Processing of WC with Fe-based alternative binders: Adjustment of C content and effect of Cr addition

Abstract

Alternative hard materials to traditional WC-Co are one of the main goals in the investigation efforts of both scientific and industrial communities. In this investigation, WC-based materials were designed and processed with different Fe alloys employing a powder metallurgy route. Two candidates were selected: FeCrAl and FeNiCr. The former showed the formation of aluminium oxides, which hindered a homogeneous metal-ceramic distribution. On the other hand, FeNiCr led to dense and optimised samples which were further characterised in terms of their mechanical properties and corrosion resistance. They revealed an excellent combination of hardness and toughness, comparable or even superior to industrial compositions containing Co. Selected Cr addition induced some segregation and formation of secondary carbides –in consonance with thermodynamic simulation results and as evidenced by optical microscopy, XRD and TEM analyses– with a decrease in the TRS value. However, massive nanoindentation tests revealed that it also led to improved intrinsic hardness of binder and composite (metal-ceramic) phases, as well as enhanced corrosion resistance in acidic media compared to Cr-free alternative and reference hardmetals.