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Oxidation behaviour of silicon-free tungsten alloys for use as the first wall material

The use of self-passivating tungsten alloys as armour material of the first wall of a fusion power reactor may be advantageous concerning safety issues. In earlier studies good performance of the system W−Cr−Si was demonstrated. Thin films of such alloys showed a strongly reduced oxidation rate compared to pure tungsten. However, the formation of brittle tungsten silicides may be disadvantageous for the powder metallurgical production of bulk W−Cr−Si alloys if a good workability is needed. This paper shows the results of screening tests to identify suitable silicon-free alloys with distinguished self-passivation and a potentially good workability. Of all the tested systems W−Cr−Ti alloys showed the most promising results. The oxidation rate was even lower than the one of W−Cr−Si alloys, the reduction factor was about four orders of magnitude compared to pure tungsten. This performance could be conserved even if the content of alloying elements was reduced.