JPS6350401B2 - - Google Patents

Description

[Detailed description of the invention]

Currently, sintered bodies with a diamond content of 70% or more by volume and diamond particles bonded to each other are on sale, and are used for cutting non-ferrous metals, plastics, and ceramics, dressers, drill bits, and wire drawing dies. 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 invention relates to a diamond sintered body that can also be used in drill bits. First, in order to investigate the reason why commercially available diamond sintered bodies do not show satisfactory performance when used as drill bits, we investigated whether the particle size was 1 μm or less and the particle size was 30 to 60 μm.
Andesite was cut using three types of diamond sintered bodies with particle sizes of 80 to 100 μm. As a result, the particle size is 1μ
Although the cutting edge of the diamond sintered body with a diameter of less than m was not damaged, there was a large amount of wear. On the other hand, a sintered body with a diamond particle size of 30 to 60 μm and a diamond particle size of 80 to 100 μm
The cutting edge of both sintered bodies was damaged at the cutting stage. The reason for this can be inferred as follows. As shown in FIG. 1, the strength of the diamond sintered body decreases as the grain size increases. Fine-grained diamond sintered bodies have high transverse rupture strength and excellent toughness, so the cutting edge is less prone to breakage, but individual particles are held in place by small diamond skeletons.
The binding force between individual particles is weak. Therefore, individual particles tend to fall off during cutting, which is thought to result in poor wear resistance. On the other hand, the coarse diamond sintered body is held by a large skeleton,
Since the bonding force between the individual diamond particles is strong, it has excellent wear resistance, but since the skeleton is large, once a crack occurs, it is likely to propagate and cause the cutting edge to break. A diamond sintered body that can be used for these purposes must have excellent wear resistance and high toughness. The present inventors continued intensive research in order to develop a diamond sintered body with excellent wear resistance and toughness.
As a result, diamond particles with a particle size of 10 to 100 μm are mixed with ultrafine diamond particles of 1 μm or less and 1 μm in diameter.
A sintered body using the following WC or (Mo, W)C having the same crystal structure and an iron group metal, or a binder containing a trace amount of boron or boride is a coarse-grained diamond sintered body. It was found that this material has both good wear resistance and the high toughness of an ultrafine diamond sintered body. In order to find the optimal composition of the above-mentioned material, the present inventors prototyped diamond sintered bodies with different coarse diamond particle size and content, and the content of diamond particles of 1 μm or less included in the binder.
Evaluation was made by cutting andesite. The results are shown in FIGS. 2 and 3. In the figure, 1 indicates normal wear, and 2 indicates the area where the cutting edge is damaged. Coarse diamond grain size is 10μ
If it is less than m, wear resistance decreases. When the coarse diamond particle size exceeds 100 μm, cracks occur within the diamond particles during sintering, and the cutting edge is thought to be damaged through these cracks, increasing the amount of wear. The content of coarse diamond particles is preferably 50 to 85% by volume. If the content of coarse diamond particles is less than 50%, the amount of binder containing fine diamond particles increases, resulting in decreased wear resistance. On the other hand, if the content of coarse diamond exceeds 85%, the toughness decreases because the coarse diamonds bond together. The particle size of the fine diamond particles in the binder is
1μm or less is good. The particle size of the fine diamond particles is preferably 1 μm or less, preferably 0.5 μm or less. When the particle size of fine diamond particles exceeds 1 μm, toughness decreases. The content of fine diamond particles in the binder is preferably 60 to 90% by volume. If the content of fine diamond particles is less than 60%, the wear resistance of the binder phase decreases, the binder phase wears out early, and coarse diamond particles fall off. On the other hand, if the content of fine diamond particles exceeds 90%, the binder becomes brittle, or the content of WC or (Mo, W)C, which has the same crystal structure, decreases, resulting in diamond particles of 1 μm or less grow,
