JPS6148484A - Zrb2 base composite sintered body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a ZrB2 (zirconium diboride) sintered body.

In general, metal boride ceramics have the characteristics of high melting point, high hardness, high strength, and high corrosion resistance, and have traditionally been used as cutting tools and heat engine parts materials, but although they have not been put into practical use yet. Most of them are titanium borides, and the reality is that zirconium borides are hardly ever put into practical use.

zrB of the present invention! Composite sintered bodies have excellent characteristics such as high melting point, high strength, high corrosion resistance, high hardness, electrical conductivity, and oxidation resistance, so they can be used as high-temperature corrosion-resistant parts, mechanical parts, heating elements, electrodes, crucibles for induction furnaces, etc. It is a material that can be used widely.

(Prior Art) Currently, there are almost no ZrB2 composite sintered bodies that are in widespread practical use, but various ones have been proposed in patents and the like.

That is, silicides such as Mo811, Tag,
Nitrides such as HfN and Bli, oxides such as ZrO2, carbides such as 810 and B2O, and various metals are known.

(Problems to be solved by the invention) For example, regarding silicides, ZrB is disclosed in Japanese Patent Publication No. 3B-6098
lz also Mo1ll in U.S. Patent No. 3,705,112.
However, these S1-based compounds melt or decompose during sintering in a high-temperature atmosphere, resulting in a porous structure and large crystal grain growth, resulting in poor strength and corrosion resistance. The oxidation resistance is often insufficient, and the oxidation resistance is also less than S10. However, these subcomponents alone are not sufficient for use in air.

Next, regarding nitrides, TaN disclosed in U.S. Patent No. 3,305,374 is used as a high hardness material, and ZrBz,
TIB! It is added to materials such as tool materials and decorative materials, and is excellent in terms of high hardness and high strength, but when used in high-temperature oxidizing atmospheres such as high-temperature corrosion-resistant parts, heating elements, electrodes, induction furnace crucibles, etc. It is not sufficient in terms of oxidation resistance, spalling resistance, corrosion resistance, etc.

Next, regarding carbides, U.S. Patent No. 3,775,157 and 8
101 US Pat. No. 5,325,500 discloses B, C, and StC, but in the US: Patent No. 377,513.
Addition of only StC of 7 is insufficient in terms of oxidation resistance and sb
Also No. 3525300 Mo1312-)-B4C, Mo
811+ SIC! +14 (Mo8 lz for addition of 3
has a melting point lower than the sintering temperature, so it melts during sintering, decomposes, promotes grain growth, and makes the structure porous, making it difficult to increase density. Therefore, it has not yet reached the level where it is a material particularly required for high-temperature structural members.

In view of these points, the present inventors added SIC-)-B40 without adding MO8Iz first, or added 5tc-B40 without adding MO8Iz first.
) - Z that was improved by studying the one with the addition of BH
We succeeded in obtaining an rB2 sintered body. Although these have made it possible to put ZrBz sintered bodies into practical use, it is also true that there remains room for improvement. For example, the addition system of jlO + BN was satisfactory in that spalling resistance could be improved by increasing the BN content, but by adding BN, which is difficult to sinter, dense sintered bodies were It is difficult to obtain such properties, and the strength and hardness are not necessarily sufficient, and therefore, it cannot be said to be suitable for applications such as high-temperature, high-strength members.

In addition, although the 5tc-14c additive system was satisfactory in terms of strength, hardness, and oxidation resistance, it was not necessarily sufficient in terms of spalling resistance and corrosion resistance, and therefore it was used for spalling resistance such as steel. , it could not be said to be suitable for uses such as corrosion-resistant members.

In view of these points, we are conducting research to overcome the conventional problems with ZrB2 sintered bodies, which have excellent properties but are not fully utilized and are actually used for only extremely limited applications. As a result of this progress, we have achieved a combination of various properties such as excellent high density, high strength, oxidation resistance, corrosion resistance, and even spalling resistance, and in some cases, we have significantly improved the strength of this type of composite. They succeeded in developing a sintered body.

(Means for solving the problem) That is, the present invention uses ZrB1 as the main component, and contains 1 to 1
5ch stc, s~20% B, O and 3~25ch B
The gist of this invention is a high-strength ZrB dual composite sintered body characterized by containing M2.

ZrB1 used in the present invention can be obtained, for example, by reacting a mixture of zirconium oxide, boron oxide, and carbon at high temperature, and it is preferable to use ZrB1 with as high purity as possible for producing the present sintered body, and It is preferable to use a powder whose diameter is as small as possible.

Specifically, purity? ? - or more, average particle size 10 μm, especially 1
This is less than μm.

Also, SiC exists as a subcomponent! , 33. c.
As for BN and BN, it is sufficient that they are present in a predetermined amount as such compounds in the form of a sintered body, so they may be blended in any form as starting materials;
5IC9B4When using raw materials other than C and BN, special consideration is required at the sintering stage, so S and IC are usually used as blended raw materials.

It is best to adjust them as B4C and BM.

It is preferable that these Sac, B40 and BN raw materials have as high a purity as possible. 9 inches or more is better.

The raw material mixture is usually prepared by uniformly mixing these three types of fine powders, but the same effect can be obtained by ultrafinely pulverizing them for the purpose of pulverizing and mixing. Generally, the particle size of the mixed raw material is preferably 10 μm or less, and preferably the average particle size is sufficiently adjusted to 1 μm or less.

