Studies of oxidation resistant tungsten alloys at temperatures of 1100 K to 1475 K

Electricity from nuclear fusion is a promising approach. An accidental scenario of a fusion power plant assumes a loss of coolant and a damaged reactor vessel. In this case temperatures beyond 1200K of the plasma-facing materials are expected. This thesis investigates W-Cr-Y alloys to provide safety after such an accident. It is shown how Cr forms an oxide layer by diffusion that suppresses the release of WO$_{3}$ at temperatures up to 1273K in dry and humid air. Suppression by more than one order of magnitude as compared to W is measured for the first time. Y is issential for suppression of WO$_{3}$ release and is detected for the first time at the oxide grain boundaries and in the form of YCrO$_{3}$ nano-particles. An understanding of the oxidation in dependence on morphology, microstructure, composition and the envronmental conditions is developed using experimental and theoretical studies of the interaction of the involved elements