The dynamics of boundary layer in tribological high-load contacts, such as brakes, is highly complex. It is influenced by various factors, including body surfaces, wear debris, surface pressure, sliding speed, temperature and chemical processes, among others. In many studies, the influence of chemical reactions and reaction products generated during high-load contact is often overlooked. The complex composition of friction pairs, such as brake pads, makes it difficult to accurately analyse the dissipation caused by chemical reactions. The main purpose of this study is to develop a simple and effective method for investigating the influence of tribological processes on the boundary layer dynamics. To achieve this purpose, sample preparation and chemical analysis procedures were investigated. Minimal mixtures of two or three components were used, with epoxy resin as binder and three different abrasives. The sample preparation process was modified by developing a fixture for the curing process, which significantly improved the homogeneity of the samples. Tribological experiments were carried out using a pin-on-disc tribometer and continuously measuring the temperature and coefficient of friction. In addition, the surface was monitored in-situ with topographic surveys. At first three different chemically inert samples were created and investigated. In following experiments, copper powder was added to each mixture to investigate the influence of possible reactions. Larger patches were identified on individual samples and became the center of attention during chemical and optical analysis. Topography images were taken with a high-resolution digital microscope to identify patches or areas of interest. Laser microscopy was used to measure the height and size of the respective patches. For chemical elemental analysis, we used different methods such as EDX, WDX, and XRF. In addition, the hardness of the various patches was measured using a microhardness measurement method. The results show that chemical reactions such as oxidation can have an influence on the complex boundary layer dynamics in tribological high-load contacts. These findings can help in the development of more efficient and sustainable tribological systems.
Mrs. Christina Lehmann, Research Associate, TU Braunschweig; Prof. Dr. Günter Bräuer, Professor and Head of Institute, Technische Universität Braunschweig, Institute for Surface Technology; Mr. Chengyuan Fang, Research Associate, Technische Universität Braunschweig, Institute for Particle Technology; Prof. Dr.-Ing. Georg-Peter Ostermeyer, Professor, Technische Universität Braunschweig, Mechanical Engineering; Prof. Dr.-Ing. Carsten Schilde, Head of Division, Technische Universität Braunschweig, Institute for Particle Technology