Dry sliding tribological properties of Cu-WS2 self-lubricating composites at 25–500 °C

Abstract

Cu-WS2 composites are being used as self-lubricating materials for various engineering applications. The poor wettability between Cu and WS2 is a main obstacle for obtaining high-performance Cu-WS2. In order to improve the wettability, a thin Cu layer was deposited on the surface of the WS2 powder through an electroless plating technology. Cu-WS2 composites were prepared via spark plasma sintering (SPS) using the mix powders of Cu and Cu-WS2. Microstructure, mechanical properties and tribological properties of the Cu-WS2 composites were investigated, and that of the Cu were also comparatively studied. Results show that the WS2 powder coated with Cu (abbreviated as WS2@Cu powder) improves the poor wettability between Cu and WS2 and meanwhile the distribution of WS2. Cu-WS2 composites sintered below 750 °C could reduce the reaction between Cu and WS2 and ensure more WS2 in the composites. Both the coefficient of friction (COF) and the wear rate of the Cu-WS2 are lower than that of the Cu. A lubricant film leads to the excellent tribological properties as the Cu-WS2 composites were tested at 25−200 °C. However, the disappearance of WS2 and the formation of Cu2O cause to the decreasing self-lubricating performances at 300−500 °C. With an increase in the test temperature, the dominant wear mechanisms of the Cu-WS2 composites change from adhesive wear to a mixture of abrasive and oxidation wear, and that of the Cu change from adhesive wear to a mixture of fatigue and oxidation wear.

Keywords

• Cu-WS2 composites
• Wettability
• Spark plasma sintering
• Friction and wear