JPS6337066B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a ZrB ₂ (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. The _ZrB2 composite sintered body of the present invention has a high melting point, high strength,
It has excellent characteristics such as high corrosion resistance, high hardness, electrical conductivity, and oxidation resistance, so it is a material that can be widely used for high-temperature corrosion-resistant parts, mechanical parts, 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 patents have been proposed. That is, silicides such _{as MoSi 2 ,}
Nitrides such as TaN, HfN, and BN, 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 porous structures and slow crystal grain growth. 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
TaN disclosed in ZrB ₂ as a high hardness material,
Added to TiB ₂ , etc., and applied to tool materials and decorative materials, it is excellent in terms of high hardness and high strength, but is used in high-temperature oxidizing atmospheres such as high-temperature corrosion-resistant parts, heating elements, electrodes, induction furnace crucibles, etc. In this case, the 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.
In addition of MoSi ₂ + B ₄ C and MoSi ₂ + SiC + B ₄ C in No. 3325300, MoSi ₂ has a lower melting point than the sintering temperature and melts during sintering, decomposing and promoting grain growth, making the structure porous. Therefore, it is difficult to increase the density. Therefore, it has not yet reached the level of a material that is particularly required as a high-temperature structural member. In view of these points, the present inventors first developed MoSi ₂
Addition of SiC + B ₄ C without adding or SiC
We investigated the addition of +BN and succeeded in obtaining an improved ZrB ₂ sintered body. Although these have made it possible to put ZrB ₂ sintered bodies to practical use, it is also true that there is still room for improvement. For example, the addition system of SiC + 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 sintering It was difficult to obtain a solid body, and the strength and hardness were not necessarily sufficient, and therefore it could not be said to be suitable for applications such as high-temperature, high-strength members. In addition, although the SiC + B ₄ C additive system was satisfactory in terms of strength, hardness, and oxidation resistance,
It is not necessarily sufficient in terms of spall resistance and corrosion resistance, especially corrosion resistance against iron and slag, and therefore it is not necessarily suitable for uses such as spall resistance for steel and high temperature corrosion resistant parts. It was hot. 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 progressing in the development of this type of composite material, it has achieved various properties such as high density, high strength, oxidation resistance, corrosion resistance, and even spalling resistance. They succeeded in developing a sintered body with significantly improved performance. [Means for solving the problem] That is, the present invention contains ZrB ₂ as a main component, TiN, B ₄ C, and SiC as subcomponents at least 1% or more by weight, and each of these subcomponents contains The gist is a ZrB _dual- composite sintered body having high corrosion resistance with a total content of 10 to 50%. 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 temperature, and it is preferable to use ZrB 2 with as high purity as possible 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. In addition, regarding SiC, B ₄ C, and TiN, which are present as subcomponents, it is sufficient that they are present in a predetermined amount as such compounds in the sintered body, so it is important to note in what form they should be blended as starting materials. However, if raw materials other than SiC, B ₄ C, and TiN are used, special consideration is required in the sintering stage, so SiC, B ₄ C, and
It is better to adjust it as TiN. The raw materials for SiC, B ₄ C and TiN are also preferably as high in purity as possible, usually 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. In general, the particle size of the mixed raw material is preferably 10 μm or less, preferably the average 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 these mixtures into a graphite mold, for example, and hot pressing in a vacuum or in a neutral or reducing atmosphere such as argon, helium, carbon monoxide, etc., or by molding the above mixture with a rubber press. It is possible to sinter something by firing it under normal pressure. The firing temperature is 1700-2200℃, and the firing time is
Approximately 0.5 to 3 hours is appropriate. TiN, B ₄ C and SiC as subcomponents are each 1
