TourTourThermal fracture

The sealing function in Mechanical face seals, M-seals or face seals in short is created between two axial ring faces. Mechanical seals materials are commonly hard-to-soft combinations where the soft face is carbon-graphite, usually impregnated with resin, and the hard face sintered or reaction bonded silicon carbide. Other hard face materials include tungsten carbide and aluminum oxide. For abrasive media hard-to-hard faces are used, generally SiC to SiC (Figure above).

High contact temperatures and large temperature gradients can be responsible for large thermo-mechanical stresses which in turn cause thermo-cracking and wear.
This is especially the case in brittle materials like ceramics.