JPH0735305B2 - Method for manufacturing ceramics sintered body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a high temperature gas turbine, a diesel engine, an MHD.
High-temperature and high-strength materials used in power generation, high-reliability and high-strength ceramics used in automobile parts and bearing balls, etc. Si that does not sinter by the usual sintering method Si additive-free Si
_{The present} invention relates to an advantageous method for obtaining a ceramic component made of ₃ N ₄ and Si ₃ N ₄ —SiC composite material.

<Prior Art> Conventionally, as a method for producing such a ceramics sintered body, a silicate glass container is used, or a silicate glass material that forms a gas impermeable layer at a sintering temperature is used to perform hot static treatment. There is a method of performing hydraulic press treatment. (For example, JP-B-58-1074, JP-B-58-11319, JP-B-59-10946, JP-B-59-7323, and JP-B-59-35.
870, Japanese Patent Publication No. 62-32241).

Further, in this method, there is a hot isostatic pressing method in which a barrier material such as BN is further applied to the surface of the molded body (for example, Japanese Patent Publication No. 61-46432, Japanese Patent Publication No. 63-395, and Japanese Patent Publication No. 62-347).
(See Publication No. 11).

Such a method is an effective means for producing high-reliability, high-temperature, high-strength ceramic materials, and in particular, a non-sinterable barrier material (such as BN) is used between the glass and the molded body such as Si ₃ N _4. The method used is important for increasing the difficulty with glass and maintaining the shape of the sintered body.

<Problems to be Solved by the Invention> However, when performing hot isostatic pressing by protecting the ceramics with a glass capsule or the like as described above,
It was found that black speckled defects composed of carbon and iron elements contained as impurities in the sample were formed, which became the origin of fracture of the sintered body material, causing strength deterioration and reliability deterioration. . (Katsuhiko Homma et al .; Journal of Kiln Association 95 [2] 229
-341987) <Means for Solving the Problems> The present invention has been made to solve the above problems.
Paying attention to the fact that the cause of the black spots is largely influenced by the amount of carbon in the barrier material, and as a result of various studies, it was found that this defect does not occur by controlling the carbon in the barrier material.

As a means for controlling the amount of carbon, a high-purity powder having a small amount of carbon is used for the barrier material, or carbon containing carbon obtained by removing carbon by a method of pre-oxidizing the barrier material at a temperature at which the barrier material does not have an adverse effect. This is achieved by using a low amount of powder as a barrier material.

That is, the outline of the present invention is to coat a surface of a ceramic powder compact with a barrier material that is difficult to sinter and has low reactivity with the ceramic powder compact, and to form a gas impermeable container or a gas impermeable layer. After encapsulation, in carrying out hot isostatic pressing treatment, a method for producing a ceramic powder compact characterized by using a barrier material having a carbon content of 0.10 wt% or less, more preferably 0.05 wt% or less. .

<Operation> According to the present invention, since the surface of the ceramic powder compact is covered with a barrier material having a carbon content of 0.10 wt% or less, the occurrence of black spots is extremely small even by hot isostatic pressing, In particular, when using a barrier material having a carbon content of 0.05% by weight or less, the occurrence of black spots is eliminated, which eliminates the fracture origin of black spots and, as a result, reduces the variation in the strength of the sintered body. It improves the level of average strength.

<Examples> Examples will be described below.

Examples 1 to 4 Si ₃ N ₄ powder 94% by weight, Al ₂ O ₃ powder 3% by weight, Y ₂ O ₃ powder 3
% By weight was mixed and pressed.

This Si ₃ N ₄ powder compact is preliminarily coated in the range of 500 ℃ ~ 800 ℃ 100
Oxidation calcination is performed every 2 ° C for 2 hours, BN powder with varying carbon content is applied, vacuum sealed in Vycor glass, and hot isostatic pressing is performed at 1600 ° C-1000kg / cm ² -2h. Was done.

Three-point bending strength of the obtained sintered body was measured, and the origin of fracture was also observed.

Comparative Examples 1 to 2 Comparative Example 1 was treated under the same conditions as Example 1 except that BN oxidation calcination was not performed, and Comparative Example 2 was treated under the same conditions as Example 1 except calcination at 400 ° C. Then, the same test as in the example was performed.

The results of these experimental examples and comparative examples are shown in the following table.

That is, in each of the examples, the amount of carbon in BN is small, the average strength is strong, the maximum strength (σmax),
There is little variation in the minimum strength (σmin), and the black spots are very small in Examples 1 and 2, but the degree thereof is extremely small, and there are no black spots in Examples 4 and 5, and the entire Examples are destroyed. It can be seen that the probability of the origin is small and that it is extremely superior to the comparative example.

Although the case where BN is used as the barrier material has been described above, it is clear that similar results can be obtained with other barrier materials such as AIN and Si ₃ N ₄ if the carbon content is 0.10 wt% or less.

<Effects of the Invention> According to the present invention, the amount of carbon in the barrier material is controlled to 0.
When the content is 10% by weight or less, the black spots on the ceramic sintered body can be reduced or eliminated, the variation in the strength of the sintered body can be reduced, the average strength level can be improved, and high reliability and high strength can be obtained. A sintered body can be obtained.

Claims (1)

[Claims] 1. A ceramic powder compact is coated on its surface with a barrier material which is difficult to sinter and has low reactivity with the ceramic powder compact, and is covered with a gas impermeable container or a gas impermeable layer. A method for producing a ceramics sintered body, comprising using a barrier material having a carbon content of 0.10% by weight or less in performing hot isostatic pressing.