JP2010208942A - High strength-high wear resistant diamond sintered body and method of producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diamond sintered body having excellent wear resistance, chipping resistance, impact resistance and heat conductivity and a method of producing the same. <P>SOLUTION: The high strength-high wear resistant diamond sintered body includes sintered diamond particles having ≤2 μm average particle diameter and a bonded phase of a remainder. The content of the sintered diamond particle in the diamond sintered body is ≥80 vol.% to ≤98 vol.%. The bonded phase contains at least one or more kinds of elements selected from titanium or the like the content of which is ≥0.5 mass% to <50 mass% in the bonded phase and cobalt the content of which is ≥50 mass% to <99.5 mass%. A part or all of the elements exist as carbide particles having ≤0.8 μm average particle diameter. The structure of the carbide particles is discontinuous and the adjacent diamond particles are bonded with each other. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a high-strength, high-abrasion resistant diamond sintered body and a method for producing the same, and more particularly, excellent in wear resistance, fracture resistance, impact resistance, and thermal conductivity, turning tools, milling tools and The present invention relates to a cutting tool typified by an end mill, a wear-resistant tool typified by a reinforcing tool for a drawing die, a sliding part or a clamp part of a machine tool, and an electronic material application such as an electrode part.

  Since diamond is the hardest material among the materials existing on the ground, diamond sintered bodies are used for cutting tools and wear-resistant tools. For example, Japanese Patent Publication No. 39-20483 (Patent Document 1) and Japanese Patent Publication No. 52-12126 (Patent Document 2) disclose diamond in which diamond particles are sintered with an iron group metal binder such as Co (cobalt). A sintered body is disclosed. Since this diamond sintered body is not easily damaged by cleavage, which is a defect of single crystal diamond, a material such as a cutting tool for cutting non-ferrous metal materials such as Al (aluminum) -Si (silicon) alloy. Is widely used.

  In such a diamond sintered body, those having an average particle diameter of 5 μm or more and 100 μm or less are excellent in wear resistance. In addition, diamond particles having an average particle diameter of less than 5 μm are excellent in chipping resistance. Similar to general ceramics sintered bodies, the diamond particles, which are the hard particles that make up the diamond sintered body, have a finer and more uniform particle size and are firmly bonded with a high content (high density). As the sintered body increases, the diamond sintered body tends to have better fracture resistance.

  As a method for firmly bonding diamond particles, the above-mentioned Patent Document 1 discloses that Co, Fe (iron), or Ni (which causes diamond powder to dissolve and re-precipitate to form a direct bond called neck growth between diamond powders. A method using a binder made of a solvent metal having catalytic ability typified by an iron group metal such as nickel) is disclosed. Japanese Examined Patent Publication No. 58-32224 (Patent Document 3) discloses a method of bonding diamond particles with each other through a binder made of a carbide of a periodic table 4a, 5a or 6a group metal. .

  The diamond sintered body manufactured by the method of generating neck growth between diamond particles using the former Co or WC (tungsten carbide) -Co alloy as a binder is the diamond sintered body manufactured by the latter method. On the other hand, a binder that is inferior in hardness and corrosion resistance to diamond particles will maintain a strong skeletal structure even after selective wear due to mechanical wear such as rubbing wear or chemical wear such as corrosion. can do. For this reason, the diamond sintered body manufactured by the latter method is excellent in fracture resistance and wear resistance.

  However, the binder itself made of the former Co or WC-Co alloy is inferior in hardness as compared with the ceramic type binder used in the latter method as well as the diamond particles. It has the weak point of being inferior to mechanical rubbing wear.

Thus, a diamond sintered body in which a Co alloy is used as a binder and an ultrafine diamond particle having an average particle diameter of 1 μm or less is firmly baked while maintaining a homogeneous structure, and is made of Co or a WC-Co alloy. If the content of diamond particles can be increased so that the content of the binder can be reduced as much as possible, an ideal diamond sintered body having extremely excellent fracture resistance and excellent wear resistance can be obtained.

  However, when sintering is performed using ultrafine diamond particles of 1 μm or less and an iron group metal such as Co or WC (tungsten carbide) -Co, the ultrafine diamond particles are very active, Abnormal grain growth of diamond grains tends to occur frequently unless the temperature and pressure conditions at the time of sintering are strictly controlled. Further, under high temperature conditions important for promotion of neck growth, when diamond particles of 2 μm or less are used as a starting material, abnormal grain growth is inevitable, and a sintered body having an abnormal grain growth portion is EDM (Electrical Discharge Machining) can no longer be cut. Moreover, the mechanical strength of diamond is also reduced by the generation of defects. Therefore, it is difficult to obtain a diamond sintered body having a grain size of 1 μm or less and having a homogeneous structure with high yield.

