JPS6323155B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a composite sintered body for tools having excellent adhesive strength and a method for manufacturing the same. Cubic boron nitride (hereinafter abbreviated as CBN) is the second hardest material after diamond, has high thermal conductivity, and has excellent chemical stability at high temperatures, so it has attracted attention as a wear-resistant material for metal processing. Used as grinding abrasive grains and cutting tools. In recent years, ultra-high pressure sintering technology has been used to produce fine CBN.
Sintered bodies in which particles are bonded with a metal mainly composed of Co and sintered bodies in which particles are bonded with various ceramics are commercially available. When using these commercially available CBN sintered bodies as machining tools, only the part that will become the cutting edge is
Providing a hard layer containing CBN and bonding this to a highly rigid base material to create a composite material is a good way to increase the strength of the tool. Examples of such compound tools include TiC and TiN.
Cutting tools coated with a WC-based cemented carbide base material are commonly used. WC-based cemented carbide is widely used as a cutting tool because it has high rigidity, excellent toughness, and good thermal conductivity, and is therefore particularly suitable as a base material for sintered bodies for composite tools such as the above. Of course it is suitable. Methods for manufacturing composite sintered bodies include a method in which a CBN-containing hard sintered body is directly bonded to a cemented carbide, and a method in which an intermediate bonding layer is inserted between the CBN-containing hard sintered body and the cemented carbide. There are two possibilities. In the former case, if the CBN binder in the CBN-containing hard sintered body has poor affinity with cemented carbide such as Al ₂ O ₃ , the CBN-containing hard sintered body will not bond to the cemented carbide base material. Almost no adhesion. Furthermore, if a hard sintered body with a high CBN content is directly joined to a cemented carbide base material, CBN and WC-
A large amount of Co _x W _y B _z is produced by the reaction of Co, but
This boride is brittle and has low adhesion strength. Therefore, in order to firmly adhere the CBN-containing hard sintered body to the cemented carbide base material, the latter method using an intermediate bonding layer is preferable. The use of an intermediate bonding layer for bonding CBN-containing hard sintered bodies is disclosed in Japanese Patent Application Laid-open No. 64693/1983, in which high-temperature metal solder is used as the bonding layer. In other words, the CBN hard sintered body and the cemented carbide base material are firmly attached to each other through the high-temperature metal solder. However, when CBN contains Al ₂ O ₃ as a binder, it is difficult to adhere to metal solder. Furthermore, in ultra-high pressure sintering, densification occurs at low temperatures and sintering progresses, so one of the biggest advantages is that grain growth can be suppressed. There is almost no reaction with the adhesive, and the adhesion strength is low. Furthermore, if a metal solder that melts at a low temperature is used, the metal solder component may enter the sintered body, reducing the performance of the sintered body, or the adhesion strength at the joint surface will decrease if the temperature reaches high temperatures during cutting. It cannot withstand use. The inventors of the present invention conducted extensive studies to solve the above-mentioned drawbacks, and found that the characteristics required for an intermediate bonding layer used in bonding a CBN-containing sintered body and a cemented carbide are those obtained by ultra-high pressure sintering. Sometimes, it is possible to firmly bond with CBN-containing hard sintered bodies and cemented carbide base materials at low temperatures, and to prevent excessive residual stress from occurring in the sintered bodies, the thermal expansion coefficient is lower than that of CBN-containing hard sintered bodies and cemented carbide. It is necessary that the material roughly corresponds to that of the alloy base material, and that when used as a cutting tool, it is a material that is difficult to deform at high temperatures so that it will not undergo plastic deformation due to the stress and heat applied to the cutting edge. In order to dissipate heat, it is desirable to use a material with good thermal conductivity, and from the viewpoint of strength, it is not possible to use something that is too brittle. From the above point of view, the content of CBN in the intermediate bonding layer is less than 70% by volume, and the remainder is the element 4a of the periodic table,
carbides, nitrides, carbonitrides, borides or mixtures thereof or mutual solid solution compounds of transition metals of groups 5a and 6a or carbides of group 4a of the periodic table;
It was concluded that materials containing Al or Si in nitrides, carbonitrides, borides, mixtures thereof, or mutual solid solution compounds are suitable. These intermediate bonding layers are CBN and periodic table 4a,
Since it contains one or a mixture of carbides, nitrides, carbonitrides, and borides of Groups 5a and 6a, it has high rigidity and excellent high-temperature strength, and according to the experiments of the present inventors. At low temperatures of 1000-1100℃
Using an intermediate bonding layer made of TiN containing 60% by volume of CBN and the remainder containing Al, the CBN bonding material is Al ₂ O ₃
When a sintered body was created, the CBN-containing hard sintered body was firmly bonded to the cemented carbide base material via the intermediate bonding layer. Furthermore, 20% by volume of CBN at a high temperature of 1500-1600℃
Ultra-high-pressure sintering of a powder containing 80% by volume of CBN and the balance consisting of Al ₂ O ₃ and TiC was performed using an intermediate layer consisting of a mixed powder containing TiN and TaC with the remainder being TiN and TaC. As a result, Co, the bonding metal of the cemented carbide matrix,
Although it penetrated into the intermediate layer, it did not penetrate into the part of the CBN-containing hard sintered body, which is due to the invasion of Co.
