Effect of WS2 Addition on Tribological Behavior of Aluminum at Room and Elevated Temperatures

The objective of this study is to evaluate the role of WS2-based two-dimensional material as solid lubricant additive to aluminum to reduce the friction. Al-2 vol% WS2 was consolidated by spark plasma sintering into a 99% dense composite. Tribological behavior of Al-2 vol% WS2 and pure Al was evaluated at room temperature and 200 degrees C using the ball-on-disk method in dry sliding wear conditions. Wear mechanism was studied using wear surface and sub-surface via electron microscopy and focused ion beam milling. Al-2 vol% WS2 showed the lowest coefficient of friction value of 0.55 at 200 degrees C as compared to 0.82 that of pure aluminum. The wear rate of Al-2 vol% WS2 showed 54 and 29% improvement at room temperature and 200 degrees C, respectively, as compared to pure Al. The improved tribological properties of Al-2 vol% WS2 are attributed to a tribofilm formation due to the breaking of the weak Van der Waals forces that hold the S-W-S structure. Due to shear forces, a portion of the tribofilm is transferred on the counter surface providing lubrication properties resulting in a stable and low COF.