The objective of the present paper is to study the influence of the substrate bias voltage on the microstructure, composition, deposition rate, tribological and corrosion properties of CrN coatings obtained by DC magnetron sputtering on 90CrMoV8 steel and Si (100) substrates. The substrate bias voltage varied from 0 to 2 700 V. The deposited films were characterized by SEM, XRD and potentiodynamic polarization. The wear behavior and coefficient of friction were determined and investigated after rotative tribometer tests. The results indicated that the substrate bias voltage considerably affected the intrinsic properties of the CrN films. Indeed, it significantly influenced the grain size and the root-mean-squared roughness which varied from 20 to 29 nm, and from 9 to 19 nm, respectively, when polarization changed from 0 to 2 700 V. All the CrN coatings have a dense columnar structure and are well crystallized according to the XRD analyses. Nevertheless, it has been shown that the peaks intensity decreased by increasing the substrate bias voltage. By applying a substrate bias voltage, it was obvious that the friction behavior was enhanced, and the wear volume was decreased. Finally, the CrN coating obtained under a substrate bias voltage of 2 500 V presented the best corrosion resistance and wear resistance probably due to its dense microstructure.

CrN/CrAlN thin films were deposited by DC reactive magnetron sputtering. The influence of CrN/CrAlN bilayer thickness on the microstructure, mechanical, and tribological properties was studied. Crystallinity of the layers was characterized by x-ray diffraction. The microstructure of all coatings was observed by scanning electron microscopy. Results exhibit that bilayer thickness was a dominant factor. The analyses showed a columnar microstructure for the CrN/CrAlN coatings. Owing to their denser structure and interfacial strengthening, CrN/CrAlN multilayer coatings exhibited higher mechanical properties than that of monolayers. Indeed, CrN/CrAlN multilayer coating with four bilayers and thickness gradient reaches a maximum of hardness around 43 GPa. Also, its resistance to spallation reaches 97 N which is a very excellent value. After ball-on-disk wear tests, it is found that all multilayer films exhibited a good wear resistance, especially the one with four bilayers and different CrN and CrAlN monolayers thickness. The lowest coefficient of friction is obtained for the coatings with 4 bilayers.