JPH0563539B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a diamond cubic boron nitride (hereinafter referred to as CBN) sintered body that has high strength and heat resistance and is suitable for use as a cutting tool or rock excavation tool, and a manufacturing method. Conventional technology and its problems Currently, sintered bodies with a diamond content of 70% by volume or more and diamond particles bonded to each other are sold, and are used for cutting nonferrous metals, plastics, and ceramics, dressers, drill bits, and wire drawing dies. ing. In particular, when these diamond sintered bodies are used as dies for cutting non-ferrous metals or drawing relatively soft wire materials such as copper wire, their performance is extremely excellent. However, at present, there is no diamond sintered body that has satisfactory performance when used in drill bits and the like. The present inventors have discovered that the reason why commercially available diamond sintered bodies do not exhibit sufficient performance when used as drill bits for drilling hard rocks such as andesite and granite is that iron group metals such as _C0 are used as binding materials. I found out that there is. That is,
When excavating hard rocks, the drilling force becomes high and sintered diamond becomes hot. (1) The presence of iron group metal binders such as C ₀ promotes graphitization of diamond and reduces the bonding strength between particles. (2) Difference between the coefficient of thermal expansion of an iron group metal binder such as C ₀ (for example, the coefficient of linear expansion of C ₀ is 18 × 10 ^-6 ) and that of diamond (the coefficient of linear expansion is 4.5 × 10 ^-6 ) It was found that because of the large amount of carbon dioxide, cracks occur due to the difference in linear expansion when used at high temperatures, reducing the bonding strength between particles. A method for improving the heat resistance of a diamond sintered body is to remove iron group metals such as C ₀ that promote graphitization of diamond at high temperatures, as described in JP-A-53-114589. However, C ₀ from diamond sintered body
When iron group metals such as iron group metals are eluted, the strength of the diamond sintered body decreases by 20 to 30%. In particular, when a diamond sintered body is used as a bit, strength, wear resistance, and heat resistance are required. Due to the lack of strength of the body, the cutting edge will break and the life will be short. Another method to improve the above drawbacks (1) and (2) is to use CBN as a binder instead of an iron group metal binder such as C ₀ . CBN has a small difference in thermal expansion from diamond, and has good thermal conductivity and thermal stability. However, a sintered body made only of diamond powder and CBN powder is weakly sintered between diamond and CBN. When used as a tool, particles tend to fall off and wear resistance decreases. For this reason, sintered bodies containing diamond and CBN, which have been developed as cutting tool materials, contain an iron group metal phase such as C ₀ and are bonded via this phase. The present inventors conducted intensive research to develop a diamond CBN composite sintered body with high strength and excellent wear resistance and heat resistance by examining the types of binders. DISCLOSURE OF THE INVENTION As a result of research, it was found that 30 to 80 diamond particles whose individual particle surfaces were strongly sintered and coated with one or more of titanium carbides, borides, nitrides, and/or solid solutions thereof and aluminum nitride were found. % by volume, the titanium compound is 0.2 to 5.0% by volume, aluminum nitride is 1.0 to 5.0% by volume, and the balance is
Diamond CBN composite sintered body, which is CBN,
It was found to have toughness, wear resistance and heat resistance. That is, since the sintered body of the present invention does not use an iron group metal binder such as _C0 , graphitization of the diamond particles can be suppressed, and the diamond particles and CBN are made of titanium carbide, titanium carbide, It has good wear resistance because it is extremely strongly bonded via one or more of nitrides and borides and/or a solid solution thereof and aluminum nitride.
Since the CBN phase of the sintered body of the present invention is obtained by converting hexagonal boron nitride (hereinafter abbreviated as hBN) during high-temperature, high-pressure sintering, it is different from conventional sintered bodies using CBN powder as a starting material. Compared to , the bonding strength between CBNs is significantly higher. In addition, the difference in thermal expansion between the titanium compounds and aluminum nitride and diamond or CBN is approximately 1/2 that between iron group metals such as _C0 and diamond or CBN, so when used as a tool, the thermal expansion difference is There has also been an improvement in cracking caused by stress. The sintered body of the present invention has the best toughness and wear resistance, especially when diamond particles with a particle size of 10 to 100 μm are used. The diamond used may be either a synthetic diamond or a heavenly diamond. The diamond content is preferably 30-80%. When this content is less than 30%, wear resistance decreases, and when it exceeds 80%, toughness decreases. The diamond particles are uniformly mixed with titanium and aluminum oxides and hBN powder using a ball mill or the like. Here, the titanium and aluminum oxides to be mixed are 0.2 to 5.0% by volume and 1 to 1% by volume, respectively.
Preferably it is 10% by volume. If the titanium volume is less than 0.2%, the diamond-CBN interface will not be completely bonded through the titanium compound, and if it exceeds 5.0 volume%,
