Korean Journal of Materials Research, Vol.10, No.9, 612-618, September, 2000
WC기 초경합금중 WC/WC界面의 구조와 입계편석
Stucture and Intergranular Segregation of WC/WC Grain Boundaries in WC-Based Cemented Carbides
초록
WC-Co와 WC-Co 초경합금중 WC/WC 입계의 구조와 입계 편석상태를 알아볼 목적으로 HRTEM과 EDS를 이용하여 연구하였다. 일부의 입계들은 액상에 의하여 분리된 상태로 관찰되었으나, 상당수는 원자적 상태의 연소계면이었다. 또 연속계면 중 WC-Co 합금에서는 Co 상이 편석되어 있었으며, WC-VC-Co 합금에서는 Co와 V이 동시에 편석되어 있음을 알 수 있었다. 그 편석의 폭은 약6nm이었다. 연속 계면 중 V의 편석은 소결 또는 열처리 시에 일어나는 입계 이동을 억제하는 데 효과적인 역할을 할 것으로 여겨졌다. 동시에 이것은 WC-Co 초경합금에서 VC 첨가에 의한 입성상 억제기구를 설명할 수 있는 것으로 사료되었다.
The WC/WC grain boundary structure and intergranular segregation in WC-Co and WC-VC-Co cemented carbides were investigated by high-resolution transmission electron microscopy and energy dispersive X-ray spectroscopy in order to elucidate whether contiguous boundaries were present or not at the atomic level. Some grain boundaries were separated by liquid phase, while others were contiguous at the atomic level. Cobalt was found to be segregated to WC/WC grain boundaries in WC-Co. Cobalt and vanadium were co-segregated to grain boundaries in WC-VC-Co. The segregation width in both materials was about 6 nm. These results suggest that the vanadium present in contiguous boundaries acts as an effective barrier to the migration of boundaries during sintering and annealing. This could explain the grain growth inhibiting mechanism of VC added to WC-Co.
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