An observation of the binder microstructure in WC-(Co plus Ru) cemented carbides using transmission Kikuchi diffraction

The microstructure of WC-(Co+Ru) cemented carbides was studied using transmission Kikuchi diffraction (TKD). We report that the Co-FCC grains contain Sigma 3-annealing twins which undergo an incomplete martensitic transformation to form Co-HCP laths on cooling below T-MS. The parent Co-FCC and product Co-HCP, phases are related via the Shoji-Nishiyama orientation relationship. Four variants of the Co-HCP, plates exhibit a special misorientation of 70.5 +/- 0.2 degrees < 11 (2) over bar0 >. A higher transformed fraction was observed in the sample possessing the lower binder content and finer WC grains. We suggest that this is due to the availability of more WC-binder interfaces, which facilitate Co-HCP plate nucleation. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.