JPS6339543B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a ZrB ₂ (zirconia 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. Among large titanium borides, zirconium borides have hardly ever been put to 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 elements, electrodes, crucibles for induction furnaces, 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, Hf, N, and BN, oxides such as ZrB 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 have a porous structure that dissolves or decomposes during sintering in a high-temperature atmosphere, and crystal grain growth. As a result, the strength and corrosion resistance are often insufficient, and the oxidation resistance is expected to be effective as a SiO ₂ film, but with these subcomponents alone, it is not suitable for use in air. not enough. Next, regarding nitrides, U.S. Patent No. 3305374
TaN disclosed in
It is added to ZrB ₂ , TiB ₂ , etc. and applied to tool materials and decorative materials, and is excellent in terms of high hardness and high strength. When used in an atmosphere, oxidation resistance, spalling resistance, corrosion resistance, etc. are not sufficient. Next, regarding carbides, refer to U.S. Patent No. 3775137.
SiC, B ₄ C and SiC are disclosed in U.S. Patent No. 3,325,300, but the addition of only SiC as in U.S. Pat. No. 3,775,137 is insufficient in terms of oxidation resistance, and
When adding MoSi ₂ + B ₄ C or MoSi ₂ + SiC + B ₄ C in 3325300, MoSi ₂ has a low melting point depending on the sintering temperature, and it melts during sintering, decomposing, promoting grain growth, and making the structure porous. Therefore, it is difficult to increase the density, and the oxidation resistance is not sufficient. Furthermore, the more important point in these proposals is that nothing that is fully satisfactory in terms of strength has been achieved. 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 higher density, higher strength, and higher hardness than conventional products, and also has various performances that can be put to practical use in terms of corrosion resistance, spalling resistance, oxidation resistance, etc. This is what I did. One of them is one that contains a certain amount of SiC and TiC as subcomponents, which are specially blended to have particularly high density, high hardness, and sufficient strength. . However, as the study progressed,
Such sintered bodies are not necessarily sufficient for applications that require strong oxidation resistance, but on the other hand, there is also a deep-rooted demand for superior strength, and there has been a desire for sintered bodies with even better performance. is also true. As a result of various studies to meet these demands, the present inventors have developed a sintered body that can improve the performance of this type of composite sintered body, especially further improve its strength and oxidation resistance. It was successful. (Means for solving the problem) That is, the present invention has ZrB ₂ as a main component, 1 to 15% SiC, 3 to 35% TiC (titanium carbide), and 2 to 30% B ₄ C by weight. The gist is a high-strength ZrB _dual- composite sintered body characterized by containing (boron carbide). 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 for the production of the present sintered body, it is preferable that the purity is as high as possible, and the particle size is also Powders as small as possible are preferred. Specifically, it has a purity of 99% or more and an average particle size of 10 μm or less, especially 1 μm or less. SiC, B ₄ C and
Regarding TiC, it is sufficient that it exists in a predetermined amount as such a compound in the form of a sintered body, so it may be blended in any form as a starting material, but other than SiC, B ₄ C and TiC When using these raw materials, special consideration is required in the sintering stage, so it is best to prepare them as SiC, B ₄ C, and TiC as the usual blended raw materials. The raw materials for SiC, B ₄ C and TiC are preferably as high in purity as possible, usually at least 99%. 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. In general, the particle size of the mixed raw material is preferably 10μm or less, preferably a refundable particle size.
It is necessary to sufficiently adjust the thickness to 1 μm or less. It is appropriate to use SiC balls 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 monoxide, or by rubber-press molding the mixture. It can be obtained by, for example, baking under normal pressure. Note that the firing temperature is 1700 to 2200°C, and the firing time is usually about 0.5 to 3 hours, although it depends on the size of the sample. In the sintered body of the present invention, SiC is required to be at least 1% by weight (the same applies hereinafter), but if it is less than that, even if B ₄ C is added, oxidation resistance will not be sufficient and it will be difficult to achieve high density. On the other hand, if it is too large, it is not preferable because the corrosion resistance and heat resistance, which are the inherent characteristics of ZrB ₂ , will deteriorate, so it is necessary to limit it to a maximum of 15%, and preferably 3 to 10%. Also, TiC must be at least 3%, but if it is less than that, a dense sintered body cannot be obtained and B ₄ C