It was possible to prevent the performance deterioration of the CBN-containing hard sintered body. As mentioned above, the CBN content is less than 70% by volume, and the remainder is carbides, nitrides, carbonitrides, borides, or mixtures thereof, mutual solid solution compounds, or periodic compounds of group 4a, 5a, and 6a transition metals of the periodic table. Carbides, nitrides, carbonitrides, borides or mixtures thereof or mutual solid solution compounds of Group 4a of the Table of Contents
The reason why a material containing Al or Si is used as the intermediate bonding layer is presumed to be as follows. First of all, the reason why the adhesive strength between the CBN-containing hard material layer and the intermediate bonding layer is high is because the hard layer and the intermediate bonding layer are in contact with each other in a powder state before sintering. This is because a mixed region of both materials is created and sintered. In addition, since CBN particles are contained in the intermediate bonding layer, the binding material of the hard layer and CBN of the intermediate layer react at the bonding surface of the hard layer, and the CBN particles contained as the remainder of the CBN in the intermediate bonding layer are , 5a, 6a group transition metal carbides, nitrides, carbonitrides, borides, etc. are also thought to react with CBN present in the hard layer and adhere firmly. The reason why the intermediate bonding layer and the cemented carbide base material have good adhesion is considered to be as follows. In other words, WC, which is the main component of the cemented carbide base material, and carbides, nitrides, carbonitrides, borides, etc. of transition metals of Groups 4a, 5a, and 6a of the periodic table contained in the intermediate bonding layer are mutually exclusive. In addition to forming a solid solution, these compounds also have good affinity with Co in the cemented carbide base material, so the intermediate bonding layer firmly adheres to the cemented carbide base material. Furthermore, CBN in the intermediate bonding layer
Reaction with Co may also be one of the reasons for strong adhesion. When the intermediate bonding layer forming powder contains Al or Si, its performance as an intermediate bonding layer is further improved. That is, this intermediate bonding layer can be used in a wide temperature range and has even better adhesion.
Especially carbides and nitrides of metals in group 4a of the periodic table,
Among carbonitrides and borides, the effect of using TiN is great. The reason for this is that when Al is added to TiN, the temperature
It can be sintered even at low temperatures of 1,500 to 1,600 degrees Celsius, and can be used without melting even at high temperatures of 1,500 to 1,600 degrees Celsius. Furthermore, it has excellent compatibility with CBN in hard sintered bodies and WC in cemented carbide base materials. This is thought to be because it is in good condition. The intermediate bonding layer in the present invention contains CBN, and as a result, the intermediate bonding layer has high strength and excellent thermal conductivity, and can fully demonstrate the performance of the CBN hard sintered layer. is possible.
When the content of CBN in the intermediate bonding layer is 70% by volume or more, the content of the remaining carbides, nitrides, carbonitrides, borides, etc. of Groups 4a, 5a, and 6a of the periodic table is less than 30% by volume. Therefore, WC at the interface with the cemented carbide
As the ratio of mutual solid solution formation with CBN decreases, boride generated by the reaction between WC-CO and CBN increases too much, and the intermediate bonding layer becomes brittle. Therefore, the content of CBN in the intermediate bonding layer is preferably less than 70% by volume. In addition, the CBN content of the CBN-containing hard sintered body is 20
If it is less than 20% by volume, the performance as a tool will not be good, so 20% by volume or more is preferable. The thickness of the hard layer of the composite sintered body according to the present invention varies depending on the purpose of use, but is generally 0.5 mm to 2 mm.
A range of is suitable. When used as a tool cutting edge for cutting, the width of wear on the tool edge flank when the tool reaches the end of its life due to wear is usually approximately 0.5 mm or less.
