JP2002187721A - Multiple ceramic powder and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of multiple ceramic powder, by which a sintered compact having higher hardness is obtained as compared to a sintered compact formed by using binary ceramic as a raw material and a manufacturing method thereof. SOLUTION: At least 2 kinds of the powder of metals selected from a group of Ti, Al, V, Nb, Zr, Hf, Mo, Ta, Cr and W, a reducing agent and a catalyst for accelerating the nitriding or the carbonitriding of the metals are mixed to alloy 2 kinds of the metals with each other by mechanical alloying. The multiple nitride ceramic powder is obtained by firing the alloy under the presence of gaseous nitrogen to nitride. In the case that powdery carbonaceous material is used as the reducing agent, the powdery carbonaceous material acts also as a carbon source. In such a case, the alloy is carbonitrided to obtain multiple carbonitride ceramic powder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-component ceramic powder comprising two or more metal elements and N, and furthermore, C, and a method for producing the same.

[0002]

2. Description of the Related Art A composite material produced by sintering a metal powder and a ceramic powder together has both high toughness derived from a metal and high hardness and high strength derived from a ceramic. Widely used in the field. For example, a tungsten carbide-cobalt cemented carbide obtained by sintering tungsten carbide and cobalt, and a titanium carbide cermet obtained by sintering titanium carbide and molybdenum are employed as cutting tools for cutting tools. These may further contain niobium carbide or the like.

Incidentally, ceramic powder used as a raw material of the composite material includes binary carbide ceramics containing one kind of metal element and C as constituents such as tungsten carbide, titanium carbide and niobium carbide as described above. And binary nitride ceramics containing one kind of metal element and N as constituents. Although these have sufficient hardness by themselves, ceramics having higher hardness may be required depending on the application.

Examples of high hardness materials include diamond and tetragonal boron nitride (c-BN). Furthermore, in recent years, T, Al and N
It has been reported that a thin film of i-Al-N ternary ceramics has a high hardness comparable to that of c-BN. That is, the hardness of the Ti—Al—N ternary ceramic is Ti
Significantly higher than the hardness of N or AlN and TiN
And AlN are both higher than a sintered body in which both are sintered.

[0005] A thin film of Ti-Al-N ternary ceramics can be produced by a physical vapor deposition (PVD) method or a chemical vapor deposition (CVD) method.

[0006]

SUMMARY OF THE INVENTION Diamond and c-B
N has a disadvantage that the oxidation resistance is not good and the production cost of the composite material rises because it is expensive. Therefore, in order to obtain a chemically stable and high-hardness composite material at low cost, two or more metal elements and C or N are used as constituent components, such as Ti-Al-N ternary ceramics. It is considered effective to use multi-component ceramic powder as a raw material.

[0007] However, as described above, the form of the Ti-Al-N ternary ceramics produced by the PVD method or the CVD method is a thin film, and no powder has been reported so far.

[0008] In addition, when a multi-component ceramic powder is to be produced by a PVD method or a CVD method, there arises a problem that the production cost of a composite material rises. The reason for this is that these methods have low reaction efficiency and low reaction rate, so that the production efficiency of the multi-component ceramic powder is low. Furthermore, in these methods, it is necessary to experimentally determine the reaction conditions under which powder can be obtained, and this disadvantageously requires a long time and is complicated.

[0009] As another method of producing a Ti-Al-N ternary ceramic powder, nitriding a mixed powder of Ti and Al is recalled. However, in this case, T
Only a mixed powder of iN and AlN can be obtained.
-Al-N ternary ceramic powder cannot be obtained.

Therefore, it is recalled that a Ti-Al binary alloy is nitrided. However, this alloy is covered with an oxide film formed by oxidizing the surface with oxygen in the air. For this reason, since it is extremely difficult to nitride the Ti-Al binary alloy to the inside, the hardness of the composite material is not so much improved even when the obtained powder is used as a raw material.

As described above, it is extremely difficult to produce a multi-component ceramic powder containing two or more metal elements and C or N as constituents. Has not yet been obtained.

The present invention has been made in order to solve the above-mentioned problems, and is a multi-element ceramic capable of obtaining a sintered body having a higher hardness than a sintered body made of a binary ceramic. It is an object to provide a powder and a method for producing the powder.

