JP2000192184A - Cubic boron nitride-containing hard member and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a dense and inexpensive cubic boron nitride-contg. hard member in which deterioration in the quality of cubic born nitride can be reduced to some degree and excellent in wear resistance and to provide a method for producing the same. SOLUTION: This invention is a cubic boron nitride-contg. hard member produced, under the condition in which cubic boron nitride is metastable, by subjecting powder having a compsn. composed of cubic boron nitride, and the balance at least either cemented carbide or cermet to electric pressure sintering. The particle size of cubic boron nitride is controlled to 1 to 1000 μm. Moreover, the content of the cubic boron nitride particles is 5 to 70 vol.%. The content of impurities in the cubic boron nitride particles is controlled to <=0.3 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hard member in which cubic boron nitride particles are combined with a hard alloy.

[0002]

2. Description of the Related Art In recent years, the application field of WC-based cemented carbide has been greatly expanded due to its excellent toughness and wear resistance. Further, the application field of the cubic boron nitride sintered body has been increasing due to its wear resistance which is much higher than that of cemented carbide. However, since the conventional cubic boron nitride sintered body is manufactured in an ultra-high pressure generating vessel, the manufacturing cost is high, and the shape is also greatly restricted, and its strength and toughness are inferior to cemented carbide, Its superior performance could only be demonstrated in limited applications.

On the other hand, JP-A-60-33336 and JP-A-63-11414 propose to manufacture a cubic boron nitride-containing hard member without using an ultrahigh-pressure vessel.

[0004]

However, the cubic boron nitride-containing hard member manufactured without using the ultrahigh-pressure apparatus has insufficient structure of the structure, and the cubic boron nitride particles are broken and fall off. There was a problem that it was easy.

[0005] To solve the above problems, the present inventors have
We have proposed a method for producing a sintered body in which cubic boron nitride is dispersed in a cemented carbide matrix under conditions where a liquid phase is formed in the cemented carbide by current pressure sintering (Japanese Patent Application Laid-Open No. 9-194978). . According to this technique, it is possible to reduce the quality deterioration of cubic boron nitride densely and to some extent, and to manufacture a sintered body which is inexpensive and has excellent wear resistance.

[0006] Thereafter, the present inventors continued the research and development of this hard member for the purpose of further improving the wear resistance of the hard member.

[0007]

According to the present invention, as a result of the above research, the wear resistance of the hard member is further improved by controlling the amount of impurities in the cubic boron nitride particles used as the raw material powder to a certain amount or less. It is based on the finding that it can be improved.

That is, the hard member of the present invention is obtained by subjecting cubic boron nitride to a powder having a composition comprising at least one of a cemented carbide and a cermet by current-pressure sintering under the condition that cubic boron nitride is metastable. This is a cubic boron nitride-containing hard member manufactured by the above method. Particle diameter of cubic boron nitride is 1 ~ 1000μm
The content of the cubic boron nitride particles is 5 to 70% by volume, and the content of impurities in the cubic boron nitride particles is 0.3% by weight.
It is characterized by the following.

Here, the particle size of the cubic boron nitride is 1 to 1000
The reason why the thickness is set to μm is that if the thickness is less than 1 μm, it is difficult to obtain the effect of adding cubic boron nitride, and if it exceeds 1000 μm, the strength is greatly reduced. Particularly preferred is
It is the case of 3 to 300 μm. Further, the content of cubic boron nitride is set to 5 to 70% by volume. When the content is less than 5% by volume, the effect of improving the wear resistance is small, and when the content is more than 70% by volume, the strength is remarkably reduced. Especially preferred is 20 to 40% by volume. Further, the reason why the impurity content in the cubic boron nitride particles is set to 0.3 wt% or less is that when the content is within this range, particularly excellent wear resistance can be obtained, and particularly preferable is 0.2 wt% or less. It is time.

