Silicon carbide ceramic molding process comparison: sintering process and its advantages and disadvantages

Silicon carbide ceramic molding process comparison: sintering process and its advantages and disadvantages

In the production of silicon carbide ceramics, forming is only one link in the whole process. Sintering is the core process that directly affects the final performance and performance of ceramics. There are many different methods of sintering silicon carbide ceramics, each with its own advantages and disadvantages. In this blog post, we will explore the sintering process of silicon carbide ceramics and compare various methods.

1. Reaction sintering:
Reaction sintering is a popular fabrication technique for silicon carbide ceramics. This is a relatively simple and cost-effective near net-to-size process. Sintering is achieved by silicidation reaction at a lower temperature of 1450~1600°C and a shorter time. This method can produce parts of large size and complex shape. However, it also has its disadvantages. The siliconizing reaction inevitably leads to 8%~12% free silicon in silicon carbide, which reduces its high-temperature mechanical properties, corrosion resistance, and oxidation resistance. And the use temperature is limited below 1350°C.

2. Hot pressing sintering:
Hot pressing sintering is another common method for sintering silicon carbide ceramics. In this method, dry silicon carbide powder is filled into a mold and heated while applying pressure from a uniaxial direction. This simultaneous heating and pressure promotes particle diffusion, flow, and mass transfer, resulting in silicon carbide ceramics with fine grains, high relative density, and excellent mechanical properties. However, hot pressing sintering also has its disadvantages. The process is more complicated and requires high-quality mold materials and equipment. The production efficiency is low and the cost is high. In addition, this method is only suitable for products with relatively simple shapes.

3. Hot isostatic pressing sintering:
Hot isostatic pressing (HIP) sintering is a technique involving the combined action of high temperature and isotropically balanced high-pressure gas. It is used for sintering and densification of silicon carbide ceramic powder, green body or pre-sintered body. Although HIP sintering can improve the performance of silicon carbide ceramics, it is not widely used in mass production due to the complicated process and high cost.

4. Pressureless sintering:
Pressureless sintering is a method with excellent high temperature performance, simple sintering process and low cost of silicon carbide ceramics. It also allows multiple forming methods, making it suitable for complex shapes and thick parts. This method is very suitable for large-scale industrial production of silicon ceramics.

In summary, the sintering process is a crucial step in the production of SiC ceramics. The choice of sintering method depends on factors such as the desired properties of the ceramic, the complexity of the shape, production cost and efficiency. Each method has its own advantages and disadvantages, and it is important to carefully consider these factors to determine the most suitable sintering process for a particular application.