COATED CUTTING TOOL INSERT

摘要

The present invention relates to a CVD-coated cutting tool insert with improved toughness properties having the ability to withstand high temperatures resulting from, e.g., extended times in cut or high metal removal. The insert has a cemented carbide body with composition of 4.0-5.3 wt-% Co, 6.4-8.1 wt-% cubic carbides, balance WC, a hardness HV3 of 1590-1650, a CW-ratio in the range 0.78-0.92 and having a surface zone of a thickness of 10 to 16 mm depleted from the cubic carbides TiC, TaC and/or NbC, the insert being at least partly coated with a 11-19 mm thick coating including at least one layer of TiC xN y and an a-Al 2O 3 layer being the outer layer on the rake face and on the cutting edge line, and that on said at least one rake face the TiC xN y-layer has a thickness of from 4 to 12 mm and a tensile stress level of 50-500 MPa and the a-Al 2O 3-layer having a thickness of from 8 mm to 12 mm and has a mean Ra value MRa < 0.12 mm, at least in the chip contact zone on the rake face, and on said at least one clearance face the TiC xN y-layer has a tensile stress in the range 500-700 MPa and the a-Al 2O 3-layer is covered with a thin 0.1-1 mm TiN, TiC xN y,ZrC xN y or TiC layer giving the insert a different colour on this face.