Abstract:The influence of preoxidation of Fe-25Cr-5Al and Fe-25Cr-10Al alloys on their subsequent sulfidation has been studied by a thermogravimetrical method. The oxidation-sulfidation procedure was decided according to the acoustic emission measurement results of the oxidizing-cooling processes. The transformation from oxidation to sulfidation at higk temperatures was achieved.As a result, the outstanding cracking of the oxide scale was avoided. It is found that a complete alumina scale can impede effectively the occurrence and the development of sulfidation. Its protection, however, has a concern with the alloy composition. The microdefects of oxide scale are the places where sulfide nodules appeared and grew. They are also the main factors to decide whether the preformed oxide scale be still protective.

Key words: Fe-25Cr-5Al Fe-25Cr-10Al preoxidation sulfidation