US Patent RE39893 Cemented carbide insert

The present invention relates to a cutting tool insert and its methods of manufacture for machining of steel comprising a cemented carbide body and a coatings. The cemented carbide body includes WC, 5-12 wt-% Co and 3-11 wt-% of cubic carbides of metals Ta and Ti. The amount of Nb is below 0.1 wt-% and the ratio Ta/Ti is 1.0-4.0. The Co-binder phase is highly alloyed with W with a CW-ratio of 0.75-0.95 and, finally, the cemented carbide body has a binder phase enriched and essentially gamma phase free surface zone of a thickness of 5-50 μm.