The carbnrization behavior of nine commercial nickel-base alloys and four iron-nickel chromium alloys was investigated at 650°C in a carbonizing H2-CO-H2O - gas with a carbon activity of ac >> 1. The iron-nickel-chromium alloys aotlered severe metal dusting after a very short test period. Nickel base alloys were generally less susceptible to metal dusting than iron-base alloys. However, their corrosion behavior was found to depend sensitively on the chromium concentration of the respective alloys. Alloys like alloy 600H, with a chromium concentration of only 16 %, anilered wastage rates which were similar to those of the more resistant iron-base alloys. Nickel-base alloys with chromium concentrations of 25% and above, on the other hand, showed no significant evidence of metal dusting even after 10000 hours of exposure. lt was found that these alloys are protected against metal dualing by tie formation of a dense, self-healing chromia scale, which prevents the penetration of carbon into the base metal.
Keywords: nickel-base alloys, iron-nickel-chromium aloys, carburization, metal dusting, chromia scales