Abstract
The chemical and mechanical properties of the tribofilms have an important effect to friction and wear in boundary lubrication. Previous studies have been carried out to investigate the mechanisms of formation, the chemical composition, and the mechanical properties of the tribofilms on steel and DLC surfaces, but the interactions between these properties are still lacking deeper understanding. In this work, the sliding evolution of the chemical and mechanical properties has been analysed using Attenuated Total Reflection-Fourier Transform Infrared (ATR-FTIR) spectroscopy and Atomic force microscope (AFM). For this purpose, three different kinds of contacts (steel/steel, steel/HDLC and steel/Si-DLC) have been analysed. Also, three oils have been used: two commercial oils containing different amount of SAPS additives (E6 and E7 grade) and a mineral base oil containing ZDDP additive. The ATR-FTIR spectroscopy has been used for the chemical characterization of the tribofimls in boundary conditions at two different testing times, 25 min and 6 hours. In order to analyse the topography, the thickness and the stiffness of the tribofilm, different modes of AFM have been employed, as well as the nano-hardness of the tribofilms has been measured using nanoindentation. The results show that chemical composition, the sliding evolution, and the growth of the tribofilms are very dependent of the surface type and the oil additives.
