JPH1179839A - Tungsten carbide-based cemented carbide material and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a tungsten carbide-based cemented carbide material comprising a WC-, a W2 C- or a WC-W2 C-based sintered compact and to provide a method for producing the tungsten carbide sintered compact and the tungsten carbide-based cemented carbide material. SOLUTION: This tungsten carbide-based cemented carbide material has a composition substantially composed of 100-0 mol.% W2 C and 0-100 mol.% WC and further has >=14 GPa measured value of Vickers hardness under 10 N load and >=5 MPa.m<1/2> value of toughness. The tungsten carbide-based cemented carbide material is produced by mixing two kinds of W, C, WC and W2 C at a predetermined mixing ratio, holding the resultant mixture within a predetermined temperature range for a predetermined time in a vacuum or an inert gas using a discharge plasma system and carrying out the reaction and sintering. A hot isostatic pressing(HIP) treatment of the obtained sintered compact may be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tungsten (W) -carbon (C) compound, an ultra-hard material using the same, and a method for producing the same. In the field, the present invention relates to a novel tungsten carbide super-hard material and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, mono-tungsten monocarbide (WC) and di-tungsten monocarbide (W ₂ C) have been known as tungsten (W) -carbon (C) compounds. This WC connects W and C,
It is produced by a carbonization reaction in a vacuum or H ₂ at a temperature of 1300 to 2000 ° C.

[0003] However, a raw material used as fine WC powder contains W ₂ C as an impurity.

On the other hand, W ₂ C is produced by putting W and C in a graphite crucible at an atomic equivalent ratio of 2: 1 and heating to 1600 ° C. The generated W ₂ C contains WC as an impurity.

[0005] Of the two tungsten carbide raw materials mentioned above, only WC is used as the raw material of the super-hard material, and W ₂ C was considered to be an unfavorable material.

Conventionally, a super-hard material is synthesized from WC by adding Co. That is, 2 to 25% of Co is added to fine WC powder and fired at 1300 to 1500 ° C. in a vacuum or in an impurity gas atmosphere to produce a dense WC-Co-based ultra-hard material.
Hot isostatic sintering (HIP) to eliminate defects such as holes
It is being applied to

[0007]

SUMMARY OF THE INVENTION Conventional WC and W
The WC synthesized by the production method of ₂ C, W ₂ C is present as an impurity, while the W ₂ C is present WC is as an impurity.

In the conventional WC sintering method, it is difficult to obtain a dense sintered body unless Co is added. For these two reasons, it has been an important task to investigate the properties of pure WC and W ₂ C sintered bodies.

Further, as described above, when sintering by adding Co, if the carbon content is less than the WC composition, that is, if W ₂ C is contained, it reacts with Co to form a brittle η phase, It makes WC tougher. Co is WC and β
It is said that it forms a phase and exists at the grain boundary, promotes sintering of the WC-Co system, and increases toughness. But this β
Since the phase is soft, the hardness of the WC-Co based sintered body tends to decrease. For example, the sintered body to which 5% Co is added has a Vickers hardness of about 15 GPa, which is smaller than that of the alumina, Si ₃ N ₄ and SiC sintered bodies. On the other hand, in the toughness value, 12 GPa · m
^1/2 is much larger than others.

Generally, it is preferable that the hardness and toughness of the super-hard material are large. However, since WC is difficult to sinter, it was difficult to synthesize a sintered body of only WC excluding Co, and a decrease in hardness due to the addition of Co was not avoided.

[0011] In the case of a WC-Co super-hard material, WC
The larger the particle size, the lower the hardness and the lower the bending strength. Conversely, when the WC grains are made finer, the hardness increases and the transverse rupture strength also increases. However, since the fine WC contains W ₂ C, it is unavoidable that an η phase is generated in the WC-Co-based ultra-hard material, and one of the problems is to prevent a decrease in toughness due to the η phase.

