Macroscopic oil-based superlubricity achieved on steel surfaces with the roughness of engineering level

In this work, the lubricating performance of 1,3-diketone oil was tested on steel surfaces with roughness grades in three different orders of magnitude. The results indicate that 1,3-diketone achieved superlubricity on both the smooth engineering surface (Sa = 17 nm) and a typical engineering surface (Sa = 202 nm). Remarkably, the superlubricity is obtained at a shorter running-in time on the rougher surface than on the smoother one. This is due to an accelerated tribochemical reaction by increasing the surface contact with the 1,3-diketone. In contrast, superlubricity is not achieved on the roughest surface (Sa = 2171 nm) due to the excessive consumption of 1,3-diketone oil and the large abrasive particles produced. This is the first paper to report oil-based superlubricity on steel surfaces with a roughness of around 200 nm. These results confirm the successful superlubricity of engineering steel with 1,3-diketone oil, which has an excellent prospect for industrial applications.