JPS6359381B2 - - Google Patents

Description

[Detailed description of the invention]

Currently, among the high-pressure phase boron nitrides, products in which a sintered body of cubic boron nitride (hereinafter referred to as CBN) is bonded to one side of a WC-Co alloy are commercially available. As a typical example of this CBN sintered body, during sintering, molten metal mainly composed of Co from WC-Co intrudes between CBN particles, serves as a binder for the CBN particles, and transforms the sintered body into a cemented carbide. There are some that are joined. This technique is disclosed in Japanese Patent Publication No. 52-43846. The present inventors first carried out additional tests on the embodiment disclosed in the above-mentioned patent publication. We also learned that it is actually quite difficult to use a embossed WC-Co body as shown in the examples. The difficult points are that WC-Co is an extremely fine powder, so it contains a large amount of gas components, which is difficult to deal with, and the embossed body has low strength, so it is difficult to maintain its shape during hot pressing. It is. Therefore, the present inventors next considered using a WC-Co sintered body. Using a sintered body solves the above two problems, but the problem is that it causes cracks. this is
During hot pressing, the stress that exceeds the strength of WC-Co is usually raised to the required pressure first and then the temperature is increased, so WC-Co cannot follow the deformation of the hot pressed part during this pressure increase. It was concluded that In order to follow this deformation, it would be better to use a WC-Co alloy that has a large plastic deformability until fracture, but such an alloy has a large amount of Co or
The viscosity of the WC crystal is high. However, alloys with high plastic deformability have low rigidity;
In particular, the rigidity at high temperatures decreases, reducing the significance of using it as a sintered body for cutting tool edges. Therefore, one of the present inventors, together with other researchers, is actively researching (MoW)C in iron group metals, especially
We focused on the use of alloys bonded with Ni and Co. One of the inventors, in collaboration with other researchers, (MoW)C
The manufacturing method of (MoW) C-based cermet, and the characteristics of this cermet are being investigated. When we investigated the properties measured as a result, we found that this cermet largely covered the drawbacks of WC-Co mentioned above. That is, as shown in FIG. 1, (MoW) C-based cermets are softer than WC-based cermets at room temperature, but are harder at high temperatures. This is particularly important in cutting tool applications. Also, as shown in Figure 2, (MoW)C-Co
The amount of strain required to break is significantly larger than that of WC-Co. The characteristics of the (MoW) C-based cermet shown in FIG. 2 are well suited to the above-mentioned object of the present invention. In other words, an alloy with high plastic deformability and high rigidity has been discovered. The point of the present invention lies in the combination of the above-mentioned required performance during hot pressing under ultra-high pressure with the new performance exhibited by the new alloy. Other properties, such as transverse rupture strength, thermal conductivity, coefficient of thermal expansion, corrosion resistance, and oxidation resistance, are determined by WC.
There is almost no difference between -Co and (MoW)C-Co. Therefore, the inventors proposed this (MoW)
Various CBN sintered bodies were created using C-based cermet as a base material. As a result (MoW), although it was possible to prevent cracks from occurring in the C-based cermet base material,
The following problems were found. Firstly
If the content of CBN is high in the CBN sintered body, the high temperature and pressure during sintering will cause iron group metals, which are components of the (MoW) C-based cermet base material, to flow into the sintered body, causing the sintered body to The composition of the material changes and the performance deteriorates. Furthermore, there is a region enriched with iron group metals at the interface between the sintered body and the (MoW) C-based cermet base material, where CBN and iron group metals react and produce a large amount of boride. Since boride is very brittle, it reduces the bonding strength at the interface. secondly
When the CBN binder has poor affinity with the (MoW) C-based cermet, such as Al ₂ O ₃ , the CBN sintered body hardly adheres to the (MoW) C-based cermet. In order to solve the above problems, an intermediate bonding layer is placed between the CBN sintered body and the (MoW) C-based cermet to prevent the intrusion of iron group metals from the (MoW) C-based cermet, and the CBN sintering The bonding strength of the body-intermediate bonding layer (MoW) C-based cermet may be increased. The use of an intermediate bonding layer is disclosed in JP-A-Sho.
