Browsing by Author "Fox, BJ"

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    Oxidation of 2¼% Cr, 1% Mo steel in carbon dioxide.
    (Australian Atomic Energy Commission, 1962-09) Draycott, A; Fox, BJ
    Alloy steels were studied to find types suitable for nuclear use in carbon dioxide-cooled reactors at temperatures in the range 400 — 600ºC. The corrosion of 2¼% Cr, 1% Mo steel in carbon dioxide was measured in the temperature range 460º to 525ºC and the gas pressure range 0 to 225 ps.i.g. The effect of gas velocity, specimen surface treatment, and water content of the gas were also determined. Adherent oxide scales of the Fe304 — Fe203 type were formed under semi—static conditions together with an unidentified spinel. A Cr203 film was never formed under any conditions. Weight gain depended mainly on temperature and varied little with gas pressure, surface treatment, or water content of the gas. The relationship between weight gain and time varied between parabolic and cubic with weight gains ranging from 1.7 mg/cm2 to 5.7 mg/cm2 after 1000 hours exposure within the temperature range investigated. Estimated penetration depths after 10,000 hours ranged from 6.8 x 10—4 to 18.5 x 10—4 inches. In high velocity gas, that is, at 150 ft/sec, weight gains varied from 0.7 mg/cm2 at 460ºC to 2.0 mg/cm2 at 525ºC after 100 hours. No scaling occurred during any experiment not involving thermal cycling but this may have been due to the short duration of the tests. The relative thickness of the outer Fe203 layer in the scales examined was much greater under flowing gas than under semi—static conditions. It appears that the limiting temperature for 2¼% Cr, 1% Mo steel in carbon dioxide—cooled reactors is 490ºC; above this temperature excessive scale formation occurs which, on flaking, could seriously contaminate any gas circuit.