  Therefore, as a method for suppressing abnormal grain growth of diamond particles, hard particles such as WC, cBN (cubic boron nitride), SiC (silicon carbide) having hardness close to diamond are arranged at the grain boundaries of diamond particles. There is known a method for controlling abnormal grain growth by the above method. Such a technique is disclosed in, for example, Japanese Patent Publication No. 61-58432 (Patent Document 4), Japanese Patent Publication No. 6-6769 (Patent Document 5), and Japanese Patent Application Laid-Open No. 2003-95743 (Patent Document 6). ing.

Japanese Examined Patent Publication No. 39-20483 Japanese Examined Patent Publication No. 52-12126 Japanese Patent Publication No. 58-32224 Japanese Examined Patent Publication No. 61-58432 Japanese Patent Publication No. 6-6769 JP 2003-95743 A

  However, in the above method, hard particles having a low affinity with diamond particles are arranged between the diamond particles, or the entire surface of the diamond particles is coated with a binder that does not have a catalytic (dissolution reprecipitation) ability for the diamond particles. By doing so, the direct bonding between diamond particles is physically and chemically prevented, and abnormal grain growth of diamond particles is suppressed. For this reason, the skeleton formation by the neck growth between diamond particles becomes insufficient. As a result, the mechanical properties and thermal properties inherent to diamond deteriorate, and there is a problem that the fracture resistance, impact resistance, wear resistance, and thermal conductivity of the diamond sintered body are lowered.

  Accordingly, an object of the present invention is to provide a diamond sintered body excellent in fracture resistance, impact resistance, wear resistance and thermal conductivity, and a method for producing the same.

  As a result of intensive studies to improve the fracture resistance and wear resistance of the diamond sintered body, the present inventors have made the direct bonding between diamond particles stronger, It has been found that strength such as fracture resistance and impact resistance, wear resistance and thermal conductivity can be improved. Therefore, it is not a hard particle that has been conventionally used, but has a catalytic action (dissolution reprecipitation) on diamond particles in the same manner as a binding material made of Co or a WC-Co alloy, but excessive diamond particles in the binding material. We investigated a method to suppress abnormal grain growth by using a new binder that suppresses dissolution of slag.

As a result, when fine diamond particles with an extremely large surface area are used as the starting material, during sintering, diamond rapidly dissolves in large quantities in Co as a binder, and carbon in the binder that instantaneously reaches supersaturation, It was found that diamond was deposited as thermodynamically stable diamond and abnormal grain growth of diamond particles occurred. In order to prevent such abnormal grain growth, Ti (titanium), Zr (zirconia), Hf (hafnium), V (vanadium) having a content of 0.5% by mass or more and less than 50% by mass in Co as a binder. ), Nb (niobium), Ta (tantalum), Cr (chromium), Mo (molybdenum) part or all of at least one element selected from the group consisting of carbides having an average particle size of 0.8 μm or less And added so that the structure of the carbide particles becomes discontinuous. As a result, the fine carbide becomes a getter and further dissolves as a carbide in Co to some extent, so that the dissolution and precipitation of simple carbon in Co can be slow. Moreover, by controlling so that the said element does not continue, diamond particles become easy to neck-growth and a firm frame | skeleton is formed. Further, since the amount of the binder added is small and it is not necessary to add hard particles, the diamond content in the diamond sintered body increases.

  Further, in a sintered body using coarse diamond powder, the diamond particles are easily sintered by the element added to the binder. Therefore, the conventional addition of tungsten carbide becomes unnecessary, and the wear resistance of the diamond sintered body can be improved.

  In the diamond sintered body of the present invention, carbide particles are discontinuously present. That is, the carbides are not directly joined to each other and have a skeleton structure. As a result, the presence of the carbide is less likely to hinder the bonding between the diamond particles, so that the bonding between the diamond particles can be strengthened.

  Further, even in a fine-grained diamond sintered body containing 90% by volume or more of diamond having an average particle diameter of 2 μm or less that could not be obtained without abnormal grain growth by the conventional method, the inclusion of diamond particles in the diamond sintered body It was confirmed that the larger the amount, the better the wear resistance and fracture resistance of the sintered body.

  Moreover, it discovered that the magnitude | size of the defect in a sintered compact and intensity | strength, such as a fracture resistance of a sintered compact, impact resistance, had a close relationship. The defect referred to here is a diamond particle having a remarkably large diameter in a diamond sintered body, a pool of a binder such as a solvent metal, a void, or a bond (neck growth) between diamond particles (not bonded or not bonded). This refers to a region where bonding is incomplete. The smaller the defects in the diamond sintered body, the higher the strength of the sintered body.

