Supermartensitic stainless steels, recently made available as oil country tubular goods (OCTG), have been developed as a valuable cost effective alternative to duplex stainless steel for high CO2, medium/high chlorides, and very low H2S environments.

Experimental tests were carried out to determine the localised corrosion and the sulphide stress cracking (SSC) resistance of supermartensitic steel UNS S41425 to be used as OCTG in slightly sour oil and gas wells and to compare its performance with standard L80 API grade UNS S42000 13% Cr steel, considered as a reference.

Supermartensitic steels with yield range as per L80, C95, P110, API5CT, were developed and corrosion and mechanical properties were determined.

The influence of different chloride contents (NaCl 10÷50 g/l), hydrogen sulphide partial pressure (0.1÷100 kPa) and pH (2.7÷4.5) has been investigated in order to simulate production service conditions.

Modified NACE constant load test and slow strain rate (SSR) test were performed.

SSR gave the most severe evaluation for the SSC resistance.

In the SSR test supermartensitic steel is deeply influenced by the chloride concentration. Supermartensitic steel corrosion resistance is by far superior to that of 13% Cr.

Subject
Tubular goods, Materials, Sodium chloride, Gas pressure, Stress cracking, Mixtures, Partial pressures, Stress, Sodium chloride solution, Sulfide stress, Steel, Corrosion resistance, Sulfide stress cracking
Keywords:
Martensitic stainless steel, corrosion resistant alloys, oil country tubular goods, sour environment, stress corrosion cracking, sulphide stress cracking, hydrogen sulphide, carbon dioxide, slow strain rate test
© 1997 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).
1997
Association for Materials Protection and Performance (AMPP)
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