Abstract
1. WC-0.40 mass%VN-0.44 mass%Cr3C2-8.0 mass%Co alloys using 0.4 micron WC powders were prepared by sintering and HIPing. In these alloys trace amount of V-rich phase were observed.
Quantification of V-rich phases was performed as follows. (1) The location of V-rich phase was determined by EPMA and FE-SEM. (2) Cutting off and making thin film was done by FIB and determination of the size of V-rich phase was carried out by FE-TEM observation. (3) The threshold value was set by coincidation of the size by FE-TEM with peak width of EPMA line analysis. (4) EPMA V mapping image was binarized by the threshold value and area % was obtained by image analysis. The amount of V-rich phase in middle carbon alloy was 0.008area% and the amount of V-rich phase increased with increasing carbon content from 0.001 to 0.051area%.
2. The start of melting as well as melting range in WC-31 mass%Co alloys were analysed by DTA measurement. They were significantly influenced by carbon content, start of melting for low carbon alloy and high carbon alloy were 1641 K and 1571 K respectively. Addition of Cr or V significantly lower the start of melting, especially for Cr added high carbon alloy. In case of Cr and V combined addition in solidification, there were two peaks suggesting two step solidification.
