The Influence of Tribolayer Formation on Tribological Performance of Rolling/Sliding Contacts

In the present study, a series of dedicated experiments has been performed to observe and measure the build-up of ZDDP tribolayer in rolling/sliding heavily loaded mixed-lubricated contacts. The experiments were carried out using several test configurations. First, ball-on-disc tests were run to investigate the effects of the contact pressure, temperature, and roughness on tribolayer formation. Then, micropitting tests were carried out, with bearing components and with rolling bearings, in order to evaluate the influence of tribolayer build-up on the tribological performance of the rolling/sliding contacts. The obtained experimental data were used first to calibrate a specially developed thermomechanical model and secondly to validate it under different operating conditions and at different levels, up to assessment of the tribological performance, by measuring the level of micropitting on the surfaces. The results show that a relatively simple thermomechanical model can account for tribolayer formation and removal and their effects on the contact performance in a relatively consistent way.