Influence of ultraviolet irradiation on the surface chemistry and tribological properties of water-glycol lubricated Al-Mg-Ti-B coatings

In this work, we studied the effect of ultraviolet (UV) irradiation on the surface chemical states and tribological properties of the water-glycol lubricated Al-Mg-Ti-B coatings by pin-on-disk unidirectional sliding test and X-ray Photoelectron Spectroscopy (XPS). XPS results indicate that boric acid is present at both the wear track and unworn surface of the UV-irradiated Al-Mg-Ti-B coating, as opposed to the case of Al-Mg-Ti-B coating untreated by UV irradiation, in which there is no clear evidence of the boric acid formation. We believe this is due to the UV-induced strong hydrophilicity in the presence of anatase TiO2. In addition, the observed distinct surface chemistries result in the different tribological behaviors for these coatings. This study, thereby, provides further insights into the role of anatase TiO2 in the tribological characteristics of Al-Mg-Ti-B coatings.