The composition of the cemented carbide or cermet serving as the matrix of the present hard material depends on the periodic table IVa, Va, V
It is preferable to be composed of at least one hard phase selected from carbides, nitrides and carbonitrides of Group Ia elements and a binder phase mainly composed of an iron group metal because of excellent strength, toughness and hardness. In particular, when WC is used as the main hard phase, the Young's modulus increases and the deformation resistance can be increased, so that excellent performance can be expected as a wear-resistant material.

The content of impurities in the cubic boron nitride particles is reduced to 0.
The reason why the wear resistance is improved by limiting the content to 3 wt% or less is not well understood, but is estimated as follows. Because this hard material is manufactured under cubic boron nitride metastable conditions, in order to prevent thermal deterioration of cubic boron nitride, rapid temperature rise and short-time Manufactured by rapid cooling. Therefore, cubic boron nitride particles having an impurity component exceeding 0.3 wt% in cubic boron nitride are more thermally unstable than cubic boron nitride particles having an impurity content of 0.3 wt% or less. Due to rapid heating and rapid cooling in the sintering process, distortion is likely to occur in the cubic boron nitride particles, which causes cracks in the cubic boron nitride particles when used as a wear-resistant material or during grinding. On the other hand, when the content of impurities in the cubic boron nitride particles is 0.3 wt% or less, strain generation in the cubic boron nitride particles due to rapid heating and rapid cooling can be suppressed, and the cubic boron nitride particles can be suppressed. It was considered that, by making the particles hard to break, the falling of the cubic boron nitride particles could be suppressed, and as a result, excellent wear resistance could be realized. The main impurity elements are Al and S
i, Fe, Ni, Co, Mg, Li, C, O and the like. However, O is easily affected by the particle size of the cubic boron nitride particles,
In the present invention, it was considered to be excluded from the specified amount, for example, 1 / 2-2
It is preferred that the content be 0.5 wt% or less for a powder of μm and 0.2 wt% or less for a powder of 2-8 μm.

The surface of the cubic boron nitride particles is 1300
It is preferable that at least one selected from metals, alloys, and ceramics having a melting point of not less than ° C is coated. This is because, when such a coating layer is provided, the reaction occurring during sintering between the cemented carbide and / or cermet and cubic boron nitride that forms the matrix of the present hard member, in particular, the formation of a liquid phase in the matrix This is because a reaction between the liquid phase and the cubic boron nitride in the case of the above can be prevented, and deterioration of the cubic boron nitride can be prevented. Cr, W, Mo, Ti-Ta, Ti-Mo, Nb-V, TiC, TiN, Al ₂ O
₃ , SiC, TiBN, TiAlN, TiZrN and the like are preferable. The thickness of the coating layer is preferably from 0.01 to 10 μm. Particularly preferred is a time of 0.1 to 5 μm. Examples of the method for forming such a coating layer include a physical vapor deposition method (PVD method) such as a sputtering method and an ion plating method, a chemical vapor deposition method (CVD method), a plating method, and an immersion method.

[0013] The hard member of the present invention is manufactured by a process of mixing raw material powders and loading them into a graphite mold, and a process of sintering the raw material powders under electric pressure. In other words, the raw material powder
5 to 70% by volume of cubic boron nitride particles having an impurity content of 0.3% by weight or less in the particles, and the balance being the periodic table IVa, Va, VI
At least one hard raw material powder selected from carbides, nitrides and carbonitrides of group a elements and a metal raw material powder mainly composed of iron group metals are used. The conditions of the current pressure sintering are as follows: a temperature rise rate of 20 to 500 ° C / min, a sintering temperature of 1000 to 1400 ° C, a holding time at the sintering temperature of 10 seconds to 30 minutes, and a cooling rate of 15 seconds.
℃ / min ～ 400 ℃ / min, pressure is 10 ～ 100MPa.

