In this research CrN/CrAlN nanostructured multilayer coatings were deposited on AISI 420 substrate by cathodic arc PVD. To evaluate the effect of number of layers on corrosion properties, coatings of 7 and 13 layers were compared with top layer of CrCN. Crystalline structure and grain size of coatings were studied by X-ray diffraction, thickness, surface topography and morphology of the coatings by SEM and FESEM, and macroparticles inside the coatings were measured by using MIP software. Chemical analysis by EDS revealed Al/Cr ratio equal to 1.63 in CrAlN layers. Average coating roughness was 0.62 and 0.2 µm before and after polishing, respectively. Coating adhesion, evaluated at two substrate roughness of 0.02 and 0.06 µm by Rockwell C indenter test, proved better adhesion on rougher substrate. Examination of fracture surface using SEM showed a brittle mode on the coating section. Mechanical properties were evaluated by nanohardne hardness 2500 HV, elastic modulus 303GPa and stiffness 0.16mN/nm were obtained. Corrosion behavior of the coatings was investigated by using EIS and potentiodynamic polarization in 3.5 wt% NaCl solution. EIS test showed that corrosion properties of 13 layer coating was superior to that of 7 layer specimen. Results of potentiodynamic polarization tests showed that 13 layer coating had lower corrosion current density and higher corrosion potential. Moreover, the number and size of pits created in the coating proved higher corrosion resistance of 13 layer specimen. Surface roughness and presence of droplets on the coating decreased corrosion resistance. Salt spray tests after 400 h showed a superior behavior of 13 layer coating with a lower degradation of the surface. The synergistic effect of wear and corrosion was studied in tribo-corrosion testing of the coatings. Under an applied load of 6 N, the friction coefficient was obtained 0.12. Active spots were created on the surface due to partial coating removal as a result of wear, thus, varying the open circuit potential during sliding process.
