ABSTRACT

Power generation from coal using Advanced-Ultra Supercritical (A-USC) steam conditions will result in further improvement of fuel efficiency and decreased greenhouse gas emissions. The steamside oxidation resistance of the candidate alloys for an A-USC application is an important consideration in selecting an alloy for superheater and reheater tubing, the header and transfer piping. The concern is that steamside oxidation could potentially lead to wall loss compromising structural integrity as well as act as an insulating barrier to heat transfer. Moreover, loose scales can also lead to clogging of the tubes. This paper will review selected papers dealing with steam oxidation of the candidate nickel-base alloys and compare results of ongoing research for exposure conditions ranging from moist air at atmospheric pressure (650°C to 800°C) to steam at 34.5 MPa (650°C to 760°C) . The role of the various alloying elements of these alloys in steam oxidation will also be discussed. The primary corrosion mechanisms are parabolic scale growth, internal oxidation and reactive evaporation of chromia.

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