JPH10310840A - Super-hard composite member and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a dense composite member excellent in hardness and strength without using an ultrahigh pressure generating vessel by allowing it to contain diamond particles coated with at least one kind among carbides, nitrides and carbonitrides, hard phases and bonding phase metal and allowing it to has a dense structure in which the theoretical density ratio is regulated to specified value or above. SOLUTION: Diamond particles are coated with at least one kind among the carbides, nitrides and carbonitridesof elements selected from the group IVa, Va and VIa elements in the Periodic Table, B, Al and Si to prevent deterioration in diamond by an attack thereon from the liq. phases of cemented carbide or the like produced at the time of sintering. For obtaining the composite member, this coated diamond particles, hard phase powder essentially consisting of at least one kind of compound among WC, TiC, TiN and TiCN and bonding phase powder essentially consisting of iron family metal are mixed. This mixture is charged to a resistance heating device and is subjected to resistance pressure sintering at 1100 to 1350 deg.C under 5 to 200 MPa. In this way, denseness in which the theoretical density ratio is 95% can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a super-hard composite member and a method for producing the same.

[0002]

2. Description of the Related Art Diamond dispersed cemented carbide materials obtained by mixing diamond particles and a WC-based cemented carbide and integrally sintering are disclosed in JP-B-61-56067, JP-B-61-58432, and USP. No. 5158148. Since these materials are manufactured using an ultrahigh-pressure generating container, a dense sintered body can be manufactured, but there is a problem that the cost is high. Further, in terms of performance, there is also a problem that toughness is reduced by adding diamond particles to the cemented carbide.

On the other hand, there has been proposed an attempt to produce such a material by hot pressing. Although the production cost could be reduced by this method, sintering was carried out in a temperature range where a liquid phase was not formed in the cemented carbide, so that a sufficiently dense sintered body could not be produced, and the sintered body strength was low. It was not enough. Attempts have been made to produce such materials at the liquid phase appearance temperature and to densify them (Japanese Patent Application Laid-Open No. 50-146614), but since sintering took a long time, diamond Had a problem that part of the material was transformed into graphite. Further, US Pat. No. 5,096,655 proposes a technique for producing a composite member holding metal-coated superhard particles in a binder phase by an infiltration method. In this method, the binder phase metal is infiltrated into the gap between the diamond particles at a temperature lower than 1300 ° C. However, it is difficult to produce a dense composite member by the infiltration method, and the strength of the sintered body is insufficient. Was something.

In general, a hard alloy in which the hard phase is mainly WC and the binder phase is an iron group metal such as Co or Ni is called a WC-based cemented carbide, and the hard phase is mainly composed of TiC (N) and the binder phase is mainly composed of TiC (N). Is a TiC (N) -based cermet. These hard alloys are generally above 1350 ° C
The sintering is carried out at a temperature of not more than 00 ° C. and in a vacuum for about one hour without pressure. The reason why the sintering is performed in such a temperature range is that the formation of a liquid phase promotes sufficient densification and produces a material having excellent hardness and strength.

[0005] For this reason, in order to produce a sufficiently dense sintered body in which diamond particles are dispersed using the above-mentioned cemented carbide and cermet as a matrix, diamond which does not use an ultrahigh pressure generating vessel is formed under metastable conditions. There is a problem that diamond dissolves in the liquid phase and becomes graphitized during reprecipitation.

[0006]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a super-hard composite member which can be manufactured without using an ultra-high pressure generating vessel and which is dense and excellent in hardness and strength, and a method of manufacturing the same. It is in.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a carbide, nitride and carbonitride of an element selected from Group IVa, Va and VIa elements of the periodic table, B, Al and Si. And a hard phase mainly composed of at least one compound selected from WC, TiC, TiN and TiCN, and a binder phase metal mainly composed of an iron group metal. A composite member having a dense structure with a theoretical density ratio of 95% or more.

