Multilayer coated hard alloy cutting tool

摘要

The present invention concerns a tungsten carbide base cutting tools formed on sintered hard alloy substrate material. Multiple hard coatings are deposited on the Co-enriched surface layer of the substrate material, and the Co-enriched surface layer occurs within a surface layer region of 50 mu m from an interface of said substrate material, wherein the Co content in a surface layer that is 5-10 mu m from an interface of said substrate material is within a range from 15-25 % by weight; wherein the Co content in said surface layer is more than the Co content in the core; and wherein the content of the carbides of Ti, Ta and Nb is lower than that in the core. A surface region within a distance of 100 mu m to 400 mu m from said interface between coatings and substrate material is substantially free of said free carbon particles, while free carbon particles are present in a region of said core located beyond 100-400 mu m from said interface of said substrate material. The multilayer coating consists of a primary coating of TiCN, a secondary coating of Al2O3 and the surface coating consisting of at least one of TiCN and TiN.