High Resolution Electron Microscopy Study in ZrC-Doped WC-12 mass%Co Alloys

Microstructures inZrC-dopedWC-Coalloys,whichwerepreparedbyliquid-phase andsolid-phasesintering,wereinvestigated mainlybyhigh-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectrometry (EDS). HRTEM study has revealed thatmulti facet structures, which are often observed in VC-doped alloys, were not formed in ZrC-doped alloys. In addition, the segregation of Zr atWC/Co interfaces could not be detected by EDS analysis even with nano size electron probe. Doped ZrC was found to exist as other carbidegrains without dissolving into -phase, i.e., Co phase by EDS-mapping performed for liquid-phase sintered alloys. In the case of liquid-phasesintering, the inhibition effect for the grain growth caused by ZrC-doping was confirmed to be very small as previously reported. In contrast, itwasfoundthatZrC-dopinglargelyretardsWCgraingrowthinthecaseofsolid-phasesintering.TheretardationofWCgraingrowthobservedinsolid-phase sintered alloys was considered to be closely related to a low sinterbility due to a low wettability between Co and ZrC.[doi:10.2320/matertrans.MC200826](Received January 6, 2009; Accepted March 5, 2009; Published April 25, 2009)Keywords: cemented carbides, grain growth, ZrC, high-resolution transmission electron microscopy (HRTEM), energy dispersive X-rayspectrometry (EDS)