Abstract WC–5TiC–10Co ultrafine and conventional cemented carbides were prepared and used for AISI 1045 carbon steel cutting tool inserts. The microstructure and mechanical properties were characterized, and cutting tests were conducted with different cutting parameters. Tool wear mechanism was analyzed by SEM and EDS. Ultrafine inserts possess higher hardness and transverse rupture strength. There were adhesive wear on the rake and slight abrasive wear on the flank of ultrafine inserts. As for conventional inserts with the same composition but with medium grain size, there were combinations of more serious abrasive and adhesive wear on the rake and flank.