JP2997320B2 - Fiber reinforced ceramics - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fiber reinforced ceramic containing a fibrous substance such as a whisker, and more particularly to a ceramic excellent in high toughness and suitable for wear-resistant materials and tool materials.

[0002]

_2. Description of the Related Art Various proposals have been made for increasing the toughness of an alumina (Al ₂ O ₃ ) sintered body due to its drawback of being inferior in toughness while being excellent in wear resistance. For example,
It has been disclosed in Japanese Patent Application Laid-Open Nos. 61-286271 and 62-41 to improve the toughness by blending a fibrous substance typified by silicon carbide (SiC) whiskers with Al ₂ O _3.
776 and the like.

[0003] When such a fiber-reinforced ceramic containing SiC whiskers is used as a cutting tool because SiC itself has a high field hardness and good thermal conductivity, cutting of some super heat-resistant alloys (rough cutting of Inconel 718). ) Shows excellent performance. It has also been proposed to add SiC powder to Al ₂ O ₃ , but it has not improved fracture toughness.

[0004]

SUMMARY OF THE INVENTION Generally, Al ₂ O
Improvement of toughness by adding SiC whiskers to ₃ is usually achieved by adding about 30 to 40% by volume of SiC whiskers.

However, the conventional Al ₂ O ₃ —SiC
Whisker-based materials have a fracture toughness of K1c of 5
It is on the order of MPa · m ^1/2, which is insufficient in properties for use as a tool, and higher toughness is required. To solve such a problem, for example, it is conceivable to further increase the addition amount of SiC whiskers.
When the amount of C whiskers is increased, the sinterability is lowered and the characteristics such as excellent wear resistance of Al ₂ O ₃ are lowered, which is not preferable.

[0006]

The inventor of the present invention has studied the above problems, and as a result, has found that SiC can be used as a toughening material.
When adding whiskers to Al ₂ O ₃ , a matrix containing alumina as a main component contains a predetermined amount of a boron-containing metal compound containing an AlBO-based needle-like substance and a metal boride as essential components, and MgO or the like. It has been found that by including a predetermined amount of the sintering aid, a fiber-reinforced ceramic having high toughness and hardness can be obtained.

That is, the fiber reinforced ceramics of the present invention comprises:
An AlBO-based acicular substance containing Al ₂ O ₃ as a main component and containing aluminum, boron and oxygen, and a boron-containing metal compound containing a metal boride as an essential component in a ratio of 0.5 to 10% by weight. , MgO, CaO, SiO ₂ and at least one element selected from the group 3a element oxides of the periodic table.
In a matrix containing 0.02 to 8% by weight of seeds, silicon carbide (SiC) whiskers are contained in a total amount of 25 to 4%.
It is characterized by being added at a ratio of 0% by volume.

[0008] The fiber reinforced ceramics of the present invention comprises Al ₂
It is composed of a matrix component mainly composed of O ₃ and a SiC whisker component. According to the present invention, the matrix contains 0.5 to 10% by weight of a boron-containing metal compound.
In the proportion of Such boron-containing metal compounds include AlB ₁₂ , ZrB ₂ , TiB ₂ , TaB, WB, N
metal borides such as bB ₂ and LaB ₆ , and Al ₁₈ B ₄ O ₃₃
For example, boric acids containing aluminum, boron and oxygen are used. As metal borides, AlB ₁₂ , ZrB ₂ , TiB ₂ , WB, N
bB ₂ is desirable.

In particular, among boric acids containing aluminum, boron and oxygen, there is a boric acid which itself has a needle-like shape (hereinafter referred to as an AlBO-based needle-like substance). Since it may grow, it contributes to improvement in toughness together with SiC whiskers.
Specifically, it is desirable to be composed of acicular particles having an aspect ratio of 1.5 or more. The addition of the acicular particles greatly improves the toughness of the sintered body while maintaining the wear resistance of the matrix itself.

The reason why the amount of the boron-containing metal compound is limited to the above-mentioned range is that if the amount is less than 0.5% by weight, the toughness and hardness are not improved. descend.

On the other hand, the SiC component is composed of acicular particles, has the function of suppressing the grain growth of the Al ₂ O ₃ component during sintering, and has the effect of increasing the strength of the sintered body itself. This SiC component is dispersed and contained at a rate of 25 to 40% by volume. Here, the amount of SiC is limited to the above range. When the amount is less than 25% by volume, the effect of suppressing grain growth is small and the strength of the sintered body is reduced, and when it exceeds 40% by volume, the sinterability is reduced. Therefore, it becomes difficult to obtain a high-density sintered body.

Further, according to the present invention, the above Al ₂ O ₃
-A sintering aid is blended to improve the sinterability of the SiC whisker-based material. As the sintering aid used, A
MgO, CaO, S known as a sintering aid for l ₂ O ₃
iO ₂ and Periodic Table Group 3a elements oxides. These auxiliaries are used at a ratio of 0.02 to 8% by weight, preferably 0.5 to 5% by weight based on the total amount. In addition, Yb, Nd, Er, Ce, Sm, Y, Gd, Dy, and La are particularly exemplified as the Group 3a element of the periodic table.

