An accelerated laboratory test method was developed to evaluate stress corrosion cracking (SCC) of kraft continuous digesters. The method uses circular patch test welds, made from 38 mm thick A516 Gr. 70 steel plate. The specimens were exposed to a 110 C solution containing 40 g/L NaOH and 20 g/L Na2S, at a controlled electrochemical potential. Several different welding procedures were evaluated for resistance to SCC, along with stress relief, shotpeening, sealed thermal spray coatings, and weld overlays of Inconel* 82 and 309L SS.

Stress relief, shotpeening and sealed thermal spray coatings prevented SCC during the test. Compared to a control specimen, SCC was less severe after temper-bead welding, and after welding with an E6010 capping pass. Severe SCC occurred in a specimen welded with the worst-case welding procedure. Deep, circumferential SCC occurred in the carbon steel at the edge of the Inconel 82 weld overlay. SCC was also observed at the interface between the 309L SS weld overlay and the base plate.

Subject
Digesters, Corrosion prevention, Welding, Inspection, Stress cracking, Crack depth, Sealants, Specimen preparation, Tensile stress, Cracks, Stress corrosion cracking, Residual stress, Thermal spray coatings
© 1987 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).
1987
Association for Materials Protection and Performance (AMPP)
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