Tribocorrosion behavior of TC18 titanium alloy: A discussion about the interaction between galvanic corrosion and wear.

Titanium and aluminum couplings are susceptible to both corrosion and wear during their service life. When the passive film on the titanium surface is worn off, the galvanic effect will affect the corrosion-wear interaction, and tribocorrosion mechanism is altered accordingly. A combination of electrochemical techniques (Potentiostatic and Potentiodynamic Polarization), characterization of wear scar morphology (Scanning Electron Microscope, SEM and a 3D profilometer), and analysis of wear debris composition (Surface-Enhanced Raman Spectroscopy, SERS) were employed to clarify the tribocorrosion mechanism. The results show that the wear effect is predominant for the tribocorrosion of TC18 titanium alloy, and the corrosion-induced wear increment mainly comes from the ploughing effect of regenerated passive film. When the titanium alloy is coupled with aluminum, the corrosion acceleration is weak, while the cathodic reaction increases due to the negative shift of the corrosion potential. This results in the regenerated passive film containing a higher proportion of easily sheared low-valent titanium oxides and titanium hydrides, promoting the wear rate. • The tribocorrosion mechanism of TC18 titanium alloy is mainly controlled by wear. • The wear increment under applied potential comes from the ploughing effect of regenerated passive film. • Al has little effect on the corrosion acceleration of worn TC18 but it promotes wear rate. • With Al coupled, the enhanced cathodic reaction changes the surface state of wear scar. • More easily-sheared low valence titanium oxides and titanium hydroxide are formed in wear scar. [ABSTRACT FROM AUTHOR]