Tribological assessment of partially sulfidated molybdenum oxide

Molybdenum sulfide is widely used as an additive in lubricated systems due to its van der Waals forces and its sliding sheets that produce low friction coefficients. Different morphologies and chemical compositions have been tested with good performance. In all circumstances, the behavior of sulfurized structures in the presence of oxygen remains unwanted. In this work, molybdenum oxide with hexagonal and orthorhombic phases crystalline structures and molybdenum oxide partially sulfidated were tested in boundary-lubrication range. The results show that partially sulfidated molybdenum oxide decreases the coefficient of friction despite the high oxygen content and it remains low during the entire test. The partially sulfidated materials present lower friction coefficients than pure oxides.