  Based on these findings, the high strength and high wear resistance diamond sintered body of the present invention has high strength and high wear resistance provided with sintered diamond particles having an average particle size of 2 μm or less and the remaining binder phase. It is a diamond sintered body. The content of sintered diamond particles in the diamond sintered body is 80 volume% or more and 98 volume% or less. Bonded with at least one element selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, and molybdenum whose content in the binder phase is 0.5% by mass or more and less than 50% by mass The binder phase contains cobalt having a content of 50% by mass or more and less than 99.5% by mass in the phase. Part or all of at least one element selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, and molybdenum exists as carbide particles having an average particle size of 0.8 μm or less. The structure of the carbide particles is discontinuous, and adjacent diamond particles are bonded to each other.

In such a diamond sintered body, at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, and Mo is added to the binder. Therefore, even when the diameter of diamond particles used as a raw material is small, abnormal growth of the particles can be suppressed without adding hard particles. In addition, even when the diameter of diamond particles used as a raw material increases, by adding the above elements to the binder, high strength and high resistance with excellent fracture resistance, wear resistance, impact resistance and thermal conductivity are achieved. A wearable diamond sintered body can be obtained. In addition, since the amount of binder added is not greater than that of conventional materials and the content of diamond is not smaller than that of conventional materials, wear resistance and the like are not deteriorated.

  The reason for setting the average particle size of the sintered diamond particles to 2 μm or less, preferably 0.8 μm or less is to prevent the strength of the diamond sintered body from being lowered due to cleavage of the diamond particles.

  The reason why the content of the sintered diamond particles is 80% by volume or more and less than 98% by volume is as follows. This is because if the content of sintered diamond particles is less than 80% by volume, strength such as fracture resistance and impact resistance and wear resistance are reduced, and if the content of diamond particles is 98% by volume or more. This is because the effect of the binder cannot be sufficiently obtained and the neck growth does not progress.

  The reason why the content of at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, and Mo is 0.5 mass% or more and less than 50 mass% is as follows. . This is because if the content of the element is less than 0.5% by weight, the effect of adding the element to suppress abnormal grain growth of the diamond particles becomes small. In addition, if the content of the element exceeds 50% by weight, the effect of the binder having a catalytic ability to promote neck growth of diamond particles cannot be sufficiently obtained.

  In the present invention, using Ti metal as a starting material is most effective in improving both the bonding strength between diamond particles and suppressing the abnormal grain growth.

  Originally, Ti is not considered to have a catalytic action for promoting neck growth between diamond particles. However, in the present invention, when an appropriate amount of Ti is added to the Co binder having neck growth catalytic ability, Ti does not inhibit the catalytic action of Co, and Ti is dissolved when carbon dissolves in the binder. Estimated to be an excess carbon getter. In addition, it is presumed that Ti can react with diamond particles to become carbides, thereby improving the bonding force between the diamond particles and suppressing abnormal grain growth.

  Here, W (tungsten) also showed the effect of suppressing some abnormal grain growth, similar to Ti, but when the diamond particle diameter was 1 μm or less, the effect of abnormal grain growth was hardly seen. Moreover, when W is added instead of Ti, W exists as WC in the diamond sintered body. Therefore, when Al (aluminum) metal is cut, Al is selectively added to the WC of the diamond sintered body. A defect was also found that it was easier to weld.

  As a specific method for producing the diamond sintered body of the present invention, at least one element selected from the group consisting of ultrafine Ti, Zr, Hf, V, Nb, Ta, Cr, and Mo, or the above element There is a method in which ceramic powder made of the above carbide is pulverized using a ball mill or the like and mixed with fine diamond powder. At that time, in order to use the metal powder to make the carbide in the sintered body into a fine and discontinuous structure, it is necessary to use ultrafine particles as a starting material. Since ordinary metal materials have ductility, only fine particles having a particle size of several tens of μm can be obtained. For this reason, a pool of binding materials is likely to be formed after sintering, and this portion becomes a defect. Therefore, in order to obtain the sintered body of the present invention, it is preferable to use metal particles made of Ti or the like obtained by using an atomizing method capable of obtaining ultrafine metal particles having a particle diameter of several μm or less. Co alloys and the like are also preferably fine particles, and it is also preferable to use nanometer-order ultrafine metal powders obtained using a titanium redox method that combines titanium ion reduction and oxidation reactions.

  The sintered body of the present invention can be obtained by using ultrafine ceramic powder made of carbide of at least one element selected from the group consisting of ultrafine Ti, Zr, Hf, V, Nb, Ta, Cr, and Mo. Although a metal powder is used rather than a ceramic powder, a stronger diamond bond can be obtained by reactive sintering with diamond particles. That is, it is preferable to use chemically active metal particles as the starting material instead of the thermally and chemically stable ceramic particles as the starting material. This is because, when metal powder is used, carbides are generated while reacting with diamond particles characterized by low sinterability, and a strong bond can be formed between the diamond particles.

