Fretting Wear Study on Micro-Arc Oxidation TiO2 Coating on TC4 Titanium Alloys in Simulated Body Fluid

Tribological properties of TiO2 coatings synthesized by micro-arc oxidation (MAO) on the surface of TC4 titanium alloys were investigated at the fretting contact against 440C stainless steel in simulated body fluid (SBF). Fretting experiments were carried out by ball-on-flat contact at various loads for 1 h, with an amplitude of 100 mu m and a frequency of 5 Hz. Results show that MAO TiO2 coatings presented good tribological properties with lower friction coefficient in SBF. Less wear volume was observed for MAO TiO2 coatings compared with that for TC4 alloy. At lower load, the wear mechanism of MAO TiO2 coatings was dominated to abrasive wear. With an increase of normal load, however, fretting corrosion increased due to chemical reactions with SBF, and therefore, fretting fatigue coexisting with abrasive wear became the predominant mode.