Long-term tests were conducted for several Fe- and Ni-base alloys to evaluate the metal dusting behavior. Test specimens with ground surfaces were reacted with a CO-H2-CO2-H2O gas mixture which simulates synthetic gases produced in reforming plants. Several pits have developed on the ground specimens of conventional Ni-base alloys after exceeding 10,000h when the heating at 650°C for 50h was periodically followed by cooling. A Ni-base alloy containing a proper content of Cu still had no pits on its surface even after an exposure of 17,000h. The cyclic heating test has also been conducted for test specimens treated by electrolytic-polishing to accelerate the pit initiation. It was demonstrated that the developed alloy had an excellent resistance against metal dusting while other Ni-base alloys had several pits in a relatively short time. A solid solution of Cu greatly restrains an interaction between the CO molecule and the metal where oxide scales were damaged, leading to a complete healing of the protective oxide scale.

Subject
Pits, Metal surfaces, Nickel based alloys, Oxide formation, Metallography, Copper alloys, Syngas, Oxide scales, Oxide surfaces, Metals, Scale formation, Metal dusting, Alloys
Keywords:
metal dusting, carburization, syngas, nickel base alloy, oxide, Cu, dissociative adsorption
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2009
Association for Materials Protection and Performance (AMPP)
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