US Patent 7132153 Coated cutting tool insert for machining of cast irons

The present invention concerns a coated cemented carbide cutting tool insert particularly useful for turning of cast irons. The cutting tool insert is characterized by a cemented carbide body comprising WC, cubic carbonitrides, a W-alloyed Co binder phase, a surface zone of the cemented carbide body that is binder phase enriched and nearly free of cubic carbonitride phase, and a coating including an innermost layer of TiCxNyOz with equiaxed grains, a layer of TiCxNyOz with columnar grains and at least one layer of Al2O3.