Therefore, a general technical problem of the present invention is to
An object of the present invention is to provide a tungsten carbide super-hard material having high hardness and toughness, and a method for manufacturing the same.

A special technical problem of the present invention is that W
An object of the present invention is to provide a tungsten carbide-based super-hard material made of a C, W ₂ C, or WC-W ₂ C-based sintered body, and a method for producing the same.

[0014]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have conducted intensive research and have found that using a discharge plasma system (manufactured and sold by Sumitomo Coal Mining Co., Ltd. and Sodick Co., Ltd.). Discovered that pure WC and W ₂ C sintered bodies could be synthesized using W and C as raw materials. This discharge plasma system is one type of hot press directly energized. Further, in this system, the same direct current pulse energization system as that of the electric discharge machine is adopted as a power supply for energization. Specifically, when a pulsed direct current is applied to a graphite mold filled with powder, a discharge plasma system is generated between the powders, and a phenomenon different from chemical reaction or sintering caused only by ordinary heat occurs. Can be expected. Therefore, with respect to WC and W ₂ C, when a discharge plasma system is used, a pure compound is obtained due to the effect of the discharge plasma.

Further, the present inventors have found that a dense WC sintered body and a W ₂ C sintered body can be synthesized from W powder and C powder without using Co by using a discharge plasma system. I started. The progress of densification due to no Co addition is also due to the discharge plasma effect.

Further, the present inventors set the ratio of W and C to W
Is changed from C to W ₂ C, it was found that a dense WC-W ₂ C sintered between when reacted and sintered using spark plasma system from WC to W ₂ C can be synthesized.

[0017] Commercially available WC powder has a W ₂ C content of 0.01 to 0.0.
Although the content is 5 mol%, a dense sintered body can be obtained by using a discharge plasma system as it is. Furthermore, if C is added to this commercially available WC powder and sintered by a discharge plasma system in order to eliminate W ₂ C contained as an impurity, a dense and pure WC sintered body can be obtained.

That is, according to the present invention, 100 to 0 mol%
With a composition consisting essentially of W ₂ C and 0-100 mol% WC, and having a Vickers hardness measurement value of 1 at a load of 10 N.
A tungsten carbide super-hard material having a strength of 4 GPa or more and a toughness value of 5 MPa · m ^1/2 or more is obtained.

Further, according to the present invention, an atomic equivalent ratio of 2:
W is mixed with C at 0.9, and 1400-200 in a vacuum or in an inert gas using a discharge plasma system.
A method for producing a tungsten carbide sintered body characterized by obtaining a W ₂ C sintered body by reacting in a temperature range of 0 ° C.

According to the present invention, the atomic equivalent ratio is 1: 1.
W and C are mixed by using a discharge plasma system.
A method for producing a tungsten carbide sintered body characterized in that it is maintained in a temperature range of 1400 to 2000 ° C. for 1 to 120 minutes in a vacuum or an inert gas and reacted to obtain a WC sintered body.

According to the present invention, in any of the above methods for producing a tungsten carbide sintered body, the sintered body is further subjected to a pressure of 5 MPa using a hot isostatic sintering machine (HIP).
There is provided a process for producing a tungsten carbide-based ultra-hard material characterized by having a step of treating at a temperature of 1300 to 2000 ° C. for 10 to 200 minutes at a temperature of 1 to 200 MPa and substantially eliminating pores.

According to the present invention, the atomic equivalent ratio is 1:
(0.45-1), C and W are mixed, and the mixture is mixed in a vacuum or in an inert gas using a discharge plasma system.
A method for producing a tungsten carbide super hard material characterized by obtaining a dense WC-W ₂ C super hard material by reacting and sintering at a temperature range of 0 to 2000 ° C. for 1 to 120 minutes to obtain a dense WC-W ₂ C super hard material. .

