JP2007126326A - Diamond sintered body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diamond sintered body having a hardness higher than that of a conventional one and excellent in strength such as chipping resistance, wear resistance or the like. <P>SOLUTION: The diamond sintered body includes diamond particles and a bonding material. The bonding material comprises a solid solution including at least one element selected from the group consisting of titanium, zirconium, vanadium, niobium and chromium, and carbon and tungsten. The material further includes iron group elements represented by cobalt. The diamond sintered body is characterized in that adjacent diamond particles are mutually bonded to each other. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a diamond sintered body that has high hardness, fracture resistance, and wear resistance, and is suitably used for cutting tools of cutting tools such as turning tools and end mills.

  A diamond sintered body obtained by sintering diamond particles with a binder has high hardness, and is not widely used as a material for cutting tools and the like because it does not easily cause a defect due to cleavage, which is a defect of single crystal diamond. As a method for producing the diamond sintered body, for example, a diamond powder is dissolved and reprecipitated using a binder made of a solvent metal having catalytic ability typified by iron group elements such as cobalt, iron, nickel, and the like. A method for forming a direct bond called neck growth between particles is disclosed in Japanese Patent Publication No. 39-20483 (Patent Document 1).

  However, iron group elements such as cobalt remaining in the diamond sintered body have low strength such as hardness, and in particular, the strength is lowered due to high temperature during use, and also has the effect of graphitizing diamond. As a result, the performance of the cutting edge may be reduced. Therefore, in order to obtain higher strength of the sintered body, a sintered body in which diamond particles are bonded to each other through a binder made of a carbide of a periodic table 4, 5 or 6 element is disclosed in Japanese Patent Publication No. 58-32224. (Patent Document 2) and Japanese Patent Application Laid-Open No. 2003-95743 (Patent Document 3).

JP-A-2005-239472 (Patent Document 4) discloses a sintered body in which diamond particles are bonded to each other through a binding material composed of a carbide such as a periodic table 4, 5 or 6 element and cobalt and cobalt. In addition to suppressing abnormal grain growth in the sintering process, and strengthening the direct bonding between diamond particles, a diamond sintered body excellent in wear resistance, fracture resistance, impact resistance, etc. is obtained. Therefore, a diamond sintered body is disclosed in which the particle diameter and content of diamond particles, the content of cobalt in the binder, the presence form of carbides, and the like are specified.
Japanese Examined Patent Publication No. 39-20483 Japanese Patent Publication No. 58-32224 JP 2003-95743 A JP 2005-239472 A

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

  As a result of intensive studies, the present inventor has found that the binder contains a solid solution made of tungsten together with a specific element in the periodic table 4, 5 or 6 and carbon, and has a high hardness and is resistant to fracture. As a result, it was found that a diamond sintered body having further excellent strength such as property and wear resistance can be obtained.

The present invention is a diamond sintered body containing diamond particles and a binder,
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.
The diamond particles adjacent to each other are bonded to each other (claim 1).

  The content of the diamond particles with respect to the total weight of the diamond particles and the binder is preferably 60% by weight or more and less than 98% by weight. Since the binder has a hardness lower than that of diamond, by setting the content of diamond particles to 60% by weight or more, the hardness is prevented from being lowered, and the strength such as fracture resistance (bending strength) and impact resistance is increased. It will be excellent. On the other hand, when the diamond particle content is 98% by weight or more, the catalytic ability of the binder is not sufficiently obtained, the neck growth does not progress, and as a result, the fracture resistance (bending strength) tends to decrease. .

  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 adjacent diamond particles being bonded to each other, excellent fracture resistance (bending 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.

  Since the solid solution has a higher hardness than the iron group element, when the binder contains the solid solution, the hardness of the binder and further the hardness of the diamond sintered body is improved. In addition, since chemical reaction resistance such as heat resistance and oxidation resistance is increased, wear resistance is increased. Furthermore, since the affinity with the aluminum alloy material which is the main application of the diamond sintered body tool is lowered, the wear resistance and the welding resistance are increased. Moreover, since strength is increased by solid solution strengthening, fracture resistance (bending strength) and impact resistance are increased.