Ceramics composed of at least one element selected from the group consisting of ultrafine Ti, Zr, Hf, V, Nb, Ta, Cr, and Mo or carbides thereof are arranged uniformly and discontinuously in the diamond sintered body. As an ideal method, there is a method in which the surface of the diamond particle powder is coated with the binding material by a PVD (Physical Vapor Deposition) method or the like. In particular, when a sputtering method is used, the binder is discontinuously coated on the diamond particles with a superfine metal of about 10 to 100 nm, particularly about 10 to 200 nm, which is representative of Ti. It can be set as the diamond sintered compact excellent in.

  In the high-strength and high wear-resistant diamond sintered body of the present invention, at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, and Mo is Ti. The content of Ti in the phase is preferably 0.5% by mass or more and less than 20% by mass.

  In the high-strength and high wear-resistant diamond sintered body of the present invention, a test piece cut out from the diamond sintered body into a rectangular planar shape having a length of 6 mm, a width of 3 mm, and a thickness of 0.35 mm to 0.45 mm. It is preferable that the bending strength measured under the condition of a span of 4 mm using is 2.65 GPa or more.

  In the high-strength and high wear-resistant diamond sintered body of the present invention, the diamond sintered body was cut into a rectangular planar shape having a length of 6 mm, a width of 3 mm, and a thickness of 0.4 to 0.45 mm. The test piece was 120 ° C. or more and 150 ° C. with 40 ml of nitric acid having a concentration of 60% or more and less than 65% diluted twice and 10 ml of hydrofluoric acid having a concentration of 45 to 50% mixed in a sealed container. After performing the dissolution treatment for less than 3 hours, the bending strength measured using this test piece under the condition of 4 mm span is preferably 1.86 GPa or more.

  In the high strength and high wear resistant diamond sintered body of the present invention, at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, and Mo is Ti, and The Ti content in the binder phase is 1% by mass or more and less than 20% by mass, under the conditions of an electron beam acceleration speed of 40 kV, current of 25 mA, diffraction angle 2θ = 20 to 80 °, and scanning speed of 0.1 ° C./second. In the X-ray diffraction pattern of the measured diamond sintered body, it is preferable that the (200) diffraction line of titanium carbide has an intensity ratio of 3% or more and less than 50% of the (111) diffraction line of diamond. Here, “intensity of X-ray diffraction line” refers to the height of a peak in an X-ray diffraction pattern using CuKα ray (characteristic X-ray generated by Cu K shell).

  In addition, the present inventors pay attention to oxygen and oxide adsorbed on the surface of diamond powder as a raw material for producing a diamond sintered body, and by removing these, defects existing in the sintered body are reduced. The inventors have found that the strength of the diamond sintered body is improved. Therefore, the proportion of oxygen in the diamond sintered body is preferably 0.001% by mass or more and less than 0.15% by mass. The oxygen ratio of 0.001 mass% or more and less than 0.15 mass% is impossible with the current technology, and if it is 0.15 mass% or more, diamond This is because the strength of the sintered body is the same as the conventional one.

  In addition, since the diamond sintered body of the present invention can suppress abnormal grain growth, it can be sintered under high pressure and temperature conditions. Conventionally, industrially, the pressure is generally 5.5 GPa and the temperature is around 1000 ° C., which is a necessary and sufficient pressure. However, finer diamond particles can be sintered at a higher content by increasing the sintering conditions. Further, neck sintering can be promoted by sintering at higher pressure.

  In the method for producing a high-strength, high-abrasion resistant diamond sintered body of the present invention, sintering is performed by holding for 10 minutes under conditions of a pressure of 5.7 GPa to 7.5 GPa and a temperature of 1500 ° C. to 1900 ° C. Is desirable. When the pressure exceeds 7.5 GPa, it becomes impractical due to the durability of the mold of the ultrahigh pressure generator. When the temperature is higher than 1900 ° C., the diamond-graphite is 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 ultra-high pressure generator and the performance of the diamond sintered body, it is baked by holding for 10 minutes under conditions of a pressure of 6.0 GPa to 7.2 GPa and a temperature of 1500 ° C. to 1900 ° C. It is more preferable to tie.

  According to the high-strength and high-abrasion resistant diamond sintered body of the present invention and the manufacturing method thereof, since it is possible to suppress grain growth without using hard particles having a low affinity with diamond particles, the diamond particles directly Bonding can be made stronger. As a result, a high-strength and high-abrasion resistant diamond sintered body excellent in wear resistance, fracture resistance, impact resistance and thermal conductivity can be obtained.

2 is a photomicrograph showing the structure of Sample 1E of Example 1. It is a microscope picture which shows the structure | tissue of the sample 1E at the time of raising magnification from FIG. 2 is a photomicrograph showing the structure of Sample 1H of Example 1. It is a microscope picture which shows the structure | tissue of the sample 1H at the time of raising magnification from FIG. It is a microscope picture which shows the structure | tissue of the diamond sintered compact which grew abnormally.

