Studies concerned with the metal dusting of Fe-Cr-Ni materials

This paper presents results form a series of experiments carried out in a H -2-based gas mixture containing 24.4% CO and 2.4% H2O. Discontinuous tests have been carried out at 560 degrees C for periods of up to 200 h. This gas mixture has a carbon activity well above 1, placing it in a regime where t he gas is considered to be supersaturated with carbon. As a result, carbon is precipitated from the gas phase and deposited onto metallic surfaces as graphite. In this way, these experiments simulate conditions found in petro chemical plants that have been shown to lead to a form of catastrophic atta ck, known as metal dusting. Several commercial candidate reformer tube materials have been exposed to t he gas mixture at nominally 1.5 bar (absolute) in order to establish their relative performance under these conditions. An additional material, a 12% Cr ferritic steel containing 2.75% Si has been exposed at the same time sin ce the presence of silicon is known to improve carburisation resistance and its influence on metal dusting has not been fully evaluated. Surface condi tion may also play a role and this has also been taken into consideration d uring this study. Cross-sectional microstructural analyses are presented showing the nature a nd extent of attack and the underlying mechanisms responsible for this form of degradation are discussed in relation to the variables covered by this study.