[0013]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides Ti, Al, V, Nb, Zr, Hf,
At least 2 selected from the group consisting of Mo, Ta, Cr, W
It is characterized in that a kind of metal element and N are used as constituent components.

Further, in addition to these, C may be a constituent component.

That is, the multi-component ceramic powder according to the present invention is, for example, Ti-Al-N or Ti-Al
It is a ternary or higher composite nitride ceramic powder or composite carbonitride ceramic powder represented by -Nb- (C, N) or the like.

A sintered body using such a composite nitride ceramic powder or a composite carbonitride ceramic powder as a raw material is higher than a sintered body using a binary ceramic such as TiN, TiC, NbC or the like as a raw material. Indicates hardness. In addition, the relative density of the former is close to the ideal density, and therefore, the former also exhibits high strength and high toughness.

When the characteristics of the sintered body made of the composite nitride ceramics as a raw material and the characteristics of the sintered body made of the composite carbonitride ceramics are compared, if the metal in both sintered bodies is of the same kind, For example, the latter shows higher hardness. That is, it is preferable that the powder is a multi-component ceramic powder containing C as a component.

In this case, the atomic ratio between C and N is C / N <1.
It is preferred that If C / N is 1 or more, the hardness of the sintered body may decrease depending on the type of the multi-component ceramic powder.

An oxide film is formed on the surface of the above-mentioned metal by oxidizing the metal with oxygen in the air. Therefore, the multi-component ceramic powder contains O as an irreversible impurity.

The proportion of O is preferably 0.5% by weight or less. If the content exceeds 0.5% by weight, a sintered body having low hardness and toughness may be obtained.

The present invention also relates to Ti, Al, V, Nb,
Mixing powders of at least two metals selected from the group consisting of Zr, Hf, Mo, Ta, Cr, and W, a reducing agent, and a catalyst that promotes nitriding or carbonitriding of the metals; A step of alloying the metals by mechanical alloying to form an alloy, and a step of firing the mixed powder containing the alloy in the presence of nitrogen gas and nitriding or carbonitriding the alloy to form a multi-element ceramic, It is characterized by having.

When the firing treatment is performed, first, an oxide film existing on the surface of the alloy is reduced by a reducing agent. Therefore, the surface of the alloy becomes extremely active. Therefore, the alloy can be nitrided or carbonitrided easily and easily from the surface to the inside, and in a large amount. Therefore, multi-component ceramic powder can be produced at low cost.

A sintered body made of a multi-element ceramic powder nitrided or carbonitrided from the surface to the inside as described above has a high hardness.

Preferred examples of the reducing agent include alkaline earth metals and powdered carbon materials. Among them, it is preferable to use a powdered carbon material. When the oxide carbon itself is oxidized by reducing the oxide film, the powdered carbon material changes to CO or CO ₂ . Because these are gases, they can be easily and quickly discharged out of the reactor.

The powdered carbon material also functions as a C source. That is, in this case, a composite carbonitride ceramic can be obtained.

In this case, the addition ratio of the powdered carbon material is 0.1%.
It is preferable that the content be 1% by weight to 11.6% by weight. 0.
If the amount is less than 1% by weight, the reducing effect is poor, and if it exceeds 11.6% by weight, free carbon is generated, so that a sintered body having low hardness may be obtained.

On the other hand, preferred examples of the catalyst include alkaline earth metals, Group VIIA elements and Group VIII elements.

In any case, it is preferable that after the firing treatment, the obtained multi-component ceramic powder is treated with an acid solution. This is because unreacted reducing agent and catalyst, and oxidized reducing agent and catalyst are eluted into the acid solution, so that high-purity multi-component ceramic powder can be obtained.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a multi-component ceramic powder and a method for producing the same according to the present invention will be described below in detail with reference to the accompanying drawings.

The multi-component ceramic powder according to the present embodiment is a composite nitride ceramic powder containing two or more metal elements and N as constituents, or a composite nitride ceramic powder containing two or more metal elements and N and C. It is a composite carbonitride ceramic powder as a component.

