The corrosion behavior of a ferritic-martensitic steel NF616 and an austenitic stainless steel D9 exposed to supercritical water (SCW) at two different dissolved oxygen concentrations, 25ppb and 2 ppm, for exposure times of up to 505 hours at 500°C was characterized. The oxide development and microstructural characteristics of the oxides that formed on the samples were analyzed by measuring weight change, oxide layer thickness, and compositional variation through the oxide layer using a Scanning Electron Microscope (SEM) with Energy Dispersive Spectroscopy (EDS) capabilities. The dissolved oxygen concentration plays a significant role in the oxidation behavior of the alloys. Both alloys exhibited much finer oxide particulates in the outer oxide layer under exposure conditions with higher oxygen concentration. For these short time tests, both NF616 and D9 showed a tendency to form a stable, self-protective oxide layer, but for D9 exposed to high oxygen concentration, a severe exfoliation of the outer oxide was observed.

Subject
Materials, Iron oxide, Oxides, Oxide formation, Oxide layers, Oxide thickness, Exfoliation, Oxide scales, Oxide surfaces, Steel, Oxygen, Dissolved oxygen, Oxidation
Keywords:
oxidation, corrosion, supercritical water reactor, Cr steels, ferritic-martensitic steel, austenitic steel
© 2005 Association for Materials Protection and Performance (AMPP). All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means (electronic, mechanical, photocopying, recording, or otherwise) without the prior written permission of AMPP. Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
2005
Association for Materials Protection and Performance (AMPP)
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