IMPROVED TOOL PERFORMANCE THROUGH METASTABILITY IN HARD COATINGS

As a basis for modeling fractural mechanics, a new concept of PVD coat ings has been developed using an advanced cathodic are technology. In comparison with the well-known TiN and TiCN, tests in several applicat ions show that this concept can be a new approach to optimize tool lif etime and wear resistance. The specific features of the applied PVD ca thodic are technology allows the deposition of partially metastable co atings, The use of the concept leads to an increased fracture toughnes s of the coating without the need of reaching hardness values towards that of diamond. The metastability of a part of the grains in the coat ing allows absorption of the propagation energy of the microcracks and therefore reduces the mechanical wear. With such coatings, solutions for dry machining, for machining stainless steels and other difficult materials can be offered to manufacturers of tools and to end-users. T he validity of this 'metastability' model will be discussed and must b e studied through additional tests measuring the improved fracture tou ghness of the coatings. This type of PVD metastable coatings in combin ation with soft top layers like MoS2 appears to have a promising futur e. (C) 1997 Elsevier Science S.A.