  Embodiments of the present invention will be described in the following examples.

In this example, the average particle diameter of the sintered diamond powder, the content of the sintered diamond particles in the diamond sintered body, and the composition of the binder were changed, respectively. Was measured. Specifically, the powder average particle size is 0.8 μm under the conditions of a vacuum degree of 0.1 Pa, an in-furnace temperature of 300 ° C., and a rotation speed of 2000 rpm using a special vacuum furnace apparatus containing a rotary mixing device. Dry mixing of the diamond powder and a mixed powder of Co metal and Ti metal as a binder was performed. The mixed diamond powder and various binders are filled in a Ta (tantalum) container in contact with a disk made of WC-6% Co cemented carbide, and pressure is applied using a belt type ultrahigh pressure device. Sintering was performed by holding for 10 minutes under conditions of 7 GPa to 7.2 GPa and a temperature of 1500 ° C. to 1900 ° C. About the sample which added Ti, the structure | tissue observation of the surface of the completed sintered compact was performed, and it was judged whether the presence form of Ti was continuous or discontinuous. Only the number of diamond grains that grew to a particle size of 300 μm or more during sintering was measured as abnormal grain growth, and the quantity was measured. Further, all the sintered bodies were processed into 6 × 3 × 0.3 mm rod-shaped test pieces, and then the bending strength was measured by a three-point bending test with a span distance of 4 mm. In addition, a sintered chip for cutting whose main surface shape is an equilateral triangle (ISO standard: TPGN1603)
04) was prepared and a cutting test was performed to measure the amount of flank wear. In the cutting test, an Al (aluminum) alloy round bar containing 16% by mass of Si was used as a work material, a cutting speed of 800 m / min, a cutting depth of 0.5 mm, a feed speed of 0.12 mm / rev using a cutting fluid. The cutting conditions were 5 min. The results are shown in Table 1. In Table 1, the diamond sintered bodies of the present invention are Samples 1E and 1G. In addition, when X-ray analysis was performed about sample 1E and 1G, it turned out that some of added Ti exists as TiC.

As shown in Table 1, in the samples 1A and 1D in which the charge composition of the binder is 100 mass% Co and the average particle diameter of the diamond powder is 0.8 μm, 258 particles exhibiting abnormal grain growth each. Many occurred with 231. In addition, IC, 1F, and 1H, in which W was added to the binding material, exhibited slight, but unusual, grain growth of 11, 8, and 3, respectively. However, in the samples 1B, 1E, 1G, 1I, and 1N in which the binder phase contains Ti of 0.5% by mass or more and the average particle diameter of the diamond particles is 0.8 μm, almost no abnormal grain growth was observed. From this, it is understood that abnormal grain growth can be suppressed by containing Ti having a content of 0.5% by mass or more in the binder phase.

  Further, comparing the sample 1E in which the average particle diameter of the diamond powder is 0.8 μm and the sample 1L in which the average particle diameter of the diamond powder is 2.5 μm, the bending strength of the sample 1E is that of the sample 1L. Greater than power. From this, it can be seen that the fracture resistance is improved by setting the average particle diameter of the diamond particles to 2 μm or less.

  In addition, samples 1B and 1C having a sintered diamond particle content of 78% by volume are compared with samples 1E and 1F having a sintered diamond particle content of 90% by volume. The bending force is larger than the bending strength of samples 1B and 1C, and the flank wear amount of samples 1E and 1F is smaller than the flank wear amount of samples 1B and 1C. From this, it can be seen that the chipping resistance and wear resistance are improved by setting the content of sintered diamond particles to 80% volume or more.

  Further, 16.1% by mass of Ti is contained in the binder phase, sample 1E sintered under conditions of pressure 7.2 GPa and temperature 1900 ° C., and 25.6% by mass of W in the binder phase. Compared with sample 1F sintered under the conditions of pressure 6.8 GPa and temperature 1800 ° C., the bending strength of sample 1E is larger than that of sample 1F, and the flank wear amount of sample 1E Is less than the flank wear amount of the sample 1F. In addition, 46.2% by mass of Ti is contained in the binder phase, sample 1G sintered under conditions of a pressure of 7.0 GPa and a temperature of 1900 ° C., and 40.8% by mass of W in the binder. This is the same even when compared with the sample 1H sintered under the conditions of a pressure of 6.7 GPa and a temperature of 1750 ° C. Since Ti is contained in the binder phase, abnormal grain growth can be suppressed, so that sintering conditions such as pressure and temperature can be set high. Therefore, it can be seen that the chipping resistance and wear resistance can be improved.

