Atomic aluminum content (x) effect on fretting-corrosion of Ti1−xAlxN coatings for orthopedic applications

• The effect of aluminum content on fretting corrosion behavior of Ti–Al–N was studied.
• Tests were performed using animal bone as counterpart and a simulated body fluid.
• Fretting-corrosion against bone can damage the metal and coatings.
• The wear volume loss is related to the corrosion resistance and H/E ratio.
• Ti–Al–N improved the wear resistance of the stainless steel in simulated body fluid.

Normal micro-movements at the bone-implant interface originate fretting-corrosion processes, thus releasing wear debris from the bone and metallic devices and compromising the fixability of the implant. Titanium aluminum nitride (Ti1−xAlxN) coatings have been considered to overcome these drawbacks and the effect of aluminum content on the fretting-corrosion resistance against bone in a simulated body fluid has been studied. Coatings were synthesized by magnetron co-sputtering by varying the power applied to the aluminum target. Morphology and chemical composition were studied by optical profilometry, SEM and XPS. Coatings with x=0.39, 0.47, 0.61 and 0.69 were obtained. Mechanical properties, adherence and corrosion behavior were assessed by nanoindentation, scratch test and potentiodynamic curves, respectively. The fretting-corrosion behavior was assessed at open circuit potential (OCP) using a tribo-electrochemical apparatus, bone-pins as the counterpart and Hank׳s solution as the simulated body fluid. It was found that the fretting-corrosion against bone in the simulated body fluid can damage the metal and coatings, thereby accelerating wear and increasing the current corrosion densities. Coatings with x=0.39, 0.47 and 0.61 are able to protect 304SS against fretting corrosion. The behavior of wear volume with aluminum content in coatings is related to the corrosion resistance and hardness to elastic modulus ratio.