The oil and gas industry has the last few years experienced several major failures in subsea components made of Duplex stainless steel due to Hydrogen Induced Stress Cracking (HISC) with hydrogen introduced from the cathodic protection system. The main objective of the work presented in this paper has been to gain a better understanding of the HISC fracture mechanism. A test method allowing examination of the deformation behaviour in the individual phases during stepwise loading has been developed, and further the deformation in the individual phases have been documented.

Both as delivered and hydrogen pre-charged samples revealed that the plastic deformation starts in the austenitic phase (γ) while the plastic deformation along slip lines in the ferrite appears to be initiated from dislocation pile ups at the austenite/ferrite phase boundaries. For specimens charged with Hydrogen, HISC took place in the ferrite, most likely initiated as a result of dislocation pile ups in adjacent austenite phases.

Subject
Materials, Deformation, Dislocation, Microstructure, Crack initiation, Stress cracking, Stress, Slip, Ferrite, Fracture, Plastic deformation, Austenite, Hydrogen
Keywords:
duplex stainless steel, microstructure, hydrogen cracking, dislocations, pile-ups
© 2007 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).
2007
Association for Materials Protection and Performance (AMPP)
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