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Microstructure Study of NiCrAlY and FeCrAlY Exposed to Superheated Steam at 800?C

[+] Author and Article Information
Alberto Sáez-Maderuelo

CIEMAT, Avda. Complutense 40, 28040. Madrid (Spain)
alberto.saez@ciemat.es

Michael McTaggart

Queens University, 99 University Ave, Kingston, ON K7L 3N6, (Canada)
michael.mctaggart@queensu.ca

Xiao Huang

Carleton University, 1125 Colonel by Dr, Ottawa, ON K1S 5B6, Canada
xiao.huang@carleton.ca

César Maffiotte

CIEMAT, Avda. Complutense 40, 28040. Madrid (Spain).
cesar.maffiotte@ciemat.es

1Corresponding author.

ASME doi:10.1115/1.4037668 History: Received April 27, 2017; Revised August 10, 2017

Abstract

Supercritical Water cooled Reactor (SCWR) was chosen as Generation IV reactor concept in Canada to utilize Canada's expertise and technical capabilities from past research and designs. The conceptual design of Canadian SCWR has a core outlet temperature of 650?C at 25 MPa and a peak cladding temperature as high as 800?C. Corrosion/oxidation resistance is an important factor in material selections and also coating considerations. Most of the reported SCW test data have been obtained at temperatures up to 700?C as no autoclave exists that can operate above 700°C at supercritical pressures and temperatures. Superheated steam is used as a surrogate fluid to SCW in this study to evaluate two coating materials, FeCrAlY and NiCrAl, at 800°C. The results showed that the FeCrAlY became discolored rapidly while NiCrAl still mained some metallic sheen after 600 hours. The weight change results suggest that more oxide formation took place on FeCrAlY than NiCrAl. In particular, grain boundary oxide (Al2O3) formed on FeCrAlY surface upon exposure to steam after 300 hours. Further exposure caused more intragranular Al2O3 to form, in addition to magnetite formation on the grain boundary regions. For NiCrAl samples, NiO formed after steam exposure for 300 hours. Spinel and (Cr,Al)2O3 were also found after 300 hours along with very limited amount of Al2O3. After 600 hours, Al2O3 became well developed on NiCrAl and the coverage of spinel and Cr2O3 on the surface reduced.

Copyright (c) 2017 by ASME
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