Rolling performance of carbon nitride-coated bearing components in different lubrication regimes

The performance of carbon nitride (CNx) coated roller bearings is investigated, using a micropitting rig. The rolling performance is evaluated using Stribeck test, with a continuously varying rolling speed (0.2 – 2 m/s). Rolling contact fatigue tests with constant speeds (0.5, 1, 2, and 3.5 m/s) are also conducted in order to study the high-cycle performance of the rollers. The obtained Stribeck curve shows that the presence of coatings eliminates run-in, resulting in low friction coefficients (∼0.08). Raman spectroscopy, performed at the wear tracks, reveals that CNxmaintain stable chemical state. Coatings show abrasion although the wear rate is not detrimental for the performance of the rollers, since a CNx-to-steel contact is retained during the entire rolling contact fatigue test.