Several methods are available for determining the threshold stress intensity for stress corrosion cracking (KISCC) of a material. The required test time for obtaining meaningful KISCC data often ranges from hundreds to thousands of hours. Research has been conducted in a controlled environment to demonstrate the feasibility of developing a rapid test technique for determination of KISCC. Corrosion-fatigue and rising-load experiments were conducted on high strength 4340 steel and 7075-T6 aluminum alloy using accelerating pollutants such as sulfur dioxide, nitrogen dioxide, surface salt and ambient air to 100% relative humidity (RH) air in a specially designed atmospheric chamber. A KISCC value of 45-46 MPa m for 4340 steel at a 1440 MPa yield strength level was determined by corrosion-fatigue test in an environment of 1000ppm NO2 + 80% RH which compared well with 49-52 MPa m as determined by means of rising load tests and 44-46 MPa m by quantitative fractography. Similarly, a KISCC value of 13-14 MPa m was found for Al 7075-T6 in an environment of 100 ppm NO2 + 80% RH + 5% surface salt by extrapolation from corrosion fatigue test which was in good agreement with a value of 13.2 MPa m obtained from rising load tests. These results indicate that such corrosion fatigue tests can be used as accelerated test techniques for determination of KISCC.

Subject
Test methods, Steel surfaces, Corrosion fatigue, Materials, Salts, Sodium chloride, Extrapolation, Stress, Mechanical failure, Test environments, Steel, Yield strength, Stress corrosion cracking
© 1984 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).
1984
Association for Materials Protection and Performance (AMPP)
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