Untersuchung der Einflussgrößen auf das Reibverhalten von Kohlenstoffschichten in geschmierten Tribosystemen

One of the most important coating for machine component applications is amorphous carbon, or commonly known as DLC (Diamond-like Carbon). This coating enables in different applications, recently also in automotive drive train, not only reduction of friction losses but also increases the wear resistance of machine components. Nevertheless, the known tribological performance of DLC coatings depends on the environment and medium, under which they are subjected to work. Due to the increasing importance of the DLC coatings especially in drive train, very good tribological performance of DLC coatings under lubricated conditions desired. The modern lubricants are developed for ferrous surfaces but the surface properties of DLC differ from such surfaces. Furthermore, the DLC coatings show chemical inert behavior; therefore, the known interactions between ferrous surfaces and additives cannot be applied for DLC surfaces. This aim of this thesis is to investigate the factors, which influence the tribological performance of the DLC coatings under lubricated condition. For this purpose, different type of DLC coatings was developed in an industrial coating facility. Thereby, the parameters taken into account are the type of the coating process (MSIP or PACVD), type of reactive gas, hydrogen and metal concentration in the DLC coatings. Furthermore, on the lubricant side different parameters such as type of the base oil, viscosity and additives are also considered. Due to the chemical inert behavior of the amorphous carbon coatings, during the investigations the main focus set on the physical interactions, adhesion energy and interfacial tension, between the DLC coatings and the lubricants. The tribological performance of the DLC with lubricants is examined in a Pin-on- Disk Tribometer, in which the lubricant regime lies between boundary and mixed lubrication zone. The influence of physical interactions, hydrogen and metal concentration as well as the reactive gas type during the deposition on the tribological behavior of the coating/ lubricant pairs is determined by regression analyze. Finally, the wear tracks of the chosen DLC/lubricant pairs are investigated with XPS, in order to complete the model, with which the interactions between the DLC and lubricants explained.