Corrosion of alumina-forming austenitic steel Fe–20Ni–14Cr–3Al–0.6Nb–0.1Ti in supercritical water

Early oxidation of Super304H stainless steel and its scales stability in supercritical water environments

“…5, which indicates that the inner layer consisted primarily of chromiumrich spinels, while magnetite phases were main components of the outer layer. The absence of hematite phase can be explained by higher temperatures [7], lower oxygen content less than 2 ppm [22], and/or insufficient exposure times for second oxidation of the magnetite [6,11,23]. The occurrence of wustite (FeO) phases was not detected, even when the testing temperature was as high as 580 C. This phenomenon can be attributed to solid reaction between FeO and Cr 2 O 3 .…”

“…Meanwhile, the inward transport of oxygen in forms of O 2À , H 2 O, and/or O 2 also are accelerated with an increase in temperatures [5,25], which is in favor of the growth of the inner layer. However, worth mentioned is that the growth of inner layer may be by means of the direct penetration of gas molecules through defects in the scales, such as cracks or crevices [23]. As can be seen in Fig.…”

High-Temperature Oxidation Resistance of Alumina-Forming Austenitic Stainless Steels Optimized by Refractory Metal Alloying

“…For solid solution alloys, the occupation of atoms is decided by the interaction between solute atoms and solvent atoms, which can be evaluated by the mixing enthalpy ∆H in binary systems. The general procedure to determine the ideal structural unit of a solid solution alloy is as follows: (1). Classify the solute atoms according to their mixing enthalpy ∆H with solvent atoms, so that their occupations (as center, shell or glue atoms) are preliminarily determined.…”

“…After the 200 h aging, a bulky σ phase is formed as identified according to reference [11], showing a brightness between B2 phase and Laves phase and lengths up to 4 µm at the grain boundaries. By examining Figure 4 (1)(2)(3)(4) all fall into the pure austenite region. These results confirm the sufficient austenite stability of the series-2 alloys satisfying the cluster formula.…”

“…Alumina-forming austenitic (AFA) stainless steel is a type of heat-resistant stainless steel which can form a dense and stable aluminum oxide layer to protect it from hightemperature environments. Compared to Cr 2 O 3 film, which is formed in traditional austenitic stainless steels, Al 2 O 3 film has a lower growth rate (1-2 orders of magnitude slower), better thermal stability, and is more stable in water vapor, even in combustion and chemical reactions with carbon and sulfur [1][2][3]. Since the 1970s, Al with weight percentages of 4-5 has been added to austenitic stainless steel in order to improve its high-temperature oxidation resistance [4][5][6][7][8][9].…”