JPS6337068B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a ZrB ₂ (zirconium diboride) composite 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. The ZrB _two- component sintered body of the present invention has excellent characteristics such as high melting point, high strength, high corrosion resistance, high hardness, electrical conductivity, and oxidation resistance, so it can be used as a high-temperature corrosion-resistant member, a mechanical member, etc.
It is a material that can be widely used for heating element electrodes, induction furnace crucibles, etc. (Prior Art) There are currently very few ZrB _2- quality 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 MoSi 2 ,}
Nitrides such as TaN and HfN, oxides such as ZrO ₂ ,
Carbides such as SiC and B ₄ C, and various metals are known. (Problems to be solved by the invention) For example, regarding silicides, the Japanese Patent Publication No. 38-6098
ZrSi ₂ and MoSi ₂ are disclosed in U.S. Patent No. 3705112, but these Si-based compounds melt or decompose during sintering in a high-temperature atmosphere, resulting in a porous structure that prevents the growth of crystal grains. Often larger,
Therefore, the strength and corrosion resistance are often insufficient, and although the oxidation resistance is expected to be effective as a SiO ₂ film, these subcomponents alone are not sufficient for use in air. Next, regarding nitrides, U.S. Patent No. 3305374
Although TaN is excellent in terms of high hardness and high strength, it has poor oxidation resistance when used in high-temperature oxidizing atmospheres such as high-temperature corrosion-resistant parts, heating elements, electrodes, and induction furnace crucibles. It is not sufficient in terms of durability, spall resistance, corrosion resistance, etc. Next, regarding carbides, refer to U.S. Patent No. 3775137.
Although SiC has been disclosed, SiC alone is insufficient in terms of oxidation resistance, and US Patent No.
MoSi ₂ +B ₄ C disclosed in 3325300 or
When MoSi ₂ + SiC + B ₄ C is added, MoSi ₂ has a lower melting point than the sintering temperature, so it may melt and decompose during sintering, or
Because it promotes grain growth and makes the structure porous, it is difficult to achieve high density, and therefore its oxidation resistance is not sufficient. US Patent No. 3,325,300 also discloses SiC and/or B ₄ C, but this patent is a ZrB ₂ - MoSi ₂ system with these additional components added, essentially MoSi Sintered bodies containing Si-based compounds such as ₂ are difficult to become sufficiently dense and do not have sufficient strength or oxidation resistance. In view of these points, we are conducting research to overcome the conventional problems with ZrB _2- material sintered bodies, which have excellent properties but are not fully utilized and are actually used for only extremely limited applications. As a result of our efforts, we succeeded in developing a sintered body that has various properties such as high density, high strength, oxidation resistance, corrosion resistance, and even spalling resistance, and has significantly improved some of its properties. It is. (Means for solving the problem) That is, the present invention contains at least 1% or more by weight of each of SiC and B ₄ C as subcomponents, the total amount of these is 2 to 50% by weight, and the remainder is substantially consisting of _ZrB2 , which can be replaced by up to 10% by weight of _TiB2 .
The main feature is a ZrB _2- quality sintered body. The ZrB ₂ used in the present invention can be obtained, for example, by reacting a mixture of zirconium oxide, boron oxide, and carbon at high temperatures, and it is preferable to use ZrB 2 with the highest possible purity for producing the present sintered body.
Further, a powder having a particle size as small as possible is preferable. Specifically, it has a purity of 99% or more and an average particle diameter of 10 μm, particularly 1 μm or less. Furthermore, as for SiC and B ₄ C, which are present as subcomponents, it is sufficient that they are present in a predetermined amount as such compounds in the sintered body, so they may be blended in any form as starting materials. However, if raw materials other than SiC and B ₄ C are used, special consideration is required at the sintering stage, so it is better to prepare them as SiC and B ₄ C as the usual blended raw materials. The raw materials for SiC and B ₄ C are preferably as pure as possible, preferably 99% or higher. 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 10μm or less, preferably the average particle size.
It is necessary to sufficiently adjust the thickness to 1 μm or less. The sintered body of the present invention can be produced by filling a graphite mold with these mixtures and hot pressing in vacuum or in a neutral or reducing atmosphere such as argon, helium, carbon monoxide, etc., or by pressing the above mixture with a rubber press. It is possible to sinter the molded product either by normal pressure firing or by firing under pressure of about 50 to 2000 kg/cm ² . Note that the firing temperature is suitably 1600 to 2200°C and the firing time is approximately 30 minutes to 1 hour. The proportion of the subcomponents in the sintered body of the present invention is 2 to 50% by weight (the same applies hereinafter),
Although the remainder is substantially composed of ZrB ₂ , a small amount of this ZrB ₂ may be replaced with other components such as TiB ₂ to the extent that the characteristics of ZrB ₂ are not impaired. Specifically, up to 10 weights of ZrB ₂ can be replaced with TiB ₂ . Note that it is necessary to limit the amount of subcomponents other than SiC and B ₄ C to as small a quantity as possible, excluding inevitable impurities, especially since the presence of Si-based compounds is extremely undesirable. Specifically, ZrB ₂ (including TiB ₂ ) and SiC
Components other than the total amount of B ₄ C must be kept at 3% by weight or less. At least 1% or more of each of B ₄ C and SiC as subcomponents is required, but if B ₄ C is less than 1%, it is difficult to achieve high density, and the properties of oxidation resistance and high corrosion resistance are fully exhibited. This is because if SiC is less than 1%, oxidation resistance is insufficient and it becomes difficult to achieve high density. It is not clear why the presence of SiC improves the oxidation resistance of this sintered body, but when used in combination with B ₄ C, a highly viscous B ₂ O ₃ -SiO ₂ film forms during use. This is thought to be due to the formation of the sintered body, and this fact indicates that the present sintered body can be used sufficiently for uses such as heating elements. On the other hand, B ₄ C and SiC can each be present in a sintered body up to about half the amount, but if B ₄ C exceeds 50%, oxidation resistance decreases.
