Patent ID: RE39814

Claim:
A coated cemented carbide cutting tool comprising: a WC—Co based cemented carbide body comprising a composition of 9-12 wt % Co, 0.2-2.0 wt % cubic carbides from elements from group IVa, Va or VIa of the periodic table and balance WC with an average grain size of the WC of 1.5-2 μm and a W-alloyed binder phase with a CW-ratio in the range of 0.77-0.95; and a hard and wear resistant coating deposited on the WC—Co cemented carbide body comprising: a first innermost bonding layer of TiN; a second layer comprising a multilayered structure of 0.05-0.2 μm thick sublayers of the 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, the first sublayer of (Ti x Al 1−x )N adjacent to the TiN bonding layer having an x-value in the range 0.45<x<0.55, the second sublayer of (Ti x Al 1−x )N having an x-value in the range 0.70<x<0.80 and the third sublayer having an x value in the range 0.45<x<0.55 and so forth repeated until 8-30 sublayers are built up; a third at least 0.2 μm thick layer of (Ti x Al 1−x )N, where x is in the range 0.45<x<0.55; a fourth outermost layer of TiN; wherein the total coating thickness is in the range of 2-9 μm and the thickness of the second layer constitutes 75-95% of the total coating thickness.