Patent ID: 6183846
Filing Date: 2001-02-06
Classification: C23C,Y10T

Abstract:
A coated hard metal material for a cutting tool comprising a base material selected from the group consisting of cemented carbide and cermet, and a hard coating layer on a surface of said base material, whereinsaid hard coating layer comprises:an inner layer that is arranged on said base material, that consists essentially of at least one layer of a material selected from the group consisting of a carbide, a nitride, a carbo-nitride, a carbo-oxide, a carbonitrogen oxide and a boronitride of Ti, and that has a thickness in the range from 0.1 to 5 .mu.m,an intermediate layer that is arranged on said inner layer, that is mainly composed of an oxide selected from the group consisting of Al.sub.2 O.sub.3 which is mainly composed of .alpha.-Al.sub.2 O.sub.3, ZrO.sub.2 and a mixture or a solid solution thereof in which one of Al.sub.2 O.sub.3 and ZrO.sub.2 predominates, and that has a thickness which is in the range from 5 to 50 .mu.m when said intermediate layer is mainly composed of said Al.sub.2 O.sub.3 and in the range from 0.5 to 20 .mu.m when said intermediate layer is mainly composed of said ZrO.sub.2, andan outer layer that is arranged on said intermediate layer, that consists essentially of at least one layer composed of TiCN, having a molar C:N ratio in the range of 5:5 to 7:3, and composed of columnar crystals having an aspect ratio in the range from 5 to 80, and that has a thickness in the range from 5 to 10 .mu.m.