[0008] By coating diamond particles with carbides, nitrides, and carbonitrides as described above, diamond (CB) is formed from the liquid phase of cemented carbide or cermet formed during sintering.
N) can be prevented from being attacked and degraded. As this coating material, Cr, Ti, Zr, Hf, Mo, W,
Particularly preferred are carbides, nitrides and carbonitrides of B, Al and Si. Needless to say, the composite member of the present invention may contain unavoidable impurities. Inevitable impurities include, for example, Al, Ba, Ca, Cu, Fe, Mg, M
n, Ni, Si, Sr, S, O, N, Mo, Sn, Cr
And the like. In addition, by adopting a structure having a denseness with a theoretical density ratio of 95% or more, a composite member having high diamond holding power, excellent strength and wear resistance can be obtained.

It is preferable that such a rigid composite member further includes the following requirements alone or in combination. (1) ISO standards A00 to A04 and B00 to B04
It has a density satisfying the range up to. Whether or not the material is dense can be evaluated by subjecting a cross section of this material to mirror finishing and then observing the structure with an optical microscope (for example, magnification 200 times).

(2) Free carbon is present in the composite member. In order to produce a dense composite member in which diamond is dispersed in a WC-based cemented carbide or a TiC (N) -based cermet under the metastable condition of diamond, it is preferable that the composition be such that a liquid phase is generated at as low a temperature as possible. This is because the lower the temperature, the more the quality of the diamond can be prevented from deteriorating due to the thermal history. In cemented carbides and cermets, high-carbon alloys that generate free carbon in sintered bodies generate a liquid phase at a lower temperature than low-carbon alloys, so alloys with a composition that generates free carbon in composite members are preferred. It is. In addition, by adopting such a high carbon composition, the solid solubility of the carbide coated on the diamond particle surface in the liquid phase is reduced, and these carbides are dissolved in the liquid phase, and the diamond is directly converted into the liquid phase. An attack can be prevented. Furthermore, the presence of free carbon improves the lubricity of the surface of the sintered body, and can be expected to provide an excellent sliding wear-resistant material.

(3) The content of diamond changes continuously or stepwise in the thickness direction such that the amount of diamond particles increases on one surface side of the super-hard composite member and decreases on the other surface side. In this super-hard composite member, the inclusion of diamond causes problems such as a decrease in toughness, an increase in cost, and a decrease in workability. Therefore, such a problem can be solved by increasing the content of diamond only in necessary portions and by reducing or eliminating the content of diamond in unnecessary portions. Note that the change in the diamond content includes a stepwise change and a substantially continuous change.

(4) It is bonded on a substrate made of one of a WC-based cemented carbide, a TiC (N) -based cermet, and a metal material. For the same reason as in the above item (3), it is preferable that the super-hard composite member is joined to a substrate made of any of a WC-based cemented carbide, a TiC (N) -based cermet, and a metal material. In particular, when sintering is performed on a metal material such as steel, the bonding strength, which has conventionally been insufficient by brazing the sintered body and the metal base, is improved, and the brazing step can be omitted. In addition, the use of steel as the base makes it possible to perform a brazing operation between other steel products and steel, so that the joining strength and workability are greatly improved.

Thus, the super-hard composite member and the super-hard alloy,
By joining with a cermet, a member having both hardness and toughness can be obtained. In addition, it is advantageous because a compressive residual stress can be generated on the surface due to the coefficient of thermal expansion. It is preferable to sinter the super-hard composite member, the super-hard alloy, and the metal material in this order. When connecting the metal material and the cemented carbide, a thin insert material (for example, Ni foil) may be inserted between the two to suppress the voids by the Kirkendall effect of the metal material.

(5) At least a part of the diamond particles is replaced with at least one of cubic boron nitride and wurtzite boron nitride. Since cubic boron nitride and wurtzite boron nitride are harder than diamond and have better stability to iron group metals than diamond, they can be expected to have better performance than diamond in terms of wear resistance against iron group metals. In addition, since the present super-hard composite material is mainly composed of an iron group metal in the binder phase, the surface of the CBN is hardly eroded during liquid phase sintering, and it is possible to produce a sintered body that is dense and has excellent mechanical properties. it can.

