JP2505789B2 - High hardness sintered body tool - Google Patents

Description

TECHNICAL FIELD The present invention relates to a high hardness sintered body tool obtained by bonding a cubic boron nitride sintered body layer to a hard sintered alloy substrate.

[Prior Art] Cubic boron nitride (hereinafter abbreviated as cBN) has a high hardness,
Because of its excellent chemical stability and heat resistance, and its low reactivity with iron group metals at high temperatures, its sintered body is expected as a cutting tool material. In recent years, this cBN
A high-hardness sintered body obtained by sintering is developed and put into practical use. Usually, in these cBN sintered bodies,
Binders made of metal such as Al, Co, TiC, TiN, Al ₂
Ceramics such as carbides such as O ₃ , nitrides or oxides, or mixtures of these metals and ceramics are used.

In addition to the above-mentioned conventional cBN sintered body, a cBN sintered body containing almost no binder is known. Since this is a cBN single-phase sintered body, it has higher hardness than conventional sintered bodies containing a binder and is excellent in wear resistance, and it is expected to obtain a high-performance cutting tool. can do. As a method for producing this kind of cBN sintered body, for example, Material Research Bulletin (Mat.Res.Bull): Vol. 7, No. 999
As shown in page (1972), a method is known in which low crystallinity hexaborate-type boron nitride (hBN) is used as a starting material, and it is converted into cBN by a direct conversion method and simultaneously sintered. ing.

Other preferable methods include, for example, Japanese Examined Patent Publication No. 59-5.
There are methods disclosed in Japanese Patent No. 547 and Japanese Patent Laid-Open No. 59-57967. This is a method in which a small amount of an alkali metal or alkaline earth metal boronitride is added to hBN powder or a sintered body, and this is pressurized / heat-treated under the thermodynamically stable condition of cBN. . According to these methods, it is possible to obtain a strong sintered body containing only fine cBN containing almost no impurities.

By the way, when such a sintered body composed only of cBN is used as a cutting tool, how to bond the sintered body and a base body (particularly a base body made of cemented carbide) becomes a problem. In the case of the cBN sintered body containing the above-mentioned binder, a metal such as Al, Co or TiN, TiC contained as the binder is used.
Etc. also effectively act on the bonding with the substrate. However, in the case of a cBN single-phase sintered body that does not contain such a binder, it cannot be directly bonded to the substrate as it is.

Therefore, as disclosed in JP-A-60-263602, a method of using Mo as an intermediate bonding phase is known.
This is a method of super high pressure / high temperature treatment of a raw material for producing a cBN sintered body not containing a binder and a hard sintered alloy substrate with a Mo plate interposed. Below, the sintered cBN sintered body, Mo, and Mo and the substrate are reacted and joined.

[Problems to be Solved by the Invention] However, even if the MoN plate is used as an intermediate bonding phase to bond the cBN sintered body containing no binder to the substrate, the bonding force between the two is not sufficient. . Therefore, when used as a cutting tool, the cBN sintered body and the Mo plate or the Mo plate and the base may be separated during cutting. It is considered that this is because the reaction between Mo and the cBN sintered body and the substrate under ultrahigh pressure and high temperature was not enough to give sufficient bonding strength.

Therefore, the present invention is to provide a high hardness sintered body tool in which a cBN sintered body substantially consisting of cubic boron nitride and a substrate are firmly joined together.

[Means for Solving the Problems] The high hardness sintered body tool of the present invention comprises a cubic boron nitride sintered body layer substantially composed of cubic boron nitride, and this cubic boron nitride sintered body layer. A hard sintered alloy base body bonded to
A cubic boron nitride sintered body layer and a bonding layer disposed between the hard sintered alloy base body and the hard sintered alloy base body are provided. This bonding layer consists of a Mo layer and a TiN layer or T layers arranged on both sides of the Mo layer.
a mixture layer containing 10% by volume or more of iN and the rest being cubic boron nitride.

The drawing is a sectional view of the high hardness sintered body tool of the present invention described above. C consisting essentially of cBN without binder
The BN sintered body 1 and the hard sintered alloy substrate 2 are joined together via the joining layer 3. The bonding layer 3 has a Mo plate 4 and a TiN layer or a mixture layer 5 of TiN and cBN formed on both sides of the Mo plate. The TiN layer or the mixture layer composed of TiN and cBN is formed for joining the Mo plate 4 and the cBN sintered body 1 and the Mo plate and the hard sintered alloy base body 2, respectively.

