Thermal-desorption behavior of MoS2−xOx solid-lubricant films sputtered on bearing rollers

Abstract

Mo S 2 − x O x films were prepared on the rollers of a cross-roller bearing by the radio-frequency magnetron-sputtering method. Outgassing properties of these rollers at various temperatures were measured by the thermal-desorption method. For film with oxygen content of 2.8at.%, the unique gases of M∕e=32 (S+) and 34 (H2S+) were detected at about 370 and 420K, respectively. These gases were not detected until 500K after baking at 393K for 24h. In order to understand the outgassing mechanism of these gases, the chemical structure of film surface was analyzed by x-ray photoelectron spectroscopy before and after the thermal-desorption spectroscopy (TDS) measurement. An increase of MoO2 and a decrease of free sulfur in the film were confirmed after the TDS measurement. This result suggests that MoO2, S, and H2S are produced by the chemical reaction between adsorption water and MoS2. In addition, it has been found that the detection temperature and peak temperature of H2S become high with the increase in the oxygen content in the film.