In stress corrosion studies, crack velocity plotted with respect to stress intensity generally yields a characteristic curve with three distinct regions. The first region (stage I) exhibits a threshold (KISCC) followed by a rapid increase in crack velocity (da/dt) for small changes in stress intensity. The second region (stage II) is characterized by an essentially constant crack velocity with increases in the stress intensity. The third region (stage III) exhibits a rapid increase in crack velocity for small increases in stress intensity leading to fracture.

Stage I behavior has been poorly characterized in the corrosion literature due to previous emphasis on determining the threshold (KISCC) and the difficulty and uncertainty in the measurements of a large increase in the crack velocity with only incremental changes in stress intensity. In order to study the stage I behavior more thoroughly, tests were conducted in the stage I regime measuring crack velocity as a function of constant stress intensity.

Constant K specimens were prepared according to the Mostovoy design, a tapered double cantilever beam specimen that produces a constant stress intensity from a constant applied load. The specimens were prepared from a Type 304 stainless steel containing 0.06 wt% C. This material was solution annealed at 1100°C for 1 hour, water quenched, and subsequently annealed at 625°C for 24 hours to produce sensitization. A sodium thiosulfate solution at 50°C was chosen as the test environment, due to the presence of aggressive anions that promote IGSCC in sensitized Type 304 stainless steel.

Subject
Anions, Materials, Stress intensity, Stress cracking, Stress, Constants, Experimental data, Crack velocity, Thiosulfate, Crack length, Specimen preparation, Stainless steel, Cracks
Keywords:
Stress corrosion, tapered DCB specimen, sensitized stainless steel, stage I behavior, IGSCC, sodium thiosulfate, Type 304 stainless steel
© 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)
You do not currently have access to this content.