11158 A Prominent Ni-Cr-Si-Cu Alloy resisting in Metal Dusting

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Product Number: 51300-11158-SG

ISBN: 2011 11158 CP

Author: Yoshitaka Nishiyama, Hirokazu Okada, Takahiro Osuki, Shinnosuke Kurihara and Satoshi Matsumoto

Publication Date: 2011

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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. In addition, Ni-base alloy has excellent phase stability which contributes long term creep strength and toughness. Matching filer metal of the new alloy is under developing and shows good resistance to metal dusting corrosion.

Keywords: metal dusting, carburization, syngas, nickel base alloy, oxide, Cu, dissociative adsorption, long term creep strength, thermal stability, welding