DEVELOPMENT OF A GRADED TICN COATING FOR CEMENTED CARBIDE CUTTING TOOLS - A DESIGN APPROACH

Cemented carbide cutting tools containing a high percentage of cobalt binder (9-13%) are used for rough machining applications involving interruptions, owing to their high fracture toughness. However, these tools are prone to deformation under such conditions. A design approach can be effectively used to develop a coating scheme which optimizes the critical properties of such coatings for improved tool life. In this paper, we discuss the design and development of chemical-vapor-deposited (CVD) TiCN/TiN multilayer coatings applied to a WC-12% Co tool substrate. The performance of the coated tool is compared with a conventional tool coated with a single, monolithic CVD TiN layer, and it is shown that a judicious combination of coating compositions can be tailored to meet the operating requirements. The interactive aspects of the wear resistance of the coating and deformation resistance of the coated tool during machining are highlighted in the turning tests on low alloy steel.