Oxidation behavior, phase stability and temperature-depended friction behavior of transition metal nitride thin films

• Applicant: Professor Dr.-Ing. Wolfgang Tillmann
• Subject Area: Coating and Surface Technology
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 509534873

The overall objective of the proposed research project is a fundamental understanding of the influence of silicon and molybdenum on the oxidation behavior, phase stability and temperature-dependent friction behavior of transition metal nitride thin films. The interaction between the chemical composition, the structure as well as the tribo-mechanical properties will be investigated in order to subsequently analyze the temperature-induced changes on the property profile of the Cr(1-x-y)MoxSiyN and Ti(1-x-y)MoxSiyN coatings. Due to a different thermal stability of the chromium and titanium oxides formed during the oxidation process, a phasetemperature specific property profile can be created. Therefore, both coating systems, the Cr(1-x-y)MoxSiyN coating at the Institute of Materials Technology, TU Dortmund and the Ti(1- x- y)MoxSiyN coating at the Research Center CIDEMAT, University of Antioquia, are synthesized under a systematic variation of the silicon and molybdenum content respectively. Subsequently, the microstructure, in particular the formation of a nanocomposite structure, is investigated as a function of the chemical composition of the coating systems. The aim is to fully understand the element-dependent amorphous/crystalline phase ratio as well as the crystallite structure and size. By using transmission electron microscopy (TEM), the coating systems can be investigated with regard to the formation of a nanocomposite structure, while X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) can be used to determine the crystalline phases and bond structures formed and thus contribute to the complete characterization of the coatings. This in turn enables a correlation between the structural properties and the tribo-mechanical behavior. Based on the results, the influence of temperature on the structure and properties of the coating systems is investigated. By means of post-annealing processes and X-ray near-edge absorption spectroscopy (XANES) a detailed examination of temperatureinitiated recrystallisation and diffusion processes as well as phase transformations is performed. In order to analyze the impact of dynamic effects of a tribological collective in addition to the thermalstructural changes, tribometer investigations are carried out at high temperatures. In particular, the oxides formed are investigated with regard to the formation of friction-reducing Magnèli phases by X-ray diffraction and are associated with the friction and wear properties.

• DFG Programme: Research Grants
• International Connection: Colombia
• Partner Organisation: Universidad de Antioquia
• Cooperation Partner: Professor Dr. Gilberto Bejarano Gaitán