Microstructure and mechanical properties of (Ti,Al)(O,N) films synthesized by reactive sputtering

A series of (Ti,Al)(O,N) films were synthesized in a gaseous mixture of Ar, N2 and O2 by the reactive magnetron sputtering method using a Ti–Al mosaic target. Energy dispersive spectroscopy, X-ray diffraction, transmission electron microscopy, scanning electron microscopy, atomic force microscopy and nanoindentation were employed to investigate films' chemical composition, microstructure and mechanical properties. The results show that oxygen content in the films increases with the rising O2 partial pressure and nitrogen content decreases correspondingly; on the other hand, the atom ratio, (Ti + Al) / (O + N) keeps close to a stoichiometric constant of 1. (Ti,Al)(O,N) films present the same NaCl structure as the (Ti,Al)N film and columnar crystals with a (200) texture. Meanwhile, hardness and elastic modulus of (Ti,Al)(O,N) films maintain 35 GPa and 370∼420 GPa, respectively, as high as those of the (Ti,Al)N film.