Project 6: Evolution of Mechanical Properties of Coating Systems during Exposure at High Temperature
Supervisors: Prof. Matthias Oechsner, Prof. Matthias Galetz
The development of novel thermal barrier coating systems, which is the primary purpose of the Research Training Group MatCom – ComMat, highly depends on the understanding of material properties and the description of potentially occurring damage mechanisms, in addition to other important aspects of investigation. In order to ensure safe operation of components in applications under extremely high temperatures and in aggressive media, both the characterization of systeminternal interactions between the individual layer components and the description of the material system behavior under said environmental conditions are of essential importance.
The sixth project of the Research Training Group can be basically divided into three work packages. The results of these subprojects are to contribute to a description of diffusion-related damage influences, the development of reliable oxidation protection coatings and the elaboration of a fracture mechanical evaluation concept for the coating systems. The methods developed for this purpose in current and already completed research projects can be transferred and extended to the novel thermal barrier coating systems, so that in addition to the characterization of the material systems, the further development and improvement of the simulation and evaluation approaches is also aimed at within the scope of the Research Training Group.
A central component of the first work package is the modeling and simulation of the interdiffusion behavior of the layer components. In terms of design and optimization of the thermal barrier coating systems to be developed, the investigation and recording of influential factors on damaging mechanisms of this type plays an important role. Depending on thermally induced microstructural transformation processes, the thermophysical and mechanical properties of the composite systems must be characterized to the best possible approximation on the basis of selected concepts and material data.
The core of the second work package is the design and subsequent optimization of suitable environmental barrier coatings (EBC). By integrating these specially developed protective coatings into the material composite, a significantly increased resistance of the material system to strongly oxidizing environments can be achieved. In order to minimize damage caused by the environmental attack as far as possible, it is necessary to adapt the protective effect of EBCs to the coating system by means of relevant parameters such as the distribution of alloying elements, Young's modulus, microstructure and coating adhesion.
The objective of the third and final phase of the project is to develop and validate an evaluation model based on fracture mechanical concepts. Taking into account and extending promising methods from previously funded research projects, the approach to be developed should be able to quantify life-limiting mechanisms in the material systems under high-temperature loading. An important aspect with regard to the development of this evaluation model is the consideration of complex microstructures and the interaction between different types of microdefects.