Coated cemented carbide endmill

Method of making a cemented carbide endmilling comprising the following steps:

• providing a cemented carbide endmill blank with a composition comprising from about 90 to about 94 wt % WC in a binder phase of Co also containing Cr in such an amount that the Cr/Co weight ratio is from about 0.05 to about 0.18,
• wet milling submicron powders of tungsten carbide cobalt, at least one of Cr3C2, Cr23C6 and Cr7C3 to obtain a slurry,
• drying the slurry to obtain a powder,
• pressing the powder into rods,
• sintering the rods in vacuum or in nitrogen, and
• optionally performing an isostatic gas pressure step during sintering temperature or at the final stage of sintering,
• grinding the rods cylindrical to h6 tolerance,
• grinding flutes using diamond wheels with emulsion cutting fluid,
• depositing whilst maintaining a partial pressure of nitrogen in the recipient, and using the appropriate selection of active evaporation sources and rates,
• a wear resistant coating (b) from about 1.8 to about 9.5 μm thick, comprising:
• a first layer (c) of a hard and wear resistant refractory PVD AlMe nitride or carbonitride where Me is Zr, V, Nb, Cr or Ti having a thickness of from about 1.0 to about 4.5 μm and an atomic fraction of Al to Me of from about 1.20 to about 1.50 with process parameters:
• arc current from about 50 to about 200 A in the equipment, N2-pressure from about 5 to about 50 μbar and deposition temperature from about 400 to about 700° C. and a substrate bias of from about −150 to about −300V,
• a second layer (d) of hard and wear resistant refractory PVD AlMe nitride or carbonitride where Me is Zr, V, Nb, Cr or Ti, having a thickness of from about 0.5 to about 4.5 μm and an atomic fraction of Al to Me of from about 1.30 to about 1.70 with process parameters:
• arc current from about 50 to about 200 A in the equipment, N2-pressure from about 5 to about 50 μbar, and deposition temperature from about 400 to about 700° C. and a substrate bias of about −50 to about −140 V, and
• in between the first and the second layers, a from about 0.05 to about 1.0 μm thick low-Al layer (e) at a temperature from about 400 to about 700° C., the substrate bias from about −30 to about 150 V and the arc current from about 80 to about 210 A.