Analyze the relationship between the operating temperature of silicon carbide products and working conditions

The theoretical service temperature of reaction-bonded silicon carbide (RBSiC) products is generally ≤1380°C . In a non-oxidizing atmosphere, it can reach higher temperatures, close to 1350-1400°C. In an oxidizing atmosphere, it can be used less than 1300°C. If the service temperature is over 1400°C, the free silicon in the material may soften, leading to a loss of strength of the material. The maximum service temperature of RBSiC is determined by and related to the following factors:

Chemical composition and purity

• Purity of raw materials: High-purity silicon and carbon raw materials can reduce the content of impurities, thereby improving the high-temperature performance of RBSiC. Impurities may form low-melting-point phases at high temperatures, which will reduce the maximum service temperature.

• Additives: Some additives are often added during the preparation process of RBSiC to improve its performance. For example, small amounts of boron and carbon can improve the sinterability and mechanical properties of silicon carbide, thus affecting the maximum service temperature.

Microstructure

• Grain size and distribution: Fine and uniform grain size is beneficial to improving the high-temperature strength and stability of RBSiC. If the grain size is too large or uneven, it may lead to stress concentration at high temperatures and reduce the maximum service temperature.

• Porosity: The porosity of RBSiC has a great influence on its high-temperature performance. The lower the porosity, the better the density and the higher the maximum service temperature that the material can withstand.

Service environment

• Oxidation resistance: In an oxidizing atmosphere, RBSiC will react with oxygen at high temperatures to form a silicon dioxide protective film. However, when the temperature is too high or the oxidation time is too long, the protective film may be destroyed, affecting the service life of the material.

• Mechanical load: If the RBSiC product is subjected to a large mechanical load at high temperatures, it may cause plastic deformation or even cracking of the material, thus limiting the maximum service temperature.

• Corrosive medium: In the presence of corrosive media, the material may be corroded at high temperatures, which will also reduce its maximum service temperature.

Manufacturing process

• Sintering temperature and time: Appropriate sintering temperature and time can make the material denser and the crystal structure more stable, thus improving the maximum service temperature.

• Cooling rate: The cooling rate after sintering also affects the internal stress and microstructure of the material. A too fast or too slow cooling rate may lead to the formation of internal defects and affect the high-temperature performance of the material.