A cracked reducer flange was analyzed for the cause of the failure. The flange was carefully cut in order to obtain samples for metallographic, x-ray, and Scanning Electron Microscopy (SEM) Examinations. The examinations revealed that the introduction of chloride ions in the operational service led to pitting corrosion in the inner surface of the flange. Chloride ions were probably the result of chemical contaminations, i.e., cleaning contamination during shutdown of the operation. The introduction of corrosion pits, caused unexpected load stress intensification and cracking of the flange. Consequently, stress corrosion cracking emanated from the pits under the influence of chloride attack and operational pressure. Then the cracks propagated in a transgranular manner, in the radial direction of the flange, until the final failure occurred.

Subject
Scanning electron microscopy, Materials, Secondary cracks, Microstructure, Reactors, Transgranular stress corrosion cracking, Flanges, Mechanical failure, Pitting, Stainless steel, Elements, Cracks, Chloride stress corrosion cracking
Keywords:
Reducer Flange, Pitting Corrosion, Stress Corrosion Cracking, Metallographic Examination, X-Ray, Scanning Electron Microscopy, Fracture roughness, Stress Intensity Factor
© 2001 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).
2001
Association for Materials Protection and Performance (AMPP)
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