No. 51-64693, the intermediate bonding layer is a high temperature metal solder. 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. In order to be able 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 coefficient of thermal expansion is lower than that of CBN-containing hard sintered bodies and cemented carbide. The material must almost match that of the base material, and when used as a cutting tool, the material must be 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. It is desirable that the material has good thermal conductivity in order to allow the heat to escape, and from the viewpoint of strength, it is also necessary that it not be very brittle. As a result of various studies from the above viewpoint, we found that the intermediate bonding layer should be made of nitrides of group 4a and 5a transition metals of the periodic table, mixtures thereof, or mutual solid solution compounds, or 70% of these nitride compounds or mutual solid solution compounds. Materials containing less than % by volume of CBN, or nitrides of transition metals of groups 4a and 5a of the periodic table, or mixtures thereof, or mutual solid solution compounds containing Al and/or Si, or nitrides or mixtures thereof. It was concluded that a material containing less than 70% by volume of CBN in a mutual solid solution compound is suitable. These intermediate bonding layers are made of nitrides of groups 4a and 5a of the periodic table or contain CBN, and therefore have high rigidity and excellent high-temperature strength. By using an intermediate layer containing 20% by volume of CBN and the remainder consisting of TiN powder, the content of CBN is 80% by volume.
Ultra-high pressure sintering of the powder, the balance of which was Al ₂ O ₃ and TiC, was carried out. As a result (MoW), although Ni and Co, which are the bonding metals of the C base material, had invaded the intermediate layer,
The CBN-containing hard sintered body does not penetrate into the parts of the CBN-containing hard sintered body, and it is possible to prevent the deterioration of the performance of the CBN-containing hard sintered body due to the intrusion of iron group metals. It was firmly bonded to the base material. Furthermore, even at low temperatures of 1000 to 1100°C, a sintered body containing Al ₂ O ₃ as the CBN binder was created using an intermediate layer made of TiN containing 60% by volume of CBN and the remainder containing Al. The aggregate was firmly bonded to the (MoW) C base material via the intermediate bonding layer. When the intermediate bonding layer of the present invention is used as described above,
Even when ultra-high pressure sintering is performed at high temperatures of 1500 to 1600°C, it is possible to prevent the intrusion of iron group metals from (MoW) C-based cermets and to firmly bond them to the base material. It is also possible to firmly bond the CBN-containing hard sintered body and (MoW) C-based cermet during bonding. The reason for this is assumed to be as follows. (MoW) The reason why the intrusion of iron group metals from C-based cermets can be prevented is because iron group metals have poor affinity with nitrides in groups 4a and 5a of the periodic table. This is probably because even if the phase appears, the rate of penetration into the intermediate bonding layer is slow. Next, the bonding strength between the CBN-containing hard sintered body and the intermediate bonding layer is high due to the periodic table 4a in the intermediate bonding layer.
The 5a group nitride reacts with CBN in the hard sintered body layer, and the intermediate bonding layer and hard layer are in contact with each other in a powder state before sintering, so in this region, both layers have a width of a few particles. This is probably because a mixed region of both materials is created and sintered. The reason why the intermediate bonding layer and the (MoW) C-based cermet base material are well bonded is considered to be as follows. This is thought to be due to the fact that (MoW)C, which is the main component of the (MoW)C-based cermet, and the nitrides of transition metals from groups 4a and 5a of the periodic table contained in the intermediate bonding layer form a mutual solid solution. When the intermediate bonding layer forming powder contains Al or Si, the 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 good adhesive properties. The effect is particularly great when TiN, which is a nitride in Group 4a of the periodic table, is used. The reason for this is that when Al is added to TiN, sintering is possible even at low temperatures of 800 to 900℃.
This is thought to be because it can be used without melting even at high temperatures of 1,500 to 1,600°C and has good affinity with CBN in the hard sintered body and (MoW)C in the (MoW)C-based cermet. When the intermediate bonding layer of the present invention contains high-pressure phase boron nitride, the strength of the intermediate bonding layer is high, and the thermal conductivity is also very excellent, making it possible to fully demonstrate the performance of the CBN hard sintered layer. It is possible. When the content of CBN in the intermediate bonding layer is 70% by volume or more, the content of the remaining nitrides of 4a and 5a of the periodic table, or their mixtures or mutual solid solutions, is less than 30% by volume, and it is different from the base alloy. The rate at which a mutual solid solution is formed with (MoW)C at the interface of (MoW)C decreases, and boride generated by the reaction between (MoW)C-based alloy and CBN increases too much, making the intermediate bonding layer brittle. Furthermore, since this boride has a low melting point, especially when sintered at a high temperature, a large amount of liquid phase is generated in the intermediate bonding layer and penetrates into the hard layer, degrading the performance. 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 0.005
The diameter is not less than mm and not more than 2 mm. If the thickness of the intermediate bonding layer is less than 0.005 mm, it may not be possible to prevent the bonding metal from entering the C base material during high temperature sintering (MoW). Further, an intermediate bonding layer of 2 mm or more is not practically necessary. The method for manufacturing a composite sintered body according to the present invention includes:
