JPH03243742A - TiB↓2-Co based cemented carbide, cutting tools, and manufacturing method of cemented carbide - Google Patents

Abstract

PURPOSE:To manufacture a TiB2-Co series sintered hard alloy having high density and high deflective strength and having a structure with uniform grain size by bonding many TiB2 grains with a bonding layer contg. a Co simple substance or Co. CONSTITUTION:Grains contg. a Co simple substance or Co are mixed with TiB2 grains, and this mixed grains are subjected to pressure sintering in the temp. range of 1,200 to 1,800 deg.C. At this time, the content of Co is regulated to 2 to 30 vol. to the total volume of the TiB2 grains and the bonding layer. In this way, the TiB2-Co series sintered hard alloy excellent in wear resistance and thermal shock resistance can be obtd. by short time sintering and is useful as the material for cutting tools.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention is directed to TiB, which is composed mainly of TiBx particles and bound by Co alone or a bonding layer containing Co.
, -Co-based cemented carbide, cutting tool, and manufacturing method.

"Prior Art" TiB and ceramics are known as ceramics with excellent heat resistance, wear resistance, and oxidation resistance.

However, since this ceramic has a high melting point, it is said to have poor sintering properties, making it extremely difficult to obtain a high-density sintered body.

Conventionally, TiB* ceramic particles were mixed with Ni-Zr or NiB particles as an auxiliary agent and binder, and this mixed powder was sintered under normal pressure at 2000°C for about an hour. The following literature reports that a sintered body could be produced.

“Fabrication or T itaniu
m D 1borida Cosp-osites
K astuhiro Nishiyama
(Coaposites' 89: Roc
ant advances in Japan
and TheU n1ted States
”).

"Problem to be Solved by the Invention" By the way, the results of measuring the bending strength of the TiB1 sintered body produced by the above method are described in the above document, and the measurement results are as shown in Figure 1O. It has become.

According to the above literature, the relative density of the TiBz sintered body is 100
%, as shown in Figure 10, the bending strength varies widely, and the data is unreliable, making it unreliable as a mechanical or structural material. There is a problem that the bending strength itself is insufficient as a mechanical or structural material.

In addition, the sintering temperature when producing the TiB sintered body is 2000°C, which is an extremely high temperature, and the sintering time is as long as 1 hour. There is a problem in that abnormal grain growth occurs and the structure becomes non-uniform, resulting in a decrease in strength and an increase in variation. This abnormal grain growth can be suppressed by shortening the sintering time or lowering the sintering temperature, but in the case of pressureless sintering, sintering must be performed under the above conditions. The current situation is that it cannot be manufactured.

The present invention was made to solve the above problems, and has a structure with high density, high bending strength, and uniform grain size, and has little variation in properties, so it is reliable as a mechanical material or a structural material. The purpose of the present invention is to provide a TiB, -Co-based cemented carbide and a cutting tool that have high heat resistance and wear resistance, and are suitable as cutting materials, and to provide a method for producing the cemented carbide. .

"Means for solving the problem" In order to solve the problem, the invention stated in claim 1 has the following features:
It is formed by bonding a large number of T iB x particles with Co alone or with a bonding layer containing CO.

In order to solve the above problem, the invention described in claim 2 has the following features:
The cutting tool is made of a TiBt-Co based cemented carbide, which is made by bonding a large number of TiB particles with Co alone or with a bonding layer containing CO.

In order to solve the above problem, the invention described in claim 3 has the following features:
It is made by bonding a large number of TiB particles with Co alone or a bonding layer containing CO, and the Co content is 2 to 30% by volume based on the total volume of the TiB particles and the bonding layer. .

In order to solve the above problem, the invention described in claim 4 has the following features:
Mixed particles obtained by mixing Co alone or Co-containing particles with TiB particles are sintered under pressure at a temperature of 1200 to 1800°C.

"Operation" Co alone or a bonding layer containing Co becomes a liquid phase at about 1200°C between 'I'iB* particles, and at that time, TiB,
Even when sintered at a lower temperature than conventional methods, the bonding layer that has become a liquid layer sufficiently surrounds the particles with T i B , and the liquid phase sintering allows for uniform sintering. A bonding layer is formed to bond the T i B particles. In addition, during pressure sintering, Co alone or a bond layer containing Co becomes a liquid layer, and the TiB* particles are surrounded by the liquid layer.
Since the B1 particles are in the same state as when they are isostatically pressurized by the liquid layer, the TiB* particles grow in the liquid layer during grain growth and change in particle size during sintering. T iB that is rearranged and uniformly distributed and has a uniform structure after sintering,
-Co-based sintered body is produced.

The present invention will be explained in more detail below.