Here, the reason why the sintering temperature is limited to 1000 to 1400 ° C. is that if the temperature is lower than 1000 ° C., the densification tends to be insufficient, and if it exceeds 1400 ° C., the cubic boron nitride particles are greatly deteriorated. is there. Next, the reason for setting the holding time to 10 seconds or more and 30 minutes or less is that if the sintering time is shorter than 10 seconds, densification is insufficient, and if it is longer than 30 minutes, the cubic boron nitride is converted to hexagonal. This is because metamorphosis is likely to occur. Particularly preferred is 1
Minutes and up to 10 minutes. Further, the reason why the pressing force is set to 10 to 100 MPa is that if the pressure is less than 10 MPa, the promotion of densification hardly occurs, and 1
If the pressure is higher than 00 MPa, a special sintering die is required, and the production cost increases. Also, the heating rate
20 ~ 500 ℃ / min, cooling rate 15 ℃ / min ~ 400 ℃ / min,
Were limited to a heating rate of 20 ° C / min and a cooling rate of 15
If the temperature is lower than ℃ / min, transformation of cubic boron nitride into hexagonal crystal tends to occur, and the temperature rise rate is 500 ° C / min and the cooling rate is 40
If the rate is higher than 0 ° C./min, cracks in the sintered body and strain generation in cubic boron nitride become remarkable, and wear resistance decreases. Then, when the current ON time is 1 to 100 msec, and the current OFF time is 1 msec or more, and the current pressure sintering is performed using a rectangular pulse current, the sintered body becomes very dense, and furthermore, the cubic boron nitride particles and the matrix It is preferable because the wettability is improved, the bonding force is improved, and a hard member having excellent abrasion resistance, in which cubic boron nitride is less likely to fall off, can be obtained.

When at least one element selected from the group consisting of Co, C, and W is diffused in the coating layer covering the cubic boron nitride particles, the bonding between the cubic boron nitride and the WC-based cemented carbide is considered. Power improves. In particular, the effect of diffusion of Co is great, and these diffusions are easily obtained by current pressure sintering using a rectangular pulse current of 1 to 100 msec.

When the hard member is bonded to at least one of a WC-based cemented carbide and a metal material, a compressive residual stress is generated in the hard member, and the hard member is toughened.
Brazing, welding, and soldering are simplified, and the field of application of the material can be expanded.

Further, when the hard member is coated with at least one of diamond, diamond-like carbon and cubic boron nitride, the entire hard member is covered with these coating films, so that very excellent wear resistance is obtained. Shows lubricity. Since this coating film is formed by using cubic boron nitride particles in the hard member as nuclei, it is possible to obtain a coating having extremely excellent adhesion.

In particular, when diamond-like carbon is coated, the film is smooth and has excellent lubricity, so that it is hard to peel off and very excellent performance as a wear-resistant member can be obtained. This excellent adhesion is achieved by particularly high performance because the bonding force between the cubic boron nitride particles in the hard member and the hard alloy as the matrix is enhanced by the present invention.

[0019]

Embodiments of the present invention will be described below. (Example 1) Artificially synthesized cubic boron nitride particles having an average particle size of 15 µm and different impurity contents were prepared, and the impurity content in the cubic boron nitride particles was determined by inductively coupled plasma emission spectrometry.
C was determined by a combustion infrared absorption method. Furthermore, the average particle size
5μm WC, 2μm Co powder, 1μm Ni powder, 2μm Cr
₃ C ₂ powders were prepared, weighed to the compositions shown in Table 1, and mixed using a ball mill to obtain sintering powders.