From the viewpoint of the production cost, the method for producing the hard composite member is preferably a method in which diamond is produced by sintering for a short time under metastable conditions. For example, periodic rate table
Coating the diamond particles with at least one of carbides, nitrides and carbonitrides of elements selected from the group consisting of IVa, Va, VIa group elements, B, Al and Si; WC, TiC,
A step of mixing a hard phase powder mainly composed of at least one compound selected from TiN and TiCN and the coated diamond particles, and a binder phase powder mainly composed of iron group metal; Arranging the raw material member in the current-carrying heating device;
And a step of sintering under electric pressure at 50 ° C. and 5 to 200 MPa.

Here, when the diamond particles are coated in advance with the above-mentioned predetermined carbide, nitride or carbonitride, a known CVD method, PVD method or plating method may be used.

The raw material members include the powders of the raw materials themselves, green compacts pressed in advance, intermediate sintered bodies, and laminates thereof. If necessary, a grain growth inhibitor such as a high melting point compound may be added when mixing the raw material powders. Examples of the high melting point compound include carbides, nitrides, and carbonitrides of elements belonging to the group IVa, Va, and VIa. Most preferably, no grain growth inhibitor is added. When adding, minimize it. However, it is preferable to add the same carbides, nitrides, and carbonitrides as those coated on the surface of the diamond particles because the dissolution of the carbides, nitrides, and carbonitrides on the surface of the diamond particles in the liquid phase can be suppressed.

In the electric pressure sintering, heating, pressurizing and cooling can be rapidly performed by direct energization to the material to be sintered without using an external heater, so that sintering can be completed in a short time of 10 minutes or less. Therefore, the time during which the material to be sintered is exposed to a high temperature can be shortened as compared with the case where the maximum temperature holding time is simply shortened by conventional pressure sintering, and the sintering can be completed without transforming the diamond into graphite. Moreover, the bonding process between diamond and the matrix can be increased by the energization process. Also,
A plasma may be generated between the particles through a pulsed current to further improve the sintering and bonding force between the diamond and the matrix. As described above, in the current pressure sintering, the performance merit unique to the present super-hard composite member, which cannot be obtained by the conventional pressure sintering method, can be obtained. In addition, since production can be performed in a short time, cost reduction can be expected by improving the operation rate of equipment, and large-sized sintered bodies that can be produced with the production method using an ultra-high pressure generation vessel can be produced. Have.

The sintering is desirably performed in the presence of a liquid phase. Densification is promoted by causing the liquid phase to appear and performing sintering. Thereby, the strength and hardness of the sintered body are improved.

The reasons for limiting the above sintering conditions are as follows. If the sintering temperature is lower than 1100 ° C., the densification hardly proceeds, and if it exceeds 1350 ° C., the liquid phase tends to be stained. The sintering temperature here refers to the temperature of the graphite mold surface when controlling the sintering furnace. It is considered that the actual sample temperature is about 150 to 300 ° C. higher than this temperature. The temperature difference seems to change depending on the graphite mold used and the sample size and shape. In order to obtain a dense sintered body, the actual sample temperature is preferably set to 1300 ° C. or higher. This is 1300
When the sample temperature is higher than ℃, a liquid phase of a cemented carbide and a cermet is generated, so-called liquid phase sintering, and promotion of densification can be expected.

If the pressing force is 5 MPa or less, the effect of pressure sintering is not seen, and it is difficult to increase the pressing force beyond 200 MPa in terms of equipment, which causes a cost increase. A particularly preferred pressure is between 10 and 50 MPa. The reason is that an inexpensive graphite type can be used.

Further, the sintering time is preferably within 3 minutes. By shortening the sintering time, grain growth of the hard phase and movement of the liquid phase during sintering can be suppressed, and a hard alloy having a different bonding layer amount in the thickness direction can be produced. More preferably, it is within one minute. The sintering atmosphere is preferably a vacuum of 0.1 Torr or less.

As a preferable production method other than the current pressure sintering method, there is an SHS / HIP sintering method. Also in this method, the sintering can be completed in a short time, the transformation of diamond into graphite can be suppressed, and the isotropic pressure sintering has the advantage that the sintered body can be near-net-shaped.