FIG. 1 shows an enlarged view of the structure of an example of the TiB, -Co-based sintered body of the present invention. Therefore, in FIG. 1, symbol A indicates TiB* particles, symbol B indicates a bonding layer, many T
i B The particles A are surrounded by a bonding layer B and are bonded to each other. The bonding layer B includes Co single layer, Co+Mo layer, Co+WC layer, Co+
It can be appropriately selected from a Ni layer or a mixed layer thereof, but is not limited to these layers, and various bonding layers (binder layers) containing Co can be used. .

Next, an example of a method for manufacturing the TiB, -Co-based sintered body will be described.

To produce a TiB, -Co-based sintered body with the above structure,
For example, TiB2 particles such as TiBx powder and Co particles such as Co powder having the same particle size are prepared, and then these are mixed at a predetermined ratio. When mixing these particles, T
iB, for the total volume of particles and Co particles, C
Mix so that the o content is in the range of 2 to 30% by volume. If the Co content is less than 2% by volume or more than 30% by volume, the strength of the TiBt-Co sintered body obtained will decrease, which is not preferable. Further, it is preferable that the particle size of each particle to be mixed is as small as possible and uniform in particle size, as in the case of manufacturing ordinary cemented carbide by a powder method.

Next, the mixed particles mixed as described above are heated and sintered while being pressurized.

FIG. 2 shows an example of an apparatus for heating the mixed particles while pressurizing them, and the apparatus in this example is a type of hot press apparatus. l indicates a heater, and a press device consisting of a push rod 2, a mold material 3, a spacer 4, and a lower stand 5 is provided inside the heater l, and a sample 6 placed on the lower stand 5 is pressurized with the push rod 2. At the same time, the heater 1 can be used to heat to a desired temperature. The entire pressurizing and heating device is enclosed in a vacuum container, and the degree of vacuum inside this vacuum container is set to 1.
It can be set to about 3XlO'□'Pa.

To sinter the mixed powder using the apparatus of this example,
The mixed particles are placed on the lower stand 5, and the whole is evacuated, and the mixed powder is pressed with a pressure of about 60 MPa using the push rod 2, and heated to 1200 to 1800°C to sinter. It is preferable that the sintering time be short, but in order to achieve sufficient sintering,
In addition, the heating time is set to about 30 minutes in order to avoid abnormal growth of crystal grains.

By sintering as described above, the 00 layer, which has a melting point lower than that of the T i B x particles A, selectively becomes a liquid layer. This Co
The liquid layer has excellent wettability for TiB* particles A, so
The liquid layer of co sufficiently surrounds TiB*particle A, TiB, and -like C around particle A.

A liquid layer is formed. And T iB , particle A is
Since they are completely surrounded by the Co liquid layer and are pressurized as a whole, the TiB and particles A receive the same effect as when they are isostatically pressurized from the outside using hydrostatic pressure. Therefore, during sintering, TiB and particles A are rearranged while the grain growth and grain size of TiB*particles A are changed, resulting in a TiBt-Co sintered body with a uniform structure. is obtained.

Also, the aforementioned T iB! -Ti in the Co sintered body
B! Co or G has higher fracture toughness than particle A.

Since TiB and particles A are bonded in a bonding layer B containing
The crack propagation speed is much slower than when TiB* alone is sintered, resulting in improved fracture toughness. Therefore, TiB obtained according to the present invention.

The CO-based sintered body is a conventional ceramic cutting material (PIOIT).
It has better wear resistance than iN, TiC, Al*os).

The TiB, -Co sintered body manufactured as described above has a bending strength of about 800 to 1000 MPa and a hardness of 30
It has excellent mechanical properties of 00 to 3500 Hv, and has excellent abrasion resistance and thermal shock resistance.

Therefore, cutting tools, blades, shafts, etc. can be manufactured using the T iB *-G o based sintered body of the present invention.

Furthermore, as another application example of TjB x -G O-based cemented carbide, it can also be applied as NH produced by carrying out PVD method (physical vapor deposition method) and CVD method (chemical vapor deposition method). can. In this case, by using a TiBxCo target with an appropriate composition and forming a film using the method described above, a film of TiB! -Co sintered body can be obtained.

Furthermore, TiB4. Since s is known to exhibit superconductivity, the method of the present invention can be applied to generate TiB+, s by controlling the amount of B, and can also be developed into a technology for developing superconducting materials.

In addition, in the above manufacturing method, the sintering temperature is 1200 to 18
Since the sintering temperature can be lowered to 00°C, the sintering temperature can be lower than that of conventional methods, and the sintering time can also be shorter than the conventional one hour.

Therefore, the crystal grain size of the obtained sintered body can be made finer.

By the way, in the above example, a hot press method is used as the sintering method, but in order to reduce the sintering temperature and sintering time, a sintering method such as electric sintering or HIP may be used. May be applied.

"Example" A mixed powder is formed by mixing T i B x powder and CO powder, and this mixed powder is inserted into the pressure heating device shown in FIG. 2, and the degree of vacuum is set to I, 3 x 10-'. The pressure was set at 60 MPa, the sintering temperature was set at 1200 to 1800°C, the sintering time was set at 30 minutes, and the temperature increase rate was set at 15°C/min, and the Co content was determined as shown in Table 1 below. Set and hot press T iB.

