Alloys are often found to suffer much greater metal-dusting attack under high-pressure conditions compared to ambient-pressure conditions. Ultimately, the resistance of a given alloy to metal dusting depends on the formation of an oxide scale that is impermeable to carbon which, in turn, depends on scale composition and structure. This paper reports the metal-dusting behavior of several Ni-based alloys having relatively high Cr contents (about 30 wt.%) and different controlled minor levels of Fe, Al, and/or Si. Testing was conducted under 20 bar total pressure of a high-carbon-activity gas at 600 °C (1112 °F). The exposed alloys were analyzed by SEM and TEM techniques to evaluate the oxide scales and evidence of carbon ingress. It was found that aluminum is beneficial to improve metal dusting resistance by reacting to form a continuous inner layer of alumina; whereas iron is detrimental to resistance. Mechanistic aspects of the role(s) played by minor elements in affecting metal-dusting resistance are considered.

Subject
Pits, Nickel based alloys, Chromia, Graphite, Commercial alloys, Oxide scales, Metals, Scale formation, Scale, Metal dusting, Carbon, Aluminum alloys, Alloys
Keywords:
Metal dusting, Ni-base alloys, Alloying elements, High-pressure testing, Chromia-scale, Alumina-scale
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2020
Association for Materials Protection and Performance (AMPP)
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