According to the present invention, the mixed powder composed of WC and W ₂ C is maintained in a temperature range of 1400 to 2000 ° C. for 1 to 120 minutes in a vacuum or in an inert gas using a discharge plasma system. And sintered, dense WC-W ₂ C
A method for producing a tungsten carbide-based super-hard material, characterized in that a super-hard material is obtained.

According to the present invention, the WC powder is added
~ 0.05 mol% of C is added, and using a discharge plasma system, in vacuum or in an inert gas,
Sintering at a temperature range of 2000 ° C for 1 to 120 minutes,
A method for producing a tungsten carbide-based super-hard material characterized by obtaining a dense WC-based super-hard material is obtained.

Further, according to the present invention, in any one of the above-mentioned methods for producing a tungsten carbide-based super-hard material, the super-hard material is further subjected to hot isostatic pressing (HIP).
At a pressure of 5 MPa to 200 MPa, a temperature of 1300
A process for producing a tungsten carbide-based ultra-hard material, characterized by having a step of treating at 2,000 ° C. for 10 to 200 minutes and substantially eliminating pores.

[0026]

Embodiments of the present invention will be described below.

First, W ₂ C was synthesized from a W powder and a C powder using a discharge plasma system. In the phase diagram of the WC system, the composition of W ₂ C is not 2 atomic weights of W and 1 atomic weight of C, but has a composition of 0.9 C with respect to 2 W. The powder was mixed and a dense sintered body composed of pure W ₂ C was synthesized using a discharge plasma system.

Similarly, 1 atomic equivalent of W powder and 1 atomic equivalent of C powder were mixed to synthesize a dense sintered body composed of pure WC.

Table 1 below shows the measurement results of the toughness and Vickers hardness of the two sintered bodies obtained by the above two methods.

As shown in Table 1 below, the hardness of the W ₂ C sintered body is almost equal to that of the WC-Co super hard material.
₂ C sintered body was also found that that can be used as a super-hard material.

The hardness of the WC sintered body is at least 1.5 times higher than that of the WC-Co system, and the toughness is slightly lower than that of the WC-Co system. Other ceramics have such a high toughness other than zirconia. Nothing had.

The inventor of the present invention has conducted various studies on the reason why the WC sintered body and the W ₂ C sintered body have high toughness. As a result, WC and W ₂ C can be plastically deformed at around room temperature, and stress is exerted. When they did, they discovered that the dislocations moved like metal, and that slip deformation was possible. That is, as shown in Table 1 below, a WC sintered body having high toughness can be synthesized without adding Co to WC.

The hardness of W ₂ C is 30 GP.
a, but as shown in Table 1 below,
Because it is less than half and its toughness is larger than WC,
This clearly shows that the compound is closer to a metal than WC and easily plastically deformed. As a result, the hardness was 14 to 24 GPa and the toughness was 1 by changing the mixing ratio of W powder and C powder as raw materials from 2 W + 0.9 C to W + C.
The synthesis of an ultra-hard material with a change of 0 to 6 GPam ^1/2 has been made possible.

[0034]

[Table 1]

Next, a method of manufacturing a tungsten carbide (WC-W ₂ C) -based ultra-hard material according to an embodiment of the present invention will be described.

The production of the WC-W ₂ C-based ultra-hard material according to the embodiment of the present invention is performed using the following five raw materials 1) to 5).

1) A raw material obtained by mixing 1 atomic equivalent of W and 0.45 atomic equivalent of C 2) A raw material obtained by mixing 1 atomic equivalent of C with respect to 1 atomic equivalent of W 3) A raw material obtained by mixing 1 atomic equivalent of W 4) A commercially available WC raw material 5) A raw material obtained by adding 0.01 to 0.05 mol% of C to a commercially available WC and mixing the above raw material into a graphite mold Packing and installation in a discharge plasma system, and after applying a vacuum or an inert gas atmosphere such as nitrogen or argon, energize and raise the temperature.

