The ultrafine WC-Co composite. powder was synthesized by in situ reactions of metal oxides and carbon. The thermal spraying feedstock was prepared by granulation using the as-synthesized composite powder. The influence of carbon addition in the starting powders on the phase constitution and chemical composition of the prepared composite powder and spraying feedstock as well as on the microstructure and mechanical properties of the sprayed cermet coating was investigated. By adjusting the carbon addition in the initial stage, the pure phase constitution can be obtained in the prepared spraying feedstock. In the subsequent thermal spraying, the decarburization can be inhibited by the free carbon existing in the feedstock powder. With an appropriate carbon addition, the prepared ultrafine-structured coating has the best combination of hardness and toughness and thus the coating exhibits the highest wear resistance. The present work indicates the significant role of carbon control during the preparation processes of WC-Co coatings. (c) 2013 Elsevier B.V. All rights reserved.