Adsorption is one of the main mechanisms of interactions between additive molecules and surfaces in boundary lubrication, whereby adsorbed molecules form thin protective layer, which provides decrease in friction and protects surfaces from wear. The main component of the DLC coatings as well as the majority of the organic additives is carbon, which makes the analysis of the thin layer adsorption to the DLC coatings extremely difficult. Main difficulties when using conventional methods (XPS, FT-IR spectroscopy, optical ellipsometry, SIMS and SEM) for such analyses are that carbon absorbs large amount of IR, visible and UV spectra and presents the dominant signal. In addition, above mentioned methods require cleaning of surfaces and/or work in UHV and are difficult to be used for direct (»in-situ«) measurements. Recent investigations showed that neutron reflectometry is convenient method for analysis of such adsorbed layers on DLC coatings. Namely, it has been successfully applied to determine the thickness and density of adsorbed layers of organic molecules on the DLC under stationary conditions, but it can also be used to study the adsorption directly in tribological contact. This paper presents the application of neutron reflectometry for analysis of the adsorbed layer on the DLC-coating.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 15107099In recent years, DLC coatings are becoming extensively used in automotive applications for internal combustion engines, where ZDDP is the key additive. In spite of research work so far the mechanism of formation, and structure of the ZDDP derived tribofilm on DLC, the understanding is still very limited. Accordingly, in this work, the chemical structure of the ZDDP thermal film during static thermal tests at 150°, i.e. without any tribological action, on Si-DLC and H-DLC, as well as steel as reference, at different times and ZDDP concentrations have been investigated. The ATR-FTIR and XPS spectroscopies have been used for the chemical characterization of these thermal films. The results have indicated that the chemical structure of ZDDP thermal films on the steel surface is different form the DLCs, while different times and ZDDP concentrations do not affect the chemical structure of the ZDDP thermal film on each individual surface/substrate. In addition, the results have indicated that the thickness of the thermal film is greater on the steel than on the DLC and is linear with the concentration, which indicates the uniformity of the chemical structure of the films.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 15106075In this study we present a successful combination of DLC coatings and steel lubricated by WS2, MoS2 and graphene nanoparticles. To clarify the mechanisms of this physically-based lubrication technology, we have investigated, on individual contacts, how different surface roughness, running-in, lubrication regime and concentration influence the lubrication performance of the nanoparticles mixed with PAO oil. The performance of the DLC/DLC contacts is directly compared to steel/steel contacts. The friction is always significantly reduced when nanoparticles are used, irrespective of the type of nanoparticles, and material in contact. However, the performance of different nanoparticles varies between different materials and lubrication regimes.
B.04 Guest lecture
COBISS.SI-ID: 14636827