1 Institute of Materials, Shanghai University, Shanghai 200072 2 Laboratory for Microstructures, Shanghai University, Shanghai 200444 3 Western Energy Material Technologies Co. Ltd., Xi'an 710016
Cite this article:
Boyang WANG,Bangxin ZHOU,Zhen WANG,Jiao HUANG,Meiyi YAO,Jun ZHOU. CORROSION RESISTANCE OF Zr-0.72Sn-0.32Fe- 0.14Cr-xNb ALLOYS IN 500 ℃ SUPERHEATED STEAM. Acta Metall Sin, 2015, 51(12): 1545-1552.
Zirconium alloys with low alloying content are mainly used in the nuclear industry as structural materials because of their superior properties in terms of thermal neutron transparency, mechanical strength and corrosion resistance. They are used for fuel cladding tubes and channels. The reaction between zirconium and water at high temperature forms oxide film on the surfaces. In order to further improve the corrosion resistance of Zr-based cladding tubes, research has continued on developing new zirconium alloys. The corrosion resistance of Zr-0.72Sn-0.32Fe-0.14Cr-xNb alloys (x=0, 0.12, 0.28, 0.48, 0.97, mass fraction, %) was investigated in a superheated steam at 500 ℃ and 10.3 MPa by autoclave tests. All the plate specimens of zirconium alloys with thickness of 2.8 mm have a similar texture. The microstructure of alloys and oxide films on the corroded specimens were observed by TEM and SEM. The results showed that no nodular corrosion appeared on these alloys for 500 h exposure. The thickness of oxide layers developed on the rolling surface (SN), the surface perpendicular to the rolling direction (SR) and the surface perpendicular to the transversal direction (ST) after 500 h exposure was close to each other. There was no anisotropic corrosion resistance for these alloys. The corrosion rate of the alloys increased with the increase of Nb content after 250 h exposure when the Nb content exceeded 0.28%. In the alloy with low Nb content, the fcc-Zr(Fe, Cr)2 or fcc-Zr(Fe, Cr, Nb)2 precipitate was mainly formed, while the hcp-Zr(Fe, Cr, Nb)2 precipitate was frequently observed in the alloy with high Nb content. The corrosion resistance of Zr-0.72Sn-0.32Fe-0.14Cr-xNb alloys was improved by decreasing the Nb/Fe ratio. From a point of view for the improving corrosion resistance, the addition of Nb no more than 0.3% is recommended.
Fig.1 (0001) pole figure (a), inverse pole figures of the normal direction (ND) to rolling surface (b), transversal direction (TD) (c) and rolling direction (RD) (d) of 0.97Nb alloy annealed at 580 ℃ for 5 h
Specimen
fN
fR
fT
0Nb
0.765
0.059
0.176
0.12Nb
0.658
0.078
0.264
0.28Nb
0.703
0.083
0.213
0.48Nb
0.727
0.053
0.220
0.97Nb
0.701
0.061
0.238
Table 1 Texture factors fN, fR and fT in ND, RD and TD for Zr-0.72Sn-0.32Fe-0.14Cr-xNb alloys
Fig.2 TEM images of 0Nb (a), 0.12Nb (b) and 0.97Nb (c) alloys
Fig.3 TEM images and SAED patterns (insets) of second phase particles 1~3 in 0Nb (a), 0.12Nb (b) and 0.97Nb (c) alloys