Here, good results can be obtained if the temperature for synthesizing and sintering W ₂ C and WC is in the range of 1400 to 2000 ° C. At temperatures below 1400 ° C., the reaction and sintering occur only partially. Also, 20
When the temperature is higher than 00 ° C., the reaction and sintering are completed at a temperature lower than the temperature. Therefore, the grain growth of the sintered body occurs and the strength is reduced. It is. Preferably, a temperature of 1500 to 1900 ° C. gives good results.

The time required to reach the temperature for the reaction and sintering is related to the performance of the discharge plasma system, and usually a range of 3 to 30 minutes is preferable from the viewpoint of performance and economy. The holding time at the temperature for reaction and sintering is
A range of 1 to 120 minutes is good. In less than one minute the reaction and sintering occur only partially. In addition, 120
Holding for more than one minute is because the reaction and sintering are completed after holding for 120 minutes or less, which only promotes the grain growth of the sintered body and lowers the strength, which is not good. Preferably, 3
Good results are obtained in the range of ６０60 minutes.

The reaction and sintering are performed while applying pressure. The range of the applied pressure is suitably from 5 to 200 MPa. If the pressure is 5 MPa or less, the adhesion of the entire graphite mold becomes poor, the electric resistance increases, and the current cannot be supplied.
On the other hand, since there is no graphite mold that can withstand the pressure of 200 MPa, 2
This is because the pressure cannot be increased to 00 MPa or more.

The dense ultra-hard material synthesized by the discharge plasma system hardly contains pores. However, in order to further improve the reliability of the material, a hot isostatic press (HIP) is used. Heat treating the material using is of industrial importance in terms of further reducing pores. The pressure of this HIP processing is 5 to 200 MPa.
Good results can be obtained within the range. If the pressure is 5 MPa or less, the pores cannot be sufficiently removed, and even if the pressure is 200 MPa or more, the effect of removing the pores remains unchanged. It is appropriate that the temperature for the HIP treatment is in the range of 1300 to 2000 ° C. The reason for this is that there is almost no effect of removing pores at 1300 ° C. or less, while there is no change in the treatment at a temperature lower than 2000 ° C. and the effect of removing pores.

The time for the HIP process is set to 10 to 200 hours.
Minutes give good results. The reason is that if the time is less than 10 minutes, the effect of removing pores is too short and the effect of removing pores is not different from the processing of 200 minutes even if the processing is performed for 200 minutes or more.

[0043]

Embodiments of the present invention will be described below.

Example 1 Commercially available WC powder (average particle size,
0.56 μm) was packed in a graphite mold, placed in a discharge plasma system, and evacuated. Electricity was applied while applying a pressure of 39.2 MPa, and the temperature was raised to 1750 ° C. in 20 minutes.
C. for 4 minutes to synthesize a dense WC-W ₂ C-based ultra-hard material. The characteristics are shown in Table 2 below.

[0045]

[Table 2]

(Example 2) Commercially available W used in Example 1
C2 powder was added with 0.02 atomic% of carbon black, mixed, packed into a graphite mold, installed in a discharge plasma system, and replaced with argon gas. While applying a pressure of 19.6 MPa, the temperature was raised to 1640 ° C. in 15 minutes and kept at this temperature for 10 minutes to obtain a WC ultra-hard material. This WC
The properties of the super hard material are shown in Table 3 below.

[0047]

[Table 3]

Example 3 The WC ultra-hard material synthesized in Example 2 was heated to 1900 ° C. in 90 minutes by introducing a hot gas of 100 MPa using a hot isostatic sintering machine (HIP). The temperature was maintained for 30 minutes to complete the heat treatment for removing pores. The properties of this WC superhard material are shown in Table 4 below. Compared to the WC super hard material shown in Table 3 above,
It can be seen that the value of the Young's modulus is slightly increased and the pore is reduced.