It is appropriate to use a StC pole for these pulverizations.

The sintered body of the present invention can be obtained by filling a graphite mold with these mixtures and hot-pressing the mixture in vacuum or in a neutral or reducing atmosphere such as argon, helium, or carbon oxide, or molding the above-mentioned mixture with a rubber press. It can be obtained by, for example, baking at normal pressure. The firing temperature is 1800~230℃.
0°C, the firing time depends on the size of the sample, etc., but is usually c1.
Approximately 5 to 5 hours is appropriate.

aSa (silicon carbide) in the sintered body of the present invention
It is necessary to have at least 1% by weight (the same applies hereafter), but if it is less than that, the oxidation resistance will be poor! On the other hand, if the number is too large, the effects of spall resistance and high corrosion resistance will not be exhibited, so it is undesirable to limit the number to a maximum of 15. ~10chi.

B and C (boron carbide) need to be at least 5 cm, but this is because if it is less than that, it will be difficult to increase the density, while if it is too large, the heat resistance will decrease, so it is undesirable and the maximum It is necessary to limit the length to 20 inches, and preferably 7 to 15 inches. At least 3 strands of BN (boron nitride) are required, but if it is less than that, the spall-resistant and high corrosion-resistant characteristics will not be fully exhibited, and if it is too much, it will be difficult to sinter, making it difficult to obtain a high-density product. For this reason, it is undesirable to limit the number to a maximum of 25 inches, and preferably 5 to 20 inches.

In addition, the total amount of StC, B4C, and BM is required to be at least 9, and it is possible to have a maximum of 60, but if the content is too large, Zr
Since this impairs the properties of B2, the appropriate content is usually 15 to 50 g.

However, the sintered body of the present invention consists of components other than these subcomponents, that is, the remainder, which essentially consists of ZrB2, but components other than ZrBz, such as Ti, may be added to the extent that the characteristics of ZrB2 are not impaired.
Of course, there is no problem even if a small amount of B, etc. is included, but it is desirable to keep the amount as small as possible.

In addition, other components may of course be included as subcomponents as long as they do not essentially impair the intended effects of the sintered body of the present invention, but they must be kept in as small a quantity as possible, including unavoidable impurities. It is.

The structure of the sintered body of the present invention consists of grains with an average grain size of several μm.
The rB2 microcrystals are uniformly dispersed, and the subcomponents BN, B4C,
It had a dense tissue structure in which SIO was distributed.

In addition, in tissues containing 15% or more of BN, BN
Because it has lubricity, BN itself consists of a plate-like structure with a few μm of poles and about 8 μm in length, and the main component, ZrB,
z Existed around fine crystal grains.

The other subcomponent (B4C!, 810) remained uniformly dispersed between the ZrB1 crystal grains as almost granular microcrystals.

(Effects of the Invention) The thus obtained sintered body of the present invention has high density, high hardness, particularly high strength, and is an electrically conductive sintered body with excellent corrosion resistance and spalling resistance. It can be preferably applied to structural members, high-temperature corrosion-resistant members, heating elements, etc., and can also be used in various other applications that exhibit the characteristics of the ZrB2 sintered body, so its practical value is great.

(Example 1) 0 Example 1 ZrB2 powder (purity 99+) B4C powder (purity 99+)
% or more), BN powder (purity of 99% or more), and Bte powder (purity of 99% or more) were thoroughly mixed and pulverized using a bot mill and an StC pole in an ethanol solvent.
It was ground and mixed for days. The obtained powder was thoroughly dried by removing alcohol using an evaporator to obtain a powder having an average particle size α of 15 μm. 2000 kg/kg of this powder was produced using a rubber press.
It was molded using A11 and fired under normal pressure at 2300° C. for 2 hours in an argon atmosphere. The properties of the sintered body thus obtained are shown in Table 1.

Example 3 The same ZrBz powder, ssc powder, B, 0 powder, and BM powder as in Example 1 were mixed and ground in a pot mill for 3 days using a StC ball in an ethanol solvent.

The alcohol was sufficiently removed from this powder using an evaporator and the powder was dried to obtain a powder having an average particle size Q of 15 μm. This powder was filled into a graphite mold and heated at 2050° C. for 30 minutes while pressurized to 350 kg/aF in an argon atmosphere.

Table 1 shows the properties of the sintered body thus obtained.

0 Examples 2 and 4 to 6 and Comparative Examples 7 to 12!
Table 1 shows the results for each sample obtained by adjusting predetermined mixed raw materials according to Examples 1 and 5 and processing them under predetermined firing conditions.

Note 1) Oxidation resistance is under oxidizing atmosphere, 1000℃ x 12 hours
The degree of increase rate of mold needles under the conditions of The bending strength of a sample heated and rapidly cooled in water is measured, and the processing temperature at which the strength suddenly decreases is expressed as ΔT.

Claims (1)

[Scope of Claims] 1. ZrB_2 composite characterized by containing ZrB_2 as a main component and containing 1 to 15% SiC, 5 to 20% B_4C, and 3 to 25% BN, respectively, by weight%. Sintered body. 2. The sintered body according to claim 1, wherein the total amount of SiC, B_4C, and BN is 15 to 50%.