Influence of chromium content on carburization of chromium-nickel-iron alloys in carbon dioxide

Abstract

The use of carbon dioxide or other gases that contain carbon dioxide as nuclear reactor coolants presents certain compatibility problems in the reactor system. One of the more important of these concerns reactions of the gas with stainless steel fuel element cladding that may introduce carbon into the steel. This paper presents the results of an investigation of the carburization of Fe-9 % Ni, varying Cr alloys in pure carbon dioxide at 600 to 800° C. It is shown that the rate of carburization increases as the chromium content increases from 7 to 11 % Or and decreases sharply on further increase in chromium content to about 20 % Cr. The mechanism causing carburization in these alloys depends on the composition and nature of the oxide film. The existence of large amounts of Cr 2O 3 in the film reduces the tendency for carburization in the higher chromium content alloys.