Analytical electron microscopy of a crack tip extracted from a stressed Alloy 800 sample exposed to an acid sulfate environmentMicron


S.Y. Persaud, A.G. Carcea, J. Huang, A. Korinek, G.A. Botton, R.C. Newman
Structural Biology / Cell Biology


Congress at York

A. of York


Brett A. S. Martin, University of Otago) is an associat pro-, Christina Kwai-Choi Lee, University of Auckland) is a se-

Metabolic studies in prolonged fasting

A. Rapoport, G.L.A. From, H. Husdan


Micron 61 (2014) 62–69

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Analytical electron microscopy of a crack tip extr

Alloy 8 vi

S.Y. Persa ott a Department o t, Tor b Department o Maste

ON L8S 4M1, C a r t i c l

Article history:

Received 7 No

Received in re

Accepted 14 F

Available onlin



Crack tip


Acid sulfate


Alloy 800 ound oy80 depth ut th ism on be ack in x oxi hed i

CC in 1. Introduction

Alloy 80 for Alloy 60 in many loc to a perceiv positions o and Gorma not immun ments (Pers not been st

J.F. Newma susceptibili performed exposures i and in som to 350 ◦C. alloy comp dependence in experime ∗ Correspon ∗∗ Correspon

E-mail add roger.newman evidencewas obtained. Reduced sulfur species are known to impair http://dx.doi.o 0968-4328/©0 is considered a replacement in nuclear power plants 0 steam generator tubing and austenitic stainless steel ations, including reactor pressure vessel internals, due ed increase in corrosion resistance. The nominal comf Alloys 600 and 800 are given in Table 1 (Staehle n, 2003; Bauccio et al., 1993). Alloy 800 is certainly e to stress corrosion cracking in acid sulfate environaud et al., 2013; Gomez-Briceno et al., 2010), but has udied extensively. In the 1980s, research was done by n on the acid sulfate stress corrosion cracking (AcSCC) ty of Alloys 600 and 690 (Newman, 1983). The author constant extension rate tests (CERT) and autoclave n an acid sulfatemixture consisting of Na2SO4, NaHSO4, e solutions FeSO4 at temperatures ranging from 305

Newman’s work revealed the potential dependence, osition dependence, and pH and sulfate concentration of AcSCC. Sulfate reduction was suggested to occur nts at temperatures greater than 330 ◦C, but no direct ding author. ding author. Tel.: +1 4169460604; fax: +1 4169788605. resses: (S.Y. Persaud), (R.C. Newman). the passivating effect of surface oxides and/or activate metal dissolution (Marcus and Oudar, 1980; Marcus and Protopopoff, 1993;

Marcus, 2002; Daret et al., 1999; Marcus and Talah, 1989). From a mechanistic point of view, AcSCC is not well understood in

Ni–Fe–Cr alloys, especially in the 800 alloy.

Studying the oxide chemistry at the crack tip would allow for increased understanding of themechanism of AcSCC. Transmission electron microscopy (TEM) provides the opportunity to do highresolution chemical analysis, and possibly chemical state analysis, to provide microstructural and chemical composition information.

The ability to prepare TEM samples containing SCC crack tips is challenging (Bruemmer and Thomas, 2001) but would lend great insight to the mechanism of cracking; in recent years, focused-ion beam (FIB) has been used to extract crack tips from SCC specimens for studies in intergranular and transgranular SCC of stainless steels (Huang and Titchmarsh, 2006; Huang et al., 2002; Wang et al., 1999) and SCC of Alloy 600 and stainless steels in high temperature hydrogenated water (Lozano-Perez et al., 2011; Lozano-Perez, 2008; Olszta et al., 2011; Schreiber et al., 2013). Similar approaches have also been applied in fatigue and hydrogen assisted cracking studies (Ro et al., 2012; Martin et al., 2011a, 2011b). The challenge with preparing an electron transparent region of a crack tip using a FIB is partly associated with the residual stress, which can cause the film to fall apart. Also, the depth of cracks is unknown without seeing the cross-section of the material. Methods have been rg/10.1016/j.micron.2014.02.011 2014 Elsevier Ltd. All rights reserved.00 sample exposed to an acid sulfate en uda,∗∗, A.G. Carceaa, J. Huangb, A. Korinekb, G.A. B f Chemical Engineering and Applied Chemistry, University of Toronto, 200 College Stree f Materials Science and Engineering, and Canadian Centre for Electron Microscopy, Mc anada e i n f o vember 2013 vised form 14 February 2014 ebruary 2014 e 25 February 2014 a b s t r a c t

Alloy 800 (Fe–21Cr–33Ni) has been f mechanism is notwell understood. All at 315 ◦C and cracks were found with containing crack tips is challenging, b tip would lend insight to the mechan technique combined with a focused i the cross-section of an acid sulfate cr

EDS and EELSwhich identified a duple

Cr-rich oxide and an outer oxide enric with respect to the mechanism of AcSacted from a stressed ronment onb, R.C. Newmana,∗ onto, ON M5S 3E5, Canada r University, 1280 Main Street West, Hamilton, susceptible to cracking in acid sulfate environments, but the 0C-ring sampleswere exposed to an acid sulfate environment s in excess of 300m after 60h. Preparation of a TEM sample e ability to perform high-resolution microscopy at the crack of acid sulfate stress corrosion cracking (AcSCC). The lift-out am sample preparation was used to extract a crack tip along an Alloy 800 C-ring. TEM elemental analysis was done using dewithin the crack; an inner oxide consisting of a thin 3–4nm n Fe and Cr. Preliminary conclusions and hypotheses resulted

Alloy 800. © 2014 Elsevier Ltd. All rights reserved.

S.Y. Persaud et al. / Micron 61 (2014) 62–69 63

Table 1

Nominal compositions of Alloys 600 and 800 in wt.% (Staehle and Gorman, 2003;

Bauccio et al., 1993).

Element Alloy 600 Alloy 800

Ni 72.0min 30.0–35.0

Fe 6.0–10.0 39.5min

Cr 15.0–17.0 19.0–23.0

Mn 1.00 max. 1.50 max.

Cu 0.50 max. 0.75 max.

S 0.01 max. 0.015 max.

Ti – 0.85–1.20

Si 0.50 max. 1.00 max.

C 0.025–0.05 max. 0.05–0.10 outlined for extraction of SCC crack tips using FIB (Huang et al., 2002; Lozano-Perez, 2008; Olszta et al., 2011), which has led to an increase in used for FIB of the “lift1998), simi with the ad

While th eral system demonstrat after expos

FIB and thi lytical elect spectroscop wereused f position an giving insig 2. Materia 2.1. Materi

Alloy 80 from Rolled

Table 2. Th shows the using Alloy

ASTM G38 potential di sulfate envi mately 2m

The sam ionized wat to a polytet the autocla