Contact angles of WC/WC grain boundaries (GBs) with the Co-based binder were measured by use of special model alloys with 10 wt% Co, ultra-coarse grained microstructure and either a low or a high carbon content. The low-carbon sample contained significantly more low-angle WC/WC contacts with binder than the high-carbon sample. Therefore, the wettability of WC/WC GBs by the liquid Co-based binder is noticeably worse in the high-carbon sample than that in the low-carbon sample. The established worse wettability of WC/WC GBs by binders at high carbon content sheds light on the mechanism of the binder drift during sintering of functionally graded cemented carbides containing high-carbon surface layers. (C) 2017 Elsevier B. V. All rights reserved.