COATED CEMENTED CARBIDE INSERTS FOR MILLING OF ESPECIALLY HARD CAST STEEL

摘要

The present invention relates to cutting insert for especially dry milling of hard cast steel with a hardness of 50-65 HRC comprising a substrate and a coating. Inserts according to the invention has improved edge line security and wear resistance in combination with good plastic deformation resistance. The substrate has a hardness of 1900-2100 HV3, with a negative chamfer and an edge rounding of 0 (sharp) -40 µm. The substrate comprises a cemented carbide with the composition 5.4 - 6.3 wt-%Co, 0.4-0.8 wt-% Cr, 0.01 - 0.05 wt-% Ti + Ta added as TaC and TiC or mixtures of these and balance WC. The cemented carbide susbstrate is sintered to obtain an Hc -value of 29-35 kA/m and a CW-Cr of 0.75-0.95. The coating comprises a homogeneous AlxTi1-xN- layer with x=0.6-0.67 and a thickness of 1-3.8 µm. The coating is deposited by cathodic arc evaporation using a target material consisting of TiAl-alloy of suitable composition, in an N2-gas atmosphere.