The Effect of Temperature on the Formation of Oxide Scales Regarding Commercial Superheater Steels
This study addresses the surface changes of three commercial steels (a low alloy ferritic 10CrMo9-10 steel, a Nb-stabilized austenitic AISI347 steel, and a high alloy austenitic Sanicro 28 steel) by comparing the oxide scale thicknesses, chemical compositions, and surface morphologies of samples after pre-oxidation at 200, 500 and 700 °C with different exposure times (5 and 24 h) under humid or dry conditions. With all three steels, the oxide scale thickness increased as functions of temperature and exposure time, the effect of temperature being more prominent than the effect of exposure time. The presence of water resulted in thicker oxide scales at the studied low alloy ferritic steel, whereas in the two austenitic steels, the presence of water increased chromium diffusion to the oxide scale rather than the scale thickness. The oxide layers characterized and analyzed in this paper will be further studied in terms of their abilities to resist corrosion by exposing them under corrosive conditions. The results regarding the corrosion resistance of the steels will be published in a sequel paper.
KeywordsPre-oxidation High-temperature oxidation Low alloy ferritic steel Austenitic stainless steel High alloy austenitic stainless steel
This work has been carried out within the Academy of Finland project “Novel Approaches to Study Corrosion Mechanisms in High-temperature Industrial Processes” (Decision No. 296435). This work has been partly carried out within CLIFF (2014–2017) as part of the activities of Abo Akademi University. Other research partners are VTT Technical Research Centre of Finland Ltd, Lappeenranta University of Technology, Aalto University and Tampere University of Technology. Support from the National Technology Agency of Finland (Tekes), Andritz Oy, Valmet Technologies Oy, Amec Foster Wheeler Energia Oy, UPM-Kymmene Oyj, Clyde Bergemann GmbH, International Paper Inc., and Top Analytica Oy Ab is gratefully acknowledged. The authors would like to thank Mr. Linus Silvander for operating the SEM-apparatus and Mr. Jyrki Juhanoja for operating the XPS-apparatus.
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