Improvement of the Ti-6Al-4V Alloy’s Tribological Properties and Electrochemical Corrosion Resistance by Nanocomposite TiN/PEEK708 Coatings

Abstract

Abstract In this work, polyetheretherketone-based TiN/PEEK708 nanocomposite coatings on oxygen hardened Ti-6Al-4V titanium alloy substrates were fabricated by using cathodic electrophoretic deposition and post-heat treatment. The microstructure of coatings was investigated by using scanning electron microscopy, transmission electron microscopy, and X-ray diffractometry. The scratch resistance, tribological properties, and electrochemical corrosion resistance were also studied. The results show that homogeneous TiN/PEEK708 coatings may be deposited from ethanol-based suspensions containing cationic chitosan polyelectrolyte, which provides electrosteric stabilization of the suspension. Heat treatment densified the coatings and changed the PEEK structure from amorphous to semi-crystalline. The coatings were characterized by very good scratch resistance, with no cohesive and adhesive cracks being observed up to the load of 30 N. They reduced the coefficient of friction from 0.70 for the baseline alloy and 0.65 for the oxygen hardened alloy to 0.30. They also significantly increased the wear resistance of the alloy during dry sliding contact with an alumina ball. The wear rate of the coated oxygen hardened alloy was about 70 and 650 times lower in comparison with the oxygen hardened and baseline alloy, respectively. The corrosion studies demonstrated that the baseline and oxygen hardened alloy have comparable corrosion resistance. The TiN/PEEK708 coating enhanced the electrochemical corrosion resistance of the alloy in the NaCl aqueous solution.