The Tribological Properties of Low-Sulfur and Low-Phosphorus Halogen-Free Ionic Liquids as Lubricants for the Nickel-Based Alloy Inconel 690

Abstract

In this study, we synthesized three low-sulfur and low-phosphorus ionic liquids (ILs). These were N88816P8, P88816P8, and P88816DOSS. The viscosity and thermal stability of the three ILs were analyzed. The tribological properties and lubrication mechanisms of the three ILs were investigated as lubricants for a carbide ball–Inconel 690 nickel-based alloy friction pair and compared at 50 °C and 150 °C. The wear spots of the carbide ball and nickel-based alloy disc samples were characterized using SEM and EDS. The experimental results revealed that P88816P8 had excellent tribological properties. The lubrication mechanism of P88816P8 as a lubricant for the carbide ball–Inconel 690 nickel-based alloy friction pair was investigated using XPS. The excellent friction reduction and anti-wear properties of P88816P8 could be attributed to the tribo-chemistry between P88816P8 and Inconel 690 as well as the formation of a tribo-film on the wear-spot surface. This high-performance IL, suitable for carbide ball–Inconel 690 contact, will be applied to a cutting process of Inconel 690.