[0020]

[Table 1]

The thus prepared powder is filled in a graphite mold of φ30 mm, and a rectangular pulse current having a current ON time of 30 msec and a current OFF time of 2 msec is applied while applying a pressure of 30 MPa in a vacuum of 0.01 Torr. Electric current pressure sintering was performed. The temperature rise pattern was 1350 ° C at a rate of 100 ° C / min.
The temperature was kept for 30 minutes and then cooled at a rate of 30 ° C./min.
The size of the sintered body thus obtained is φ30 mm, thickness
The 10 mm sintered body had a good appearance without cracks.
After removing the black scale of the sintered bodies of Nos. 1-1 to 1-6, the specific gravity was measured by the Archimedes method. The sintered bodies of Nos. 1-1 to 1-6 had a dense density of 99% or more of the theoretical density ratio.

Next, a sintered body of 15 × 15 × 9 mm was prepared from these sintered bodies by discharge wire cutting and surface grinding using a # 200 diamond grindstone. Abrasion resistance test was performed by sandblasting SiC having an average particle diameter of 10 μm at a pressure of 5 kg / cm ² for 60 minutes. Table 1 shows the wear amount of No.1-1 to 1-6 sintered bodies, with the wear amount of No.1 sintered body being 100.
It was described in.

From the results shown in Table 1, the samples of Nos. 1-3 to 1-6 in which the content of impurities in the cubic boron nitride is 0.3% by weight or less show excellent wear resistance, It was confirmed that particularly excellent wear resistance was exhibited when the content was 0.2 wt% or less.

Further, when the wear portion of the sample for which the wear resistance was evaluated was cut vertically, and the wear portion was observed in detail, it was found that the amount of impurities in cubic boron nitride exceeded 0.3 wt%, and that the sample was No. 1-1.
In samples 1-2, more cracks were formed in the cubic boron nitride particles than in samples Nos. 1-3 to 1-6. No.1-1
The abrasion resistance of the samples of Nos. 1-3 and 1-2 was worse than the samples of Nos. 1-3 to 1-6 because of the cracks generated in the cubic boron nitride particles. More dropouts,
It is considered that the result of Table 1 was caused.

The amount of impurities contained in the cubic boron nitride of each sintered body is removed by dissolving the hard alloy as a matrix with an acid, and then dissolving the cubic boron nitride particles using a molten salt. An aqueous solution was prepared by adding an acid, and the solution was measured by inductively coupled plasma emission spectrometry. As a result, it was confirmed that the amount of impurities contained in the raw material did not change much.

Example 2 Cubic boron nitride particles having an average particle size of 200 μm and different impurity contents were prepared, and the surface of the particles was coated with TiN by 2 μm by a PVD method. Further, 80% by volume of TiCN having an average particle diameter of 3 μm, and 15 and 5% by volume of Ni and Co powders having an average particle diameter of 2 μm were prepared and mixed by a ball mill to prepare a cermet powder. This cermet powder was blended with the cubic boron nitride particles in an amount of 35% by volume and mixed in a dry system to obtain a sintering powder.

Next, in the lowermost layer, a steel (S
45C), WC-30wt% Co cemented carbide powder in the intermediate layer, cermet powder mixed with the cubic boron nitride particles in the uppermost layer, filled in a graphite mold of φ50mm, and filled in a vacuum of 0.01 Torr or less. Current ON time is 100
msec, current OFF time is 2msec.
The temperature was raised to 50 ° C., and the temperature was maintained for 6 minutes, followed by current pressure sintering. The heating rate and the cooling rate were as shown in Table 2.

[0028]

[Table 2]

The sintered body thus obtained is a sintered body having a diameter of 50 mm and a thickness of 10 mm. Sample No.2-1, 2-2, 2
-3 and 2-4 had good appearance without cracks, but samples No. 2-5 and 2-6, which had a rapid temperature rise of 800 ° C / min, had cracks in the laminate, The abrasion resistance test shown in No. 1 could not be performed. Further, the presence or absence of transformation of cubic boron nitride to hexagonal in each sample was evaluated by X-ray diffraction.
No transformation of cubic boron nitride to hexagonal crystal was observed in -3 and 2-4, whereas in sample Nos. 2-1 and 2-2, a part of cubic boron nitride was transformed to hexagonal crystal. It was confirmed that it was progressing. This was considered because the heating rate and cooling rate were slower than those of Sample Nos. 2-3 and 2-4.

