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Breakaway corrosion in mixed-gas environments

Conference ·
OSTI ID:5752270
Incoloy 800 was preoxidized for approx. 165 h in a low-oxygen environment (p/sub O/sub 2// = 9 x 10/sup -18/ atm) at 875/sup 0/C. subsequently, the specimens were exposed for approx. 165 h to either H/sub 2/-H/sub 2/S or CO-CO/sub 2/-CH/sub 4/-H/sub 2/-H/sub 2/S gas mixtures with a wide range of oxygen and sulfur partial pressures. Results show that in atmospheres with p/Sub S/sub 2// values below that required for base-metal sulfidation and above-threshold p/sub O/sub 2// values, negligible adsorption of sulfur by the Cr-rich oxide scale is noted. Any transport of sulfur across the oxide scale leads to the formation of Cr sulfide particles at grain-boundary locations. Under these conditions, the alloy can weaken owing to grain-boundary embrittlement but the sulfidation wastage will be small. The same conclusions can apply even if the atmosphere has a p/sub S/sub 2// value above that required for base-metal sulfidation and an above-threshold p/sub O/sub 2// value. As p/sub O/sub 2// decreases below the threshold value, significant adsorption of sulfur by the scale and establishment of sulfur channels occur; these processes aid in the transport of Fe and Ni to the gas/scale interface for reaction to form fast-growing sulfides, which lead to breakaway corrosion.
Research Organization:
Argonne National Lab., IL (USA)
DOE Contract Number:
W-31109-ENG-38
OSTI ID:
5752270
Report Number(s):
CONF-831086-2; ON: DE83014704
Country of Publication:
United States
Language:
English