Silicon carbide (SiC) is a popular seal face material due to its high hardness, wear resistance, good thermal conductivity, and chemical stability. The fourth edition of API 682 standard accepts both types of SiC as default seal face materials, but they differ in manufacturing process, structure, and chemical resistance.
SiC particles mixed with carbon are formed, then molten silicon infiltrates the pores and reacts with carbon to form additional SiC. The result is a dense material with almost no porosity, but still contains a amount of free silicon bonding between particles.
Fine SiC powder mixed with sintering aids is formed and then fired at a very high temperature, the particles bond directly to each other. The resulting material is almost entirely composed of SiC, with no free silicon.
There is a type of SSiC that contains graphite particles to improve its ability to withstand dry running, and a type of SiC with controlled porosity to retain liquid at the seal face, reducing friction. Each type has its own advantages and disadvantages, so it is necessary to choose according to the service.
SiC is a brittle material, so it is prone to cracking when impacted or unevenly clamped. When two SiC faces are mated together, the seal is less resistant to dry running compared to mating SiC with carbon.
Always check the chemical compatibility chart of the manufacturer for each medium and concentration. Contact SNS-VN for advice on material selection.
Pumps and Systems, a compilation of common technical knowledge of materials.