A support structure for the sintering process of large-scale reaction-sintered silicon carbide

Abstract

The invention relates to a support structure for a large-scale reaction sintering silicon carbide sintering process, belonging to the technical field of reaction sintering silicon carbide preparation. The supporting structure of the present invention is composed of an upper graphite plate, a lower graphite plate, and ceramic balls located between the two graphite plates, and the rolling support is mainly realized by the ceramic balls placed in the sinking platform of the graphite plate; the rolling of the ceramic balls can realize the supporting area The position changes, and when the position of the support area changes, it is only affected by the rolling friction of the ceramic ball. Since the rolling friction of the ceramic ball is very small, the process of thermal expansion and contraction of the green body is almost not restricted by the support area, and the green body can be realized. The free expansion and contraction greatly reduces the stress of the green body during the sintering process and improves the yield in the preparation process.

Description

technical field [0001] The invention relates to a structure for supporting a green body in a sintering process, in particular to a support structure for large-size reaction sintered silicon carbide that is horizontally unconstrained during the sintering process, and belongs to the technical field of reaction sintered silicon carbide preparation. Background technique [0002] Reaction sintered silicon carbide is one of the most commonly used engineering ceramics. Its preparation method is to put SiC / C porous preform (hereinafter referred to as preform) and Si together in a vacuum sintering furnace for heating, so that the molten Si can completely penetrate into the preform. In the pores of the body, the carbon in the green body reacts with the infiltrated silicon to form new silicon carbide, and the remaining liquid free silicon fills the pores, thereby obtaining a dense silicon carbide ceramic and completing its reaction sintering process. [0003] When preparing small-sized...

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Problems solved by technology

[0004] However, when large-sized reaction sintered silicon carbide is prepared, the weight of the green body is very large; if the traditional method of directly placing the green body on the crucible, or using a high-temperature-resistant solid support on the graphite crucible, during the heating and cooling process , due to the difference in linear expansion coefficient between the green body and the crucible, the expansion and contraction process of the green body will be constrained by the large friction force at the support point, which will generate a large stress on the green body

Since the strength of the SiC / C preform is low during the heating and sintering process, the strength of the green body after reaction sintering is also relatively low at high temperature. When the stress at any point in the green body is greater than the strength of the green body, it will cause the green body to crack. , make reaction sintered silicon carbide products useless

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