Tribological characteristics of WS2/MoS2 solid lubricating multilayer films

Sputter-deposited MoS2 films have been often used as dry lubricant in various industrial fields, such as space applications. Most investigations have been focused on the reduction of the friction coefficient. However, mechanical components require not only stable lubricating films for friction reduction, but also excellent wear resistance for prolonged endurance life. Therefore, in this work, anti-wear properties of WS2/MoS2 nanometer-scale multilayers have been investigated, because a nanometer-scale multilayer film, so-called superlattice structured film, is expected to show good mechanical properties, such as high hardness and high stiffness, resulting in a low friction and long endurance lives. WS2/MoS2 nanometer-scale multilayer films have been prepared by multi-target RF sputtering. Single-layer MoS2 and WS2 films were also prepared for comparison. Ball-on-disk wear tests and nono-indentation tests were performed on the films grown onto Si substrates. WS2/MoS2 multilayer film showed a significantly improved tribological performance in air compared to the single-layer MoS2 or WS2 film, with an improvement in wear life of approximately seven times, and with a low friction coefficient of approximately 0.05.