It is sufficient to have a hard layer with a thickness greater than that, that is, 0.5 mm or more, and a thickness exceeding 2 mm is not actually necessary. The thickness of the intermediate bonding layer, which is a feature of the present invention, is 2 mm or less. A cemented carbide is used as the base material to be bonded using this intermediate bonding layer. In particular, the WC-based cemented carbide base material has high rigidity and excellent thermal conductivity, and since it contains a metal binder, it also has excellent toughness, making it suitable as a base material. The structure of the composite sintered body for tools according to the present invention is shown in FIG. 1 is a CBN-containing hard sintered body layer used as a tool cutting edge, 2 is a WC-based cemented carbide as a base material,
3 is the intermediate bonding layer of the present invention. The method for manufacturing a composite sintered body according to the present invention includes:
When obtaining an intermediate bonding layer consisting mainly of CBN and carbides, nitrides, carbonitrides, borides, mixtures thereof, or mutual solid solution compounds, these mixed powders are mixed with the cemented carbide base material and the CBN-containing hard layer forming powder. The intermediate bonding layer is formed by applying the required amount in powder form or as a stamped body during the process, or by adding an appropriate solvent to the intermediate bonding layer forming powder and making it into a slurry and applying it to the cemented carbide base material. By hot-pressing this powder layer under ultra-high pressure and high temperature, the CBN-containing hard layer is simultaneously sintered.
An intermediate bonding layer made of carbide, nitride, carbonitride, or boride is sintered and bonded to the base material at the same time. The carbides, nitrides, carbonitrides, borides, etc. of metals in groups 4a, 5a, and 6a of the periodic table used in the present invention are high-strength compounds, but the ultra-high pressure conditions for sintering the CBN-containing hard layer At the bottom (generally 20-90Kb), these compound powder particles are deformed, crushed, and easily packed into a dense state, and by subsequent heating, the intermediate bonding layer becomes a dense sintered body. . 4a, 5a, 6a of the periodic table forming the intermediate bonding layer
Among the group metal compounds, Ti, Zr,
These are carbides, nitrides, and carbonitrides of Hf, a group 4a metal of the periodic table. These compounds, where M is the metal, MCx,
It is expressed in the form MNx, M(C,N)x and can exist in a wide range of values of x outside the stoichiometric composition (x=1). In the present invention, a strong bond is particularly achieved when a non-stoichiometric compound is used in which the value of x is 0.98 or less, preferably in the range of 0.9 to 0.5. The reason is that it has atomic vacancies, which makes it easier to sinter at low temperatures, and when it contains CBN,
This seems to be because it reacts with CBN to form a strong bond and also reacts with the CBN particles in the hard layer and the WC of the base material to form a strong bond to both. In the Examples described later in this application, the values of x of these compounds were all 0.98 or less. In particular, TiNx powder with x=0.8 was used. The composite sintered body of the present invention is used for machining tools, etc., but especially when used in places where interrupted cutting is performed, the CBN-containing hard layer firmly attaches to the cemented carbide base material through the intermediate bonding layer. Because it is attached to the surface, it can fully demonstrate its performance as a composite tool. In particular, the binder of the CBN-containing hard layer is Al ₂ O ₃ , Si ₃ N ₄
Alternatively, when the compatibility with the cemented carbide base material is poor, such as SiC, or when the CBN content of the hard layer is 80% by volume or more, the effect of the intermediate bonding layer according to the present invention becomes even more remarkable. The present invention will be explained in more detail below by way of Examples. Example 1 60% by volume in a Ni container with an inner diameter of 10 mm and an outer diameter of 14 mm
WC-6% Co cemented carbide (outer diameter 10 mm,
3mm in height) and 35% CBN in contact with this.
-0.30g of Al ₂ O ₃ mixed powder was filled. Furthermore, a 3 mm thick cemented carbide and a 0.2 mm thick copper plate were placed on top of this.
Next, a stopper made of Ni was placed and the entire container was placed in an ultra-high pressure apparatus used for diamond synthesis. Pyroferrite was used as the pressure medium, and a graphite cylinder was used as the heater. First increase the pressure to 55kb,
The temperature was then raised to 1100°C and held for 20 minutes. The Ni container was taken out from the ultra-high pressure equipment, and the Ni was cut off. The obtained sintered body has an outer diameter of approximately 10 mm and a thickness of 1 mm.
It was hot. This sintered body is approximately 0.1 mm CBN−TiN−
Although it adhered strongly to the cemented carbide base material with an intermediate bonding layer of Al, it did not adhere to the cemented carbide without an intermediate bonding layer, and the sintered body was easier to bond to the cemented carbide base material than the cemented carbide base material. I was able to peel it off. Example 2 CBN powder with an average particle size of 3μ and TiN in a 9:1 ratio by volume
mixed with. In the same manner as in Example 1, 40 volume% CBN and the balance were added to a cemented carbide base material consisting of WC-6%Co.
