Cerium enrichment on sinter skin of mischmetal doped WC-Co cemented carbide

Rare earth-doped WC-Co cemented carbides with low carbon-containing level were prepared by adding mischmetal (mainly containing lanthanum and cerium) in the form of cobalt pre-alloyed powder during ball-milling.After sintering, the sinter skin (exterior) was observed and analyzed by scanning electron microscopy(SEM)and energy disperse X-ray spectroscopy(EDXS). The results show that during the sintering process lanthanum and cerium are separated and cerium predominantly migrates towards the surface forming precipitates containing oxygen.Thermodynamic analysis and polarization of cerium atom caused by the strong interaction between cerium atoms and high energy carbon atoms were used in explaining the observed phenomenon.