Stress corrosion cracking tests were conducted on damaged (indented) and undamaged but highly stressed specimens of Monel 400 as well as damaged tubing that was stress relieved by a resistance heat treatment. The specimens were exposed for up to 10,000 hours to the vapor phase of a concentrated ammonium hydroxide solution at 300°C (572°F). Cracking was observed in many of the specimens that were stressed in excess of the material's yield stress, i.e., approximately 276 MPa (40,000 psi). Cracks were also observed in the damaged areas of steam generator tubes. No cracking was observed in any of the resistance heat treated stress relieved specimens. Thus a resistance heat treatment of, at least, 600°C (1112°F) for a few seconds will greatly improve the stress corrosion resistance of Monel 400 steam generator tubing.

Subject
Tubes, Ammonia, Stress cracking, Vapors, Thermal stress, Stress, Metallographic examination, Tubing, U bends, Monel alloys, Stress corrosion cracking, Damage, Residual stress
© 1982 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).
1982
Association for Materials Protection and Performance (AMPP)
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