% (wt%; the same applies hereafter), but this is because if TiN is less than 1%, the high corrosion resistance characteristics will not be fully exhibited, and if B ₄ C is less than 1%, it will be difficult to increase the density, and SiC will This is because, if it is less than 1%, oxidation resistance is insufficient. Furthermore, if the total amount of the subcomponents TiN, B ₄ C and SiC is too small, the corrosion resistance and oxidation resistance against iron and slag may be insufficient, or a high-density sintered body cannot be obtained. Not enough, at least 10% in total
is necessary. On the other hand, TiN, B ₄ C, and SiC can each be present in the sintered body up to about half the amount, but if TiN exceeds about 50%, the oxidation resistance decreases, and B ₄ C If it exceeds 50%, the heat resistance and corrosion resistance will be poor, and if the SiC content exceeds about 50%, the spalling resistance will not be effective, so it is not desirable.In any case, the characteristics of the ZrB ₂ quality will not be essentially impaired. To achieve this, it is necessary to limit the total amount of TiN, B ₄ C, and SiC to 50%. In addition, in these ranges, a more desirable range is that TiN, B ₄ C, and SiC are all 3
% or more, the total amount is 10% or more, preferably 20% or more40
%. In addition, the preferable range of each of the subcomponents is as follows:
TiN 3-15%, BiC 3-25%, SiC 3-30
%. In the sintered body of the present invention, the components other than these subcomponents, that is, the remainder of the main component, is substantially composed of ZrB ₂ , but other than ZrB ₂ may be used as long as the characteristics of the ZrB ₂ quality are not impaired. Of course, there is no problem even if a small amount of a component such as TiB ₂ is included as part of the main component, but it is desirable to keep the amount as small as possible. In addition, it is of course possible to include 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 sintered body of the present invention is structurally ZrB _{2
ZrB 2}
Crystals exist in the form of extremely fine crystals, and their properties have been fully demonstrated. 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] The sintered body of the present invention thus obtained has high density, high hardness, high strength, high oxidation resistance, and is particularly excellent in high temperature corrosion resistance.
It can be preferably applied to high-temperature structural members, high-temperature corrosion-resistant members, etc., and can also be used in a variety of other applications that exhibit the characteristics of the ZrB ₂ -substance sintered body, so its practical value is great. [Example] Example 1 ZrB ₂ powder (purity 99% or more) 75 parts by weight, TiN powder (purity 99%) 10 parts, B ₄ C powder (purity 99%) 10
and 5 parts of SiC powder (99% purity) were thoroughly mixed and ground in an ethanol solvent using a pot mill.
Grinding and mixing was carried out for 3 days using SiC balls. The obtained powder was thoroughly dried by removing alcohol with an evaporator to obtain a powder with an average particle size of 0.15 μm. This powder was packed into a graphite mold and heated to 350 kg/kg under an argon atmosphere.
A sintered body was obtained by heating at 1900° C. for 30 minutes under a pressure of cm ² . The properties of the obtained sintered body are: relative density 98%, bending strength 72Kg/mm ² , no change in oxidation resistance (Note 1), pure iron,
No erodibility (Note 2) against slag, hardness 2100
It was Kg/ ^mm2 . In addition, the size of most of the ZrB ₂ crystals in this sintered body was less than 5 μm, and it had a dense structure in which TiN, B ₄ C, and SiC were strongly bonded around the ZrB ₂ crystals. . Table 1 shows the properties of the sintered body thus obtained. Note 1: Oxidation resistance indicates the oxidation status under the conditions of 1000℃ x 12 hours in an oxidizing atmosphere. Note 2: Erosion properties were determined from the thickness of the altered layer formed by adjusting the sample to a 1 cm square, embedding it in pure iron or slag, and treating it at 1500°C for 2 hours. Note that the corrosion experiment was measured under an argon atmosphere. Examples 2 to 6 and Comparative Examples 1 to 4 Table 1 shows the results for each sample obtained by adjusting predetermined mixed raw materials according to Example 1 and processing them under predetermined firing conditions. 【table】

Claims (1)

[Claims] 1 ZrB ₂ as the main component, TiN, as subcomponents.
At least 1% each of B ₄ C and SiC by weight
Contains the above, and the total amount of these subcomponents is 10 to 50%
ZrB _dual -composite sintered body with high corrosion resistance. 2. The sintered body according to claim 1, wherein the subcomponents of TiN, B ₄ C, and SiC are all 3% or more by weight. 3 TiN is 3-15%, B ₄ C is 3-25%,
The sintered body according to claim 2, wherein the SiC content is 3 to 30%. 4 Total amount of TiN, _B4C and SiC is 20~20% by weight
40% of the sintered body according to any one of claims 1 to 3. 5. The sintered body according to any one of claims 1 to 4, wherein most of the ZrB ₂ crystals have a grain size of 10 μm or less.