Patent ID: RE40873

Claim:
A method of making a cutting tool, the cutting tool comprising a WC—Co based cemented carbide body comprising WC with an average grain size of about 1.4 μm, 12-13 wt-% Co and 0.4-1.8 wt-% TaC+NbC, and a W-alloyed binder phase with a CW-ratio of 0.82-0.91, the method comprising: applying a first innermost 0.1-0.5 μm bonding layer of TiN to the body; applying a second layer comprising a mutlilayered structure comprising a plurality of 0.05-0.2 μm thick sublayers of a composition (Ti x Al 1-x )N in which x varies repeatedly between the two ranges 0.45<x<0.55 and 0.70<x<0.80, a first sublayer of (Ti x Al 1-x )N adjacent to the TiN bonding layer having an x-value of 0.45<x<0.55, a second sublayer of (Ti x Al 1-x )N having an x-value of 0.70<x<0.80 and a third sublayer having x in the range 0.45<x<0.55, the sequence of sublayers alternating and repeating until 12-25 sublayers are built up; applying a third 0.1-0.5 μm thick layer of (Ti x Al 1-x )N, where x is 0.45<x<0.55; and applying a fourth outermost 0.1-0.2 μm layer of TiN; wherein the total coating thickness close to a cutting edge of the tool is in the range of 1-8 μm and the thickness of the second layer constitutes 75-95% of the total coating thickness.