Corrosion Behavior Evaluation of Nanolayered CrN/CrAlN Coatings on Titanium and Ti6Al4V Substrates

In recent years, implants are used as prostheses to replace and protect bone. Titanium, as an implantable material, needs to improve corrosion and wear properties for better performance. Therefore, in the current study nitride coatings were applied with the aim of improving corrosion and wear properties. Cathodic arc evaporation physical vapor deposition (CAE-PVD) technique was used to deposit nanolayered CrN/CrAlN coatings on commercially pure titanium and Ti6Al4V substrates for biomaterial applications. X-ray diffraction (XRD) was used to characterize the crystal structure of the coating, and scanning electron microscopy (SEM) and field emission scanning electron microscopy (FESEM) were utilized to observe the surface morphology and cross-section of the coating. The coating adhesion was measured according to VDI 3198 standard using a Rockwell-C indenter. The corrosion behavior was evaluated by potentiodynamic polarization and spectroscope electrochemical impedance in Ringer's solution. The results showed that the nanolayered coating changed the corrosion potential from -0.368 V to -0.054 V for the titanium sample and from -0.405 V to -0.028 V for the Ti6Al4V specimen. Additionally, the corrosion current density was reduced to about one-eighth and a third for the titanium and Ti6Al4V coated samples, respectively. The capacitator circle diameters increased due to the deposition of CrN/CrAlN coating, demonstrating enhanced corrosion behavior of the coated samples compared to uncoated specimens, as the coating acted as a barrier against corrosive liquids accessing the substrate.