Sintering, properties and microstructure of low friction SiC ceramic seals containing graphite fluoride

Low friction silicon carbide (SiC) ceramic seals were prepared by liquid phase sintering in the presence of graphite fluoride. The addition of graphite fluoride as a lubricating additive restricted the sintering of SiC ceramics and worsened the mechanical properties to some extent, but obviously reduced the friction coefficient of SiC ceramic seals. With the graphite fluoride content increasing from 0 to 7 wt-%, the bending strength of SiC ceramic decreased from 507 to 357 MPa, while the dry friction coefficient dropped from 0·4 to 0·2. The graphite fluoride particles with lamellar structure did not vary the main crystalline phase compositions and distributed in the boundary of SiC grains. When the self-mated friction happened, graphite fluoride would fall off and stick to the friction surface, which improved the friction performance of SiC ceramic seals.