In order to manufacture a composite member in which the amount of diamond particles changes in the thickness direction, a plurality of types of mixed powders having different diamond particle contents may be prepared. Then, in the step of arranging the raw material members in the electric heating device, these plural kinds of mixed powders are laminated and arranged in the order of the content of the diamond particles. If the type of the prepared powder mixture is small, it is possible to obtain an ultra-hard composite member (the minimum is two stages—with or without diamond particles) having a different diamond particle content stepwise in the thickness direction. If the thickness of each layer to be laminated is reduced by increasing the number of layers, an ultra-hard composite member in which the content of diamond particles changes substantially continuously can be obtained. According to the method of the present invention, the grain growth of the hard phase and the movement of the liquid phase during sintering are small, so that a sintered body having such a configuration can be stably manufactured. In the same manner, an ultra-hard composite member in which the amount of the binder phase changes in the thickness direction can be manufactured.

To join such a hard alloy having a tilted structure to a substrate made of a cemented carbide, a cermet, or a metal material, a raw material member together with the substrate may be arranged in an electric heating device. For example, raw material powder for ultra-hard composite members,
A cemented carbide substrate and a metal material substrate can be sequentially laminated and joined in an electric heating device.

Hereinafter, embodiments of the invention will be described. (Example 1) Diamond powder (average particle size: 50 μm) coated with Cr carbide to a thickness of 2 μm, WC powder (2 μm),
Using Co powder (2 μm), TiC powder (2 μm), and Ni powder (2 μm), a mixed powder having the ratio (% by weight) shown in Table 1 (sample Nos. 1-1 to 1-7) ) Was prepared, and the mixed powder was wet-mixed with a ball mill for 5 hours and then dried. Next, this dry powder is filled in a graphite mold, and while applying a pressure of 20 MPa from above and below in a vacuum of about 0.01 Torr or less, the graphite mold is energized at a heating rate of 250 ° C./min. After reaching 1 minute, keep for 1 minute
The quenching was performed at a speed of min.

[0027]

[Table 1]

The obtained sintered body having a diameter of 20 mm and a thickness of 5 mm had no cracks and had a dense structure having a theoretical density ratio of 95 to 100%. The surface was ground with a # 250 diamond grindstone, mirror-polished, and the structure was observed at 200 times magnification using an optical microscope. All samples are A0 according to ISO standard.
2, high density in the range of B02. In addition, 500g
Table 1 also shows the results of the measurement of Knoop hardness under the load of Example 1. In all samples, hardness values that could not be considered with compositions containing no diamond were measured, and although indirect, diamond was contained in the sintered body. It could be confirmed that it remained.

For comparison, the powder of sample No. 1-1 was pressed at 100 MPa and sintered by the conventional manufacturing method (keeping in vacuum at 1350 ° C. for 1 hour) (sample No. 1-1 ′). The sintered body was similarly ground and mirror-polished, and Knoop hardness was measured. The results are also shown in Table 1. The hardness of Sample No. 1-1 'was very low, and microscopic observation confirmed that the diamond was graphitized.

Example 2 Sample No. 1 prepared in Example 1
-5, using powder of the same composition as 900, 1000, 1100, 1200, 130
At a sintering temperature of 0.1400 ° C., a sintered body was produced in the same manner as in Example 1. The sintered body was surface-ground with a # 250 grindstone, mirror-polished, and the presence or absence of pores in the WC-Co phase was observed using an optical microscope at a magnification of × 200. Observation results were classified into A00 to B08 based on ISO and described in Table 2. Table 2 also shows the results of measuring the actual sample temperature during sintering with a thermocouple, and the bending strength and theoretical density ratio of each sintered body. The theoretical density ratio is the specific gravity of WC.
15.6 g / cm ³ , Co specific gravity 8.9 g / cm ³ , VC specific gravity 5.5 g
/ cm ³ , the specific gravity of diamond was 3.5 g / cm ³ , the theoretical density of this composition was calculated, and the density of the sintered body was measured by the Archimedes method.