If SiC exceeds 50%, the spalling resistance and high corrosion resistance effects will no longer be exhibited, which is undesirable, and in any case, the characteristics of the ZrB ₂ quality will be essentially impaired, including loss of heat resistance. Therefore, B ₄ C and SiC
It is necessary to limit the total amount to 50%. Further, within these ranges, a more desirable range is for each of SiC and B ₄ C to be 5% or more, and the total amount to be 10% or more, preferably 20% or more. Moreover, the ratio of SiC and B ₄ C is 10 to 60% for the former and 90 to 40% for the latter. The sintered body of the present invention is structurally ZrB ₂
ZrB ₂ is a dense substance whose main component is crystal, with B ₄ C and SiC strongly bonded between them. It's on. Specifically, ZrB ₂ in the sintered body of the present invention
Most of the crystals exist as particles with a particle size of 10 μm or less. (Effects of the Invention) As described above, the sintered body of the present invention thus obtained has high density, oxidation resistance, spalling resistance,
It is a dense sintered body with high strength, excellent corrosion resistance, and conductivity, making it ideal for high-temperature corrosion-resistant parts used in air, heating elements, crucibles, etc., as well as other mechanical parts materials, tools, etc. is also applicable
It can be used for various purposes that exhibit the characteristics of the ZrB ₂ -quality sintered body, and its practical value is great. (Example) Γ Example 1 85 parts by weight of ZrB ₂ powder (99% purity or higher), 10 parts of B ₄ C powder (99% purity), and 5 parts of SiC powder (99% purity) were thoroughly mixed and ground using a pot mill. The mixture was ground and mixed for 3 days using SiC balls in an ethanol solvent. The obtained powder was thoroughly dried by removing alcohol with an evaporator to obtain a powder with an average particle size of 0.15μ. This powder was filled into a graphite mold and heated at 2000° C. for 30 minutes under a pressure of 350 kg/cm ² in an argon atmosphere to obtain a sintered body. The properties of the obtained sintered body are relative density 98% bending strength
78Kg/mm ² , No change in oxidation resistance (Note 1), Hardness HV
(Note 2) It was 2100Kg/ ^mm2 . In addition, the size of most of the ZrB ₂ crystals in this sintered body was less than 5 μm, and the analytical value was almost the same as the sample composition ratio. (SiC contamination from the grinding balls was approximately 2%) Γ Examples 2 to 6, 11 to 13 and Comparative Examples 1 to 3: Sintered bodies were obtained in the same manner as in Example 1. Γ Examples 7 to 10 are ZrB ₂ similar to Example 1,
A predetermined amount of B ₄ C and SiC powder was molded at 2000 kg/cm ² using a rubber press, and this was sintered under specific sintering conditions (argon atmosphere, 1 hour). The characteristics of each sintered body are as follows.

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Claims (1)

[Scope of Claims] 1 Contains at least 1% or more by weight of each of SiC and B ₄ C as subcomponents, and the total amount of these is 2 to 50%.
% by weight, with the remainder substantially up to 10% by weight
ZrB binary composite sintered body consisting of ZrB ₂ that can be replaced _with TiB ₂ . 2. The sintered body according to claim 1, wherein the total amount of SiC and B ₄ C is 10% by weight or more. 3. The sintered body according to claim 2, wherein the total amount of SiC and B ₄ C is 20% by weight or more. 4 ZrB _{2 and ZrB 2} can be replaced by up to 10% by weight of TiB ₂
The sintered body according to any one of claims 1 to 3, wherein the content of components other than the total amount of SiC and B ₄ C is 3% by weight or less. 5. The sintered body according to any one of claims 2 to 4, wherein each of SiC and B ₄ C is 5% by weight or more. 6. The sintered body according to claim 1 or 5, wherein the proportion of SiC and _B4C is 10 to 60% by weight for the former and 90 to 40% by weight for the latter. 7. The sintered body according to claim 1, wherein most of the ZrB ₂ crystals have a grain size of 10 μm or less.