In producing the fiber reinforced ceramics of the present invention, a boron-containing metal compound powder containing alumina powder, an AlBO-based acicular substance, and a metal boride as essential components;
The C whiskers and the sintering aid are mixed in the ratio described above. At this time, the compounded SiC whiskers themselves are made of single crystal or polycrystalline, and have an average diameter of 2 μm or less,
In particular, it is preferably 0.5 to 1.0 μm, and the average of the aspect ratio represented by the major axis / minor axis is 3 to 100, particularly 10 to 10 μm.
50 are used. When the average diameter is 2 μm or less, the grain growth during firing does not become excessive, and high bending strength can be maintained. On the other hand, when the average diameter is larger than 2 μm, it becomes difficult to control the grain growth during firing, and the strength and toughness are increased. Both tend to decrease. On the other hand, if the average of the aspect ratios is less than 3, the effect of fiber reinforcement is small and the toughness is reduced, and if it is more than 100, the handling of the raw materials is difficult, and uniform dispersion is not possible, so that the toughness tends to be reduced.

The AlBO-based acicular substance has an average diameter of preferably 2 μm or less, more preferably 0.2 to 0.7 μm, and preferably has an aspect ratio of 3 to 100, particularly 10 to 50, in order to increase the effect of suppressing grain growth. Things are used. AlB
By using the O-based acicular material, the toughness of the sintered body is improved even when the amount of the AlBO-based acicular material is small due to the synergistic effect of the AlBO-based acicular crystal and the SiC whisker.

The mixture of each of the above-mentioned raw materials is formed into an arbitrary shape by a desired forming means, for example, a die press, a cold isostatic press, an extrusion molding or the like, and then fired.

For firing, a normal firing method, a hot press method, a hot isostatic firing method, or the like is applied. The sintering may be performed at a temperature of 1450 to 1850 ° C. in a reducing atmosphere in which an inert gas such as Ar or He or carbon is present and a pressurized or reduced pressure atmosphere for 0.5 to 6.0 hours. In order to obtain a sintered body, a sintered body having a relative density of 96% or more is prepared by ordinary firing and hot pressing, and then hot isostatic firing is performed under a high pressure of 500 atm or more.

[0017]

EXAMPLE An Al ₂ O ₃ powder having an average particle size of 1 μm or less and a purity of 99.9% or more and various metal compounds shown in Table 1 were weighed in predetermined amounts, and then mixed and pulverized in an attrition mill for 12 hours.
This mixed powder has an average particle size of 0.8 μm and an aspect ratio of 30.
~ 50 SiC whiskers were added in the amounts shown in Table 1, sealed in a nylon pot with nylon balls, and mixed for 12 hours on a rotary mill. The slurry after mixing was dried to obtain a raw material for hot pressing. Note that acicular aluminum borate having an aspect ratio of 30 to 50 was used as the AlBO-based acicular substance.

This raw material is filled in a carbon mold and subjected to 300 to 500 kg / mm for 1 hour under the conditions shown in Tables 1 and 2.
Hot press baking was performed at a pressure of ² to prepare a bending test piece based on JIS.

Each of the obtained samples was polished and subjected to JIS1601.
K1c was measured by IF method after polishing to three-point bending strength based on the above, Vickers hardness and mirror surface. The results are shown in Tables 3 and 4.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

[Table 3]

[0023]

[Table 4]

According to Tables 1 to 4, samples Nos. 1, 2 and 10 to which no boride was added showed no improvement in transverse rupture strength and toughness, whereas samples Nos. 5 to 7 did not. Is 0.22% by weight or more of boride and 0.02% of AlBO needles.
When the weight% or more remained, the bending strength and toughness were improved. In sample No. 4, the bending strength was improved, but the sinterability was reduced due to the small amount of auxiliary agent, and fine voids remained, and no improvement in toughness was observed. In the sintered body sample No. 8 in which the amount of the boride exceeds 10% by weight, the effect of adding the SiC whiskers could not be sufficiently exhibited, resulting in deterioration of properties such as bending strength.

As shown in sample No. 9, the characteristics are improved in the sintered body of the present invention even if the addition ratio of the AlBO needle-like substance of the needle-like particles to the other metal boride is not 1: 1. : 1
At that time, remarkable high strength and improvement in toughness were observed. Particularly, in sample No. 7, the characteristics (hardness: 18.0 GPa, toughness: 5.0MPa) of a general Al ₂ O ₃ —SiC whisker-based sintered body were obtained.
a.m ^1/2 or less), and has a toughness of 2.0M with respect to the sample No. 10 in which the whisker amount is about 10% larger.
Pa · m ^1/2 also improved. In sample No. 16, Si
The C content was small, the whisker pullout and crack deflection were insufficient, and the characteristics were low.

As described above, all of the samples within the scope of the present invention are sintered bodies having excellent properties in both hardness and toughness, with a flexural strength of 800 MPa or more, a toughness of 5.8 MPa · m ^1/2 or more, and a Vickers hardness. 18.0 GPa or more was achieved.

[0027]

As described above in detail, according to the present invention, AlB is contained in a matrix containing alumina as a main component.
A predetermined amount of a boron-containing metal compound containing an O-based acicular substance and a metal boride as essential components, a predetermined amount of a sintering aid such as MgO, and a predetermined amount of SiC whiskers are added. Thus, high toughness and high strength can be achieved, which can further expand the field of wear-resistant materials and the range of application as a material for various large-sized industrial machine parts including tool materials.

Claims (1)

(57) [Claims] 1. A boron-containing metal compound containing alumina (Al ₂ O ₃ ) as a main component, an AlBO-based acicular substance containing aluminum, boron and oxygen, and a metal boride as essential components in an amount of 0.5 to 0.5. 10% by weight and Mg
Silicon carbide (SiC) is contained in a matrix containing at least one selected from the group consisting of O, CaO, SiO ₂ and an oxide of a Group 3a element of the periodic table at a ratio of 0.02 to 8% by weight.
A fiber-reinforced ceramic, wherein whiskers are added at a ratio of 25 to 40% by volume based on the total amount.