Wear phenomena on WC-based face seal rings

In order to study wear mechanisms on WC-based face seals, lubricated seal tests have been performed. The tested materials were WC–Co, WC–Ni and a WC–TiC binderless carbide. The tests lasted for 700 h and all seals were still fully functional at the end of the tests. The worn surfaces have been studied with a range of different techniques including focused ion beam and transmission electron microscopy (TEM). All tested seals showed a periodic wear pattern extending perpendicular to the sliding direction. On the metal bonded cemented carbides the pattern included cracks penetrating about 40 μm into the material. In connection to each crack on the WC–Co seals, a damaged subsurface zone with altered structure was found. X-ray analysis of the altered zone revealed the presence of oxides in the vicinity of the cracks as well as an enrichment of Cl in the crack tips. The mechanisms that may have caused the surface damages are discussed.