Fabrication of Functionally Graded WC-Co Cemented Carbides with Plate-Like WC Grains

Functionally graded WC-Co cemented carbides (FG WC-Co) with plate-like WC grains were fabricated by carburizing of cemented carbides with no eta phase. The phase composition and microstructure of FG WC-Co were investigated by XRD, SEM and EDX. The results showed that a cobalt-deficient layer was formed due to difference in affinity among carbon and other alloying elements. WC grain size increased while the ratio of side length to thickness decreased slightly in the surface zone due to difference of growth rate between different planes of WC grains. Moreover, FG WC-Co possessed an 80 mu m deep cobalt-deficient layer, and showed excellent mechanical properties with a surface hardness of 1748 HV and fracture toughness of 9.6 MPa center dot m(1/2) in the surface zone.