HIGH-TEMPERATURE SULFIDATION-OXIDATION OF STAINLESS-STEELS

The alloys 153MA, 253MA and 353MA,Type310S stainless steel, Type 309S stainless steel and IN601 were all exposed at 900-degrees-C to a compl ex gas mixture of CO/CO2/SO2/N2, corresponding to a sulfur partial pre ssure of 1.3 x 10(-3) atm and oxygen partial pressure of 3.2 x 10(-14) atm. The corrosion kinetics were parabolic in all cases. The rate for IN601 was unacceptably high due to extensive liquid sulfide formation . The other materials all formed solid external scales as well as unde rgoing some internal corrosion. The rates for all three MA alloys were less than those of the two conventional stainless steels. The corrosi on behaviour of all the materials was dominated by sulfide formation a s only relatively small amounts of oxides were formed. The same materi als were exposed at 800-degrees-C to a gas mixture corresponding to a sulfur partial pressure of 1.7 X 10(-3) atm and an oxygen partial pres sure of 4.9 x 10(-16) atm. No liquids were formed, and the corrosion p roducts consisted of an outer scale layer of (Fe, Ni)1-xS, and an inne r layer containing mixtures of sulfides and oxides. Reaction kinetics were again parabolic. The rates were rather similar, with IN601 reacti ng fastest, and 353MA slowest.