The IGSCC, sensitization, and microstructure study of Alloys 600 and 690

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

42 Scopus Citations
View graph of relations

Author(s)

Detail(s)

Original languageEnglish
Pages (from-to)449-457
Journal / PublicationNuclear Engineering and Design
Volume144
Issue number3
Publication statusPublished - 1 Nov 1993
Externally publishedYes

Abstract

Both Alloys 600 and 690 were studied to understand the effect of heat treatment on the sensitization and SCC behavior of these alloys. The microstructural evolution and chromium depletion near the grain boundaries were carefully studied using analytical electron microscopy. The majority of the precipitates formed in Alloy 600 was found to be M7C3 with a hexagonal structure (a0 = 1.398 nm, c0 = 0.45 nm); whereas the carbides found in Alloy 690 were identified as M23C6 with an fcc structure (a0 = 1.06 nm). Modified Huey test performed in boiling 40% HNO3 was used to study the effect of heat treatment and degree of sensitization. Constant load tests and constant extension rate tests were performed in the solution containing sodium thiosulfate to study the SCC resistance of these alloys. The results of the constant load tests for Alloy 600 indicated that the susceptibility to SCC is sensitive to the chromium depletion depth at grain boundary, and the minimum value to prevent SCC failure is approximately 8 wt%. No SCC was observed for Alloy 690 tested using constand load and CERT in the same environments. All tests showed that Alloy 690 has a far better resistance to intergranular attack and SCC than Alloy 600, which is believed due to its high chromium content. It is therefore anticipated that Alloy 690 now a better substitute to Alloy 600 as a steam generator tubing material for pressurized water reactor will also offer a superior corrosion resistance when "sensitized" and in particular if exposed to sulfur containing media such as thiosulfate solutions. © 1993.

Citation Format(s)

The IGSCC, sensitization, and microstructure study of Alloys 600 and 690. / Kai, J. J.; Tsai, C. H.; Yu, G. P.
In: Nuclear Engineering and Design, Vol. 144, No. 3, 01.11.1993, p. 449-457.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review