High-Temperature Corrosion of Stainless Steels and Ni Alloys During Combustion of Urea–Ammonium Nitrate (UAN) Fuel
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This paper reports on corrosion behavior of different materials under combustion of a nitrogen-based fuel: aqueous solution of ammonium nitrate and urea (UAN). Tested materials include stainless steels 316, 310 and nickel alloys: 600, 601, 617, 800H and RA333. The results were derived under conditions close to those in practical continuous combustion applications. The coupons were positioned in quartz cylinders at temperature 520 ± 10 °C and pressure 10 MPa in the effluent gases. The corrosion of the 316 SS fuel injection tube was tested as a function of the stages that occurred along the tube, namely: heating, ignition, and combustion. Microstructure, chemical composition, depth profile and thickness of the formed oxide scales were studied. High corrosion resistance was found for 310 SS, nickel alloys 601 and RA 333. The heaviest corrosion attack of 316 inlet tube (both general and intergranular) was observed in the area where the exothermic combustion process began.