Microstructure and mechanical properties of (Al, Ti)(O, N) coatings prepared by reactive sputtering

A series of (Al, Ti)(O, N) coatings were synthesized in a gaseous mixture of argon, nitrogen and oxygen by reactive sputtering method using a Al–Ti mosaic target. Energy dispersive spectroscopy, X-ray diffraction, atomic force microscopy, transmission electron microscopy and nanoindentation were employed to investigate these coatings’ chemical composition, microstructure and mechanical properties. Experiment results show that with the increase of O2 partial pressure in the mixed atmosphere, oxygen content in the coatings increases and nitrogen content decreases correspondingly; while the atom ratio, (Al + Ti)/(O + N) keeps in a stoichiometric constant of about 1. All of these (Al, Ti)(O, N) coatings present a NaCl structure, the same as that of (Al, Ti)N coating. But they change their growing preferred orientation with the increasing oxygen content, exhibiting a typical columnar crystal structure with a (2 0 0) texture at high oxygen content. Meanwhile, the hardness of all (Al, Ti)(O, N) coatings remains in the level of about 35 GPa, close to that of the base material (Al, Ti)N coating.