Fatigue Crack Growth Rate (FCGR) of X65 steels in sour environments is relevant to the performance of offshore risers and flowlines that can experience significant fatigue demand over the course of their life. The effect of environmental variables such as pH and pH2S on FCGR of X65 as a function of frequency (1Hz to 1mHz) was studied using fracture mechanics specimens at constant ΔK. Particularly, the role of bulk charging of hydrogen versus crack tip charging on the FCGR was evaluated in this work. The results of this work show that FCGR increases with decreasing frequency before reaching a plateau at low frequencies (<30mHz). The plateau FCGR values appeared to depend strongly on the concentration of hydrogen. The FCGR was proportional to f−0.5 in a range of conditions suggesting that the diffusion of hydrogen through the fracture process zone appeared to be the rate controlling step in FCGR.

Subject
Hydrogen sulfide, Hydrogen induced cracking, Corrosion fatigue, Piping, Hydrogen concentration, Corrosion rate, Diffusion, Sour environments, Fatigue crack growth rate, Steel, Fracture, Stress corrosion cracking, Hydrogen
Keywords:
Sour Environments, Fatigue Crack Growth Rate (FCGR), Flow lines
© 2012 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).
2012
Association for Materials Protection and Performance (AMPP)
You do not currently have access to this content.