| WANG Rui,HUO Tonglong,TIAN Zhenzhen,LIU Xin,SUN Changshuai,QIAN Baozhi.Corrosion Behavior of Inconel690 Alloy in High Temperature Caustic Alkaline Solution[J],54(10):105-115, 150 |
| Corrosion Behavior of Inconel690 Alloy in High Temperature Caustic Alkaline Solution |
| Received:July 14, 2024 Revised:December 26, 2024 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2025.10.008 |
| KeyWord:steam generator 690 alloy high temperature alkaline solution uniform corrosion corrosion rate |
| Author | Institution |
| WANG Rui |
College of Mechanical and Electronic Engineering, Shandong University of Science and Technology, Shandong Qingdao , China;HBIS Group Co., Ltd., Shijiazhuang , China |
| HUO Tonglong |
College of Mechanical and Electronic Engineering, Shandong University of Science and Technology, Shandong Qingdao , China |
| TIAN Zhenzhen |
Qingdao Tianhe Manufacturing Transformation and Upgrading Research Institute Co., Ltd., Shandong Qingdao , China |
| LIU Xin |
College of Mechanical and Electronic Engineering, Shandong University of Science and Technology, Shandong Qingdao , China |
| SUN Changshuai |
College of Mechanical and Electronic Engineering, Shandong University of Science and Technology, Shandong Qingdao , China |
| QIAN Baozhi |
College of Mechanical and Electronic Engineering, Shandong University of Science and Technology, Shandong Qingdao , China;Shanghai Nuclear Equipment Test Center, Shanghai , China |
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| Abstract: |
| The steam generator heat transfer tube is a heat exchange hub between the primary circuit and the secondary circuit of the pressurized water reactor (PWR). There is high temperature and high pressure alkaline solution in the service environment. In view of this, the corrosion behavior of Inconel 690 alloy in high temperature caustic alkaline solution was studied in this paper. The autoclave equipment with a water circulation system was used to simulate the real working conditions of PWR. The experimental schemes of secondary loop water environment (285 ℃), 320 ℃ off-condition water environment, sub-critical water environment (360 ℃) and different pH values (pH=7, pH=9.8, pH=10.6) were designed, and the uniform corrosion properties of the corresponding 690 alloy were tested. The morphology, composition, element content and corrosion mechanism of the oxide film were analyzed by SEM, EDS and XRD, and the corrosion rate under three working conditions was calculated. The uniform corrosion rate of alloy 690 at three temperatures were obtained. In the secondary loop water environment, the surface oxides of alloy 690 in pH=9.8 and pH=10.6 water environments were similar in shape, showing a uniform distribution of flocculent oxides, and discretely distributed in flocculent oxides. The flake-like oxide particles were about 0.3 μm in size, while the oxides in the pure water (pH=7) environment were pure flocculent. Combined with EDS results, the Cr content of flocculent oxides was higher. Under the 320 ℃ off-condition water environment, the outer oxides formed by 690 alloy were all flakes, and irregular granular oxides were formed. Compared with the outer oxide film, the Cr content of the inner oxide film was slightly higher, while the Fe content was slightly lower. In the sub-critical water environment (360 ℃), with the increase of temperature, the oxide size on the surface of 690 alloy was also gradually increasing. Compared with the 320 ℃ off-condition environment, the number of granular oxides under the sub-critical water environment was also more, but the morphology did not change much. In the secondary loop water environment, the uniform corrosion rates of pure water (pH=7), pH = 9.8 and pH =10.6 were 0.015, 0.013 and 0.004 mg/(dm2.h1/2), respectively. At 320 ℃, the uniform corrosion rates were 0.004, 0.008, 0.002 mg/(dm2.h1/2), respectively. In the sub-critical water environment, the uniform corrosion rates were 0.010, 0.002 and 0.011 mg/(dm2.h1/2), respectively. In conclusion, in the simulated secondary loop water environment, the surface of 690 alloy is uniformly distributed flocculent oxides, and flake oxides are dispersed in the flocculent oxides. With the increase of temperature, under the 320 ℃ off-condition environment, the flocculent oxide disappears, but the flake/leafy oxide increases and the size also increases. In the sub-critical water environment (360 ℃), the surface oxides are granular and not dense. A double-layer oxide film is formed on the surface of alloy 690 in the high temperature water environment. At the initial stage, the inner and outer oxide films are Cr2O3, Fe(OH)2 and Ni(OH)2, respectively. Due to the mechanism of solid-state oxidation and metal dissolution and deposition, the inner oxide film with Cr2O3 and Cr(OH)2 as the main and trace (Nix, Fe1−x)Cr2O4 as the main and the outer oxide film with Fe(OH)2, Ni(OH)2 and NiFe2O4 as the main and a small amount of NiO, FeO and Fe2O3 as the main are formed. When pH=7 and pH=10.6, the uniform corrosion rate is the lowest at 320 ℃. When pH=9.8, the uniform corrosion rate under the sub-critical water environment (360 ℃) is the lowest. |
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