Abstract
The focus of this review is the state of knowledge of the oxidation behavior in steam of alloys with potential for use as pressure parts in steam boilers. Growth of steam-side oxides has implications for scale exfoliation, tube blockage and overheating, and turbine erosion. Mitigation of such problems requires mechanistic understanding of the influences of alloy composition and microstructure as well as time, temperature, and boiler operating parameters on the evolution of specific scale structures. The oxidation behavior in steam of three classes of alloys is addressed: ferritic steels (particularly the 9-12 wt% Cr alloys), austenitic steels, and high-temperature nickel-based alloys. Understanding the interplay among compositional and microstructural requirements for strengthening and oxidation resistance, and their influence on the rate and mode of scale evolution is key to the most effective application of these alloy classes. Underlying these interests is the apparently different mode of oxide growth in steam than in air, especially contributions from inward transport of oxidant species. The particular species involved and their roles in the oxidation process are expected to exert a large influence on the oxide morphologies developed, while the fate of any hydrogen released in the alloy is a further topic of particular interest.