When obtaining an intermediate bonding layer mainly composed of nitrides of Groups 4a and 5a of the periodic table, mixtures thereof, or mutual solid solution compounds, or those mainly containing CBN, these mixed powders are mixed with (MoW)C. The required amount of C-base is added between the base cermet base material and the CBN-containing hard layer-forming powder in powder form or as a stamped body, or by adding an appropriate solvent to the intermediate bonding layer-forming powder and making it into a slurry (MoW). A powder layer that forms an intermediate bonding layer is provided by applying it to the cermet base material, and this is hot-pressed under ultra-high pressure and high temperature to sinter the intermediate bonding layer simultaneously with the sintering of the CBN-containing hard layer. Join it to the base material. In addition, as the intermediate bonding layer, periodic table 4a,
If a nitride in which the value of x of the nitride represented by MNx is 0.5 or more and 0.95 or less is used, where M is a group 5a transition metal, the sinterability of the intermediate bonding layer will increase and the bonding strength will be good. The reason for this is that it is easy to sinter at low temperatures due to the presence of atomic vacancies, and when CBN is contained, it reacts with CBN to form a strong bond, and also reacts with CBN particles in the hard layer and WC in the base material, resulting in both This is thought to be due to the strong bond between the two. The value of
If it is less than 0.5, the strength of the nitride of transition metals belonging to groups 4a and 5a of the periodic table decreases, which is not preferable. Also X
When the value exceeds 0.95, the bonding strength decreases. The nitrides of metals 4a and 5a of the periodic table used in the present invention are high-strength compounds, but the CBN-containing hard layer is sintered under ultra-high pressure conditions (generally
90 kb), 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. 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 adheres to the cermet base material through the intermediate bonding layer. Because of this, it can fully demonstrate its performance as a compound 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 cermet 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. Note that equivalent performance can be obtained even if part or all of the CBN used in this paper is replaced with Wurtz type boron nitride, which is a type of high-pressure phase type boron nitride. The present invention will be explained in detail below with reference to Examples. Example 1 30% by volume in a Mo container with an inner diameter of 10 mm and an outer diameter of 14 mm
A cermet with a C-15.3% Co composition (Mo _0.7 W _0.3 ) was prepared by making a slurry of TiN0.7 powder containing CBN and the balance 20% Al in an organic solvent to a thickness of 0.2 mm (outer diameter 10 mm). , height 3 mm), and 0.3 g of a mixed powder of 80% by volume CBN and TiN-Al-Cu-Ni was filled in contact with this. Furthermore, Ta foil, 3 mm thick (MoW) C cermet, and 0.2 mm copper plate were placed on top of this. Next, a Ni stopper was placed on the container, and the entire container was placed in an ultra-high pressure device 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 increased to 1500°C and held for 20 minutes. The Ni container was removed from the ultra-high pressure device, the Mo was removed, and the inside of the container was observed. There are no cracks in the (Mo _0.7 W _0.3 )C cermet base material, and the CB-containing hard sintered body is firmly bonded (Mo _0.7 W _0.3 )C through the intermediate bonding layer.
It was attached to the top. When this composite sintered body was cut and the bonding interface was observed (Mo.W), it was found that the iron group metal, which is the binder in the C cermet, was present in a part of the intermediate bonding layer, but the CBN-containing hard sintered body It was not present in the body, and the sintered body remained with the composition of the finished powder. For comparison, ultra-high pressure sintering was performed under the same conditions as in the above case except that WC-15.3v/oCo cemented carbide was used as the base material instead of the (MoW) C-based cermet coated with the intermediate bonding layer. did. When the inside of the container was observed, cracks were found in the WC-based cemented carbide base material. Furthermore, when the bonding interface was observed, a large amount of Co, which is the bonding metal of the cemented carbide base material, had penetrated into the CBN sintered body. Example 2 CBN powder with an average particle size of 3 μm and Al ₂ O ₃ powder were mixed in a volume ratio of 1:1. (Mo _0.9 W _0.1 )C-5%Ni
A mixed powder consisting of 60% CBN by volume and the balance TiN _0.8 , ZrN _0.7 , and Al in a ratio of 5:4:1 was applied to a -5% Co cermet base material in the same manner as in Example 1. 50% by volume in contact with the surface coated with this powder
A mixed powder consisting of CBN and Al ₂ O ₃ was filled into a container made of Mo. This was sintered at 1100℃ under ultra-high pressure of 50kb. The obtained sintered body was firmly bonded to the (Mo.W) C-based cermet base material through the intermediate bonding layer, and no cracks were present in the (Mo.W) C-based cermet. Example 3 A Ni container with an inner diameter of 10 mm and an outer diameter of 14 mm (Mo _0.5
W _0.5 ) C-19%Co cermet (outer diameter 10mm height 3
The intermediate bonding layer forming powder having the composition shown in Table 1 was molded into a container with an outer diameter of 10 mm and a thickness of 0.3 mm, and then placed in a container.
A mixed powder containing Al in a ratio of 6:2:2 by weight was filled. After placing Ta foil on top of this (Mo _0.7 W _0.3 )
Place a C-19% Co cermet and plug it with a Ni plug.

