Project Details
Projekt
Chemical composition of the boundary layer
Applicant
Dr.-Ing. Marcus Hans
Subject Area
Synthesis and Properties of Functional Materials
Term
since 2026
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 556252784
Reaction layers on the friction surfaces of rolling bearings have a decisive influence on their running behavior and are therefore of enormous importance for wear minimization. While the chemical composition of reaction layers is significantly relevant concerning layer formation and effect, it is not yet understood. In particular, the characterization of reaction layers is challenging due to their small thicknesses. The goal of subproject (TP) 7 within the research group is to understand the chemical composition of the outer boundary layer, consisting of reaction, adsorption, and oxide layers, as well as to identify viable reaction layers. The three-dimensional analysis of the chemical composition using atom probe tomography at the nanometer scale allows for mapping relevant physical and chemical processes and thus contributes to cross-scale modeling of layer formation. Using the rolling bearing material 100Cr6 in contact with a zinc dialkyl dithiophosphate/polyalphaolefine (ZDDP/PAO) lubricant mixture, the following central scientific questions are investigated: - How do material and contact parameters influence the chemical composition of the reaction layer in real contact? - What impact does parameter reduction at laboratory scale have on the comparability of synthetic reaction layers with real contact conditions? - How does the bonding of the reaction layer to the oxide layer occur? - Which characteristics of the chemical composition indicate wear-protective reaction layers? In real contact, the local composition of samples from tribometer tests is examined depending on contact parameters (rolling and sliding speed, local pressures and temperatures, contact and rest times). In model contact, both the influence of shear through cyclic loading under pressure and shear as well as mechanical loading from individual roughness peaks on nanoscale composition are evaluated. Synthetic model layers are produced via physical vapor deposition and serve for comparison with tribometer tests. Understanding the chemical composition of the outer boundary layer in model contact enables evaluation of the chosen reduction hypothesis through comparison with real contact. Additionally, synthetic adsorption layers will also be quantified, which will be transported exclusively via vacuum suitcases to avoid atmospheric exposure. TP7 bridges between levels of consideration: real contact (TP1, TP4), model contact (TP4, TP5, TP6), as well as atomic level (TP2, TP3) and contributes to continuity in knowledge transfer. Close experimental collaboration will particularly take place with TP3, TP4, TP5, and TP6, while TP1 and TP2 will utilize results from TP7 regarding creating boundary layer models and validating simulations.
DFG Programme
Research Units