The metal elements are Ti, Al, V, Nb, Z
2 selected from the group of r, Hf, Mo, Ta, Cr, W
More than a species. These constitute an alloy that can be nitrided or carbonitrided with each other.

N is supplied from a nitrogen gas contained in an atmosphere gas when a powder of an alloy containing two or more of the above-mentioned metal elements is subjected to a sintering process.
As will be described later, a composite nitride ceramic powder is obtained by nitriding an alloy containing two or more of the above metal elements with nitrogen gas.

A sintered body obtained by sintering the composite nitride ceramic powder or a sintered body (composite material) obtained by sintering the composite nitride ceramic powder and the metal powder together, ie, a composite A sintered body using nitride ceramic powder as a raw material can be made of 2N such as TiN or TiC.
Higher hardness than sintered body made from base ceramic powder.

In the case of the composite carbonitride ceramic powder further comprising C, C is supplied from a powdered carbon material such as carbon black. The sintered body using the composite carbonitride ceramic powder as a raw material has higher hardness than the sintered body using the composite nitride ceramic powder as a raw material.

Here, when C is a constituent component, C and N
Is preferably C / N <1. C / N
If the ratio is 1 or more, the hardness of the sintered body may decrease depending on the type of the multi-component ceramic powder.
A more preferred atomic ratio is 0.4 <C / N <0.9.

This multi-component ceramic powder contains O as an irreversible impurity. This O ratio is
It is set to 0.5% by weight or less. If the content exceeds 0.5% by weight, the hardness of the sintered body using the multi-component ceramic powder as a raw material may be low.

Such a multi-component ceramic powder can be produced as follows.

FIG. 1 is a flowchart showing a method for producing a multi-component ceramic powder according to the present embodiment. This manufacturing method includes a mechanical alloying step S1 for mixing a metal powder, a reducing agent, and a catalyst, a sintering step S2 for sintering the obtained mixed powder, and an acid sintering process. Acid treatment step S3 of treating with a solution.

First, in the mechanical alloying step S1, a metal powder, a reducing agent and a catalyst are mixed.

As the metal powder, Ti, Al, V, N
At least two powders are selected from the group of b, Zr, Hf, Mo, Ta, Cr, W. These easily form alloys by mechanical alloying. In addition, a sintered body made of a multi-component ceramic powder containing these as components has high hardness.

The reducing agent is for reducing the oxide film formed on the surface of these metals. That is, these metals are usually covered with an oxide film formed by oxidizing the surface with oxygen in the air.
The reducing agent reduces this oxide film by being oxidized during the firing process.

Preferable examples of the reducing agent that functions as described above include alkaline earth metals represented by Mg, Ca, Sr, and Ba or powdered carbon materials. Both of them have a strong reducing power compared to the above-mentioned metals, and therefore,
It is an effective reducing agent for the above metals.

Of these, it is preferable to use a powdered carbon material. Powdered carbon material is easy to handle, and
This is because it is inexpensive and advantageous in cost. Further, when the powdered carbon material reacts with the oxide film, CO or CO ₂
Is generated. Since these are gases, they can be easily and quickly discharged out of the firing furnace when performing the firing process step S2. That is, no oxide remains. This is because high-purity multi-element ceramic powder can be obtained. Further, since the powdered carbon material also functions as a C source, it is possible to produce a composite carbonitride ceramic having higher hardness than the composite nitride ceramic.

The proportion of the powdered carbon material is preferably 0.1% by weight to 11.6% by weight. If it is less than 0.1% by weight, the ability as a reducing agent is poor. Also, 1
If it exceeds 1.6% by weight, free carbon will be generated. For example, when Al powder is selected as the metal, Al ₄ C ₃ is also generated. A sintered body containing such a material has poor hardness and toughness.

When Mg powder is used as the reducing agent, 0.1 to 5 g may be added to 100 g of metal powder. When Ba powder is used, 0.5 to 10 g may be added to 100 g of metal powder.

The catalyst is for accelerating the nitriding of the metal. In addition, when the powdered carbon material is present, carbonitriding is also promoted.