[0031]

[Table 2]

From Table 2, it can be seen that the actual sample temperature was
The sample No. has a low theoretical density ratio of 90% and has many nests as compared with B08, so that the bending strength is low, and the samples Nos. 2-3, 4, and 5 in which the type A and type B pores are smaller than 04 are dense. It was confirmed that the composition exhibited particularly excellent characteristics. In Sample No. 2-6, the liquid phase oozed out of the graphite mold during sintering, and the flexural strength also showed a low value.

The sintering temperature is 1100-1300 ° C.
It was also found that the range described above was preferable from the viewpoint of bending strength. It was also confirmed that the difference between the sintering temperature for temperature control and the actual sample temperature was about 200 ° C.

Example 3 WC powder having an average particle size of 3 μm,
Co powder with an average particle size of ₂ μm, Cr ₃ C _{2 with} an average particle size of 1 μm
Powders are prepared and these are weight% WC: Co: Cr ₃ C
₂ = 89: 10: 1 to prepare a superhard powder. Further, a diamond powder having an average particle size of 3 μm was prepared, and the surface of the powder was coated with various carbides (nitrides, carbonitrides) shown in Table 3 by 0.5 μm by a PVD method. Then, these diamond powders were blended so as to be 30% by volume with respect to the previously prepared carbide powder, and mixed by a ball mill for 5 hours to prepare a raw material powder. These raw material powders are charged into a graphite mold, and a current of 1100 ° C. is applied to the graphite mold using an electric heating sintering apparatus while applying a pressure of 50 MPa from above and below at a heating rate of 200 ° C./min. At the time
The hard members of Sample Nos. 3-1 to 3-13 were prepared by keeping for 30 seconds and cooling at a rate of about 100 ° C./min.

[0035]

[Table 3]

The thus obtained sintered body (sample No. 3
-1 to 3-13) were subjected to a disk-type abrasive wear test (a test piece was placed around the circumference of a 10 mm wide disk rotating in a SiC slurry).
(Method of evaluating abrasion resistance by pressing with a pressure of kg). Table 3 also shows the results. The evaluation results are shown by standardizing the wear test results of the other samples, with the wear amount of sample No. 3-1 made of diamond powder without metal coating being set to 1.

As shown in Table 3, Sample No. 3-1 having no coating on diamond and Sample No. 3 containing no diamond
No. 3-2 to 3- in which diamond particles were coated with carbide, nitride and carbonitride compared to -13 (only cemented carbide)
It was found that 11 samples could achieve very good wear resistance.

Next, sample No. 3-5 'was prepared in which carbon was added to the cemented carbide powder having the same composition as sample No. 3-5 so that free carbon was deposited in the sintered body. . This sample was similarly evaluated using the above-mentioned abrasive wear tester. The results are also shown in Table 3. It can be seen that the sample of No. 3-5 'on which free carbon was deposited exhibited twice the wear resistance as the sample of No. 3-5 on which no free carbon was deposited. It could be confirmed.

(Example 4) Powder and steel having the composition (% by weight) shown in Table 4 were pressed in layers and filled into a graphite mold, and the temperature was raised at a rate of 200 ° C / 200 ° C. while applying a pressure of 10 MPa from above and below. current through the graphite mold so that
When the temperature reached 50 ° C., it was kept for 1 minute to perform rapid cooling.

[0040]

[Table 4]

When the obtained disk-shaped sintered body having a diameter of 50 mm and a thickness of 20 mm was observed, no crack was generated between the layers and the layers were well bonded. The cross section in the thickness direction of this sintered body was mirror-polished and composition analysis was performed by EPMA. Diffusion was suppressed.

The sintered body of this structure can obtain high wear resistance due to the surface layer containing diamond, and high strength and high toughness due to the use of a super hard and steel layer as the inner layer.
Usually, it is a material that can achieve both contradictory characteristics. Further, the use of a steel layer has a great advantage in use, such as enabling welding, and the advantage that such an excellent material can be manufactured at low cost without using an ultrahigh-pressure vessel is very significant.

