wire. That is, in the sintered bodies C, D and F to I in which tungsten forms a solid solution with the elements Z and carbon, the sintered bodies A and B in which the wire drawing life is long but tungsten does not form a solid solution, In the case of the sintered body E using a solid solution containing molybdenum, the wire drawing life is shorter than that of the sintered bodies C, D and F to I.

Claims (8)

A diamond sintered body containing diamond particles, a binder and pores,
The content of the diamond particles is 80% by volume or more and less than 98% by volume,
The binder includes at least one element selected from the group consisting of titanium, zirconium, vanadium, niobium, and chromium, a solid solution containing carbon and tungsten, and an iron group element.
A diamond sintered body characterized in that adjacent diamond particles are bonded to each other.   The diamond sintered body according to claim 1, wherein the content of pores is 0.1 volume% or more and less than 10 volume%.   The content of the solid solution containing at least one element selected from the group consisting of titanium, zirconium, vanadium, niobium, and chromium, carbon and tungsten is 0.1% by volume or more and less than 15% by volume, 3. The diamond sintered body according to claim 1, wherein an element content is 0.1 volume% or more and less than 3 volume%.   The atomic ratio of at least one element selected from the group consisting of titanium, zirconium, vanadium, niobium, and chromium in the solid solution is in the range of 0.4 or more and 15.0 or less. The diamond sintered body according to any one of claims 1 to 3, wherein   The diamond sintered body according to any one of claims 1 to 4, wherein at least one element selected from the group consisting of titanium, zirconium, vanadium, niobium, and chromium is titanium.   The diamond sintered body according to any one of claims 1 to 5, wherein the iron group element is cobalt. Mixing at least one element selected from the group consisting of titanium, zirconium, vanadium, niobium, and chromium, carbon and tungsten, an iron group element, and diamond particles;
The obtained mixture is sintered under high temperature and high pressure where diamond is thermodynamically stable, and the solid solution of the element, carbon and tungsten, the binder containing the iron group element, and adjacent particles are bonded to each other. A method for producing a diamond sintered body comprising a step of forming a sintered body X containing diamond particles, and a step of acid-treating the sintered body X to elute iron group elements. The diamond sintered body according to claim 7, wherein the acid treatment is performed by immersing the sintered body X in an acid solution containing at least one selected from the group consisting of nitric acid and hydrochloric acid. Production method.