Field Test Results of Newly Developed Austenitic Steels in the Eddystone Unit No.1 Boiler

Six new grade austenitic stainless steel tubes including SUPER304H® (C.C. 2328), TP347HFG, NF709® , TEMPALOY A-3® , HR3C® (TP310HCbN) and TEMPALOY CR30A® were selected and installed in the superheater of the Eddystone No.1 boiler for the purpose of extending tube service life by reducing fire-side and steam-side corrosion. No significant corrosion was observed on the outer surfaces at 75,075h of exposure. Precipitates due to exposure were identified by TEM-EDS analysis. The thickness of steam oxidation scale was less in high-Cr materials, and high Cr content was thus demonstrated to have effectively improved steam oxidation resistance. HR3C showed comparatively poor impact properties, while the other materials exhibited acceptable impact values of over 30J/cm2 at 20°C. All materials showed reduced creep strength compared with unexposed materials after service exposure under high stress test conditions. However the differences became smaller at lower stresses.Copyright © 2007 by ASME