Twenty-nine Inconel alloy 600 steam generator tube U-bends were removed from the Trojan plant as part of a program to document the cause of leakage in tubes with the smallest radius bend. All of the tubes were radiographed and selected tubes were subjected to detailed dimensional measurements, light metallography, scanning electron microscopy, transmission electron microscopy, hardness measurements, and chemical analyses by spark source mass spectrometry, energy dispersive X-ray analysis, electron beam microanalysis, and Auger electron spectroscopy. Additional information was obtained by re-examining U-bends previously studied from other plants. Tube leakage resulted from multiple initiation and intergranular cracking from the tube ID at the extrados and at the most well-defined transition from curved to straight section. This cracking was found on 3 out of 26 small radius U-bends from the Trojan plant. Three tubes studied with the next largest radius bend had no indications or well-defined transitions. No consistent nor significant relationship could be established between cracking and the other characteristics measured.

Subject
Nickel based alloys, Tubes, Walls, Steam generators, Metallography, Stress cracking, Intergranular cracking, U bends, Deposit corrosion, Elements, Hardness, Alloys, Cracks
© 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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