Non-destructive evaluation of thermal aging embrittlement of duplex stainless steels

Y. S. Yi, T. Tomobe, Y. Watanabe, T. Shoji

Research output: Chapter in Book/Report/Conference proceedingConference contribution

10 Citations (Scopus)

Abstract

The non-destructive evaluation procedure for detecting thermal aging embrittlement of cast duplex stainless steels has been investigated. As a novel measurement technique for the thermal aging embrittlement, an electrochemical method was used and anodic polarization behaviors were measured on new, service exposed, and laboratory aged materials and then were compared with the results of the mechanical tests and microstructural changes. During the polarization experiments performed in potassium hydroxide solution (KOH), M23C6 carbides on phase boundary were preferentially dissolved, which was confirmed by the SEM after polarization measurements. The preferential dissolution of M23C6 carbides appeared as the large anodic current density on the polarization curves. Through the electrochemical potentiokinetic reactivation (EPR) experiments in sulphuric acid solution, the relation between reactivation ratio and microstructural change was discussed. In EPR experiments, the reactivation peaks corresponding to Cr depleted zone formed on ferrite/austenite boundaries by the precipitation of M23C6 carbides were obtained. Also, the non-destructive measurement and evaluation method of spinodal decomposition, which has been known as the primary mechanism of embrittlement in ferrite phase, was reviewed. When the materials, where spinodal decomposition occurred, were polarized in an acetic acid solution (CH3COOH), larger critical anodic current densities were observed than those observed on new materials, and these results were consistent with the result of the microhardness measurement. Concerning these polarization results, a critical electric charge, which was required for stable passive films in passive metals, was defined and the relationship between the microstructural changes and this charge amount was reviewed under various polarization conditions in order to verify the polarization mechanism of the spinodally decomposed ferrite phase.

Original languageEnglish
Title of host publicationProc 6 Int Symp Environ Degrad Mat Nucl Power Syst Water React
EditorsRobert E. Gold, Edward P. Simonen
PublisherPubl by Minerals, Metals & Materials Soc (TMS)
Pages409-417
Number of pages9
ISBN (Print)0873392582
Publication statusPublished - 1993 Dec 1
EventProceedings of the 6th International Symposium on Environmental Degradation of Materials in Nuclear Power Systems-Water Reactors - San Diego, CA, USA
Duration: 1993 Aug 11993 Aug 5

Publication series

NameProc 6 Int Symp Environ Degrad Mat Nucl Power Syst Water React

Other

OtherProceedings of the 6th International Symposium on Environmental Degradation of Materials in Nuclear Power Systems-Water Reactors
CitySan Diego, CA, USA
Period93/8/193/8/5

ASJC Scopus subject areas

  • Engineering(all)

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