  In addition, the samples 1E and 1G of the present invention have higher bending strength and smaller flank wear than the conventional sample 1M. Further, it can be seen that Sample 1K having an average particle diameter of 2 μm or more does not cause abnormal grain growth even when Ti is not added. Furthermore, in the sample 1N having a diamond particle content of 99% by mass, it can be seen that the neck growth due to the binder is insufficient because the bending strength is low and the flank wear amount is large.

  In this example, the bending strength and the flank wear amount were measured by changing the average particle diameter of Ti contained in the binder. Specifically, a diamond powder having an average particle diameter of 0.8 μm and a content of 90% by volume was mixed with a binder containing 75% by mass of Co and 25% by mass of Ti using a ball mill. Ti having an average particle size of 0.1 μm, 0.8 μm, 0.9 μm, and 1.0 μm was used as Ti in the binder. Then, it sintered by hold | maintaining for 10 minutes on the conditions of a pressure of 7.2 GPa, and temperature of 1900 degreeC using the belt-type ultrahigh pressure apparatus. With respect to the obtained sintered body, the bending strength was measured in the same manner as in Example 1, and the flank wear amount was measured by performing a cutting test. The results are shown in Table 2.

As shown in Table 2, the flank wear amount of the samples 2A to 2D is substantially the same, and the flank wear amount of the samples 2E to 2H is substantially the same. However, the bending strength of samples 2A and 2B is the same as that of samples 2C and 2B.
The bending strength of Samples 2E and 2F is larger than the bending strength of Samples 2G and 2H. In addition, the number of diamond particles whose particle size grew to 300 μm or more during sintering was measured. As a result, no abnormal grain growth was observed in Samples 2A, 2B, 2E, and 2F. On the other hand, Samples 2C, 2D, 2G, and 2H showed 3, 25, 4, and 25 abnormal grain growth, respectively. From this, it can be seen that when the average particle diameter of Ti in the binder is 0.8 μm or less, there is an effect of suppressing abnormal grain growth, and further, the neck growth is not suppressed, so that the fracture resistance is improved.

In this example, the bending force and flank wear were measured by changing the method of adding Ti added to the binder. Specifically, a sample obtained by mixing a diamond powder having an average particle size of 0.8 μm and a content of 90% by volume with a binder containing 75% by mass of Co and 25% by mass of Ti by a ball mill is used as a sample. Prepared as 3A. Further, a sample 3B having a similar composition and using a RF (Radio Frequency) sputtering PVD apparatus and coating diamond powder with Ti was prepared. Further, a sample 3C prepared by coating a diamond powder with Ti using a CVD (Chemical Vapor Deposition) apparatus so that the thickness of the coating layer is 0.1 μm on the entire surface of the diamond particle having the same structure is prepared. did. Each of the samples 3A to 3C is filled in a Ta (tantalum) container in contact with a WC-6% Co cemented carbide disk, and a pressure of 7.2 GPa is applied using a belt-type ultrahigh pressure device. Sintering was performed by holding at 1900 ° C. for 10 minutes. With respect to the obtained sintered body, the bending strength was measured in the same manner as in Example 1, and the flank wear amount was measured by performing a cutting test. The results are shown in Table 3.

As shown in Table 3, the sample 3A in which Ti was added by mixing using a ball mill and the sample 3B in which Ti was coated by the CVD method were more resistant to bending force and flank than in the sample 3B coated with the RF sputtering PVD apparatus. The wear amount showed good performance. When the surface of each sample was observed with a metal microscope, the sample 3A showed segregation of Co and Ti, and a uniform structure was not obtained. Moreover, the average grain system of Ti carbide was 1.0 μm, which was larger than that at the time of addition. In Samples 3B and 3C, no segregation of Co or Ti was observed, and a uniform structure was obtained. However, since the sample 3C uniformly covered the entire surface of the diamond particles, the TiC structure was continuous, and not only abnormal grain growth but also neck growth between the diamond particles was suppressed. The sample 3B was discontinuous because the Ti coating on the diamond particles was not uniform throughout but was discontinuous, and the average particle size of the Ti powder was maintained at about 0.1 μm. From this, it was found that the addition method of Ti is preferably coating with an RF sputtering PVD apparatus. Further, it has been found that if the average particle size of the carbide is larger than 0.8 μm or the structure of the carbide itself is continuous, the bending strength is reduced and the flank wear amount is increased.

