Pressureless sintering of SiC ceramic materials

Vacuum sintering furnace is suitable for vacuum sintering of powder metallurgy products, metal forming products, graphite composite felt hardening, stainless steel matrix, ceramic materials, etc.

Although the reaction sintering of SiC ceramic materials in high temperature vacuum sintering furnace is simple and easy, it can not eliminate the residual Si in the products, so the service temperature is low, and it also brings many limitations to the application environment and working conditions. As far as the mechanical properties of ceramic materials are concerned, the high-temperature vacuum sintering furnace hot pressing sintering process is undoubtedly easier to obtain higher mechanical properties and more uniform microstructure, but the shape of hot pressing sintered products in high-temperature vacuum sintering furnace is single and the cost is high.

Therefore, people’s interest gradually shifted from hot pressing and Reactive Sintering SiC to pressureless sintering in high temperature vacuum sintering furnace. SiC [13j4] O pressureless sintering can prepare complex shaped parts and large-size SiC ceramic parts, and it is relatively easy to realize industrialization. Therefore, it is considered to be the most promising sintering method for SiC ceramic composites. Compared with the reaction sintering method in high temperature sintering furnace, the purity of Pressureless Sintering SiC is higher, the mass fraction of SiC is more than 97%, the corrosion resistance is much better than that of Reaction Sintering SiC, and the product has more market competitiveness.

Pure SiC ceramic is a kind of stable compound with strong covalent bond. It is difficult to sinter by Pressureless Sintering in high temperature vacuum sintering furnace. Therefore, additive g must be used. According to different additives, pressureless sintering in high temperature vacuum sintering furnace can be divided into solid phase sintering and liquid phase sintering. B-C and T1b are effective additives for SiC solid phase sintering, and al2o3-y2o3 and a14cj-b4c are effective additives for SiC liquid phase sintering. Both solid phase sintering and liquid phase sintering are carried out under the protection of inert gas (oxygen).

Vacuum sintering furnace is generally composed of furnace, electric heating device, sealed furnace shell, vacuum system, power supply system and temperature control system. The sealed furnace shell is welded with carbon steel or stainless steel, and the joint surface of detachable parts is sealed with vacuum sealing material. In order to prevent the deformation of the furnace shell and the deterioration of the sealing material after heating, the furnace shell is generally cooled by water cooling or air cooling. The furnace is located in a sealed furnace shell. According to the purpose of the furnace, different types of heating elements are installed in the furnace, such as resistance, induction coil, electrode and electron gun. Crucible is installed in the furnace of vacuum furnace for melting metal, and some are also equipped with automatic pouring device and manipulator for loading and unloading. The vacuum system is mainly composed of vacuum pump, vacuum valve and vacuum gauge.