Exposure temperature has a known effect on sulfide stress cracking (SSC) in low alloy steels where elevated temperatures permit the use of oil country tubular goods (OCTG) in sour conditions that would not be survivable at lower temperatures. In order to assess SSC susceptibility, NACE MR0175 / ISO15156-2 and API 5CT advise or require the use of room temperature NACE exposure tests in H2S-containing brines and, consequently, the bulk of qualification data on OCTG has been obtained at these conditions. Previous publications have demonstrated the effect of lower temperatures, e.g. 40°F, testing on KISSC values of low alloy steel using double cantilever beam (DCB) tests showing a reduction on sour toughness when the temperature is lowered from 75°F to 40°F. This KISSC data provides a clear indication of SSC severity at 40°F on crack propagation; however, very little data is available pertinent to crack initiation at temperatures lower than 75°F.

In this work, several crack initiation tests were performed in mild sour conditions and demonstrated that at low temperature crack initiation susceptibility is increased. Details of the results are discussed within the context of traditional SSC qualification tests and materials selection standards along with the theoretical understanding of SSC fundamentals. Cracking tendency and time-to-failure are reviewed within the context of environmental and material parameters that are altered by the exposure temperature including hydrogen diffusion, corrosion rate, dissolved H2S concentration, and the behavior of hydrogen traps.

Subject
Test methods, Tubular goods, Materials, Hydrogen concentration, Corrosion rate, Crack initiation, Stress cracking, Sour conditions, Stress, Steel, Sulfide stress cracking, Hydrogen, Hydrogen stress cracking
Keywords:
H2S, sour, sulfide stress cracking, crack tip hydrogen, OCTG, temperature
© 2019 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).
2019
Association for Materials Protection and Performance (AMPP)
You do not currently have access to this content.