Abstract: A series of TiAlN/ AlON nanomultilayers with various AlON layer thicknesses are synthesized by reactive magnetron sputtering. The microstructure and mechanical properties are evaluated by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and nano-indentation. The results reveal that, under the template effect of TiAlN layers, amorphous AlON is forced to crystallize and grows epitaxially with TiAlN layers when AlON layer thickness is below 1 nm, and the nanomultilayer appears superhardness effect with the maximum hardness and elastic modulus of 38.1 GPa and 385.6 GPa when AlON layer thickness is 0.7 nm. As the AlON layer thickness exceeds 1 nm, AlON transforms into amorphous state and breaks the coherent growth of multilayers, resulting in the decrease of hardness and elastic modulus. Therefore cutter protective coatings which possess not only better mechanical properties but also good oxidation resistance at high temperature are synthesized by this mechanism to meet modern cutting.

Key words: Amorphous crystallization, Coherent growth, Magnetron sputtering, Superhardness effect, TiAlN/AlON nanomultilayers