SELECTIVE SULFIDATION OF FE-CR ALLOYS

Using Fe-57 Mossbauer spectroscopy, the influence of sulphidation on t he metallic phase in a series of Fe100-xCrx alloys (x less-than-or-equ al-to 45.5) is studied. For samples treated at 1073 K for 1.5 h in an H-2-H2S atmosphere, the partial pressure of sulphur being 10(-3) Pa, t he sulphidation turned out to be selective. For x less-than-or-equal-t o 4.3 at.% the metallic phase became enriched in chromium, while for x > 4.3 at.% it became enriched in iron, indicating that at this critic al composition there is a change in the sulphidation preference.