Multilayered and nanolayered hard nitride thin films for a better yield in micro machining

TiN/AlTiN ; TiN/CrN and CrN/AlTiN multilayer coatings have been deposited by the cathodic arc evaporation technique. The period is in the range 7 – 200 nm for a total thichness of 3 μm. The period’s control of the nanoscaled hard films is achieved, a priori, by way of a simple geometrical calculation and, a posteriori, via both X-ray diffraction and transmission electron microscopy on cross-sections. Microstructure of the as-deposited coatings has been investigated by means of Xray diffraction and transmission electron microscopy in connection with the decrease of the period λ. For lower periods (multilayered coatings), the fcc structures, which derive from each nitride are observed while only the superlattice structure is found for nanoscale layered films (nanolayered coatings). Microstructure evolution with the period (defined as the sum of two elementary layers) is investigated for the three systems and the differences are comment. Mechanical and tribological properties are strongly dependant on coating structure. The best mechanical properties were obtained with TiN/AlTiN nanolayers with 7 nm periods and superlattice structure [1]. These coatings induced low main cutting force and low flank wear during Inconel 718 turning. Time life of superlattice TiN-AlTiN coated cutting tool is increased comparatively to CVD coated and AlTiN coated cutting tools actually used in production.