The cBN sintered body layer used in the present invention consists essentially of cBN, that is, a cBN single-phase cBN sintered body containing no binder.

Further, the TiN layer or the mixture layer is for joining the Mo plate and the cBN sintered body layer and the hard sintered alloy substrate, when the mixture layer is used, the proportion of cBN is 9% by volume.
It should not exceed 0%. 90% by volume of cBN
If it exceeds, the strength will decrease. Further, preferably, the bonding strength can be further increased by using a mixture layer formed by mixing 20 to 80% by volume of cBN as compared with a layer formed of only TiN.

As the method for forming the TiN layer or the mixture layer, the powder-like or embossed state is applied on the hard sintered alloy substrate or on the surface of the Mo plate, or by the PVD or CVD method. It is possible to use a method of forming a thin film by the above method. When powdered TiN layer or mixture layer is used, TiN and / or cBN particle size is 5
It is preferable to use fine powder having a particle size of not more than μm, preferably about 1 μm. This is because when a coarse TiN and / or cBN grain size of 5 μm or more is used, the structure of the bonding layer becomes non-uniform and the strength tends to decrease.

The thickness of the TiN layer or the mixture layer is 0.001 to 1 m.
m is preferred. This is because if it is less than 0.001 mm, sufficient bonding strength cannot be obtained. On the other hand, although it depends on the purpose of use, the thickness does not have to exceed 1 mm when used as a cutting edge for cutting. Therefore, it should be pointed out that the upper limit value, that is, the value of 1 mm is not critical.

In addition, in the present invention, the Mo plate is not used as a bonding layer, but cB
N Used as a shielding plate to prevent the reaction between the sintered body and the hard alloy substrate. When ultra-high pressure and high temperature sintering is performed without using a Mo plate, metals such as W and Co contained in the hard sintered alloy substrate pass through TiN or the mixture layer and react with cBN. As a result, substances like W ₂ Co ₂₁ B ₆
A large amount is generated in the N sintered body, which adversely affects the strength and wear resistance of the cBN sintered body.

In addition to Mo plate as a shielding plate, Ti, Z that is stable under high temperature and high pressure
It is also possible to use r, Ta or the like. However, Ti
Considering the wettability with the N layer, it is necessary to use a Mo plate. The Mo plate preferably has a thickness of about 0.01 to 0.5 mm. This is because if it is less than 0.01 mm, it is likely to be broken during ultra-high pressure application, and if it exceeds 0.5 mm, the strain stress due to the difference between the thermal expansion coefficient of Mo and TiN or cBN becomes large, which causes peeling.

An example of the method for manufacturing the high hardness sintered body tool of the present invention will be described. First, 0.01 to 1 mm TiN on the surface of the hard sintered alloy substrate.
A layer or a layer composed of a mixture of TiN and cBN is formed. Next, a Mo plate of 0.01 to 0.5 mm is placed on it. Furthermore, M
o A 0.001 to 1 mm TiN layer or a layer made of a mixture of TiN and cBN is formed on a plate, and the cBN sintered body raw material is placed thereon.
The sample body thus prepared is placed in the reaction container,
It is exposed to ultra high pressure and high temperature to form a cBN sintered body, and at the same time, join the cBN sintered body and the hard sintered alloy substrate.

Under ultra-high pressure and high temperature, TiN reacts with cBN, Mo and hard sintered alloy, and firmly bonds with each other. As a result, cB
It is possible to obtain a high hardness sintered body tool for cutting in which the N sintered body is extremely strongly bonded to the hard sintered alloy substrate.

[Operation] In the high-hardness sintered body tool of the present invention, the cBN sintered body layer that does not contain a binder and can be regarded as substantially consisting of cBN is bonded to the hard sintered alloy substrate by the bonding layer described above. It In this bonding layer, layers made of TiN or a mixture of TiN and cBN are formed on both sides of the Mo plate. As will be supported from the examples described below, this TiN layer or the above mixture layer reacts with the Mo plate, the cBN sintered body layer and the hard sintered alloy, and the Mo plate and the cBN sintered body layer, and the Mo plate and the hard sintered body. Firmly joins the sintered alloy substrate. Moreover, the Mo plate is also firmly bonded, and the Mo plate serves to shield the reaction between the cBN sintered body layer and the hard sintered alloy base under the sintering conditions.