Fig.4 Mass gain curves of Zr-0.72Sn-0.32Fe-0.14Cr-xNb alloys corroded in 500 ℃, 10.3 MPa superheated steam for different times
Fig.5 Variation of average corrosion rate of Zr-0.72Sn-0.32Fe-0.14Cr-xNb alloys with Nb contents after corrosion for 250~500 h
Fig.6 Fracture surface morphologies of oxide films formed on SN surface (rolling surface) after exposed in 500 ℃, 10.3 MPa superheated steam for 500 h for 0Nb (a), 0.28Nb (b) and 0.97Nb (c) alloys
Fig.7 Oxide thickness on rolling surface (SN), surface perpendicular to rolling direction (SR) and surface perpendicular to transversal direction (ST) as a function of exposure time for 0Nb (a), 0.12Nb (b), 0.28Nb (c), 0.48Nb (d) and 0.97Nb (e) alloys corroded in 500 ℃, 10.3 MPa superheated steam
[1]
Zhao W J, Zhou B X, Miao Z, Peng Q, Jiang Y R, Jiang H M, Pang H. Atom Energy Sci Technol, 2005; 39(suppl): 1
Sabol G P. In: Rudling P, Kammenzind B eds., Zirconium in the Nuclear Industry: Fourteenth International Symposium, ASTM STP 1467, Stockholm: ASTM, 2004: 3
[4]
Sabol G P, Comstock R J, Weiner R A. In: Garde A M, Bradley E R eds., Zirconium in the Nuclear Industry: Tenth International Symposium, ASTM STP 1245, Baltimore, MD: ASTM, 1994: 724
[5]
Nikulina A V, Markelov V A, Peregud M M. In: Bradley E R, Sabol G P eds., Zirconium in the Nuclear Industry: Eleventh International Symposium, ASTM STP 1295, Garmisch-Partenkirchen, Germany: ASTM, 1996: 785
[6]
Zhao W J. Rare Met Lett, 2004; 23(5): 15
[6]
(赵文金. 稀有金属快报, 2004; 23(5): 15)
[7]
Zhou B X. J Met Heat Treat, 1997; 18(3): 8
[7]
(周邦新. 金属热处理学报, 1997; 18(3): 8)
[8]
Liu W Q, Zhu X Y, Wang X J, Li Q, Yao M Y, Zhou B X. Atom Energy Sci Technol, 2010; 44: 1477
Zhou B X, Peng J C, Yao M Y, Li Q, Xia S, Du C X, Xu G. In: Limb?ck M, Barbéris P eds., Zirconium in the Nuclear Industry: Sixteenth International Symposium, ASTM STP 1529, Bridgeport: ASTM, 2011: 620
[12]
Sun G C, Zhou B X, Yao M Y, Xie S J, Li Q. Acta Metall Sin, 2012; 48: 1103
[12]
(孙国成, 周邦新, 姚美意, 谢世敬, 李 强. 金属学报, 2012; 48: 1103)
[13]
Yao M Y, Li S L, Zhang X, Peng J C, Zhou B X, Zhao X S, Shen J Y. Acta Metall Sin, 2011; 47: 865
Toffolon C, Brachet J C, Servant C, Legras L, Charquet D, Barberis P, Mardon J P. In: Moan G D, Rudling P eds., Zirconium in the Nuclear Industry: Thirteenth International Symposium, ASTM STP 1423, West Conshohochen: ASTM, 2002: 361
[15]
Takeda K, Anada H. In: Sabol G P, Moan G D eds., Zirconium in the Nuclear Industry: Twelfth International Symposium, ASTM STP 1354, West Conshohochen: ASTM, 2000: 592
[16]
Broy Y, Garzarolli F, Seibold A, van Swam L F. In: Sabol G P, Moan G D eds., Zirconium in the Nuclear Industry: Twelfth International Symposium, ASTM STP 1354, West Conshohochen: ASTM, 2000: 609
[17]
Zhou B X, Li Q, Yao M Y, Liu W Q, Chu Y L. J ASTM Int, 2008; 5: 360
[18]
Zhou B X, Li Q, Yao M Y, Liu W Q. Nucl Power Eng, 2005; 26: 364
[18]
(周邦新, 李 强, 姚美意, 刘文庆. 核动力工程, 2005; 26: 364)
[19]
Zhou B X, Li Q, Huang Q, Miao Z, Zhao W J, Li C. Nucl Power Eng, 2000; 21: 339