Toughness decreases. It is preferable that the ratio of WC used as a part of the binder or (Mo, W)C having the same crystal structure as this and iron group metal has a higher carbide content than that corresponding to its eutectic composition. For example, in WC-Co, the eutectic composition is 48% by weight WC-Co52% by weight.
If the carbide content is less than the amount equivalent to the eutectic composition, no carbide is precipitated and diamond growth cannot be suppressed. This is because carbide has the effect of suppressing the growth of diamond grains in the binder phase. Further, the upper limit of the carbide content is up to 95% by weight. If there is too little metal, a sintered body with sufficient strength cannot be obtained. In particular, the sintered body of the present invention has a weight of 0.005~
When containing 0.15% boron or boride, the performance is further improved. Usually, diamond particles are sintered under ultra-high pressure and high temperature by the phenomenon of diamond dissolution and precipitation using a catalyst such as an iron group metal. When boron or a boron compound is added, borides of iron group metals are produced, which lowers the melting point. At the same time, the melt deposition rate increases, which causes the bond between diamond particles (diamond skeleton) to grow, which reduces the holding power of the diamond particles. It can be assumed that this has improved. If the content of boron or boride is less than 0.005%, the formation of the diamond skeleton portion will be slow. On the other hand, if the boron or boride content exceeds 0.15%, a large amount of boron will enter the diamond skeleton, reducing the strength of the diamond skeleton. Next, the diamond sintered body of the present invention was directly WC
- A core bit was created by brazing a blank bonded to a Co plate onto the bit body, and an excavation test was conducted. As a result, when the excavation conditions were made more severe, the diamond sintered body did not break off, but a problem occurred in which the diamond sintered body peeled off from the WC-Co base material. In particular, as the brazing temperature increased, the frequency of peeling increased. To investigate the cause of this, we observed the structure near the joint and found that there was a Co-enriched layer at the interface between the diamond sintered body and the cemented carbide. Furthermore, free carbon was present in the cemented carbide near the interface. The brazing temperature is generally
Although the temperature is 750 to 800°C, there is a large amount of Co present at the interface, and it is thought that this Co causes the diamond to become graphitic, reducing its strength and causing it to peel off. Furthermore, the presence of free carbon in the cemented carbide reduces the strength of the cemented carbide, which is also considered to be a cause of peeling. In order to obtain a high-strength bond, the present inventors conducted various studies and found that high-pressure phase boron nitride was used in an amount of 70% by volume or less, and the remainder was carbides and nitrides from groups 4a and 5a of the periodic table.
We discovered that it is better to use the intermediate layer that remains from carbonitride. According to experiments conducted by the present inventors, the diamond sintered body and the cemented carbide base material were firmly bonded via this intermediate bonding layer under the ultra-high pressure and high temperature conditions for manufacturing the diamond sintered body. These composite sintered bodies with an intermediate bonding layer consisting of high-pressure phase boron nitride, carbides, and nitrides were leaked from the cemented carbide base material, etc. at the interface between the diamond sintered body layer and the intermediate bonding layer.
Diamond solvent metals such as Co are not present in large quantities,
The area where the diamond particles and the intermediate bonding layer are in direct contact is large. Therefore, no decrease in strength occurs due to reheating. Furthermore, since almost no free carbon exists in the cemented carbide near the interface, the bonding strength is high. As described above, according to the present invention, the diamond sintered layer can be firmly attached to the cemented carbide base material, which is very useful. Guessed. First, regarding the adhesion between the intermediate bonding layer and the cemented carbide base material, the carbides and nitrides of groups 4a and 5a of the periodic table contained in the intermediate bonding layer are the main components of the cemented carbide base material. The high-pressure phase boron nitride in the intermediate layer forms a mutual solid solution with WC, which is