Preferred examples of the catalyst include alkaline earth metals, Group VIIA elements and Group VIII elements. Among them, Group VIIA element or V
It is preferred to use Group III elements. These are easily eluted into the acid solution by the acid treatment step S3 described below,
Therefore, multi-component ceramics can be obtained with high purity. The group VIII element is F
e, Co and Ni are exemplified, and Mn is exemplified as the group VIIA element. Among them, Mn is preferably used because it is most excellent in promoting the nitriding or carbonitriding of the metal.

The preferable addition ratio of the catalyst is not uniquely determined because it varies depending on the type of the catalyst. For example, M
When using n, 3% by weight or less, Fe, Co, Ni
When is used, the content is preferably 5% by weight or less. When the catalyst is added in excess of the above ratio, the residual amount of the unreacted catalyst or the production amount of these nitrides or carbonitrides increases in any case. Therefore, it is not easy to elute them in the acid treatment step S3, and it is not easy to improve the hardness of the sintered body.

Here, as the reducing agent and the catalyst, not only pure substances of alkaline earth metals, Group VIIA elements or Group VIII elements but also compounds can be used. For example, carbonyl iron or carbonyl nickel powder may be used instead of Fe or Ni powder. Such a compound powder has a significantly smaller particle size than a pure substance powder. For this reason, since it is uniformly dispersed in the mixed powder, it is possible to promote nitriding or carbonitriding with a smaller amount of addition than the pure substance powder. Therefore, resource saving can be achieved, which is ultimately advantageous in cost.

The above mixing of the metal powder, the reducing agent and the catalyst is carried out under such conditions that the two selected metals form an alloy by mechanical alloying. In particular,
Metal powder, reducing agent,
The water-cooled container is sealed by containing the catalyst and the steel balls, and the rotating blade inserted into the water-cooled container is rotated. As a result, the metal powders are ground and pressed under high energy,
As a result, an alloy powder is generated. Further, the reducing agent and the catalyst are substantially uniformly dispersed in the alloy powder.

Next, the mixed powder thus obtained is subjected to a baking treatment in the presence of nitrogen gas in a baking treatment step S2. At this time, nitriding of the alloy proceeds in the mixed powder containing no powdered carbon material, while nitriding proceeds in the mixed powder containing the powdered carbon material.

The nitrogen gas may be contained in the atmosphere gas to such an extent that the alloy can be nitrided or carbonitrided. That is, only the nitrogen gas may be used as the atmospheric gas, or a mixed gas of the nitrogen gas and another inert gas such as an argon gas may be used as the atmospheric gas.

The temperature of the baking treatment is 1000 ° C. to 1 ° C.
The temperature is preferably set to 600 ° C. If the temperature is lower than 1000 ° C., nitriding or carbonitriding does not proceed efficiently. Also, 1600
Even if the temperature exceeds ℃, the progress speed of nitriding or carbonitriding does not improve, so that the production cost of multi-component ceramics rises.

In the firing step S2, first, the oxide film formed on the surface of the alloy is reduced. That is,
The surface of the alloy is covered with an oxide film formed by oxidizing a metal constituting the alloy with oxygen in the air.
This oxide film is reduced by a reducing agent to become an active alloy.

When a powdered carbon material is used as a reducing agent,
The powdered carbon material itself is oxidized to CO or CO ₂ by removing oxygen from the oxide film. Since these are both gases, they can be easily and quickly discharged out of the reaction furnace by being accompanied by the atmospheric gas.

When the oxide film is reduced, the surface of the alloy becomes extremely active. Therefore, it is easily nitrided from the surface to the inside. When a powdered carbon material is used as the reducing agent, the surplus powdered carbon material also functions as a C source. That is, in this case, the alloy is carbonitrided from the surface to the inside.

In the firing step S2, the catalyst may be oxidized. When an alkaline earth metal is used as a reducing agent, the alkaline earth metal itself is oxidized by removing oxygen from the oxide, and remains in the multi-component ceramic powder as an oxide. That is, the unreacted reducing agent and catalyst, the oxide of the reducing agent, and the oxide of the catalyst are mixed as impurities in the multi-component ceramic powder obtained in the firing treatment step S2. When a sintered body is manufactured using a multi-component ceramic powder containing these impurities as a raw material, the sintered body may exhibit low hardness.

