Performance of PVD TiN/TaN and TiN/NbN superlattice coated cemented carbide tools in stainless steel machining

摘要

Cemented carbide cutting tools coated with superlattice TiN/TaN and TiN/NbN lamellae thin films were evaluated in face milling machining tests of austenitic stainless steel (AISI/SAE 303/304). The coatings were grown by PVD on cemented carbide inserts by a combination of ion plating of TiN and reactive magnetron sputtering of NbN and TaN. The lamellae coatings were macroscopically disordered as a consequence of the relatively rough surface of the carbide substrate, but the coatings did exhibit a microscopic superlattice structure. For both TiN/TaN and TiN/NbN, the two constituent layers of the superlattices crystallized in the cubic B1 structure. The TiN/NbN lamellea coating showed a Vickers microhardness (HV0.5 N) of 32 GPa and the TiN/TaN lamellea coating exhibited a HV0.5 N value of 39 GPa. The results from the machining tests indicate a superior performance of tools coated with the harder lamellae coatings as compared to tools coated with single layer PVD or CVD coatings. (C) 1998 Elsevier Science S.A. [References: 12]