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.
Keywords: metal dusting, carburization, syngas, nickel base alloy, oxide, Cu, dissociative
adsorption