Patent ID: RE40082

Claim:
A method of making a milling insert comprising a cemented carbide body and a coating wherein the WC-Co-based cemented carbide body comprises WC, 7.3-7.9 wt. % Co and 1.0-1.8 wt. % cubic carbides of Ta and Nb and a highly W-alloyed binder phase with a CW-ratio of 0.86-0.94, the method comprising the steps of: depositing by a CVD-method a first, innermost layer of TiC x N y O z with x+y+z=1, y>x and z<0.2 having an equiaxed grain structure with a size <0.5 μm and a total thickness of 0.1-1.5 μm; depositing by a MTCVD-technique a layer of TiC x N y with x+y=1, x>0.3 and y>0.3 with a thickness of 1-4 μm having a columnar grain structure with an average diameter of <5 μm, wherein the MTCVD-technique uses acetonitrile as a source of carbon and nitrogen for forming a layer in a temperature range of 700-900° C.; depositing a layer of a smooth κ-Al 2 O 3 with a thickness of 1-2.5 μm; and depositing an outer layer of TiN with a thickness of 0.5-1.0 μm.