Microstructures and mechanical properties evaluation of TiAlN/CrSiN multilayered thin films with different bilayer periods

The Ti0.45Al0.55N/Cr0.75Si0.25N nanoscale multilayered coatings were deposited periodically by a bipolar asymmetric pulsed DC reactive magnetron sputtering technique. The structures and bilayer period of multilayer coatings were characterized by an X-ray diffractometer. The surface and cross-sectional morphologies of thin films were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. The surface roughness of thin films was explored by atomic force microscopy (AFM). A nanoindenter, a micro Vickers hardness tester and pin-on-disk wear tests were used to evaluate the hardness, fracture toughness and tribological properties of the thin films, respectively. Six coatings with bilayer period ranges from 6 nm to 40 nm were produced in this work. It was observed that the hardness increased with increasing bilayer period and reached the maximum at 12 nm and then leveled off at periods larger than 12 nm. An optimal hardness, and plastic deformation resistance, as well as adequate tribological behaviors were found on the coating with a critical bilayer period of 12 nm.