Performance in oxidizing and carburizing atmospheres

The laboratory investigations include oxidation/corrosion and aim to understand the degradation mechanisms of these materials, in order to assess their performance. As the primary usage of these materials is in the heat exchanger of the innovative CSP-supercritical CO2 power plants, separate investigations for each of the two atmospheres of the heat exchanger (ambient air and CO2) were conducted. Task 4.1 and Task 4.2 focused on investigating the material degradation on the outer side of the heat exchanger tubes (air oxidation) and the internal wall degradation (due to CO2 corrosion). The investigations of oxidation and corrosion resistance were carried out in a test programme shared between FZJ, CIEMAT and CVR. The specimens were tested in air or CO2 (technical or high-purity gas) at elevated temperatures (between 600°C and 900°C). The materials were characterised in thermogravimetry experiments (FZJ), quasi-isothermal oxidation (CIEMAT), and cyclic oxidation (FZJ), with future high pressure autoclave (CVR) tests planned. In order to evaluate the oxide scale growth kinetics and the microstructural changes in the materials induced by oxidation/corrosion, post-exposure characterisation was performed mainly by optical metallography and SEM/EDS analysis of cross-sections of the specimens. The deliverable D 4.1 provides a comprehensive overview of the oxidation and CO2-corrosion testing results.