Fretting Wear Behavior and Photoelectron Spectroscopy (XPS) Analysis of a Ti/TiN Multilayer Film Deposited on Depleted Uranium

Depleted uranium has been widely applied in nuclear energy fields. However, its poor corrosion and wear resistance restrict its applications. A titanium/titanium nitride (Ti/TiN) multilayer film was deposited on a uranium surface to improve its fretting wear resistance. Fretting wear tests were carried out using a pin-on-disc configuration. The fretting behaviors of uranium and the Ti/TiN film were investigated under different normal loads. With the normal load increasing, the mode of fretting wear gradually transformed from slip region (SR) to mixed fretting region (MFR) and then to partial slip region (PSR). It is illustrated that the normal load had an obvious effect on the fretting wear behavior. The friction coefficients of both uranium and Ti/TiN multilayer film decreased with the increase of the normal load. In SR, the main wear mechanisms were delamination and abrasion for uncoated uranium, and delamination and oxidation for uranium coated with the Ti/TiN multilayer film. Photoelectron spectroscopy (XPS) analysis also showed that the Ti/TiN coating was oxidized and formed TiO2 during fretting wear. The wear depth of naked uranium was much greater than that of coated uranium, which demonstrated that the Ti/TiN multilayer film could effectively improve the wear properties of uranium.