Low-alloy steels containing chromium and molybdenum as alloying elements are extensively used in the powergenerating and petroleum industries. Of these, 2.25Cr-1Mo and 1.25Cr-0.5Mo ferritic steels have been a logical choice for power plants and pressure vessels.

Hydrogen in steel is a serious problem since hydrogen-induced failures are common. It has caused numerous failures during construction and during service. Sulphide stress cracking (SSC) failure in welded structures often occurs in the weld metal and heat-affected zone (HAZ); the rapid heating and cooling during welding produces a hardened microstructure and residual stresses, which makes these regions vulnerable to cracking.

The corrosion behaviour of C/Mn and Cr/Mo steels and sulphide-stress cracking (four-point bend test) was investigated in NACE solutions TM0177 and TM0284 containing hydrogen sulphide (H2S).

The results obtained from the present studies will be presented and discussed. The data indicated that hardness was the primary factor controlling the SSC resistance of these steels.

Subject
Materials, Yield stress, Stress cracking, Acidity, Base metals, Repair, Heat, Steel, Sulfide stress cracking, Hardness, Cracks, Weld metal, Stress corrosion cracking
Keywords:
hydrogen, SCC, H2S, hardness, welding, HAZ, stress
© 1994 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).
1994
Association for Materials Protection and Performance (AMPP)
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