What are high-temperature materials?
High-temperature materials are materials that can be used reliably even under extreme thermal and mechanical conditions. They are used wherever components are exposed to high temperatures, thermal cycling, mechanical loads, oxidation, corrosion, or wear. Typical fields of application include, for example, energy and power transmission technology, mechanical and plant engineering, and other high-performance industrial applications. It is crucial that these materials retain their strength, microstructural stability, and functionality even over extended periods of use.
The focus is on the interplay between chemical composition, microstructure, manufacturing process, and operating conditions. High-temperature-resistant materials must resist creep deformation, thermal fatigue, oxidation, and damaging microstructural changes for as long as possible. At the Chair of Materials Science and Testing, we investigate how microstructures, phases, precipitates, and defects change under high temperatures and what impact these changes have on mechanical and functional properties. The goal is to better understand materials and process routes, evaluate them systematically, and further develop them for demanding applications.
Research at the Department
Understanding microstructures, evaluating high-temperature properties, and further developing materials for extreme operating conditions
At the Chair of Materials Science and Testing, we view high-temperature materials as the interplay of chemical composition, manufacturing process, microstructure, and thermomechanical stress. The focus is on how microstructures, phases, precipitates, and defects change at high temperatures and how these changes influence mechanical and functional properties.
To this end, we combine materials testing methods with metallographic and microscopic characterization. This allows us to systematically investigate the relationships between material condition, temperature resistance, damage behavior, and component reliability. Particular emphasis is placed on evaluating microstructural stability, oxidation and corrosion behavior, and mechanical performance under demanding operating conditions.
Methods and Skills
From cyclic testing to fracture surface analysis
Evaluation of strength, hardness, and deformation behavior under conditions similar to those encountered in actual use. This allows for a precise assessment of the material's condition and load-bearing capacity.
Investigation of resistance to oxidizing and corrosive environments. The key factor is how protective layers form and change under thermal stress.
Analysis of crack formation, microstructural changes, and local damage mechanisms. This allows for a better understanding of the causes of property degradation and component failure.
Analysis of microstructure, grain boundaries, precipitates, oxide layers, and defects. This allows for a targeted evaluation of structural changes at high temperatures.
Investigation of temperature-dependent phases, precipitates, and transformation processes. The focus is on their influence on microstructural stability and material properties.
Evaluation of the influence of temperature-time profiles on microstructure, hardness, and durability. The goal is to gain a better understanding of thermally induced changes.
Projects in this subject area
Overview of Research Projects in the Field of Innovative High-Temperature Materials
Refractory metal-based multicomponent alloys (RHEAs) are considered promising candidates for high-temperature applications. RHEAs consist of five or more elements in nearly equiatomic concentrations. The Ta-Mo-Cr-Ti-Al alloy has a multiphase microstructure consisting of an ordered B2 matrix and an intermetallic Laves phase. The project aims to develop alloys in the Ta-Mo-Cr-Ti-Al system with an A2 matrix and high volume fractions of ordered B2 precipitates in order to achieve a balance of properties with respect to ductility at room temperature, creep resistance at elevated temperatures, and oxidation resistance. To achieve these goals, alloying strategies are planned that aim to suppress the formation of brittle intermetallic phases while simultaneously increasing the intrinsic ductility of the matrix. The alloy development is based on thermodynamic calculations as well as experimental analytical methods.
To further increase the efficiency of gas turbines in the future, new high-temperature materials with improved temperature resistance and lower specific weight are needed. Mo-Si-B alloys, which possess good mechanical properties at high temperatures, offer great potential for these applications. It is clear that SiO₂-forming protective layers are needed for long-term operation. When these materials are used in the high-velocity combustion atmosphere of gas turbines, SiO₂ must be protected against water vapor corrosion by means of environmental barrier coatings (EBCs), which requires the application of an appropriate ceramic EBC overlay. Furthermore, the oxidation behavior of the substrate material or its pretreatment must be improved to the extent that spalling of the oxidation-resistant layer does not lead to total failure of the component. The overarching goal of this project is therefore the development of a technically viable Mo-Si-B-Ti alloy, together with a coating system (Figure), that provides lasting protection over a wide temperature range in both dry and humid atmospheres.
High-temperature materials are essential in the development of aircraft gas turbines. The selected materials must withstand high mechanical and corrosive stresses at temperatures exceeding 1,000°C. Due to increasing demands, alloys based on refractory metals are attracting more and more attention. The element vanadium could offer a lucrative and interesting alternative to the materials used to date. The goal of this project is to gain a comprehensive understanding of the vanadium-silicon-boron system. This includes phase formation and transformation during solidification, as well as phase stability and transformations at equilibrium. To this end, a thermodynamic database has been created, which is continuously optimized and adapted in conjunction with the results obtained from the various alloys.
Contact
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