Example 5 Sample Nos. 4-1 to 4-7 in which the diamond described in Example 2 was partially or entirely replaced with CBN or WBN having an average particle diameter of 1 μm under the same conditions as in Example 2 To produce a sintered body having a diameter of 20 mm and a thickness of 5 mm. Table 5 shows the compositions of Sample Nos. 4-1 to 4-7.

[0044]

[Table 5]

These sintered bodies were surface ground with a # 250 diamond grindstone, mirror-polished, and observed with an optical microscope. As a result, all the samples showed values with a theoretical density ratio of 95% or more. In addition, cracks occurred in all samples,
No dropout of CBN (WBN) particles was observed, and it was confirmed by X-ray qualitative analysis that CBN (WBN) could be sintered without being transformed into hexagonal BN.

[0046]

As described above, the composite member of the present invention is capable of firmly dispersing and holding diamond (CBN) particles having excellent hardness and abrasion resistance in a high-toughness cemented carbide or cermet. By forming a structure, both extremely high hardness and strength can be achieved.

Therefore, the composite member of the present invention can be used for cutting tools such as casing bits, earth auger bits, shield cutter bits, etc., cutting tools such as woodworking, metalworking, and resin processing chips, and machine tools. It can be used for wear-resistant materials such as bearings, centerless blades and nozzles, plastic working tools such as drawing dies, and tools for grinding.

Further, the production method of the present invention does not use an ultra-high pressure generating vessel, but employs current pressure sintering or SHS / HI
By P sintering, a hard composite member excellent in hardness and wear resistance can be manufactured. In other words, diamond particles coated with a predetermined carbide (nitride, carbonitride) are dispersed in a cemented carbide or cermet, and a liquid phase is generated in a short time and sintered, so that the strength, hardness, and wear resistance are improved. And a dense super-hard composite member can be obtained. In particular, since the heating time, the keeping time, and the cooling time can be shortened, it is expected that the cost and the size of the sintered body can be further reduced as compared with the conventional manufacturing method (including the method using an ultrahigh pressure generating vessel).

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C22C 29/02 B22F 3/14 101B

Claims (8)

[Claims] 1. A composite member comprising a hard phase and a binder phase metal, wherein the hard phase is a carbide or nitride of an element selected from the group IVa, Va, VIa, B, Al and Si of the periodic table. And a diamond particle coated with at least one of carbonitride and at least one compound selected from WC, TiC, TiN and TiCN, wherein the binder phase metal is mainly an iron group metal, and the theoretical density is An ultra-hard composite member having a dense structure with a ratio of 95% or more. 2. ISO standards A00 to A04 and B0
The super-hard composite member according to claim 1, wherein the ultra-hard composite member has a density satisfying a range of 0 to B04. 3. The super-hard composite member according to claim 1, wherein free carbon is precipitated. 4. The diamond content is changed continuously or stepwise in the thickness direction such that the amount of diamond particles is larger on one surface side of the super-hard member and smaller on the other surface side. The super-hard composite member according to claim 1, wherein 5. The super-hard composite member according to claim 1, wherein the super-hard composite member is bonded to a substrate made of any one of a WC-based cemented carbide, a TiC (N) -based cermet, and a metal material. 6. The super-hard composite member according to claim 1, wherein at least a part of the diamond particles is replaced by at least one of cubic boron nitride and wurtzite boron nitride. 7. The method according to claim 7, wherein the diamond particles are prepared in advance in a periodic table IVa, V
coating with at least one of carbides, nitrides and carbonitrides of an element selected from the group consisting of a, VIa group elements, B, Al and Si; and at least one type selected from WC, TiC, TiN and TiCN. Mixing a hard phase powder composed of a compound and the coated diamond particles, and a binder phase powder of an iron group metal; disposing a raw material member composed of the mixed powder in an electric heating device; And sintering under pressure at 1100 ° C. to 1350 ° C. and 5 to 200 MPa. 8. The method according to claim 7, wherein at least a part of the diamond particles is replaced with at least one of cubic boron nitride and wurtzite boron nitride.