TRIBOLOGICAL CHARACTERISTICS OF RADIAL JOURNAL BEARINGS BY ULTRASONIC NANOCRYSTAL SURFACE MODIFICATION TECHNOLOGY

Ultrasonic nanocrystal surface modification (UNSM) has applied to a radial journal bearings made of bearing steel SUJ2. Mechanical characteristics are compared between UNSM treated and untreated bearings. Friction torque is measured at the boundary lubrication condition, the mixed lubrication condition, and the full hydrodynamic lubrication condition. The peak torque at the boundary lubrication condition and the transition period to mixed lubrication condition on the UNSM treated samples are reduced. These effects are very useful to improve the service life of journal bearings. The Stribeck curve at the mixed and full hydrodynamic lubrication is derived and compared. The friction coefficient at these two regimes is reduced by more than 50%, which will do effective role for improvement of energy efficiency. The major effects for this reduction at three lubrication regimes could be explained in the terms of micro dimple surface.