Binder Phase Analysis for Property Improvement of WC-Co and WC-TiC-(Ta,Nb)C-Co Hardmetals

摘要

WC-Co and WC-TiC-(Ta,Nb)C-Co model alloys with high Co contents were prepared and analysed by wavelength-dispersive electron-probe microanalysis (WDS-EPMA). The maximum solubility of the various elements including Ti, Zr, V, Nb, Ta, Cr, Mo, W and C was measured in samples located within the two phase fields of fixed C activity neighbouring the phase fields of hardmetals, i.e. in samples with free eta phase as well as in samples with free carbon. These data specify the range of solubility of the various metals (also in combinations among each other) as a function of carbon content. They were used to prepare hardmetals at an industrial scale optimised in number and concentrations of carbides such as VC, Cr_3C_2 and TaC, which are commonly used as grain-growth inhibitors. Microstructural investigations of these hardmetals were performed by LOM, SEM and EBSD. In addition, hardness (HV30), Palmqvist fracture toughness (Klc) and TRS (four-point bending test, Weibull analysis) were measured.