Unexpected brittle failures of UNS N05500 drill string parts and nonmagnetic drill collars have recently been observed in cases where the UNS N05500 components were galvanically coupled to carbon steel in concentrated salt solutions at temperatures between ambient and higher than 373 K. Cracking occurred preferably at locations with a tri-axial stress condition (roots of threads) and has been ascribed to hydrogen embrittlement.

Mechanical and slow strain rate tests with UNS N05500, either at the free corrosion potential or galvanically coupled to carbon steel, have now been carried out in MgCl2 mud to determine the conditions under which hydrogen embrittlement occurs. A number of alternative high-strength non-magnetic alloys were included in the tests. It was found that under all our test conditions UNS N05500 was embrittled by hydrogen when galvanically coupled to carbon steel. It was immune to cracking at its free corrosion potential. Under the conditions of our tests, alloys SCF 19, N 10276 and R 30035 were not susceptible to either stress corrosion cracking or hydrogen embrittlement.

Subject
Hydrogen embrittlement, Materials, Intergranular stress corrosion cracking, Drilling fluid, Carbon cracking, Transgranular stress corrosion cracking, Free corrosion potential, Carbon steel, Fracture, Alloys, Ductile fracture, Stress corrosion cracking, Hydrogen
© 1986 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).
1986
Association for Materials Protection and Performance (AMPP)
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