Radiation-induced chromium depletion near grain boundaries have been simulated through controlled thermal treatments, and its influences on the degree of sensitization(DOS) and intergranular stress corrosion cracking(IGSCC) of commercial purity AISI 304 austenitic stainless steel were investigated in this study.

Microstructural and microchemistry evolution measurements were studied by using STEM/EDX microscopy. Constant extension rate tensile(CERT) and electrochemical potentiokinetic reactivation (EPR) tests under various environments were performed using the thermally-treated specimens to study the effects of different Cr depletion profiles on IGSCC and IGC susceptibility of this material.

Microstructural examination indicated that M23C6 carbides along grain boundaries were observed in all heat-treated specimens. It was found that after heat-treated at 650°C/50h, significant Cr depletion was observed near grain boundary areas. The CERT and EPR test results indicated that the width and depth of chromium depletion determined its DOS and the resistance to IGSCC and IGC. It was concluded that a critical chromium level of 15wt% is needed to prevent IGSCC in 288°C pure water for 304 specimens. The larger depleted volume below the critical chromium value exhibited more fraction of intergranular fracture surface in CERT tests. While the more depletion width at the critical chromium level would result in more intergranular corrosion in ERP test.

Subject
Materials, Carbides, Intergranular stress corrosion cracking, Precipitation (solids), Dislocation, Chromium, Fracture surfaces, Intergranular cracking, Mechanical failure, Stainless steel, Fracture, Grain boundary, Heat treatment
Keywords:
Stainless steel, intergranular corrosion, stress corrosion cracking
© 1993 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).
1993
Association for Materials Protection and Performance (AMPP)
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