Standard and Pd-enhanced Ti-3Al-8V-6Cr-4Zr-4Mo (Ti-38644 or Beta-C™ titanium) alloy plate, billet, and tubular materials were evaluated with respect to their SCC resistance in a simulated worst-case deep sour gas well environment up to 274° C (525° F). Long term C-ring tests of standard Ti-38644 tubulars revealed no SCC susceptibility below 232° C (450° F) within test matrix parameters. Slow strain rate (SSR) testing of standard Ti-38644 tubulars, however, produced much more conservative SCC thresholds of 163-177°C (325-350°F) for extruded/STA pipe and 177-191°C (350-375°F) for the more ductile cold pilgered/STA pipe. Stress cracking above these threshold temperatures was primarily transgranular cleavage and probably anodically controlled.

SSR testing of all Pd-enhanced Ti-38644 products revealed SCC threshold improvements over standard Ti-38644 in the range of 42-83°C (75-150°F) in this worst-case environment. SCC resistance was synergistically elevated when both cold processing and Pd enhancement were incorporated into the Ti-38644 alloy product, achieving SCC thresholds in excess of 246°C (475°F). This SSR data base suggests that Pd-enhanced Ti-38644 can provide more than adequate SCC resistance for the worst-case deep sour gas well environments currently anticipated.

Subject
Test methods, Strain rate, Piping, Autoclaves, Sour environments, Sour gas, Transgranular stress corrosion cracking, C ring stress corrosion testing, Brines, Titanium, Titanium alloys, Stress corrosion cracking, Chloride stress corrosion cracking
© 1992 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).
1992
Association for Materials Protection and Performance (AMPP)
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