Then, next, in the acid treatment step S3,
Impurities are separated and removed from the multi-component ceramic powder. Specifically, impurities are eluted by immersing the obtained multi-component ceramic powder in an acid solution.

This acid solution preferably contains hydrofluoric acid or borofluoric acid. These are excellent in the ability to dissolve the above-mentioned impurities, and therefore, the impurities can be efficiently separated and removed from the multi-component ceramic powder.

At this time, some of the metal elements constituting the multi-component ceramic powder may be oxidized.
As described above, the hardness of a sintered body made of a powder in which the proportion of O exceeds 0.5% by weight is reduced. Therefore, the concentration of the acid solution and the immersion time are 0.5% by weight of O.
Is set not to exceed.

After filtration to separate the filtrate and the powder,
By neutralizing the powder and washing it with water, high-purity multi-component ceramic powder is obtained.

The sintered body using the multi-component ceramic powder as a raw material exhibits high hardness because the multi-component ceramic powder is nitrided or carbonitrided from the surface to the inside. Further, since the impurities are removed from the multi-component ceramic powder, the relative density of the sintered body approaches the theoretical density.
For this reason, the sintered body also has excellent strength and toughness.

As described above, by mixing two or more kinds of metal powders, a reducing agent and a catalyst and then performing a calcination treatment in the presence of nitrogen gas, a multi-component ceramic powder can be easily and simply produced. Moreover, the reaction efficiency and the reaction rate are higher than those of the PVD method and the CVD method. For this reason,
The production amount per batch is large, and therefore, the production cost of the sintered body can be reduced.

The multi-component ceramic powder can be used as a suitable raw material for cutting tools such as chips and cutting tools, dies and the like. That is, by sintering the multi-component ceramic powder alone or after molding it together with the metal powder, it is possible to obtain a high-hardness cutting tool, a mold, and the like.

[0065]

EXAMPLES Ti, Al, Zr, Hf, V, Nb, Cr,
W as metal powder, carbon black as reducing agent and C
As a source, Mg as a reducing agent or a catalyst, Mn, Ni
Was mixed as a catalyst at the ratio shown in FIG. 2 (numbers are% by weight). This mixing was performed under conditions where the metals formed an alloy by mechanical alloying.

The alloy in the mixed powder thus obtained was carbonitrided by firing in a pattern shown in FIG. 3 in a nitrogen atmosphere to obtain various composite carbonitride ceramic powders.

Further, the composite carbonitride ceramic powder is immersed in aqua regia or a mixed solution of hydrofluoric acid and nitric acid, and unreacted Mg, Mn, Ni and their oxides are eluted in the acid solution to form a composite. Separated from carbonitride ceramic powder. Then, after sintering the purified composite carbonitride ceramic powder into a sintered body, Vickers hardness of each sintered body was measured. These are Examples 1-28.

For comparison, sintered bodies were manufactured according to Examples 1 to 28 except that no catalyst was added, and the Vickers hardness of each sintered body was measured. These are Comparative Examples 1 to 3.

The Vickers hardness (Hv) of each of the sintered bodies of Examples 1 to 28 and Comparative Examples 1 to 3 is also shown in FIG. From FIG. 2, it is clear that each of the sintered bodies of Examples 1 to 28 has extremely high hardness, and that the hardness of the sintered bodies is extremely low when no catalyst is added.

FIG. 2 shows that Ti-Al-Nb- (C,
It is also understood that the sintered body made of the N) -based ceramic powder has a relatively high hardness. Therefore, with respect to this system, ceramic powders were produced by varying the addition ratio of carbon black, and Hv of a sintered body obtained by sintering the ceramic powders was measured. FIG. 4 is a graph showing the relationship between the addition ratio of carbon black and Hv of the sintered body.
From FIG. 4, it can be seen that, in this system, the addition ratio of carbon black is maximum at 3% by weight, and when it exceeds that, Hv decreases as the addition ratio increases.

The C / N (atomic ratio) in the obtained powder was measured by instrumental analysis. C / N and Hv of sintered body
FIG. 5 is a graph showing the relationship. From FIG. 5, it can be said that in this system, the C / N is preferably less than 1.

