The effect of sulphur on the carburization of three Fe-19Ni-13Cr alloys with various Al additions at 900 °C in oxygen-contaminated CH4-H2-H2S atmospheres

The sulphur effect on the carburization of three Fe-19Ni-13Cr alloys with various Al additions was studied at 900 °C in four CH4-H2-H2S gases providing sulphur pressures from 0 to 4.8 × 10−11 atm. The corrosion rates, decreasing with increasing sulphur pressure, were slower for Fe-19Ni-13Cr-6Al than for the other alloys under each gas mixture. The carburization of Fe-19Ni-13Cr-6Al was blocked in the two H2S-richer gas mixtures by the growth of external alumina scales. The carbon attack was also prevented on Fe-19Ni-13Cr and Fe-19Ni-13Cr-2Al in the gas richest in H2S by the formation of thin continuous CrS scales.