Enhanced hardness in sputtered Zr–Ni–N films

Recently, it was found that the reactive magnetron sputtering of TiN films with the addition of small (≤ 10 at.%) amount of Fe makes it possible to change the preferred crystallographic orientation of grains in the film when the partial pressure of nitrogen pN2 in the sputtering gas is continuously increased. Between the films with different preferred crystallographic orientations there is a transition region (TR). The films produced inside TR are characterized by an X-ray amorphous structure. In spite of the fact that the films produced inside TR and outside of it strongly differ in their structure, both kinds of films exhibit an enhanced hardness [J. Musil, H. Polakova, J. Suna, J. Vlcek, Surf. Coat. Technol. 177–178 (2004) 289]. It was found that the enhanced hardness arises in two cases: (1) in the materials composed of a mixture of small grains of different crystallographic orientations, i.e. in the films produced inside TR, and (2) in the materials composed of nanocolumns perpendicular to the film/substrate interface, i.e. in the films produced outside TR. These findings are in an agreement with a new concept of nanocomposite phases with enhanced hardness based on the size of grains and the shape of crystallites [J. Musil, in: A. Cavaleiro, J.T.M. De Hosson (Eds.), Nanostructured Hard Coatings, Kluwer Academic/Plenum Publishers, New York, 2005, Chapter 10]. A development of mechanical properties of the Zr–Ni–N films with increasing pN2 is also discussed in detail.