Materials Transactions Online

Materials Transactions, Vol.50 No.05 (2009) pp.1096-1101
© 2009 The Japan Institute of Metals

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

Y. Yamanaka1, T. Taniuchi2, F. Shirase2, T. Tanase3, Y. Ikuhara4,5 and T. Yamamoto1,5

1Department of Advanced Materials Science, the University of Tokyo, Kashiwa 277-8561, Japan
2Tsukuba Plant, Mitsubishi Materials Corporation, Jyoso 300-2795, Japan
3Ryotec Corporation, Anpachi-gun, Gifu 503-2394, Japan
4Institute of Engineering Innovation, The University of Tokyo, Tokyo 113-8656, Japan
5Nanostructures Research Laboratory, Japan Fine Ceramic Center, Nagoya 456-8587, Japan

Microstructures in ZrC-doped WC-Co alloys, which were prepared by liquid-phase and solid-phase sintering, were investigated mainly by high-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectrometry (EDS). HRTEM study has revealed that multi facet structures, which are often observed in VC-doped alloys, were not formed in ZrC-doped alloys. In addition, the segregation of Zr at WC/Co interfaces could not be detected by EDS analysis even with nano size electron probe. Doped ZrC was found to exist as other carbide grains without dissolving into γ-phase, i.e., Co phase by EDS-mapping performed for liquid-phase sintered alloys. In the case of liquid-phase sintering, the inhibition effect for the grain growth caused by ZrC-doping was confirmed to be very small as previously reported. In contrast, it was found that ZrC-doping largely retards WC grain growth in the case of solid-phase sintering. The retardation of WC grain growth observed in solid-phase sintered alloys was considered to be closely related to a low sinterbility due to a low wettability between Co and ZrC.

(Received 2009/1/6; Accepted 2009/3/5; Published 2009/4/25)

Keywords: cemented carbides, grain growth, ZrC, high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectrometry (EDS)

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