Showing papers by "Arnold R. Marder published in 2009"
TL;DR: The results from electron microprobe analysis (EMPA) and scanning transmission electron microscopy (STEM) analyses of select as-corroded coupons from the long tem tests are discussed in this article.
Abstract: The first part of this manuscript presented SEM analysis of corrosion products formed on iron-aluminum-chromium alloys that were exposed to a simulated low NO x combustion environments. In Part II, results from electron microprobe analysis (EMPA) and scanning transmission electron microscopy (STEM) analyses of select as-corroded coupons from the long tem tests are discussed. Despite the formation of thick iron sulfide films one of the alloys, EMPA did not detect any measurable depletion of aluminum near the surface of this alloy. STEM analysis revealed that chromium was able to form chromium sulfides only on the higher aluminum content alloys, thereby preventing the formation of deleterious iron sulfides and reducing the overall corrosive attack on this alloy. Also observed in the STEM analysis was the encapsulation of external iron sulfide products with a thin layer of aluminum oxide, which may serve as a secondary layer of corrosion protection in these regions.
6 citations
TL;DR: In this paper, three iron aluminum alloys were exposed to simulated coal combustion environments at 500 and 700 °C for short (100 h) and long (5000 h) isothermal durations.
Abstract: Due to their excellent corrosion resistance, iron aluminum alloys are currently being considered for use as weld claddings in fossil fuel fired power plants. The susceptibility to hydrogen cracking of these alloys at higher aluminum concentrations has led researchers to examine the effect of chromium additions on the corrosion resistance of lower aluminum alloys. In this work, three iron aluminum alloys were exposed to simulated coal combustion environments at 500 and 700 °C for short (100 h) and long (5000 h) isothermal durations. Scanning electron microscopy was used to analyze the corrosion products. All alloys exhibited excellent corrosion resistance during short term exposures. For longer test times, increasing the aluminum concentration improved alloy corrosion resistance. The addition of chromium to the binary iron aluminum alloy prevented the formation iron sulfide and resulted in slower corrosion kinetics. A general classification of the scales developed on these alloys is presented.
1 citations