  The solid solution includes a carbide of the element Z. When the solid solution contains the carbide of element Z, strength such as fracture resistance and wear resistance is improved. Even if it is an element of Periodic Table 4, 5 or 6 or contains an element other than element Z, for example, molybdenum carbide, excellent fracture resistance and wear resistance cannot be obtained.

  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 hardness, fracture resistance, and wear resistance are further improved. From the prior art diamond sintered body containing only one of the carbide of element Z and the carbide of tungsten, Further excellent strength can be obtained.

  The element Z, tungsten and carbon contained in the binder form a solid solution. By forming a solid solution, even better fracture resistance and wear resistance can be obtained 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 content of the solid solution in the binder is preferably 0.5% by weight or more and less than 50% by weight, and more preferably 20% by weight or more and less than 50% by weight. On the other hand, the content of the iron group element in the binder is preferably 50% by weight or more and less than 99.5% by weight, and more preferably 50% by weight or more and less than 80% by weight. When the solid solution content is smaller than the above range, it is difficult to obtain excellent fracture resistance, wear resistance, etc., while when the solid solution content is larger than the above range, the neck growth of diamond particles is promoted. As a result, it becomes difficult to obtain sufficient catalytic ability, and as a result, problems such as a reduction in fracture resistance are likely to occur.

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

  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 2). When the component ratio of element Z to tungsten in the solid solution is in the range of 0.4 ≦ element Z / tungsten ≦ 15.0 in terms of atomic ratio, greater hardness and excellent wear resistance can be obtained. Among these ranges, the range of 0.4 ≦ element Z / tungsten ≦ 3.0 is particularly preferable, and even greater hardness and excellent wear resistance can be obtained.

  The diamond sintered body according to claim 1, wherein the iron group element is cobalt, and the content in the binder is 50 wt% or more and less than 80 wt%. 3). Examples of the iron group element include iron, nickel, and cobalt. Among them, cobalt is preferable because of its high catalytic ability.

  Further, when the content of cobalt in the binder is 50% by weight or more, the catalytic ability to promote neck growth of diamond particles is particularly large, and as a result, excellent fracture resistance and the like are obtained. On the other hand, when the content is less than 80% by weight, the content of the solid solution in the binder is high, and excellent chipping resistance, wear resistance, and the like are obtained.

  The diamond sintered body according to claim 4, wherein the diamond particles have an average particle diameter 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 Patent Document 4.

  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). When titanium is used among the elements Z, the hardness of the sintered body is particularly high, and particularly excellent fracture resistance and wear resistance are obtained.

  Next, the manufacturing method of the diamond sintered compact of this invention is described.

  The solid solution can be obtained by mixing carbide powder of element Z and powder of tungsten carbide separately from diamond particles, and then heating and pressurizing to 1300 ° C. and 3 GPa or more at which these solid solutions. The obtained solid solution is pulverized using a ball mill or the like.

  The diamond sintered body is obtained by, for example, dry-mixing the solid solution powder, the iron group element powder, and the diamond powder thus obtained, and then heating and pressurizing them in the mold of the ultrahigh pressure generator. It can be obtained by sintering. 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 easily neck-growth, a strong skeleton is formed, and the fracture resistance 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 formed in the sintering process, resulting in fracture resistance and wear resistance. A diamond sintered body having excellent properties 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 diamond sintered body obtained as described above is more excellent in strength such as wear resistance and fracture resistance than the conventional diamond sintered body, and is suitable for cutting blades of cutting tools. Used

  The diamond sintered body of the present invention is a sintered body having a higher hardness than the conventional diamond sintered body, and exhibits a high bending strength and a small flank wear amount. Since the high bending strength indicates that the fracture resistance as a tool is excellent, and the small flank wear amount indicates that the wear resistance is excellent, the diamond sintered body of the present invention has such as fracture resistance and wear resistance. It is a sintered body that is superior in strength to a conventional diamond sintered body, and is suitably used for cutting tools and the like.

  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.