Unreacted titanium remains and reduces bonding strength. Additionally, if the aluminum oxide capacity is less than 1%, as will be explained later, the amount of aluminum nitride produced during pretreatment will decrease, resulting in
hBN→CBN conversion is not performed sufficiently and unreacted
hBN remains and the strength of the sintered body decreases. If it exceeds 10% by volume, unreacted aluminum oxide remains in the pretreatment, which reduces the bonding strength between diamond and CBN during sintering, which is not preferable. In addition, the hBN powder used here usually has an average particle size of 1 to 10 μm, and has been purified in advance so that its impurity oxygen content is 0.3% by weight or less, preferably 0.08% by weight or less. That's what I did. For example, the removal of oxygen impurities was
This can be easily achieved by the method shown in No. 58-60603.
This high purity of hBN makes hBN→CBN conversion extremely efficient. The above mixture is heated to 1550°C or higher, preferably 1600°C or higher at normal pressure in a nitrogen-containing atmosphere.
By heat treatment at a temperature of 1800°C to 1800°C, the surface of the diamond particles is graphitized, and at the same time, aluminum oxide is reduced to produce aluminum nitride. Through this treatment, as shown in the reaction formula below, a portion of the diamond is dissipated as carbon monoxide, but 0.5 to 10% by volume remains as graphite on the surface of the diamond particles. Al ₂ O ₃ +3C+N ₂ →2AlN+3CO When the treatment temperature is less than 1600°C, the reduction reaction of aluminum oxide is slow. In addition, if the temperature exceeds 1800℃, the graphitization of diamond particles is significantly accelerated, unreacted graphite remains in the sintered body, and at the same time AlN exceeds the decomposition reaction, so hBN is not sufficiently converted to CBN. This is not preferable because it significantly reduces the strength of the sintered body. The pretreated mixture consists of titanium, aluminum nitride, hBN, and surface graphitized diamond. The raw material for the sintered body is filled into a metal reaction container, such as a container made of molybdenum, tungsten, etc., which does not easily cause chemical reactions with these raw materials under sintering conditions, and the container is placed in a high-temperature, high-pressure generation chamber, and heated. Mechanically, CBN and diamond are simultaneously stable, and
Exposure for several minutes to the temperature and pressure conditions under which aluminum nitride exhibits the catalytic effect of converting hBN to CBN. During this time, hBN→CBN changes due to the action of aluminum nitride.
Conversion reaction proceeds. Along with this, titanium was precipitated with graphitized diamond and, at the same time, with aluminum nitride, as well as with hBN.
It reacts with CBN, and finally forms 0.2 to 5.0% by volume of titanium carbides, borides, nitrides, and/or solid solutions thereof at the diamond-CBN interface. A part of the aluminum nitride, which is the hBN→CBN conversion catalyst, reacts with titanium to form a titanium compound, but 1.0 to 5.0% by volume remains. If the residual amount of aluminum nitride is less than 1% by volume, titanium compounds will be excessively produced during the sintering process, and unreacted hBN will remain, resulting in a decrease in strength. Moreover, when it exceeds 5% by volume, the diamond-CBN bonding strength via the titanium compound decreases. The sintering time is hBN of aluminum nitride → CBN
Since the conversion action and the production reaction of the titanium compound are extremely fast, the reaction time may be extremely short, and approximately 5 minutes is sufficient. After sintering, only heating is stopped while the pressure is maintained, and after the interior of the high-temperature, high-pressure generation chamber is cooled to around room temperature, the holding pressure is gradually released to return to normal pressure. By treating the metal reaction vessel with an acid, only a very strongly sintered hard diamond sintered body can be obtained from the recovered sample. In addition to bits, the sintered body of the present invention can be used for wire drawing dies, ceramic cutting tools, dressers, etc. This will be explained in detail below using Examples. Example 1 Synthetic diamond powder with a particle size of 30 μm, hBN powder with an impurity oxygen content of 0.06% by weight and a particle size of 5 μm, titanium, and aluminum oxide were mixed in a ratio of 65:30 by volume.
The mixture was mixed at a ratio of 2:3 to ensure uniform mixing. When this mixed powder was heat-treated at 1650°C for 3 hours in a nitrogen stream, 3% by volume of the surface of the diamond particles was graphitized, and at the same time, aluminum oxide was reduced by nitrogen to become aluminum nitride. . This finished powder was packed into a container made of M ₀ , and using an ultra-high pressure device, a pressure of 60 Kb was first applied, and then
It was heated to 1650°C and held for 3 minutes. After sintering is complete,
The sample was taken out, and the _M0 container was dissolved in heated aqua regia, and the sintered body was recovered. Analysis of the composition of this sintered body revealed that it contained 67% diamond by volume.
CBN was 27% by volume, Ti (C, B, N) solid solution was 3% by volume, and aluminum nitride was 3% by volume. This diamond sintered body is heated to 1000℃ in a vacuum.
After heating for 30 minutes, the strength was measured by a transverse rupture strength test.
The results are shown in Table 1. For comparison, the strength of a diamond sintered body using a conventional metal binder was also measured and shown in Table 1. The sample number marked with * is this comparative example.