-Coo sintered body was manufactured.

Figure 3 shows the relationship between the Vickers hardness measurement results and the Co content for the TiB1Co sintered body produced as described above and the TiB* sintered body produced by the conventional method. FIG. 4 shows the relationship between the measurement results of the bending strength and the Co content.

From the results shown in Figures 3 and 4, the lower limit of Co content is 2.
It has been found that the upper limit of the Co content is preferably 30% by volume.

Moreover, the TiB, -Coo sintered body of the present invention has a bending strength of approximately 800 to 1000 MPa and a hardness of 3000 to 350 MPa.
It has become clear that it exhibits excellent mechanical properties of 0Hv.

Further, FIGS. 5 to 7 show the TiBz-Co of the present invention.
Figure 8 shows the results of measuring the room temperature strength of the sintered body after applying thermal shock at various temperatures. The results of measuring the room temperature strength after applying thermal shock at various temperatures to the sintered body are shown.

From these results, TiBy-Coo sintered body, conventional T
iB! It has become clear that the high-temperature strength is also superior to that of sintered bodies.

FIG. 9 shows a conventional TiB sintered body and a TiB of the present invention.
Forming tools from 1Co sintered bodies and various other materials,
The cutting test results are shown when cutting is performed using each tool. In FIG. 9, the data indicated by ◯, square, and ∆ indicate the cutting test results of the tool made of the TiBt-Co sintered body of the present invention.

From the results shown in FIG. 9, it can be seen that T iB x-G o of the present invention
It has been revealed that the sintered body has excellent wear resistance and thermal shock resistance, and exhibits excellent performance as a cutting tool.

"Effect of the invention" As explained above, according to the invention stated in claim 1,
It is possible to provide a TiB*-Co-based cemented carbide having high transverse strength and hardness, excellent mechanical properties, and excellent wear resistance and thermal shock resistance.

According to the invention described in claim 2, it is possible to provide an excellent cutting tool that has high bending strength and hardness, has excellent mechanical properties, and has excellent wear resistance and thermal shock resistance.

According to the invention described in claim 3, since the Co content is limited to a specific range, the bending strength and hardness are even higher,
T iB with exceptional abrasion resistance and thermal shock resistance
, -G o-based cemented carbide can be provided.

According to the invention described in claim 4, the sintering temperature can be lowered than before, and the sintering time can be shortened than before, and abnormal growth of crystal grains during sintering can be suppressed, so that fine grains can be reduced. T iB has uniform crystal grains, high strength, and excellent wear resistance and thermal shock resistance! -CO based cemented carbide can be manufactured.

Further, since the sintering temperature can be lowered than in the past, there is less burden on the sintering equipment, and the sintering time can be shortened, so the manufacturing time can also be shortened.

[Brief Description of the Drawings] Figure 1 shows the T iB! of the present invention. Figure 2 is an enlarged view of the structure of the alloy, Figure 2 is a cross-sectional view showing an example of the apparatus used to carry out the method of the present invention, and Figure 3 is a diagram showing the Co content and Figure 4 is a diagram showing the relationship between Vickers hardness, Figure 4 is a diagram showing the relationship between grain size and bending strength, and Co content in cemented carbide, and Figure 5 is a diagram showing the relationship between Co content in cemented carbide.
% containing T iB , -C. Figure 6 is a diagram showing the relationship between heating temperature and room temperature strength in T iB -C0 series cemented carbide containing 6% Co. Figure 7 is a diagram showing the relationship between heating temperature and room temperature strength in a TiBt-Co cemented carbide containing 10% Co, and Figure 8 is a diagram showing the relationship between heating temperature and room temperature strength in a conventional T r By sintered body. FIG. 9 is a diagram showing cutting test results for the alloy of the present invention and other alloys and ceramics, and FIG. 10 is a diagram showing conventional T iB to which various binders are added. FIG. 3 is a diagram showing the strength of a sintered body. A: TiBy particles, B: bonding layer, ■: heater, 2: push rod, 3: mold material, 4: spacer, 5
...lower stand, 6...sample.

Claims (4)

[Claims] (1) TiB characterized by being formed by bonding a large number of TiB_2 particles with Co alone or a bonding layer containing Co.
_2-Co-based cemented carbide. (2) A cutting tool made of TiB_2-Co based cemented carbide, which is made by bonding a large number of TiB_2 particles with Co alone or a bonding layer containing Co. (3) A large number of TiB_2 particles are bonded by Co alone or a bonding layer containing Co, and the Co content is 2 to 30% by volume based on the total volume of the TiB_2 particles and bonding layer. TiB_2-Co based cemented carbide. (4) A method for producing a TiB_2-Co cemented carbide, which comprises pressurizing and sintering mixed particles obtained by mixing TiB_2 particles with Co alone or particles containing Co at a temperature of 1200 to 1800°C.