  The diamond sintered bodies A to L of the binder component shown in Table 1 were manufactured, and the bending strength of the diamond sintered body and the cutting tool when the obtained diamond sintered body was used as a cutting blade of a cutting tool. The amount of wear on the flank was measured. Sintered bodies C to F and sintered bodies H to L are examples of the present invention, and sintered bodies A, B, and G are comparative examples.

(Manufacture of diamond sintered body)
85 parts by weight of diamond particles having an average particle diameter of 1 μm, 10 parts by weight of cobalt powder, and 5 parts by weight of binder components other than cobalt were dry mixed.

  As the binder component other than cobalt, tungsten carbide powder is used in the production of sintered body A, and the mixture used in the production of sintered body B is a mixture of tungsten carbide powder and titanium carbide powder.

  In the production of the sintered bodies C to L, the elements shown in the “binding material component” column of Table 1 are mixed at the atomic ratio shown in the “element ratio of solid solution” column of Table 1, and the pressure is 5.5 GPa, A solid solution prepared by pulverizing a solid solution held at a temperature of 1400 ° C. for 5 minutes was used as a binder component other than cobalt.

  In this way, the raw material obtained by dry-mixing the diamond particles and the binder is filled in a tantalum container in contact with a base material (disk) made of cemented carbide, and using a belt-type ultra-high pressure device, Sintering was performed by holding for 10 minutes under the conditions of pressure: 5.8 GPa and temperature: 1500 ° C. to obtain a diamond sintered body.

(Measurement of cobalt and carbide / solid solution content)
The cobalt and carbide / solid solution contained in each of the diamond sintered bodies obtained above are measured by XRD (X-ray diffraction), TEM (transmission electron microscope), AES (Auger electron spectroscopy), and cobalt. And carbide and solid solution were detected. Each element was quantitatively measured by a high frequency induction plasma emission analysis method (ICP method), and each content (% by weight with respect to the total amount of diamond particles and binder components) was calculated. The calculated values are shown in Table 1.

(Measurement of hardness of sintered body and binder)
Further, for each sintered body, the Martens hardness (ISO14577) of the sintered body and the binder part was measured 10 times using a nanoindenter at a test load of 10 gf. The average value is shown in Table 1.

(Measurement of bending strength and flank wear)
Each diamond sintered body was processed into a plate-shaped specimen having a length of 6 mm, a width of 3 mm, and a thickness of 0.3 mm, and the bending strength of each specimen was measured by a three-point bending test with a span distance of 4 mm. Furthermore, a sintered sintered body tip (blade exchangeable tip, ISO standard: TPGN160304) in which each diamond sintered body is attached to a corner of a base metal having a regular triangular main surface is manufactured and cut under the following conditions. A test was conducted to measure the flank wear amount of the diamond sintered body. These results are shown in Table 1.

[Conditions for cutting test]
Work material: Al alloy round bar containing Si-16 wt% Cutting conditions: peripheral turning, cutting speed 800 m / min, cutting 0.5 mm, feed 0.12 mm / rev, wet cutting, cutting time 5 minutes

  The results in Table 1 indicate that the bending strength of the diamond sintered body and the amount of flank wear when used as a cutting tool cutting edge vary greatly depending on the constituent elements of the binder.

  As is clear from the results in Table 1, sintered bodies C to F and H to L manufactured using a solid solution of element Z, tungsten, and carbon as binders have higher hardness than sintered bodies A and B, and High bending strength and low flank wear. The binder containing this solid solution has a high hardness of the binder component. As a result, the hardness of the entire sintered body is increased, and the wear resistance is considered to be improved. Furthermore, since this solid solution also has a function as a binder, it is considered that the bending strength is improved as compared with sintered bodies A and B containing tungsten carbide or the like that cannot obtain the function as a binder.

  Since a high bending strength indicates that the fracture resistance as a tool is excellent, and a small flank wear amount indicates that the wear resistance is excellent, the sintered bodies C to F and H to L which are examples of the present invention are cut. It became clear that it was suitable as a material for tools.

  Note that the sintered body G manufactured using the solid solution as the binder was substantially the same as the sintered body B in terms of hardness, bending strength, and wear resistance, despite the fact that tungsten was dissolved. That is, even if it is an element of periodic table 4, 5, and 6 group, the effect of this invention is not acquired in the case of molybdenum. This is presumably because the atomic weights of molybdenum and tungsten were close, and even when tungsten was dissolved in molybdenum carbide, the hardness was not greatly improved.

