Nickel base corrosion resistant alloys are thought to be strong candidates as a structural material for chemical processes using supercritical water (SCW). In recent years, Cr was considered as the most important alloying element to improve corrosion resistance in supercritical water. However, high Cr content can cause phase transformation in Ni base alloys due to poor phase stability at elevated temperatures for SCW processes from 400°C up to 650°C. The change in micro structure of the alloy can lead to degradation in corrosion resistance and mechanical properties.

In this study, thermal aging effects on corrosion resistance and mechanical properties of various Ni base alloys were investigated with corrosion test in supercritical water containing 0.01mol/kg-H2SO4 at 400°C/30MPa and with charpy impact tests. Reduction in impact toughness and in corrosion resistance was observed for all the alloys tested and degree of degradation was more significant for high Cr alloys. Importance of susceptibility to thermal aging in materials selection for supercritical applications was discussed.

Subject
Supercritical water, Materials, Corrosion resistant alloys, Corrosion rate, Thermal degradation, Nickel based alloys, Nickel chromium molybdenum alloys, Corrosion testing, Copper alloys, Mechanical properties, Commercial alloys, Corrosion resistance, Aging
Keywords:
Supercritical water, Ni-base alloy, aging effect, degradation, corrosion, mechanical property, Fracture toughness, Charpy impact value
© 2004 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).
2004
Association for Materials Protection and Performance (AMPP)
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