THE CORROSION OF AISI-310 STAINLESS-STEEL EXPOSED TO SULFIDIZING OXIDIZING CARBURIZING ATMOSPHERES AT 600-DEGREES-C

AISI 310 is one of the iron-based austenitic steels most commonly used for high temperature components in industrial engineering plants. The alloy, containing 25% Cr and 20% Ni, relies upon the formation and ma intenance of a thin adherent surface chromia layer for protection agai nst severe corrosive attack. The alloy's performance in purely oxidizi ng environments is well established but its behaviour in multi-compone nt atmospheres, particularly those containing sulphidizing species, is less well documented. In the gasification of coal for the subsequent production of electricity using steam or gas turbines, component corro sion can pose significant problems. The work described in this paper w as carried out at 600-degrees-C in H-2-based gas mixtures with constan t oxygen partial pressure (pO2 = 10(-26) bar) and carbon activity (a(c ) = 0.2), but with different levels of sulphur. Sulphur partial pressu res, typical of those found in coal gasifiers (pS2 = 10(-11) to 10(-9) bar), were achieved by making H2S additions of 0.4-1.0%. Corrosion be haviour for exposures up to 1000 b was investigated using weight chang es and a range of electron-optical structural analysis techniques. The influence of sulphur partial pressure on scaling kinetics is quantifi ed and scaling mechanisms are identified.