[Effects of the Invention] Therefore, according to the present invention, the cBN sintered body substantially consisting of only cBN is firmly bonded to the hard sintered alloy substrate, and high hardness baking that does not cause problems such as peeling during use. A binding tool can be obtained.

[Description of Examples] Example 1 As a raw material of cBN sintered body containing no binder, oxygen content
A high-purity hBN compact of 0.03% by weight or less was used. This hBN compact was processed into a disk shape with a diameter of 30 mm and a thickness of 2 mm.
The processed hBN plate was embedded in magnesium nitride powder and treated in nitrogen gas at 1165 ° C. for 12 hours to uniformly diffuse and carry about 1.0 mol% of magnesium bonitride in the hBN compact.

TiN powder having an average particle size of 1 μm was mixed with an organic solvent containing ethyl cellulose to form a slurry. This TiN slurry is applied to both sides of a Mo disk with a diameter of 30 mm and a thickness of 0.1 mm,
A TiN layer having a thickness of about 0.02 mm was formed. Above the Mo disk, the above-mentioned hBN compact was placed underneath and the WC-C with a diameter of 30 mm and thickness of 4 mm
o Cemented carbide discs were placed and placed in a reaction vessel for high pressure / high temperature processing.

The reaction vessel was set in the ultrahigh pressure generator, and the pressure was set to 5.
Pressurized to 5 GPa and then heated to 1400 ° C. 30 in this state
Hold for a minute, after the conversion reaction from hBN to cBN and the sintering reaction of cBN are sufficiently performed, lower the temperature and remove the pressure,
After that, the sample was taken out.

The raw material part of the hBN compact was all converted to cBN and was strongly sintered. The cBN sintered body and the TiN layer reacted at the boundary portion, and were extremely strongly bonded. The TiN layer also reacted with the Mo plate and the cemented carbide substrate, and they were bonded with considerably high strength.

The integrated body of the cBN sintered body and the cemented carbide substrate thus obtained was cut by a laser to produce a cutting tip. The cutting tip was brazed to a steel support to prepare a cutting tool. With this cutting tool, gray cast iron (Fc
25 types), cutting speed 500m / min, depth of cut 0.5mm, feed 0.1mm / revolution, dry cutting, cB despite intermittent cutting
N could be cut without peeling of the sintered body.

Example 2 Instead of the TiN powder used in Example 1, an average particle size of 1 μm
Of TiN powder and cBN powder having an average particle size of 3 μm were mixed in a volume ratio of 40% and 60%, respectively,
In the same manner as in the other Example 1, an integrated body composed of the cBN sintered body and the cemented carbide substrate was obtained. The bonding of each phase was strong, and as a result of the same cutting test as in Example 1, no defects such as peeling were observed.

Example 3 A TiN layer having a thickness of 0.003 mm was formed on both surfaces of a Mo disk having a diameter of 30 mm and a thickness of 0.1 mm by the CVD method. Above this Mo disk,
An hBN compact containing about 1.0 mol% of magnesium boronitride was placed, and a WC-Co cemented carbide was placed below. Other structures were the same as in Example 1 to obtain an integrated body composed of a cBN sintered body and a cemented carbide substrate. The bonding of each layer was strong, and
When a cutting test similar to the above was conducted, no problem such as peeling occurred.

[Brief description of drawings]

The accompanying drawings are sectional views of the high hardness sintered body tool of the present invention. 1 is a sintered body layer which is substantially composed only of cBN, 2 is a substrate made of a hard sintered alloy, 3 is a bonding layer, 4 is a Mo plate, and 5 is TiN
A layer or a mixture layer of TiN and cBN is shown.

Claims (3)

(57) [Claims] 1. A cubic boron nitride sintered body layer consisting essentially of cubic boron nitride, a hard sintered alloy substrate to which the cubic boron nitride sintered body layer is bonded, and the cubic boron nitride sintered body. It comprises a sintered body layer and a bonding layer arranged between the hard sintered alloy substrate and the hard sintered alloy substrate for bonding, wherein the bonding layer is a Mo layer and TiN arranged on both sides of the Mo layer.
A high hardness sintered body tool having a layer or a mixture layer containing 10% by volume or more of TiN with the balance being cubic boron nitride. 2. The high hardness sintered body tool according to claim 1, wherein the Mo layer has a thickness in the range of 0.01 to 0.5 mm. 3. The thickness of the TiN layer or the mixture layer is 0.0
The high hardness sintered body tool according to claim 1 or 2, which is in the range of 01 to 1 mm.