A mixed powder consisting of TiN, TiC, and TiAl in a weight ratio of 5:4:1 was applied. In contact with the surface coated with this powder, 60% by volume CBN and 40% by volume
The mixed powder of TiN was filled into a container made of Mo. This was sintered at 1300℃ under ultra-high pressure of 50Kb. The obtained sintered body had CBN firmly bonded to the cemented carbide base material through a 50 μm intermediate bonding layer consisting only of TiN. This composite sintered body was cut using a diamond cutting wheel and brazed to a steel bite shank at approximately 800°C using a regular silver solder for cemented carbide. After brazing, the cutting edge was polished with a diamond grindstone and the state of the bond was examined, and it was found that the diamond sintered body layer and the cemented carbide base material were firmly bonded via the intermediate bonding layer. Furthermore, as a result of examining the intrusion of impurities at the cutting edge using an X-ray microanalyzer, no intrusion of the bonding metal of the cemented carbide was observed. Furthermore, the bonding strength of the CBN-containing hard layer was investigated by cutting a workpiece material (SCM21) that had V grooves at two locations 180° apart in the circumferential direction. The cutting conditions were a cutting speed of 100 m/min, depth of cut of 1 mm, and feed rate of 0.35/rev. For comparison, similar experiments were conducted on a sintered body in which a commercially available CBN-containing hard layer was bonded directly to a cemented carbide base material with Co. As a result, the sintered body of the present invention
Even after passing through the grooves 10,000 times, the sintered body remained firmly attached to the cemented carbide base material, whereas the commercially available Co-bonded sintered body passed through the grooves 7,000 times and the CBN hard layer remained firmly attached. It peeled off from the fruit surface of the hard metal base material. Example 3 WC-10 in a Mo container with an inner diameter of 10 mm and an outer diameter of 14 mm.
Put %Co cemented carbide and 20% CBN by volume on top of it
A disk-embossed body (diameter 10 mm, thickness 0.5 mm) of mixed powder, the remainder of which was TiN and TaC, was placed. Furthermore, it contains 80% by volume of CBN with a particle size of 3μ, and the remainder is
It was filled with a mixed powder of Al ₂ O ₃ and TiC and capped with a Mo stopper. This was placed in an ultra-high pressure device, heated to 1600°C at 70Kb, and held for 20 minutes. In the obtained sintered body, the CBN-containing hard layer was firmly attached to the cemented carbide via the intermediate bonding layer. When the intermediate bonding layer was examined using an X-ray microanalyzer, Co from the cemented carbide base material was present in the intermediate bonding layer, but it did not penetrate into the CBN-containing hard layer and was completely prevented by the intermediate bonding layer. It has been proven that Example 4 A mixed powder shown in Table 1 was prepared. This powder is made into a slurry and applied to a cemented carbide base material consisting of WC-6% Co, placed in a container made of Mo, and on top of this is CBN with a particle size of 3 μm at 80% by volume and the balance is TiC-20% by weight. After filling the powder made of Al, plug it with Mo.
50Kb, sintered at 1400℃ for 15 minutes. These sintered bodies are cut to determine the thickness of the intermediate bonding layer and the hard sintered body.
We investigated the invasion of Co.

[Table] 〓 *: Indicates a comparative example
〓
〓**: Outside the scope of the present invention As a result, in F, intrusion of Co into the hard layer was observed. Next, the bonding strength of these sintered bodies was measured. The results are also shown in Table 1.

[Brief explanation of drawings]

The drawing is a sectional view showing the structure of the composite sintered body for tools of the present invention.

Claims (1)

[Scope of Claims] 1. The content of cubic boron nitride on the cemented carbide base material is less than 70% by volume and 20% by volume or more, and the remainder is from the periodic table.
4a, 5a, 6a group transition metal carbide, nitride, carbonitride or boride, or a mixture or mutual solid solution compound of these;
On this, a powder as an intermediate bonding layer containing 0.1% by weight or more of Al and/or Si is pressed or placed in powder form to a thickness of 2 mm or less, or it is preliminarily placed on the cemented carbide base material. A hard sintered compact powder having a composition with low adhesion strength containing 20% by volume or more of cubic boron nitride, which has a composition different from that of the intermediate bonding layer, is then molded onto the powder or powder. After that, the whole is hot-pressed under ultra-high pressure and high temperature to sinter the hard layer containing cubic boron nitride and the intermediate bonding layer, and to sinter the hard layer, the intermediate bonding layer, and the base material. A method for manufacturing a composite sintered body for tools, characterized by joining. 2. Non-chemical substances in which the value of x is 0.98 or less, preferably in the range of 0.9 to 0.5, when carbides, nitrides, and carbonitrides of Group 4a of the periodic table are expressed as MCx, MNx, and M(C,N)x, respectively. A method for manufacturing a composite sintered body for tools according to claim 1, characterized in that a stoichiometric compound is used.