Since it reacts with WC-Co to produce boride, the two are thought to adhere firmly. Next, regarding the adhesion between the intermediate bonding layer and the diamond sintered body, diamond powder, iron group metals, carbides, and nitrides that are usually used as a bonding phase for diamond, carbides of groups 4a and 5a of the periodic table in the intermediate bonding layer, It has excellent affinity with nitrides, and since the intermediate bonding layer and the diamond sintered body layer are in contact with each other in a powder state before sintering, after sintering, the intermediate bonding layer and the diamond sintered body layer form a mixed layer. exists,
It is thought that the bonding is strong. In addition, by adding 0.1% by weight or more of Al or Si to carbides and nitrides of groups 4a and 5a of the periodic table,
The sinterability of the intermediate bonding layer itself is improved, and the affinity between these carbides and nitrides and diamond particles is also improved. In particular, the effect will be greater if TiN, which is a nitride in Group 4a of the periodic table, contains 0.1% by weight or more of Al. Since the intermediate bonding layer according to the present invention contains high-pressure phase type boron nitride, it has high thermal conductivity, high high-temperature strength, and can have a coefficient of thermal expansion comparable to that of a diamond sintered body. When the content of high-pressure phase type boron nitride exceeds 70% by volume, the remaining periodic table
The amount of carbides and nitrides of groups 4a and 5a becomes less than 30% by volume, and the amount of mutual solid solution formed between these carbides and nitrides and WC, which is the main component of the cemented carbide matrix, decreases, and furthermore, the intermediate bonding High-pressure phase boron nitride in the layer and
Since the boride produced by the reaction of WC-Co is brittle,
The adhesive strength between the intermediate bonding layer and the cemented carbide base material tends to decrease. Therefore, the content of high-pressure phase boron nitride in the intermediate bonding layer is preferably less than 70% by volume. The base material to be bonded using this intermediate bonding layer is
A WC-Co cemented carbide or a cermet made by bonding (Mo, W)C type carbide crystals containing Mo as the main component with an iron group metal is good. WC―Coya (Mo, W)
The C-iron group metal base material has high rigidity and excellent thermal conductivity, and since it contains a metal binder, it also has good toughness, so it is suitable as a base material for a diamond sintered body for a drill bit. Examples of the carbides and nitrides in the intermediate bonding layer of the present invention include carbides such as TiC, ZrO, HfC, NbC, and TaC, nitrides such as TiN, ZrN, HfN, NbN, and TaN, and mixtures thereof and Ti. (C,
Carbonitrides such as N) and Zr(C,N) are used. In particular, when TiN is used, the performance as an intermediate bonding layer is the best. The diamond raw material powder used for the sintered body of the present invention includes diamond particles of 10 μm or more, diamond particles of 1 μm or less,
Preferably it is a micron powder of 0.5 μm or less. Either synthetic diamond or natural diamond may be used. This diamond powder and WC or (Mo,
W) C and powders of iron group metals such as Fe, Co, and Ni or powders obtained by adding boron or boride to these powders are uniformly mixed using a means such as a ball mill. This iron group metal may be infiltrated during sintering without being mixed in advance. In addition, the inventors' earlier application (Japanese Patent Application No. 52-51381)
Mix the pot and ball during ball milling as in
It is made of WC or (Mo, W)C carbide and a sintered body of iron group metal, and at the same time as the diamond powder is ground in a ball mill, WC is produced from the pot and ball.
Alternatively, there is also a method of mixing (Mo, W)C with fine powder of a sintered body of an iron group metal. A method for producing a sintered body of these mixed powders is to place the required amount of high-pressure phase boron nitride and carbide or nitride powder between the cemented carbide base material and the diamond-containing hard layer-forming powder in powder form or As a embossed body,
