Towards eliminating friction and wear in plain bearings operating without lubrication

Abstract

Plain bearings, owing to their versatility and simplicity, are extensively utilized in engineering design across a variety of industries involving moving parts. Lubrication is vital to the functioning of these bearings so their usage is inhibited under dynamic load conditions or at elevated or reduced temperatures due to this dependency on lubrication. This study introduces an innovative method to significantly mitigate friction and wear in plain bearings operating without lubrication. The plain bearings were constructed from steel-bronze pairs, where the steel shafts were alloyed with bismuth oxide via short-pulse laser treatment. To incorporate the bismuth oxide into the surface layers of the steel, MnO2 was utilized as a carrier. Insights from transmission electron microscopy and X-ray photoelectron spectroscopy exposed a highly non-equilibrium state of matter, which is unattainable through conventional engineering methods. The tribological performance of the modified steel disks was assessed via a block-on-ring sliding test, demonstrating superior wear and friction performance without lubrication, and an ultra-low coefficient of friction. Remarkably, the modified friction pairs remained functional after 200 km of linear sliding at a load of 250 N (12.5 MPa) and a sliding speed of 9 m/s. To substantiate the technique's viability, we tested the performance of an internal combustion engine turbocharger fitted with a modified steel shaft. The turbocharger's performance validated the long-term effectiveness of the steel-bronze coupling operating without lubrication at 75,000 rpm. The simplicity and resilience of this technique for modifying steel-bronze pairs offer a ground-breaking and promising approach for a wide range of applications.