JPH0431365A - High-temperature resistant member and production thereof - 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 [Object of the Invention] (Industrial Application Field) The present invention relates to a high temperature resistant member, and particularly to a high temperature resistant member suitable for a jig used for oxidation tests at high temperatures.

(Prior Art) Ceramics such as silicon carbide and silicon nitride have excellent heat resistance and high strength at high temperatures, and are expected to be applied to harsh applications at high temperatures such as gas turbines. Efforts are being made to find the most suitable materials and manufacturing methods for these ceramics by variously changing the composition of sintering aids, other components, sintering conditions, etc.

Various material evaluation tests are performed to evaluate the characteristics of the ceramic materials obtained in this way, and these evaluation tests require a jig to support the evaluation test piece. These jigs must not affect the evaluation test results.

In other words, if the evaluation test results are affected by the jig, the material will not be evaluated correctly. The results of material evaluation tests serve as powerful data when applying new materials to actual products, and these results must be accurate.

Therefore, there is a need for a test jig that provides stable and accurate evaluation results in various material evaluation tests.

Among the evaluation tests, oxidation resistance tests at high temperatures are particularly important for products used in the atmosphere at high temperatures, such as gas turbine components. Conventionally, jigs used for high-temperature oxidation resistance tests include oxide ceramics such as aluminum oxide and zirconium oxide, dense sintered bodies of silicon carbide ceramics and silicon nitride ceramics that can withstand high temperatures, or graphite. The surface is coated with silicon carbide or silicon nitride.

It is said that the aforementioned silicon carbide and silicon nitride need to be sintered as densely as possible when used in high temperature ranges, and sintering aids such as boron and carbon are added to silicon carbide, and itria and alumina are added to silicon nitride. The finely sintered material is used in jigs for high-temperature oxidation resistance tests. For example, Japanese Patent Publication No. 49-21091 discloses that silicon nitride containing yttria and alumina is suitable as a material for high temperatures, and Japanese Patent Publication No. 50-78609 discloses that silicon carbide containing boron and carbon is suitable for high-temperature materials. It has been shown to be suitable for high temperature materials.

(Problems to be Solved by the Invention) However, the conventional jigs for oxidation resistance tests still have points to be improved. Jigs made of aluminum oxide or zirconium oxide may soften at high temperatures, making it impossible to accurately support the evaluation specimen, or even evaporating, making it impossible to maintain the function of the jig. . Furthermore, in a jig made of silicon nitride or silicon carbide, in a high temperature range of 1600° C. or higher, the added sintering aid component may be oxidized and oxides may adhere to the evaluation test piece. It is thought that the adhesion of these sintering aid components to the evaluation test piece may affect the evaluation test results. Furthermore, all of the above ceramic sintered bodies are difficult to process and require many processing steps to obtain the desired shape of the test jig, and are difficult to process to accommodate evaluation test pieces of various shapes. It is difficult to obtain test jigs of arbitrary shapes.

Furthermore, graphite surfaces coated with silicon carbide or silicon nitride are not only expensive, but also have drawbacks such as long manufacturing time, and are not practical.

As described above, there are still points to be improved in the conventional evaluation test jigs. In particular, as the level of high temperature resistance and other properties required of new materials such as ceramics becomes higher and higher, the conditions for evaluation tests will also become more severe. There is a strong demand for superior high-temperature jigs.

The present invention has been made to address these problems, and an object of the present invention is to provide a high-temperature-resistant jig that has excellent heat resistance, particularly oxidation resistance at high temperatures, and good workability.

[Structure of the Invention] (Means and Effects for Solving the Problems) The high temperature resistant member of the present invention is characterized in that it is made of a high-purity silicon carbide sintered body containing no additive components. Moreover, the high temperature resistant member of the present invention can be obtained by comprising a step of molding silicon carbide powder having an average particle size of 3 μm or less into a predetermined shape and sintering it.

Silicon carbide has excellent high-temperature strength among ceramics. The inventor focused on this silicon carbide, analyzed the characteristics required for high temperature resistant members, and obtained the knowledge that led to the present invention.

In other words, in the past, it was necessary to add a sintering aid to obtain a sintered body of silicon carbide, but in the case of high-temperature resistant parts such as oxidation-resistant jigs, it is necessary to add a sintering aid to that degree. From the viewpoint that it was not necessary, we came up with the idea that silicon carbide without adding a sintering aid could be used.

