IMPROVED COATED CUTTING INSERT FOR ROUGH TURNING

The present invention relates to a cutting tool insert of a cemented carbide substrate (D) and a coating. The insert is used for medium and rough machining of steels. The object of the invention is to provide a coated tool insert with good deformation resistance, good wear resistance and high toughness. The cemented carbide substrate comprises WC, 8-11 wt-% Co, 6.5-11 wt-% cubic carbides of metals from the groups IVb, Vb and VIb with a binder phase that is highly alloyed with tungsten. The substrate has a binder phase enriched surface zone (C). The cemented carbide has a coercivity of 8- 14 kA/m. The coating comprises at least one 2-9 µm thick a- aluminium oxide layer (A) composed of columnar grains with texture coefficients, TC(006)>2 and