[Table] As in Example 1, sintering was carried out at a pressure of 50 kb and a temperature of 1350°C. These sintered bodies were taken out and placed in a steel bite shank using ordinary silver brazing material for cemented carbide.
Brazed at ℃. After brazing, the cutting edge is polished with a diamond whetstone.
When the bonding conditions were examined, all sintered bodies were firmly bonded to the (MoW)C cermet base material via an 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 binding metal of the (MoW) cermet was observed. Furthermore, the bonding strength of the CBN-containing hard layer was investigated by cutting hardened carburized steel that had V-grooves spaced 180° apart at two locations 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 having intermediate bonding layers A to E was firmly attached to the (Mo.W)C cermet base material even after passing through the groove 10,000 times. A commercially available Co-bonded sintered body passed through the groove 7000 times, and the CBN hard layer was peeled off from the surface of the cemented carbide base material.

[Brief explanation of drawings]

FIG. 1 is for explaining the effects of the present invention, and compares the high-temperature Vickers hardness of the (MoW) C-based cermet used in the present invention and a conventional WC-Co cemented carbide. Binding phase metal content is 11vol%,
Two types of alloys each containing 15.3 vol% are shown. FIG. 2 compares the stress-strain curves of the (MoW) C-based cermet used in the present invention and a conventional WC-Co cemented carbide under compressive stress. Curved ×
The point indicated by the mark is the point of compression failure, and the vol% of the bonded metals is equal to WC−11vol%Co(1) and (Mo _0.7
W _0.3 ) C-11vol%Cc(3), it can be seen that the latter has a significantly large plastic deformation ability. The symbols in the drawings indicate the following compositions (volume %): 1...WC-11Co, 2...WC-15.3Co, 3...
...(Mo _0.7 W _0.3 )C-11Co, 4...(Mo _0.7 W _0.3 )
C-15.3Co, 5...WC-16Co, 6...WC-
24Co, 7...(Mo _0.5 W _0.5 )C-19Co,.

Claims (1)

[Scope of Claims] 1. A cermet in which a hard sintered body containing 20% to 95% by volume of high-pressure phase boron nitride and a C-based carbide crystal mainly composed of molybdenum (MoW) are bonded by an iron group metal. The base material is bonded to the base material via an intermediate bonding layer, and the intermediate bonding layer is mainly composed of one of the nitrides of transition metals of Groups 4a and 5a of the periodic table, a mixture thereof, or a mutual solid solution compound, or A tool for a tool, characterized in that it mainly contains less than 70% by volume of high-pressure phase boron nitride, has a composition different from the hard sintered body, and has a thickness of 0.005 mm or more and 2 mm or less. Composite sintered body. 2. In the composite sintered body according to claim 1, the hard sintered body contains 20% by volume of high-pressure phase boron nitride.
Above 95% by volume, the balance being Al ₂ O ₃ , TiC, TiN,
A composite sintered body for tools, characterized in that it is a hard sintered body made of compounds such as SiC, Si ₃ N _4, etc., and metals such as Al, Cu, and Ni. 3. The composite sintered body for tools according to claim 1, wherein the intermediate bonding layer further contains Al and/or Si in an amount of 0.1% by weight to 50% by weight. Concretion. 4 In the composite sintered body according to claim 1, when M is a metal of groups 4a and 5a of the periodic table in the intermediate bonding layer, x of the nitride represented by MNx is
A composite sintered body for tools, characterized by being a nitride of 0.5 or more and 0.95 or less. 5. In the sintered body according to claim 1, 2, 3 or 4, the nitride of the intermediate bonding layer is TiNx.
A composite sintered body for tools, characterized by: 6 A type of nitride, a mixture of these, or a mutual solid solution of transition metals of Groups 4a and 5a of the periodic table is applied to a cermet base material in which molybdenum-based (MoW) C-based carbide crystals are bonded with iron group metals. A powder as an intermediate bonding layer consisting mainly of a compound or containing less than 70% by volume of high-pressure phase boron nitride is molded or pre-coated on the cermet base material. Then, an intermediate bonding layer is provided, and on this, a hard sintered body-forming powder or a molded body containing high-pressure phase boron nitride having a composition different from that of the intermediate bonding layer at 20% by volume or more and 95% by volume or less is provided. After mounting, the whole is hot-pressed under ultra-high pressure and high temperature to sinter the hard layer containing high-pressure phase boron nitride and the intermediate bonding layer, and further bond the hard layer, intermediate bonding layer, and cermet base material. A method for manufacturing a composite sintered body for a tool, the method comprising joining the composite sintered body.