【table】

[Table] Example 2 Finished powders were prepared in the proportions shown in Table 2 and sintered in the same manner as in Example 1. These sintered bodies are used to create cutting tools for cutting granite.
Dry cutting was performed at a speed of 300 m/mm for 20 minutes. The results are also shown in Table 2. For comparison, the results of a diamond sintered body using a conventional metal binding material are also shown. Sample numbers marked with * are comparative examples.

【table】

Claims (1)

[Claims] 1. Consisting of diamond particles and cubic boron nitride, which are bonded to one or more of titanium carbides, borides, nitrides, and/or solid solutions thereof, and aluminum nitride. , and the diamond particles are 30 to 80% by volume, the titanium compound is 0.2 to 5.0% by volume, and the aluminum nitride is 1.0 to 5.0% by volume.
% by volume, and the balance is cubic boron nitride. 2. The composite diamond sintered body according to claim 1, wherein the diamond particles have a particle size of 10 to 100 μm. 3 Consisting of titanium and aluminum oxides and diamond particles and hexagonal boron nitride with an impurity oxygen content of 0.3% by weight or less, and diamond particles are 30 to 80% by volume and titanium is 0.2 to 0.2% by volume.
Heating a mixture of 5.0% by volume, 1 to 10% by volume of aluminum oxide, and the balance being hexagonal boron nitride to 1550°C or higher in an atmosphere containing nitrogen,
At the same time as graphitizing the diamond particle surface, a mixed powder in which aluminum oxide is reduced to aluminum nitride is filled into a metal container that does not easily react with the mixed powder, and the container is placed in a high temperature and high pressure generation chamber. A method for manufacturing a composite diamond sintered body, which comprises holding cubic boron nitride at a stable temperature and pressure for several minutes or more, cooling only the temperature to around room temperature, and then releasing the holding pressure. 4. The method for producing a composite diamond sintered body according to claim 3, wherein the diamond particles have a particle size of 10 to 100 μm. 5. A patent claim characterized in that the temperature and pressure at which both diamond and cubic boron nitride are stable satisfy thermodynamic conditions for aluminum nitride to exhibit a catalytic action for converting hexagonal boron nitride to cubic boron nitride. A method for producing a composite diamond sintered body according to item 3 or 4.