Further, C / C, which exhibited the maximum hardness in this system,
After preparing a powder of N ≒ 0.7 to an average particle size of about 2 μm,
Ni was added by 7% by weight and wet-mixed with a ball mill. After press-molding this mixed powder at 150 MPa, it was sintered at 1400 ° C. for 1.5 hours in a nitrogen atmosphere to produce a composite material of Ti—Al—Nb— (C, N) and Ni. . The relative density of this composite was approximately 100%.

When the Rockwell hardness and the transverse rupture strength of this composite material were measured, the values were 93.4 to 93.4, respectively.
94.0 and 3 GPa. These values were higher by 2 points and 1 GPa, respectively, than the cermet composed of TiC, NbC and Ni.

From the above, it can be seen that a sintered body using multi-component ceramic powder as a raw material has higher hardness than a sintered body using binary ceramic such as TiC or TiN as a raw material. it is obvious.

[0075]

As described above, according to the multi-component ceramic powder of the present invention, two or more kinds of metals, N, and C are constituents. For this reason, a sintered body obtained using this powder as a raw material is a sintered body obtained using a binary nitride ceramic powder or a binary carbonitride ceramic powder as a nitride or carbonitride of one kind of metal as a raw material. The effect of exhibiting high hardness as compared with the union is achieved.

Further, according to the method for producing a multi-component ceramic powder according to the present invention, two or more metals are alloyed by mechanical alloying, and after reducing the oxide film formed on the surface of the alloy, nitriding or Carbonitriding is performed. Therefore, the alloy can be surely nitrided or carbonitrided from the surface to the inside thereof, and as a result, the effect of easily and simply obtaining multi-element ceramic powder at low cost can be achieved.

[Brief description of the drawings]

FIG. 1 is a flowchart of a method for producing a multi-component ceramic powder according to the present embodiment.

FIG. 2 is a table showing a mixing ratio of each powder and Vickers hardness when obtaining multi-component ceramic powders as raw materials of sintered bodies of Examples 1 to 28 and Comparative Examples 1 to 3.

FIG. 3 is a firing pattern in a firing process step S2 for obtaining the multi-component ceramic powder.

FIG. 4 is a graph showing the relationship between the addition ratio of carbon black and Hv of a sintered body when obtaining a Ti—Al—Nb— (C, N) ceramic powder.

FIG. 5 is a graph showing a relationship between C / N (atomic ratio) in Ti-Al-Nb- (C, N) -based ceramic powder and Hv of a sintered body.

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Claims (9)

[Claims] 1. Ti, Al, V, Nb, Zr, Hf, M
A multi-component ceramic powder comprising N as at least two metal elements selected from the group consisting of o, Ta, Cr, and W, and N. 2. The multi-component ceramic powder according to claim 1, further comprising C as a constituent. 3. The multi-component ceramic powder according to claim 2, wherein the atomic ratio of C to N is C / N <1. 4. The multi-component ceramic powder according to claim 1, wherein the proportion of O contained as an irreversible impurity is 0.5% by weight or less. Powder. 5. Ti, Al, V, Nb, Zr, Hf, M
a powder of at least two metals selected from the group consisting of o, Ta, Cr, and W, a reducing agent, and a catalyst that promotes nitriding or carbonitriding of the metals are mixed, and the two metals are mechanically combined with each other. Alloying by alloying to form an alloy; and baking the mixed powder containing the alloy in the presence of nitrogen gas to nitride or carbonitride the alloy to form a multi-component ceramic. Characteristic method for producing multi-component ceramic powder. 6. The method according to claim 5, wherein at least one of an alkaline earth metal and a powdered carbon material is used as said reducing agent. 7. The method for producing a multi-component ceramic powder according to claim 6, wherein an addition ratio of said powdered carbon material is 0.1% by weight to 11.6% by weight. 8. The method according to claim 5, wherein a powder of at least one of an alkaline earth metal, a Group VIIA element and a Group VIII element is used as the catalyst. A method for producing a multi-component ceramic powder, comprising: 9. The method according to claim 5, further comprising a step of treating the multi-component ceramic powder with an acid solution. .