  In the present Example, the change of each bending strength when the samples 3A to 3C of Example 3 were dissolved was examined. Specifically, a test piece cut into a rectangular planar shape having a length of 6 mm, a width of 3 mm, and a thickness of 0.4 to 0.45 mm from the diamond sintered bodies of Samples 3A to 3C of Example 3 was sealed in a sealed container. Among them, 40 ml of nitric acid having a concentration of 60% or more and less than 65% diluted twice and hydrofluoric acid mixed with 10 ml of hydrofluoric acid having a concentration of 45 to 50% were dissolved at 120 ° C. or more and less than 150 ° C. for 3 hours. Processed. Of the test pieces (samples) thus obtained, sample 4A was sample 4A, sample 3B was sample 4B, and sample 3C was sample 4C. Using each sample, the bending strength was measured under the condition of 4 mm span. The results are shown in Table 4.

As shown in Table 4, the bending strength of Sample 4B in which the addition method of Ti was an RF sputtering PVD apparatus was a decrease of only 0.22 GPa from 2.88 GPa to 2.59 GPa. On the other hand, the bending strength of sample 4A, in which the addition method of Ti was mixing by a ball mill, was greatly reduced by 0.57 GPa from 2.59 GPa to 2.02 GPa. Further, the bending strength of the sample 4C in which the addition method of Ti is CVD was greatly reduced by 0.48 GPa from 2.46 GPa to 1.98 GPa. From this, it can be said that the addition method of Ti is an RF sputtering PVD apparatus, that is, the structure of Ti itself is discontinuous, so that neck growth between diamond particles progresses and a strong skeleton is formed. I understand.

  In this example, the ratio of Ti in the binder was changed, and the intensity ratio between the (200) diffraction line of TiC and the (111) diffraction line of diamond in the obtained sintered body was measured. Specifically, the diamond powder content is 78% by volume, the sintered material contains 75% by mass of Co and 25% by mass of Ti, the sample 5A, the diamond powder content is 90% by volume, Sample 5B in which the binder contains 75% by mass of Co and 25% by mass of Ti, the diamond powder content is 90% by volume, the sintered material is 50% by mass of Co, and 50% by mass of Ti. Three types of samples were prepared, including the included sample 5C. The average particle diameter of the diamond powder was 0.8 μm in all samples. Then, it sintered by hold | maintaining for 10 minutes on the conditions of a pressure of 7.2 GPa, and temperature of 1900 degreeC using the belt-type superhigh pressure apparatus. About the obtained sintered body, using characteristic X-rays generated by the K shell of Cu, the acceleration speed of the electron beam irradiated to the Cu target is 40 kV, the current is 25 mA, the diffraction angle is 2θ = 20 to 80 °, and the scanning speed is 0.1 ° C. The X-ray diffraction pattern of the diamond sintered body was measured under the conditions of / sec, and the intensity ratio between the (200) diffraction line of TiC and the (111) diffraction line of diamond was measured. The results are shown in Table 5. In Table 5, the diamond sintered body of the present invention is Sample 5B.

  As shown in Table 5, the X-ray diffraction intensity ratio of Sample 5B with the smallest flank wear amount was 40%, but Samples 5A and 5C had a value exceeding 50%. Thereby, it turns out that there exists a tendency for the amount of flank wear to increase about the thing whose intensity ratio of TiC exceeds 50%. Further, since the sintered body containing no Ti in the composition of the binder causes abnormal grain growth, the intensity ratio of the (200) diffraction line of TiC is not less than 0.01% of the (111) diffraction line of diamond. It can be seen that the intensity ratio is preferably less than%.

  In this example, the bending strength and the flank wear amount were measured by changing the amount of oxygen contained in the diamond sintered body. Specifically, diamond powder having an average particle diameter of 0.8 μm and a content of 90% by volume was mixed with a binder containing 75% by mass of Co and 25% by mass of Ti. Next, heat treatment was performed in vacuum at temperatures of 1000 ° C., 1100 ° C., and 1250 ° C. for 60 minutes to reduce the binder and partially graphitize from the surface of the diamond particles. Then, it sintered by hold | maintaining for 10 minutes on the conditions of a pressure of 7.2 GPa, and temperature of 1900 degreeC using the belt-type superhigh pressure apparatus. Among the obtained samples, a sample heat-treated at a temperature of 1000 ° C. was sample 6A, a sample heat-treated at a temperature of 1100 ° C. was sample 6B, and a sample heat-treated at a temperature of 1250 ° C. was sample 6C. The amount of oxygen contained in these samples 6A to 6C was measured by ICP (Inductively Coupled Plasma) analysis. Further, the bending strength of the samples 6A to 6C was measured in the same manner as in Example 1. The results are shown in Table 6.

  As shown in Table 6, the amount of oxygen contained in the diamond sintered body is changed by changing the heat treatment temperature before sintering, and when the amount of oxygen becomes 0.15% by mass or less, the bending strength is greatly increased. It has improved. From this, it is understood that the defect resistance is improved by containing less than 0.15% by mass of oxygen.

