TiN/NbN superlattice hard coatings deposited by unbalanced magnetron sputtering

TiN/NbN superlattice hard coatings were deposited using unbalanced magnetron sputtering technology. A gas manifold was used to generate a desired N-2 partial pressure for each target, so as to produce stoichiometric TiN and NbN simultaneously. During film deposition, an optical emission monitor (OEM) was used to monitor and control the poisoning status of the targets. Under optimized deposition conditions, the TiN/NbN superlattice coatings deposited on high-speed steel substrates had a well-defined superlattice structure and sharp interfaces as well as stoichiometric composition. These coatings show high toughness, high elasticity and very high hardness, giving rise to significant improvements in tribological performance. The nano-indentation hardness of 48 GPa was achieved in the coatings with an optimized superlattice wavelength of about 7 nm. This super-high hardness coupled with high elasticity implies that TiN/NbN superlattice coatings could be ideal for tools application, especially in the stamping/cutting tooling industry. (C) 1999 Elsevier Science S.A. All rights reserved.