The standardized laboratory test according to NACE TM0284-2003 for the determination of hydrogen-induced cracking (HIC) resistance provides relative susceptibility of material which is established in two different test solutions of different severity. The fitness of the materials for the intended application (fitness-for-purpose) is assured for in-field environmental conditions when the test is successfully passed.

The objectives of the investigations addressed in this paper were verification of sour service suitability of steels which do not qualify or only partially qualify for sour service when tested under standard test conditions and definition of boundary conditions for HIC resistance of these steels with regard to solution pH and H2S partial pressure. Therefore HIC tests were performed on HIC susceptible submerged arc welded (SAW) large-diameter pipe API 5L grade X65 linepipe steel under different test conditions with pH ranging between 3.5 and 6.3 and H2S partial pressures between 0.001 and 1 bar. Based on the outcome of the test results HIC severity regions were defined in a similar manner to the SSC regions of ISO 15156-2. It was shown that, compared to the ISO 15156-2 SSC regions, for susceptible X65 steels the non-sour region of the HIC severity diagram is shifted to a higher H2S partial pressure of 0.1 bar. A slightly sour region and a severely sour region were also defined.

Subject
Hydrogen induced cracking, Test methods, Materials, Piping, Inspection, Metallography, Partial pressures, Chemical composition, Steel, Hydrophobic interaction chromatography, Sulfide stress cracking, Stress corrosion cracking, Hydrogen
Keywords:
Sour service, HIC, fitness-for-purpose, low alloy steel, large-diameter pipe, SAW, longitudinal weld
© 2006 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).
2006
Association for Materials Protection and Performance (AMPP)
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