  In the sintered bodies C to F, the ratio of element Z: tungsten: carbon in the solid solution is the same, and only the type of element Z is different. As shown in the results of Table 1, the sintered body C using titanium as the element Z has particularly high hardness, high bending strength, low flank wear, It is particularly excellent as a material. Titanium is considered to have a larger function of promoting the bonding between diamond particles than other elements, and the sintered body C is particularly excellent in the bending strength that is greatly influenced by the bonding force between diamond particles.

  The sintered bodies C and H to L each contain a solid solution of titanium, tungsten, and carbon in the binder, but the element ratios of titanium and tungsten are different. Note that the number of carbon elements is the total number of elements of titanium and tungsten.

  Among the sintered bodies C and H to L, the sintered body C in which titanium and tungsten are dissolved at a ratio of 1: 1 shows the best performance, the hardness is large, and the bending strength is high. The flank wear is small. On the other hand, in the sintered body L in which titanium / tungsten is less than 0.4 and the sintered body J in which titanium / tungsten exceeds 15, there is a tendency for hardness, fracture resistance, and wear resistance to decrease.

  The diamond sintered bodies M to Q of the binder component shown in Table 2 are manufactured by changing the addition method of each element, and the bending strength of the diamond sintered body is obtained. The amount of wear on the flank face of the cutting tool when used as a cutting edge was measured. Sintered bodies O, P and Q are examples of the present invention, and sintered bodies M and N are comparative examples.

(Manufacture of diamond sintered body)
Specifically, the diamond sintered body was manufactured as follows. In Table 2, diamond particles having an average particle diameter of 1 μm, cobalt powder as a binder, and a compound having the composition shown in Table 2 are mixed in a proportion of 85% by weight of diamond particles, 10% by weight of cobalt powder, and 5% by weight of additives. Addition was performed by the addition method shown. For PVD coating, an RF (Radio Frequency) sputtering PVD apparatus was used, and 50% of the surface area of the diamond particles was controlled so as to be discontinuous. The raw material thus obtained was filled in a tantalum container in contact with a substrate (disk) formed of a cemented carbide, and using a belt-type ultrahigh pressure device, the pressure: 5.8 GPa, Sintering was performed for 10 minutes at a temperature of 1500 ° C. to obtain a diamond sintered body.

(Measurement of cobalt and carbide / solid solution content)
The contents of cobalt and carbide / solid solution contained in each diamond sintered body were examined by the same method as in Example 1, and the respective weight percentages were calculated and shown in Table 2.

(Measurement of bending strength and flank wear)
Furthermore, Table 2 shows the results of measuring the amount of wear on the flank of the cutting tool when used as a bending force and a cutting edge of a tool in the same manner as in Example 1.

  Sintered bodies N, O, P, and Q were obtained by adding titanium and tungsten, but differences were found in the bending strength and wear resistance of the binder and the diamond sintered body depending on the addition method.

  When the sintered bodies M and N are compared, when tungsten carbide is PVD-coated, even if Ti powder is mixed and sintered, a (Ti, W) C solid solution cannot be formed and exists as titanium carbide and tungsten carbide. There was almost no difference in performance.

However, in the sintered bodies O to Q in which the solid solution of titanium, titanium carbide, and (Ti, W) C is PVD-coated, the solid solution of (Ti, W) C exists in the diamond sintered body, so A significant improvement in wear was observed. Since a solid solution of (Ti, W) C is formed by PVD coating of a compound containing titanium, it is clear from this result that any form of titanium before coating may be used.

Claims (5)

A diamond sintered body containing diamond particles and a binder,
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 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 claim 1, wherein:   3. The diamond sintered body according to claim 1, wherein the iron group element is cobalt, and the content of the iron group element in the binder is 50 wt% or more and less than 80 wt%.   The diamond sintered body according to any one of claims 1 to 3, wherein an average particle diameter of the diamond particles is 2 µm or less. 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. .