This is because even if it is used in combination with B 4 C, the desired sufficient strength cannot be obtained.On the other hand, if it is added too much, properties such as corrosion resistance and oxidation resistance will be impaired.In particular, the purpose of improving oxidation resistance by blending B ₄ C In order to achieve this, it is necessary to keep it to a maximum of 35%, preferably 5 to 20%. In addition, B ₄ C is required to be at least 3%, because if it is less than that, the strength of this type of composition will not be improved enough, and the oxidation resistance will not improve, but if it is too high, the corrosion resistance and heat resistance will be reduced. max.
It is necessary to keep it at 30%, preferably 5%.
~20%. In addition, these SiC, TiC and B ₄ C must be present in a total amount of at least 7% in the sintered body, preferably 15% or more,
This is because if these subcomponents are too small, oxidation resistance will not be sufficient, and a dense sintered body will not be obtained, so that the desired sufficient strength will not be obtained. In addition, if the total amount of these subcomponents is too large, it will essentially impair the characteristics of _ZrB2 , so the maximum amount is 60%, usually 50%, and preferably 40%.
It is best to keep it to within. The sintered body of the present invention consists of components other than these subcomponents, that is, the remainder, which essentially consists of ZrB ₂ , but components other than ZrB 2 , such as TiB ₂ , may be added to the extent that the characteristics of the ZrB ₂ quality are not impaired _. Of course, there is no problem even if it is contained in a small amount, but it is desirable to keep the amount as small as possible. Furthermore, there is of course no problem in including other components as subcomponents as long as they do not essentially impair the intended effects of the sintered body of the present invention, but they should be kept in as small a quantity as possible, including unavoidable impurities. is necessary. The structure of the sintered body of the present invention is extremely dense in which fine crystals of ZrB ₂ are uniformly dispersed, and the subcomponent is composed of a good structure distributed between the fine crystal grains of ZrB ₂ . Specifically, most of the ZrB ₂ crystals in the sintered body of the present invention exist with a grain size of 10 μm or less. (Effects of the Invention) The thus obtained sintered body of the present invention has high density, high hardness, especially high strength, and is a conductive sintered body with excellent oxidation resistance, so it can be heated at high temperatures. It can be preferably applied to structural members, high-temperature corrosion-resistant parts, industrial machine parts, heating elements, etc., and can be used in a variety of applications that exhibit the characteristics of the ZrB _dual -composite sintered body. The value is enormous. (Example) Example 1 ZrB ₂ powder (purity 99% or more), TiC powder (purity 99% or more)
% or more), B ₄ C powder (purity of 99% or more), and SiC powder (purity of 99% or more) were pulverized and mixed in a pot mill for 3 days using SiC balls in an ethanol solvent in order to thoroughly mix and pulverize them. 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 2200°C for 60 minutes in an argon atmosphere to obtain a sintered body. The physical properties of the obtained sintered body are shown in Table 1 as sample No. 1. In addition, the structure of this sintered body is good, with ZrB ₂ microcrystals, most of which have a grain size of 5 μm or less, uniformly dispersed, and surrounding the ZrB ₂ crystals are TiC, SiC, and B as subcomponents. It had an extremely dense microstructure in which _4C crystals were present and strongly bonded. Examples 2 and 6 and Comparative Examples 7 to 11 Table 1 shows the results for each sample obtained by preparing predetermined mixed raw materials in substantially the same manner as in Example 1 and treating them under predetermined firing conditions.

【table】

【table】

Claims (1)

[Claims] 1 ZrB ₂ as the main component, 1 to 15% by weight
A high-strength ZrB _binary sintered body characterized by containing SiC, 3-35% TiC and 3-30% _B4C . 2. The sintered body according to claim 1, wherein the total amount of SiC, TiC, and _B4C is 7 to 60%. 3. The sintered body according to claim 2, wherein the total amount of SiC, TiC, and _B4C is 15 to 50%.