Using of transpassive dissolution for detection of structural changes in 9Cr

Abstract

The development of structural changes during long term service is a serious problem of heat resistant steels due to formation of deleterious Cr- and Mo-rich phases in the structure. Since chromium and molybdenum are easily soluble by transpassive mechanisms, electrochemical polarisation in appropriate electrolyte could be used as method for detection of such phases. Transpassive behaviour of creep resistant steel 9Cr–1Mo (P91) in different states of heat treatment/long term aging was studied in this work. Materials were studied by means of electrochemical methods, OES analysis and SEM observation. Potentiodynamic curves of tempered and aged (650°C/10 000 h) samples in NaOH solution show a significant local peak in transpassivity/secondary passivity region. No peak was observed on polarisation curve of quenched sample. Formation of the local peak on polarisation curve is assumed to be caused by dissolution of Cr- and Mo-rich phases by a transpassive mechanism. This assumption was confirmed using potentiostatic etching, chemical analysis of electrolytes and microstructure observation.

Keywords

9Cr–1Mo creep resistant steel Transpassivity Potentiodynamic measurement Electrochemical detection

Get full access to this article

View all access options for this article.

References

Maruyama

Sawada

and Koike

: ‘Strengthening mechanisms of creep resistant tempered martensitic steel‘, ISIJ Int. 2001 41 (6) 641–653.

Nagode

Kosec

Ule

and Kosec

: ‘Review of creep resistant alloys for power plant applications‘, Metalurgija 2011 50 (1) 45–48.

Klueh

: ‘Elevated temperature ferritic and martensitic steels and their application to future nuclear reactors’ Int. Mater. Rev. 2005 50 (5) 287–310.

Kaybyshev

Skorobogatykh

and Shchenkova

: ‘New martensitic steels for fossil power plant: Creep resistance’ Phys. Met. Metallogr. 2010 109 (2) 186–200.

Shen

Kim

Cho

Han

and Ryu

: ‘Precipitate phases of a ferritic/martensitic 9% Cr steel for nuclear power reactors‘, Nucl. Eng. Des., 2009 239 (4) 648–654.

Hald

: ‘Microstructure and long-term creep properties of 9-12% Cr steels’ Int. J. Press. Ves. Pip. 2008 85 (1-2) 30–37.

Tavares

SSM

da Silva Mr and Neto

: ‘Magnetic property changes during embrittlement of a duplex stainless steel’ J. Alloy. Compd. 2000 313 (1-2) 168–173.

de Macedo Silva

de Albuquerque

VHC

Leite

Varela

ACG

Moura

EPd

and Tavares

JMRS

: ‘Phase transformations evaluation on a UNS S31803 duplex stainless steel based on nondestructive testing’ Mater. Sci. Eng. A 2009 A516 (1-2) 126–130.

May

de Sousa

CAC

and Kuri

: ‘Aspects of the anodic behaviour of duplex stainless steels aged for long periods at low temperatures’ Corros. Sci. 2003 45 (7), 1395-1403.

10.

Domínguez-Aguilar

and Newman

: ‘Detection of deleterious phases in duplex stainless steel by weak galvanostatic polarization in alkaline solution‘, Corros. Sci., 2006 48 (9), 2560-2576.

11.

Watanabe

and Shoji

: ‘The evaluation of in-service materials degradation of low-alloy steels by the electrochemical method’ Metall. Trans. A 1991 22A (9), 2097-2106.

12.

Hyun

Lee

and Kim

: ‘The evaluation of material degradation in modified 9Cr-1Mo steel by the electrochemical technique’ Key Eng. Mater. 2004 270-273, 1206-1211.

13.

Rapouch

and Bystriansky

: ‘Behaviour of creep-resistant steels in a transpassive zone’ Koroze Ochrana Mater. 2012 56 (2) 31–37.

14.

Abd El-Rehim

Abd El-Haleem

Abd El-Wahaab

and Shalab

: ‘Corrosion behaviour of 18-8 austenitic stainless steel in NaOH solutions and the effect of chloride ions‘, Surf. Technol. 1983 19 (3) 261–271.

15.

Bojinov

Betova

Fabricius

Laitinen

Raicheff

and Saario

: ‘The stability of the passive state of iron-chromium alloys in sulphuric acid solution’ Corros. Sci. 1999 41 (8), 1557-1584.

16.

Betova

Bojinov

Laitinen

Makela

Pohjanne

and Saario

: ‘The transpassive dissolution mechanism of highly alloyed stainless steels: I. Experimental results and modelling procedure‘, Corros. Sci. 2002 44 (12), 2675-2697.

17.

Holcomb

: ‘Steam oxidation and chromia evaporation in ultrasupercritical steam boilers and turbines‘, J. Electrochem. Soc. 2009 156 (9) C292–C297.

18.

Ehlers

Young

Smaardijk

Tyagi

Penkalla

Singheiser

and Quadakkers

: ‘Enhanced oxidation of the 9%Cr steel P91 in water vapour containing environments’ Corros. Sci. 2006 48 (11), 3428-3454.

19.

Essuman

Meier

Zurek

Hansel

and Quadakkers

: ‘The effect of water vapor on selective oxidation of Fe–Cr alloys’ Oxid. Met. 2008 69 (3-4) 143–162.

20.

Pourbaix

: ‘Atlas of electrochemical equilibria in aqueous solutions’ 2nd edn; 1974

Houston

National Association of Corrosion Engineers.

Using of transpassive dissolution for detection of structural changes in 9Cr–1Mo creep resistant steel

Abstract

Keywords

Get full access to this article

References