Frictional energy, i.e. the multiplication of frictional force and sliding path, is frequently used to characterize tribosystems and their wear behavior e.g. under fretting or ultra-mild sliding wear. While energy-based wear rates, e.g. in units of µm³/J, may be used to differentiate between wear states of a specific tribosystem, no general numbers are known e.g. for the energy needed to produce a certain amount of wear at a particular wear mechanism and material.
In the present work steel X30CrMoN15-1 was tested as base body against 100Cr6 bearing balls as counterbody a ball-on-flat configuration. Reciprocating sliding wear tests were conducted at a normal force of 30 N and an average sliding speed of 0.06 m/s at room temperature. Different lubricants were applied: silicone oil, commercial gear oil and polyalphaolefin (PAO) with and without additives. The number of sliding cycles for the test series was chosen in such way, that all tribosystems with different lubricants encountered the same value of total frictional energy by the end of testing time. Wear mechanisms are studied by scanning-electron-microscopy, and wear volumes are determined by confocal microscopy.
As to be expected, both friction and wear were reduced significantly by additives in the lubricants. This effect was not levelled out by the additional sliding cycles applied. No correlation was found between the introduced total frictional energy and the measured wear volumes. This can partially be explained by the different acting wear mechanisms. Still, this work leads to the conclusion that averaging the frictional energy is not suitable to describe the progress of wear in the studied tribosystems. It is assumed that fluctuations of friction and specific events during testing need to be observed at high temporal and possibly spatial resolution, in order to observe correlations with the progress of wear.