Silicon Carbide Ceramics Sintering Technology

Silicon carbide ceramics have been widely used in petroleum, chemical, automotive, mechanical and aerospace industries due to their excellent thermal shock resistance, high temperature resistance, wear resistance, heat shock resistance, high thermal conductivity, high hardness, oxidation resistance, chemical corrosion resistance and thermal stability. For example, silicon carbide can be used as bearings, balls, nozzles, seals, turbocharger rotors, gas turbine blades, reflector screens and rocket combustion chamber linings.

SIC is a strong covalently bonded compound. Therefore, the diffusion rate during sintering is very low. The self-diffusion coefficients of C and SI are only so low even at 2100 C. SiC is difficult to sinter. Densification can only be achieved by means of additives or external pressure or siliconizing reaction. At present, the main methods of preparing high density SiC ceramics are pressureless sintering, hot pressing sintering, hot isostatic pressing sintering and reaction sintering.

Silicon carbide parts with complex shape and large size can be prepared by pressureless sintering process. Therefore, it is considered as the most promising sintering method for SIC ceramics.

SIC components with simple shape can only be prepared by hot pressing sintering process, and the number of products produced by one-time hot pressing sintering process is very small, so it is not conducive to commercial production.

SIC products with complex shapes can be obtained by hot isostatic pressing, but it is difficult to realize industrial production because of the need to encapsulate the deterioration.

Reactive sintering process can produce SIC components with complex shape, and the sintering temperature is low. However, the high temperature properties of reaction sintered SIC ceramics are poor.

Generally speaking, the comprehensive properties of pressureless sintered SIC ceramics are superior to those of reactive sintered SIC, but inferior to those of hot pressing sintered SIC and hot isostatic pressing sintered SIC.