Influence of Oxidation Temperature on the High-Temperature Oxide Film Forming Behavior of T22 Heat-Exchange Tubes

Abstract:

In this study, without changing the whole manufacturing process of T22 coiled tubes, high-temperature oxide films are formed through atmosphere adjustment by taking advantages of the cooling process after stress elimination heat treatment. The corrosion resistance of T22 heat-exchange tubes is improved, which are used in the steam generators (SG) of high-temperature gas cooled reactors (HTR). The surface microscopic morphology of the oxide films is observed using a scanning electron microscope, and the structure of these films is characterized using an X-ray diffractometer. The stability of the high-temperature oxide film forming process is investigated using TG-DTG, as well as the thermal expansion coefficient of the films. The results prove that: (1) The oxide film generated at 550 °C is uniform and dense; (2) The oxide films formed at various holding temperatures are mainly consisted by Fe₂O₃ and Fe₃O₄. When the holding temperature is 550 °C, the content of Fe₃O₄ is the highest as 70.1%; (3) The films are stable when placed in inert atmosphere (N2) below 900 °C, and there is not any change in the composition and structure of the films even after reacting with steam at 550 °C for 24 h; (4) The expansion coefficient of high-temperature oxide films is very close to that of the matrix of the heat exchange tube, and the difference between these two thermal expansion coefficients is 5.3×10^-9 mm/°C.

• Periodical: Advanced Materials Research (Volumes 1120-1121)
• Pages: 723-729
• DOI: https://doi.org/10.4028/www.scientific.net/AMR.1120-1121.723
• Online since: July 2015
• Authors: Bao Shan Gu*, Qiang Lu, Ji Yi Fu, Xiao Bao Yuan, Yan Wang, Pei Yan Yang
• Keywords: High-Temperature Gas Cooled Reactor, Oxide Film, Stability, T22, Temperature, Thermal Expansion Coefficient

References

[1] Fu Xiaoming, Wang Ji. Review on development of high-temperature gas-cooled reactor in China. Modern Electric Power, 2006, 23(5): 70-75.

[2] WANG Ying-su. The commercial application prospect of HTGR plant in China. CHINA NUCLEAR POWER, 2008, 1(3): 206-211.

[3] Li Jufeng. Discussion on thelocalization of nuclear power plantsteam generator of high-temperature gas-cooled reactor. Electric Power Technology, 2010, 19, 17-18: 106-109.

[4] Pan Feng, Yan Yunfeng, Xu Baoshun, Song Baoxing Research on Heat Treatment of T22 Steel High-pressure Boiler Pipe. STEEL PIPE, 2010, 39, 1: 60-66.

[5] Manna G, Castello P, Harskamp F, et al. Testing of welded 2. 25CrMo steel in hot high pressure hydrogen under creep conditions. Engineering fracture mechanics, 2007, 74: 956-968.

DOI: 10.1016/j.engfracmech.2006.08.021

[6] Moro L, Gonzalez G, Brizuela G, et al. Influence of chromium and vanadium in the mechanical resistance of steels. Materials chemistry and physics, 2008, 109: 212-216.

DOI: 10.1016/j.matchemphys.2007.11.030

[7] American Society of Mechanical Engineers NQA-1 Standard Part II Quality Assurance Requirements for Nuclear Facility Applications. ASME, Edition (2000).

[8] Design and Construction Rules for Mechanical Components of PWR Nuclear Islands[S], RCC-M Section V, F6000 Cleanliness, Edition (2000).

[9] Henry C, Elter C, Thermohydraulic verification during THTR steam generator commissioning. Palomero C F, Grebennik V. Tech of Steam Generators for Gas-Cooled Reactors. Vienna, AUT: Int. Atomic Energy Agency, 1988, 204-209.

[10] Hu Chuanshun, QinHua, MaXilong, Zhu Jian, Effect of dual thermal cycle on microstructure of 2. 25Cr1Mo steel. Journal of Petrochemical Universities, 2012, 25, 3: 64-66.

[11] LITiefan, High-temperature Oxidation and Hot Corrosion of Metals. Beijing, Chemical Industry Press, 2003: 52, 169-173.

[12] Hu Gengxiang, CaiXun, RongYonghua. Fundamentals of Material Science. Second Edition, Shanghai: Shanghai Jiao Tong University Press, 2006: 64.