Creep, Stress Rupture and Stress Relaxation
Besides the usual mechanical design parameters of metallic materials and metal-ceramic composites in energy conversion systems (steam generators, turbines, high temperature fuel cell (SOFC) stacks, heat exchangers, exhaust systems, etc.) their the time-dependent deformation, damage and failure behavior under permanent mechanical load at high temperature is of decisive importance for the reliability of components and systems. In practice not only temperature and mechanical stress play a role. The surrounding atmosphere due to possible superposition of mechanical damage and corrosive attack is of high importance, too. For this reason stress rupture, creep and stress relaxation tests are carried in both air as well as in simulated operation environment (steam, simulated combustion gases such as so-called Oxyfuel atmosphere: 70% CO2 / 29% H2O / 1% O2). Besides the determination of mechanical properties and possible effects of the testing atmosphere on these, the focus is on accompanying microstructural investigation to characterize strengthening-, deformation- and failure mechanisms.