In addition, a powder layer that forms an intermediate bonding layer is provided by applying a powder made into a slurry by adding an appropriate solvent to the cemented carbide base material, and this is hot-pressed under ultra-high pressure and high temperature to form a diamond bonding layer. It is also possible to adopt a method in which an intermediate bonding layer made of carbide or nitride is sintered simultaneously with the sintering of the containing hard layer, and bonded to the base material at the same time. 4a of the periodic table in the intermediate bonding layer used in the present invention,
Carbides and nitrides of group 5a metals are high-strength compounds, but under the ultra-high pressure conditions (generally 20Kb to 90Kb) used to sinter the diamond-containing layer, pressure close to the ideal shear strength of these compounds is required. has been
These compound powder particles are deformed, crushed, easily packed into a dense state, and then heated to form a dense sintered body. In addition, it is also possible to impregnate a molten diamond-forming catalyst metal or other binding metal into the diamond powder layer under ultra-high pressure and high temperature. In the diamond sintered body directly bonded to the currently commercially available cemented carbide base material mentioned above, Co, which is the bonding metal contained in the cemented carbide base metal, penetrates into the diamond powder layer and the bonding metal of the diamond sintered body. becomes. In the case of the present invention, the bonding metal can be selected regardless of the bonding metal of the base cemented carbide. This will be explained in detail below using Examples. Example 1 Synthetic diamond powder with particle size of 0.5 μ and WC and Co
The powder was ground and mixed using a pot and ball made of WC—Co cemented carbide. The composition of the obtained mixed powder was as follows: 80% by volume of fine diamonds with an average particle size of 0.3 μm;
WC was 12% by volume and Co was 8% by volume. This mixed powder and diamond powder with a particle size of 20 to 30 μm are combined by volume.
Mixed at 75:25. To this powder was added 0.15 weight of B powder. Next, a powder consisting of TiN containing 60% by volume of cubic boron nitride (CBN) and the balance 20% by weight of Al was applied to the top surface of a cemented carbide with an outer diameter of 10 mm and a height of 3 mm having a WC-6% Co composition. The slurry was mixed into an organic solvent containing the liquid and applied. This cemented carbide was packed in a Mo container and filled with hard layer powder containing diamond so as to be in contact with the intermediate layer containing cubic boron nitride. Subsequently, it was heated to 1500°C and held for 20 minutes. After cooling, the sintered body was taken out and observed.
Diamond particles of 20 to 30 μm were bonded together via a binder containing ultrafine diamond particles. Furthermore, at the bonding interface, the diamond sintered body was firmly bonded to the cemented carbide via an intermediate layer containing cubic boron nitride. Using this composite sintered body, a core bit consisting of four teeth with an outer diameter of 46 mm was created, and the compressive strength was 1800 Kg/cm ²
andesite was excavated at a speed of 250 revolutions per minute. The bit load was 800 kg. For comparison, a commercially available diamond sintered body for bits and a core bit made of the above-mentioned diamond sintered body directly bonded to cemented carbide without using an intermediate layer were also prototyped, and similar tests were conducted. As a result, the diamond sintered body of the present invention could be used even after 20m excavation without any breakage, whereas the core bit using a commercially available diamond sintered body for bits could be used after 5m excavation. in,
The life of the diamond sintered body was reached due to chipping and peeling. In addition, the hard layer has the same composition as the sintered body of the present invention, but the core bit of the sintered body without the intermediate bonding layer is
After excavating 15m, the diamond sintered body separated from the cemented carbide. Example 2 A binder powder shown in Table 1 was prepared. The fine diamond particles used were those with a diameter of 0.3 μm.

