Alumina Coated Grade

A cutting tool insert comprising a cemented carbide body and a coating;

• wherein the cemented carbide body comprises:
• WC;
• about 5-9 wt-% Co;
• and
• about 5-11 wt-% cubic carbides of at least one metal selected from the group consisting of groups IVb, Vb and VIb of the periodic table;
• wherein the cemented carbide body has an S-value of about 0.79-0.9 and a coercivity of about 9-16 kA/m;
• wherein at least one surface of the cemented carbide body comprises a binder phase enriched surface zone with a thickness of about 5-40 μm being essentially free from cubic carbides adjacent the coating;
• wherein the coating comprises at least one α-Al2O3 layer, wherein the α-Al2O3 layer is about 2-9 μm thick and wherein the α-Al2O3 layer comprises columnar grains with a length/width ratio from about 2-12 whereby the α-Al2O3 layer has a texture coefficient TC(104)≧2.0:
• the texture coefficient TC(hkil) being defined as:
• TC
• 
• (
• hkil
• )
• =
• I
• 
• (
• hkil
• )
• I
• 0
• 
• (
• hkil
• )
• [
• 1
• n
• 
• ∑
• n
• =
• 1
• n
• 
• I
• 
• (
• hkil
• )
• I
• 0
• 
• (
• hkil
• )
• ]
• -
• 1
• where:
• I(hkl) intensity of the (hkl) reflection;
• Io(hkl) standard intensity according to JCPDS card no. 46-1212;
• n number of reflections used in the calculation;
• where the (hkil) reflections used are:
• (012), (104), (110), (113) and (116).