Type 304 Stainless Steel vs Flowing CO2 At Atmospheric Pressure and 1100-1800F

Abstract

Oxidation characteristics of Type 304 stainless steel in CO2 were observed over the temperature range 1100–1800 F (593–982 C). Although in general oxidation rate curves were parabolic, several periods were observed in which they were approximately linear. These breaks were reproducible and thought to be associated with changes in rate-controlling step of the oxidation process. Carburization of Type 304 stainless steel during exposure to CO2 was observed. Several other alloys were studied, to determine earbiorization mechanism. These included Type 406 stainless steel, a British 20 Cr– 25 Ni, niobium-stabilized steel, Inconel, iron, Fe–1 Cr, Fe–3 Cr, and Fe–10 Cr. Correlation was found between carburization and chromium content, with low chromium favoring and higher chromium inhibiting this reaction. Mechanism was proposed based upon influence of chromium on type of surface oxide formed.

Carburisation of ferritic Fe–Cr alloys by low carbon activity gases

“…Fujii and Meussner [5] reported simultaneous oxidation and carburisation of Fe-Cr alloys containing 1-15 wt.% Cr in pure CO 2 at temperatures of 700, 900 and 1100°C. All alloys remained ferritic at 700°C and produced (Fe,Cr) carbides, the nature of which varied with alloy chromium content from (Fe,Cr) 3 C to (Fe,Cr) 7 C 3 and (Fe,Cr) 23 C 6 , in accordance with the Fe-Cr-C phase diagram. Carbon-containing austenite was formed at the higher temperatures and produced ferrite plus pearlite, martensite and/or (Fe,Cr) carbides upon cooling to room temperature, according to the alloy chromium content.…”

“…Internal carbides were observed after exposure of 9Cr (P92) and 12Cr (X20 and VM12) steels to Ar-50%CO 2 at 550°C [1], and after exposure of model Fe-Cr alloys to Ar-30%CO 2 at 650°C [2]. Reaction of pure CO 2 with an 18Cr (304) steel at 704, 816 and 927°C [3] and with an Fe-15Cr alloy at 900°C [4] also led to internal carbide precipitation. Fujii and Meussner [5] reported simultaneous oxidation and carburisation of Fe-Cr alloys containing 1-15 wt.% Cr in pure CO 2 at temperatures of 700, 900 and 1100°C.…”

“…McCoy [3] suggested that oxide formation from direct reaction of iron with CO 2 could generate CO, FeðsÞ þ CO 2 ðgÞ ¼ FeOðsÞ þ COðgÞ ð1Þ…”

Mechanism of sulphur transport through preformed oxide scales

“…Gilewicz-Wolter (8) has also shown that during the oxidation of iron in SOz atmospheres transport of sulphur takes place via preferred paths at low sulphur dioxide partial-pressure, whereas at one atmosphere fissures are produced at the corners of the specimens through which sulphur from the atmosphere penetrates the scale. McCoy (9) proposed that the carburization of chromium steels in flowing C 0 2 atmospheres at high temperatures may be due to the accumulation of COz molecules in pores present in the outer oxide layer. Birks ( 1 0) proposes that the metal ions and electrons diffusing outwards t o the scale-gas interface produce metal oxide and carbon monoxide which then diffuses inward down microcracks to the porous region of the scale where the CO/CO2 redox system is established.…”

Oxidation behaviour of ferritic stainless steel grade Crofer 22 APU at 700 °C in flowing Ar−75%CO2−12%H2O

“…Future power plants are theoretical to work in the range of 700 °C. The technologies with CO 2 environment require increasing efficiencies which cause higher working temperatures, pressure and customized gas compositions [5]. As that reason, better understanding of the corrosion behaviour of the materials react with CO 2 and H 2 O has to be obtained.…”