  In this example, the diamond sintered bodies of Sample 1E (present invention) and Sample 1H (conventional example) of Example 1 were acid-treated and micrographs were taken. FIG. 1 is a photomicrograph showing the structure of Sample 1E of Example 1. FIG. 2 is a photomicrograph showing the structure of the sample 1E when the magnification is increased as compared with FIG. FIG. 3 is a photomicrograph showing the structure of the sample 1H of Example 1. FIG. 4 is a photomicrograph showing the structure of the sample 1H when the magnification is higher than that in FIG.

  With reference to FIGS. 1 to 4, a plurality of small holes scattered throughout correspond to a portion where the binder phase was present. The volume of the binder phase in FIGS. 1 and 2 showing the diamond sintered body of the present invention is smaller than the volume of the binder phase in FIGS. 3 and 4 showing the conventional diamond sintered pair. This shows that the neck growth of diamond particles is not inhibited by the binder phase in the present invention.

  FIG. 5 is a photomicrograph showing the structure of the diamond sintered body in which abnormal grains have grown. Referring to FIG. 5, the small dot portions are diamond particles that have grown abnormally. The diameter of the diamond particles that have grown abnormally in this way is 300 μm or more. Many conventional abnormal grain growths have been observed in conventional diamond sintered bodies. This abnormal grain growth can be suppressed in the present invention.

  The embodiments disclosed above are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the examples above, and is intended to include any modifications and variations within the scope and meaning equivalent to the terms of the claims.

Claims (8)

A high-strength, high-abrasion-resistant diamond sintered body comprising sintered diamond particles having an average particle size of 2 μm or less and the remaining binder phase,
The content of the sintered diamond particles in the diamond sintered body is 80 vol% or more and 98 vol% or less,
At least one element selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, and molybdenum having a content of 0.5% by mass or more and less than 50% by mass in the binder phase; The binder phase contains cobalt having a content of 50% by mass or more and less than 99.5% by mass in the binder phase,
A part or all of at least one element selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, and molybdenum exists as carbide particles having an average particle size of 0.8 μm or less;
The structure of the carbide particles is discontinuous,
A diamond sintered body having high strength and high wear resistance, wherein the adjacent diamond particles are bonded to each other.   The at least one element selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, and molybdenum is titanium, and the content of the titanium in the binder phase is 0.5% by mass. The high-strength and high-abrasion resistant diamond sintered body according to claim 1, wherein the sintered body is less than 20% by mass.   The bending strength measured under the condition of 4 mm span using a test piece cut out from the diamond sintered body into a rectangular planar shape having a length of 6 mm, a width of 3 mm, and a thickness of 0.4 mm to 0.45 mm is 2. The high-strength / high-abrasion resistant diamond sintered body according to claim 1, wherein the sintered body has a high strength and a high wear resistance. A test piece cut out from the diamond sintered body into a rectangular planar shape having a length of 6 mm, a width of 3 mm, and a thickness of 0.4 to 0.45 mm is contained in a sealed container with a concentration of 60% or more and less than 65% nitric acid. After performing a dissolution treatment for 3 hours at 120 ° C. or more and less than 150 ° C. with hydrofluoric acid mixed with 40 ml of a 2-fold diluted solution and 10 ml of hydrofluoric acid having a concentration of 45 to 50%, this test piece was used. The high strength and high wear resistance diamond sintered body according to any one of claims 1 to 3, wherein a bending strength measured under a condition of 4 mm span is 1.86 GPa or more.   The at least one element selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, and molybdenum is titanium, and the content of the titanium in the binder phase is 0.5 mass. X-ray diffraction of the diamond sintered compact measured under the conditions of an electron beam acceleration speed of 40 kV, a current of 25 mA, a diffraction angle of 2θ = 20 to 80 °, and a scanning speed of 0.1 ° C./second. 5. The high strength according to claim 1, wherein the (200) diffraction line of titanium carbide is an intensity ratio of 3% or more and less than 50% of the (111) diffraction line of diamond.・ High wear resistant diamond sintered body.   The high-strength and high wear-resistant diamond sintered body according to any one of claims 1 to 5, wherein the diamond sintered body contains 0.001 mass% or more and less than 0.15 mass% oxygen. . It is a manufacturing method of the high intensity | strength and the high abrasion-resistant diamond sintered compact of Claim 1-6, Comprising: A pressure is 5.7 GPa or more and 7.5 GPa or less using a belt-type superhigh pressure apparatus, Temperature is 1400 degreeC or more and 1900 degreeC. A method for producing a high-strength, high-abrasion resistant diamond sintered body characterized by sintering under the following conditions.   The high strength and high wear resistance according to claim 7, characterized in that sintering is performed under conditions of a pressure of 6.0 GPa to 7.2 GPa and a temperature of 1400 ° C to 1900 ° C using a belt type ultra high pressure apparatus. A method for producing a diamond sintered body.