Effects of atomic oxygen exposure on tribological property of zirconium alloy

ZrTiAlV alloy has potential applications in space mechanisms. The change of wear and the friction coefficient of the ZrTiAlV alloy subjected to atomic oxygen (AO) exposure were investigated aiming to evaluate the tribological properties influenced by the atomic oxygen (AO) environment of the low Earth orbit (LEO). The AO testing employing a 5 eV AO beam was performed under various AO fluencies. The mass loss and roughness of the exposed to AO surfaces were measured. The exposed surfaces and the worn surfaces were analyzed using scanning electron microscopy (SEM) and X-ray photoelectron spectrometry (XPS) to explore the mechanism of AO effect. The results show that, the friction coefficient at the initial friction stage and the wear loss are increased after AO exposure. The exposure to energetic AO beam leads to mass loss and decrease in roughness, showing a polishing effect on the exposed surface. Comprehensive analysis indicated that the AO interaction with the exposed surface results in two simultaneously occurring phenomena, i.e., the growth of surface oxides and their spalling. The wear loss and friction coefficient exhibit a non monotonous variation with AO fluence under the competition of these two processes.