[0049]

[Table 4]

(Example 4) Each mixed powder obtained by mixing W powder and carbon black at the ratio shown in Table 5 below was packed in a graphite mold and installed in a discharge plasma system. The system was evacuated, energized and heated to 1800 ° C. in about 20 minutes, held at this temperature for 2 minutes and WC, W ₂ C and WC
The -W ₂ C-based superhard materials were synthesized. The properties are shown in Table 5 below.
It was shown to.

[0051]

[Table 5]

As described above, the super-hard material of the present invention can be used as a cutting tool such as a cutting tool, a drill, a cutter, a reamer and the like. Cold forging die, hot forging die, drawing die, drawing die, hot wire rolling roll, etc. as long cutting blades, various punching and other reversing tools, mechanical seal, drill push, nozzle, Workrest blade, gauge plate, high pressure type, cylinder for synthesis, plunger for synthesis,
Ultra-high pressure type and others, used for impact drilling tools, rotary drilling tools, mechanical drilling tools and others as civil engineering mining tools, and powder molding dies, boring bars, spikes,
It can also be applied to various molds, stamps, and the like.

[0053]

As described above, the present invention can provide a tungsten carbide super-hard material having high hardness and toughness and a method for producing the same.

The present invention also provides a tungsten carbide super-hard material made of a WC, W ₂ C, or WC-W ₂ C sintered body having high hardness and toughness, and a method for producing the same. be able to.

Claims (8)

[Claims] 1. The method according to claim 1, wherein the W ₂ C is from 100 to 0 mol% and the amount is from 0 to 10.
It has a composition consisting essentially of 0 mol% WC and has a load of 10
Vickers hardness measurement value in N is 14 GPa or more,
A tungsten carbide super-hard material having a toughness value of 5 MPa · m ^1/2 or more. 2. Mixing W and C at an atomic equivalence ratio of 2: 0.9, and reacting in a vacuum or an inert gas in a temperature range of 1400 to 2000 ° C. using a discharge plasma system to produce W _2. A method for producing a tungsten carbide sintered body, comprising obtaining a sintered body of C. 3. Mixing W and C at an atomic equivalent ratio of 1: 1;
Using a discharge plasma system in a vacuum or in an inert gas at a temperature in the range of
A method for producing a tungsten carbide sintered body, characterized in that a sintered body of WC is obtained by holding and reacting for one minute. 4. The method for producing a tungsten carbide sintered body according to claim 2, further comprising the step of using a hot isostatic sintering machine (HIP) to apply a pressure of 5 MPa to 200 MPa.
At a temperature of 1300 to 2000 ° C. and 10 to 2
A method for producing a tungsten carbide-based ultra-hard material, comprising a step of treating for 00 minutes and substantially eliminating pores. 5. A mixture of C and W in an atomic equivalence ratio of 1: (0.45-1), and using a discharge plasma system in a vacuum or an inert gas at a temperature of 1400-2000 ° C. Hold for ~ 120 minutes to react and sinter to obtain dense W
A method for producing a tungsten carbide super hard material, characterized by obtaining a C-W ₂ C super hard material. 6. A mixed powder composed of WC and W ₂ C is sintered in a vacuum or an inert gas at a temperature of 1400 to 2000 ° C. for 1 to 120 minutes by using a discharge plasma system, and sintered. A method for producing a tungsten carbide super hard material, characterized by obtaining an excellent WC-W ₂ C super hard material. 7. The WC powder contains 0.01 to 0.05 mol% of C.
And sintering it in a vacuum or inert gas for 1 to 120 minutes in a vacuum or in an inert gas using a discharge plasma system to obtain a dense WC superhard material. Of producing a tungsten carbide super-hard material. 8. The method for producing a tungsten carbide super-hard material according to any one of claims 5 to 7, further comprising: using a hot isostatic press (HIP) for the super-hard material.
At a pressure of 5 MPa to 200 MPa, a temperature of 1300
A method for producing a tungsten carbide-based ultra-hard material, comprising a step of treating at 2,000 ° C. for 10 to 200 minutes to substantially eliminate pores.