Study on the tribological properties of metal rolling bearing under lubrication with diketone lubricants

In this article, 1-(4-ethylphenyl)-nonane-1,3-dione (0206) was prepared by Claisen condensation. By mixing 0206, chelate, and base oil in a ratio of 3.2:4.8:2, a diketone lubricant (PAO=14 (20%)) that can achieve superlubricity was prepared and applied to bearing lubrication experiments. The experimental results show that when the bearing was lubricated by base oil, the friction coefficient (COF) and temperature rise decreased with the decrease of the viscosity of PAO. When PAO=14 (20%) was used as the lubricant, the COF of the bearing was the lowest (0.001), and the wear morphology was comparable to that of the bearing lubricated with commercial lubricant. Compared with the base oil with the same viscosity, it is found that the COF and temperature rise of the bearing lubricated by PAO=14 (20%) were lower under any experimental conditions. And when the amount of lubricant added was 10 µL, the COF of the bearing lubricated by PAO=14 (20%) reached a very low value (0.0004). Bearing ball surface analysis identified the formation of diketone adsorption films. Combined with the previous PAO=14 (20%) superlubricity mechanism, it was considered that the occurrence of tribochemical reaction and the bearing effect of chelates were the main reasons for the existence of ultra-low friction coefficient and low wear. In addition, when there were polar molecules in the lubricant, they were adsorbed on the metal surface through tribochemical reactions, resulting in many irregular pits on the surface.