This is a finding that would not arise from the conventional idea that silicon carbide without the addition of a sintering aid cannot be applied to structural members.

The silicon carbide sintered body constituting the high temperature resistant member of the present invention is of high purity and does not contain any additive components (except for unavoidable impurities), so even if exposed to high temperature conditions in an oxidizing atmosphere for a long time, no additives will be present. It does not cause softening due to ingredients or evaporation of added ingredients (and has excellent oxidation resistance. Also, since it does not contain added ingredients, it does not become more dense than necessary.
Even after sintering, it can be easily machined to obtain any desired shape. The silicon carbide sintered body constituting the high temperature resistant member of the present invention has a density of approximately 2 or less even after the sintering process, but has sufficient strength to support materials for evaluation tests as a jig, for example. .

In addition, the silicon carbide sintered body constituting the high temperature resistant member of the present invention hardly shrinks during the sintering process because there is no additive component, and therefore a product with high shape accuracy can be easily obtained. Therefore, it is also possible to process the material into a predetermined shape in advance before the sintering process.

Further, the high temperature resistant member of the present invention can obtain the strength necessary as a jig by molding silicon carbide powder with an average particle size of 3 μm or less into a predetermined shape and sintering it. If the particle size of the raw material powder is too large, sufficient strength after sintering cannot be obtained. The high temperature resistant member of the present invention can be obtained by adding a binder to high purity silicon carbide powder, molding it into a predetermined shape, and sintering it in an inert atmosphere. In the sintering process,
Since there are no additive components, it is necessary to carefully examine the conditions, especially regarding the sintering temperature and atmosphere. In particular, the atmosphere requires a non-oxidizing atmosphere, preferably Ar, and the temperature range is preferably 1900°C to 2200°C. Processing into the required jig shape is possible either after molding or after sintering.

(Example) Next, examples of the present invention will be described.

A mixture of α-8iC powder with an average particle size of 0.5μ■ as a raw material, paraffin added as a binder, and well mixed was molded in a molding press at a pressure of 1 ton/cj to form a 5 x 2
A molded body of 0×20+m was obtained. After degreasing this compact, it was sintered by raising the temperature to 2100° C. at normal pressure in an argon gas atmosphere. A hole 4 with a diameter of 5.5 mm is formed in the obtained sintered body.
A jig for oxidation test as shown in FIG. 1 was obtained by processing the piece. The processing was carried out using a cemented carbide drill. The density of the sintered body was about 1.9, and by using a cemented carbide drill, holes with high precision could be obtained.

A test piece of silicon nitride sintered body was inserted into the hole of the oxidation test jig obtained in this way, and the test piece was heated at 1700°C x 1 in an air atmosphere.
A 00 hour oxidation test was conducted. As a result, there was almost no change in the oxidation test jig, and the weight change was less than 0.5%. In addition, it was possible to obtain suitable evaluation test results without causing phenomena such as foreign matter adhering to the test piece.

For comparison, an oxidation test jig with the same shape as in the above example was prepared using a silicon nitride sintered body containing ittriya and alumina as sintering aids, and the test was conducted.
An oxide layer formed on the surface of the jig at around 00°C, making it unusable. In addition, the silicon nitride sintered body is dense, and it takes a long time to process the hole into which the evaluation test piece is inserted.

In addition, when an oxidation test jig was prepared and tested using a silicon carbide sintered body containing a sintering aid, the same phenomenon as that using a silicon nitride sintered body occurred, and the An oxidized layer formed on the surface of the ingredients, making them unusable.

In addition, an oxidation test jig was prepared using a sintered body obtained by molding and sintering α-8iC powder with an average particle size of 3.5 μm under the same conditions as above. Because the body did not have sufficient strength, the hole into which the test piece was inserted could not be properly machined, making it difficult to support the test piece accurately.

[Effects of the Invention] As explained above, according to the present invention, it is possible to provide a high temperature resistant member that has excellent heat resistance, particularly oxidation resistance at high temperatures, and has good workability. The high-temperature member of the present invention is particularly suitable as a jig for oxidation tests at high temperatures, and can also be applied to furnace members that do not require much strength.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention. Agent: Patent Attorney Noriyuki Chika Same Yukio Yama

Claims (2)

[Claims] (1) A high-temperature-resistant member characterized by being constructed of a high-purity silicon carbide sintered body containing no additive components. (2) A method for producing a high temperature resistant member, comprising a step of molding silicon carbide powder with an average particle size of 3 μm or less into a predetermined shape and sintering it.