Preparation and characterization of wear resistant TiO layer on Ti alloy

Abstract

Titanium monoxide (TiO) is golden in color, and of good chemical inertness and high hardness, making it a potential candidate for decorative and protective coatings. In this study, a TiO layer was coated on Ti alloy substrate through a combination of cathode plasma electrolysis (CPE) and comproportionation between the Ti substrate and Ti4+ from the electrolyte. The thickness of the obtained TiO layer was around 500 nm, with a hardness of 11 GPa, a modulus of 220 GPa and a critical load of 55 N. The coefficient of friction of the CPE-treated sample vs. ZrO2 ball was decreased from 0.4 to 0.6 to around 0.2 when the Hertz pressure was less than 885 MPa. The wear rate of the CPE-treated sample was reduced by ~450 times compared with that of the untreated Ti alloy. Correspondingly, the wear rate of the ZrO2 ball was reduced by ~170 times. In addition, wear resistance of the CPE-treated samples was also significantly improved for common metallic materials (such as stainless steel, carbon steel, or copper alloy) as the counterpart. The surface morphology evolution and the mechanical properties of the TiO layer can avoid the severe abrasive wear as well as adhesive wear, and contribute to the excellent antiwear effects. CPE demonstrates a technologically relevant capability, especially in forming a TiO antiwear layer on Ti alloy.