Abstract
Multilayered CrAlN and SiN x films were deposited periodically by radio frequency reactive magnetron sputtering. In the CrAlN/SiN x multilayered coatings, the thickness of CrAlN layer was fixed at 4 nm, while that of SiN x layer was adjusted from 4 nm to 0.3 nm. The dependence of the SiN x layer thickness on the preferred orientation, crystalline behavior and mechanical properties of multilayered coatings were discussed with the aid of XRD patterns and HRTEM. It was demonstrated that amorphous SiN x layer transformed to a crystallized one when the thickness decreased from 4 nm to 0.3 nm. The crystalline SiN x layer grew epitaxially, formed the coherent interface with the CrAlN layer, and the columnar structure was exhibited. The critical layer thickness for the transition from amorphous SiN x to a crystallized one was found to be around 0.4 nm, and maximum hardness of 33 GPa was revealed. © 2009 Elsevier B.V. All rights reserved.