Next, the N 2 sintered and bonded to the steel
o. A 30 × 30 × 9 mm sintered body was prepared from the test specimens of 2-1 to 2-4 by discharge wire cutting and surface grinding using a # 200 diamond grindstone. The test was performed. The test results are shown in Table 2 with the wear amount of the sintered bodies of Nos. 2-1 to 2-4 assuming that the wear amount of the sintered body of sample No. 2-1 is 100.

From the results shown in Table 2, the content of impurities in the cubic boron nitride is 0.3 wt% or less, and the temperature rise rate is 20 to 500 ° C./m
in, sample No.2-4 whose cooling rate is in the range of 15 to 400 ° C / min
It was confirmed that the sample of Example 1 exhibited particularly excellent wear resistance.

Example 3 Sample No. 2 prepared in Example 2
No. 3-1 and N in which the surface of the sintered body on the cubic boron nitride-containing side of No. -4 was coated with diamond and cubic boron nitride by 5 μm by CVD method.
o.3-2 and 5μm diamond-like carbon by PVD method
Using No. 3-3 coated with m, an abrasion resistance test was performed under the same conditions as in Example 2. In this test, the diamond, cubic boron nitride and diamond-like carbon films adhered firmly to the substrate, and no peeled portions were observed.

Table 3 shows the results of the abrasion test.
No.3-1, No.3-2 and No.3-3 are all uncoated samples
No.2-4 was confirmed to have excellent wear resistance.

[0034]

[Table 3]

[0035]

As described above, according to the hard member of the present invention, the wear resistance can be improved by specifying the impurity content in the cubic boron nitride particles in the hard member.

According to the production method of the present invention, the sintering is carried out under a predetermined current and pressure, whereby the wettability between the cubic boron nitride particles and the matrix is improved, and the bonding force is improved. A hard member having high strength and excellent in abrasion resistance that is difficult to fall off can be obtained.

Claims (6)

[Claims] 1. A cubic nitride produced by current-pressure sintering of cubic boron nitride and a powder having a composition consisting of at least one of a cemented carbide and a cermet under the condition that cubic boron nitride is metastable. In the boron-containing hard member, the particle diameter of the cubic boron nitride is 1 to 1000 μm, the content of the cubic boron nitride particles is 5 to 70% by volume, and the impurity content in the cubic boron nitride particles. Is not more than 0.3% by weight. 2. The cubic boron nitride-containing hard member according to claim 1, wherein the impurity content is 0.2 wt% or less. 3. The surface of the cubic boron nitride particles has a thickness of 1300.
The cubic boron nitride-containing hard member according to claim 1, wherein at least one selected from metals, alloys, and ceramics having a melting point of not less than ° C is coated. 4. The cubic boron nitride-containing hard member according to claim 1, wherein the hard member is bonded to at least one of a WC-based cemented carbide and steel. 5. The hard member is coated with at least one selected from the group consisting of diamond, diamond-like carbon, and cubic boron nitride.
3. The cubic boron nitride-containing hard member according to item 1. 6. A cubic boron nitride particle having an impurity content of 0.3% by weight or less in particles of 5 to 70% by volume, with the balance being carbides, nitrides and carbons of Group IVa, Va, VIa group elements. A step of loading at least one kind of hard raw material powder selected from nitrides and a metal raw material powder mainly composed of an iron group metal into a graphite mold, a heating rate of 20 to 500 ° C./min, and a sintering temperature of 1000 to 1400. ℃,
Holding time at sintering temperature is more than 10 seconds and less than 30 minutes, cooling rate is
Sintering the raw material powder in the graphite mold under electric pressure under conditions of 15 ° C./min to 400 ° C./min and a pressure of 10 to 100 MPa. Production method.