[Table] Finished powders were prepared by mixing this binder and diamond particles with a particle size of 5 μm or more in the proportions shown in Table 2.

【table】 Next, intermediate layer powders shown in Table 3 were created.

[Table] This intermediate layer powder was mixed into an organic solvent containing ethyl cellulose to form a slurry, and the slurry was applied to a cemented carbide with a WC-8% Co composition. This cemented carbide was placed in a Mo container, and filled with the diamond-containing powder shown in Table 2 so as to be in contact with the intermediate layer powder. This was subjected to ultra-high pressure sintering in the same manner as in Example 1 to create a diamond sintered body, and a core bit consisting of three teeth was prototyped. Table 4 shows the composition of the prototype diamond sintered body and the intermediate layer. Using this bit, andesite with an unconfined compressive strength of 2000Kg/cm ² was processed at a speed of 50m/min.
Excavated 10m. The test results are shown in Table 4.

【table】

[Table] Example 3 WC-6%Co cemented carbide (Mo, W)C-10%
A diamond sintered body was produced as a prototype in the same manner as in Example 1 except that Ti and 10% Co were used, and a core bit consisting of four teeth was produced. Using this bit, andesite with a compressive strength of 1700 Kg/cm ² was excavated for 20 m at a speed of 100 m/min, but the diamond sintered body did not break or peel. Example 4 Synthetic diamond powder with a particle size of 0.5 μm and WC and
Co powder was ground and mixed using a pot and ball made of WC—Co cemented carbide. The composition of the obtained mixed powder was 80% by volume of fine diamond with an average particle size of 0.3 μm, 12% WC, and 8% Co. This mixed powder and diamond powder having a particle size of 20 to 30 μm were mixed in a volume ratio of 75:25. Table 5
The amount of B powder shown in was added. Table 5 Addition amount of B Flank wear width (mm) 1 0.001 0.15 2 0.01 0.09 3 0.05 0.08 4 0.10 0.07 5 0.20 0.13 6 0 0.16 A diamond sintered body was obtained in the same manner as in Example 1. These sintered bodies are processed to have an outer diameter of 8.2 mm.
We made chips for cutting, and achieved a Vickers hardness of
A 1600 alumina round bar was cut for 10 minutes at a cutting speed of 50 m/min, depth of cut of 0.3 mm, and feed rate of 0.1 mm/rotation. Table 5 also shows the results of measuring the amount of flank wear.

[Brief explanation of drawings]

FIG. 1 shows the relationship between strength (transverse rupture strength) and diamond particle size in a diamond sintered body. FIG. 2 shows the particle size of coarse diamond particles and rock cutting performance in the sintered body of the present invention. FIG. 3 is a graph showing the content of coarse diamond and rock cutting performance in the sintered body of the present invention.

Claims (1)

[Claims] 1. Coarse diamond particles with a particle size of 10 μm or more and 100 μm or less account for 50 to 85% by volume, and the remainder is 60 to 90% by volume of ultrafine diamond particles with a particle size of 1 μm or less.
and WC of 1 μm or less, or a binding material composed of (Mo, W)C and iron group metals having the same crystal structure, and used as a part of the binding material.
WC or has the same crystal structure (Mo,
W) The hard sintered body made of a binder whose ratio of C and iron group metal is higher than that corresponding to its eutectic composition contains high-pressure phase boron nitride at 70% by volume or less and the remainder. Carbides of groups 4a and 5a of the periodic table,
Consisting of nitrides, carbonitrides, solid solutions or mixtures of two or more of these, or
WC-Co through an intermediate layer with a thickness of 2 mm or less containing 0.1% or more of Al or Si or both by weight.
Alloy base material or Mo-based main component (Mo, W)
A composite diamond sintered body for tools, characterized in that it is formed by joining a C-type carbide crystal to a cermet base material bonded with an iron group metal. 2. The composite diamond sintered body for tools according to claim 1, wherein the nitride of Group 4a of the periodic table, which is a component of the intermediate layer, is TiN. 3 Coarse diamond particles with a particle size of 10 μm or more and 100 μm or less account for 50 to 85% by volume, and the remainder is 60 to 90% by volume of ultrafine diamond particles with a particle size of 1 μm or less.
and WC of 1 μm or less or (Mo, W)C and iron group metals with the same crystal structure as 0.005 by weight
Contains ~0.15% boron or/and boride,
WC or has the same crystal structure (Mo,
W) The ratio of C and iron group metals is that the hard sintered body has a higher carbide content than that corresponding to its eutectic composition, and the hard sintered body contains high-pressure phase boron nitride at 70% by volume or less, and the remainder is from the periodic table. An intermediate layer with a thickness of 2 mm or less consisting of carbides, nitrides, carbonitrides of groups 4a and 5a, solid solutions or mixtures of two or more of these, or containing 0.1% or more of Al or Si or both by weight. A composite diamond sintered tool for tools is characterized by being bonded to a cermet base material in which a WC-Co alloy base material or a (Mo, W)C type carbide crystal mainly composed of Mo is bonded with an iron group metal. Body. 4. The composite diamond sintered body for tools according to claim 3, wherein the nitride of group 4a of the periodic table, which is a component of the intermediate layer, is TiN.